Date: Sun, 17 Dec 2006 15:52:49 -0500 From: Kris Kennaway <kris@obsecurity.org> To: Andrew Pantyukhin <infofarmer@FreeBSD.org> Cc: current@freebsd.org, David Xu <davidxu@freebsd.org> Subject: Re: vge(4) bad checksum Message-ID: <20061217205249.GA73132@xor.obsecurity.org> In-Reply-To: <cb5206420612171246q54ac783h1fd9d420b80ba84c@mail.gmail.com> References: <cb5206420612171246q54ac783h1fd9d420b80ba84c@mail.gmail.com>
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--4Ckj6UjgE2iN1+kY Content-Type: text/plain; charset=us-ascii Content-Disposition: inline On Sun, Dec 17, 2006 at 11:46:24PM +0300, Andrew Pantyukhin wrote: > I'm not sure what it's all about, but with today's > current whatever goes out my vge interface (icmp/ > tcp/udp) has bad checksum: This is a FAQ; it's probably using hardware checksum offloading. Since the packet passed down to the NIC does not yet have the checksum computed, it looks to tcpdump like the checksum is incorrect. However if you look at the packet actually transmitted by the NIC (e.g. tcpdump on another host), you'll see that it has the correct checksum. Kris --4Ckj6UjgE2iN1+kY Content-Type: application/pgp-signature Content-Disposition: inline -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.6 (FreeBSD) iD8DBQFFha4hWry0BWjoQKURAkPDAKDv6DDEkCGdSi+Hq/RVdTedthSfjACgvVQW Yd27Rb3UV1qeJtEtnwk3Z/g= =OnaB -----END PGP SIGNATURE----- --4Ckj6UjgE2iN1+kY--
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