Path: csiph.com!v102.xanadu-bbs.net!xanadu-bbs.net!feeder.erje.net!eu.feeder.erje.net!eternal-september.org!feeder.eternal-september.org!mx02.eternal-september.org!.POSTED!not-for-mail From: D Finnigan Newsgroups: comp.sys.apple2.programmer Subject: Re: Resolved!, was Re: Uthernet receive error: bytes swapped Date: Fri, 6 Mar 2015 00:30:23 +0000 (UTC) Organization: Mac GUI Lines: 23 Message-ID: References: <27094031-e746-4e9d-a0a4-e81ef6f82c44@googlegroups.com> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Injection-Date: Fri, 6 Mar 2015 00:30:23 +0000 (UTC) Injection-Info: mx02.eternal-september.org; posting-host="ac9e0e4d7dd3957fb97803ee6801bab8"; logging-data="31354"; mail-complaints-to="abuse@eternal-september.org"; posting-account="U2FsdGVkX18AEwulaxapPQgi56Fr2kiO" User-Agent: Mac GUI Usenet In-Reply-To: <27094031-e746-4e9d-a0a4-e81ef6f82c44@googlegroups.com> Cancel-Lock: sha1:WxGM1djUgIb2TowCToqpBMKGizs= Xref: csiph.com comp.sys.apple2.programmer:1548 gids.rs wrote: >> What's incredible is how the checksum routine still managed to give >> correct >> results in so many cases. That's definitely one of those tricky bugs. >> > > > Maybe not so incredible. Wouldn't 10 bytes of code followed by 10 bytes > of > 0's give the same checksum? I don't know. This IP checksum routine was supposed to only cover the 20 byte IP header. If it was running twice as long, it was either checksumming a bit of the data payload, or something else. I'm not really interested in looking into exactly what it was doing, just surprised that it was giving correct results in its broken state. -- ]DF$ Apple II Book: http://macgui.com/newa2guide/ Usenet: http://macgui.com/usenet/ <-- get posts by email! Apple II Web & Blog hosting: http://a2hq.com/