Date: Thu, 8 Mar 2001 16:32:08 -0600 From: Jonathan Lemon <jlemon@flugsvamp.com> To: Alfred Perlstein <bright@wintelcom.net>, g@flugsvamp.com Cc: Jonathan Lemon <jlemon@flugsvamp.com>, Wietse Venema <wietse@porcupine.org>, itojun@iijlab.net, Arjan.deVet@adv.iae.nl, net@FreeBSD.ORG, postfix-users@postfix.org Subject: Re: [itojun@iijlab.net: accept(2) behavior with tcp RST right after handshake] Message-ID: <20010308163208.C78851@prism.flugsvamp.com> In-Reply-To: <20010308143022.E18351@fw.wintelcom.net> References: <20010308095759.S41963@prism.flugsvamp.com> <20010308180048.CC09DBC06D@spike.porcupine.org> <20010308161611.B78851@prism.flugsvamp.com> <20010308143022.E18351@fw.wintelcom.net>
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On Thu, Mar 08, 2001 at 02:30:23PM -0800, Alfred Perlstein wrote: > * Jonathan Lemon <jlemon@flugsvamp.com> [010308 14:19] wrote: > > On Thu, Mar 08, 2001 at 01:00:48PM -0500, Wietse Venema wrote: > > > Jonathan Lemon: > > > > On Thu, Mar 08, 2001 at 10:38:17AM -0500, Wietse Venema wrote: > > > > > If the result of connect() write() close() depends on whether > > > > > accept() happens after or before close(), then the behavior is > > > > > broken. The client has received a successful return from write() > > > > > and close(). The system is not supposed to lose the data, period. > > > > > > > > What you seem to be missing here is that the behavior described > > > > above is ONLY specific to UNIX-DOMAIN sockets. The description > > > > above is generally (but not always) true for the TCP/IP protocol. > > > > > > The problem is observed with UNIX-domain sockets. > > > > > > > Data CAN be lost if the TCP connection is RST. It has nothing to > > > > do with the ordering of accept() with respect to close(). > > > > > > Please educate me: how would RST come into this discussion at all? > > > The client does connect() write() close(), there is no forced > > > connection termination involved at all. > > > > Under normal circumstances, a connect(), write(), close() call > > should work. However, the code that was added was to handle the > > abnormal cases from the server's point of view. > > Just make sure your patch is ok with the unix file descriptor > passing garbage collection code, it seems to rely on socket state > to get things right. It doesn't change any of the socket state, nor does it touch the SS_NOFDREF flag, so the gc algorithm should be okay. Actually, all I'm doing here is pushing the decision down to each protocol, rather than short-circuiting the test at the socket layer. -- Jonathan To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-net" in the body of the message
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