Re: [PATCH 3.10 06/31] tcp: tcp_make_synack() should clear skb->tstamp

[Willy Tarreau <w@1wt.eu>]

Hi Greg,

On Sun, Apr 26, 2015 at 03:46:26PM +0200, Greg Kroah-Hartman wrote:
> 3.10-stable review patch.  If anyone has any objections, please let me know.
> 
> ------------------
> 
> From: Eric Dumazet <edumazet@google.com>
> 
> [ Upstream commit b50edd7812852d989f2ef09dcfc729690f54a42d ]
> 
> 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@google.com>
> Signed-off-by: David S. Miller <davem@davemloft.net>
> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> ---

Unless I missed something, the commit this patch fixes was not
backported to 3.10 so I think we don't need this one. I have no
idea whether it can have a side effect there though, Eric will
probably know better.

Thanks,
Willy