Date: Sun, 24 Dec 2006 00:10:13 -0500 From: Kris Kennaway <kris@obsecurity.org> To: Ruslan Ermilov <ru@FreeBSD.org> Cc: Andrew Pantyukhin <infofarmer@FreeBSD.org>, David Xu <davidxu@FreeBSD.org>, current@FreeBSD.org, Kris Kennaway <kris@obsecurity.org> Subject: Re: vge(4) bad checksum Message-ID: <20061224051013.GA25197@xor.obsecurity.org> In-Reply-To: <20061222080202.GB77429@rambler-co.ru> References: <cb5206420612171246q54ac783h1fd9d420b80ba84c@mail.gmail.com> <20061217205249.GA73132@xor.obsecurity.org> <20061222080202.GB77429@rambler-co.ru>
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--+HP7ph2BbKc20aGI Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Fri, Dec 22, 2006 at 11:02:02AM +0300, Ruslan Ermilov wrote: > Hi, >=20 > On Sun, Dec 17, 2006 at 03:52:49PM -0500, Kris Kennaway wrote: > > 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: > >=20 > > This is a FAQ; it's probably using hardware checksum offloading. > >=20 > > 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. > >=20 > Kris, you probably missed a commit by csjp@ where it was fixed. >=20 > : revision 1.220 > : date: 2006/11/18 23:17:22; author: csjp; state: Exp; lines: +40 -0 > : Currently, drivers that support hardware offload of VLAN tag > : processing are forced to toggle this functionality when the card > : is put in and out of promiscuous mode. The main reason for this > : is because the hardware strips the VLAN tag, making it impossible > : for the tag information to show up in network diagnostic tools like > : tcpdump(1). > : [...] That sounds like an unrelated issue (VLAN tagging, not checksum offloading). Kris --+HP7ph2BbKc20aGI Content-Type: application/pgp-signature Content-Disposition: inline -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.6 (FreeBSD) iD8DBQFFjgu0Wry0BWjoQKURAjDlAKCUlnzxhgPtZM1hVmGzimXlfwx18QCg7U8R k6cpBk7hiETq5MJFQEvrY4Y= =VvHv -----END PGP SIGNATURE----- --+HP7ph2BbKc20aGI--
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