Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755636Ab2HAPrE (ORCPT ); Wed, 1 Aug 2012 11:47:04 -0400 Received: from alice.et.bocholt.fh-gelsenkirchen.de ([193.175.197.63]:46545 "EHLO alice.et.bocholt.fh-gelsenkirchen.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755226Ab2HAPrB (ORCPT ); Wed, 1 Aug 2012 11:47:01 -0400 X-DKIM: Sendmail DKIM Filter v2.8.3 alice.et.bocholt.fh-gelsenkirchen.de q71FkesX031280 From: Dirk Gouders To: Rob Landley Cc: Milton Miller , Borislav Petkov , Cong Wang , Jesse Barnes , Linux Kernel Subject: Re: [RFC] netconsole.txt: "nc" needs "-p" to specify the listening port In-Reply-To: <501937F7.2070600@landley.net> (Rob Landley's message of "Wed, 01 Aug 2012 09:06:47 -0500") References:

<501937F7.2070600@landley.net> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/23.4 (gnu/linux) Date: Wed, 01 Aug 2012 17:46:38 +0200 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii X-Greylist: Sender succeeded STARTTLS authentication, not delayed by milter-greylist-4.2.3 (alice.et.bocholt.fh-gelsenkirchen.de [192.168.0.63]); Wed, 01 Aug 2012 17:46:41 +0200 (CEST) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 5049 Lines: 139 Rob Landley writes: > On 07/29/2012 03:40 AM, Milton Miller wrote: >> [adding Rob as Doc maintanier] >> >> On Sat, 28 Jul 2012 about 11:08:16 -0000, Dirk Gouders wrote: >>> Borislav Petkov writes: >>> >>>> On Fri, Jul 27, 2012 at 11:24:53AM +0200, Dirk Gouders wrote: >>>>> Cong Wang writes: >>>>> >>>>>> On Fri, Jul 27, 2012 at 2:35 PM, Dirk Gouders >>>>>> wrote: >>>>>>> Hi Jesse, >>>>>>> >>>>>>> I would like to ask you to check if the documentation of "nc" in >>>>>>> netconsole.txt is still correct. I tried two different netcat packages >>>>>>> and both require "-p" to specify the listening port. I am wondering if >>>>>>> that changed after the use of "nc" has been documented. >>>>>> >>>>>> On Fedora 16, `nc -u -l ` works fine. >>>>> >>>>> Thanks for checking that. >>>>> >>>>> If the information I found is correct, Fedora uses OpenBSD's nc >>>>> codebase. The two netcat packages I tested on a Gentoo system differ in >>>>> requiring the -p switch for the port specification. >>>> >>>> So say exactly that in the doc: that the *BSD's version of nc doesn't >>>> need the port number specified with '-p' and you're covered. >>> OK, I tried that in the attached patch. >>> I'm not sure if every exeption needs to/should be documented, though. >>> >>> >From 3cdeac3e814471053129145c5fa8391acb365fd8 Mon Sep 17 00:00:00 2001 >>> From: Dirk Gouders >>> Date: Sat, 28 Jul 2012 12:32:49 +0200 >>> Subject: [PATCH] netconsole.txt: non-BSD versions of nc(1) require '-p' >>> switch >>> >>> Gentoo for example uses non-BSD versions of nc(1) which require >>> the '-p' switch to specify the listening port. >>> >>> --- >>> Documentation/networking/netconsole.txt | 3 ++- >>> 1 files changed, 2 insertions(+), 1 deletions(-) > > Did this ever resolve to a specific recommended patch? The one at the > start of the thread: > > http://lkml.indiana.edu/hypermail/linux/kernel/1207.3/01995.html > > Apparently isn't it...? Sorry for the delay. I tested the situation on a few distributions and am still thinking about a proper way to write it in a way without netconsole.txt becoming a kind of "netcat.txt". I would be glad about comments to what I currently have -- also, because I am not a native English speaker: ------------------------------------------------------------------------ The remote host can run syslogd or netcat to receive the kernel messages. On distributions using a BSD-based netcat version (e.g. Fedora, openSUSE and Ubuntu) the listening port must be specified without the -p switch: 'nc -u -l -p ' / 'nc -u -l ' or 'netcat -u -l -p ' / 'netcat -u -l ' ------------------------------------------------------------------------ At the end, I also attach what I have noted during the tests with the different distributions. Dirk ------------------------------------------------------------------------ Problem on systems where the gnu-netcat package provides a symbolic link /usr/bin/nc -> /usr/bin/netcat: gnu-netcat requires -p to specify the local port but does not complain if invoked as `nc -l -u '; you need to use -v to see that it does not do what you might expect: # nc -l -u 4444 -v Warning: Inverse name lookup failed for `0.0.17.92' ------------------------------------------------------------------------ Distro Package needs -p Command invocation ======================================================================== Arch gnu-netcat yes (Website nc | netcat documentation) openbsd-netcat no nc.openbsd ------------------------------------------------------------------------ Debian-6.0.5 netcat-openbsd no nc | netcat | nc.openbsd netcat / netcat-traditional (preinstalled) yes nc | netcat netcat6 yes nc | netcat | nc6 ------------------------------------------------------------------------ Fedora-17 nc (preinstalled) no nc nc6 nc6 yes ------------------------------------------------------------------------ Gentoo gnu-netcat yes netcat netcat yes nc netcat6 yes nc | nc6 ------------------------------------------------------------------------ OpenSUSE-12.1 netcat-openbsd no nc | netcat ------------------------------------------------------------------------ Ubuntu-12.04 netcat-openbsd (preinstalled) no Desktop nc | netcat | nc.openbsd netcat / netcat-traditional yes nc | netcat netcat6 yes nc | netcat | nc6 ------------------------------------------------------------------------ -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/