From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-8.6 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, MENTIONS_GIT_HOSTING,SPF_HELO_NONE,SPF_PASS autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id D656FC43460 for ; Fri, 23 Apr 2021 15:32:23 +0000 (UTC) Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 422DE611CD for ; Fri, 23 Apr 2021 15:32:23 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 422DE611CD Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:57442 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1lZxn3-0000aI-Px for qemu-devel@archiver.kernel.org; Fri, 23 Apr 2021 11:32:22 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:40196) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1lZxlp-0007md-P2 for qemu-devel@nongnu.org; Fri, 23 Apr 2021 11:31:05 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]:27034) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1lZxlm-0000cG-EU for qemu-devel@nongnu.org; Fri, 23 Apr 2021 11:31:04 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1619191861; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=+xgYjixjgRF1rM4Au2Akfj0nFwMMU3SWxorFJOP5bps=; b=QoFdGXgOwlaMzJmyWJ4JUm2YfWHHQIHEg/LGkI6M0U+IySY3aDakNJNzXIQxsrT2Ycgi2v kOxL6epdbPpigO7dGhmjXvYOXp0K0o+GRA8D1v9pCkfx8/MOUvsObKft6hAkUqs9fA+I7+ WpUFEGFu4B0QbHj9Mnvama9OMTI3Sro= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-186-Z9F5A-0xNliGDWr4L-_Asw-1; Fri, 23 Apr 2021 11:29:43 -0400 X-MC-Unique: Z9F5A-0xNliGDWr4L-_Asw-1 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.phx2.redhat.com [10.5.11.16]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id D291E6D4E0; Fri, 23 Apr 2021 15:29:42 +0000 (UTC) Received: from maya.cloud.tilaa.com (unknown [10.36.110.6]) by smtp.corp.redhat.com (Postfix) with ESMTP id 766235C1BB; Fri, 23 Apr 2021 15:29:42 +0000 (UTC) Received: from elisabeth (238-055-210-188.ip-addr.inexio.net [188.210.55.238]) by maya.cloud.tilaa.com (Postfix) with ESMTPSA id A712A40098; Fri, 23 Apr 2021 17:29:41 +0200 (CEST) Date: Fri, 23 Apr 2021 17:29:40 +0200 From: Stefano Brivio To: Ralph Schmieder Subject: Re: socket.c added support for unix domain socket datagram transport Message-ID: <20210423172940.14f48b49@elisabeth> In-Reply-To: <1C0E1BC5-904F-46B0-8044-68E43E67BE60@gmail.com> References: <1C0E1BC5-904F-46B0-8044-68E43E67BE60@gmail.com> Organization: Red Hat MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=sbrivio@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Received-SPF: pass client-ip=170.10.133.124; envelope-from=sbrivio@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -27 X-Spam_score: -2.8 X-Spam_bar: -- X-Spam_report: (-2.8 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_LOW=-0.7, RCVD_IN_MSPIKE_H4=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: "Daniel P. =?UTF-8?B?QmVycmFuZ8Op?=" , qemu-devel@nongnu.org Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" Hi Ralph, On Fri, 23 Apr 2021 08:56:48 +0200 Ralph Schmieder wrote: > Hey... new to this list. I was looking for a way to use Unix domain > sockets as a network transport between local VMs. > > I'm part of a team where we run dozens if not hundreds of VMs on a > single compute instance which are highly interconnected. > > In the current implementation, I use UDP sockets (e.g. something like > > -netdev > id=bla,type=socket,udp=localhost:1234,localaddr=localhost:5678) > > which works great. > > The downside of this approach is that I need to keep track of all the > UDP ports in use and that there's a potential for clashes. Clearly, > having Unix domain sockets where I could store the sockets in the > VM's directory would be much easier to manage. > > However, even though there is some AF_UNIX support in net/socket.c, > it's > > - not configurable > - it doesn't work I hate to say this, but I've been working on something very similar just in the past days, with the notable difference that I'm using stream-oriented AF_UNIX sockets instead of datagram-oriented. I have a similar use case, and after some experiments I picked a stream-oriented socket over datagram-oriented because: - overhead appears to be the same - message boundaries make little sense here -- you already have a 32-bit vnet header with the message size defining the message boundaries - datagram-oriented AF_UNIX sockets are actually reliable and there's no packet reordering on Linux, but this is not "formally" guaranteed - it's helpful for me to know when a qemu instance disconnects for any reason > As a side note, I tried to pass in an already open FD, but that > didn't work either. This actually worked for me as a quick work-around, either with: https://github.com/StevenVanAcker/udstools or with a trivial C implementation of that, that does essentially: fd = strtol(argv[1], NULL, 0); if (fd < 3 || fd > INT_MAX || errno) usage(argv[0]); s = socket(AF_UNIX, SOCK_STREAM, 0); if (s < 0) { perror("socket"); exit(EXIT_FAILURE); } if (connect(s, (const struct sockaddr *)&addr, sizeof(addr)) < 0) { perror("connect"); exit(EXIT_FAILURE); } if (dup2(s, (int)fd) < 0) { perror("dup"); exit(EXIT_FAILURE); } close(s); execvp(argv[2], argv + 2); perror("execvp"); where argv[1] is the socket number you pass in the qemu command line (-net socket,fd=X) and argv[2] is the path to qemu. > So, I added some code which does work for me... e.g. > > - can specify the socket paths like -netdev > id=bla,type=socket,unix=/tmp/in:/tmp/out > - it does forward packets between two Qemu instances running > back-to-back > > I'm wondering if this is of interest for the wider community and, if > so, how to proceed. > > Thanks, > -ralph > > Commit > https://github.com/rschmied/qemu/commit/73f02114e718ec898c7cd8e855d0d5d5d7abe362 I think your patch could be a bit simpler, as you could mostly reuse net_socket_udp_init() for your initialisation, and perhaps rename it to net_socket_dgram_init(). Anyway, I wonder, would my approach work for you instead? I'm posting my patch in a minute. -- Stefano