tcp: fix length used for checksum in a reset

While looking for some common code I came across difference
in checksum calculation between tcp_v6_send_(reset|ack) I
couldn't explain. I checked both v4 and v6 and found out that
both seem to have the same "feature". I couldn't find anything
in rfc nor anywhere else which would state that md5 option
should be ignored like it was in case of reset so I came to
a conclusion that this is probably a genuine bug. I suspect
that addition of md5 just was fooled by the excessive
copy-paste code in those functions and the reset part was
never tested well enough to find out the problem.

Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@helsinki.fi>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 1 insertions, 1 deletions

diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
index 24ffc5e1d3da..ba46769c6e97 100644
--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c
@@ -589,7 +589,7 @@ static void tcp_v4_send_reset(struct sock *sk, struct sk_buff *skb)
 #endif
         arg.csum = csum_tcpudp_nofold(ip_hdr(skb)->daddr,
                                       ip_hdr(skb)->saddr, /* XXX */
-                                      sizeof(struct tcphdr), IPPROTO_TCP, 0);
+                                      arg.iov[0].iov_len, IPPROTO_TCP, 0);
         arg.csumoffset = offsetof(struct tcphdr, check) / 2;
         arg.flags = (sk && inet_sk(sk)->transparent) ? IP_REPLY_ARG_NOSRCCHECK : 0;