netdev - fq_codel and skb->hash

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-next>] [day] [month] [year] [list]

Message-ID: <f9913fca-da16-8620-d237-d7d8d09cced2@cradlepoint.com>
Date:   Mon, 16 Jan 2017 17:04:44 -0700
From:   Andrew Collins <acollins@...dlepoint.com>
To:     <netdev@...r.kernel.org>
CC:     <edumazet@...gle.com>
Subject: fq_codel and skb->hash

The fq_codel packet scheduler always regenerates the skb flow hash.  Is there any reason
to do this other than the recent hash perturbation additions?

I ask because I have a case where an incoming set of TCP flows is encapsulated in a
single ipsec tunnel, which is then classified on egress into a single flow by fq_codel
resulting in poor behavior.

Reusing the skb hash set in receive results in much better behavior, as the value is
determined pre-encapsulation and flows end up being distributed more naturally across
codel queues.

Is opportunistically using the pre-existing skb hash (if available) problematic?  Is
there a better way to manage flow separation in routed+encapsulated traffic?

Thanks,
Andrew Collins