[TCP]: Honour sk_bound_dev_if in tcp_v4_send_ack

A time_wait socket inherits sk_bound_dev_if from the original socket,
but it is not used when sending ACK packets using ip_send_reply.

Fix by passing the oif to ip_send_reply in struct ip_reply_arg and
use it for output routing.

Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

2 files changed, 5 insertions, 1 deletions

diff --git a/net/ipv4/ip_output.c b/net/ipv4/ip_output.c
index d6427d918512..34ea4547ebbe 100644
--- a/net/ipv4/ip_output.c
+++ b/net/ipv4/ip_output.c
@@ -1352,7 +1352,8 @@ void ip_send_reply(struct sock *sk, struct sk_buff *skb, struct ip_reply_arg *ar
         }
 
         {
-                struct flowi fl = { .nl_u = { .ip4_u =
+                struct flowi fl = { .oif = arg->bound_dev_if,
+                                    .nl_u = { .ip4_u =
                                               { .daddr = daddr,
                                                 .saddr = rt->rt_spec_dst,
                                                 .tos = RT_TOS(ip_hdr(skb)->tos) } },
@@ -1376,6 +1377,7 @@ void ip_send_reply(struct sock *sk, struct sk_buff *skb, struct ip_reply_arg *ar
         inet->tos = ip_hdr(skb)->tos;
         sk->sk_priority = skb->priority;
         sk->sk_protocol = ip_hdr(skb)->protocol;
+        sk->sk_bound_dev_if = arg->bound_dev_if;
         ip_append_data(sk, ip_reply_glue_bits, arg->iov->iov_base, len, 0,
                        &ipc, rt, MSG_DONTWAIT);
         if ((skb = skb_peek(&sk->sk_write_queue)) != NULL) {
diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
index 47c61055eb60..97e294e82679 100644
--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c
@@ -705,6 +705,8 @@ static void tcp_v4_send_ack(struct tcp_timewait_sock *twsk,
                                       ip_hdr(skb)->saddr, /* XXX */
                                       arg.iov[0].iov_len, IPPROTO_TCP, 0);
         arg.csumoffset = offsetof(struct tcphdr, check) / 2;
+        if (twsk)
+                arg.bound_dev_if = twsk->tw_sk.tw_bound_dev_if;
 
         ip_send_reply(tcp_socket->sk, skb, &arg, arg.iov[0].iov_len);