netdev - Re: TCP keepalives ignored by kernel when the contain timestamps

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Message-ID: <1307731266.2872.4.camel@edumazet-laptop>
Date:	Fri, 10 Jun 2011 20:41:06 +0200
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Charles Bearden <Charles.F.Bearden@....tmc.edu>
Cc:	netdev@...r.kernel.org
Subject: Re: TCP keepalives ignored by kernel when the contain timestamps

Le vendredi 10 juin 2011 à 13:13 -0500, Charles Bearden a écrit :
> On 06/10/2011 01:04 PM, Eric Dumazet wrote:
> > Le vendredi 10 juin 2011 à 13:00 -0500, Charles Bearden a écrit :
> >
> >> Each keepalive from the Win2008 machine has a 1-byte payload 0x00. The last byte
> >> of the last packet with a payload before that from the Win2008 host (at
> >> 14:40:18.166394 in the paste) is also 0x00. Is that what you were asking about?
> >>
> >
> > Yes, thats fine, thanks :)
> 
> One other thing: when tcp timestamps are disabled on the Linux (receiving) end, 
> so that the Win2008 host sends keepalives without timestamps, the checksums in 
> the keepalives are correct. It's only when the keepalives also contain 
> timestamps that the checksums are broken.
> 
> If you think this might be a Linux kernel issue, I'll be glad to keep working 
> with you, but I don't want to spam this list if my problem isn't relevant. Thank 
> you for your help in any case.
> 

Well, if your linux machine receives frames with a bad checksum, linux
is working well : These frames must be dropped.

It is a bug in the sender (Win2008 in this case). 

I am not that surprised, given timestamps were disabled in microsoft
products until very last releases (Windows Seven, and apparently
winserver 2008)



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