netdev - dhclient, checksum and tap

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Message-ID: <20100625151008.GA17911@redhat.com>
Date:	Fri, 25 Jun 2010 18:10:08 +0300
From:	"Michael S. Tsirkin" <mst@...hat.com>
To:	Herbert Xu <herbert.xu@...hat.com>
Cc:	netdev@...r.kernel.org
Subject: dhclient, checksum and tap

Hi!
I've been looking at the issue of checksum on
dhcp packets: to recap, 8dc4194474159660d7f37c495e3fc3f10d0db8cc
added a way for af_packet sockets to get the packet status.
Unfortunately not all dhcp clients caught up with
this development, so they are still broken
when both server and client run on the same host,
e.g. with bridge+tap.

And of course virtualization adds another way to run
old dhcp clients, so userspace virtio net in qemu has
a hack to detect DHCP and fill in the checksum.
I guess we could add this in vhost, as well.

However, one wonders whether the tap driver is a better place
for this work-around, that would help all users.
Any objections against putting such code in tap?

-- 
MST
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