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List:       kvm
Subject:    Re: [PATCH] Work around dhclient brokenness
From:       Avi Kivity <avi () qumranet ! com>
Date:       2008-08-18 10:56:57
Message-ID: 48A95579.6080004 () qumranet ! com
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Anthony Liguori wrote:
> With the latest GSO/csum offload patches, any guest using an unpatched version
> of dhclient (any Ubuntu guest, for instance), will no longer be able to get
> a DHCP address.
>
> dhclient is actually at fault here.  It uses AF_PACKET to receive DHCP responses
> but does not check auxdata to see if the packet has a valid csum.  This causes
> it to throw out the DHCP responses it gets from the virtio interface as there
> is not a valid checksum.
>
> Fedora has carried a patch to fix their dhclient (it's needed for Xen too) but
> this patch has not made it into a release of dhclient.  AFAIK, the patch is in
> the dhclient CVS but I cannot confirm since their CVS is not public.
>
> This patch, suggested by Rusty, looks for UDP packets (of a normal MTU) and
> explicitly adds a checksum to them if they are missing one.  We could further
> refine the search criteria based on srcport but that's probably unnecessary.
>
>   

Won't this slow down nfs/udp?  I think a srcport check would be good here.

-- 
error compiling committee.c: too many arguments to function

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