From owner-freebsd-hackers  Tue Jul 23 17:25:14 1996
Return-Path: owner-hackers
Received: (from root@localhost)
          by freefall.freebsd.org (8.7.5/8.7.3) id RAA26907
          for hackers-outgoing; Tue, 23 Jul 1996 17:25:14 -0700 (PDT)
Received: from mail0.iij.ad.jp (root@mail0.iij.ad.jp [192.244.176.61])
          by freefall.freebsd.org (8.7.5/8.7.3) with SMTP id RAA26901
          for <hackers@FreeBSD.org>; Tue, 23 Jul 1996 17:25:11 -0700 (PDT)
Received: from uucp1.iij.ad.jp (uucp1.iij.ad.jp [192.244.176.73]) by mail0.iij.ad.jp (8.6.12+2.4W/3.3W9-MAIL) with ESMTP id JAA24172; Wed, 24 Jul 1996 09:24:26 +0900
Received: (from uucp@localhost) by uucp1.iij.ad.jp (8.6.12+2.4W/3.3W9-UUCP) with UUCP id JAA06060; Wed, 24 Jul 1996 09:24:26 +0900
Received: from xxx.fct.kgc.co.jp by yyy.kgc.co.jp (8.7.5/3.4W:95122611) id JAA11392; Wed, 24 Jul 1996 09:12:07 +0900 (JST)
Received: from localhost by xxx.fct.kgc.co.jp (8.6.12/3.3W8:95062916) id JAA00403; Wed, 24 Jul 1996 09:12:07 +0900
Message-Id: <199607240012.JAA00403@xxx.fct.kgc.co.jp>
To: "K.V.S. Sankaram" <kasturi@teil.soft.net>
cc: hackers@FreeBSD.org
Subject: Re: How to use BPF ?
In-reply-to: "K.V.S. Sankaram"'s message of 23 Jul 1996 19:29:01 +0900
References: <Pine.SGI.3.93.960723142034.11451D-100000@teil.soft.net>
Date: Wed, 24 Jul 1996 09:12:06 +0900
From: Toshihiro Kanda <candy@fct.kgc.co.jp>
Sender: owner-hackers@FreeBSD.org
X-Loop: FreeBSD.org
Precedence: bulk

> 	I am facing problems in sending packets through BPF. Can anybody give me
> 
> some idea (or steps) as to how to configure BPF and send packets through it ?

static struct bpf_program prog;

	First, initialize prog. Then,	

	char *name = "ed0";
	fd = open("/dev/bpf0", O_RDWR);
	if (fd >= 0) {
		struct bpf_version ver;
		if (ioctl(fd, BIOCVERSION, &ver) == 0) {
			if (BPF_MAJOR_VERSION == ver.bv_major && BPF_MINOR_VERSION <= ver.bv_minor) {
				unsigned int blen = BPF_BUFFER_SIZE;
				if (ioctl(fd, BIOCSBLEN, &blen) == 0) {
					struct ifreq ifr;
					strncpy(ifr.ifr_name, name, sizeof(ifr.ifr_name));
					if (ioctl(fd, BIOCSETIF, &ifr) == 0) {
						unsigned int im = 1;
						if (ioctl(fd, BIOCIMMEDIATE, &im) == 0) {
							if (ioctl(fd, BIOCSETF, prog) == 0) {
								err = fd;
							}
						}
					}
				}
			}
		}
		if (err < 0)
			close(fd);
	}
	: : :
	write(fd, data, length);

Note: data[12] and data[13] (ether type) must be host byte order (NOT
network byte order).  I believe this is a bug, though FreeBSD core
team don't think so.

candy@fct.kgc.co.jp (Toshihiro Kanda)