1/*	$OpenBSD: bpf.c,v 1.27 2019/06/28 13:32:50 deraadt Exp $	*/
2/*	$NetBSD: bpf.c,v 1.5.2.1 1995/11/14 08:45:42 thorpej Exp $	*/
3
4/*
5 * Copyright (c) 1988, 1992 The University of Utah and the Center
6 *	for Software Science (CSS).
7 * Copyright (c) 1992, 1993
8 *	The Regents of the University of California.  All rights reserved.
9 *
10 * This code is derived from software contributed to Berkeley by
11 * the Center for Software Science of the University of Utah Computer
12 * Science Department.  CSS requests users of this software to return
13 * to css-dist@cs.utah.edu any improvements that they make and grant
14 * CSS redistribution rights.
15 *
16 * Redistribution and use in source and binary forms, with or without
17 * modification, are permitted provided that the following conditions
18 * are met:
19 * 1. Redistributions of source code must retain the above copyright
20 *    notice, this list of conditions and the following disclaimer.
21 * 2. Redistributions in binary form must reproduce the above copyright
22 *    notice, this list of conditions and the following disclaimer in the
23 *    documentation and/or other materials provided with the distribution.
24 * 3. Neither the name of the University nor the names of its contributors
25 *    may be used to endorse or promote products derived from this software
26 *    without specific prior written permission.
27 *
28 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
29 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
30 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
31 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
32 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
33 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
34 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
35 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
36 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
37 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
38 * SUCH DAMAGE.
39 *
40 *	from: @(#)bpf.c	8.1 (Berkeley) 6/4/93
41 *
42 * From: Utah Hdr: bpf.c 3.1 92/07/06
43 * Author: Jeff Forys, University of Utah CSS
44 */
45
46#include <sys/ioctl.h>
47#include <sys/socket.h>
48
49#include <net/if.h>
50#include <net/bpf.h>
51
52#include <ctype.h>
53#include <errno.h>
54#include <fcntl.h>
55#include <stddef.h>
56#include <stdio.h>
57#include <stdlib.h>
58#include <string.h>
59#include <syslog.h>
60#include <unistd.h>
61#include <limits.h>
62#include <ifaddrs.h>
63#include "defs.h"
64
65static int BpfFd = -1;
66static unsigned int BpfLen = 0;
67static u_int8_t *BpfPkt = NULL;
68
69/*
70**  BpfOpen -- Open and initialize a BPF device.
71**
72**	Parameters:
73**		None.
74**
75**	Returns:
76**		File descriptor of opened BPF device
77**
78**	Side Effects:
79**		If an error is encountered, the program terminates here.
80*/
81int
82BpfOpen(void)
83{
84	struct ifreq ifr;
85	int n;
86
87	if ((BpfFd = open("/dev/bpf", O_RDWR)) == -1) {
88		syslog(LOG_ERR, "bpf: can't open device: %m");
89		DoExit();
90	}
91
92	/*
93	 *  Set interface name for bpf device, get data link layer
94	 *  type and make sure it's type Ethernet.
95	 */
96	(void) strncpy(ifr.ifr_name, IntfName, sizeof(ifr.ifr_name));
97	if (ioctl(BpfFd, BIOCSETIF, (caddr_t)&ifr) == -1) {
98		syslog(LOG_ERR, "bpf: ioctl(BIOCSETIF,%s): %m", IntfName);
99		DoExit();
100	}
101
102	/*
103	 *  Make sure we are dealing with an Ethernet device.
104	 */
105	if (ioctl(BpfFd, BIOCGDLT, (caddr_t)&n) == -1) {
106		syslog(LOG_ERR, "bpf: ioctl(BIOCGDLT): %m");
107		DoExit();
108	}
109	if (n != DLT_EN10MB) {
110		syslog(LOG_ERR,"bpf: %s: data-link type %d unsupported",
111		    IntfName, n);
112		DoExit();
113	}
114
115	/*
116	 *  On read(), return packets immediately (do not buffer them).
117	 */
118	n = 1;
119	if (ioctl(BpfFd, BIOCIMMEDIATE, (caddr_t)&n) == -1) {
120		syslog(LOG_ERR, "bpf: ioctl(BIOCIMMEDIATE): %m");
121		DoExit();
122	}
123
124	/*
125	 *  Try to enable the chip/driver's multicast address filter to
126	 *  grab our RMP address.  If this fails, try promiscuous mode.
127	 *  If this fails, there's no way we are going to get any RMP
128	 *  packets so just exit here.
129	 */
130#ifdef MSG_EOR
131	ifr.ifr_addr.sa_len = RMP_ADDRLEN + 2;
132#endif
133	ifr.ifr_addr.sa_family = AF_UNSPEC;
134	bcopy(&RmpMcastAddr[0], (char *)&ifr.ifr_addr.sa_data[0], RMP_ADDRLEN);
135	if (ioctl(BpfFd, SIOCADDMULTI, (caddr_t)&ifr) == -1) {
136		syslog(LOG_WARNING,
137		    "bpf: can't add mcast addr (%m), setting promiscuous mode");
138
139		if (ioctl(BpfFd, BIOCPROMISC, (caddr_t)0) == -1) {
140			syslog(LOG_ERR, "bpf: can't set promiscuous mode: %m");
141			DoExit();
142		}
143	}
144
145	/*
146	 *  Ask BPF how much buffer space it requires and allocate one.
147	 */
148	if (ioctl(BpfFd, BIOCGBLEN, (caddr_t)&BpfLen) == -1) {
149		syslog(LOG_ERR, "bpf: ioctl(BIOCGBLEN): %m");
150		DoExit();
151	}
152	if (BpfPkt == NULL)
153		BpfPkt = malloc(BpfLen);
154
155	if (BpfPkt == NULL) {
156		syslog(LOG_ERR, "bpf: out of memory (%u bytes for bpfpkt)",
157		    BpfLen);
158		DoExit();
159	}
160
161	/*
162	 *  Write a little program to snarf RMP Boot packets and stuff
163	 *  it down BPF's throat (i.e. set up the packet filter).
164	 */
165	{
166#define	RMP(field)	offsetof(struct rmp_packet, field)
167		static struct bpf_insn bpf_insn[] = {
168		    /* make sure it is a 802.3 packet */
169		    { BPF_LD|BPF_H|BPF_ABS,  0, 0, RMP(hp_hdr.len) },
170		    { BPF_JMP|BPF_JGE|BPF_K, 7, 0, 0x600 },
171
172		    { BPF_LD|BPF_B|BPF_ABS,  0, 0, RMP(hp_llc.dsap) },
173		    { BPF_JMP|BPF_JEQ|BPF_K, 0, 5, IEEE_DSAP_HP },
174		    { BPF_LD|BPF_H|BPF_ABS,  0, 0, RMP(hp_llc.cntrl) },
175		    { BPF_JMP|BPF_JEQ|BPF_K, 0, 3, IEEE_CNTL_HP },
176		    { BPF_LD|BPF_H|BPF_ABS,  0, 0, RMP(hp_llc.dxsap) },
177		    { BPF_JMP|BPF_JEQ|BPF_K, 0, 1, HPEXT_DXSAP },
178		    { BPF_RET|BPF_K,         0, 0, RMP_MAX_PACKET },
179		    { BPF_RET|BPF_K,         0, 0, 0x0 }
180		};
181
182		static struct bpf_insn bpf_wf_insn[] = {
183		    /* make sure it is a 802.3 packet */
184		    { BPF_LD|BPF_H|BPF_ABS,  0, 0, RMP(hp_hdr.len) },
185		    { BPF_JMP|BPF_JGE|BPF_K, 12, 0, 0x600 },
186
187		    /* check the SNAP header */
188		    { BPF_LD|BPF_B|BPF_ABS,  0, 0, RMP(hp_llc.dsap) },
189		    { BPF_JMP|BPF_JEQ|BPF_K, 0, 10, IEEE_DSAP_HP },
190		    { BPF_LD|BPF_H|BPF_ABS,  0, 0, RMP(hp_llc.cntrl) },
191		    { BPF_JMP|BPF_JEQ|BPF_K, 0, 8, IEEE_CNTL_HP },
192
193		    { BPF_LD|BPF_H|BPF_ABS,  0, 0, RMP(hp_llc.sxsap) },
194		    { BPF_JMP|BPF_JEQ|BPF_K, 0, 6, HPEXT_DXSAP },
195		    { BPF_LD|BPF_H|BPF_ABS,  0, 0, RMP(hp_llc.dxsap) },
196		    { BPF_JMP|BPF_JEQ|BPF_K, 0, 4, HPEXT_SXSAP },
197
198		    /* check return type code */
199		    { BPF_LD|BPF_B|BPF_ABS,  0, 0,
200		        RMP(rmp_proto.rmp_raw.rmp_type) },
201		    { BPF_JMP|BPF_JEQ|BPF_K, 1, 0, RMP_BOOT_REPL },
202		    { BPF_JMP|BPF_JEQ|BPF_K, 0, 1, RMP_READ_REPL },
203
204		    { BPF_RET|BPF_K,         0, 0, RMP_MAX_PACKET },
205		    { BPF_RET|BPF_K,         0, 0, 0x0 }
206		};
207#undef	RMP
208		static struct bpf_program bpf_pgm = {
209			sizeof(bpf_insn)/sizeof(bpf_insn[0]), bpf_insn
210		};
211
212		static struct bpf_program bpf_w_pgm = {
213			sizeof(bpf_wf_insn)/sizeof(bpf_wf_insn[0]), bpf_wf_insn
214		};
215
216		if (ioctl(BpfFd, BIOCSETF, (caddr_t)&bpf_pgm) == -1) {
217			syslog(LOG_ERR, "bpf: ioctl(BIOCSETF): %m");
218			DoExit();
219		}
220
221		if (ioctl(BpfFd, BIOCSETWF, (caddr_t)&bpf_w_pgm) == -1) {
222			syslog(LOG_ERR, "bpf: ioctl(BIOCSETWF): %m");
223			DoExit();
224		}
225
226		if (ioctl(BpfFd, BIOCLOCK) == -1) {
227			syslog(LOG_ERR, "bpf: ioctl(BIOCLOCK): %m");
228			DoExit();
229		}
230	}
231
232	return(BpfFd);
233}
234
235/*
236**  BPF GetIntfName -- Return the name of a network interface attached to
237**		the system, or 0 if none can be found.  The interface
238**		must be configured up; the lowest unit number is
239**		preferred; loopback is ignored.
240**
241**	Parameters:
242**		errmsg - if no network interface found, *errmsg explains why.
243**
244**	Returns:
245**		A (static) pointer to interface name, or NULL on error.
246**
247**	Side Effects:
248**		None.
249*/
250char *
251BpfGetIntfName(char **errmsg)
252{
253	int minunit = 999, n;
254	char *cp;
255	const char *errstr;
256	static char device[IFNAMSIZ];
257	static char errbuf[128] = "No Error!";
258	struct ifaddrs *ifap, *ifa, *mp = NULL;
259
260	if (errmsg != NULL)
261		*errmsg = errbuf;
262
263	if (getifaddrs(&ifap) != 0) {
264		(void) strlcpy(errbuf, "bpf: getifaddrs: %m", sizeof(errbuf));
265		return(NULL);
266	}
267
268	for (ifa = ifap; ifa; ifa = ifa->ifa_next) {
269		/*
270		 *  If interface is down or this is the loopback interface,
271		 *  ignore it.
272		 */
273		if ((ifa->ifa_flags & IFF_UP) == 0 ||
274#ifdef IFF_LOOPBACK
275		    (ifa->ifa_flags & IFF_LOOPBACK))
276#else
277		    (strcmp(ifa->ifa_name, "lo0") == 0))
278#endif
279			continue;
280
281		for (cp = ifa->ifa_name; !isdigit((unsigned char)*cp); ++cp)
282			;
283		n = strtonum(cp, 0, INT_MAX, &errstr);
284		if (errstr == NULL && n < minunit) {
285			minunit = n;
286			mp = ifa;
287		}
288	}
289
290	if (mp == 0) {
291		(void) strlcpy(errbuf, "bpf: no interfaces found",
292		    sizeof(errbuf));
293		freeifaddrs(ifap);
294		return(NULL);
295	}
296
297	(void) strlcpy(device, mp->ifa_name, sizeof device);
298	freeifaddrs(ifap);
299	return(device);
300}
301
302/*
303**  BpfRead -- Read packets from a BPF device and fill in `rconn'.
304**
305**	Parameters:
306**		rconn - filled in with next packet.
307**		doread - is True if we can issue a read() syscall.
308**
309**	Returns:
310**		True if `rconn' contains a new packet, False otherwise.
311**
312**	Side Effects:
313**		None.
314*/
315int
316BpfRead(RMPCONN *rconn, int doread)
317{
318	int datlen, caplen, hdrlen;
319	static u_int8_t *bp = NULL, *ep = NULL;
320	int cc;
321
322	/*
323	 *  The read() may block, or it may return one or more packets.
324	 *  We let the caller decide whether or not we can issue a read().
325	 */
326	if (doread) {
327		if ((cc = read(BpfFd, (char *)BpfPkt, (int)BpfLen)) == -1) {
328			syslog(LOG_ERR, "bpf: read: %m");
329			return(0);
330		} else {
331			bp = BpfPkt;
332			ep = BpfPkt + cc;
333		}
334	}
335
336#define bhp ((struct bpf_hdr *)bp)
337	/*
338	 *  If there is a new packet in the buffer, stuff it into `rconn'
339	 *  and return a success indication.
340	 */
341	if (bp < ep) {
342		datlen = bhp->bh_datalen;
343		caplen = bhp->bh_caplen;
344		hdrlen = bhp->bh_hdrlen;
345
346		if (caplen != datlen)
347			syslog(LOG_ERR,
348			    "bpf: short packet dropped (%d of %d bytes)",
349			    caplen, datlen);
350		else if (caplen > sizeof(struct rmp_packet))
351			syslog(LOG_ERR, "bpf: large packet dropped (%d bytes)",
352			    caplen);
353		else {
354			rconn->rmplen = caplen;
355			rconn->tstamp.tv_sec = bhp->bh_tstamp.tv_sec;
356			rconn->tstamp.tv_usec = bhp->bh_tstamp.tv_usec;
357			bcopy((char *)bp + hdrlen, (char *)&rconn->rmp, caplen);
358		}
359		bp += BPF_WORDALIGN(caplen + hdrlen);
360		return(1);
361	}
362#undef bhp
363
364	return(0);
365}
366
367/*
368**  BpfWrite -- Write packet to BPF device.
369**
370**	Parameters:
371**		rconn - packet to send.
372**
373**	Returns:
374**		True if write succeeded, False otherwise.
375**
376**	Side Effects:
377**		None.
378*/
379int
380BpfWrite(RMPCONN *rconn)
381{
382	if (write(BpfFd, (char *)&rconn->rmp, rconn->rmplen) == -1) {
383		syslog(LOG_ERR, "write: %s: %m", EnetStr(rconn));
384		return(0);
385	}
386
387	return(1);
388}
389