Date: Wed, 24 Oct 2012 18:24:30 +0200 From: Harald Schmalzbauer <h.schmalzbauer@omnilan.de> To: Jeremy Chadwick <jdc@koitsu.org> Cc: adrian@freebsd.org, freebsd-stable@freebsd.org Subject: Re: every 2nd echo-request malformed when ping -s >4067 Message-ID: <5088163E.2090506@omnilan.de> In-Reply-To: <20121024154017.GA3167@icarus.home.lan> References: <20121024154017.GA3167@icarus.home.lan>
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This is an OpenPGP/MIME signed message (RFC 2440 and 3156) --------------enig3B546E6D0DDE8702202A5B74 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable schrieb Jeremy Chadwick am 24.10.2012 17:40 (localtime): > (Please keep me CC'd as I'm not subscribed) > > Regarding: > > http://lists.freebsd.org/pipermail/freebsd-stable/2012-October/070239.h= tml > > tcpdump -x is not helpful here. tcpdump -xx would be. > > tcpdump -x dumps the *payload* portion of the packet, while -xx dumps > everything (all headers/protocol data included). > > The reason I say -xx would be helpful is because of this: > >> 2nd: 12:21:10.052891 IP 10.5.49.126 > 10.5.49.65: icmp >> 0x0000: 4500 1000 0f2d 0040 4001 e4c7 0a05 317e > The ICMP code/type and related header data is not being decoded > correctly, or is being *encoded* incorrectly. I can't tell because all= > that's shown there is the payload!=20 Hmm, if I understand things right, there's only the link-level-header missing, meaning the ethernet adresses. Not the IP-header. Verified that: 1st: 16:03:08.963292 IP 10.5.49.126 > 10.5.49.65: ICMP echo request, id 30477, seq 0, length 4076 000c 29f1 8424 90e2 ba18 f885 0800 2nd: 16:03:09.968454 IP 10.5.49.126 > 10.5.49.65: icmp 000c 29f1 8424 90e2 ba18 f885 0800 Since the link-level-header is identical, the problem must be later and the former dump should be valid. That's easily reproducable everywhere, since lo0 has mtu 16384, so just ' ping -D -s 4068 127.0.0.1 '. Thanks, -Harry --------------enig3B546E6D0DDE8702202A5B74 Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.18 (FreeBSD) iEYEARECAAYFAlCIFj4ACgkQLDqVQ9VXb8hWnwCfcfDpTztBpewIDY3io5zTsidS q/8AoJCYPjPCnDPmThmjfLYZKa+/7f7r =aPBZ -----END PGP SIGNATURE----- --------------enig3B546E6D0DDE8702202A5B74--
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