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>

5 files changed, 15 insertions, 6 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)
diff --git a/net/core/sock.c b/net/core/sock.c
index 94c4affdda9b..63530a03b8c2 100644
--- a/net/core/sock.c
+++ b/net/core/sock.c
@@ -1231,6 +1231,7 @@ void sk_setup_caps(struct sock *sk, struct dst_entry *dst)
         sk->sk_route_caps = dst->dev->features;
         if (sk->sk_route_caps & NETIF_F_GSO)
                 sk->sk_route_caps |= NETIF_F_GSO_SOFTWARE;
+        sk->sk_route_caps &= ~sk->sk_route_nocaps;
         if (sk_can_gso(sk)) {
                 if (dst->header_len) {
                         sk->sk_route_caps &= ~NETIF_F_GSO_MASK;
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
 
diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index 5db3a2c6cb33..18a3302480cb 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -873,7 +873,7 @@ static int tcp_transmit_skb(struct sock *sk, struct sk_buff *skb, int clone_it,
 #ifdef CONFIG_TCP_MD5SIG
         /* Calculate the MD5 hash, as we have all we need now */
         if (md5) {
-                sk->sk_route_caps &= ~NETIF_F_GSO_MASK;
+                sk_nocaps_add(sk, NETIF_F_GSO_MASK);
                 tp->af_specific->calc_md5_hash(opts.hash_location,
                                                md5, sk, NULL, skb);
         }
diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c
index 6603511e3673..2b7c3a100e2c 100644
--- a/net/ipv6/tcp_ipv6.c
+++ b/net/ipv6/tcp_ipv6.c
@@ -604,7 +604,7 @@ static int tcp_v6_md5_do_add(struct sock *sk, struct in6_addr *peer,
                                 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);
@@ -741,7 +741,7 @@ static int tcp_v6_parse_md5_keys (struct sock *sk, char __user *optval,
                         return -ENOMEM;
 
                 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, GFP_KERNEL);