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[Qemu-devel] Re: [PATCH] Add pcap-based host network bridge
From: |
Jan Kiszka |
Subject: |
[Qemu-devel] Re: [PATCH] Add pcap-based host network bridge |
Date: |
Tue, 24 Mar 2009 18:28:09 +0100 |
User-agent: |
Mozilla/5.0 (X11; U; Linux i686 (x86_64); de; rv:1.8.1.12) Gecko/20080226 SUSE/2.0.0.12-1.1 Thunderbird/2.0.0.12 Mnenhy/0.7.5.666 |
Anthony Liguori wrote:
> Jan Kiszka wrote:
>> This introduces bridged networking via pcap. Both Unix and Windows
>> platforms are supported.
>>
>> While tap-based bridging provides basically the same support pcap does,
>> the latter is often more handy to set up. Under Linux, it doesn't
>> require to configure a bridge and it is able to bypass the ebtables if
>> this is desired. Also under Windows, the bridge setup can be lengthy
>> procedure compared to using the pcap interface.
>>
>> Signed-off-by: Klaus Wenninger <address@hidden>
>> Signed-off-by: Jan Kiszka <address@hidden>
>>
>
> The previous version of this had a fundamental flaw wrt guest->host
> communication on Linux. My understanding was that this was an intrinsic
> limitation of pcap.
To my understanding too. We will try to look closer at this, maybe there
are smarter alternatives at least on some platforms (PF_PACKET under
Linux...?).
Klaus explained to me that there is some switch in winpcap to support
this, but it caused troubles due to weird packet loops. I don't have a
Windows platform to test, but I will see if we can clarify this in some
other way.
>
> That's a blocker IMHO because it will invariably lead to many folks
> asking why ping to the host doesn't work (just like slirp). Since it
> still requires root privileges, I don't think it improves a lot on tap.
>
Well, in case we do not find a workaround for host<->guest
communication, would the patch remain unacceptable even with proper,
prominent documentation of this shortcoming?
Jan
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