From owner-freebsd-questions Thu Jul 18 15:46:59 2002 Delivered-To: freebsd-questions@freebsd.org Received: from mx1.FreeBSD.org (mx1.FreeBSD.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id 7157337B400 for ; Thu, 18 Jul 2002 15:46:56 -0700 (PDT) Received: from dan.emsphone.com (dan.emsphone.com [199.67.51.101]) by mx1.FreeBSD.org (Postfix) with ESMTP id A55FA43E58 for ; Thu, 18 Jul 2002 15:46:55 -0700 (PDT) (envelope-from dan@dan.emsphone.com) Received: (from dan@localhost) by dan.emsphone.com (8.12.5/8.12.5) id g6IMkhsA002410; Thu, 18 Jul 2002 17:46:43 -0500 (CDT) (envelope-from dan) Date: Thu, 18 Jul 2002 17:46:43 -0500 From: Dan Nelson To: Benjamin Franks Cc: freebsd-questions@FreeBSD.ORG Subject: Re: tcp SYN retries? Message-ID: <20020718224643.GA74352@dan.emsphone.com> References: <20020718145818.M46100-100000@crimea.dzhan.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20020718145818.M46100-100000@crimea.dzhan.com> X-OS: FreeBSD 5.0-CURRENT X-message-flag: Outlook Error User-Agent: Mutt/1.5.1i Sender: owner-freebsd-questions@FreeBSD.ORG Precedence: bulk List-ID: List-Archive: (Web Archive) List-Help: (List Instructions) List-Subscribe: List-Unsubscribe: X-Loop: FreeBSD.ORG In the last episode (Jul 18), Benjamin Franks said: > When I attempt to make a sock_stream connection to an IP, and DON'T > receive an ACK or RST response, it seems that the system retries a finite > number of times by sending additional SYN packets. There also looks to be > a 3 or 6 second delay between SYN retries. After four or five, the > connection fails. The delays are stored in /sys/netinet/tcp_timer.c, tcp_syn_backoff[]. Those numbers are multiplied by 3 ( TCPTV_RTOBASE - the default retransmit timeout) to get the 3, 3, 3, 3, 3, 6, 12, 24 delays you are seeing. > Is there a way I can change the interval time for SYN retries, or > decrease the number of times it retries? I would imagine this would > be dependent on the particular tcp/ip stack implementation of my OS. > I'm using FreeBSD and would imaging some kernel sysctl variable would > control this... Any ideas? Or perhaps it's a socket option? You'll have to twiddle those numbers and rebuild the kernel. -- Dan Nelson dnelson@allantgroup.com To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-questions" in the body of the message