netdev - [PATCH net 1/2] net-timestamp: fix missing ACK timestamp

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Date:	Tue, 12 Aug 2014 14:53:16 -0400
From:	Willem de Bruijn <willemb@...gle.com>
To:	netdev@...r.kernel.org
Cc:	davem@...emloft.net, eric.dumazet@...il.com,
	richardcochran@...il.com, Willem de Bruijn <willemb@...gle.com>
Subject: [PATCH net 1/2] net-timestamp: fix missing ACK timestamp

ACK timestamps are generated in tcp_clean_rtx_queue. The TSO datapath
can break out early, causing the timestamp code to be skipped. Move
the code up before the break.

Reported-by: David S. Miller <davem@...emloft.net>

Also fix a boundary condition: tp->snd_una is the next unacknowledged
byte and between tests inclusive (a <= b <= c), so generate a an ACK
timestamp if (prior_snd_una <= tskey <= tp->snd_una - 1).

Signed-off-by: Willem de Bruijn <willemb@...gle.com>
---
 net/ipv4/tcp_input.c | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index a3d47af..1a8e89f 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -3050,10 +3050,15 @@ static int tcp_clean_rtx_queue(struct sock *sk, int prior_fackets,
 	first_ackt.v64 = 0;
 
 	while ((skb = tcp_write_queue_head(sk)) && skb != tcp_send_head(sk)) {
+		struct skb_shared_info *shinfo = skb_shinfo(skb);
 		struct tcp_skb_cb *scb = TCP_SKB_CB(skb);
 		u8 sacked = scb->sacked;
 		u32 acked_pcount;
 
+		if (unlikely(shinfo->tx_flags & SKBTX_ACK_TSTAMP) &&
+		    between(shinfo->tskey, prior_snd_una, tp->snd_una - 1))
+			__skb_tstamp_tx(skb, NULL, sk, SCM_TSTAMP_ACK);
+
 		/* Determine how many packets and what bytes were acked, tso and else */
 		if (after(scb->end_seq, tp->snd_una)) {
 			if (tcp_skb_pcount(skb) == 1 ||
@@ -3107,11 +3112,6 @@ static int tcp_clean_rtx_queue(struct sock *sk, int prior_fackets,
 			tp->retrans_stamp = 0;
 		}
 
-		if (unlikely(skb_shinfo(skb)->tx_flags & SKBTX_ACK_TSTAMP) &&
-		    between(skb_shinfo(skb)->tskey, prior_snd_una,
-			    tp->snd_una + 1))
-			__skb_tstamp_tx(skb, NULL, sk, SCM_TSTAMP_ACK);
-
 		if (!fully_acked)
 			break;
 
-- 
2.1.0.rc2.206.gedb03e5

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