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:	Tue, 27 Nov 2012 09:05:30 -0800
From:	Rick Jones <rick.jones2@...com>
To:	Saku Ytti <saku@...i.fi>
CC:	netdev@...r.kernel.org
Subject: Re: TCP and reordering

On 11/27/2012 01:32 AM, Saku Ytti wrote:
> Today due to fast retransmit performance on links which cause
> reordering is appalling.
>
> Is it too esoteric situation to handle gracefully? Couldn't we
> maintain 'reorder' counter in socket, which is increment when we get
> two copies of same packet after duplicate ack, if this counter is
> sufficiently high in relation to packet loss, we could start delaying
> duplicate acks as we'd expect to receive the sequence very soon.

Packet reordering is supposed to be the exception, not the rule.  Links 
which habitually/constantly introduce reordering are, in my opinion, 
broken.  Optimizing for them would be optimizing an error case.

That said, there is net.ipv4.tcp_reordering which you can increase from 
the default of three to desensitize TCP to such broken links.  That will 
though be on the sending rather than receiving side.

rick jones
--
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