From mboxrd@z Thu Jan 1 00:00:00 1970 From: Chris Friesen Subject: unexpected TCP behaviour when deleting local IP addresses Date: Tue, 16 Oct 2012 15:12:13 -0600 Message-ID: <507DCDAD.7030209@mail.usask.ca> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit To: netdev Return-path: Received: from idcmail-mo2no.shaw.ca ([64.59.134.9]:20775 "EHLO idcmail-mo2no.shaw.ca" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753890Ab2JPVVv (ORCPT ); Tue, 16 Oct 2012 17:21:51 -0400 Sender: netdev-owner@vger.kernel.org List-ID: I'm seeing some strange behaviour with local TCP connections. The scenario goes as follows: 1) create new IP address and assign to eth device 2) TCP server starts listening on that IP address 3) TCP client connects to server 4) remove new IP address 5) kill server with ctrl-C. At this point it appears that because the address was removed the shutdown message isn't processed properly. netstat shows the server socket as FIN_WAIT1, but the client socket is still ESTABLISHED. 6) client writes to the connected socket (this passes with no error) 7) client waits for response from server, and waits forever or until keepalive expires This was originally seen on 2.6.27, but I've verified it on 2.6.35. I'll see about trying it on current git. Is the waiting forever in step 7 a bug, or is this legitimate TCP behaviour since the server was basically shut down uncleanly? If we don't remove the address in step 4, then step 5 results in the server socket going to FIN_WAIT2 and the client socket going to CLOSE_WAIT and step 7 returns right away with zero bytes. In the "remove IP address" case I would expect step 6 to cause some sort of error since the IP address no longer exists. The interesting thing is that if you do this sort of scenario with the client and server on different hosts then you get a "no route to host" error at step 6. Curious how this is supposed to work... Chris