From owner-freebsd-net Mon Sep 2 17:50: 7 2002 Delivered-To: freebsd-net@freebsd.org Received: from mx1.FreeBSD.org (mx1.FreeBSD.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id 7F80337B400 for ; Mon, 2 Sep 2002 17:49:59 -0700 (PDT) Received: from smtp2.vol.cz (smtp2.vol.cz [195.250.128.42]) by mx1.FreeBSD.org (Postfix) with ESMTP id 8F4CE43E4A for ; Mon, 2 Sep 2002 17:49:58 -0700 (PDT) (envelope-from dan@obluda.cz) Received: from obluda.cz (xkulesh.vol.cz [195.250.154.106]) by smtp2.vol.cz (8.12.5/8.12.5) with ESMTP id g830nvtV024751 for ; Tue, 3 Sep 2002 02:49:57 +0200 (CEST) (envelope-from dan@obluda.cz) Message-ID: <3D6EE15E.1060508@obluda.cz> Date: Fri, 30 Aug 2002 05:07:10 +0200 From: Dan Lukes User-Agent: Mozilla/5.0 (X11; U; FreeBSD i386; en-US; rv:1.0rc3) Gecko/20020524 X-Accept-Language: en, cs MIME-Version: 1.0 To: freebsd-net@freebsd.org Subject: Limited broadcast procesing (still unanswered question) Content-Type: text/plain; charset=iso-8859-2; format=flowed Content-Transfer-Encoding: 7bit Sender: owner-freebsd-net@FreeBSD.ORG Precedence: bulk List-ID: List-Archive: (Web Archive) List-Help: (List Instructions) List-Subscribe: List-Unsubscribe: X-Loop: FreeBSD.org Hi, as I got no response to my question sent to -hackers several months ago, I want to repeat it there. (first incarnation of the question has been sent to -question on November 21, 2001, no response) -net seems to be more apropriate forum ... Dan -------- Original Message -------- Subject: Limited broadcast procesing. Date: Sun, 11 Feb 2002 23:36:24 +0100 From: Dan Lukes Hi. I don't understand some aspects of processing of packets with destination address 255.255.255.255 a) if first interface is broadcast capable then the destination address is unconditionally rewritten with no warning to first subnet network broadcast address on that interface and send; else the destination address is left intact and continue to b) b) if SO_DONTROUTE not set then routing table apply (most important rule is "default"); else packet discarded (no route to ...) My first question: Why the silent rewritting of one destination address to other is used ? There must be a good reason to change explicit user request and rewrite it to another one, but I have no idea about it. I tracked history of it code in in_pcb.c - I found it in 4.3BSD (dated 6/29/88) - so it's an ancient relict ? Second question(s): How to send a packet to limited broadcast address over specific interface (using standard socket interface, not bpf)? If there no way to do it, should be ? If there is no way to do it and should be, I have a idea how to do it. If source address is set to a interface address and SO_DONTROUTE is in effect, then packet adressed to limited broadcast is sent over the interface specified by the source address (current processing discard it with "no route to ..." unless silent rewritting of destination address do it's dirty work). The silent rewriting of destination address must not occur for those packets. It is acceptable ? I see no contraindication. I read the sys/netinet/ from first line to last line several times, but it's possible i'm missed something, of course. Dan Please note the english isn't my native language, but I hope it's readable. -- Dan Lukes tel: +420 2 21914205, fax: +420 2 21914206 root of FIONet, KolejNET, webmaster of www.freebsd.cz AKA: dan@obluda.cz, dan@freebsd.cz,dan@kolej.mff.cuni.cz To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-net" in the body of the message