netdev - [PATCH net-next] tcp: timestamp SYN+DATA messages

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Date:	Sun, 09 Mar 2014 17:36:02 -0700
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	David Miller <davem@...emloft.net>
Cc:	netdev <netdev@...r.kernel.org>,
	Neal Cardwell <ncardwell@...gle.com>,
	Yuchung Cheng <ycheng@...gle.com>
Subject: [PATCH net-next] tcp: timestamp SYN+DATA messages

From: Eric Dumazet <edumazet@...gle.com>

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@...gle.com>
Cc: Neal Cardwell <ncardwell@...gle.com>
Cc: Yuchung Cheng <ycheng@...gle.com>
---
 net/ipv4/tcp_input.c  |    1 +
 net/ipv4/tcp_output.c |    6 ++++++
 2 files changed, 7 insertions(+)

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..a64c51d6f9b6 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);


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