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 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id D8E7BC433F5 for ; Thu, 7 Oct 2021 14:54:14 +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 9A9C261038 for ; Thu, 7 Oct 2021 14:54:14 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org 9A9C261038 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=nongnu.org Received: from localhost ([::1]:34964 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1mYUmj-0002ad-Ik for qemu-devel@archiver.kernel.org; Thu, 07 Oct 2021 10:54:13 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:54458) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1mYUky-0008J8-La for qemu-devel@nongnu.org; Thu, 07 Oct 2021 10:52:24 -0400 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:56368) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1mYUkv-00083G-CX for qemu-devel@nongnu.org; Thu, 07 Oct 2021 10:52:24 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1633618340; 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: in-reply-to:in-reply-to:references:references; bh=0NH9jobNvwHIaCkuJqIQtKWyXJjQ06bw0AL3eueD+68=; b=LY26uGTLENMLnklUIecP6P1AaSOT6hrwlMLzuLb6sVmiWVx06wE4ShkOP2NYRrIb3Yx0R3 v41nwdnX0nF+DN02vfGh1LRNXvu7s44yIi1wHB3xvgYGACZ52x25xnrCuXufyNGlhBkAuJ USp9PHWki8AgvZhyjgK7J5fVIkzD3oU= 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-349-BVJyYs3nM1W_YQNjZPgT9w-1; Thu, 07 Oct 2021 10:52:17 -0400 X-MC-Unique: BVJyYs3nM1W_YQNjZPgT9w-1 Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.11]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 8B617100C660; Thu, 7 Oct 2021 14:52:16 +0000 (UTC) Received: from redhat.com (ovpn-113-216.phx2.redhat.com [10.3.113.216]) by smtp.corp.redhat.com (Postfix) with ESMTPS id E8F3C4180; Thu, 7 Oct 2021 14:52:15 +0000 (UTC) Date: Thu, 7 Oct 2021 09:52:14 -0500 From: Eric Blake To: John Snow Subject: Re: [PATCH v2 04/17] python/aqmp: add send_fd_scm Message-ID: <20211007145214.ua7db2hwifhtawis@redhat.com> References: <20210923004938.3999963-1-jsnow@redhat.com> <20210923004938.3999963-5-jsnow@redhat.com> MIME-Version: 1.0 In-Reply-To: <20210923004938.3999963-5-jsnow@redhat.com> User-Agent: NeoMutt/20210205-818-e2615c X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=eblake@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Received-SPF: pass client-ip=216.205.24.124; envelope-from=eblake@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -28 X-Spam_score: -2.9 X-Spam_bar: -- X-Spam_report: (-2.9 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.05, 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_H2=-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: Kevin Wolf , Vladimir Sementsov-Ogievskiy , Eduardo Habkost , qemu-block@nongnu.org, qemu-devel@nongnu.org, Hanna Reitz , Cleber Rosa Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Wed, Sep 22, 2021 at 08:49:25PM -0400, John Snow wrote: > The single space is indeed required to successfully transmit the file > descriptor to QEMU. Sending fds requires a payload of at least one byte, but I don't think that qemu cares which byte. Thus, while your choice of space is fine, the commit message may be a bit misleading at implying it must be space. > > Python 3.11 removes support for calling sendmsg directly from a > transport's socket. There is no other interface for doing this, our use > case is, I suspect, "quite unique". > > As far as I can tell, this is safe to do -- send_fd_scm is a synchronous > function and we can be guaranteed that the async coroutines will *not* be > running when it is invoked. In testing, it works correctly. > > I investigated quite thoroughly the possibility of creating my own > asyncio Transport (The class that ultimately manages the raw socket > object) so that I could manage the socket myself, but this is so wildly > invasive and unportable I scrapped the idea. It would involve a lot of > copy-pasting of various python utilities and classes just to re-create > the same infrastructure, and for extremely little benefit. Nah. > > Just boldly void the warranty instead, while I try to follow up on > https://bugs.python.org/issue43232 Bummer that we have to do that, but at least you are documenting the problems and pursuing a remedy upstream. > > Signed-off-by: John Snow > --- > python/qemu/aqmp/qmp_client.py | 22 ++++++++++++++++++++++ > 1 file changed, 22 insertions(+) > > diff --git a/python/qemu/aqmp/qmp_client.py b/python/qemu/aqmp/qmp_client.py > index d2ad7459f9f..f987da02eb0 100644 > --- a/python/qemu/aqmp/qmp_client.py > +++ b/python/qemu/aqmp/qmp_client.py > @@ -9,6 +9,8 @@ > > import asyncio > import logging > +import socket > +import struct > from typing import ( > Dict, > List, > @@ -624,3 +626,23 @@ async def execute(self, cmd: str, > """ > msg = self.make_execute_msg(cmd, arguments, oob=oob) > return await self.execute_msg(msg) > + > + @upper_half > + @require(Runstate.RUNNING) > + def send_fd_scm(self, fd: int) -> None: > + """ > + Send a file descriptor to the remote via SCM_RIGHTS. > + """ > + assert self._writer is not None > + sock = self._writer.transport.get_extra_info('socket') > + > + if sock.family != socket.AF_UNIX: > + raise AQMPError("Sending file descriptors requires a UNIX socket.") > + > + # Void the warranty sticker. > + # Access to sendmsg in asyncio is scheduled for removal in Python 3.11. > + sock = sock._sock # pylint: disable=protected-access > + sock.sendmsg( > + [b' '], > + [(socket.SOL_SOCKET, socket.SCM_RIGHTS, struct.pack('@i', fd))] > + ) Reviewed-by: Eric Blake -- Eric Blake, Principal Software Engineer Red Hat, Inc. +1-919-301-3266 Virtualization: qemu.org | libvirt.org