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
65 static int BpfFd = -1;
66 static unsigned int BpfLen = 0;
67 static 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 */
81 int
BpfOpen(void)82 BpfOpen(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 */
250 char *
BpfGetIntfName(char ** errmsg)251 BpfGetIntfName(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 */
315 int
BpfRead(RMPCONN * rconn,int doread)316 BpfRead(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 */
379 int
BpfWrite(RMPCONN * rconn)380 BpfWrite(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