From owner-freebsd-bugs Fri Sep 6 11:10:12 2002 Delivered-To: freebsd-bugs@hub.freebsd.org Received: from mx1.FreeBSD.org (mx1.FreeBSD.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id 4606637B401 for ; Fri, 6 Sep 2002 11:10:04 -0700 (PDT) Received: from freefall.freebsd.org (freefall.FreeBSD.org [216.136.204.21]) by mx1.FreeBSD.org (Postfix) with ESMTP id C279E43E4A for ; Fri, 6 Sep 2002 11:10:03 -0700 (PDT) (envelope-from gnats@FreeBSD.org) Received: from freefall.freebsd.org (gnats@localhost [127.0.0.1]) by freefall.freebsd.org (8.12.4/8.12.4) with ESMTP id g86IA3JU002792 for ; Fri, 6 Sep 2002 11:10:03 -0700 (PDT) (envelope-from gnats@freefall.freebsd.org) Received: (from gnats@localhost) by freefall.freebsd.org (8.12.4/8.12.4/Submit) id g86IA3RY002791; Fri, 6 Sep 2002 11:10:03 -0700 (PDT) Date: Fri, 6 Sep 2002 11:10:03 -0700 (PDT) Message-Id: <200209061810.g86IA3RY002791@freefall.freebsd.org> To: freebsd-bugs@FreeBSD.org Cc: From: Jeff Behl Subject: Re: kern/42137: Path MTU broken - initial too-large packet continuously resent Reply-To: Jeff Behl Sender: owner-freebsd-bugs@FreeBSD.ORG Precedence: bulk List-ID: List-Archive: (Web Archive) List-Help: (List Instructions) List-Subscribe: List-Unsubscribe: X-Loop: FreeBSD.org The following reply was made to PR kern/42137; it has been noted by GNATS. From: Jeff Behl To: Martin Kaeske Cc: freebsd-gnats-submit@FreeBSD.org, Steve Francis Subject: Re: kern/42137: Path MTU broken - initial too-large packet continuously resent Date: Fri, 06 Sep 2002 11:07:02 -0700 Actually, it would be our layer two load balancer that is not re-writing the icmps from the router correctly. I was using ethereal to do a inspection of the packets but it doesn't seem to show the sequence number in the tcp header in the icmp. Thanks! I knew it had something to do with this blasted load balancer. This is a foundery serveriron for all who might be interested But in any case, it still doesn't seem to be a 'good idea' for the stack to transmit packets (and keep re-transmitting them) that are above the MTU that it has for a certain host, does it? or is this the only way it makes sense as it would be inefficient to have TCP re-check the MTU on every re-transmitted packet? I'm certaintly no expert in this area... thanks again. Jeff Martin Kaeske wrote: > Hi Jeff, > Thanks for the tcpdump, i think i was able to identify the problem. > As i wrote in the PR tcp_ctlinput() is responsible for calling tcp_mtudisc > but tcp_ctlinput() does not only check src/dst-port it also examines wether > the tcp-sequence number (found in the ICMP-response) is between snd_una (send > unacknowledged) and snd_max (highest number sent). I found out that the > ICMP-responses doesn't contain the correct seq. number, the first two bytes > are correct but the last two aren't. > > So i think it is a router problem (as it was in my case ;). > > HTH > Martin > To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-bugs" in the body of the message