From owner-freebsd-questions@FreeBSD.ORG Thu Jun 19 14:33:14 2003 Return-Path: Delivered-To: freebsd-questions@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id 426FD37B401 for ; Thu, 19 Jun 2003 14:33:14 -0700 (PDT) Received: from mailgw2a.lmco.com (mailgw2a.lmco.com [192.91.147.7]) by mx1.FreeBSD.org (Postfix) with ESMTP id 47D5143FAF for ; Thu, 19 Jun 2003 14:33:13 -0700 (PDT) (envelope-from koroush.saraf@lmco.com) Received: from emss01g01.ems.lmco.com ([129.197.181.54]) by mailgw2a.lmco.com (8.11.6p2/8.11.6) with ESMTP id h5JLXCv19645 for ; Thu, 19 Jun 2003 17:33:12 -0400 (EDT) Received: from CONVERSION-DAEMON.lmco.com by lmco.com (PMDF V6.1-1 #40643) id <0HGQ00101ZASGL@lmco.com> for freebsd-questions@freebsd.org; Thu, 19 Jun 2003 14:33:10 -0700 (PDT) Received: from BSDWIN2KKOROUSH ([129.197.244.4]) by lmco.com (PMDF V6.1-1 #40643) with SMTP id <0HGQ003SMYUZ4G@lmco.com> for freebsd-questions@freebsd.org; Thu, 19 Jun 2003 14:11:23 -0700 (PDT) Date: Thu, 19 Jun 2003 14:10:58 -0700 From: Koroush Saraf To: "Saraf, Koroush (N-Norman SubSystems)" , freebsd-questions@freebsd.org Message-id: <00e601c336a7$479325d0$04f4c581@BSDWIN2KKOROUSH> MIME-version: 1.0 X-MIMEOLE: Produced By Microsoft MimeOLE V6.00.2800.1165 X-Mailer: Microsoft Outlook Express 6.00.2800.1158 X-Priority: 3 X-MSMail-priority: Normal References: <00a001c33680$68827600$04f4c581@BSDWIN2KKOROUSH> Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: 7BIT X-Content-Filtered-By: Mailman/MimeDel 2.1.1 Subject: Re: MTU Path Discovery Problem X-BeenThere: freebsd-questions@freebsd.org X-Mailman-Version: 2.1.1 Precedence: list List-Id: User questions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 19 Jun 2003 21:33:14 -0000 PMTUD Black Hole ProblemCode Problem? Is this a code problem in ip_input.c, This code is from FreeBSD 4.8 that I just installed on my computers. ip_forward ? It looks to me like case EMSGSIZE can never be reached. Is this breaking mtu path discovery responses ? ip_forward(struct mbuf *m, int srcrt, struct sockaddr_in *next_hop) switch (error) { case 0: /* forwarded, but need redirect */ /* type, code set above */ break; case ENETUNREACH: /* shouldn't happen, checked above */ case EHOSTUNREACH: case ENETDOWN: case EHOSTDOWN: default: type = ICMP_UNREACH; code = ICMP_UNREACH_HOST; break; case EMSGSIZE: type = ICMP_UNREACH; code = ICMP_UNREACH_NEEDFRAG; ----- Original Message ----- From: Saraf, Koroush (N-Norman SubSystems) To: freebsd-questions@freebsd.org Sent: Thursday, June 19, 2003 9:32 AM Subject: PMTUD Black Hole Problem Hi All, I have the following network in the lap WINXP <---mtu1500--->FREEBSD4.4<---mtu1280(gif tunnel--->FREEBSD4.4<---mtu1500--->WINXP The BSD computers are setup as gateway routers. As you might see from diagram above, the MTU of the link between the two BSD computers is 1280Bytes because of a tunnel. When I try to transfer a file between the XP endpoints, the PMTUD goes off by sending a 1514B packet to the other end with the Don't fragment bit set. However this packet never generates the ICMP unreachable message back to the XP box during Path MTU discovery. So that's why I have concluded that the BSD router is the black hole. Now I would like to know how to make my BSD router to participate in the MTU discovery. Changing the MTU of the windows computers is not an option for me. Also please note that the BSD computers only have one NIC interface, and the network is logically sperate but physically all connected to a switch, so playing with the MTU of the interface connecting the BSD computers is not an option either. I hope that this is a known problem and easy to fix and thanks for taking the time to respond. ~koroush _______________________________________________ freebsd-questions@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-questions To unsubscribe, send any mail to "freebsd-questions-unsubscribe@freebsd.org"