Date: Wed, 07 Mar 2001 09:40:34 -0500 From: "Louis A. Mamakos" <louie@TransSys.COM> To: Ruslan Ermilov <ru@FreeBSD.ORG> Cc: Jonathan Lemon <jlemon@flugsvamp.com>, Jonathan Lemon <jlemon@FreeBSD.ORG>, net@FreeBSD.ORG Subject: Re: Delayed checksums commit broke UDP checksum calculation Message-ID: <200103071440.f27EeYa99809@whizzo.transsys.com> In-Reply-To: Your message of "Wed, 07 Mar 2001 12:31:56 %2B0200." <20010307123156.A19829@sunbay.com> References: <20001116120936.A45755@sunbay.com> <20001116091954.A19895@prism.flugsvamp.com> <20010307123156.A19829@sunbay.com>
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> > So that the same logic applies to TCP packets as well. Currently, we > > can send a TCP packet with a checksum of 0, which is legal. Of possible > > interest is that Linux doesn't do this; they alwyas send a non-zero > > checksum in the TCP case, if a checksum was computed. > > > Hmm, but why would we do this for TCP? This violates RFC 793. > AFAIK, only UDP checksums are special. 0x0000 and 0xFFFF are both 16-bit 1's complement representations of zero, so you could send either and still have the remote TCP validate the checksum. To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-net" in the body of the message
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