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From: Robert Kleemann <robert@kleemann.org>
To: Andi Kleen <ak@suse.de>
Cc: <linux-kernel@vger.kernel.org>
Subject: Re: Client receives TCP packets but does not ACK
Date: Wed, 13 Jun 2001 09:09:34 -0700 (PDT)	[thread overview]
Message-ID: <Pine.LNX.4.33.0106130856050.1153-100000@localhost.localdomain> (raw)
In-Reply-To: <oup1yoon4to.fsf@pigdrop.muc.suse.de>

On 13 Jun 2001, Andi Kleen wrote:
> The packet likely doesn't fit into the socket buffer and is silently
> dropped. The TCP stack doesn't force an ACK in this case, but it
> probably should, although it wouldn't solve the deadlock. The deadlock
> will be only solved if the local application reads data and clears the
> socket buffer. If you have a single packet that is bigger than the
> empty socket buffer / 2 you lose.
>
> You can check the allocated socket buffer size using netstat.

Thanks for the quick response!

I tried most of the netstat options and was unable to see the buffer size.
I do see the Recv-Q and the Send-Q which are usually zero except when the
client stops ack-ing and then the server's Send-Q starts filling up.

> You can increase it using the /proc/sys/net/core/rmem_{default,max}
> sysctls; in 2.4 there is also a TCP memory limit that can be tuned
> using /proc/sys/net/ipv4/tcp_mem. Doubling one of these will probably
> fix your problems.

On the client:
/proc/sys/net/core/rmem_default = 65535
/proc/sys/net/core/rmem_max = 65535
/proc/sys/net/ipv4/tcp_mem = 48128	48640	49152

On the server:
/proc/sys/net/core/rmem_default = 65535
/proc/sys/net/core/rmem_max = 65535
/proc/sys/net/ipv4/tcp_mem = 23552	24064	24576

The "bad" packet that seems to cause all the problems is only 1448
bytes long so I don't think insufficient buffers is the problem.
After the client stops ack-ing I can watch the server's Send-Q slowly
rise 2K, 4K, 6K, but it never comes close to these buffer limits.

Robert.


  reply	other threads:[~2001-06-13 16:09 UTC|newest]

Thread overview: 29+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <Pine.LNX.4.33.0106121720310.1152-100000@localhost.localdomain.suse.lists.linux.kernel>
2001-06-13  8:48 ` Andi Kleen
2001-06-13 16:09   ` Robert Kleemann [this message]
2001-07-01 21:27 Nivedita Singhvi
2001-07-11  3:43 ` Robert Kleemann
     [not found] <E15BiHy-0002xC-00@the-village.bc.nu.suse.lists.linux.kernel>
2001-06-17 20:21 ` Andi Kleen
  -- strict thread matches above, loose matches on Subject: below --
2001-06-15 12:53 Heusden, Folkert van
2001-06-15 18:27 ` Mike Black
2001-06-15 18:39   ` Gérard Roudier
2001-06-15 19:12   ` Alan Cox
2001-06-17 18:17     ` Pavel Machek
2001-06-17 19:32       ` Alan Cox
2001-06-17 19:40       ` Dan Podeanu
     [not found]         ` <200106172113.f5HLDhJ377473@saturn.cs.uml.edu>
2001-06-17 22:09           ` Dan Podeanu
2001-06-17 22:35         ` dean gaudet
2001-06-18 11:50 ` Jan Hudec
2001-06-18 16:17   ` dean gaudet
2001-06-18 16:48     ` Jonathan Morton
2001-06-18 22:30       ` dean gaudet
2001-06-18 23:43         ` Jonathan Morton
2001-06-19  2:46           ` dean gaudet
2001-06-20 21:01   ` David Schwartz
2001-06-13  0:26 Robert Kleemann
2001-06-15  3:50 ` Robert Kleemann
2001-06-15 12:44   ` Mike Black
2001-06-15 18:29     ` Albert D. Cahalan
2001-06-15 23:10       ` Robert Kleemann
2001-06-16 11:55       ` Mike Black
2001-06-16 23:56 ` Robert Kleemann
2001-06-27  1:04   ` Robert Kleemann

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