Message-ID: <53D84749.6060601@...1926...> Date: Wed, 30 Jul 2014 03:15:53 +0200 From: Julien Muchembled MIME-Version: 1.0 References: <1406654929-6079-1-git-send-email-jm@...1926...> <20140729185713.GX1118@...1296...> <53D803BE.1040500@...1926...> <20140729210527.GY1118@...1296...> In-Reply-To: <20140729210527.GY1118@...1296...> Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="GM5gRS5NxsPM7dNFJFRWxm3rpbOnC5mV4" Subject: Re: [Openvpn-devel] [PATCH] Fix --mtu-disc option with IPv6 transport List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Gert Doering Cc: openvpn-devel@lists.sourceforge.net This is an OpenPGP/MIME signed message (RFC 4880 and 3156) --GM5gRS5NxsPM7dNFJFRWxm3rpbOnC5mV4 Content-Type: text/plain; charset="ISO-8859-1" Content-Transfer-Encoding: quoted-printable Le 07/29/14 23:05, Gert Doering a =E9crit : >> For example: >> A --[mtu=3D1500]-- B --[mtu=3D1400]-- C >> >> Given a UDP6 socket on A with IPV6_MTU_DISCOVER=3DIP_PMTUDISC_DO, >> sendto(1452 bytes, B) will succeed >> but sendto(1452 bytes, C) will return EMSGSIZE (except for the first sen= d to C) >> Yes, at some point, there are icmp packets. >=20 > So (being lazy again, sorry) how is the maximum message size communicated > back to OpenVPN? Ancilliary data again? ICMP packets contains the size and ping/ping6 even reports it (this is real= example with mtu=3D1433 between B & C): # ping6 -c 1 -M do -s 1452 B PING B (...) 1452 data bytes 1460 bytes from B: icmp_seq=3D1 ttl=3D255 time=3D0.430 ms # ping6 -c 1 -M do -s 1454 B PING B(...) 1454 data bytes --GM5gRS5NxsPM7dNFJFRWxm3rpbOnC5mV4--