fix some bugs in the headers and fix checksumming.

base/inet.cc:
    we can't use a uint16_t for the intermediate checksum values
    since there may be some bits that carry.
    the length that is added in the pseudo header is the length of
    the tcp portion only.
base/inet.hh:
    silly me, the ip_hlen field is in terms of 4-byte words.
    when caclulating checksum, we're dealing with network byte order,
    so don't bother doing any byteswapping.

--HG--
extra : convert_revision : 993e3413e9febea0ba2fb6ba8bf04c053cca15ed

1 files changed, 8 insertions, 7 deletions

diff --git a/base/inet.cc b/base/inet.cc
index ac0758c1f..0b9e32854 100644
--- a/base/inet.cc
+++ b/base/inet.cc
@@ -46,16 +46,17 @@ eaddr_string(const uint8_t a[6])
 uint16_t
 IpHdr::ip_cksum() const
 {
-    uint16_t sum = ip_cksum_add(this, hlen(), 0);
-    return ip_cksum_carry(sum);
+    int sum = ip_cksum_add(this, hlen(), 0);
+    sum = ip_cksum_carry(sum);
+    return sum;
 }
 
 uint16_t
 IpHdr::tu_cksum() const
 {
-    uint16_t sum = ip_cksum_add(payload(), len() - hlen(), 0);
-    sum = ip_cksum_add(&ip_src, 4, sum);
-    sum = ip_cksum_add(&ip_dst, 4, sum);
-    sum += htons(ip_p + ip_len);
-    return ip_cksum_carry(sum);
+    int sum = ip_cksum_add(payload(), len() - hlen(), 0);
+    sum = ip_cksum_add(&ip_src, 8, sum); // source and destination
+    sum += htons(ip_p + len() - hlen());
+    sum = ip_cksum_carry(sum);
+    return sum;
 }