netdev - Re: After many hours all outbound connections get stuck in SYN

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Message-ID: <83a51e120712190853q33d9c7c1t4a46380665b7538b@mail.gmail.com>
Date:	Wed, 19 Dec 2007 11:53:06 -0500
From:	"James Nichols" <jamesnichols3@...il.com>
To:	"Eric Dumazet" <dada1@...mosbay.com>
Cc:	"Jan Engelhardt" <jengelh@...putergmbh.de>,
	linux-kernel@...r.kernel.org,
	"Linux Netdev List" <netdev@...r.kernel.org>
Subject: Re: After many hours all outbound connections get stuck in SYN_SENT

> So you see outgoing SYN packets, but no SYN replies coming from the remote
> peer ?  (you mention ACKS, but the first packet received from the remote
>  peer should be a SYN+ACK),

Right, I meant to say SYN+ACK.  I don't see them coming back.


> When the problem comes, instead of restarting the application, please take a
> tcpdump of say 10.000 packets.
> Then turn off tcp_sack and take a 2nd tcpdump sample, and make both samples
> available to us.

I can take these captures and take a look at the results.
Unfortunately, I don't think I'll be able to make the captures
available to the general public.



> If turning off tcp_sack makes the problem go away, why dont you turn it off
> all the time ?

Unfortunately, I think that will be the answer if I can't get any help
fixing this problem in the kernel.  It's a bummer, because many of the
remote hosts my application communicates with are on wireless links,
so there may be performance implications to turning SACK off.
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