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>

2 files changed, 3 insertions, 3 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;
 
diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c
index 424d9c4a67ac..e8b0fdd9edb8 100644
--- a/net/ipv6/tcp_ipv6.c
+++ b/net/ipv6/tcp_ipv6.c
@@ -1012,14 +1012,14 @@ static void tcp_v6_send_reset(struct sock *sk, struct sk_buff *skb)
         }
 #endif
 
-        buff->csum = csum_partial((char *)t1, sizeof(*t1), 0);
+        buff->csum = csum_partial((char *)t1, tot_len, 0);
 
         memset(&fl, 0, sizeof(fl));
         ipv6_addr_copy(&fl.fl6_dst, &ipv6_hdr(skb)->saddr);
         ipv6_addr_copy(&fl.fl6_src, &ipv6_hdr(skb)->daddr);
 
         t1->check = csum_ipv6_magic(&fl.fl6_src, &fl.fl6_dst,
-                                    sizeof(*t1), IPPROTO_TCP,
+                                    tot_len, IPPROTO_TCP,
                                     buff->csum);
 
         fl.proto = IPPROTO_TCP;