From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andi Kleen Subject: No pmtu probing on retransmits? Date: Sun, 3 Feb 2008 13:37:19 +0100 Message-ID: <20080203123719.GA3323@basil.nowhere.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii To: jheffner@psc.edu, netdev@vger.kernel.org Return-path: Received: from smtp-out04.alice-dsl.net ([88.44.63.6]:8079 "EHLO smtp-out04.alice-dsl.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S935844AbYBCMhg (ORCPT ); Sun, 3 Feb 2008 07:37:36 -0500 Content-Disposition: inline Sender: netdev-owner@vger.kernel.org List-ID: Hallo, While looking for something else in tcp_output.c I noticed that MTU probing seems to be only done in tcp_write_xmit (when packets come directly from process context), but not via the timer driven timer retransmit path (tcp_retransmit_skb). Is that intentional? It looks quite weird. I would normally assume PMTU blackholes get usually detected on retransmit timeouts. Or do I miss something? You seem to have assumed interrupt context at least because tcp_mtu_probe() uses GFP_ATOMIC which is only needed for interrupts. Currently it is only called in process context I think. -Andi