From owner-freebsd-hackers Fri Jun 8 5:42:50 2001 Delivered-To: freebsd-hackers@freebsd.org Received: from assaris.sics.se (assaris.sics.se [193.10.66.234]) by hub.freebsd.org (Postfix) with ESMTP id 89F9137B401; Fri, 8 Jun 2001 05:42:44 -0700 (PDT) (envelope-from assar@assaris.sics.se) Received: (from assar@localhost) by assaris.sics.se (8.9.3/8.9.3) id OAA63084; Fri, 8 Jun 2001 14:42:47 +0200 (CEST) (envelope-from assar) To: Ruslan Ermilov Cc: tlambert2@mindspring.com, freebsd-hackers@FreeBSD.ORG Subject: Re: How to disable software TCP checksumming? References: <20010529144114.I19771@luke.immure.com> <20010529221107.C49875@skriver.dk> <20010529155212.M19771@luke.immure.com> <20010530045200.A1031@hades.hell.gr> <20010529235215.A60177@luke.immure.com> <20010530085155.B24096@Odin.AC.HMC.Edu> <200105310204.f4V248n15260@whizzo.transsys.com> <200106070549.WAA06248@windsor.research.att.com> <3B208F11.87722148@mindspring.com> <5lk82ntb0o.fsf@assaris.sics.se> <20010608153544.C87737@sunbay.com> From: Assar Westerlund Date: 08 Jun 2001 14:42:46 +0200 In-Reply-To: Ruslan Ermilov's message of "Fri, 8 Jun 2001 15:35:44 +0300" Message-ID: <5lofrzrvll.fsf@assaris.sics.se> Lines: 33 User-Agent: Gnus/5.070098 (Pterodactyl Gnus v0.98) Emacs/20.6 MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Sender: owner-freebsd-hackers@FreeBSD.ORG Precedence: bulk List-ID: List-Archive: (Web Archive) List-Help: (List Instructions) List-Subscribe: List-Unsubscribe: X-Loop: FreeBSD.ORG Ruslan Ermilov writes: > On Fri, Jun 08, 2001 at 02:24:23PM +0200, Assar Westerlund wrote: > > Terry Lambert writes: > > > This all came from IP headers being 14 bytes long, instead > > > of 16. > > > > Hu? An IPv4 header (not including options) is 20 bytes long. > > > Terry meant the length of an IPv4 header up to but not including > the checksum field. I'm confused. From rfc791: 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |Version| IHL |Type of Service| Total Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Identification |Flags| Fragment Offset | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Time to Live | Protocol | Header Checksum | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Source Address | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Destination Address | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Options | Padding | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Which to me says that an IP header up to but not including the checksum is 10 bytes? /assar To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message