From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mailman by lists.gnu.org with tmda-scanned (Exim 4.43) id 1LmAQD-0005I5-1x for qemu-devel@nongnu.org; Tue, 24 Mar 2009 13:28:17 -0400 Received: from exim by lists.gnu.org with spam-scanned (Exim 4.43) id 1LmAQ7-0005Fd-U6 for qemu-devel@nongnu.org; Tue, 24 Mar 2009 13:28:16 -0400 Received: from [199.232.76.173] (port=51351 helo=monty-python.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1LmAQ7-0005FX-Nj for qemu-devel@nongnu.org; Tue, 24 Mar 2009 13:28:11 -0400 Received: from lizzard.sbs.de ([194.138.37.39]:19060) by monty-python.gnu.org with esmtps (TLS-1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.60) (envelope-from ) id 1LmAQ7-0008EA-7I for qemu-devel@nongnu.org; Tue, 24 Mar 2009 13:28:11 -0400 Received: from mail2.sbs.de (localhost [127.0.0.1]) by lizzard.sbs.de (8.12.11.20060308/8.12.11) with ESMTP id n2OHS9KF009596 for ; Tue, 24 Mar 2009 18:28:09 +0100 Received: from [146.254.148.245] (mchn012c.med.siemens.de [146.254.148.245] (may be forged)) by mail2.sbs.de (8.12.11.20060308/8.12.11) with ESMTP id n2OHS92O023842 for ; Tue, 24 Mar 2009 18:28:09 +0100 Message-ID: <49C91829.6000606@siemens.com> Date: Tue, 24 Mar 2009 18:28:09 +0100 From: Jan Kiszka MIME-Version: 1.0 References: <49C0BFCD.1040304@siemens.com> <49C6F2AA.40408@codemonkey.ws> In-Reply-To: <49C6F2AA.40408@codemonkey.ws> Content-Type: text/plain; charset=ISO-8859-15 Content-Transfer-Encoding: 7bit Subject: [Qemu-devel] Re: [PATCH] Add pcap-based host network bridge Reply-To: qemu-devel@nongnu.org List-Id: qemu-devel.nongnu.org List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org 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 >> Signed-off-by: Jan Kiszka >> > > 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 -- Siemens AG, Corporate Technology, CT SE 2 Corporate Competence Center Embedded Linux