netdev - Problem with cxgb, mac-vlans, and UDP checksum offloading.

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>] [day] [month] [year] [list]

Message-ID: <475ED616.6070903@candelatech.com>
Date:	Tue, 11 Dec 2007 10:25:26 -0800
From:	Ben Greear <greearb@...delatech.com>
To:	Divy Le Ray <divy@...lsio.com>, NetDev <netdev@...r.kernel.org>
Subject: Problem with cxgb, mac-vlans, and UDP checksum offloading.

Hello!

This is with kernel 2.6.23, plus our hacks, but the mac-vlan logic
is part of the official kernel now.  OS is Fedora 8.  I have applied
patch 1 and 3 of those sent a few weeks ago for the cxgb as well.

While testing NFS on mac-vlans on cxgb, we noticed that
UDP packets have incorrect checksums when sent from
the mac-vlan device on a cxgb interface to another system.  When sending
from a regular ethernet device (cxgb), it works fine.
When we disable rx and tx UDP checksums on the mac-vlan
device, it works fine.  When we use e1000 interfaces (which
also do rx/tx UDP checksumming), mac-vlans & NFS works fine
with mac-vlan rx/tx checksumming on (the default value).

So, there seems something weird about the cxgb NIC when
used with mac-vlans.  Perhaps it is somehow paying attention
to MAC addresses when it determines if it should csum a packet
or not?

If you want to test it yourself, grab the latest iputils package
and create MAC-VLANs like this:

ip link add link eth0 name eth0#0 address 00:11:22:33:44:55 type macvlan

If you would like a packet trace or any other debugging, please
let me know.

Thanks,
Ben

-- 
Ben Greear <greearb@...delatech.com>
Candela Technologies Inc  http://www.candelatech.com

--
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