From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 25072 invoked by alias); 16 Jun 2009 14:23:43 -0000 Received: (qmail 25061 invoked by uid 22791); 16 Jun 2009 14:23:41 -0000 X-SWARE-Spam-Status: No, hits=-1.2 required=5.0 tests=AWL,BAYES_00,RCVD_IN_DNSWL_LOW,RCVD_NUMERIC_HELO,SPF_HELO_PASS,SPF_PASS X-Spam-Check-By: sourceware.org Received: from main.gmane.org (HELO ciao.gmane.org) (80.91.229.2) by sourceware.org (qpsmtpd/0.43rc1) with ESMTP; Tue, 16 Jun 2009 14:23:34 +0000 Received: from list by ciao.gmane.org with local (Exim 4.43) id 1MGZZR-0003wN-4Z for ecos-discuss@sources.redhat.com; Tue, 16 Jun 2009 14:23:29 +0000 Received: from 69.34.67.62 ([69.34.67.62]) by main.gmane.org with esmtp (Gmexim 0.1 (Debian)) id 1AlnuQ-0007hv-00 for ; Tue, 16 Jun 2009 14:23:29 +0000 Received: from grante by 69.34.67.62 with local (Gmexim 0.1 (Debian)) id 1AlnuQ-0007hv-00 for ; Tue, 16 Jun 2009 14:23:29 +0000 To: ecos-discuss@sources.redhat.com From: Grant Edwards Date: Tue, 16 Jun 2009 14:23:00 -0000 Message-ID: References: <20090616064348.GA32303@lunn.ch> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit User-Agent: slrn/pre0.9.9-102 (Linux) X-IsSubscribed: yes Mailing-List: contact ecos-discuss-help@ecos.sourceware.org; run by ezmlm Precedence: bulk List-Id: List-Subscribe: List-Archive: List-Post: List-Help: , Sender: ecos-discuss-owner@ecos.sourceware.org Subject: [ECOS] Re: How to send UDP broadcast to 255.255.255.255? X-SW-Source: 2009-06/txt/msg00074.txt.bz2 On 2009-06-16, Andrew Lunn wrote: > On Mon, Jun 15, 2009 at 05:41:54PM +0000, Grant Edwards wrote: >> I've been asked by one of my internal customers how to send a >> UDP broadcast packet to IP address 255.255.255.255. > > Hi Grant > > If you have a debugger handy, try putting a break point here: I don't have one handy, but it certainly looks like the right spot. > src/sys/netinet/in_pcb.c > int > in_pcbladdr(inp, nam, plocal_sin) > register struct inpcb *inp; > struct sockaddr *nam; > struct sockaddr_in **plocal_sin; > { > struct in_ifaddr *ia; > register struct sockaddr_in *sin = (struct sockaddr_in *)nam; > > if (nam->sa_len != sizeof (*sin)) > return (EINVAL); > if (sin->sin_family != AF_INET) > return (EAFNOSUPPORT); > if (sin->sin_port == 0) > return (EADDRNOTAVAIL); > if (!TAILQ_EMPTY(&in_ifaddrhead)) { > /* > * If the destination address is INADDR_ANY, > * use the primary local address. > * If the supplied address is INADDR_BROADCAST, > * and the primary interface supports broadcast, > * choose the broadcast address for that interface. > */ > #define satosin(sa) ((struct sockaddr_in *)(sa)) > #define sintosa(sin) ((struct sockaddr *)(sin)) > #define ifatoia(ifa) ((struct in_ifaddr *)(ifa)) > if (sin->sin_addr.s_addr == INADDR_ANY) > sin->sin_addr = IA_SIN(TAILQ_FIRST(&in_ifaddrhead))->sin_addr; > else if (sin->sin_addr.s_addr == (u_long)INADDR_BROADCAST && > (TAILQ_FIRST(&in_ifaddrhead)->ia_ifp->if_flags & IFF_BROADCAST)) > sin->sin_addr = satosin(&TAILQ_FIRST(&in_ifaddrhead)->ia_broadaddr)->sin_addr; > > Unfortunately, if this is the place the address is being changed, i > don't see an obvious way around this. I've been doing some experiments on a FreeBSD 6.1 system, and it won't allow applications to send a 255.255.255.255 broadcast either. In fact, it _requires_ you to specify the interface's broadcast address as a destination before in order to broadcast a packet. FreeBSD 6.1 won't "convert" 255.255.255.255 into the interface broadcast address the way that eCos does. Still, the Linux implementation seems to be a lot more useful. You can specify either 255.255.255.255 or the interface's broadcast address as the destination, and the packet is broadcast to that destination address. I found complaints dating back many years regarding FreeBSD's lack of ability to send broadcast UDP packets to 255.255.255.255. It seems you have to use the raw socket interface to do that. -- Grant Edwards grante Yow! Pardon me, but do you at know what it means to be visi.com TRULY ONE with your BOOTH! -- Before posting, please read the FAQ: http://ecos.sourceware.org/fom/ecos and search the list archive: http://ecos.sourceware.org/ml/ecos-discuss