dev: Distributed Ethernet link for distributed gem5 simulations

Distributed gem5 (abbreviated dist-gem5) is the result of the
convergence effort between multi-gem5 and pd-gem5 (from Univ. of
Wisconsin). It relies on the base multi-gem5 infrastructure for packet
forwarding, synchronisation and checkpointing but combines those with
the elaborated network switch model from pd-gem5.

--HG--
rename : src/dev/net/multi_etherlink.cc => src/dev/net/dist_etherlink.cc
rename : src/dev/net/multi_etherlink.hh => src/dev/net/dist_etherlink.hh
rename : src/dev/net/multi_iface.cc => src/dev/net/dist_iface.cc
rename : src/dev/net/multi_iface.hh => src/dev/net/dist_iface.hh
rename : src/dev/net/multi_packet.hh => src/dev/net/dist_packet.hh

19 files changed, 1879 insertions, 2226 deletions

diff --git a/src/dev/net/Ethernet.py b/src/dev/net/Ethernet.py
index 9859857a0..5f878ea10 100644
--- a/src/dev/net/Ethernet.py
+++ b/src/dev/net/Ethernet.py
@@ -58,19 +58,22 @@ class EtherLink(EtherObject):
     speed = Param.NetworkBandwidth('1Gbps', "link speed")
     dump = Param.EtherDump(NULL, "dump object")
 
-class MultiEtherLink(EtherObject):
-    type = 'MultiEtherLink'
-    cxx_header = "dev/net/multi_etherlink.hh"
+class DistEtherLink(EtherObject):
+    type = 'DistEtherLink'
+    cxx_header = "dev/net/dist_etherlink.hh"
     int0 = SlavePort("interface 0")
     delay = Param.Latency('0us', "packet transmit delay")
     delay_var = Param.Latency('0ns', "packet transmit delay variability")
     speed = Param.NetworkBandwidth('1Gbps', "link speed")
     dump = Param.EtherDump(NULL, "dump object")
-    multi_rank  =  Param.UInt32('0', "Rank of the this gem5 process (multi run)")
-    sync_start  = Param.Latency('5200000000000t', "first multi sync barrier")
-    sync_repeat = Param.Latency('10us', "multi sync barrier repeat")
+    dist_rank = Param.UInt32('0', "Rank of this gem5 process (dist run)")
+    dist_size = Param.UInt32('1', "Number of gem5 processes (dist run)")
+    sync_start = Param.Latency('5200000000000t', "first dist sync barrier")
+    sync_repeat = Param.Latency('10us', "dist sync barrier repeat")
     server_name = Param.String('localhost', "Message server name")
     server_port = Param.UInt32('2200', "Message server port")
+    is_switch = Param.Bool(False, "true if this a link in etherswitch")
+    num_nodes = Param.UInt32('2', "Number of simulate nodes")
 
 class EtherBus(EtherObject):
     type = 'EtherBus'
diff --git a/src/dev/net/SConscript b/src/dev/net/SConscript
index f529a1b2a..9ad8eec92 100644
--- a/src/dev/net/SConscript
+++ b/src/dev/net/SConscript
@@ -70,14 +70,14 @@ DebugFlag('EthernetIntr')
 DebugFlag('EthernetPIO')
 DebugFlag('EthernetSM')
 
-# Multi gem5
-Source('multi_packet.cc')
-Source('multi_iface.cc')
-Source('multi_etherlink.cc')
+# Dist gem5
+Source('dist_iface.cc')
+Source('dist_etherlink.cc')
 Source('tcp_iface.cc')
 
-DebugFlag('MultiEthernet')
-DebugFlag('MultiEthernetPkt')
+DebugFlag('DistEthernet')
+DebugFlag('DistEthernetPkt')
+DebugFlag('DistEthernetCmd')
 
 # Ethernet controllers
 Source('i8254xGBe.cc')
diff --git a/src/dev/net/multi_etherlink.cc b/src/dev/net/dist_etherlink.cc
index cf4300ddf..a793739f8 100644
--- a/src/dev/net/multi_etherlink.cc
+++ b/src/dev/net/dist_etherlink.cc
@@ -38,10 +38,10 @@
  */
 
 /* @file
- * Device module for a full duplex ethernet link for multi gem5 simulations.
+ * Device module for a full duplex ethernet link for dist gem5 simulations.
  */
 
-#include "dev/net/multi_etherlink.hh"
+#include "dev/net/dist_etherlink.hh"
 
 #include <arpa/inet.h>
 #include <sys/socket.h>
@@ -54,15 +54,15 @@
 
 #include "base/random.hh"
 #include "base/trace.hh"
+#include "debug/DistEthernet.hh"
+#include "debug/DistEthernetPkt.hh"
 #include "debug/EthernetData.hh"
-#include "debug/MultiEthernet.hh"
-#include "debug/MultiEthernetPkt.hh"
+#include "dev/net/dist_iface.hh"
 #include "dev/net/etherdump.hh"
 #include "dev/net/etherint.hh"
 #include "dev/net/etherlink.hh"
 #include "dev/net/etherobject.hh"
 #include "dev/net/etherpkt.hh"
-#include "dev/net/multi_iface.hh"
 #include "dev/net/tcp_iface.hh"
 #include "params/EtherLink.hh"
 #include "sim/core.hh"
@@ -71,33 +71,45 @@
 
 using namespace std;
 
-MultiEtherLink::MultiEtherLink(const Params *p)
-    : EtherObject(p)
+DistEtherLink::DistEtherLink(const Params *p)
+    : EtherObject(p), linkDelay(p->delay)
 {
-    DPRINTF(MultiEthernet,"MultiEtherLink::MultiEtherLink() "
-            "link delay:%llu\n", p->delay);
+    DPRINTF(DistEthernet,"DistEtherLink::DistEtherLink() "
+            "link delay:%llu ticksPerByte:%f\n", p->delay, p->speed);
 
     txLink = new TxLink(name() + ".link0", this, p->speed, p->delay_var,
                         p->dump);
     rxLink = new RxLink(name() + ".link1", this, p->delay, p->dump);
 
-    // create the multi (TCP) interface to talk to the peer gem5 processes.
-    multiIface = new TCPIface(p->server_name, p->server_port, p->multi_rank,
-                              p->sync_start, p->sync_repeat, this);
+    Tick sync_repeat;
+    if (p->sync_repeat != 0) {
+        if (p->sync_repeat != p->delay)
+            warn("DistEtherLink(): sync_repeat is %lu and linkdelay is %lu",
+                 p->sync_repeat, p->delay);
+        sync_repeat = p->sync_repeat;
+    } else {
+        sync_repeat = p->delay;
+    }
+
+    // create the dist (TCP) interface to talk to the peer gem5 processes.
+    distIface = new TCPIface(p->server_name, p->server_port,
+                             p->dist_rank, p->dist_size,
+                             p->sync_start, sync_repeat, this, p->is_switch,
+                             p->num_nodes);
 
-    localIface = new LocalIface(name() + ".int0", txLink, rxLink, multiIface);
+    localIface = new LocalIface(name() + ".int0", txLink, rxLink, distIface);
 }
 
-MultiEtherLink::~MultiEtherLink()
+DistEtherLink::~DistEtherLink()
 {
     delete txLink;
     delete rxLink;
     delete localIface;
-    delete multiIface;
+    delete distIface;
 }
 
 EtherInt*
-MultiEtherLink::getEthPort(const std::string &if_name, int idx)
+DistEtherLink::getEthPort(const std::string &if_name, int idx)
 {
     if (if_name != "int0") {
         return nullptr;
@@ -107,66 +119,55 @@ MultiEtherLink::getEthPort(const std::string &if_name, int idx)
     return localIface;
 }
 
-void MultiEtherLink::memWriteback()
-{
-    DPRINTF(MultiEthernet,"MultiEtherLink::memWriteback() called\n");
-    multiIface->drainDone();
-}
-
 void
-MultiEtherLink::serialize(CheckpointOut &cp) const
+DistEtherLink::serialize(CheckpointOut &cp) const
 {
-    multiIface->serialize("multiIface", cp);
-    txLink->serialize("txLink", cp);
-    rxLink->serialize("rxLink", cp);
+    distIface->serializeSection(cp, "distIface");
+    txLink->serializeSection(cp, "txLink");
+    rxLink->serializeSection(cp, "rxLink");
 }
 
 void
-MultiEtherLink::unserialize(CheckpointIn &cp)
+DistEtherLink::unserialize(CheckpointIn &cp)
 {
-    multiIface->unserialize("multiIface", cp);
-    txLink->unserialize("txLink", cp);
-    rxLink->unserialize("rxLink", cp);
+    distIface->unserializeSection(cp, "distIface");
+    txLink->unserializeSection(cp, "txLink");
+    rxLink->unserializeSection(cp, "rxLink");
 }
 
 void
-MultiEtherLink::init()
+DistEtherLink::init()
 {
-    DPRINTF(MultiEthernet,"MultiEtherLink::init() called\n");
-    multiIface->initRandom();
+    DPRINTF(DistEthernet,"DistEtherLink::init() called\n");
+    distIface->init(rxLink->doneEvent(), linkDelay);
 }
 
 void
-MultiEtherLink::startup()
+DistEtherLink::startup()
 {
-    DPRINTF(MultiEthernet,"MultiEtherLink::startup() called\n");
-    multiIface->startPeriodicSync();
+    DPRINTF(DistEthernet,"DistEtherLink::startup() called\n");
+    distIface->startup();
 }
 
 void
-MultiEtherLink::RxLink::setMultiInt(MultiIface *m)
+DistEtherLink::RxLink::setDistInt(DistIface *m)
 {
-    assert(!multiIface);
-    multiIface = m;
-    // Spawn a new receiver thread that will process messages
-    // coming in from peer gem5 processes.
-    // The receive thread will also schedule a (receive) doneEvent
-    // for each incoming data packet.
-    multiIface->spawnRecvThread(&doneEvent, linkDelay);
+    assert(!distIface);
+    distIface = m;
 }
 
 void
-MultiEtherLink::RxLink::rxDone()
+DistEtherLink::RxLink::rxDone()
 {
     assert(!busy());
 
     // retrieve the packet that triggered the receive done event
-    packet = multiIface->packetIn();
+    packet = distIface->packetIn();
 
     if (dump)
         dump->dump(packet);
 
-    DPRINTF(MultiEthernetPkt, "MultiEtherLink::MultiLink::rxDone() "
+    DPRINTF(DistEthernetPkt, "DistEtherLink::DistLink::rxDone() "
             "packet received: len=%d\n", packet->length);
     DDUMP(EthernetData, packet->data, packet->length);
 
@@ -176,7 +177,7 @@ MultiEtherLink::RxLink::rxDone()
 }
 
 void
-MultiEtherLink::TxLink::txDone()
+DistEtherLink::TxLink::txDone()
 {
     if (dump)
         dump->dump(packet);
@@ -188,10 +189,10 @@ MultiEtherLink::TxLink::txDone()
 }
 
 bool
-MultiEtherLink::TxLink::transmit(EthPacketPtr pkt)
+DistEtherLink::TxLink::transmit(EthPacketPtr pkt)
 {
     if (busy()) {
-        DPRINTF(MultiEthernet, "packet not sent, link busy\n");
+        DPRINTF(DistEthernet, "packet not sent, link busy\n");
         return false;
     }
 
@@ -201,8 +202,8 @@ MultiEtherLink::TxLink::transmit(EthPacketPtr pkt)
         delay += random_mt.random<Tick>(0, delayVar);
 
     // send the packet to the peers
-    assert(multiIface);
-    multiIface->packetOut(pkt, delay);
+    assert(distIface);
+    distIface->packetOut(pkt, delay);
 
     // schedule the send done event
     parent->schedule(doneEvent, curTick() + delay);
@@ -211,56 +212,56 @@ MultiEtherLink::TxLink::transmit(EthPacketPtr pkt)
 }
 
 void
-MultiEtherLink::Link::serialize(const string &base, CheckpointOut &cp) const
+DistEtherLink::Link::serialize(CheckpointOut &cp) const
 {
     bool packet_exists = (packet != nullptr);
-    paramOut(cp, base + ".packet_exists", packet_exists);
+    SERIALIZE_SCALAR(packet_exists);
     if (packet_exists)
-        packet->serialize(base + ".packet", cp);
+        packet->serialize("packet", cp);
 
     bool event_scheduled = event->scheduled();
-    paramOut(cp, base + ".event_scheduled", event_scheduled);
+    SERIALIZE_SCALAR(event_scheduled);
     if (event_scheduled) {
         Tick event_time = event->when();
-        paramOut(cp, base + ".event_time", event_time);
+        SERIALIZE_SCALAR(event_time);
     }
 }
 
 void
-MultiEtherLink::Link::unserialize(const string &base, CheckpointIn &cp)
+DistEtherLink::Link::unserialize(CheckpointIn &cp)
 {
     bool packet_exists;
-    paramIn(cp, base + ".packet_exists", packet_exists);
+    UNSERIALIZE_SCALAR(packet_exists);
     if (packet_exists) {
         packet = make_shared<EthPacketData>(16384);
-        packet->unserialize(base + ".packet", cp);
+        packet->unserialize("packet", cp);
     }
 
     bool event_scheduled;
-    paramIn(cp, base + ".event_scheduled", event_scheduled);
+    UNSERIALIZE_SCALAR(event_scheduled);
     if (event_scheduled) {
         Tick event_time;
-        paramIn(cp, base + ".event_time", event_time);
+        UNSERIALIZE_SCALAR(event_time);
         parent->schedule(*event, event_time);
     }
 }
 
-MultiEtherLink::LocalIface::LocalIface(const std::string &name,
+DistEtherLink::LocalIface::LocalIface(const std::string &name,
                                        TxLink *tx,
                                        RxLink *rx,
-                                       MultiIface *m) :
+                                       DistIface *m) :
     EtherInt(name), txLink(tx)
 {
     tx->setLocalInt(this);
     rx->setLocalInt(this);
-    tx->setMultiInt(m);
-    rx->setMultiInt(m);
+    tx->setDistInt(m);
+    rx->setDistInt(m);
 }
 
-MultiEtherLink *
-MultiEtherLinkParams::create()
+DistEtherLink *
+DistEtherLinkParams::create()
 {
-    return new MultiEtherLink(this);
+    return new DistEtherLink(this);
 }
 
 
diff --git a/src/dev/net/multi_etherlink.hh b/src/dev/net/dist_etherlink.hh
index 0a3e39bd7..e8218941a 100644
--- a/src/dev/net/multi_etherlink.hh
+++ b/src/dev/net/dist_etherlink.hh
@@ -38,30 +38,30 @@
  */
 
 /* @file
- * Device module for a full duplex ethernet link for multi gem5 simulations.
+ * Device module for a full duplex ethernet link for dist gem5 simulations.
  *
- * See comments in dev/multi_iface.hh for a generic description of multi
+ * See comments in dev/net/dist_iface.hh for a generic description of dist
  * gem5 simulations.
  *
  * This class is meant to be a drop in replacement for the EtherLink class for
- * multi gem5 runs.
+ * dist gem5 runs.
  *
  */
-#ifndef __DEV_NET_MULTIETHERLINK_HH__
-#define __DEV_NET_MULTIETHERLINK_HH__
+#ifndef __DEV_DIST_ETHERLINK_HH__
+#define __DEV_DIST_ETHERLINK_HH__
 
 #include <iostream>
 
 #include "dev/net/etherlink.hh"
-#include "params/MultiEtherLink.hh"
+#include "params/DistEtherLink.hh"
 
-class MultiIface;
+class DistIface;
 class EthPacketData;
 
 /**
  * Model for a fixed bandwidth full duplex ethernet link.
  */
-class MultiEtherLink : public EtherObject
+class DistEtherLink : public EtherObject
 {
   protected:
     class LocalIface;
@@ -72,22 +72,22 @@ class MultiEtherLink : public EtherObject
      * The link will encapsulate and transfer Ethernet packets to/from
      * the message server.
      */
-    class Link
+    class Link : public Serializable
     {
       protected:
         std::string objName;
-        MultiEtherLink *parent;
+        DistEtherLink *parent;
         LocalIface *localIface;
         EtherDump *dump;
-        MultiIface *multiIface;
+        DistIface *distIface;
         Event *event;
         EthPacketPtr packet;
 
       public:
-        Link(const std::string &name, MultiEtherLink *p,
+        Link(const std::string &name, DistEtherLink *p,
              EtherDump *d, Event *e) :
             objName(name), parent(p), localIface(nullptr), dump(d),
-            multiIface(nullptr), event(e) {}
+            distIface(nullptr), event(e) {}
 
         ~Link() {}
 
@@ -95,8 +95,8 @@ class MultiEtherLink : public EtherObject
         bool busy() const { return (bool)packet; }
         void setLocalInt(LocalIface *i) { assert(!localIface); localIface=i; }
 
-        void serialize(const std::string &base, CheckpointOut &cp) const;
-        void unserialize(const std::string &base, CheckpointIn &cp);
+        void serialize(CheckpointOut &cp) const override;
+        void unserialize(CheckpointIn &cp) override;
     };
 
     /**
@@ -123,17 +123,17 @@ class MultiEtherLink : public EtherObject
         DoneEvent doneEvent;
 
       public:
-        TxLink(const std::string &name, MultiEtherLink *p,
+        TxLink(const std::string &name, DistEtherLink *p,
                double invBW, Tick delay_var, EtherDump *d) :
             Link(name, p, d, &doneEvent), ticksPerByte(invBW),
             delayVar(delay_var), doneEvent(this) {}
         ~TxLink() {}
 
         /**
-         * Register the multi interface to be used to talk to the
+         * Register the dist interface to be used to talk to the
          * peer gem5 processes.
          */
-        void setMultiInt(MultiIface *m) { assert(!multiIface); multiIface=m; }
+        void setDistInt(DistIface *m) { assert(!distIface); distIface=m; }
 
         /**
          * Initiate sending of a packet via this link.
@@ -158,23 +158,27 @@ class MultiEtherLink : public EtherObject
         /**
          * Receive done callback method. Called from doneEvent.
          */
-        void rxDone() ;
+        void rxDone();
         typedef EventWrapper<RxLink, &RxLink::rxDone> DoneEvent;
         friend void DoneEvent::process();
-        DoneEvent doneEvent;
+        DoneEvent _doneEvent;
 
       public:
 
-        RxLink(const std::string &name, MultiEtherLink *p,
+        RxLink(const std::string &name, DistEtherLink *p,
                Tick delay, EtherDump *d) :
-            Link(name, p, d, &doneEvent),
-            linkDelay(delay), doneEvent(this) {}
+            Link(name, p, d, &_doneEvent),
+            linkDelay(delay), _doneEvent(this) {}
         ~RxLink() {}
 
         /**
-         * Register our multi interface to talk to the peer gem5 processes.
+         * Register our dist interface to talk to the peer gem5 processes.
+         */
+        void setDistInt(DistIface *m);
+        /**
+         * Done events will be scheduled by DistIface (so we need the accessor)
          */
-        void setMultiInt(MultiIface *m);
+        const DoneEvent *doneEvent() const { return &_doneEvent; }
     };
 
     /**
@@ -187,7 +191,7 @@ class MultiEtherLink : public EtherObject
 
       public:
         LocalIface(const std::string &name, TxLink *tx, RxLink *rx,
-                   MultiIface *m);
+                   DistIface *m);
 
         bool recvPacket(EthPacketPtr pkt) { return txLink->transmit(pkt); }
         void sendDone() { peer->sendDone(); }
@@ -199,7 +203,7 @@ class MultiEtherLink : public EtherObject
     /**
      * Interface to talk to the peer gem5 processes.
      */
-    MultiIface *multiIface;
+    DistIface *distIface;
     /**
      * Send link
      */
@@ -210,10 +214,12 @@ class MultiEtherLink : public EtherObject
     RxLink *rxLink;
     LocalIface *localIface;
 
+    Tick linkDelay;
+
   public:
-    typedef MultiEtherLinkParams Params;
-    MultiEtherLink(const Params *p);
-    ~MultiEtherLink();
+    typedef DistEtherLinkParams Params;
+    DistEtherLink(const Params *p);
+    ~DistEtherLink();
 
     const Params *
     params() const
@@ -224,12 +230,11 @@ class MultiEtherLink : public EtherObject
     virtual EtherInt *getEthPort(const std::string &if_name,
                                  int idx) override;
 
-    void memWriteback() override;
-    void init() override;
-    void startup() override;
+    virtual void init() override;
+    virtual void startup() override;
 
     void serialize(CheckpointOut &cp) const override;
     void unserialize(CheckpointIn &cp) override;
 };
 
-#endif // __DEV_NET_MULTIETHERLINK_HH__
+#endif // __DEV_DIST_ETHERLINK_HH__
diff --git a/src/dev/net/dist_iface.cc b/src/dev/net/dist_iface.cc
new file mode 100644
index 000000000..45ce651a9
--- /dev/null
+++ b/src/dev/net/dist_iface.cc
@@ -0,0 +1,808 @@
+/*
+ * Copyright (c) 2015 ARM Limited
+ * All rights reserved
+ *
+ * The license below extends only to copyright in the software and shall
+ * not be construed as granting a license to any other intellectual
+ * property including but not limited to intellectual property relating
+ * to a hardware implementation of the functionality of the software
+ * licensed hereunder.  You may use the software subject to the license
+ * terms below provided that you ensure that this notice is replicated
+ * unmodified and in its entirety in all distributions of the software,
+ * modified or unmodified, in source code or in binary form.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met: redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer;
+ * redistributions in binary form must reproduce the above copyright
+ * notice, this list of conditions and the following disclaimer in the
+ * documentation and/or other materials provided with the distribution;
+ * neither the name of the copyright holders nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ * Authors: Gabor Dozsa
+ */
+
+/* @file
+ * The interface class for dist-gem5 simulations.
+ */
+
+#include "dev/net/dist_iface.hh"
+
+#include <queue>
+#include <thread>
+
+#include "base/random.hh"
+#include "base/trace.hh"
+#include "debug/DistEthernet.hh"
+#include "debug/DistEthernetPkt.hh"
+#include "dev/net/etherpkt.hh"
+#include "sim/sim_exit.hh"
+#include "sim/sim_object.hh"
+
+using namespace std;
+DistIface::Sync *DistIface::sync = nullptr;
+DistIface::SyncEvent *DistIface::syncEvent = nullptr;
+unsigned DistIface::distIfaceNum = 0;
+unsigned DistIface::recvThreadsNum = 0;
+DistIface *DistIface::master = nullptr;
+
+void
+DistIface::Sync::init(Tick start_tick, Tick repeat_tick)
+{
+    if (start_tick < firstAt) {
+        firstAt = start_tick;
+        inform("Next dist synchronisation tick is changed to %lu.\n", nextAt);
+    }
+
+    if (repeat_tick == 0)
+        panic("Dist synchronisation interval must be greater than zero");
+
+    if (repeat_tick < nextRepeat) {
+        nextRepeat = repeat_tick;
+        inform("Dist synchronisation interval is changed to %lu.\n",
+               nextRepeat);
+    }
+}
+
+DistIface::SyncSwitch::SyncSwitch(int num_nodes)
+{
+    numNodes = num_nodes;
+    waitNum = num_nodes;
+    numExitReq = 0;
+    numCkptReq = 0;
+    doExit = false;
+    doCkpt = false;
+    firstAt = std::numeric_limits<Tick>::max();
+    nextAt = 0;
+    nextRepeat = std::numeric_limits<Tick>::max();
+}
+
+DistIface::SyncNode::SyncNode()
+{
+    waitNum = 0;
+    needExit = ReqType::none;
+    needCkpt = ReqType::none;
+    doExit = false;
+    doCkpt = false;
+    firstAt = std::numeric_limits<Tick>::max();
+    nextAt = 0;
+    nextRepeat = std::numeric_limits<Tick>::max();
+}
+
+void
+DistIface::SyncNode::run(bool same_tick)
+{
+    std::unique_lock<std::mutex> sync_lock(lock);
+    Header header;
+
+    assert(waitNum == 0);
+    waitNum = DistIface::recvThreadsNum;
+    // initiate the global synchronisation
+    header.msgType = MsgType::cmdSyncReq;
+    header.sendTick = curTick();
+    header.syncRepeat = nextRepeat;
+    header.needCkpt = needCkpt;
+    if (needCkpt != ReqType::none)
+        needCkpt = ReqType::pending;
+    header.needExit = needExit;
+    if (needExit != ReqType::none)
+        needExit = ReqType::pending;
+    DistIface::master->sendCmd(header);
+    // now wait until all receiver threads complete the synchronisation
+    auto lf = [this]{ return waitNum == 0; };
+    cv.wait(sync_lock, lf);
+    // global synchronisation is done
+    assert(!same_tick || (nextAt == curTick()));
+}
+
+
+void
+DistIface::SyncSwitch::run(bool same_tick)
+{
+    std::unique_lock<std::mutex> sync_lock(lock);
+    Header header;
+    // Wait for the sync requests from the nodes
+    if (waitNum > 0) {
+        auto lf = [this]{ return waitNum == 0; };
+        cv.wait(sync_lock, lf);
+    }
+    assert(waitNum == 0);
+    assert(!same_tick || (nextAt == curTick()));
+    waitNum = numNodes;
+    // Complete the global synchronisation
+    header.msgType = MsgType::cmdSyncAck;
+    header.sendTick = nextAt;
+    header.syncRepeat = nextRepeat;
+    if (doCkpt || numCkptReq == numNodes) {
+        doCkpt = true;
+        header.needCkpt = ReqType::immediate;
+        numCkptReq = 0;
+    } else {
+        header.needCkpt = ReqType::none;
+    }
+    if (doExit || numExitReq == numNodes) {
+        doExit = true;
+        header.needExit = ReqType::immediate;
+    } else {
+        header.needExit = ReqType::none;
+    }
+    DistIface::master->sendCmd(header);
+}
+
+void
+DistIface::SyncSwitch::progress(Tick send_tick,
+                                 Tick sync_repeat,
+                                 ReqType need_ckpt,
+                                 ReqType need_exit)
+{
+    std::unique_lock<std::mutex> sync_lock(lock);
+    assert(waitNum > 0);
+
+    if (send_tick > nextAt)
+        nextAt = send_tick;
+    if (nextRepeat > sync_repeat)
+        nextRepeat = sync_repeat;
+
+    if (need_ckpt == ReqType::collective)
+        numCkptReq++;
+    else if (need_ckpt == ReqType::immediate)
+        doCkpt = true;
+    if (need_exit == ReqType::collective)
+        numExitReq++;
+    else if (need_exit == ReqType::immediate)
+        doExit = true;
+
+    waitNum--;
+    // Notify the simulation thread if the on-going sync is complete
+    if (waitNum == 0) {
+        sync_lock.unlock();
+        cv.notify_one();
+    }
+}
+
+void
+DistIface::SyncNode::progress(Tick max_send_tick,
+                               Tick next_repeat,
+                               ReqType do_ckpt,
+                               ReqType do_exit)
+{
+    std::unique_lock<std::mutex> sync_lock(lock);
+    assert(waitNum > 0);
+
+    nextAt = max_send_tick;
+    nextRepeat = next_repeat;
+    doCkpt = (do_ckpt != ReqType::none);
+    doExit = (do_exit != ReqType::none);
+
+    waitNum--;
+    // Notify the simulation thread if the on-going sync is complete
+    if (waitNum == 0) {
+        sync_lock.unlock();
+        cv.notify_one();
+    }
+}
+
+void
+DistIface::SyncNode::requestCkpt(ReqType req)
+{
+   std::lock_guard<std::mutex> sync_lock(lock);
+   assert(req != ReqType::none);
+   if (needCkpt != ReqType::none)
+       warn("Ckpt requested multiple times (req:%d)\n", static_cast<int>(req));
+   if (needCkpt == ReqType::none || req == ReqType::immediate)
+       needCkpt = req;
+}
+
+void
+DistIface::SyncNode::requestExit(ReqType req)
+{
+   std::lock_guard<std::mutex> sync_lock(lock);
+   assert(req != ReqType::none);
+   if (needExit != ReqType::none)
+       warn("Exit requested multiple times (req:%d)\n", static_cast<int>(req));
+   if (needExit == ReqType::none || req == ReqType::immediate)
+       needExit = req;
+}
+
+void
+DistIface::Sync::drainComplete()
+{
+    if (doCkpt) {
+        // The first DistIface object called this right before writing the
+        // checkpoint. We need to drain the underlying physical network here.
+        // Note that other gem5 peers may enter this barrier at different
+        // ticks due to draining.
+        run(false);
+        // Only the "first" DistIface object has to perform the sync
+        doCkpt = false;
+    }
+}
+
+void
+DistIface::SyncNode::serialize(CheckpointOut &cp) const
+{
+    int need_exit = static_cast<int>(needExit);
+    SERIALIZE_SCALAR(need_exit);
+}
+
+void
+DistIface::SyncNode::unserialize(CheckpointIn &cp)
+{
+    int need_exit;
+    UNSERIALIZE_SCALAR(need_exit);
+    needExit = static_cast<ReqType>(need_exit);
+}
+
+void
+DistIface::SyncSwitch::serialize(CheckpointOut &cp) const
+{
+    SERIALIZE_SCALAR(numExitReq);
+}
+
+void
+DistIface::SyncSwitch::unserialize(CheckpointIn &cp)
+{
+    UNSERIALIZE_SCALAR(numExitReq);
+}
+
+void
+DistIface::SyncEvent::start()
+{
+    // Note that this may be called either from startup() or drainResume()
+
+    // At this point, all DistIface objects has already called Sync::init() so
+    // we have a local minimum of the start tick and repeat for the periodic
+    // sync.
+    Tick firstAt  = DistIface::sync->firstAt;
+    repeat = DistIface::sync->nextRepeat;
+    // Do a global barrier to agree on a common repeat value (the smallest
+    // one from all participating nodes
+    DistIface::sync->run(curTick() == 0);
+
+    assert(!DistIface::sync->doCkpt);
+    assert(!DistIface::sync->doExit);
+    assert(DistIface::sync->nextAt >= curTick());
+    assert(DistIface::sync->nextRepeat <= repeat);
+
+    // if this is called at tick 0 then we use the config start param otherwise
+    // the maximum of the current tick of all participating nodes
+    if (curTick() == 0) {
+        assert(!scheduled());
+        assert(DistIface::sync->nextAt == 0);
+        schedule(firstAt);
+    } else {
+        if (scheduled())
+            reschedule(DistIface::sync->nextAt);
+        else
+            schedule(DistIface::sync->nextAt);
+    }
+    inform("Dist sync scheduled at %lu and repeats %lu\n",  when(),
+           DistIface::sync->nextRepeat);
+}
+
+void
+DistIface::SyncEvent::process()
+{
+    // We may not start a global periodic sync while draining before taking a
+    // checkpoint.  This is due to the possibility that peer gem5 processes
+    // may not hit the same periodic sync before they complete draining and
+    // that would make this periodic sync clash with sync called from
+    // DistIface::serialize() by other gem5 processes.
+    // We would need a 'distributed drain' solution to eliminate this
+    // restriction.
+    // Note that if draining was not triggered by checkpointing then we are
+    // fine since no extra global sync will happen (i.e. all peer gem5 will
+    // hit this periodic sync eventually).
+    panic_if(_draining && DistIface::sync->doCkpt,
+             "Distributed sync is hit while draining");
+    /*
+     * Note that this is a global event so this process method will be called
+     * by only exactly one thread.
+     */
+    /*
+     * We hold the eventq lock at this point but the receiver thread may
+     * need the lock to schedule new recv events while waiting for the
+     * dist sync to complete.
+     * Note that the other simulation threads also release their eventq
+     * locks while waiting for us due to the global event semantics.
+     */
+    {
+        EventQueue::ScopedRelease sr(curEventQueue());
+        // we do a global sync here that is supposed to happen at the same
+        // tick in all gem5 peers
+        DistIface::sync->run(true);
+        // global sync completed
+    }
+    if (DistIface::sync->doCkpt)
+        exitSimLoop("checkpoint");
+    if (DistIface::sync->doExit)
+        exitSimLoop("exit request from gem5 peers");
+
+    // schedule the next periodic sync
+    repeat = DistIface::sync->nextRepeat;
+    schedule(curTick() + repeat);
+}
+
+void
+DistIface::RecvScheduler::init(Event *recv_done, Tick link_delay)
+{
+    // This is called from the receiver thread when it starts running. The new
+    // receiver thread shares the event queue with the simulation thread
+    // (associated with the simulated Ethernet link).
+    curEventQueue(eventManager->eventQueue());
+
+    recvDone = recv_done;
+    linkDelay = link_delay;
+}
+
+Tick
+DistIface::RecvScheduler::calcReceiveTick(Tick send_tick,
+                                          Tick send_delay,
+                                          Tick prev_recv_tick)
+{
+    Tick recv_tick = send_tick + send_delay + linkDelay;
+    // sanity check (we need atleast a send delay long window)
+    assert(recv_tick >= prev_recv_tick + send_delay);
+    panic_if(prev_recv_tick + send_delay > recv_tick,
+             "Receive window is smaller than send delay");
+    panic_if(recv_tick <= curTick(),
+             "Simulators out of sync - missed packet receive by %llu ticks"
+             "(rev_recv_tick: %lu send_tick: %lu send_delay: %lu "
+             "linkDelay: %lu )",
+             curTick() - recv_tick, prev_recv_tick, send_tick, send_delay,
+             linkDelay);
+
+    return recv_tick;
+}
+
+void
+DistIface::RecvScheduler::resumeRecvTicks()
+{
+    // Schedule pending packets asap in case link speed/delay changed when
+    // restoring from the checkpoint.
+    // This may be done during unserialize except that curTick() is unknown
+    // so we call this during drainResume().
+    // If we are not restoring from a checkppint then link latency could not
+    // change so we just return.
+    if (!ckptRestore)
+        return;
+
+    std::vector<Desc> v;
+    while (!descQueue.empty()) {
+        Desc d = descQueue.front();
+        descQueue.pop();
+        d.sendTick = curTick();
+        d.sendDelay = d.packet->size(); // assume 1 tick/byte max link speed
+        v.push_back(d);
+    }
+
+    for (auto &d : v)
+        descQueue.push(d);
+
+    if (recvDone->scheduled()) {
+        assert(!descQueue.empty());
+        eventManager->reschedule(recvDone, curTick());
+    } else {
+        assert(descQueue.empty() && v.empty());
+    }
+    ckptRestore = false;
+}
+
+void
+DistIface::RecvScheduler::pushPacket(EthPacketPtr new_packet,
+                                     Tick send_tick,
+                                     Tick send_delay)
+{
+    // Note : this is called from the receiver thread
+    curEventQueue()->lock();
+    Tick recv_tick = calcReceiveTick(send_tick, send_delay, prevRecvTick);
+
+    DPRINTF(DistEthernetPkt, "DistIface::recvScheduler::pushPacket "
+            "send_tick:%llu send_delay:%llu link_delay:%llu recv_tick:%llu\n",
+            send_tick, send_delay, linkDelay, recv_tick);
+    // Every packet must be sent and arrive in the same quantum
+    assert(send_tick > master->syncEvent->when() -
+           master->syncEvent->repeat);
+    // No packet may be scheduled for receive in the arrival quantum
+    assert(send_tick + send_delay + linkDelay > master->syncEvent->when());
+
+    // Now we are about to schedule a recvDone event for the new data packet.
+    // We use the same recvDone object for all incoming data packets. Packet
+    // descriptors are saved in the ordered queue. The currently scheduled
+    // packet is always on the top of the queue.
+    // NOTE:  we use the event queue lock to protect the receive desc queue,
+    // too, which is accessed both by the receiver thread and the simulation
+    // thread.
+    descQueue.emplace(new_packet, send_tick, send_delay);
+    if (descQueue.size() == 1) {
+        assert(!recvDone->scheduled());
+        eventManager->schedule(recvDone, recv_tick);
+    } else {
+        assert(recvDone->scheduled());
+        panic_if(descQueue.front().sendTick + descQueue.front().sendDelay > recv_tick,
+                 "Out of order packet received (recv_tick: %lu top(): %lu\n",
+                 recv_tick, descQueue.front().sendTick + descQueue.front().sendDelay);
+    }
+    curEventQueue()->unlock();
+}
+
+EthPacketPtr
+DistIface::RecvScheduler::popPacket()
+{
+    // Note : this is called from the simulation thread when a receive done
+    // event is being processed for the link. We assume that the thread holds
+    // the event queue queue lock when this is called!
+    EthPacketPtr next_packet = descQueue.front().packet;
+    descQueue.pop();
+
+    if (descQueue.size() > 0) {
+        Tick recv_tick = calcReceiveTick(descQueue.front().sendTick,
+                                         descQueue.front().sendDelay,
+                                         curTick());
+        eventManager->schedule(recvDone, recv_tick);
+    }
+    prevRecvTick = curTick();
+    return next_packet;
+}
+
+void
+DistIface::RecvScheduler::Desc::serialize(CheckpointOut &cp) const
+{
+        SERIALIZE_SCALAR(sendTick);
+        SERIALIZE_SCALAR(sendDelay);
+        packet->serialize("rxPacket", cp);
+}
+
+void
+DistIface::RecvScheduler::Desc::unserialize(CheckpointIn &cp)
+{
+        UNSERIALIZE_SCALAR(sendTick);
+        UNSERIALIZE_SCALAR(sendDelay);
+        packet = std::make_shared<EthPacketData>(16384);
+        packet->unserialize("rxPacket", cp);
+}
+
+void
+DistIface::RecvScheduler::serialize(CheckpointOut &cp) const
+{
+    SERIALIZE_SCALAR(prevRecvTick);
+    // serialize the receive desc queue
+    std::queue<Desc> tmp_queue(descQueue);
+    unsigned n_desc_queue = descQueue.size();
+    assert(tmp_queue.size() == descQueue.size());
+    SERIALIZE_SCALAR(n_desc_queue);
+    for (int i = 0; i < n_desc_queue; i++) {
+        tmp_queue.front().serializeSection(cp, csprintf("rxDesc_%d", i));
+        tmp_queue.pop();
+    }
+    assert(tmp_queue.empty());
+}
+
+void
+DistIface::RecvScheduler::unserialize(CheckpointIn &cp)
+{
+    assert(descQueue.size() == 0);
+    assert(recvDone->scheduled() == false);
+    assert(ckptRestore == false);
+
+    UNSERIALIZE_SCALAR(prevRecvTick);
+    // unserialize the receive desc queue
+    unsigned n_desc_queue;
+    UNSERIALIZE_SCALAR(n_desc_queue);
+    for (int i = 0; i < n_desc_queue; i++) {
+        Desc recv_desc;
+        recv_desc.unserializeSection(cp, csprintf("rxDesc_%d", i));
+        descQueue.push(recv_desc);
+    }
+    ckptRestore = true;
+}
+
+DistIface::DistIface(unsigned dist_rank,
+                     unsigned dist_size,
+                     Tick sync_start,
+                     Tick sync_repeat,
+                     EventManager *em,
+                     bool is_switch, int num_nodes) :
+    syncStart(sync_start), syncRepeat(sync_repeat),
+    recvThread(nullptr), recvScheduler(em),
+    rank(dist_rank), size(dist_size)
+{
+    DPRINTF(DistEthernet, "DistIface() ctor rank:%d\n",dist_rank);
+    isMaster = false;
+    if (master == nullptr) {
+        assert(sync == nullptr);
+        assert(syncEvent == nullptr);
+        if (is_switch)
+            sync = new SyncSwitch(num_nodes);
+        else
+            sync = new SyncNode();
+        syncEvent = new SyncEvent();
+        master = this;
+        isMaster = true;
+    }
+    distIfaceId = distIfaceNum;
+    distIfaceNum++;
+}
+
+DistIface::~DistIface()
+{
+    assert(recvThread);
+    delete recvThread;
+    if (this == master) {
+        assert(syncEvent);
+        delete syncEvent;
+        assert(sync);
+        delete sync;
+        master = nullptr;
+    }
+}
+
+void
+DistIface::packetOut(EthPacketPtr pkt, Tick send_delay)
+{
+    Header header;
+
+    // Prepare a dist header packet for the Ethernet packet we want to
+    // send out.
+    header.msgType = MsgType::dataDescriptor;
+    header.sendTick  = curTick();
+    header.sendDelay = send_delay;
+
+    header.dataPacketLength = pkt->size();
+
+    // Send out the packet and the meta info.
+    sendPacket(header, pkt);
+
+    DPRINTF(DistEthernetPkt,
+            "DistIface::sendDataPacket() done size:%d send_delay:%llu\n",
+            pkt->size(), send_delay);
+}
+
+void
+DistIface::recvThreadFunc(Event *recv_done, Tick link_delay)
+{
+    EthPacketPtr new_packet;
+    DistHeaderPkt::Header header;
+
+    // Initialize receive scheduler parameters
+    recvScheduler.init(recv_done, link_delay);
+
+    // Main loop to wait for and process any incoming message.
+    for (;;) {
+        // recvHeader() blocks until the next dist header packet comes in.
+        if (!recvHeader(header)) {
+            // We lost connection to the peer gem5 processes most likely
+            // because one of them called m5 exit. So we stop here.
+            // Grab the eventq lock to stop the simulation thread
+            curEventQueue()->lock();
+            exit_message("info",
+                         0,
+                         "Message server closed connection, "
+                         "simulation is exiting");
+        }
+
+        // We got a valid dist header packet, let's process it
+        if (header.msgType == MsgType::dataDescriptor) {
+            recvPacket(header, new_packet);
+            recvScheduler.pushPacket(new_packet,
+                                     header.sendTick,
+                                     header.sendDelay);
+        } else {
+            // everything else must be synchronisation related command
+            sync->progress(header.sendTick,
+                           header.syncRepeat,
+                           header.needCkpt,
+                           header.needExit);
+        }
+    }
+}
+
+void
+DistIface::spawnRecvThread(const Event *recv_done, Tick link_delay)
+{
+    assert(recvThread == nullptr);
+
+    recvThread = new std::thread(&DistIface::recvThreadFunc,
+                                 this,
+                                 const_cast<Event *>(recv_done),
+                                 link_delay);
+    recvThreadsNum++;
+}
+
+DrainState
+DistIface::drain()
+{
+    DPRINTF(DistEthernet,"DistIFace::drain() called\n");
+    // This can be called multiple times in the same drain cycle.
+    if (this == master)
+        syncEvent->draining(true);
+    return DrainState::Drained;
+}
+
+void
+DistIface::drainResume() {
+    DPRINTF(DistEthernet,"DistIFace::drainResume() called\n");
+    if (this == master)
+        syncEvent->draining(false);
+    recvScheduler.resumeRecvTicks();
+}
+
+void
+DistIface::serialize(CheckpointOut &cp) const
+{
+    // Drain the dist interface before the checkpoint is taken. We cannot call
+    // this as part of the normal drain cycle because this dist sync has to be
+    // called exactly once after the system is fully drained.
+    sync->drainComplete();
+
+    unsigned rank_orig = rank, dist_iface_id_orig = distIfaceId;
+
+    SERIALIZE_SCALAR(rank_orig);
+    SERIALIZE_SCALAR(dist_iface_id_orig);
+
+    recvScheduler.serializeSection(cp, "recvScheduler");
+    if (this == master) {
+        sync->serializeSection(cp, "Sync");
+    }
+}
+
+void
+DistIface::unserialize(CheckpointIn &cp)
+{
+    unsigned rank_orig, dist_iface_id_orig;
+    UNSERIALIZE_SCALAR(rank_orig);
+    UNSERIALIZE_SCALAR(dist_iface_id_orig);
+
+    panic_if(rank != rank_orig, "Rank mismatch at resume (rank=%d, orig=%d)",
+             rank, rank_orig);
+    panic_if(distIfaceId != dist_iface_id_orig, "Dist iface ID mismatch "
+             "at resume (distIfaceId=%d, orig=%d)", distIfaceId,
+             dist_iface_id_orig);
+
+    recvScheduler.unserializeSection(cp, "recvScheduler");
+    if (this == master) {
+        sync->unserializeSection(cp, "Sync");
+    }
+}
+
+void
+DistIface::init(const Event *done_event, Tick link_delay)
+{
+    // Init hook for the underlaying message transport to setup/finalize
+    // communication channels
+    initTransport();
+
+    // Spawn a new receiver thread that will process messages
+    // coming in from peer gem5 processes.
+    // The receive thread will also schedule a (receive) doneEvent
+    // for each incoming data packet.
+    spawnRecvThread(done_event, link_delay);
+
+
+    // Adjust the periodic sync start and interval. Different DistIface
+    // might have different requirements. The singleton sync object
+    // will select the minimum values for both params.
+    assert(sync != nullptr);
+    sync->init(syncStart, syncRepeat);
+
+    // Initialize the seed for random generator to avoid the same sequence
+    // in all gem5 peer processes
+    assert(master != nullptr);
+    if (this == master)
+        random_mt.init(5489 * (rank+1) + 257);
+}
+
+void
+DistIface::startup()
+{
+    DPRINTF(DistEthernet, "DistIface::startup() started\n");
+    if (this == master)
+        syncEvent->start();
+    DPRINTF(DistEthernet, "DistIface::startup() done\n");
+}
+
+bool
+DistIface::readyToCkpt(Tick delay, Tick period)
+{
+    bool ret = true;
+    DPRINTF(DistEthernet, "DistIface::readyToCkpt() called, delay:%lu "
+            "period:%lu\n", delay, period);
+    if (master) {
+        if (delay == 0) {
+            inform("m5 checkpoint called with zero delay => triggering collaborative "
+                   "checkpoint\n");
+            sync->requestCkpt(ReqType::collective);
+        } else {
+            inform("m5 checkpoint called with non-zero delay => triggering immediate "
+                   "checkpoint (at the next sync)\n");
+            sync->requestCkpt(ReqType::immediate);
+        }
+        if (period != 0)
+            inform("Non-zero period for m5_ckpt is ignored in "
+                   "distributed gem5 runs\n");
+        ret = false;
+    }
+    return ret;
+}
+
+bool
+DistIface::readyToExit(Tick delay)
+{
+    bool ret = true;
+    DPRINTF(DistEthernet, "DistIface::readyToExit() called, delay:%lu\n",
+            delay);
+    if (master) {
+        if (delay == 0) {
+            inform("m5 exit called with zero delay => triggering collaborative "
+                   "exit\n");
+            sync->requestExit(ReqType::collective);
+        } else {
+            inform("m5 exit called with non-zero delay => triggering immediate "
+                   "exit (at the next sync)\n");
+            sync->requestExit(ReqType::immediate);
+        }
+        ret = false;
+    }
+    return ret;
+}
+
+uint64_t
+DistIface::rankParam()
+{
+    uint64_t val;
+    if (master) {
+        val = master->rank;
+    } else {
+        warn("Dist-rank parameter is queried in single gem5 simulation.");
+        val = 0;
+    }
+    return val;
+}
+
+uint64_t
+DistIface::sizeParam()
+{
+    uint64_t val;
+    if (master) {
+        val = master->size;
+    } else {
+        warn("Dist-size parameter is queried in single gem5 simulation.");
+        val = 1;
+    }
+    return val;
+}
diff --git a/src/dev/net/dist_iface.hh b/src/dev/net/dist_iface.hh
new file mode 100644
index 000000000..e69211fb8
--- /dev/null
+++ b/src/dev/net/dist_iface.hh
@@ -0,0 +1,595 @@
+/*
+ * Copyright (c) 2015 ARM Limited
+ * All rights reserved
+ *
+ * The license below extends only to copyright in the software and shall
+ * not be construed as granting a license to any other intellectual
+ * property including but not limited to intellectual property relating
+ * to a hardware implementation of the functionality of the software
+ * licensed hereunder.  You may use the software subject to the license
+ * terms below provided that you ensure that this notice is replicated
+ * unmodified and in its entirety in all distributions of the software,
+ * modified or unmodified, in source code or in binary form.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met: redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer;
+ * redistributions in binary form must reproduce the above copyright
+ * notice, this list of conditions and the following disclaimer in the
+ * documentation and/or other materials provided with the distribution;
+ * neither the name of the copyright holders nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ * Authors: Gabor Dozsa
+ */
+
+/* @file
+ * The interface class for dist gem5 simulations.
+ *
+ * dist-gem5 is an extension to gem5 to enable parallel simulation of a
+ * distributed system (e.g. simulation of a pool of machines
+ * connected by Ethernet links). A dist gem5 run consists of seperate gem5
+ * processes running in parallel. Each gem5 process executes
+ * the simulation of a component of the simulated distributed system.
+ * (An example component can be a dist-core board with an Ethernet NIC.)
+ * The DistIface class below provides services to transfer data and
+ * control messages among the gem5 processes. The main such services are
+ * as follows.
+ *
+ * 1. Send a data packet coming from a simulated Ethernet link. The packet
+ * will be transferred to (all) the target(s) gem5 processes. The send
+ * operation is always performed by the simulation thread, i.e. the gem5
+ * thread that is processing the event queue associated with the simulated
+ * Ethernet link.
+ *
+ * 2. Spawn a receiver thread to process messages coming in from the
+ * from other gem5 processes. Each simulated Ethernet link has its own
+ * associated receiver thread. The receiver thread saves the incoming packet
+ * and schedule an appropriate receive event in the event queue.
+ *
+ * 3. Schedule a global barrier event periodically to keep the gem5
+ * processes in sync.
+ * Periodic barrier event to keep peer gem5 processes in sync. The basic idea
+ * is that no gem5 process can go ahead further than the simulated link
+ * transmission delay to ensure that a corresponding receive event can always
+ * be scheduled for any message coming in from a peer gem5 process.
+ *
+ *
+ *
+ * This interface is an abstract class. It can work with various low level
+ * send/receive service implementations (e.g. TCP/IP, MPI,...). A TCP
+ * stream socket version is implemented in src/dev/net/tcp_iface.[hh,cc].
+ */
+#ifndef __DEV_DIST_IFACE_HH__
+#define __DEV_DIST_IFACE_HH__
+
+#include <array>
+#include <mutex>
+#include <queue>
+#include <thread>
+#include <utility>
+
+#include "dev/net/dist_packet.hh"
+#include "dev/net/etherpkt.hh"
+#include "sim/core.hh"
+#include "sim/drain.hh"
+#include "sim/global_event.hh"
+#include "sim/serialize.hh"
+
+class EventManager;
+
+/**
+ * The interface class to talk to peer gem5 processes.
+ */
+class DistIface : public Drainable, public Serializable
+{
+  public:
+    typedef DistHeaderPkt::Header Header;
+
+  protected:
+    typedef DistHeaderPkt::MsgType MsgType;
+    typedef DistHeaderPkt::ReqType ReqType;
+
+  private:
+    class SyncEvent;
+    /** @class Sync
+     * This class implements global sync operations among gem5 peer processes.
+     *
+     * @note This class is used as a singleton object (shared by all DistIface
+     * objects).
+     */
+    class Sync : public Serializable
+    {
+      protected:
+        /**
+         * The lock to protect access to the Sync object.
+         */
+        std::mutex lock;
+        /**
+         * Condition variable for the simulation thread to wait on
+         * until all receiver threads completes the current global
+         * synchronisation.
+         */
+        std::condition_variable cv;
+        /**
+         * Number of receiver threads that not yet completed the current global
+         * synchronisation.
+         */
+        unsigned waitNum;
+        /**
+         * Flag is set if exit is permitted upon sync completion
+         */
+        bool doExit;
+        /**
+         * Flag is set if taking a ckpt is permitted upon sync completion
+         */
+        bool doCkpt;
+        /**
+         * The repeat value for the next periodic sync
+         */
+        Tick nextRepeat;
+        /**
+         * Tick for the very first periodic sync
+         */
+        Tick firstAt;
+        /**
+         * Tick for the next periodic sync (if the event is not scheduled yet)
+         */
+        Tick nextAt;
+
+        friend class SyncEvent;
+
+      public:
+        /**
+         * Initialize periodic sync params.
+         *
+         * @param start Start tick for dist synchronisation
+         * @param repeat Frequency of dist synchronisation
+         *
+         */
+        void init(Tick start, Tick repeat);
+        /**
+         *  Core method to perform a full dist sync.
+         */
+        virtual void run(bool same_tick) = 0;
+        /**
+         * Callback when the receiver thread gets a sync ack message.
+         */
+        virtual void progress(Tick send_tick,
+                              Tick next_repeat,
+                              ReqType do_ckpt,
+                              ReqType do_exit) = 0;
+
+        virtual void requestCkpt(ReqType req) = 0;
+        virtual void requestExit(ReqType req) = 0;
+
+        void drainComplete();
+
+        virtual void serialize(CheckpointOut &cp) const override = 0;
+        virtual void unserialize(CheckpointIn &cp) override = 0;
+    };
+
+    class SyncNode: public Sync
+    {
+      private:
+        /**
+         * Exit requested
+         */
+        ReqType needExit;
+        /**
+         * Ckpt requested
+         */
+        ReqType needCkpt;
+
+      public:
+
+        SyncNode();
+        ~SyncNode() {}
+        void run(bool same_tick) override;
+        void progress(Tick max_req_tick,
+                      Tick next_repeat,
+                      ReqType do_ckpt,
+                      ReqType do_exit) override;
+
+        void requestCkpt(ReqType req) override;
+        void requestExit(ReqType req) override;
+
+        void serialize(CheckpointOut &cp) const override;
+        void unserialize(CheckpointIn &cp) override;
+    };
+
+    class SyncSwitch: public Sync
+    {
+      private:
+        /**
+         * Counter for recording exit requests
+         */
+        unsigned numExitReq;
+        /**
+         * Counter for recording ckpt requests
+         */
+        unsigned numCkptReq;
+        /**
+         *  Number of connected simulated nodes
+         */
+        unsigned numNodes;
+
+      public:
+        SyncSwitch(int num_nodes);
+        ~SyncSwitch() {}
+
+        void run(bool same_tick) override;
+        void progress(Tick max_req_tick,
+                      Tick next_repeat,
+                      ReqType do_ckpt,
+                      ReqType do_exit) override;
+
+        void requestCkpt(ReqType) override {
+            panic("Switch requested checkpoint");
+        }
+        void requestExit(ReqType) override {
+            panic("Switch requested exit");
+        }
+
+        void serialize(CheckpointOut &cp) const override;
+        void unserialize(CheckpointIn &cp) override;
+    };
+
+    /**
+     * The global event to schedule periodic dist sync. It is used as a
+     * singleton object.
+     *
+     * The periodic synchronisation works as follows.
+     * 1. A SyncEvent is scheduled as a global event when startup() is
+     * called.
+     * 2. The process() method of the SyncEvent initiates a new barrier
+     * for each simulated Ethernet link.
+     * 3. Simulation thread(s) then waits until all receiver threads
+     * complete the ongoing barrier. The global sync event is done.
+     */
+    class SyncEvent : public GlobalSyncEvent
+    {
+      private:
+        /**
+         * Flag to set when the system is draining
+         */
+        bool _draining;
+      public:
+        /**
+         * Only the firstly instantiated DistIface object will
+         * call this constructor.
+         */
+        SyncEvent() : GlobalSyncEvent(Sim_Exit_Pri, 0), _draining(false) {}
+
+        ~SyncEvent() {}
+        /**
+         * Schedule the first periodic sync event.
+         */
+        void start();
+        /**
+         * This is a global event so process() will only be called by
+         * exactly one simulation thread. (See further comments in the .cc
+         * file.)
+         */
+        void process() override;
+
+        bool draining() const { return _draining; }
+        void draining(bool fl) { _draining = fl; }
+    };
+    /**
+     * Class to encapsulate information about data packets received.
+
+     * @note The main purpose of the class to take care of scheduling receive
+     * done events for the simulated network link and store incoming packets
+     * until they can be received by the simulated network link.
+     */
+    class RecvScheduler : public Serializable
+    {
+      private:
+        /**
+         * Received packet descriptor. This information is used by the receive
+         * thread to schedule receive events and by the simulation thread to
+         * process those events.
+         */
+        struct Desc : public Serializable
+        {
+            EthPacketPtr packet;
+            Tick sendTick;
+            Tick sendDelay;
+
+            Desc() : sendTick(0), sendDelay(0) {}
+            Desc(EthPacketPtr p, Tick s, Tick d) :
+                packet(p), sendTick(s), sendDelay(d) {}
+            Desc(const Desc &d) :
+                packet(d.packet), sendTick(d.sendTick), sendDelay(d.sendDelay) {}
+
+            void serialize(CheckpointOut &cp) const override;
+            void unserialize(CheckpointIn &cp) override;
+        };
+        /**
+         * The queue to store the receive descriptors.
+         */
+        std::queue<Desc> descQueue;
+        /**
+         * The tick when the most recent receive event was processed.
+         *
+         * @note This information is necessary to simulate possible receiver
+         * link contention when calculating the receive tick for the next
+         * incoming data packet (see the calcReceiveTick() method)
+         */
+        Tick prevRecvTick;
+        /**
+         * The receive done event for the simulated Ethernet link.
+         *
+         * @note This object is constructed by the simulated network link. We
+         * schedule this object for each incoming data packet.
+         */
+        Event *recvDone;
+        /**
+         * The link delay in ticks for the simulated Ethernet link.
+         *
+         * @note This value is used for calculating the receive ticks for
+         * incoming data packets.
+         */
+        Tick linkDelay;
+        /**
+         * The event manager associated with the simulated Ethernet link.
+         *
+         * @note It is used to access the event queue for scheduling receive
+         * done events for the link.
+         */
+        EventManager *eventManager;
+        /**
+         * Calculate the tick to schedule the next receive done event.
+         *
+         * @param send_tick The tick the packet was sent.
+         * @param send_delay The simulated delay at the sender side.
+         * @param prev_recv_tick Tick when the last receive event was
+         * processed.
+         *
+         * @note This method tries to take into account possible receiver link
+         * contention and adjust receive tick for the incoming packets
+         * accordingly.
+         */
+        Tick calcReceiveTick(Tick send_tick,
+                             Tick send_delay,
+                             Tick prev_recv_tick);
+
+        /**
+         * Flag to set if receive ticks for pending packets need to be
+         * recalculated due to changed link latencies at a resume
+         */
+        bool ckptRestore;
+
+      public:
+        /**
+         * Scheduler for the incoming data packets.
+         *
+         * @param em The event manager associated with the simulated Ethernet
+         * link.
+         */
+        RecvScheduler(EventManager *em) :
+            prevRecvTick(0), recvDone(nullptr), linkDelay(0),
+            eventManager(em), ckptRestore(false) {}
+
+        /**
+         *  Initialize network link parameters.
+         *
+         * @note This method is called from the receiver thread (see
+         * recvThreadFunc()).
+         */
+        void init(Event *recv_done, Tick link_delay);
+        /**
+         * Fetch the next packet that is to be received by the simulated network
+         * link.
+         *
+         * @note This method is called from the process() method of the receive
+         * done event associated with the network link.
+         */
+        EthPacketPtr popPacket();
+        /**
+         * Push a newly arrived packet into the desc queue.
+         */
+        void pushPacket(EthPacketPtr new_packet,
+                        Tick send_tick,
+                        Tick send_delay);
+
+        void serialize(CheckpointOut &cp) const override;
+        void unserialize(CheckpointIn &cp) override;
+        /**
+         * Adjust receive ticks for pending packets when restoring from a
+         * checkpoint
+         *
+         * @note Link speed and delay parameters may change at resume.
+         */
+        void resumeRecvTicks();
+    };
+    /**
+     * Tick to schedule the first dist sync event.
+     * This is just as optimization : we do not need any dist sync
+     * event until the simulated NIC is brought up by the OS.
+     */
+    Tick syncStart;
+    /**
+     * Frequency of dist sync events in ticks.
+     */
+    Tick syncRepeat;
+    /**
+     * Receiver thread pointer.
+     * Each DistIface object must have exactly one receiver thread.
+     */
+    std::thread *recvThread;
+    /**
+     * Meta information about data packets received.
+     */
+    RecvScheduler recvScheduler;
+
+  protected:
+    /**
+     * The rank of this process among the gem5 peers.
+     */
+    unsigned rank;
+    /**
+     * The number of gem5 processes comprising this dist simulation.
+     */
+    unsigned size;
+    /**
+     * Number of DistIface objects (i.e. dist links in this gem5 process)
+     */
+    static unsigned distIfaceNum;
+    /**
+     * Unique id for the dist link
+     */
+    unsigned distIfaceId;
+
+    bool isMaster;
+
+  private:
+    /**
+     * Number of receiver threads (in this gem5 process)
+     */
+    static unsigned recvThreadsNum;
+    /**
+     * The singleton Sync object to perform dist synchronisation.
+     */
+    static Sync *sync;
+    /**
+     * The singleton SyncEvent object to schedule periodic dist sync.
+     */
+    static SyncEvent *syncEvent;
+    /**
+     * The very first DistIface object created becomes the master. We need
+     * a master to co-ordinate the global synchronisation.
+     */
+    static DistIface *master;
+
+  private:
+    /**
+     * Send out a data packet to the remote end.
+     * @param header Meta info about the packet (which needs to be transferred
+     * to the destination alongside the packet).
+     * @param packet Pointer to the packet to send.
+     */
+    virtual void sendPacket(const Header &header, const EthPacketPtr &packet) = 0;
+    /**
+     * Send out a control command to the remote end.
+     * @param header Meta info describing the command (e.g. sync request)
+     */
+    virtual void sendCmd(const Header &header) = 0;
+    /**
+     * Receive a header (i.e. meta info describing a data packet or a control command)
+     * from the remote end.
+     * @param header The meta info structure to store the incoming header.
+     */
+    virtual bool recvHeader(Header &header) = 0;
+    /**
+     * Receive a packet from the remote end.
+     * @param header Meta info about the incoming packet (obtanied by a previous
+     * call to the recvHedaer() method).
+     * @param Pointer to packet received.
+     */
+    virtual void recvPacket(const Header &header, EthPacketPtr &packet) = 0;
+    /**
+     * Init hook for the underlaying transport
+     */
+    virtual void initTransport() = 0;
+    /**
+     * spawn the receiver thread.
+     * @param recv_done The receive done event associated with the simulated
+     * Ethernet link.
+     * @param link_delay The link delay for the simulated Ethernet link.
+     */
+    void spawnRecvThread(const Event *recv_done, Tick link_delay);
+    /**
+     * The function executed by a receiver thread.
+     */
+    void recvThreadFunc(Event *recv_done, Tick link_delay);
+
+  public:
+
+    /**
+     * ctor
+     * @param dist_rank Rank of this gem5 process within the dist run
+     * @param sync_start Start tick for dist synchronisation
+     * @param sync_repeat Frequency for dist synchronisation
+     * @param em The event manager associated with the simulated Ethernet link
+     */
+    DistIface(unsigned dist_rank,
+              unsigned dist_size,
+              Tick sync_start,
+              Tick sync_repeat,
+              EventManager *em,
+              bool is_switch,
+              int num_nodes);
+
+    virtual ~DistIface();
+    /**
+     * Send out an Ethernet packet.
+     * @param pkt The Ethernet packet to send.
+     * @param send_delay The delay in ticks for the send completion event.
+     */
+    void packetOut(EthPacketPtr pkt, Tick send_delay);
+    /**
+     * Fetch the packet scheduled to be received next by the simulated
+     * network link.
+     *
+     * @note This method is called within the process() method of the link
+     * receive done event. It also schedules the next receive event if the
+     * receive queue is not empty.
+     */
+    EthPacketPtr packetIn() { return recvScheduler.popPacket(); }
+
+    DrainState drain() override;
+    void drainResume() override;
+    void init(const Event *e, Tick link_delay);
+    void startup();
+
+    void serialize(CheckpointOut &cp) const override;
+    void unserialize(CheckpointIn &cp) override;
+    /**
+     * Initiate the exit from the simulation.
+     * @param delay Delay param from the m5 exit command. If Delay is zero
+     * then a collaborative exit is requested (i.e. all nodes have to call
+     * this method before the distributed simulation can exit). If Delay is
+     * not zero then exit is requested asap (and it will happen at the next
+     * sync tick).
+     * @return False if we are in distributed mode (i.e. exit can happen only
+     * at sync), True otherwise.
+     */
+    static bool readyToExit(Tick delay);
+    /**
+     * Initiate taking a checkpoint
+     * @param delay Delay param from the m5 checkpoint command. If Delay is
+     * zero then a collaborative checkpoint is requested (i.e. all nodes have
+     * to call this method before the checkpoint can be taken). If Delay is
+     * not zero then a checkpoint is requested asap (and it will happen at the
+     * next sync tick).
+     * @return False if we are in dist mode (i.e. exit can happen only at
+     * sync), True otherwise.
+     */
+    static bool readyToCkpt(Tick delay, Tick period);
+    /**
+     * Getter for the dist rank param.
+     */
+    static uint64_t rankParam();
+    /**
+     * Getter for the dist size param.
+     */
+    static uint64_t sizeParam();
+ };
+
+#endif
diff --git a/src/dev/net/multi_packet.hh b/src/dev/net/dist_packet.hh
index 3d8e85dfa..4c079c44a 100644
--- a/src/dev/net/multi_packet.hh
+++ b/src/dev/net/dist_packet.hh
@@ -38,93 +38,69 @@
  */
 
 /* @file
- * Header packet class for multi gem5 runs.
+ * Header packet class for dist-gem5 runs.
  *
- * For a high level description about multi gem5 see comments in
- * header file multi_iface.hh.
+ * For a high level description about dist-gem5 see comments in
+ * header file dist_iface.hh.
  *
- * The MultiHeaderPkt class defines the format of message headers
- * sent among gem5 processes during a multi gem5 simulation. A header packet
+ * The DistHeaderPkt class defines the format of message headers
+ * sent among gem5 processes during a dist gem5 simulation. A header packet
  * can either carry the description of data packet (i.e. a simulated Ethernet
  * packet) or a synchronisation related control command. In case of
  * data packet description, the corresponding data packet always follows
  * the header packet back-to-back.
  */
-#ifndef __DEV_NET_MULTI_PACKET_HH__
-#define __DEV_NET_MULTI_PACKET_HH__
+#ifndef __DEV_DIST_PACKET_HH__
+#define __DEV_DIST_PACKET_HH__
 
 #include <cstring>
 
 #include "base/types.hh"
 
-class MultiHeaderPkt
+class DistHeaderPkt
 {
   private:
-    MultiHeaderPkt() {}
-    ~MultiHeaderPkt() {}
+    DistHeaderPkt() {}
+    ~DistHeaderPkt() {}
 
   public:
+    enum class ReqType { immediate, collective, pending, none };
     /**
-     * Simply type to help with calculating space requirements for
-     * the corresponding header field.
-     */
-    typedef uint8_t AddressType[6];
-
-    /**
-     *  The msg type defines what informarion a multi header packet carries.
+     *  The msg type defines what information a dist header packet carries.
      */
     enum class MsgType
     {
         dataDescriptor,
-        cmdPeriodicSyncReq,
-        cmdPeriodicSyncAck,
-        cmdCkptSyncReq,
-        cmdCkptSyncAck,
-        cmdAtomicSyncReq,
-        cmdAtomicSyncAck,
+        cmdSyncReq,
+        cmdSyncAck,
         unknown
     };
 
     struct Header
     {
         /**
-         * The msg type field is valid for all header packets. In case of
-         * a synchronisation control command this is the only valid field.
+         * The msg type field is valid for all header packets.
+         *
+         * @note senderRank is used with data packets while collFlags are used
+         * by sync ack messages to trigger collective ckpt or exit events.
          */
         MsgType msgType;
         Tick sendTick;
-        Tick sendDelay;
-        /**
-         * Actual length of the simulated Ethernet packet.
-         */
-        unsigned dataPacketLength;
-        /**
-         * Source MAC address.
-         */
-        AddressType srcAddress;
-        /**
-         * Destination MAC address.
-         */
-        AddressType dstAddress;
+        union {
+            Tick sendDelay;
+            Tick syncRepeat;
+        };
+        union {
+            /**
+             * Actual length of the simulated Ethernet packet.
+             */
+            unsigned dataPacketLength;
+            struct {
+                ReqType needCkpt;
+                ReqType needExit;
+            };
+        };
     };
-
-    static unsigned maxAddressLength();
-
-    /**
-     * Static functions for manipulating and comparing MAC addresses.
-     */
-    static void clearAddress(AddressType &addr);
-    static bool isAddressEqual(const AddressType &addr1,
-                               const AddressType &addr2);
-    static bool isAddressLess(const AddressType &addr1,
-                              const AddressType &addr2);
-
-    static void copyAddress(AddressType &dest,
-                            const AddressType &src);
-
-    static bool isUnicastAddress(const AddressType &addr);
-    static bool isMulticastAddress(const AddressType &addr);
-    static bool isBroadcastAddress(const AddressType &addr);
 };
 
-#endif // __DEV_NET_MULTI_PACKET_HH__
+#endif
diff --git a/src/dev/net/etherpkt.cc b/src/dev/net/etherpkt.cc
index a16f572c5..f06af3306 100644
--- a/src/dev/net/etherpkt.cc
+++ b/src/dev/net/etherpkt.cc
@@ -53,19 +53,3 @@ EthPacketData::unserialize(const string &base, CheckpointIn &cp)
         arrayParamIn(cp, base + ".data", data, length);
 }
 
-void
-EthPacketData::packAddress(uint8_t *src_addr,
-                           uint8_t *dst_addr,
-                           unsigned &nbytes)
-{
-    Net::EthHdr *hdr = (Net::EthHdr *)data;
-    assert(hdr->src().size() == hdr->dst().size());
-    if (nbytes < hdr->src().size())
-        panic("EthPacketData::packAddress() Buffer overflow");
-
-    memcpy(dst_addr, hdr->dst().bytes(), hdr->dst().size());
-    memcpy(src_addr, hdr->src().bytes(), hdr->src().size());
-
-    nbytes = hdr->src().size();
-}
-
diff --git a/src/dev/net/etherpkt.hh b/src/dev/net/etherpkt.hh
index 4119578c3..457563293 100644
--- a/src/dev/net/etherpkt.hh
+++ b/src/dev/net/etherpkt.hh
@@ -71,18 +71,6 @@ class EthPacketData
     ~EthPacketData() { if (data) delete [] data; }
 
   public:
-    /**
-     * This function pulls out the MAC source and destination addresses from
-     * the packet data and stores them in the caller specified buffers.
-     *
-     * @param src_addr The buffer to store the source MAC address.
-     * @param dst_addr The buffer to store the destination MAC address.
-     * @param length This is an inout parameter. The caller stores in this
-     * the size of the address buffers. On return, this will contain the
-     * actual address size stored in the buffers. (We assume that source
-     * address size is equal to that of the destination address.)
-     */
-    void packAddress(uint8_t *src_addr, uint8_t *dst_addr, unsigned &length);
 
     void serialize(const std::string &base, CheckpointOut &cp) const;
     void unserialize(const std::string &base, CheckpointIn &cp);
diff --git a/src/dev/net/multi_iface.cc b/src/dev/net/multi_iface.cc
deleted file mode 100644
index 15f69f2ac..000000000
--- a/src/dev/net/multi_iface.cc
+++ /dev/null
@@ -1,622 +0,0 @@
-/*
- * Copyright (c) 2015 ARM Limited
- * All rights reserved
- *
- * The license below extends only to copyright in the software and shall
- * not be construed as granting a license to any other intellectual
- * property including but not limited to intellectual property relating
- * to a hardware implementation of the functionality of the software
- * licensed hereunder.  You may use the software subject to the license
- * terms below provided that you ensure that this notice is replicated
- * unmodified and in its entirety in all distributions of the software,
- * modified or unmodified, in source code or in binary form.
- *
- * Redistribution and use in source and binary forms, with or without
- * modification, are permitted provided that the following conditions are
- * met: redistributions of source code must retain the above copyright
- * notice, this list of conditions and the following disclaimer;
- * redistributions in binary form must reproduce the above copyright
- * notice, this list of conditions and the following disclaimer in the
- * documentation and/or other materials provided with the distribution;
- * neither the name of the copyright holders nor the names of its
- * contributors may be used to endorse or promote products derived from
- * this software without specific prior written permission.
- *
- * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
- * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
- * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
- * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
- * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
- * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
- * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
- * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
- * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
- * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
- * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
- *
- * Authors: Gabor Dozsa
- */
-
-/* @file
- * The interface class for multi gem5 simulations.
- */
-
-#include "dev/net/multi_iface.hh"
-
-#include <queue>
-#include <thread>
-
-#include "base/random.hh"
-#include "base/trace.hh"
-#include "debug/MultiEthernet.hh"
-#include "debug/MultiEthernetPkt.hh"
-#include "dev/net/etherpkt.hh"
-#include "sim/sim_exit.hh"
-#include "sim/sim_object.hh"
-
-
-MultiIface::Sync *MultiIface::sync = nullptr;
-MultiIface::SyncEvent *MultiIface::syncEvent = nullptr;
-unsigned MultiIface::recvThreadsNum = 0;
-MultiIface *MultiIface::master = nullptr;
-
-bool
-MultiIface::Sync::run(SyncTrigger t, Tick sync_tick)
-{
-    std::unique_lock<std::mutex> sync_lock(lock);
-
-    trigger = t;
-    if (trigger != SyncTrigger::periodic) {
-        DPRINTF(MultiEthernet,"MultiIface::Sync::run() trigger:%d\n",
-                (unsigned)trigger);
-    }
-
-    switch (state) {
-      case SyncState::asyncCkpt:
-        switch (trigger) {
-          case SyncTrigger::ckpt:
-            assert(MultiIface::syncEvent->interrupted == false);
-            state = SyncState::busy;
-            break;
-          case SyncTrigger::periodic:
-            if (waitNum == 0) {
-                // So all recv threads got an async checkpoint request already
-                // and a simExit is scheduled at the end of the current tick
-                // (i.e. it is a periodic sync scheduled at the same tick as
-                // the simExit).
-                state = SyncState::idle;
-                DPRINTF(MultiEthernet,"MultiIface::Sync::run() interrupted "
-                "due to async ckpt scheduled\n");
-                return false;
-            } else {
-                // we still need to wait for some receiver thread to get the
-                // aysnc ckpt request. We are going to proceed as 'interrupted'
-                // periodic sync.
-                state = SyncState::interrupted;
-                DPRINTF(MultiEthernet,"MultiIface::Sync::run() interrupted "
-                "due to ckpt request is coming in\n");
-            }
-            break;
-          case SyncTrigger::atomic:
-            assert(trigger != SyncTrigger::atomic);
-        }
-        break;
-      case SyncState::idle:
-        state = SyncState::busy;
-        break;
-        // Only one sync can be active at any time
-      case SyncState::interrupted:
-      case SyncState::busy:
-        assert(state != SyncState::interrupted);
-        assert(state != SyncState::busy);
-        break;
-    }
-    // Kick-off the sync unless we are in the middle of an interrupted
-    // periodic sync
-    if (state != SyncState::interrupted) {
-        assert(waitNum == 0);
-        waitNum = MultiIface::recvThreadsNum;
-        // initiate the global synchronisation
-        assert(MultiIface::master != nullptr);
-        MultiIface::master->syncRaw(triggerToMsg[(unsigned)trigger], sync_tick);
-    }
-    // now wait until all receiver threads complete the synchronisation
-    auto lf = [this]{ return waitNum == 0; };
-    cv.wait(sync_lock, lf);
-
-    // we are done
-    assert(state == SyncState::busy || state == SyncState::interrupted);
-    bool ret = (state != SyncState::interrupted);
-    state = SyncState::idle;
-    return ret;
-}
-
-void
-MultiIface::Sync::progress(MsgType msg)
-{
-    std::unique_lock<std::mutex> sync_lock(lock);
-
-    switch (msg) {
-      case MsgType::cmdAtomicSyncAck:
-        assert(state == SyncState::busy && trigger == SyncTrigger::atomic);
-        break;
-      case MsgType::cmdPeriodicSyncAck:
-        assert(state == SyncState::busy && trigger == SyncTrigger::periodic);
-        break;
-      case MsgType::cmdCkptSyncAck:
-        assert(state == SyncState::busy && trigger == SyncTrigger::ckpt);
-        break;
-      case MsgType::cmdCkptSyncReq:
-        switch (state) {
-          case SyncState::busy:
-            if (trigger == SyncTrigger::ckpt) {
-                // We are already in a checkpoint sync but got another ckpt
-                // sync request. This may happen if two (or more) peer gem5
-                // processes try to start a ckpt nearly at the same time.
-                // Incrementing waitNum here (before decrementing it below)
-                // effectively results in ignoring this new ckpt sync request.
-                waitNum++;
-                break;
-            }
-            assert (waitNum == recvThreadsNum);
-            state = SyncState::interrupted;
-            // we need to fall over here to handle "recvThreadsNum == 1" case
-          case SyncState::interrupted:
-            assert(trigger == SyncTrigger::periodic);
-            assert(waitNum >= 1);
-            if (waitNum == 1) {
-                exitSimLoop("checkpoint");
-            }
-            break;
-          case SyncState::idle:
-            // There is no on-going sync so we got an async ckpt request. If we
-            // are the only receiver thread then we need to schedule the
-            // checkpoint. Otherwise, only change the state to 'asyncCkpt' and
-            // let the last receiver thread to schedule the checkpoint at the
-            // 'asyncCkpt' case.
-            // Note that a periodic or resume sync may start later and that can
-            // trigger a state change to 'interrupted' (so the checkpoint may
-            // get scheduled at 'interrupted' case finally).
-            assert(waitNum == 0);
-            state = SyncState::asyncCkpt;
-            waitNum = MultiIface::recvThreadsNum;
-            // we need to fall over here to handle "recvThreadsNum == 1" case
-          case SyncState::asyncCkpt:
-            assert(waitNum >= 1);
-            if (waitNum == 1)
-                exitSimLoop("checkpoint");
-            break;
-          default:
-            panic("Unexpected state for checkpoint request message");
-            break;
-        }
-        break;
-      default:
-        panic("Unknown msg type");
-        break;
-    }
-    waitNum--;
-    assert(state != SyncState::idle);
-    // Notify the simultaion thread if there is an on-going sync.
-    if (state != SyncState::asyncCkpt) {
-        sync_lock.unlock();
-        cv.notify_one();
-    }
-}
-
-void MultiIface::SyncEvent::start(Tick start, Tick interval)
-{
-    assert(!scheduled());
-    if (interval == 0)
-        panic("Multi synchronisation period must be greater than zero");
-    repeat = interval;
-    schedule(start);
-}
-
-void
-MultiIface::SyncEvent::adjust(Tick start_tick, Tick repeat_tick)
-{
-    // The new multi interface may require earlier start of the
-    // synchronisation.
-    assert(scheduled() == true);
-    if (start_tick < when())
-        reschedule(start_tick);
-    // The new multi interface may require more frequent synchronisation.
-    if (repeat == 0)
-        panic("Multi synchronisation period must be greater than zero");
-    if (repeat < repeat_tick)
-        repeat = repeat_tick;
-}
-
-void
-MultiIface::SyncEvent::process()
-{
-    /*
-     * Note that this is a global event so this process method will be called
-     * by only exactly one thread.
-     */
-    // if we are draining the system then we must not start a periodic sync (as
-    // it is not sure that all peer gem5 will reach this tick before taking
-    // the checkpoint).
-    if (isDraining == true) {
-        assert(interrupted == false);
-        interrupted = true;
-        DPRINTF(MultiEthernet,"MultiIface::SyncEvent::process() interrupted "
-                "due to draining\n");
-        return;
-    }
-    if (interrupted == false)
-        scheduledAt = curTick();
-    /*
-     * We hold the eventq lock at this point but the receiver thread may
-     * need the lock to schedule new recv events while waiting for the
-     * multi sync to complete.
-     * Note that the other simulation threads also release their eventq
-     * locks while waiting for us due to the global event semantics.
-     */
-    curEventQueue()->unlock();
-    // we do a global sync here
-    interrupted = !MultiIface::sync->run(SyncTrigger::periodic, scheduledAt);
-    // Global sync completed or got interrupted.
-    // we are expected to exit with the eventq lock held
-    curEventQueue()->lock();
-    // schedule the next global sync event if this one completed. Otherwise
-    // (i.e. this one was interrupted by a checkpoint request), we will 
-    // reschedule this one after the draining is complete.
-    if (!interrupted)
-        schedule(scheduledAt + repeat);
-}
-
-void MultiIface::SyncEvent::resume()
-{
-    Tick sync_tick;
-    assert(!scheduled());
-    if (interrupted) {
-        assert(curTick() >= scheduledAt);
-        // We have to complete the interrupted periodic sync asap.
-        // Note that this sync might be interrupted now again with a checkpoint
-        // request from a peer gem5...
-        sync_tick = curTick();
-        schedule(sync_tick);
-    } else {
-        // So we completed the last periodic sync, let's find  out the tick for
-        // next one
-        assert(curTick() > scheduledAt);
-        sync_tick = scheduledAt + repeat;
-        if (sync_tick < curTick())
-            panic("Cannot resume periodic synchronisation");
-        schedule(sync_tick);
-    }
-    DPRINTF(MultiEthernet,
-            "MultiIface::SyncEvent periodic sync resumed at %lld "
-            "(curTick:%lld)\n", sync_tick, curTick());
-}
-
-void MultiIface::SyncEvent::serialize(const std::string &base,
-                                      CheckpointOut &cp) const
-{
-    // Save the periodic multi sync schedule information
-    paramOut(cp, base + ".periodicSyncRepeat", repeat);
-    paramOut(cp, base + ".periodicSyncInterrupted", interrupted);
-    paramOut(cp, base + ".periodicSyncAt", scheduledAt);
-}
-
-void MultiIface::SyncEvent::unserialize(const std::string &base,
-                                        CheckpointIn &cp)
-{
-    paramIn(cp, base + ".periodicSyncRepeat", repeat);
-    paramIn(cp, base + ".periodicSyncInterrupted", interrupted);
-    paramIn(cp, base + ".periodicSyncAt", scheduledAt);
-}
-
-MultiIface::MultiIface(unsigned multi_rank,
-                       Tick sync_start,
-                       Tick sync_repeat,
-                       EventManager *em) :
-    syncStart(sync_start), syncRepeat(sync_repeat),
-    recvThread(nullptr), eventManager(em), recvDone(nullptr),
-    scheduledRecvPacket(nullptr), linkDelay(0), rank(multi_rank)
-{
-    DPRINTF(MultiEthernet, "MultiIface() ctor rank:%d\n",multi_rank);
-    if (master == nullptr) {
-        assert(sync == nullptr);
-        assert(syncEvent == nullptr);
-        sync = new Sync();
-        syncEvent = new SyncEvent();
-        master = this;
-    }
-}
-
-MultiIface::~MultiIface()
-{
-    assert(recvThread);
-    delete recvThread;
-    if (this == master) {
-        assert(syncEvent);
-        delete syncEvent;
-        assert(sync);
-        delete sync;
-    }
-}
-
-void
-MultiIface::packetOut(EthPacketPtr pkt, Tick send_delay)
-{
-    MultiHeaderPkt::Header header_pkt;
-    unsigned address_length = MultiHeaderPkt::maxAddressLength();
-
-    // Prepare a multi header packet for the Ethernet packet we want to
-    // send out.
-    header_pkt.msgType = MsgType::dataDescriptor;
-    header_pkt.sendTick  = curTick();
-    header_pkt.sendDelay = send_delay;
-
-    // Store also the source and destination addresses.
-    pkt->packAddress(header_pkt.srcAddress, header_pkt.dstAddress,
-                     address_length);
-
-    header_pkt.dataPacketLength = pkt->size();
-
-    // Send out the multi hedare packet followed by the Ethernet packet.
-    sendRaw(&header_pkt, sizeof(header_pkt), header_pkt.dstAddress);
-    sendRaw(pkt->data, pkt->size(), header_pkt.dstAddress);
-    DPRINTF(MultiEthernetPkt,
-            "MultiIface::sendDataPacket() done size:%d send_delay:%llu "
-            "src:0x%02x%02x%02x%02x%02x%02x "
-            "dst:0x%02x%02x%02x%02x%02x%02x\n",
-            pkt->size(), send_delay,
-            header_pkt.srcAddress[0], header_pkt.srcAddress[1],
-            header_pkt.srcAddress[2], header_pkt.srcAddress[3],
-            header_pkt.srcAddress[4], header_pkt.srcAddress[5],
-            header_pkt.dstAddress[0], header_pkt.dstAddress[1],
-            header_pkt.dstAddress[2], header_pkt.dstAddress[3],
-            header_pkt.dstAddress[4], header_pkt.dstAddress[5]);
-}
-
-bool
-MultiIface::recvHeader(MultiHeaderPkt::Header &header_pkt)
-{
-    // Blocking receive of an incoming multi header packet.
-    return recvRaw((void *)&header_pkt, sizeof(header_pkt));
-}
-
-void
-MultiIface::recvData(const MultiHeaderPkt::Header &header_pkt)
-{
-    // We are here beacuse a header packet has been received implying
-    // that an Ethernet (data) packet is coming in next.
-    assert(header_pkt.msgType == MsgType::dataDescriptor);
-    // Allocate storage for the incoming Ethernet packet.
-    EthPacketPtr new_packet(new EthPacketData(header_pkt.dataPacketLength));
-    // Now execute the blocking receive and store the incoming data directly
-    // in the new EthPacketData object.
-    if (! recvRaw((void *)(new_packet->data), header_pkt.dataPacketLength))
-        panic("Missing data packet");
-
-    new_packet->length = header_pkt.dataPacketLength;
-    // Grab the event queue lock to schedule a new receive event for the
-    // data packet.
-    curEventQueue()->lock();
-    // Compute the receive tick. It includes the send delay and the
-    // simulated link delay.
-    Tick recv_tick = header_pkt.sendTick + header_pkt.sendDelay + linkDelay;
-    DPRINTF(MultiEthernetPkt, "MultiIface::recvThread() packet receive, "
-            "send_tick:%llu send_delay:%llu link_delay:%llu recv_tick:%llu\n",
-            header_pkt.sendTick, header_pkt.sendDelay, linkDelay, recv_tick);
-
-    if (recv_tick <= curTick()) {
-        panic("Simulators out of sync - missed packet receive by %llu ticks",
-              curTick() - recv_tick);
-    }
-    // Now we are about to schedule a recvDone event for the new data packet.
-    // We use the same recvDone object for all incoming data packets. If
-    // that is already scheduled - i.e. a receive event for a previous
-    // data packet is already pending - then we have to check whether the
-    // receive tick for the new packet is earlier than that of the currently
-    // pending event. Packets may arrive out-of-order with respect to
-    // simulated receive time. If that is the case, we need to re-schedule the
-    // recvDone event for the new packet. Otherwise, we save the packet
-    // pointer and the recv tick for the new packet in the recvQueue. See
-    // the implementation of the packetIn() method for comments on how this
-    // information is retrieved from the recvQueue by the simulation thread.
-    if (!recvDone->scheduled()) {
-        assert(recvQueue.size() == 0);
-        assert(scheduledRecvPacket == nullptr);
-        scheduledRecvPacket = new_packet;
-        eventManager->schedule(recvDone, recv_tick);
-    } else if (recvDone->when() > recv_tick) {
-        recvQueue.emplace(scheduledRecvPacket, recvDone->when());
-        eventManager->reschedule(recvDone, recv_tick);
-        scheduledRecvPacket = new_packet;
-    } else {
-        recvQueue.emplace(new_packet, recv_tick);
-    }
-    curEventQueue()->unlock();
-}
-
-void
-MultiIface::recvThreadFunc()
-{
-    EthPacketPtr new_packet;
-    MultiHeaderPkt::Header header;
-
-    // The new receiver thread shares the event queue with the simulation
-    // thread (associated with the simulated Ethernet link).
-    curEventQueue(eventManager->eventQueue());
-    // Main loop to wait for and process any incoming message.
-    for (;;) {
-        // recvHeader() blocks until the next multi header packet comes in.
-        if (!recvHeader(header)) {
-            // We lost connection to the peer gem5 processes most likely
-            // because one of them called m5 exit. So we stop here.
-            exit_message("info", 0, "Message server closed connection, "
-                         "simulation is exiting");
-        }
-        // We got a valid multi header packet, let's process it
-        if (header.msgType == MsgType::dataDescriptor) {
-            recvData(header);
-        } else {
-            // everything else must be synchronisation related command
-            sync->progress(header.msgType);
-        }
-    }
-}
-
-EthPacketPtr
-MultiIface::packetIn()
-{
-    // We are called within the process() method of the recvDone event. We
-    // return the packet that triggered the current receive event.
-    // If there is further packets in the recvQueue, we also have to schedule
-    // the recvEvent for the next packet with the smallest receive tick.
-    // The priority queue container ensures that smallest receive tick is
-    // always on the top of the queue.
-    assert(scheduledRecvPacket != nullptr);
-    EthPacketPtr next_packet = scheduledRecvPacket;
-
-    if (! recvQueue.empty()) {
-        eventManager->schedule(recvDone, recvQueue.top().second);
-        scheduledRecvPacket = recvQueue.top().first;
-        recvQueue.pop();
-    } else {
-        scheduledRecvPacket = nullptr;
-    }
-
-    return next_packet;
-}
-
-void
-MultiIface::spawnRecvThread(Event *recv_done, Tick link_delay)
-{
-    assert(recvThread == nullptr);
-    // all receive thread must be spawned before simulation starts
-    assert(eventManager->eventQueue()->getCurTick() == 0);
-
-    recvDone = recv_done;
-    linkDelay = link_delay;
-
-    recvThread = new std::thread(&MultiIface::recvThreadFunc, this);
-
-    recvThreadsNum++;
-}
-
-DrainState
-MultiIface::drain()
-{
-    DPRINTF(MultiEthernet,"MultiIFace::drain() called\n");
-
-    // This can be called multiple times in the same drain cycle.
-    if (master == this) {
-        syncEvent->isDraining = true;
-    }
-
-    return DrainState::Drained;
-}
-
-void MultiIface::drainDone() {
-    if (master == this) {
-        assert(syncEvent->isDraining == true);
-        syncEvent->isDraining = false;
-        // We need to resume the interrupted periodic sync here now that the
-        // draining is done. If the last periodic sync completed before the
-        // checkpoint then the next one is already scheduled.
-        if (syncEvent->interrupted)
-            syncEvent->resume();
-    }
-}
-
-void MultiIface::serialize(const std::string &base, CheckpointOut &cp) const
-{
-    // Drain the multi interface before the checkpoint is taken. We cannot call
-    // this as part of the normal drain cycle because this multi sync has to be
-    // called exactly once after the system is fully drained.
-    // Note that every peer will take a checkpoint but they may take it at
-    // different ticks.
-    // This sync request may interrupt an on-going periodic sync in some peers.
-    sync->run(SyncTrigger::ckpt, curTick());
-
-    // Save the periodic multi sync status
-    syncEvent->serialize(base, cp);
-
-    unsigned n_rx_packets = recvQueue.size();
-    if (scheduledRecvPacket != nullptr)
-        n_rx_packets++;
-
-    paramOut(cp, base + ".nRxPackets", n_rx_packets);
-
-    if (n_rx_packets > 0) {
-        assert(recvDone->scheduled());
-        scheduledRecvPacket->serialize(base + ".rxPacket[0]", cp);
-    }
-
-    for (unsigned i=1; i < n_rx_packets; i++)  {
-        const RecvInfo recv_info = recvQueue.impl().at(i-1);
-        recv_info.first->serialize(base + csprintf(".rxPacket[%d]", i), cp);
-        Tick rx_tick = recv_info.second;
-        paramOut(cp, base + csprintf(".rxTick[%d]", i), rx_tick);
-    }
-}
-
-void MultiIface::unserialize(const std::string &base, CheckpointIn &cp)
-{
-    assert(recvQueue.size() == 0);
-    assert(scheduledRecvPacket == nullptr);
-    assert(recvDone->scheduled() == false);
-
-    // restore periodic sync info
-    syncEvent->unserialize(base, cp);
-
-    unsigned n_rx_packets;
-    paramIn(cp, base + ".nRxPackets", n_rx_packets);
-
-    if (n_rx_packets > 0) {
-        scheduledRecvPacket = std::make_shared<EthPacketData>(16384);
-        scheduledRecvPacket->unserialize(base + ".rxPacket[0]", cp);
-        // Note: receive event will be scheduled when the link is unserialized
-    }
-
-    for (unsigned i=1; i < n_rx_packets; i++) {
-        EthPacketPtr rx_packet = std::make_shared<EthPacketData>(16384);
-        rx_packet->unserialize(base + csprintf(".rxPacket[%d]", i), cp);
-        Tick rx_tick = 0;
-        paramIn(cp, base + csprintf(".rxTick[%d]", i), rx_tick);
-        assert(rx_tick > 0);
-        recvQueue.emplace(rx_packet,rx_tick);
-    }
-}
-
-void MultiIface::initRandom()
-{
-    // Initialize the seed for random generator to avoid the same sequence
-    // in all gem5 peer processes
-    assert(master != nullptr);
-    if (this == master)
-        random_mt.init(5489 * (rank+1) + 257);
-}
-
-void MultiIface::startPeriodicSync()
-{
-    DPRINTF(MultiEthernet, "MultiIface:::initPeriodicSync started\n");
-    // Do a global sync here to ensure that peer gem5 processes are around
-    // (actually this may not be needed...)
-    sync->run(SyncTrigger::atomic, curTick());
-
-    // Start the periodic sync if it is a fresh simulation from scratch
-    if (curTick() == 0) {
-        if (this == master) {
-        syncEvent->start(syncStart, syncRepeat);
-        inform("Multi synchronisation activated: start at %lld, "
-               "repeat at every %lld ticks.\n",
-               syncStart, syncRepeat);
-        } else {
-            // In case another multiIface object requires different schedule
-            // for periodic sync than the master does.
-            syncEvent->adjust(syncStart, syncRepeat);
-        }
-    } else {
-        // Schedule the next periodic sync if resuming from a checkpoint
-        if (this == master)
-            syncEvent->resume();
-    }
-    DPRINTF(MultiEthernet, "MultiIface::initPeriodicSync done\n");
-}
diff --git a/src/dev/net/multi_iface.hh b/src/dev/net/multi_iface.hh
deleted file mode 100644
index f8ce2abf7..000000000
--- a/src/dev/net/multi_iface.hh
+++ /dev/null
@@ -1,492 +0,0 @@
-/*
- * Copyright (c) 2015 ARM Limited
- * All rights reserved
- *
- * The license below extends only to copyright in the software and shall
- * not be construed as granting a license to any other intellectual
- * property including but not limited to intellectual property relating
- * to a hardware implementation of the functionality of the software
- * licensed hereunder.  You may use the software subject to the license
- * terms below provided that you ensure that this notice is replicated
- * unmodified and in its entirety in all distributions of the software,
- * modified or unmodified, in source code or in binary form.
- *
- * Redistribution and use in source and binary forms, with or without
- * modification, are permitted provided that the following conditions are
- * met: redistributions of source code must retain the above copyright
- * notice, this list of conditions and the following disclaimer;
- * redistributions in binary form must reproduce the above copyright
- * notice, this list of conditions and the following disclaimer in the
- * documentation and/or other materials provided with the distribution;
- * neither the name of the copyright holders nor the names of its
- * contributors may be used to endorse or promote products derived from
- * this software without specific prior written permission.
- *
- * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
- * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
- * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
- * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
- * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
- * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
- * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
- * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
- * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
- * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
- * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
- *
- * Authors: Gabor Dozsa
- */
-
-/* @file
- * The interface class for multi gem5 simulations.
- *
- * Multi gem5 is an extension to gem5 to enable parallel simulation of a
- * distributed system (e.g. simulation of a pool of machines
- * connected by Ethernet links). A multi gem5 run consists of seperate gem5
- * processes running in parallel. Each gem5 process executes
- * the simulation of a component of the simulated distributed system.
- * (An example component can be a multi-core board with an Ethernet NIC.)
- * The MultiIface class below provides services to transfer data and
- * control messages among the gem5 processes. The main such services are
- * as follows.
- *
- * 1. Send a data packet coming from a simulated Ethernet link. The packet
- * will be transferred to (all) the target(s) gem5 processes. The send
- * operation is always performed by the simulation thread, i.e. the gem5
- * thread that is processing the event queue associated with the simulated
- * Ethernet link.
- *
- * 2. Spawn a receiver thread to process messages coming in from the
- * from other gem5 processes. Each simulated Ethernet link has its own
- * associated receiver thread. The receiver thread saves the incoming packet
- * and schedule an appropriate receive event in the event queue.
- *
- * 3. Schedule a global barrier event periodically to keep the gem5
- * processes in sync.
- * Periodic barrier event to keep peer gem5 processes in sync. The basic idea
- * is that no gem5 process can go ahead further than the simulated link
- * transmission delay to ensure that a corresponding receive event can always
- * be scheduled for any message coming in from a peer gem5 process.
- *
- *
- *
- * This interface is an abstract class (sendRaw() and recvRaw()
- * methods are pure virtual). It can work with various low level
- * send/receive service implementations (e.g. TCP/IP, MPI,...). A TCP
- * stream socket version is implemented in dev/src/tcp_iface.[hh,cc].
- */
-#ifndef __DEV_NET_MULTI_IFACE_HH__
-#define __DEV_NET_MULTI_IFACE_HH__
-
-#include <array>
-#include <mutex>
-#include <queue>
-#include <thread>
-#include <utility>
-
-#include "dev/net/etherpkt.hh"
-#include "dev/net/multi_packet.hh"
-#include "sim/core.hh"
-#include "sim/drain.hh"
-#include "sim/global_event.hh"
-
-class EventManager;
-
-/**
- * The interface class to talk to peer gem5 processes.
- */
-class MultiIface : public Drainable
-{
-  public:
-    /*!
-     * The possible reasons a multi sync among gem5 peers is needed for.
-     */
-    enum
-    class SyncTrigger {
-        periodic, /*!< Regular periodic sync. This can be interrupted by a
-                   checkpoint sync request */
-        ckpt,     /*!< sync before taking a checkpoint */
-        atomic    /*!< sync that cannot be interrupted (e.g. sync at startup) */
-    };
-
-  private:
-    typedef MultiHeaderPkt::MsgType MsgType;
-
-    /** Sync State-Machine
-     \dot
-     digraph Sync {
-     node [shape=box, fontsize=10];
-     idle -> busy
-     [ label="new trigger\n by run()" fontsize=8 ];
-     busy -> busy
-     [ label="new message by progress():\n(msg == SyncAck &&\nwaitNum > 1) || \n(msg==CkptSyncReq &&\ntrigger == ckpt)" fontsize=8 ];
-     busy -> idle
-     [ label="new message by progress():\n(msg == SyncAck &&\nwaitNum == 1)" fontsize=8 ];
-     busy -> interrupted
-     [ label="new message by progress():\n(msg == CkptSyncReq &&\ntrigger == periodic)" fontsize=8 ];
-     idle -> asyncCkpt
-     [ label="new message by progress():\nmsg == CkptSyncReq" fontsize=8 ];
-     asyncCkpt -> asyncCkpt
-     [ label="new message by progress():\nmsg == CkptSyncReq" fontsize=8 ];
-     asyncCkpt -> busy
-     [ label="new trigger by run():\ntrigger == ckpt" fontsize=8 ];
-     asyncCkpt -> idle
-     [ label="new trigger by run():\n(trigger == periodic &&\nwaitNum == 0) " fontsize=8 ];
-     asyncCkpt -> interrupted
-     [ label="new trigger by run():\n(trigger == periodic &&\nwaitNum > 0) " fontsize=8 ];
-     interrupted -> interrupted
-     [ label="new message by progress():\n(msg == CkptSyncReq &&\nwaitNum > 1)" fontsize=8 ];
-     interrupted -> idle
-     [ label="new message by progress():\n(msg == CkptSyncReq &&\nwaitNum == 1)" fontsize=8 ];
-     }
-     \enddot
-     */
-    /** @class Sync
-     * This class implements global sync operations among gem5 peer processes.
-     *
-     * @note This class is used as a singleton object (shared by all MultiIface
-     * objects).
-     */
-    class Sync
-    {
-      private:
-        /*!
-         * Internal state of the sync singleton object.
-         */
-        enum class SyncState {
-            busy,        /*!< There is an on-going sync. */
-            interrupted, /*!< An on-going periodic sync was interrupted. */
-            asyncCkpt,   /*!< A checkpoint (sim_exit) is already scheduled */
-            idle         /*!< There is no active sync. */
-        };
-        /**
-         * The lock to protect access to the MultiSync object.
-         */
-        std::mutex lock;
-        /**
-         * Condition variable for the simulation thread to wait on
-         * until all receiver threads completes the current global
-         * synchronisation.
-         */
-        std::condition_variable cv;
-        /**
-         * Number of receiver threads that not yet completed the current global
-         * synchronisation.
-         */
-        unsigned waitNum;
-        /**
-         * The trigger for the most recent sync.
-         */
-        SyncTrigger trigger;
-        /**
-         * Map sync triggers to request messages.
-         */
-        std::array<MsgType, 3> triggerToMsg = {{
-                MsgType::cmdPeriodicSyncReq,
-                MsgType::cmdCkptSyncReq,
-                MsgType::cmdAtomicSyncReq
-            }};
-
-        /**
-         * Current sync state.
-         */
-        SyncState state;
-
-      public:
-        /**
-         *  Core method to perform a full multi sync.
-         *
-         * @param t Sync trigger.
-         * @param sync_tick The tick the sync was expected to happen at.
-         * @return true if the sync completed, false if it was interrupted.
-         *
-         * @note In case of an interrupted periodic sync, sync_tick can be less
-         * than curTick() when we resume (i.e. re-run) it
-         */
-        bool run(SyncTrigger t, Tick sync_tick);
-        /**
-         * Callback when the receiver thread gets a sync message.
-         */
-        void progress(MsgType m);
-
-        Sync() : waitNum(0), state(SyncState::idle) {}
-        ~Sync() {}
-    };
-
-
-    /**
-     * The global event to schedule peridic multi sync. It is used as a
-     * singleton object.
-     *
-     * The periodic synchronisation works as follows.
-     * 1. A MultisyncEvent is scheduled as a global event when startup() is
-     * called.
-     * 2. The progress() method of the MultisyncEvent initiates a new barrier
-     * for each simulated Ethernet links.
-     * 3. Simulation thread(s) then waits until all receiver threads
-     * completes the ongoing barrier. The global sync event is done.
-     */
-    class SyncEvent : public GlobalSyncEvent
-    {
-      public:
-        /**
-         * Flag to indicate that the most recent periodic sync was interrupted
-         * (by a checkpoint request).
-         */
-        bool interrupted;
-        /**
-         * The tick when the most recent periodic synchronisation was scheduled
-         * at.
-         */
-        Tick scheduledAt;
-        /**
-         * Flag to indicate an on-going drain cycle.
-         */
-         bool isDraining;
-
-      public:
-        /**
-         * Only the firstly instanstiated MultiIface object will
-         * call this constructor.
-         */
-        SyncEvent() : GlobalSyncEvent(Default_Pri, 0), interrupted(false),
-                      scheduledAt(0), isDraining(false) {}
-
-        ~SyncEvent() { assert (scheduled() == false); }
-        /**
-         * Schedule the first periodic sync event.
-         *
-         * @param start Start tick for multi synchronisation
-         * @param repeat Frequency of multi synchronisation
-         *
-         */
-        void start(Tick start, Tick repeat);
-        /**
-         * Reschedule (if necessary) the periodic sync event.
-         *
-         * @param start Start tick for multi synchronisation
-         * @param repeat Frequency of multi synchronisation
-         *
-         * @note Useful if we have multiple MultiIface objects with
-         * different 'start' and 'repeat' values for global sync.
-         */
-        void adjust(Tick start, Tick repeat);
-        /**
-         * This is a global event so process() will be called by each
-         * simulation threads. (See further comments in the .cc file.)
-         */
-        void process() override;
-        /**
-         * Schedule periodic sync when resuming from a checkpoint.
-         */
-        void resume();
-
-        void serialize(const std::string &base, CheckpointOut &cp) const;
-        void unserialize(const std::string &base, CheckpointIn &cp);
-    };
-
-    /**
-     * The receive thread needs to store the packet pointer and the computed
-     * receive tick for each incoming data packet. This information is used
-     * by the simulation thread when it processes the corresponding receive
-     * event. (See more comments at the implemetation of the recvThreadFunc()
-     * and RecvPacketIn() methods.)
-     */
-    typedef std::pair<EthPacketPtr, Tick> RecvInfo;
-
-    /**
-     * Comparison predicate for RecvInfo, needed by the recvQueue.
-     */
-    struct RecvInfoCompare {
-        bool operator()(const RecvInfo &lhs, const RecvInfo &rhs)
-        {
-            return lhs.second > rhs.second;
-        }
-    };
-
-    /**
-     * Customized priority queue used to store incoming data packets info by
-     * the receiver thread. We need to expose the underlying container to
-     * enable iterator access for serializing.
-     */
-    class RecvQueue : public std::priority_queue<RecvInfo,
-                                                 std::vector<RecvInfo>,
-                                                 RecvInfoCompare>
-    {
-      public:
-        std::vector<RecvInfo> &impl() { return c; }
-        const std::vector<RecvInfo> &impl() const { return c; }
-    };
-
-    /*
-     * The priority queue to store RecvInfo items ordered by receive ticks.
-     */
-    RecvQueue recvQueue;
-    /**
-     * The singleton Sync object to perform multi synchronisation.
-     */
-    static Sync *sync;
-    /**
-     * The singleton SyncEvent object to schedule periodic multi sync.
-     */
-    static SyncEvent *syncEvent;
-    /**
-     * Tick to schedule the first multi sync event.
-     * This is just as optimization : we do not need any multi sync
-     * event until the simulated NIC is brought up by the OS.
-     */
-    Tick syncStart;
-    /**
-     * Frequency of multi sync events in ticks.
-     */
-    Tick syncRepeat;
-    /**
-     * Receiver thread pointer.
-     * Each MultiIface object must have exactly one receiver thread.
-     */
-    std::thread *recvThread;
-    /**
-     * The event manager associated with the MultiIface object.
-     */
-    EventManager *eventManager;
-
-    /**
-     * The receive done event for the simulated Ethernet link.
-     * It is scheduled by the receiver thread for each incoming data
-     * packet.
-     */
-    Event *recvDone;
-
-    /**
-     * The packet that belongs to the currently scheduled recvDone event.
-     */
-    EthPacketPtr scheduledRecvPacket;
-
-    /**
-     * The link delay in ticks for the simulated Ethernet link.
-     */
-    Tick linkDelay;
-
-    /**
-     * The rank of this process among the gem5 peers.
-     */
-    unsigned rank;
-    /**
-     * Total number of receiver threads (in this gem5 process).
-     * During the simulation it should be constant and equal to the
-     * number of MultiIface objects (i.e. simulated Ethernet
-     * links).
-     */
-    static unsigned recvThreadsNum;
-    /**
-     * The very first MultiIface object created becomes the master. We need
-     * a master to co-ordinate the global synchronisation.
-     */
-    static MultiIface *master;
-
-  protected:
-    /**
-     * Low level generic send routine.
-     * @param buf buffer that holds the data to send out
-     * @param length number of bytes to send
-     * @param dest_addr address of the target (simulated NIC). This may be
-     * used by a subclass for optimization (e.g. optimize broadcast)
-     */
-    virtual void sendRaw(void *buf,
-                         unsigned length,
-                         const MultiHeaderPkt::AddressType dest_addr) = 0;
-    /**
-     * Low level generic receive routine.
-     * @param buf the buffer to store the incoming message
-     * @param length buffer size (in bytes)
-     */
-    virtual bool recvRaw(void *buf, unsigned length) = 0;
-    /**
-     * Low level request for synchronisation among gem5 processes. Only one
-     * MultiIface object needs to call this (in each gem5 process) to trigger
-     * a multi sync.
-     *
-     * @param sync_req Sync request command.
-     * @param sync_tick The tick when sync is expected to happen in the sender.
-     */
-    virtual void syncRaw(MsgType sync_req, Tick sync_tick) = 0;
-    /**
-     * The function executed by a receiver thread.
-     */
-    void recvThreadFunc();
-    /**
-     * Receive a multi header packet. Called by the receiver thread.
-     * @param header the structure to store the incoming header packet.
-     * @return false if any error occured during the receive, true otherwise
-     *
-     * A header packet can carry a control command (e.g. 'barrier leave') or
-     * information about a data packet that is following the header packet
-     * back to back.
-     */
-    bool recvHeader(MultiHeaderPkt::Header &header);
-    /**
-     * Receive a data packet. Called by the receiver thread.
-     * @param data_header The packet descriptor for the expected incoming data
-     * packet.
-     */
-    void recvData(const MultiHeaderPkt::Header &data_header);
-
-  public:
-
-    /**
-     * ctor
-     * @param multi_rank Rank of this gem5 process within the multi run
-     * @param sync_start Start tick for multi synchronisation
-     * @param sync_repeat Frequency for multi synchronisation
-     * @param em The event manager associated with the simulated Ethernet link
-     */
-    MultiIface(unsigned multi_rank,
-               Tick sync_start,
-               Tick sync_repeat,
-               EventManager *em);
-
-    virtual ~MultiIface();
-    /**
-     * Send out an Ethernet packet.
-     * @param pkt The Ethernet packet to send.
-     * @param send_delay The delay in ticks for the send completion event.
-     */
-    void packetOut(EthPacketPtr pkt, Tick send_delay);
-    /**
-     * Fetch the next packet from the receive queue.
-     */
-    EthPacketPtr packetIn();
-
-    /**
-     * spawn the receiver thread.
-     * @param recv_done The receive done event associated with the simulated
-     * Ethernet link.
-     * @param link_delay The link delay for the simulated Ethernet link.
-     */
-    void spawnRecvThread(Event *recv_done,
-                         Tick link_delay);
-    /**
-     * Initialize the random number generator with a different seed in each
-     * peer gem5 process.
-     */
-    void initRandom();
-
-    DrainState drain() override;
-
-    /**
-     * Callback when draining is complete.
-     */
-    void drainDone();
-
-    /**
-     * Initialize the periodic synchronisation among peer gem5 processes.
-     */
-    void startPeriodicSync();
-
-    void serialize(const std::string &base, CheckpointOut &cp) const;
-    void unserialize(const std::string &base, CheckpointIn &cp);
-
-};
-
-
-#endif // __DEV_NET_MULTI_IFACE_HH__
diff --git a/src/dev/net/tcp_iface.cc b/src/dev/net/tcp_iface.cc
index 035ec8fd0..38fc7aef2 100644
--- a/src/dev/net/tcp_iface.cc
+++ b/src/dev/net/tcp_iface.cc
@@ -35,25 +35,35 @@
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  *
  * Authors: Gabor Dozsa
+ *          Mohammad Alian
  */
 
 /* @file
- * TCP stream socket based interface class implementation for multi gem5 runs.
+ * TCP stream socket based interface class implementation for dist-gem5 runs.
  */
 
 #include "dev/net/tcp_iface.hh"
 
 #include <arpa/inet.h>
 #include <netdb.h>
+#include <netinet/tcp.h>
 #include <sys/socket.h>
 #include <sys/types.h>
 #include <unistd.h>
 
 #include <cerrno>
 #include <cstring>
+#include <vector>
 
 #include "base/types.hh"
-#include "debug/MultiEthernet.hh"
+#include "debug/DistEthernet.hh"
+#include "debug/DistEthernetCmd.hh"
+#include "sim/sim_exit.hh"
+
+#if defined(__FreeBSD__)
+#include <netinet/in.h>
+
+#endif
 
 // MSG_NOSIGNAL does not exists on OS X
 #if defined(__APPLE__) || defined(__MACH__)
@@ -64,42 +74,181 @@
 
 using namespace std;
 
+std::vector<std::pair<TCPIface::NodeInfo, int> > TCPIface::nodes;
 vector<int> TCPIface::sockRegistry;
+int TCPIface::fdStatic = -1;
+bool TCPIface::anyListening = false;
 
 TCPIface::TCPIface(string server_name, unsigned server_port,
-                   unsigned multi_rank, Tick sync_start, Tick sync_repeat,
-                   EventManager *em) :
-    MultiIface(multi_rank, sync_start, sync_repeat, em)
+                   unsigned dist_rank, unsigned dist_size,
+                   Tick sync_start, Tick sync_repeat,
+                   EventManager *em, bool is_switch, int num_nodes) :
+    DistIface(dist_rank, dist_size, sync_start, sync_repeat, em,
+              is_switch, num_nodes), serverName(server_name),
+    serverPort(server_port), isSwitch(is_switch), listening(false)
 {
-    struct addrinfo addr_hint, *addr_results;
+    if (is_switch && isMaster) {
+        while (!listen(serverPort)) {
+            DPRINTF(DistEthernet, "TCPIface(listen): Can't bind port %d\n",
+                    serverPort);
+            serverPort++;
+        }
+        inform("tcp_iface listening on port %d", serverPort);
+        // Now accept the first connection requests from each compute node and
+        // store the node info. The compute nodes will then wait for ack
+        // messages. Ack messages will be sent by initTransport() in the
+        // appropriate order to make sure that every compute node is always
+        // connected to the same switch port.
+        NodeInfo ni;
+        for (int i = 0; i < size; i++) {
+            accept();
+            DPRINTF(DistEthernet, "First connection, waiting for link info\n");
+            if (!recvTCP(sock, &ni, sizeof(ni)))
+                panic("Failed to receive link info");
+            nodes.push_back(make_pair(ni, sock));
+        }
+    }
+}
+
+bool
+TCPIface::listen(int port)
+{
+    if (listening)
+        panic("Socket already listening!");
+
+    struct sockaddr_in sockaddr;
     int ret;
 
-    string port_str = to_string(server_port);
+    fdStatic = socket(PF_INET, SOCK_STREAM, IPPROTO_TCP);
+    panic_if(fdStatic < 0, "socket() failed: %s", strerror(errno));
 
-    sock = socket(PF_INET, SOCK_STREAM, IPPROTO_TCP);
-    panic_if(sock < 0, "socket() failed: %s", strerror(errno));
+    sockaddr.sin_family = PF_INET;
+    sockaddr.sin_addr.s_addr = INADDR_ANY;
+    sockaddr.sin_port = htons(port);
+    // finally clear sin_zero
+    memset(&sockaddr.sin_zero, 0, sizeof(sockaddr.sin_zero));
+    ret = ::bind(fdStatic, (struct sockaddr *)&sockaddr, sizeof (sockaddr));
 
-    bzero(&addr_hint, sizeof(addr_hint));
-    addr_hint.ai_family = AF_INET;
-    addr_hint.ai_socktype = SOCK_STREAM;
-    addr_hint.ai_protocol = IPPROTO_TCP;
+    if (ret != 0) {
+        if (ret == -1 && errno != EADDRINUSE)
+            panic("ListenSocket(listen): bind() failed!");
+        return false;
+    }
 
-    ret = getaddrinfo(server_name.c_str(), port_str.c_str(),
-                      &addr_hint, &addr_results);
-    panic_if(ret < 0, "getaddrinf() failed: %s", strerror(errno));
+    if (::listen(fdStatic, 24) == -1) {
+        if (errno != EADDRINUSE)
+            panic("ListenSocket(listen): listen() failed!");
 
-    DPRINTF(MultiEthernet, "Connecting to %s:%u\n",
-            server_name.c_str(), port_str.c_str());
+        return false;
+    }
 
-    ret = ::connect(sock, (struct sockaddr *)(addr_results->ai_addr),
-                    addr_results->ai_addrlen);
-    panic_if(ret < 0, "connect() failed: %s", strerror(errno));
+    listening = true;
+    anyListening = true;
+    return true;
+}
 
-    freeaddrinfo(addr_results);
-    // add our socket to the static registry
+void
+TCPIface::establishConnection()
+{
+    static unsigned cur_rank = 0;
+    static unsigned cur_id = 0;
+    NodeInfo ni;
+
+    if (isSwitch) {
+        if (cur_id == 0) { // first connection accepted in the ctor already
+            auto const &iface0 =
+                find_if(nodes.begin(), nodes.end(),
+                        [](const pair<NodeInfo, int> &cn) -> bool {
+                            return cn.first.rank == cur_rank;
+                        });
+            assert(iface0 != nodes.end());
+            assert(iface0->first.distIfaceId == 0);
+            sock = iface0->second;
+            ni = iface0->first;
+        } else { // additional connections from the same compute node
+            accept();
+            DPRINTF(DistEthernet, "Next connection, waiting for link info\n");
+            if (!recvTCP(sock, &ni, sizeof(ni)))
+                panic("Failed to receive link info");
+            assert(ni.rank == cur_rank);
+            assert(ni.distIfaceId == cur_id);
+        }
+        inform("Link okay  (iface:%d -> (node:%d, iface:%d))",
+               distIfaceId, ni.rank, ni.distIfaceId);
+        if (ni.distIfaceId < ni.distIfaceNum - 1) {
+            cur_id++;
+        } else {
+            cur_rank++;
+            cur_id = 0;
+        }
+        // send ack
+        ni.distIfaceId = distIfaceId;
+        ni.distIfaceNum = distIfaceNum;
+        sendTCP(sock, &ni, sizeof(ni));
+    } else { // this is not a switch
+        connect();
+        // send link info
+        ni.rank = rank;
+        ni.distIfaceId = distIfaceId;
+        ni.distIfaceNum = distIfaceNum;
+        sendTCP(sock, &ni, sizeof(ni));
+        DPRINTF(DistEthernet, "Connected, waiting for ack (distIfaceId:%d\n",
+                distIfaceId);
+        if (!recvTCP(sock, &ni, sizeof(ni)))
+            panic("Failed to receive ack");
+        assert(ni.rank == rank);
+        inform("Link okay  (iface:%d -> switch iface:%d)", distIfaceId,
+               ni.distIfaceId);
+    }
     sockRegistry.push_back(sock);
-    // let the server know who we are
-    sendTCP(sock, &multi_rank, sizeof(multi_rank));
+}
+
+void
+TCPIface::accept()
+{
+    struct sockaddr_in sockaddr;
+    socklen_t slen = sizeof (sockaddr);
+    sock = ::accept(fdStatic, (struct sockaddr *)&sockaddr, &slen);
+    if (sock != -1) {
+        int i = 1;
+        if (setsockopt(sock, IPPROTO_TCP, TCP_NODELAY, (char *)&i,
+                         sizeof(i)) < 0)
+            warn("ListenSocket(accept): setsockopt() TCP_NODELAY failed!");
+    }
+}
+
+void
+TCPIface::connect()
+{
+    struct addrinfo addr_hint, *addr_results;
+     int ret;
+
+     string port_str = to_string(serverPort);
+
+     sock = socket(PF_INET, SOCK_STREAM, IPPROTO_TCP);
+     panic_if(sock < 0, "socket() failed: %s", strerror(errno));
+
+     int fl = 1;
+     if (setsockopt(sock, IPPROTO_TCP, TCP_NODELAY, (char *)&fl, sizeof(fl)) < 0)
+         warn("ConnectSocket(connect): setsockopt() TCP_NODELAY failed!");
+
+     bzero(&addr_hint, sizeof(addr_hint));
+     addr_hint.ai_family = AF_INET;
+     addr_hint.ai_socktype = SOCK_STREAM;
+     addr_hint.ai_protocol = IPPROTO_TCP;
+
+     ret = getaddrinfo(serverName.c_str(), port_str.c_str(),
+                       &addr_hint, &addr_results);
+     panic_if(ret < 0, "getaddrinf() failed: %s", strerror(errno));
+
+     DPRINTF(DistEthernet, "Connecting to %s:%s\n",
+             serverName.c_str(), port_str.c_str());
+
+     ret = ::connect(sock, (struct sockaddr *)(addr_results->ai_addr),
+                     addr_results->ai_addrlen);
+     panic_if(ret < 0, "connect() failed: %s", strerror(errno));
+
+     freeaddrinfo(addr_results);
 }
 
 TCPIface::~TCPIface()
@@ -111,12 +260,20 @@ TCPIface::~TCPIface()
 }
 
 void
-TCPIface::sendTCP(int sock, void *buf, unsigned length)
+TCPIface::sendTCP(int sock, const void *buf, unsigned length)
 {
     ssize_t ret;
 
     ret = ::send(sock, buf, length, MSG_NOSIGNAL);
-    panic_if(ret < 0, "send() failed: %s", strerror(errno));
+    if (ret < 0) {
+        if (errno == ECONNRESET || errno == EPIPE) {
+            inform("send(): %s", strerror(errno));
+            exit_message("info", 0, "Message server closed connection, "
+                         "simulation is exiting");
+        } else {
+            panic("send() failed: %s", strerror(errno));
+        }
+    }
     panic_if(ret != length, "send() failed");
 }
 
@@ -140,19 +297,47 @@ TCPIface::recvTCP(int sock, void *buf, unsigned length)
 }
 
 void
-TCPIface::syncRaw(MultiHeaderPkt::MsgType sync_req, Tick sync_tick)
+TCPIface::sendPacket(const Header &header, const EthPacketPtr &packet)
+{
+    sendTCP(sock, &header, sizeof(header));
+    sendTCP(sock, packet->data, packet->length);
+}
+
+void
+TCPIface::sendCmd(const Header &header)
 {
-    /*
-     * Barrier is simply implemented by point-to-point messages to the server
-     * for now. This method is called by only one TCPIface object.
-     * The server will send back an 'ack' message when it gets the
-     * sync request from all clients.
-     */
-    MultiHeaderPkt::Header header_pkt;
-    header_pkt.msgType = sync_req;
-    header_pkt.sendTick = sync_tick;
-
-    for (auto s : sockRegistry)
-        sendTCP(s, (void *)&header_pkt, sizeof(header_pkt));
+    DPRINTF(DistEthernetCmd, "TCPIface::sendCmd() type: %d\n",
+            static_cast<int>(header.msgType));
+    // Global commands (i.e. sync request) are always sent by the master
+    // DistIface. The transfer method is simply implemented as point-to-point
+    // messages for now
+    for (auto s: sockRegistry)
+        sendTCP(s, (void*)&header, sizeof(header));
 }
 
+bool
+TCPIface::recvHeader(Header &header)
+{
+    bool ret = recvTCP(sock, &header, sizeof(header));
+    DPRINTF(DistEthernetCmd, "TCPIface::recvHeader() type: %d ret: %d\n",
+            static_cast<int>(header.msgType), ret);
+    return ret;
+}
+
+void
+TCPIface::recvPacket(const Header &header, EthPacketPtr &packet)
+{
+    packet = make_shared<EthPacketData>(header.dataPacketLength);
+    bool ret = recvTCP(sock, packet->data, header.dataPacketLength);
+    panic_if(!ret, "Error while reading socket");
+    packet->length = header.dataPacketLength;
+}
+
+void
+TCPIface::initTransport()
+{
+    // We cannot setup the conections in the constructor because the number
+    // of dist interfaces (per process) is unknown until the (simobject) init
+    // phase. That information is necessary for global connection ordering.
+    establishConnection();
+}
diff --git a/src/dev/net/tcp_iface.hh b/src/dev/net/tcp_iface.hh
index 2eb2c1c07..97ae9cde0 100644
--- a/src/dev/net/tcp_iface.hh
+++ b/src/dev/net/tcp_iface.hh
@@ -35,17 +35,17 @@
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  *
  * Authors: Gabor Dozsa
+ *          Mohammad Alian
  */
 
 /* @file
- * TCP stream socket based interface class for multi gem5 runs.
+ * TCP stream socket based interface class for dist-gem5 runs.
  *
- * For a high level description about multi gem5 see comments in
- * header file multi_iface.hh.
+ * For a high level description about dist-gem5 see comments in
+ * header file dist_iface.hh.
  *
- * The TCP subclass of MultiIface uses a separate server process
- * (see tcp_server.[hh,cc] under directory gem5/util/multi). Each gem5
- * process connects to the server via a stream socket. The server process
+ * Each gem5 process connects to the server (another gem5 process which
+ * simulates a switch box) via a stream socket. The server process
  * transfers messages and co-ordinates the synchronisation among the gem5
  * peers.
  */
@@ -55,11 +55,11 @@
 
 #include <string>
 
-#include "dev/net/multi_iface.hh"
+#include "dev/net/dist_iface.hh"
 
 class EventManager;
 
-class TCPIface : public MultiIface
+class TCPIface : public DistIface
 {
   private:
     /**
@@ -67,8 +67,28 @@ class TCPIface : public MultiIface
      */
     int sock;
 
+    std::string serverName;
+    int serverPort;
+
+    bool isSwitch;
+
+    bool listening;
+    static bool anyListening;
+    static int fdStatic;
+
+    /**
+     * Compute node info and storage for the very first connection from each
+     * node (used by the switch)
+     */
+    struct NodeInfo
+    {
+        unsigned rank;
+        unsigned distIfaceId;
+        unsigned distIfaceNum;
+    };
+    static std::vector<std::pair<NodeInfo, int> > nodes;
     /**
-     * Registry for all sockets to the server opened by this gem5 process.
+     * Storage for all opened sockets
      */
     static std::vector<int> sockRegistry;
 
@@ -82,7 +102,7 @@ class TCPIface : public MultiIface
      * @param length Size of the message in bytes.
      */
     void
-    sendTCP(int sock, void *buf, unsigned length);
+    sendTCP(int sock, const void *buf, unsigned length);
 
     /**
      * Receive the next incoming message through a TCP stream socket.
@@ -92,24 +112,26 @@ class TCPIface : public MultiIface
      * @param length Exact size of the expected message in bytes.
      */
     bool recvTCP(int sock, void *buf, unsigned length);
-
+    bool listen(int port);
+    void accept();
+    void connect();
+    int getfdStatic() const { return fdStatic; }
+    bool islistening() const { return listening; }
+    bool anyislistening() const { return anyListening; }
+    void establishConnection();
 
   protected:
 
-    virtual void
-    sendRaw(void *buf, unsigned length,
-            const MultiHeaderPkt::AddressType dest_addr=nullptr) override
-    {
-        sendTCP(sock, buf, length);
-    }
+    void sendPacket(const Header &header,
+                    const EthPacketPtr &packet) override;
 
-    virtual bool recvRaw(void *buf, unsigned length) override
-    {
-        return recvTCP(sock, buf, length);
-    }
+    void sendCmd(const Header &header) override;
+
+    bool recvHeader(Header &header) override;
+
+    void recvPacket(const Header &header, EthPacketPtr &packet) override;
 
-    virtual void syncRaw(MultiHeaderPkt::MsgType sync_req,
-                         Tick sync_tick) override;
+    void initTransport() override;
 
   public:
     /**
@@ -118,14 +140,15 @@ class TCPIface : public MultiIface
      * server process.
      * @param server_port The port number the server listening for new
      * connections.
-     * @param sync_start The tick for the first multi synchronisation.
-     * @param sync_repeat The frequency of multi synchronisation.
+     * @param sync_start The tick for the first dist synchronisation.
+     * @param sync_repeat The frequency of dist synchronisation.
      * @param em The EventManager object associated with the simulated
      * Ethernet link.
      */
     TCPIface(std::string server_name, unsigned server_port,
-             unsigned multi_rank, Tick sync_start, Tick sync_repeat,
-             EventManager *em);
+             unsigned dist_rank, unsigned dist_size,
+             Tick sync_start, Tick sync_repeat, EventManager *em,
+             bool is_switch, int num_nodes);
 
     ~TCPIface() override;
 };
diff --git a/src/sim/global_event.hh b/src/sim/global_event.hh
index 88981b52a..1aab4a233 100644
--- a/src/sim/global_event.hh
+++ b/src/sim/global_event.hh
@@ -219,7 +219,7 @@ class GlobalSyncEvent : public BaseGlobalEventTemplate<GlobalSyncEvent>
     };
 
     GlobalSyncEvent(Priority p, Flags f)
-        : Base(p, f)
+        : Base(p, f), repeat(0)
     { }
 
     GlobalSyncEvent(Tick when, Tick _repeat, Priority p, Flags f)
diff --git a/src/dev/net/multi_packet.cc b/src/sim/initparam_keys.hh
index 85f76b0c4..3ea68ddfe 100644
--- a/src/dev/net/multi_packet.cc
+++ b/src/sim/initparam_keys.hh
@@ -38,63 +38,33 @@
  */
 
 /* @file
- * MultiHeaderPkt class to encapsulate multi-gem5 header packets
- *
+ * Magic key definitions for the InitParam pseudo inst
  */
+#ifndef ___SIM_INITPARAM_KEYS_HH__
+#define ___SIM_INITPARAM_KEYS_HH__
 
-#include "dev/net/multi_packet.hh"
-
-#include <cstdint>
-#include <cstring>
-
-#include "base/inet.hh"
-
-unsigned
-MultiHeaderPkt::maxAddressLength()
-{
-    return sizeof(AddressType);
-}
-
-void
-MultiHeaderPkt::clearAddress(AddressType &addr)
-{
-    std::memset(addr, 0, sizeof(addr));
-}
-
-bool
-MultiHeaderPkt::isAddressEqual(const AddressType &addr1,
-                               const AddressType &addr2)
-{
-    return (std::memcmp(addr1, addr2, sizeof(addr1)) == 0);
-}
-
-bool
-MultiHeaderPkt::isAddressLess(const AddressType &addr1,
-                              const AddressType &addr2)
-{
-    return (std::memcmp(addr1, addr2, sizeof(addr1)) < 0);
-}
-
-void
-MultiHeaderPkt::copyAddress(AddressType &dest, const AddressType &src)
-{
-    std::memcpy(dest, src, sizeof(dest));
-}
-
-bool
-MultiHeaderPkt::isBroadcastAddress(const AddressType &addr)
-{
-    return ((Net::EthAddr *)&addr)->broadcast();
-}
-
-bool
-MultiHeaderPkt::isMulticastAddress(const AddressType &addr)
+namespace PseudoInst {
+/**
+ * Unique keys to retrieve various params by the initParam pseudo inst.
+ *
+ * @note Each key must be shorter than 16 characters (because we use
+ * two 64-bit registers two pass in the key to the initparam function)
+ */
+struct InitParamKey
 {
-    return ((Net::EthAddr *)&addr)->multicast();
-}
+    /**
+     *  The default key (empty string)
+     */
+    static constexpr const char *DEFAULT = "";
+    /**
+     *  Unique key for "rank" param (distributed gem5 runs)
+     */
+    static constexpr const char *DIST_RANK = "dist-rank";
+    /**
+     *  Unique key for "size" param (distributed gem5 runs)
+     */
+    static constexpr const char *DIST_SIZE = "dist-size";
+};
+} // namespace PseudoInst
 
-bool
-MultiHeaderPkt::isUnicastAddress(const AddressType &addr)
-{
-    return ((Net::EthAddr *)&addr)->unicast();
-}
+#endif
diff --git a/src/sim/pseudo_inst.cc b/src/sim/pseudo_inst.cc
index 0f7de0c3a..67c47ce77 100644
--- a/src/sim/pseudo_inst.cc
+++ b/src/sim/pseudo_inst.cc
@@ -63,8 +63,10 @@
 #include "debug/PseudoInst.hh"
 #include "debug/Quiesce.hh"
 #include "debug/WorkItems.hh"
+#include "dev/net/dist_iface.hh"
 #include "params/BaseCPU.hh"
 #include "sim/full_system.hh"
+#include "sim/initparam_keys.hh"
 #include "sim/process.hh"
 #include "sim/pseudo_inst.hh"
 #include "sim/serialize.hh"
@@ -357,8 +359,10 @@ void
 m5exit(ThreadContext *tc, Tick delay)
 {
     DPRINTF(PseudoInst, "PseudoInst::m5exit(%i)\n", delay);
-    Tick when = curTick() + delay * SimClock::Int::ns;
-    exitSimLoop("m5_exit instruction encountered", 0, when, 0, true);
+    if (DistIface::readyToExit(delay)) {
+        Tick when = curTick() + delay * SimClock::Int::ns;
+        exitSimLoop("m5_exit instruction encountered", 0, when, 0, true);
+    }
 }
 
 void
@@ -471,10 +475,14 @@ initParam(ThreadContext *tc, uint64_t key_str1, uint64_t key_str2)
     // Compare the key parameter with the known values to select the return
     // value
     uint64_t val;
-    if (strlen(key_str) == 0) {
+    if (strcmp(key_str, InitParamKey::DEFAULT) == 0) {
         val = tc->getCpuPtr()->system->init_param;
+    } else if (strcmp(key_str, InitParamKey::DIST_RANK) == 0) {
+        val = DistIface::rankParam();
+    } else if (strcmp(key_str, InitParamKey::DIST_SIZE) == 0) {
+        val = DistIface::sizeParam();
     } else {
-        panic("Unknown key for initparam pseudo instruction");
+        panic("Unknown key for initparam pseudo instruction:\"%s\"", key_str);
     }
     return val;
 }
@@ -529,10 +537,11 @@ m5checkpoint(ThreadContext *tc, Tick delay, Tick period)
     if (!tc->getCpuPtr()->params()->do_checkpoint_insts)
         return;
 
-    Tick when = curTick() + delay * SimClock::Int::ns;
-    Tick repeat = period * SimClock::Int::ns;
-
-    exitSimLoop("checkpoint", 0, when, repeat);
+    if (DistIface::readyToCkpt(delay, period)) {
+        Tick when = curTick() + delay * SimClock::Int::ns;
+        Tick repeat = period * SimClock::Int::ns;
+        exitSimLoop("checkpoint", 0, when, repeat);
+    }
 }
 
 uint64_t
diff --git a/util/multi/Makefile b/util/multi/Makefile
deleted file mode 100644
index a58dd3307..000000000
--- a/util/multi/Makefile
+++ /dev/null
@@ -1,63 +0,0 @@
-#
-# Copyright (c) 2015 ARM Limited
-# All rights reserved
-#
-# The license below extends only to copyright in the software and shall
-# not be construed as granting a license to any other intellectual
-# property including but not limited to intellectual property relating
-# to a hardware implementation of the functionality of the software
-# licensed hereunder.  You may use the software subject to the license
-# terms below provided that you ensure that this notice is replicated
-# unmodified and in its entirety in all distributions of the software,
-# modified or unmodified, in source code or in binary form.
-#
-# Redistribution and use in source and binary forms, with or without
-# modification, are permitted provided that the following conditions are
-# met: redistributions of source code must retain the above copyright
-# notice, this list of conditions and the following disclaimer;
-# redistributions in binary form must reproduce the above copyright
-# notice, this list of conditions and the following disclaimer in the
-# documentation and/or other materials provided with the distribution;
-# neither the name of the copyright holders nor the names of its
-# contributors may be used to endorse or promote products derived from
-# this software without specific prior written permission.
-#
-# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
-# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
-# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
-# A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
-# OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
-# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
-# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
-# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
-# THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
-# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
-# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
-#
-# Authors: Gabor Dozsa
-
-CXX= g++
-
-DEBUG= -DDEBUG
-
-M5_ARCH?= ARM
-M5_DIR?= ../..
-
-vpath % $(M5_DIR)/build/$(M5_ARCH)/dev
-
-INCDIRS= -I. -I$(M5_DIR)/build/$(M5_ARCH) -I$(M5_DIR)/ext
-CCFLAGS= -g -Wall -O3 $(DEBUG) -std=c++11 -MMD $(INCDIRS)
-
-default: tcp_server
-
-clean:
-	@rm -f tcp_server *.o *.d *~
-
-tcp_server: tcp_server.o multi_packet.o
-	$(CXX) $(LFLAGS) -o $@ $^
-
-%.o: %.cc
-	@echo '$(CXX) $(CCFLAGS) -c $(notdir $<) -o $@'
-	@$(CXX) $(CCFLAGS) -c $< -o $@
-
--include *.d
diff --git a/util/multi/tcp_server.cc b/util/multi/tcp_server.cc
deleted file mode 100644
index 1ec4303d3..000000000
--- a/util/multi/tcp_server.cc
+++ /dev/null
@@ -1,463 +0,0 @@
-/*
- * Copyright (c) 2015 ARM Limited
- * All rights reserved
- *
- * The license below extends only to copyright in the software and shall
- * not be construed as granting a license to any other intellectual
- * property including but not limited to intellectual property relating
- * to a hardware implementation of the functionality of the software
- * licensed hereunder.  You may use the software subject to the license
- * terms below provided that you ensure that this notice is replicated
- * unmodified and in its entirety in all distributions of the software,
- * modified or unmodified, in source code or in binary form.
- *
- * Copyright (c) 2008 The Regents of The University of Michigan
- * All rights reserved.
- *
- * Redistribution and use in source and binary forms, with or without
- * modification, are permitted provided that the following conditions are
- * met: redistributions of source code must retain the above copyright
- * notice, this list of conditions and the following disclaimer;
- * redistributions in binary form must reproduce the above copyright
- * notice, this list of conditions and the following disclaimer in the
- * documentation and/or other materials provided with the distribution;
- * neither the name of the copyright holders nor the names of its
- * contributors may be used to endorse or promote products derived from
- * this software without specific prior written permission.
- *
- * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
- * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
- * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
- * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
- * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
- * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
- * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
- * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
- * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
- * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
- * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
- *
- * Authors: Gabor Dozsa
- */
-
-
-/* @file
- *  Message server implementation using TCP stream sockets for parallel gem5
- * runs.
- */
-#include <arpa/inet.h>
-#include <sys/socket.h>
-#include <sys/types.h>
-#include <unistd.h>
-
-#include <cstdio>
-#include <cstdlib>
-
-#include "tcp_server.hh"
-
-using namespace std;
-
-// Some basic macros for information and error reporting.
-#define PRINTF(...) fprintf(stderr, __VA_ARGS__)
-
-#ifdef DEBUG
-static bool debugSetup = true;
-static bool debugPeriodic = false;
-static bool debugSync = true;
-static bool debugPkt = false;
-#define DPRINTF(v,...) if (v) PRINTF(__VA_ARGS__)
-#else
-#define DPRINTF(v,...)
-#endif
-
-#define inform(...) do { PRINTF("info: ");      \
-        PRINTF(__VA_ARGS__); } while(0)
-
-#define panic(...)  do { PRINTF("panic: ");     \
-        PRINTF(__VA_ARGS__);                    \
-        PRINTF("\n[%s:%s], line %d\n",          \
-               __FUNCTION__, __FILE__, __LINE__); \
-        exit(-1); } while(0)
-
-TCPServer *TCPServer::instance = nullptr;
-
-TCPServer::Channel::Channel() : fd(-1), isAlive(false), state(SyncState::idle)
-{
-    MultiHeaderPkt::clearAddress(address);
-}
-
-unsigned
-TCPServer::Channel::recvRaw(void *buf, unsigned size) const
-{
-    ssize_t n;
-    // This is a blocking receive.
-    n = recv(fd, buf, size, MSG_WAITALL);
-
-    if (n < 0)
-        panic("read() failed:%s", strerror(errno));
-    else if (n > 0 && n < size)
-        // the recv() call should wait for the full message
-        panic("read() failed");
-
-    return n;
-}
-
-void
-TCPServer::Channel::sendRaw(const void *buf, unsigned size) const
-{
-    ssize_t n;
-    n = send(fd, buf, size, MSG_NOSIGNAL);
-    if (n < 0)
-        panic("write() failed:%s", strerror(errno));
-    else if (n != size)
-        panic("write() failed");
-}
-
-void TCPServer::Channel::updateAddress(const AddressType &new_address)
-{
-    // check if the known address has changed (e.g. the client reconfigured
-    // its Ethernet NIC)
-    if (MultiHeaderPkt::isAddressEqual(address, new_address))
-        return;
-
-    // So we have to update the address. Note that we always
-    // store the same address as key in the map but the ordering
-    // may change so we need to erase and re-insert it again.
-    auto info = TCPServer::instance->addressMap.find(&address);
-    if (info != TCPServer::instance->addressMap.end()) {
-        TCPServer::instance->addressMap.erase(info);
-    }
-
-    MultiHeaderPkt::copyAddress(address, new_address);
-    TCPServer::instance->addressMap[&address] = this;
-}
-
-void
-TCPServer::Channel::headerPktIn()
-{
-    ssize_t n;
-    Header hdr_pkt;
-
-    n = recvRaw(&hdr_pkt, sizeof(hdr_pkt));
-
-    if (n == 0) {
-        // EOF - nothing to do here, we will handle this as a POLLRDHUP event
-        // in the main loop.
-        return;
-    }
-
-    if (hdr_pkt.msgType == MsgType::dataDescriptor) {
-        updateAddress(hdr_pkt.srcAddress);
-        TCPServer::instance->xferData(hdr_pkt, *this);
-    } else {
-        processCmd(hdr_pkt.msgType, hdr_pkt.sendTick);
-    }
-}
-
-void TCPServer::Channel::processCmd(MsgType cmd, Tick send_tick)
-{
-    switch (cmd) {
-      case MsgType::cmdAtomicSyncReq:
-        DPRINTF(debugSync,"Atomic sync request (rank:%d)\n",rank);
-        assert(state == SyncState::idle);
-        state = SyncState::atomic;
-        TCPServer::instance->syncTryComplete(SyncState::atomic,
-                                             MsgType::cmdAtomicSyncAck);
-        break;
-      case MsgType::cmdPeriodicSyncReq:
-        DPRINTF(debugPeriodic,"PERIODIC sync request (at %ld)\n",send_tick);
-        // sanity check
-        if (TCPServer::instance->periodicSyncTick() == 0) {
-            TCPServer::instance->periodicSyncTick(send_tick);
-        } else if ( TCPServer::instance->periodicSyncTick() != send_tick) {
-            panic("Out of order periodic sync request - rank:%d "
-                  "(send_tick:%ld ongoing:%ld)", rank, send_tick,
-                  TCPServer::instance->periodicSyncTick());
-        }
-        switch (state) {
-          case SyncState::idle:
-            state = SyncState::periodic;
-            TCPServer::instance->syncTryComplete(SyncState::periodic,
-                                                 MsgType::cmdPeriodicSyncAck);
-            break;
-          case SyncState::asyncCkpt:
-            // An async ckpt request has already been sent to this client and
-            // that will interrupt this periodic sync. We can simply drop this
-            // message.
-            break;
-          default:
-            panic("Unexpected state for periodic sync request (rank:%d)",
-                rank);
-            break;
-        }
-        break;
-      case MsgType::cmdCkptSyncReq:
-        DPRINTF(debugSync, "CKPT sync request (rank:%d)\n",rank);
-        switch (state) {
-          case SyncState::idle:
-            TCPServer::instance->ckptPropagate(*this);
-            // we fall through here to complete #clients==1 case
-          case SyncState::asyncCkpt:
-            state = SyncState::ckpt;
-            TCPServer::instance->syncTryComplete(SyncState::ckpt,
-                                                 MsgType::cmdCkptSyncAck);
-            break;
-          default:
-            panic("Unexpected state for ckpt sync request (rank:%d)", rank);
-            break;
-        }
-        break;
-      default:
-        panic("Unexpected header packet (rank:%d)",rank);
-        break;
-    }
-}
-
-TCPServer::TCPServer(unsigned clients_num,
-                     unsigned listen_port,
-                     int timeout_in_sec)
-{
-    assert(instance == nullptr);
-    construct(clients_num, listen_port, timeout_in_sec);
-    instance = this;
-}
-
-TCPServer::~TCPServer()
-{
-    for (auto &c : clientsPollFd)
-        close(c.fd);
-}
-
-void
-TCPServer::construct(unsigned clients_num, unsigned port, int timeout_in_sec)
-{
-    int listen_sock, new_sock, ret;
-    unsigned client_len;
-    struct sockaddr_in server_addr, client_addr;
-    struct pollfd new_pollfd;
-    Channel new_channel;
-
-    DPRINTF(debugSetup, "Start listening on port %u ...\n", port);
-
-    listen_sock = socket(AF_INET, SOCK_STREAM, 0);
-    if (listen_sock < 0)
-        panic("socket() failed:%s", strerror(errno));
-
-    bzero(&server_addr, sizeof(server_addr));
-    server_addr.sin_family = AF_INET;
-    server_addr.sin_addr.s_addr = INADDR_ANY;
-    server_addr.sin_port = htons(port);
-    if (bind(listen_sock, (struct sockaddr *) &server_addr,
-             sizeof(server_addr)) < 0)
-        panic("bind() failed:%s", strerror(errno));
-    listen(listen_sock, 10);
-
-    clientsPollFd.reserve(clients_num);
-    clientsChannel.reserve(clients_num);
-
-    new_pollfd.events = POLLIN | POLLRDHUP;
-    new_pollfd.revents = 0;
-    while (clientsPollFd.size() < clients_num) {
-        new_pollfd.fd = listen_sock;
-        ret = poll(&new_pollfd, 1, timeout_in_sec*1000);
-        if (ret == 0)
-            panic("Timeout while waiting for clients to connect");
-        assert(ret == 1 && new_pollfd.revents == POLLIN);
-        client_len = sizeof(client_addr);
-        new_sock = accept(listen_sock,
-                          (struct sockaddr *) &client_addr,
-                          &client_len);
-        if (new_sock < 0)
-            panic("accept() failed:%s", strerror(errno));
-        new_pollfd.fd = new_sock;
-        new_pollfd.revents = 0;
-        clientsPollFd.push_back(new_pollfd);
-        new_channel.fd = new_sock;
-        new_channel.isAlive = true;
-        new_channel.recvRaw(&new_channel.rank, sizeof(new_channel.rank));
-        clientsChannel.push_back(new_channel);
-
-        DPRINTF(debugSetup, "New client connection addr:%u port:%hu rank:%d\n",
-                client_addr.sin_addr.s_addr, client_addr.sin_port,
-                new_channel.rank);
-    }
-    ret = close(listen_sock);
-    assert(ret == 0);
-
-    DPRINTF(debugSetup, "Setup complete\n");
-}
-
-void
-TCPServer::run()
-{
-    int nfd;
-    unsigned num_active_clients = clientsPollFd.size();
-
-    DPRINTF(debugSetup, "Entering run() loop\n");
-    while (num_active_clients ==  clientsPollFd.size()) {
-        nfd = poll(&clientsPollFd[0], clientsPollFd.size(), -1);
-        if (nfd == -1)
-            panic("poll() failed:%s", strerror(errno));
-
-        for (unsigned i = 0, n = 0;
-             i < clientsPollFd.size() && (signed)n < nfd;
-             i++) {
-            struct pollfd &pfd = clientsPollFd[i];
-            if (pfd.revents) {
-                if (pfd.revents & POLLERR)
-                    panic("poll() returned POLLERR");
-                if (pfd.revents & POLLIN) {
-                    clientsChannel[i].headerPktIn();
-                }
-                if (pfd.revents & POLLRDHUP) {
-                    // One gem5 process exited or aborted. Either way, we
-                    // assume the full simulation should stop now (either
-                    // because m5 exit was called or a serious error
-                    // occurred.) So we quit the run loop here and close all
-                    // sockets to notify the remaining peer gem5 processes.
-                    pfd.events = 0;
-                    clientsChannel[i].isAlive = false;
-                    num_active_clients--;
-                    DPRINTF(debugSetup, "POLLRDHUP event");
-                }
-                n++;
-                if ((signed)n == nfd)
-                    break;
-            }
-        }
-    }
-    DPRINTF(debugSetup, "Exiting run() loop\n");
-}
-
-void
-TCPServer::xferData(const Header &hdr_pkt, const Channel &src)
-{
-    unsigned n;
-    assert(hdr_pkt.dataPacketLength <= sizeof(packetBuffer));
-    n = src.recvRaw(packetBuffer, hdr_pkt.dataPacketLength);
-
-    if (n == 0)
-        panic("recvRaw() failed");
-    DPRINTF(debugPkt, "Incoming data packet (from rank %d) "
-            "src:0x%02x%02x%02x%02x%02x%02x "
-            "dst:0x%02x%02x%02x%02x%02x%02x\n",
-            src.rank,
-            hdr_pkt.srcAddress[0],
-            hdr_pkt.srcAddress[1],
-            hdr_pkt.srcAddress[2],
-            hdr_pkt.srcAddress[3],
-            hdr_pkt.srcAddress[4],
-            hdr_pkt.srcAddress[5],
-            hdr_pkt.dstAddress[0],
-            hdr_pkt.dstAddress[1],
-            hdr_pkt.dstAddress[2],
-            hdr_pkt.dstAddress[3],
-            hdr_pkt.dstAddress[4],
-            hdr_pkt.dstAddress[5]);
-    // Now try to figure out the destination client(s).
-    auto dst_info = addressMap.find(&hdr_pkt.dstAddress);
-
-    // First handle the multicast/broadcast or unknonw destination case. These
-    // all trigger a broadcast of the packet to all clients.
-    if (MultiHeaderPkt::isUnicastAddress(hdr_pkt.dstAddress) == false ||
-        dst_info == addressMap.end()) {
-        unsigned n = 0;
-        for (auto const &c: clientsChannel) {
-            if (c.isAlive && &c!=&src) {
-                c.sendRaw(&hdr_pkt, sizeof(hdr_pkt));
-                c.sendRaw(packetBuffer, hdr_pkt.dataPacketLength);
-                n++;
-            }
-        }
-        if (n == 0) {
-            inform("Broadcast/multicast packet dropped\n");
-        }
-    } else {
-        // It is a unicast address with a known destination
-        Channel *dst = dst_info->second;
-        if (dst->isAlive) {
-            dst->sendRaw(&hdr_pkt, sizeof(hdr_pkt));
-            dst->sendRaw(packetBuffer, hdr_pkt.dataPacketLength);
-            DPRINTF(debugPkt, "Unicast packet sent (to rank %d)\n",dst->rank);
-        } else {
-            inform("Unicast packet dropped (destination exited)\n");
-        }
-    }
-}
-
-void
-TCPServer::syncTryComplete(SyncState st, MsgType ack)
-{
-    // Check if the barrieris complete. If so then notify all the clients.
-    for (auto &c : clientsChannel) {
-        if (c.isAlive && (c.state != st)) {
-            // sync not complete yet, stop here
-            return;
-        }
-    }
-    // Sync complete, send out the acks
-    MultiHeaderPkt::Header hdr_pkt;
-    hdr_pkt.msgType = ack;
-    for (auto &c : clientsChannel) {
-        if (c.isAlive) {
-            c.sendRaw(&hdr_pkt, sizeof(hdr_pkt));
-            c.state = SyncState::idle;
-        }
-    }
-    // Reset periodic send tick
-    _periodicSyncTick = 0;
-    DPRINTF(st == SyncState::periodic ? debugPeriodic : debugSync,
-            "Sync COMPLETE\n");
-}
-
-void
-TCPServer::ckptPropagate(Channel &ch)
-{
-    // Channel ch got a ckpt request that needs to be propagated to the other
-    // clients
-    MultiHeaderPkt::Header hdr_pkt;
-    hdr_pkt.msgType = MsgType::cmdCkptSyncReq;
-    for (auto &c : clientsChannel) {
-        if (c.isAlive && (&c != &ch)) {
-            switch (c.state) {
-              case SyncState::idle:
-              case SyncState::periodic:
-                c.sendRaw(&hdr_pkt, sizeof(hdr_pkt));
-                c.state = SyncState::asyncCkpt;
-                break;
-              default:
-                panic("Unexpected state for ckpt sync request propagation "
-                      "(rank:%d)\n",c.rank);
-                break;
-            }
-        }
-    }
-}
-
-int main(int argc, char *argv[])
-{
-    TCPServer *server;
-    int clients_num = -1, listen_port = -1;
-    int first_arg = 1, timeout_in_sec = 60;
-
-    if (argc > 1 && string(argv[1]).compare("-debug") == 0) {
-        timeout_in_sec = -1;
-        first_arg++;
-        argc--;
-    }
-
-    if (argc != 3)
-        panic("We need two command line args (number of clients and tcp listen"
-              " port");
-
-    clients_num = atoi(argv[first_arg]);
-    listen_port = atoi(argv[first_arg + 1]);
-
-    server = new TCPServer(clients_num, listen_port, timeout_in_sec);
-
-    server->run();
-
-    delete server;
-
-    return 0;
-}
diff --git a/util/multi/tcp_server.hh b/util/multi/tcp_server.hh
deleted file mode 100644
index c5f2a9ce8..000000000
--- a/util/multi/tcp_server.hh
+++ /dev/null
@@ -1,254 +0,0 @@
-/*
- * Copyright (c) 2015 ARM Limited
- * All rights reserved
- *
- * The license below extends only to copyright in the software and shall
- * not be construed as granting a license to any other intellectual
- * property including but not limited to intellectual property relating
- * to a hardware implementation of the functionality of the software
- * licensed hereunder.  You may use the software subject to the license
- * terms below provided that you ensure that this notice is replicated
- * unmodified and in its entirety in all distributions of the software,
- * modified or unmodified, in source code or in binary form.
- *
- * Copyright (c) 2008 The Regents of The University of Michigan
- * All rights reserved.
- *
- * Redistribution and use in source and binary forms, with or without
- * modification, are permitted provided that the following conditions are
- * met: redistributions of source code must retain the above copyright
- * notice, this list of conditions and the following disclaimer;
- * redistributions in binary form must reproduce the above copyright
- * notice, this list of conditions and the following disclaimer in the
- * documentation and/or other materials provided with the distribution;
- * neither the name of the copyright holders nor the names of its
- * contributors may be used to endorse or promote products derived from
- * this software without specific prior written permission.
- *
- * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
- * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
- * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
- * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
- * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
- * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
- * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
- * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
- * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
- * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
- * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
- *
- * Authors: Gabor Dozsa
- */
-
-/* @file
- *  Message server using TCP stream sockets for parallel gem5 runs.
- *
- * For a high level description about multi gem5 see comments in
- * header files src/dev/multi_iface.hh and src/dev/tcp_iface.hh.
- *
- * This file implements the central message server process for multi gem5.
- * The server is responsible the following tasks.
- * 1. Establishing a TCP socket connection for each gem5 process (clients).
- *
- * 2. Process data messages coming in from clients. The server checks
- * the MAC addresses in the header message and transfers the message
- * to the target(s) client(s).
- *
- * 3. Processing synchronisation related control messages. Synchronisation
- * is performed as follows. The server waits for a 'barrier enter' message
- * from all the clients. When the last such control message arrives, the
- * server sends out a 'barrier leave' control message to all the clients.
- *
- * 4. Triggers complete termination in case a client exits. A client may
- * exit either by calling 'm5 exit' pseudo instruction or due to a fatal
- * error. In either case, we assume that the entire multi simulation needs to
- * terminate. The server triggers full termination by tearing down the
- * open TCP sockets.
- *
- * The TCPServer class is instantiated as a singleton object.
- *
- * The server can be built independently from the rest of gem5 (and it is
- * architecture agnostic). See the Makefile in the same directory.
- *
- */
-
-#include <poll.h>
-
-#include <map>
-#include <vector>
-
-#include "dev/etherpkt.hh"
-#include "dev/multi_packet.hh"
-
-/**
- * The maximum length of an Ethernet packet (allowing Jumbo frames).
- */
-#define MAX_ETH_PACKET_LENGTH 9014
-
-class TCPServer
-{
-  public:
-    typedef MultiHeaderPkt::AddressType AddressType;
-    typedef MultiHeaderPkt::Header Header;
-    typedef MultiHeaderPkt::MsgType MsgType;
-
-  private:
-
-    enum
-    class SyncState { periodic, ckpt, asyncCkpt, atomic, idle };
-    /**
-     * The Channel class encapsulates all the information about a client
-     * and its current status.
-     */
-    class Channel
-    {
-      private:
-        /**
-         * The MAC address of the client.
-         */
-        AddressType address;
-
-        /**
-         * Update the client MAC address. It is called every time a new data
-         * packet is to come in.
-         */
-        void updateAddress(const AddressType &new_addr);
-        /**
-         * Process an incoming command message.
-         */
-        void processCmd(MultiHeaderPkt::MsgType cmd, Tick send_tick);
-
-
-      public:
-        /**
-         * TCP stream socket.
-         */
-        int fd;
-        /**
-         * Is client connected?
-         */
-        bool isAlive;
-        /**
-         * Current state of the channel wrt. multi synchronisation.
-         */
-        SyncState state;
-        /**
-         * Multi rank of the client
-         */
-        unsigned rank;
-
-      public:
-        Channel();
-        ~Channel () {}
-
-
-        /**
-         * Receive and process the next incoming header packet.
-         */
-        void headerPktIn();
-        /**
-         * Send raw data to the connected client.
-         *
-         * @param data The data to send.
-         * @param size Size of the data (in bytes).
-         */
-        void sendRaw(const void *data, unsigned size) const;
-        /**
-         * Receive raw data from the connected client.
-         *
-         * @param buf The buffer to store the incoming data into.
-         * @param size Size of data to receive (in bytes).
-         * @return In case of success, it returns size. Zero is returned
-         * if the socket is already closed by the client.
-         */
-        unsigned recvRaw(void *buf, unsigned size) const;
-    };
-
-    /**
-     * The array of socket descriptors needed by the poll() system call.
-     */
-    std::vector<struct pollfd> clientsPollFd;
-    /**
-     * Array holding all clients info.
-     */
-    std::vector<Channel> clientsChannel;
-
-
-    /**
-     * We use a map to select the target client based on the destination
-     * MAC address.
-     */
-    struct AddressCompare
-    {
-        bool operator()(const AddressType *a1, const AddressType *a2)
-        {
-            return MultiHeaderPkt::isAddressLess(*a1, *a2);
-        }
-    };
-    std::map<const AddressType *, Channel *, AddressCompare> addressMap;
-
-    /**
-     * As we dealt with only one message at a time, we can allocate and re-use
-     * a single packet buffer (to hold any incoming data packet).
-     */
-    uint8_t packetBuffer[MAX_ETH_PACKET_LENGTH];
-    /**
-     * Send tick of the current periodic sync. It is used for sanity check.
-     */
-    Tick _periodicSyncTick;
-    /**
-     * The singleton server object.
-     */
-    static TCPServer *instance;
-
-    /**
-     * Set up the socket connections to all the clients.
-     *
-     * @param listen_port The port we are listening on for new client
-     * connection requests.
-     * @param nclients The number of clients to connect to.
-     * @param timeout Timeout in sec to complete the setup phase
-     * (i.e. all gem5 establish socket connections)
-     */
-    void construct(unsigned listen_port, unsigned nclients, int timeout);
-    /**
-     * Transfer the header and the follow up data packet to the target(s)
-     * clients.
-     *
-     * @param hdr The header message structure.
-     * @param ch The source channel for the message.
-     */
-    void xferData(const Header &hdr, const Channel &ch);
-    /**
-     * Check if the current round of a synchronisation is completed and notify
-     * the clients if it is so.
-     *
-     * @param st The state all channels should have if sync is complete.
-     * @param ack The type of ack message to send out if the sync is compete.
-     */
-    void syncTryComplete(SyncState st, MultiHeaderPkt::MsgType ack);
-    /**
-     * Broadcast a request for checkpoint sync.
-     *
-     * @param ch The source channel of the checkpoint sync request.
-     */
-    void ckptPropagate(Channel &ch);
-    /**
-     * Setter for current periodic send tick.
-     */
-    void periodicSyncTick(Tick t) { _periodicSyncTick = t; }
-    /**
-     * Getter for current periodic send tick.
-     */
-    Tick periodicSyncTick() { return _periodicSyncTick; }
-
-  public:
-
-    TCPServer(unsigned clients_num, unsigned listen_port, int timeout_in_sec);
-    ~TCPServer();
-
-    /**
-     * The main server loop that waits for and processes incoming messages.
-     */
-    void run();
-};