net: Introduce sk_route_nocaps

TCP-MD5 sessions have intermittent failures, when route cache is
invalidated. ip_queue_xmit() has to find a new route, calls
sk_setup_caps(sk, &rt->u.dst), destroying the 

sk->sk_route_caps &= ~NETIF_F_GSO_MASK

that MD5 desperately try to make all over its way (from
tcp_transmit_skb() for example)

So we send few bad packets, and everything is fine when
tcp_transmit_skb() is called again for this socket.

Since ip_queue_xmit() is at a lower level than TCP-MD5, I chose to use a
socket field, sk_route_nocaps, containing bits to mask on sk_route_caps.

Reported-by: Bhaskar Dutta <bhaskie@gmail.com>
Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 3 insertions, 3 deletions

diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
index 771f8146a2e5..202cf09c4cd4 100644
--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c
@@ -891,7 +891,7 @@ int tcp_v4_md5_do_add(struct sock *sk, __be32 addr,
                                 kfree(newkey);
                                 return -ENOMEM;
                         }
-                        sk->sk_route_caps &= ~NETIF_F_GSO_MASK;
+                        sk_nocaps_add(sk, NETIF_F_GSO_MASK);
                 }
                 if (tcp_alloc_md5sig_pool(sk) == NULL) {
                         kfree(newkey);
@@ -1021,7 +1021,7 @@ static int tcp_v4_parse_md5_keys(struct sock *sk, char __user *optval,
                         return -EINVAL;
 
                 tp->md5sig_info = p;
-                sk->sk_route_caps &= ~NETIF_F_GSO_MASK;
+                sk_nocaps_add(sk, NETIF_F_GSO_MASK);
         }
 
         newkey = kmemdup(cmd.tcpm_key, cmd.tcpm_keylen, sk->sk_allocation);
@@ -1462,7 +1462,7 @@ struct sock *tcp_v4_syn_recv_sock(struct sock *sk, struct sk_buff *skb,
                 if (newkey != NULL)
                         tcp_v4_md5_do_add(newsk, newinet->inet_daddr,
                                           newkey, key->keylen);
-                newsk->sk_route_caps &= ~NETIF_F_GSO_MASK;
+                sk_nocaps_add(newsk, NETIF_F_GSO_MASK);
         }
 #endif