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Re: xen networking and tap0



On Fri, Jan 22, 2010 at 11:09:52AM -0700, Brook Milligan wrote:
> Manuel Bouyer writes:
>  > On Fri, Jan 22, 2010 at 11:26:57AM -0500, der Mouse wrote:
>  > that's not completely true; tap interfaces can be used without controlling
>  > processes. The kernel should still be able to use it as a regular
>  > interface for bridging purposes (it would behaves like a real
>  > ethernet device without the cable plugged in).
> 
> And that is supported by the fact that it seems to work that way if
> the domU interface is statically assigned.  For example, ping and ssh
> connections to the dom0 from the domU work fine.  However, the domU
> dhcp requests are not being seen by the dom0.  The dom0 tcpdump
> recognizes the requests on tap0 but there are no responses:
> 
> 11:32:25.016539 IP 0.0.0.0.bootpc > 255.255.255.255.bootps: BOOTP/DHCP, 
> Request from 00:16:3e:00:00:12 (oui Unknown), length 300
> 
> So, why does the bridging not work for dhcp requests when it does seem
> to work for at least some other packets?

I wonder if it is an issue of dhcpd not seeing incoming packets or maybe
an issue of dhcpd not being able to send the answer (it uses a bpf
filter for incoming packets and a raw socket for outgoing packets, if
memory serves).  Do you really not see anything in the logs?

-- 
Quentin Garnier - cube%cubidou.net@localhost - cube%NetBSD.org@localhost
"See the look on my face from staying too long in one place
[...] every time the morning breaks I know I'm closer to falling"
KT Tunstall, Saving My Face, Drastic Fantastic, 2007.

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