ipv6: tcp: send consistent autoflowlabel in TIME_WAIT state

In case autoflowlabel is in action, skb_get_hash_flowi6()
derives a non zero skb->hash to the flowlabel.

If skb->hash is zero, a flow dissection is performed.

Since all TCP skbs sent from ESTABLISH state inherit their
skb->hash from sk->sk_txhash, we better keep a copy
of sk->sk_txhash into the TIME_WAIT socket.

After this patch, ACK or RST packets sent on behalf of
a TIME_WAIT socket have the flowlabel that was previously
used by the flow.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

3 files changed, 12 insertions, 3 deletions

diff --git a/include/net/inet_timewait_sock.h b/include/net/inet_timewait_sock.h
index c2f756aedc54..aef38c140014 100644
--- a/include/net/inet_timewait_sock.h
+++ b/include/net/inet_timewait_sock.h
@@ -70,6 +70,7 @@ struct inet_timewait_sock {
                                 tw_flowlabel    : 20,
                                 tw_pad          : 2,    /* 2 bits hole */
                                 tw_tos          : 8;
+        u32                     tw_txhash;
         struct timer_list       tw_timer;
         struct inet_bind_bucket *tw_tb;
 };
diff --git a/net/ipv4/tcp_minisocks.c b/net/ipv4/tcp_minisocks.c
index 7c35731816e2..11011e8386dc 100644
--- a/net/ipv4/tcp_minisocks.c
+++ b/net/ipv4/tcp_minisocks.c
@@ -283,6 +283,7 @@ void tcp_time_wait(struct sock *sk, int state, int timeo)
                         tw->tw_v6_rcv_saddr = sk->sk_v6_rcv_saddr;
                         tw->tw_tclass = np->tclass;
                         tw->tw_flowlabel = be32_to_cpu(np->flow_label & IPV6_FLOWLABEL_MASK);
+                        tw->tw_txhash = sk->sk_txhash;
                         tw->tw_ipv6only = sk->sk_ipv6only;
                 }
 #endif
diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c
index c1da52c7f990..ad7039137a20 100644
--- a/net/ipv6/tcp_ipv6.c
+++ b/net/ipv6/tcp_ipv6.c
@@ -883,9 +883,16 @@ static void tcp_v6_send_response(const struct sock *sk, struct sk_buff *skb, u32
                 fl6.flowi6_oif = oif;
         }
 
-        if (sk)
-                mark = (sk->sk_state == TCP_TIME_WAIT) ?
-                        inet_twsk(sk)->tw_mark : sk->sk_mark;
+        if (sk) {
+                if (sk->sk_state == TCP_TIME_WAIT) {
+                        mark = inet_twsk(sk)->tw_mark;
+                        /* autoflowlabel relies on buff->hash */
+                        skb_set_hash(buff, inet_twsk(sk)->tw_txhash,
+                                     PKT_HASH_TYPE_L4);
+                } else {
+                        mark = sk->sk_mark;
+                }
+        }
         fl6.flowi6_mark = IP6_REPLY_MARK(net, skb->mark) ?: mark;
         fl6.fl6_dport = t1->dest;
         fl6.fl6_sport = t1->source;