tcp: MD5: Fix IPv6 signatures

Reported by Stefanos Harhalakis; although 2.6.27-rc1 talks to itself using IPv6
TCP MD5 packets just fine, Stefanos noted that tcpdump claimed that the
signatures were invalid.

I broke this in 49a72dfb8814c2d65bd9f8c9c6daf6395a1ec58d ("tcp: Fix MD5
signatures for non-linear skbs"), it was just a typo.

Note that tcpdump will still sometimes claim that the signatures are incorrect.
A patch to tcpdump has been submitted for this[1].

[1] http://tinyurl.com/6a4fl2

Signed-off-by: Adam Langley <agl@imperialviolet.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/ipv6/tcp_ipv6.c

@@ -748,7 +748,7 @@ static int tcp_v6_md5_hash_pseudoheader(struct tcp_md5sig_pool *hp,
 	ipv6_addr_copy(&bp->saddr, saddr);
 	ipv6_addr_copy(&bp->daddr, daddr);
 	bp->protocol = cpu_to_be32(IPPROTO_TCP);
-	bp->len = cpu_to_be16(nbytes);
+	bp->len = cpu_to_be32(nbytes);
 
 	sg_init_one(&sg, bp, sizeof(*bp));
 	return crypto_hash_update(&hp->md5_desc, &sg, sizeof(*bp));