netdev - Re: tcp: Do not apply TSO segment limit to non-TSO packets

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Date:	Mon, 19 Jan 2015 14:39:26 +0100
From:	Thomas Jarosch <thomas.jarosch@...ra2net.com>
To:	Herbert Xu <herbert@...dor.apana.org.au>
Cc:	netdev@...r.kernel.org, edumazet@...gle.com,
	Steffen Klassert <steffen.klassert@...unet.com>,
	Ben Hutchings <bhutchings@...arflare.com>,
	"David S. Miller" <davem@...emloft.net>
Subject: Re: tcp: Do not apply TSO segment limit to non-TSO packets

Hi Herbert,

On Thursday, 1. January 2015 00:39:23 Herbert Xu wrote:
> The problem is that when the MSS goes down, existing queued packet
> on the TX queue that have not been transmitted yet all look like
> TSO packets and get treated as such.
> 
> This then triggers a bug where tcp_mss_split_point tells us to
> generate a zero-sized packet on the TX queue.  Once that happens
> we're screwed because the zero-sized packet can never be removed
> by ACKs.

picking up this one again: Is there any valid use case to have
zero-sized packets in the TX queue? If not, may be a WARN_ON() could
be added to the processing of the TX queue. That would help to
prevent future issues like this.

Cheers,
Thomas

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