ipv4: tcp: fix TOS value in ACK messages sent from TIME_WAIT

There is a long standing bug in linux tcp stack, about ACK messages sent
on behalf of TIME_WAIT sockets.

In the IP header of the ACK message, we choose to reflect TOS field of
incoming message, and this might break some setups.

Example of things that were broken :
  - Routing using TOS as a selector
  - Firewalls
  - Trafic classification / shaping

We now remember in timewait structure the inet tos field and use it in
ACK generation, and route lookup.

Notes :
 - We still reflect incoming TOS in RST messages.
 - We could extend MuraliRaja Muniraju patch to report TOS value in
netlink messages for TIME_WAIT sockets.
 - A patch is needed for IPv6

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/ip_output.c b/net/ipv4/ip_output.c
index e1374ab..0bc95f3 100644
--- a/net/ipv4/ip_output.c
+++ b/net/ipv4/ip_output.c
@@ -1466,7 +1466,7 @@ static int ip_reply_glue_bits(void *dptr, char *to, int offset,
  *     	structure to pass arguments.
  */
 void ip_send_reply(struct sock *sk, struct sk_buff *skb, __be32 daddr,
-		   struct ip_reply_arg *arg, unsigned int len)
+		   const struct ip_reply_arg *arg, unsigned int len)
 {
 	struct inet_sock *inet = inet_sk(sk);
 	struct ip_options_data replyopts;
@@ -1489,7 +1489,7 @@ void ip_send_reply(struct sock *sk, struct sk_buff *skb, __be32 daddr,
 	}
 
 	flowi4_init_output(&fl4, arg->bound_dev_if, 0,
-			   RT_TOS(ip_hdr(skb)->tos),
+			   RT_TOS(arg->tos),
 			   RT_SCOPE_UNIVERSE, sk->sk_protocol,
 			   ip_reply_arg_flowi_flags(arg),
 			   daddr, rt->rt_spec_dst,
@@ -1506,7 +1506,7 @@ void ip_send_reply(struct sock *sk, struct sk_buff *skb, __be32 daddr,
 	   with locally disabled BH and that sk cannot be already spinlocked.
 	 */
 	bh_lock_sock(sk);
-	inet->tos = ip_hdr(skb)->tos;
+	inet->tos = arg->tos;
 	sk->sk_priority = skb->priority;
 	sk->sk_protocol = ip_hdr(skb)->protocol;
 	sk->sk_bound_dev_if = arg->bound_dev_if;