Subject: Re: [PATCH] netfilter: add CHECKSUM target

From: Patrick McHardy <[email-masked]>
Date: Fri, 09 Jul 2010 17:17:36 +0200

Am 09.07.2010 00:29, schrieb Michael S. Tsirkin:
> This adds a `CHECKSUM' target, which can be used in the iptables mangle
> table.
> 
> You can use this target to compute and fill in the checksum in
> an IP packet that lacks a checksum.  This is particularly useful,
> if you need to work around old applications such as dhcp clients,
> that do not work well with checksum offloads, but don't want to
> disable checksum offload in your device.
> 
> The problem happens in the field with virtualized applications.
> For reference, see Red Hat bz 605555, as well as
> http://www.spinics.net/lists/kvm/msg37660.html
> 
> Typical expected use (helps old dhclient binary running in a VM):
> iptables -A POSTROUTING -t mangle -p udp --dport 68 -j CHECKSUM
> --checksum-fill

I'm not sure this is something we want to merge upstream and
support indefinitely. Dave suggested this as a temporary
out-of-tree workaround until the majority of guest dhcp clients
are fixed. Has anything changed that makes this course of
action impractical?