From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Mon, 20 Aug 2001 14:51:14 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Mon, 20 Aug 2001 14:51:04 -0400 Received: from UNASSIGNED.SKYNETWEB.COM ([64.23.55.10]:14377 "HELO mx.webmailstation.com") by vger.kernel.org with SMTP id convert rfc822-to-8bit; Mon, 20 Aug 2001 14:50:51 -0400 Content-Type: text/plain; charset=US-ASCII From: Denis Perchine Organization: AcademSoft To: Alexey Kuznetsov Subject: Re: Problems with kernel-2.2.19-6.2.7 from RH update for 6.2 Date: Tue, 21 Aug 2001 01:52:04 +0700 X-Mailer: KMail [version 1.3.5] In-Reply-To: <200108200211.GAA00342@mops.inr.ac.ru> In-Reply-To: <200108200211.GAA00342@mops.inr.ac.ru> Cc: linux-kernel@vger.kernel.org MIME-Version: 1.0 Content-Transfer-Encoding: 7BIT Message-Id: <20010820155450.777C91FD74@mx.webmailstation.com> Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Monday 20 August 2001 09:11, you wrote: > Hello! > > > socket(PF_INET, SOCK_STREAM, IPPROTO_IP) = 40 > > fcntl(40, F_GETFL) = 0x2 (flags O_RDWR) > > fcntl(40, F_SETFL, O_RDWR|O_NONBLOCK) = 0 > > setsockopt(40, SOL_SOCKET, SO_LINGER, [1], 8) = 0 > > connect(40, {sin_family=AF_INET, sin_port=htons(2030), > > sin_addr=inet_addr("127.0.0.1")}}, 16) = -1 EINPROGRESS (Operation now in > > progress) > > select(41, NULL, [40], NULL, {180, 0}) = 1 (out [40], left {180, 0}) > > getsockopt(40, SOL_SOCKET, SO_ERROR, [0], [4]) = 0 > > select(41, [40], NULL, NULL, {180, 0}) = 1 (in [40], left {175, 550000}) > > ioctl(4, FIONREAD, [0]) = 0 > > select(41, [40], NULL, NULL, {180, 0}) = 1 (in [40], left {180, 0}) > > recv(4, 0x806aa28, 1, 0x4000) = -1 EAGAIN (Resource temporarily > > unavailable) > > > > As far as you can see select say that socket is writable after connect. > > This mean that connection is completed... But later before read we do > > select on read, and get OK. But recv fails with EAGAIN. This situation is > > repeated constantly. The program stucks in the loop trying to connect, > > but fails. > > > > Any ideas what can this be? > F.e. this can be recv() on wrong descriptor, which is seen from strace > above. > > :-) Oups... I should sleep for at least 9 hours when I wrote it. :-(( It looks like a bug. > BTW why do you use funny getsockopt instead of canonical non-blocking > connect? Hmmm... If I know what canonical non-blocking connect is, I would use it I think... Also I use getsockopt to get an error. I set non-blocking with fcntl. > Does standard way have some drawbacks or it is just legal desire > to "think different"? :-) No. Just usual lameness. I read lot of FAQs, play with the code, and this is the combination which works. Actually thttpd also uses this (if I am not mistaken). > The question is very interesting: it is big > puzzle for me what does motivate people to invent such strange combinations > of selct/ioctl/getsockopt (f.e. qmail did another bizarre thing: > getpeername() in the place where you use getsockopt(), so strace > looks like a shizophrenic dialogue to itself: "I am Bob!", ... > "Am I really Bob?" ... "Am I still Bob?" and so on for 3 minutes. :-)) Eeerrhhh... Let's not touch Berstein, or he will rfuse answering my bugreports if I will ever change Postfix to QMail. He is a special guy. QMail is the only software I can not read like a book... > And the second note: the whole sequence is equivalent to plain blocking > connect, only with lots of overhead. In all the OSes standard connect > timeout is of order 2-4 minutes. Yes, Linux-2.2 is unfortunate exception > (13 minutes), but the difference is purely quantitative yet and for any > installation this should be changed to smaller value via sysctl in any > case. The problem here is that I need to tune timeout for: each connection, and for connect, and read/write separately. If you could give me an advise how to do this more effective, I would be really glad. Actually the problem was anyway in my app. I have fixed it. -- Sincerely Yours, Denis Perchine ---------------------------------- E-Mail: dyp@perchine.com HomePage: http://www.perchine.com/dyp/ FidoNet: 2:5000/120.5 ----------------------------------