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, 8 insertions, 0 deletions

diff --git a/include/net/sock.h b/include/net/sock.h
index 328e03f47dd1..aed16eb9db4b 100644
--- a/include/net/sock.h
+++ b/include/net/sock.h
@@ -177,6 +177,7 @@ struct sock_common {
   *                %SO_OOBINLINE settings, %SO_TIMESTAMPING settings
   *     @sk_no_check: %SO_NO_CHECK setting, wether or not checkup packets
   *     @sk_route_caps: route capabilities (e.g. %NETIF_F_TSO)
+  *     @sk_route_nocaps: forbidden route capabilities (e.g NETIF_F_GSO_MASK)
   *     @sk_gso_type: GSO type (e.g. %SKB_GSO_TCPV4)
   *     @sk_gso_max_size: Maximum GSO segment size to build
   *     @sk_lingertime: %SO_LINGER l_linger setting
@@ -276,6 +277,7 @@ struct sock {
         int                     sk_forward_alloc;
         gfp_t                   sk_allocation;
         int                     sk_route_caps;
+        int                     sk_route_nocaps;
         int                     sk_gso_type;
         unsigned int            sk_gso_max_size;
         int                     sk_rcvlowat;
@@ -1335,6 +1337,12 @@ static inline int sk_can_gso(const struct sock *sk)
 
 extern void sk_setup_caps(struct sock *sk, struct dst_entry *dst);
 
+static inline void sk_nocaps_add(struct sock *sk, int flags)
+{
+        sk->sk_route_nocaps |= flags;
+        sk->sk_route_caps &= ~flags;
+}
+
 static inline int skb_copy_to_page(struct sock *sk, char __user *from,
                                    struct sk_buff *skb, struct page *page,
                                    int off, int copy)