netdev - Re: [net 2/2] net: fix a bug of dropping FCoE frames when disabling tx ip checksum

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, 14 Mar 2012 20:35:55 +0000
From:	Ben Hutchings <bhutchings@...arflare.com>
To:	Jeff Kirsher <jeffrey.t.kirsher@...el.com>
CC:	<davem@...emloft.net>, Yi Zou <yi.zou@...el.com>,
	<netdev@...r.kernel.org>, <gospo@...hat.com>, <sassmann@...hat.com>
Subject: Re: [net 2/2] net: fix a bug of dropping FCoE frames when disabling
 tx ip checksum

On Wed, 2012-03-14 at 00:01 -0700, Jeff Kirsher wrote:
> From: Yi Zou <yi.zou@...el.com>
> 
> Fix a bug when using 'ethtool -K ethx tx off' to turn off tx ip checksum,
> FCoE CRC offload should not be impacte. The skb_checksum_help() is needed
> only if it's not FCoE traffic for ip checksum, regardless of ethtool toggling
> the tx ip checksum on or off.
[...]

I think the bug is more fundamental, and it's not just a problem for
FCoE.  For the transmit path, the ip_summed values are specified as:

[forwarding]
 *	COMPLETE: the most generic way. Device supplied checksum of _all_
 *	    the packet as seen by netif_rx in skb->csum.
 *	    NOTE: Even if device supports only some protocols, but
 *	    is able to produce some skb->csum, it MUST use COMPLETE,
 *	    not UNNECESSARY.

[locally-generated]
 *	NONE: skb is checksummed by protocol or csum is not required.
 *
 *	PARTIAL: device is required to csum packet as seen by hard_start_xmit
 *	from skb->csum_start to the end and to record the checksum
 *	at skb->csum_start + skb->csum_offset.

It's implicit that the checksum algorithm for CHECKSUM_PARTIAL is as
specified for TCP/IP.  So none of those is correct when a different
algorithm is to be used.

It seems like we may need another ip_summed value for FCoE, SCTP or any
other protocol with a different checksum algorithm that will be
offloaded.  Maybe allow CHECKSUM_UNNECESSARY to be used on output in
that case?

Ben.

-- 
Ben Hutchings, Staff Engineer, Solarflare
Not speaking for my employer; that's the marketing department's job.
They asked us to note that Solarflare product names are trademarked.

--
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