From owner-freebsd-net Wed Mar 22 9: 8:55 2000 Delivered-To: freebsd-net@freebsd.org Received: from gw.errno.com (node-d1d4bd7a.powerinter.net [209.212.189.122]) by hub.freebsd.org (Postfix) with ESMTP id EAC6B37B9F8 for ; Wed, 22 Mar 2000 09:08:49 -0800 (PST) (envelope-from sam@errno.com) Received: from MELANGE (melange.errno.com [209.212.166.36]) by gw.errno.com (8.9.0/8.9.0) with SMTP id JAA10023; Wed, 22 Mar 2000 09:04:18 -0800 (PST) Message-ID: <005301bf9420$a53ebdc0$0132a8c0@MELANGE> From: "Sam Leffler" To: , "C. Stephen Gunn" References: <200003220239.VAA01543@dustdevil.waterspout.com> Subject: Re: Trimming ether_header before ether_input() Date: Wed, 22 Mar 2000 09:04:07 -0800 MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 5.00.2919.6700 X-MimeOLE: Produced By Microsoft MimeOLE V5.00.2919.6700 Sender: owner-freebsd-net@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.org ----- Original Message ----- From: "C. Stephen Gunn" To: Sent: Tuesday, March 21, 2000 6:39 PM Subject: Trimming ether_header before ether_input() > In my wanderings through the FreeBSD networking code, I've noticed > something peculiar in all ethernet drivers. Is there a historical > reason that the ethernet header is trimmed from the mbuf chain > before its passed to ether_input()? > > I can only assume that (at one time) there were ethernet devices > (back in the IMP days) that handed you the link header and the > payload in separate buffers. > When all this code was written there was a link layer encapsulation called a trailer protocol that placed the Ethernet header at the end of the packet. I think it's described in the "real BSD book" (the 4.2 one, not a later one :-)); if not there is an RFC that describes it. Sam To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-net" in the body of the message