Date: Mon, 10 Sep 2001 12:43:15 -0700 (PDT) From: Julian Elischer <julian@elischer.org> To: Jonathan Lemon <jlemon@flugsvamp.com> Cc: kent@erix.ericsson.se, hackers@freebsd.org Subject: Re: How to force small TCP packets? Message-ID: <Pine.BSF.4.21.0109101242140.48807-100000@InterJet.elischer.org> In-Reply-To: <200109101817.f8AIH7t11927@prism.flugsvamp.com>
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just set the MTU on the sender to something really small (120 byres) On Mon, 10 Sep 2001, Jonathan Lemon wrote: > In article <local.mail.freebsd-hackers/d2heubk4p2.fsf@erix.ericsson.se> you write: > > > >bright@mu.org (Alfred Perlstein) writes: > >> there's a setsockopt for this called TCP_NODELAY in netinet/tcp.h. > >> > >> you should read further into stevens before posting such questions. > > > >I seem to have expressed myself really bad :-( I want to debug an > >application. We have had code that broke only occasionally on a > >specific Linux version under heavy load. I want to detect bad code > >like that and had hoped that some FreeBSD hackers had some tricks how > >to use kernel configuration to do that. > > > >If application A do a write like > > > > write(socket, buf, 100); > > > >and application B read this like > > > > read(socket, buf, 100); > > > >without checking the result from the read operation, then this code > >will probably work 99.9999% of the time. But if I could force the > >kernel to pass data from a socket on to the application say one byte > >at the time then this code will break 100% of the time. This makes > >finding these problems more easy. > > > >This is highly simplified example, else I could just grep the sources > >for all calls to read() and manually inspect the code. The data is > >passed on to other parts of the system using message queues. > > > >But using the kernel to debug user applications like this was probably > >a stupid idea. I'm sorry for posting a question to this group without > >the proper knowledge wasting your time, > > One thing you might want to try doing is to write your own read() > function and link against that. Your modified version could then > replace the nbytes value with something smaller, for debugging purposes. > -- > Jonathan > > To Unsubscribe: send mail to majordomo@FreeBSD.org > with "unsubscribe freebsd-hackers" in the body of the message > To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message
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