Date: Fri, 13 Apr 2001 10:00:21 +0200 From: Joachim =?iso-8859-1?Q?Str=F6mbergson?= <watchman@ludd.luth.se> To: Nik Clayton <nik@FreeBSD.ORG> Cc: doc@FreeBSD.ORG Subject: Suggested adendum to FAQ section 3.22 Message-ID: <3AD6B215.189906@ludd.luth.se> References: <20010404182156.C86363@canyon.nothing-going-on.org>
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Aloha! Thanks to Niks "Weekly FAQ changes mail" I saw the added question in the FAQ about slow ssh and telnet connection. I had this problem and I found this section did not contain the solution to my version of the problems, So, I would like to suggest an addition to that section. Section 3.22 reads: <quote> 3.22. Why does it take so long to connect to my computer via ssh(1) or telnet(1)? The symptom: there is a long delay between the time the TCP connection is established and the time when the client software asks for a password (or, in telnet(1)'s case, when a login prompt appears). The problem: more likely than not, the delay is caused by the server software trying to resolve the client's IP address into a hostname. Many servers, including the Telnet and SSH servers that come with FreeBSD, do this in order to, among other things, store the hostname in a log file for future reference by the administrator. The remedy: if the problem occurs whenever you connect from your computer (the client) to any server, the problem is with the client; likewise, if the problem only occurs when someone connects to your computer (the server) the problem is with the server. If the problem is with the client, the only remedy is to fix the DNS so the server can resolve it. If this is on a local network, consider it a server problem and keep reading; conversely, if this is on the global Internet, you will most likely need to contact your ISP and ask them to fix it for you. </quote> Problem discussion: ------------------- First off - a question: Wouldn't the same problem affect ftp, http and ping to the same host - that is a name resolution problem should affect all connection types, not only telnet or ssh, no? For me I had the behaviour described in 3.22. The problem was that the sites I tried to connect to belonged to some of the bigger sites on the net, and the DNSs I use are also among the bigger ones (my ISP is the biggest ISP in the country). It was also pretty easy to do a name lookup and find the correct name and IP-number for the hosts I tried to SSH or Telnet to. Furthermore, ftp worked nicely, whereas telnet to port 21 didn't. Running ktrace while running ssh and telnet suggested common libraries. The solution found was to do a buildworld/installworld so that libraries and binaries were updated. Now, ssh and telnet runs fine. Analysis of my faulty ways: --------------------------- (1) I had used -O3 optimization for the last version of system upgrade. Yes, this is BAD. No, it won't happen again. This could very well be the reason for the behaviour. (2) I update the cvs-tree and make buildworld on a weekly basis, but update the system very much more rarely. The kernel however have been updated due to added HW and such things. Since the kernel sources have been updated, some problems due to kernel and system is out of sync might be responsible. Suggested addendum: ------------------- If the DNS entries seemes to be in order make sure that your system have been updated and/or the kernel is in sync with the system. If not, see the handbook section <xxx.yy> for ways to update the system. For information about compiler optimization settings, see <mmm,nnn>. If your system is in sync and up to date, please ensure that the system have been built without compiler optimizations that can generate faulty code. Check in /etc/make.conf and ensure that the optimization flag is set to at most -O2, or that the CFLAGS and COPTFLAGS have been commented out. Comments, suggestions are highly welcome. Yes, I know I messed up on the optimization bit, I know that's a no-no. I'm pretty sure thhough I'm not the first nor last person that will make that mistake - and possibly learn from it by reading section 3.22. -- Cheers! Joachim - Alltid i harmonisk svängning --- FairLight ------ FairLight ------ FairLight ------ FairLight --- Joachim Strömbergson ASIC SoC designer, nice to CUTE animals Phone: +46(0)31 - 27 98 47 Web: http://www.ludd.luth.se/~watchman --------------- Spamfodder: regeringen@regeringen.se --------------- To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-doc" in the body of the message
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