From mboxrd@z Thu Jan 1 00:00:00 1970 From: Stephen Hemminger Subject: Re: why would EPIPE cause socket port to change? Date: Tue, 23 Jan 2007 12:26:52 -0800 Message-ID: <20070123122652.484c05b3@freekitty> References: Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Cc: dean@arctic.org (dean gaudet), netdev@vger.kernel.org Return-path: Received: from smtp.osdl.org ([65.172.181.24]:53478 "EHLO smtp.osdl.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933095AbXAWU3P (ORCPT ); Tue, 23 Jan 2007 15:29:15 -0500 To: Herbert Xu In-Reply-To: Sender: netdev-owner@vger.kernel.org List-Id: netdev.vger.kernel.org On Tue, 23 Jan 2007 16:44:10 +1100 Herbert Xu wrote: > dean gaudet wrote: > > in the test program below the getsockname result on a TCP socket changes > > across a write which produces EPIPE... here's a fragment of the strace: > > > > getsockname(3, {sa_family=AF_INET, sin_port=htons(37636), sin_addr=inet_addr("127.0.0.1")}, [17863593746633850896]) = 0 > > ... > > write(3, "hi!\n", 4) = 4 > > write(3, "hi!\n", 4) = -1 EPIPE (Broken pipe) > > --- SIGPIPE (Broken pipe) @ 0 (0) --- > > getsockname(3, {sa_family=AF_INET, sin_port=htons(59882), sin_addr=inet_addr("127.0.0.1")}, [16927060683038654480]) = 0 > > > > why does the port# change? this is on 2.6.19.1. > > Prior to the last write, the socket entered the CLOSED state meaning > that the old port is no longer allocated to it. As a result, the > last write operates on an unconnected socket which causes a new local > port to be allocated as an autobind. It then fails because the socket > is still not connected. Why does write cause an autobind? One would think that on a SOCK_STREAM socket, the write should just fail with ENOTCONN > > So any attempt to run getsockname after an error on the socket is > simply buggy. > > Cheers, -- Stephen Hemminger