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[79.34.249.199]) by smtp.gmail.com with ESMTPSA id n186sm1409710wmn.22.2021.03.12.01.01.06 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 12 Mar 2021 01:01:06 -0800 (PST) Date: Fri, 12 Mar 2021 10:01:04 +0100 From: Stefano Garzarella To: Stefan Hajnoczi Subject: Re: [PATCH] sockets: update SOCKET_ADDRESS_TYPE_FD listen(2) backlog Message-ID: <20210312090104.52xemd7umyawotnc@steredhat> References: <20210310173004.420190-1-stefanha@redhat.com> MIME-Version: 1.0 In-Reply-To: <20210310173004.420190-1-stefanha@redhat.com> Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=sgarzare@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=us-ascii; format=flowed Content-Disposition: inline Received-SPF: pass client-ip=170.10.133.124; envelope-from=sgarzare@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -29 X-Spam_score: -3.0 X-Spam_bar: --- X-Spam_report: (-3.0 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.25, 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: "Richard W . M . Jones" , Gerd Hoffmann , Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= , qemu-devel@nongnu.org, Juan Quintela Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Wed, Mar 10, 2021 at 05:30:04PM +0000, Stefan Hajnoczi wrote: >socket_get_fd() fails with the error "socket_get_fd: too many >connections" if the given listen backlog value is not 1. > >Not all callers set the backlog to 1. For example, commit >582d4210eb2f2ab5baac328fe4b479cd86da1647 ("qemu-nbd: Use SOMAXCONN for >socket listen() backlog") uses SOMAXCONN. This will always fail with in >socket_get_fd(). > >This patch calls listen(2) on the fd to update the backlog value. The >socket may already be in the listen state. I have tested that this works >on Linux 5.10 and macOS Catalina. Confirmed also from the listen(2) man page of FreeBSD: "A subsequent listen() system call on the listening socket allows the caller to change the maximum queue length using a new backlog argument." > >As a bonus this allows us to detect when the fd cannot listen. Now we'll >be able to catch unbound or connected fds in socket_listen(). > >Drop the num argument from socket_get_fd() since this function is also >called by socket_connect() where a listen backlog value does not make >sense. > >Fixes: e5b6353cf25c99c3f08bf51e29933352f7140e8f ("socket: Add backlog parameter to socket_listen") >Reported-by: Richard W.M. Jones >Cc: Juan Quintela >Cc: Eric Blake >Signed-off-by: Stefan Hajnoczi >--- > util/qemu-sockets.c | 29 ++++++++++++++++++++++------- > 1 file changed, 22 insertions(+), 7 deletions(-) Reviewed-by: Stefano Garzarella Thanks, Stefano