[PATCH net-next] tcp: do not leak non zero tstamp in output packets

[PATCH net-next] tcp: do not leak non zero tstamp in output packets

[Eric Dumazet]

From: Eric Dumazet <edumazet@google.com>

Usage of skb->tstamp should remain private to TCP stack
(only set on packets on write queue, not on cloned ones)

Otherwise, packets given to loopback interface with a non null tstamp
can confuse netif_rx() / net_timestamp_check()

Other possibility would be to clear tstamp in loopback_xmit(),
as done in skb_scrub_packet()

Fixes: 740b0f1841f6 ("tcp: switch rtt estimations to usec resolution")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reported-by: Willem de Bruijn <willemb@google.com>
---
 net/ipv4/tcp_output.c |    2 ++
 1 file changed, 2 insertions(+)

diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index aaa68f5b1055..2b50b6e425b8 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -882,6 +882,8 @@ static int tcp_transmit_skb(struct sock *sk, struct sk_buff *skb, int clone_it,
 			skb = skb_clone(skb, gfp_mask);
 		if (unlikely(!skb))
 			return -ENOBUFS;
+		/* Our usage of tstamp should remain private */
+		skb->tstamp.tv64 = 0;
 	}
 
 	inet = inet_sk(sk);

Re: [PATCH net-next] tcp: do not leak non zero tstamp in output packets

[David Miller]

From: Eric Dumazet <eric.dumazet@gmail.com>
Date: Wed, 05 Mar 2014 14:08:38 -0800

> From: Eric Dumazet <edumazet@google.com>
> 
> Usage of skb->tstamp should remain private to TCP stack
> (only set on packets on write queue, not on cloned ones)
> 
> Otherwise, packets given to loopback interface with a non null tstamp
> can confuse netif_rx() / net_timestamp_check()
> 
> Other possibility would be to clear tstamp in loopback_xmit(),
> as done in skb_scrub_packet()
> 
> Fixes: 740b0f1841f6 ("tcp: switch rtt estimations to usec resolution")
> Signed-off-by: Eric Dumazet <edumazet@google.com>
> Reported-by: Willem de Bruijn <willemb@google.com>

Applied, thanks Eric.