From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S262843AbUCJVVU (ORCPT ); Wed, 10 Mar 2004 16:21:20 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S262705AbUCJVVT (ORCPT ); Wed, 10 Mar 2004 16:21:19 -0500 Received: from mail41-s.fg.online.no ([148.122.161.41]:37117 "EHLO mail41-s.fg.online.no") by vger.kernel.org with ESMTP id S262843AbUCJVVE convert rfc822-to-8bit (ORCPT ); Wed, 10 Mar 2004 16:21:04 -0500 To: KyoungSoo Park Cc: linux-kernel@vger.kernel.org Subject: Re: how to detect udp packets drops ? References: <404E36F1.8000908@newsguy.com> <404F6F52.2000202@cs.princeton.edu> <404F855E.9090009@cs.princeton.edu> From: mru@kth.se (=?iso-8859-1?q?M=E5ns_Rullg=E5rd?=) Date: Wed, 10 Mar 2004 22:20:53 +0100 In-Reply-To: <404F855E.9090009@cs.princeton.edu> (KyoungSoo Park's message of "Wed, 10 Mar 2004 16:15:10 -0500") Message-ID: User-Agent: Gnus/5.1006 (Gnus v5.10.6) XEmacs/21.4 (Security Through Obscurity, linux) MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org KyoungSoo Park writes: > Thank you for your kind response. But, if I follow your test > senario, I cannot know which entity drops the packets. Routers on > the path also can get congested and may drop the packets. That is true. > What I really want is to know is if the "kernel"(whch is supposed to > receive packets) drops packets. Do you mean you want to know if the kernel's receive buffer overflows? That could be possible in theory, but I don't know whether it's possible with the current Linux kernels. > Also I don't want to contribute to the congestion by sending test UDP > packets, because that may worsen the situation. > Isn't there any way to monitor the packet drops at the end host by > just looking at the "packet drop counter"? If the packet reaches the end host the only reason for dropping it would be a filled receive buffer. The size of the buffer can be set using setsockopt(). -- Måns Rullgård mru@kth.se