tcp: timestamp SYN+DATA messages

All skb in socket write queue should be properly timestamped.

In case of FastOpen, we special case the SYN+DATA 'message' as we
queue in socket wrote queue the two fallback skbs:

1) SYN message by itself.
2) DATA segment by itself.

We should make sure these skbs have proper timestamps.

Add a WARN_ON_ONCE() to eventually catch future violations.

Fixes: 740b0f1841f6 ("tcp: switch rtt estimations to usec resolution")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Neal Cardwell <ncardwell@google.com>
Cc: Yuchung Cheng <ycheng@google.com>
Acked-by: Neal Cardwell <ncardwell@google.com>
Acked-by: Yuchung Cheng <ycheng@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

2 files changed, 7 insertions, 0 deletions

diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index b99003f556d8..e1661f46fd19 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -3067,6 +3067,7 @@ static int tcp_clean_rtx_queue(struct sock *sk, int prior_fackets,
                         flag |= FLAG_RETRANS_DATA_ACKED;
                 } else {
                         last_ackt = skb->skb_mstamp;
+                        WARN_ON_ONCE(last_ackt.v64 == 0);
                         if (!first_ackt.v64)
                                 first_ackt = last_ackt;
 
diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index bc0fb0fc7552..5a163de5e142 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -2972,6 +2972,12 @@ static int tcp_send_syn_data(struct sock *sk, struct sk_buff *syn)
         tcp_connect_queue_skb(sk, data);
         fo->copied = data->len;
 
+        /* syn_data is about to be sent, we need to take current time stamps
+         * for the packets that are in write queue : SYN packet and DATA
+         */
+        skb_mstamp_get(&syn->skb_mstamp);
+        data->skb_mstamp = syn->skb_mstamp;
+
         if (tcp_transmit_skb(sk, syn_data, 0, sk->sk_allocation) == 0) {
                 tp->syn_data = (fo->copied > 0);
                 NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPORIGDATASENT);