netdev - Re: TCP and reordering

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Wed, 28 Nov 2012 09:16:36 -0800
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	David Woodhouse <dwmw2@...radead.org>
Cc:	Benjamin LaHaise <bcrl@...ck.org>,
	Vijay Subramanian <subramanian.vijay@...il.com>,
	David Miller <davem@...emloft.net>, saku@...i.fi,
	rick.jones2@...com, netdev@...r.kernel.org
Subject: Re: TCP and reordering

On Wed, 2012-11-28 at 16:41 +0000, David Woodhouse wrote:

> Another fun issue with tunnelling protocols and BQL... packets tend to
> *grow* as they get encapsulated. So you might end up calling
> netdev_sent_queue() with a given size, then netdev_completed_queue()
> with a bigger packet later...

Its the driver responsibility to maintain the coherent 'bytes' value for
each transmitted/completed packet.

If a driver calls an external entity, it cannot possibly use BQL, unless
doing an approximation (bytes becomes a fixed value)

BQL was really something to control/limit queueing on ethernet links,
not for stacked devices, as stacked devices normally have no queue.




--
To unsubscribe from this list: send the line "unsubscribe netdev" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html