netdev - Re: [PATCH net] tcp: tcp_make_synack() should clear skb->tstamp

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Date:	Thu, 09 Apr 2015 17:29:32 -0400 (EDT)
From:	David Miller <davem@...emloft.net>
To:	eric.dumazet@...il.com
Cc:	netdev@...r.kernel.org
Subject: Re: [PATCH net] tcp: tcp_make_synack() should clear skb->tstamp

From: Eric Dumazet <eric.dumazet@...il.com>
Date: Thu, 09 Apr 2015 13:31:56 -0700

> From: Eric Dumazet <edumazet@...gle.com>
> 
> I noticed tcpdump was giving funky timestamps for locally
> generated SYNACK messages on loopback interface.
> 
> 11:42:46.938990 IP 127.0.0.1.48245 > 127.0.0.2.23850: S
> 945476042:945476042(0) win 43690 <mss 65495,nop,nop,sackOK,nop,wscale 7>
> 
> 20:28:58.502209 IP 127.0.0.2.23850 > 127.0.0.1.48245: S
> 3160535375:3160535375(0) ack 945476043 win 43690 <mss
> 65495,nop,nop,sackOK,nop,wscale 7>
> 
> This is because we need to clear skb->tstamp before
> entering lower stack, otherwise net_timestamp_check()
> does not set skb->tstamp.
> 
> Fixes: 7faee5c0d514 ("tcp: remove TCP_SKB_CB(skb)->when")
> Signed-off-by: Eric Dumazet <edumazet@...gle.com>

Applied and queued up for -stable.
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