From owner-freebsd-net@FreeBSD.ORG Sun Apr 29 16:25:24 2012 Return-Path: Delivered-To: freebsd-net@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [69.147.83.52]) by hub.freebsd.org (Postfix) with ESMTP id 5C71C1065689 for ; Sun, 29 Apr 2012 16:25:24 +0000 (UTC) (envelope-from lev@FreeBSD.org) Received: from onlyone.friendlyhosting.spb.ru (onlyone.friendlyhosting.spb.ru [46.4.40.135]) by mx1.freebsd.org (Postfix) with ESMTP id 184AC8FC12 for ; Sun, 29 Apr 2012 16:25:24 +0000 (UTC) Received: from lion.home.serebryakov.spb.ru (89.112.15.178.pppoe.eltel.net [89.112.15.178]) (Authenticated sender: lev@serebryakov.spb.ru) by onlyone.friendlyhosting.spb.ru (Postfix) with ESMTPA id 41A724AC32; Sun, 29 Apr 2012 20:25:23 +0400 (MSK) Date: Sun, 29 Apr 2012 20:25:22 +0400 From: Lev Serebryakov Organization: FreeBSD Project X-Priority: 3 (Normal) Message-ID: <882834004.20120429202522@serebryakov.spb.ru> To: Seth Mos In-Reply-To: <2vl4qolvow9yktrrufp56o2n.1335716454950@email.android.com> References: <2vl4qolvow9yktrrufp56o2n.1335716454950@email.android.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Cc: freebsd-net@freebsd.org Subject: Re: IPv6 MTU discrovery -- how should it work? X-BeenThere: freebsd-net@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list Reply-To: lev@FreeBSD.org List-Id: Networking and TCP/IP with FreeBSD List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sun, 29 Apr 2012 16:25:24 -0000 Hello, Seth. You wrote 29 =D0=B0=D0=BF=D1=80=D0=B5=D0=BB=D1=8F 2012 =D0=B3., 20:20:54: SM> Make sure you do not block icmp6. Or atleast make sure that SM> unreachable and toobig packets come through even if you do not want ech= o. icmp6 enabled in firewall. It seems to be problem in "gif" interface, which has this words in BUGS section in man page: If the outer protocol is IPv4, gif does not try to perform path MTU di= s- covery for the encapsulated packet (DF bit is set to 0). If the outer protocol is IPv6, path MTU discovery for encapsulated pac= k- ets may affect communication over the interface. The first bigger-tha= n- pmtu packet may be lost. To avoid the problem, you may want to set the interface MTU for gif to 1240 or smaller, when the outer header is IPv6 and the inner header is IPv4. I have MTU 1460 on my "outer" interface (it is PPPoE connection to my IPv4 provider), and gif0 doesn't allow me to set mtu 1240 on it. --=20 // Black Lion AKA Lev Serebryakov