netdev - Re: [net-next-2.6 PATCH 2/5] ixgbe: drop support for UDP in RSS hash generation

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]

Message-Id: <20100719.234454.123445936.davem@davemloft.net>
Date:	Mon, 19 Jul 2010 23:44:54 -0700 (PDT)
From:	David Miller <davem@...emloft.net>
To:	eric.dumazet@...il.com
Cc:	jeffrey.t.kirsher@...el.com, netdev@...r.kernel.org,
	gospo@...hat.com, bphilips@...ell.com, alexander.h.duyck@...el.com,
	donald.c.skidmore@...el.com
Subject: Re: [net-next-2.6 PATCH 2/5] ixgbe: drop support for UDP in RSS
 hash generation

From: Eric Dumazet <eric.dumazet@...il.com>
Date: Tue, 20 Jul 2010 08:39:40 +0200

> This would be a serious regression.

The regression is in the hardware Eric.

> Many UDP applications try hard to not use fragments. 
> 
> They are going to pay the price because some application :
> - Use big segments, fragmented.
> - Is subject to OOO artifacts.

None of this matters.  If the hardware can't flow seperate properly
it's tough cookies.

We never may reorder packets in our stack by our own doing.  The
only safe default is to turn UDP flow seperation off on chips
like ixgbe.

If you want an ethtool knob to turn it back on for your machines,
fine.  But never can it be enabled by default.
--
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