tcp: tcp_v[46]_conn_request: fix snt_synack initialization

Commit 016818d07 (tcp: TCP Fast Open Server - take SYNACK RTT after
completing 3WHS) changes the code to only take a snt_synack timestamp
when a SYNACK transmit or retransmit succeeds. This behaviour is later
broken by commit 843f4a55e (tcp: use tcp_v4_send_synack on first
SYN-ACK), as snt_synack is now updated even if tcp_v4_send_synack
fails.

Also, commit 3a19ce0ee (tcp: IPv6 support for fastopen server) misses
the required IPv6 updates for 016818d07.

This patch makes sure that snt_synack is updated only when the SYNACK
trasnmit/retransmit succeeds, for both IPv4 and IPv6.

Cc: Cardwell <ncardwell@google.com>
Cc: Daniel Lee <longinus00@gmail.com>
Cc: Yuchung Cheng <ycheng@google.com>

Signed-off-by: Octavian Purdila <octavian.purdila@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 2 insertions, 1 deletions

diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c
index 08ae3da0db4a..a962455471ba 100644
--- a/net/ipv6/tcp_ipv6.c
+++ b/net/ipv6/tcp_ipv6.c
@@ -497,6 +497,8 @@ static int tcp_v6_send_synack(struct sock *sk, struct dst_entry *dst,
                 skb_set_queue_mapping(skb, queue_mapping);
                 err = ip6_xmit(sk, skb, fl6, np->opt, np->tclass);
                 err = net_xmit_eval(err);
+                if (!tcp_rsk(req)->snt_synack && !err)
+                        tcp_rsk(req)->snt_synack = tcp_time_stamp;
         }
 
 done:
@@ -1100,7 +1102,6 @@ have_isn:
                 goto drop_and_free;
 
         tcp_rsk(req)->snt_isn = isn;
-        tcp_rsk(req)->snt_synack = tcp_time_stamp;
         tcp_openreq_init_rwin(req, sk, dst);
         fastopen = !want_cookie &&
                    tcp_try_fastopen(sk, skb, req, &foc, dst);