[PATCH] Fix sorting of SACK blocks

[Baruch Even <baruch@ev-en.org>]

The sorting of SACK blocks actually munges them rather than sort, causing the
TCP stack to ignore some SACK information and breaking the assumption of
ordered SACK blocks after sorting.

The sort takes the data from a second buffer which isn't moved causing
subsequent data moves to occur from the wrong location. The fix is to
use a temporary buffer as a normal sort does.

Signed-Off-By: Baruch Even <baruch@ev-en.org>

diff -X 2.6-rc6/Documentation/dontdiff -ur 2.6-rc6/net/ipv4/tcp_input.c 2.6-mod/net/ipv4/tcp_input.c
--- 2.6-rc6/net/ipv4/tcp_input.c	2007-01-25 19:04:20.000000000 +0200
+++ 2.6-mod/net/ipv4/tcp_input.c	2007-01-25 19:52:04.000000000 +0200
@@ -1011,10 +1011,11 @@
 			for (j = 0; j < i; j++){
 				if (after(ntohl(sp[j].start_seq),
 					  ntohl(sp[j+1].start_seq))){
-					sp[j].start_seq = htonl(tp->recv_sack_cache[j+1].start_seq);
-					sp[j].end_seq = htonl(tp->recv_sack_cache[j+1].end_seq);
-					sp[j+1].start_seq = htonl(tp->recv_sack_cache[j].start_seq);
-					sp[j+1].end_seq = htonl(tp->recv_sack_cache[j].end_seq);
+					struct tcp_sack_block_wire tmp;
+
+					tmp = sp[j];
+					sp[j] = sp[j+1];
+					sp[j+1] = tmp;
 				}
 
 			}