xref: /freebsd/contrib/bsnmp/snmpd/trans_udp.c (revision be996c05224c3d82f26f94315c760776c3f2896c) 
1 /*
2  * Copyright (c) 2003
3  *	Fraunhofer Institute for Open Communication Systems (FhG Fokus).
4  *	All rights reserved.
5  *
6  * Author: Harti Brandt <harti@freebsd.org>
7  *
8  * Redistribution and use in source and binary forms, with or without
9  * modification, are permitted provided that the following conditions
10  * are met:
11  * 1. Redistributions of source code must retain the above copyright
12  *    notice, this list of conditions and the following disclaimer.
13  * 2. Redistributions in binary form must reproduce the above copyright
14  *    notice, this list of conditions and the following disclaimer in the
15  *    documentation and/or other materials provided with the distribution.
16  *
17  * THIS SOFTWARE IS PROVIDED BY AUTHOR AND CONTRIBUTORS ``AS IS'' AND
18  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
19  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
20  * ARE DISCLAIMED.  IN NO EVENT SHALL AUTHOR OR CONTRIBUTORS BE LIABLE
21  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
22  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
23  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
24  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
25  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
26  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
27  * SUCH DAMAGE.
28  *
29  * $Begemot: bsnmp/snmpd/trans_udp.c,v 1.5 2005/10/04 08:46:56 brandt_h Exp $
30  *
31  * UDP transport
32  */
33 #include <sys/types.h>
34 #include <sys/queue.h>
35 #include <sys/ucred.h>
36 
37 #include <stdlib.h>
38 #include <syslog.h>
39 #include <string.h>
40 #include <errno.h>
41 #include <unistd.h>
42 
43 #include <netinet/in.h>
44 #include <arpa/inet.h>
45 
46 #include "snmpmod.h"
47 #include "snmpd.h"
48 #include "trans_udp.h"
49 #include "tree.h"
50 #include "oid.h"
51 
52 static int udp_start(void);
53 static int udp_stop(int);
54 static void udp_close_port(struct tport *);
55 static int udp_init_port(struct tport *);
56 static ssize_t udp_send(struct tport *, const u_char *, size_t,
57     const struct sockaddr *, size_t);
58 static ssize_t udp_recv(struct tport *, struct port_input *);
59 
60 /* exported */
61 const struct transport_def udp_trans = {
62 	"udp",
63 	OIDX_begemotSnmpdTransUdp,
64 	udp_start,
65 	udp_stop,
66 	udp_close_port,
67 	udp_init_port,
68 	udp_send,
69 	udp_recv
70 };
71 static struct transport *my_trans;
72 
73 static int
74 udp_start(void)
75 {
76 	return (trans_register(&udp_trans, &my_trans));
77 }
78 
79 static int
80 udp_stop(int force __unused)
81 {
82 	if (my_trans != NULL)
83 		if (trans_unregister(my_trans) != 0)
84 			return (SNMP_ERR_GENERR);
85 	return (SNMP_ERR_NOERROR);
86 }
87 
88 /*
89  * A UDP port is ready
90  */
91 static void
92 udp_input(int fd __unused, void *udata)
93 {
94 	struct udp_port *p = udata;
95 
96 	p->input.peerlen = sizeof(p->ret);
97 	snmpd_input(&p->input, &p->tport);
98 }
99 
100 /*
101  * Create a UDP socket and bind it to the given port
102  */
103 static int
104 udp_init_port(struct tport *tp)
105 {
106 	struct udp_port *p = (struct udp_port *)tp;
107 	struct sockaddr_in addr;
108 	u_int32_t ip;
109 	const int on = 1;
110 
111 	if ((p->input.fd = socket(PF_INET, SOCK_DGRAM, 0)) < 0) {
112 		syslog(LOG_ERR, "creating UDP socket: %m");
113 		return (SNMP_ERR_RES_UNAVAIL);
114 	}
115 	ip = (p->addr[0] << 24) | (p->addr[1] << 16) | (p->addr[2] << 8) |
116 	    p->addr[3];
117 	memset(&addr, 0, sizeof(addr));
118 	addr.sin_addr.s_addr = htonl(ip);
119 	addr.sin_port = htons(p->port);
120 	addr.sin_family = AF_INET;
121 	addr.sin_len = sizeof(addr);
122 	if (addr.sin_addr.s_addr == INADDR_ANY &&
123 	    setsockopt(p->input.fd, IPPROTO_IP, IP_RECVDSTADDR, &on,
124 	    sizeof(on)) == -1) {
125 		syslog(LOG_ERR, "setsockopt(IP_RECVDSTADDR): %m");
126 		close(p->input.fd);
127 		p->input.fd = -1;
128 		return (SNMP_ERR_GENERR);
129 	}
130 	if (bind(p->input.fd, (struct sockaddr *)&addr, sizeof(addr))) {
131 		if (errno == EADDRNOTAVAIL) {
132 			close(p->input.fd);
133 			p->input.fd = -1;
134 			return (SNMP_ERR_INCONS_NAME);
135 		}
136 		syslog(LOG_ERR, "bind: %s:%u %m", inet_ntoa(addr.sin_addr),
137 		    p->port);
138 		close(p->input.fd);
139 		p->input.fd = -1;
140 		return (SNMP_ERR_GENERR);
141 	}
142 	if ((p->input.id = fd_select(p->input.fd, udp_input,
143 	    p, NULL)) == NULL) {
144 		close(p->input.fd);
145 		p->input.fd = -1;
146 		return (SNMP_ERR_GENERR);
147 	}
148 	return (SNMP_ERR_NOERROR);
149 }
150 
151 /*
152  * Create a new SNMP Port object and start it, if we are not
153  * in initialization mode. The arguments are in host byte order.
154  */
155 static int
156 udp_open_port(u_int8_t *addr, u_int32_t udp_port, struct udp_port **pp)
157 {
158 	struct udp_port *port;
159 	int err;
160 
161 	if (udp_port > 0xffff)
162 		return (SNMP_ERR_NO_CREATION);
163 	if ((port = malloc(sizeof(*port))) == NULL)
164 		return (SNMP_ERR_GENERR);
165 	memset(port, 0, sizeof(*port));
166 
167 	/* initialize common part */
168 	port->tport.index.len = 5;
169 	port->tport.index.subs[0] = addr[0];
170 	port->tport.index.subs[1] = addr[1];
171 	port->tport.index.subs[2] = addr[2];
172 	port->tport.index.subs[3] = addr[3];
173 	port->tport.index.subs[4] = udp_port;
174 
175 	port->addr[0] = addr[0];
176 	port->addr[1] = addr[1];
177 	port->addr[2] = addr[2];
178 	port->addr[3] = addr[3];
179 	port->port = udp_port;
180 
181 	port->input.fd = -1;
182 	port->input.id = NULL;
183 	port->input.stream = 0;
184 	port->input.cred = 0;
185 	port->input.peer = (struct sockaddr *)&port->ret;
186 	port->input.peerlen = sizeof(port->ret);
187 
188 	trans_insert_port(my_trans, &port->tport);
189 
190 	if (community != COMM_INITIALIZE &&
191 	    (err = udp_init_port(&port->tport)) != SNMP_ERR_NOERROR) {
192 		udp_close_port(&port->tport);
193 		return (err);
194 	}
195 	*pp = port;
196 	return (SNMP_ERR_NOERROR);
197 }
198 
199 /*
200  * Close an SNMP port
201  */
202 static void
203 udp_close_port(struct tport *tp)
204 {
205 	struct udp_port *port = (struct udp_port *)tp;
206 
207 	snmpd_input_close(&port->input);
208 	trans_remove_port(tp);
209 	free(port);
210 }
211 
212 /*
213  * Send something
214  */
215 static ssize_t
216 udp_send(struct tport *tp, const u_char *buf, size_t len,
217     const struct sockaddr *addr, size_t addrlen)
218 {
219 	struct udp_port *p = (struct udp_port *)tp;
220 	struct cmsghdr *cmsg;
221 	struct in_addr *src_addr;
222 	struct msghdr msg;
223 	char cbuf[CMSG_SPACE(sizeof(struct in_addr))];
224 	struct iovec iov;
225 
226 	iov.iov_base = __DECONST(void*, buf);
227 	iov.iov_len = len;
228 
229 	msg.msg_flags = 0;
230 	msg.msg_iov = &iov;
231 	msg.msg_iovlen = 1;
232 	msg.msg_name = __DECONST(void *, addr);
233 	msg.msg_namelen = addrlen;
234 	msg.msg_control = cbuf;
235 	msg.msg_controllen = sizeof(cbuf);
236 
237 	cmsg = CMSG_FIRSTHDR(&msg);
238 	cmsg->cmsg_level = IPPROTO_IP;
239 	cmsg->cmsg_type = IP_SENDSRCADDR;
240 	cmsg->cmsg_len = CMSG_LEN(sizeof(struct in_addr));
241 	src_addr = (struct in_addr *)(void*)CMSG_DATA(cmsg);
242 	memcpy(src_addr, &p->recv_addr, sizeof(struct in_addr));
243 
244 	return (sendmsg(p->input.fd, &msg, 0));
245 }
246 
247 static void
248 check_priv_dgram(struct port_input *pi, struct sockcred *cred)
249 {
250 
251 	/* process explicitly sends credentials */
252 	if (cred)
253 		pi->priv = (cred->sc_euid == 0);
254 	else
255 		pi->priv = 0;
256 }
257 
258 /*
259  * Input from a datagram socket.
260  * Each receive should return one datagram.
261  */
262 static ssize_t
263 recv_dgram(struct port_input *pi, struct in_addr *laddr)
264 {
265 	u_char embuf[1000];
266 	char cbuf[CMSG_SPACE(SOCKCREDSIZE(CMGROUP_MAX)) +
267 	    CMSG_SPACE(sizeof(struct in_addr))];
268 	struct msghdr msg;
269 	struct iovec iov[1];
270 	ssize_t len;
271 	struct cmsghdr *cmsg;
272 	struct sockcred *cred = NULL;
273 
274 	if (pi->buf == NULL) {
275 		/* no buffer yet - allocate one */
276 		if ((pi->buf = buf_alloc(0)) == NULL) {
277 			/* ups - could not get buffer. Read away input
278 			 * and drop it */
279 			(void)recvfrom(pi->fd, embuf, sizeof(embuf),
280 			    0, NULL, NULL);
281 			/* return error */
282 			return (-1);
283 		}
284 		pi->buflen = buf_size(0);
285 	}
286 
287 	/* try to get a message */
288 	msg.msg_name = pi->peer;
289 	msg.msg_namelen = pi->peerlen;
290 	msg.msg_iov = iov;
291 	msg.msg_iovlen = 1;
292 	memset(cbuf, 0, sizeof(cbuf));
293 	msg.msg_control = cbuf;
294 	msg.msg_controllen = sizeof(cbuf);
295 	msg.msg_flags = 0;
296 
297 	iov[0].iov_base = pi->buf;
298 	iov[0].iov_len = pi->buflen;
299 
300 	len = recvmsg(pi->fd, &msg, 0);
301 
302 	if (len == -1 || len == 0)
303 		/* receive error */
304 		return (-1);
305 
306 	if (msg.msg_flags & MSG_TRUNC) {
307 		/* truncated - drop */
308 		snmpd_stats.silentDrops++;
309 		snmpd_stats.inTooLong++;
310 		return (-1);
311 	}
312 
313 	pi->length = (size_t)len;
314 
315 	for (cmsg = CMSG_FIRSTHDR(&msg); cmsg != NULL;
316 	    cmsg = CMSG_NXTHDR(&msg, cmsg)) {
317 		if (cmsg->cmsg_level == IPPROTO_IP &&
318 		    cmsg->cmsg_type == IP_RECVDSTADDR)
319 			memcpy(laddr, CMSG_DATA(cmsg), sizeof(struct in_addr));
320 		if (cmsg->cmsg_level == SOL_SOCKET &&
321 		    cmsg->cmsg_type == SCM_CREDS)
322 			cred = (struct sockcred *)CMSG_DATA(cmsg);
323 	}
324 
325 	if (pi->cred)
326 		check_priv_dgram(pi, cred);
327 
328 	return (0);
329 }
330 
331 /*
332  * Receive something
333  */
334 static ssize_t
335 udp_recv(struct tport *tp, struct port_input *pi)
336 {
337 	struct udp_port *p = (struct udp_port *)tp;
338 	struct cmsghdr *cmsgp;
339 	struct in_addr *laddr;
340 	struct msghdr msg;
341 	char cbuf[CMSG_SPACE(sizeof(struct in_addr))];
342 	ssize_t ret;
343 
344 	memset(cbuf, 0, sizeof(cbuf));
345 
346 	msg.msg_control = cbuf;
347 	msg.msg_controllen = sizeof(cbuf);
348 
349 	cmsgp = CMSG_FIRSTHDR(&msg);
350 	cmsgp->cmsg_len = CMSG_LEN(sizeof(struct in_addr));
351 	cmsgp->cmsg_level = IPPROTO_IP;
352 	cmsgp->cmsg_type = IP_SENDSRCADDR;
353 	laddr = (struct in_addr *)CMSG_DATA(cmsgp);
354 
355 	ret = recv_dgram(pi, laddr);
356 
357 	memcpy(&p->recv_addr, laddr, sizeof(struct in_addr));
358 
359 	if (laddr->s_addr == INADDR_ANY) {
360 		msg.msg_control = NULL;
361 		msg.msg_controllen = 0;
362 	}
363 
364 	return (ret);
365 }
366 
367 /*
368  * Port table
369  */
370 int
371 op_snmp_port(struct snmp_context *ctx, struct snmp_value *value,
372     u_int sub, u_int iidx, enum snmp_op op)
373 {
374 	asn_subid_t which = value->var.subs[sub-1];
375 	struct udp_port *p;
376 	u_int8_t addr[4];
377 	u_int32_t port;
378 
379 	switch (op) {
380 
381 	  case SNMP_OP_GETNEXT:
382 		if ((p = (struct udp_port *)trans_next_port(my_trans,
383 		    &value->var, sub)) == NULL)
384 			return (SNMP_ERR_NOSUCHNAME);
385 		index_append(&value->var, sub, &p->tport.index);
386 		break;
387 
388 	  case SNMP_OP_GET:
389 		if ((p = (struct udp_port *)trans_find_port(my_trans,
390 		    &value->var, sub)) == NULL)
391 			return (SNMP_ERR_NOSUCHNAME);
392 		break;
393 
394 	  case SNMP_OP_SET:
395 		p = (struct udp_port *)trans_find_port(my_trans,
396 		    &value->var, sub);
397 		ctx->scratch->int1 = (p != NULL);
398 
399 		if (which != LEAF_begemotSnmpdPortStatus)
400 			abort();
401 		if (!TRUTH_OK(value->v.integer))
402 			return (SNMP_ERR_WRONG_VALUE);
403 
404 		ctx->scratch->int2 = TRUTH_GET(value->v.integer);
405 
406 		if (ctx->scratch->int2) {
407 			/* open an SNMP port */
408 			if (p != NULL)
409 				/* already open - do nothing */
410 				return (SNMP_ERR_NOERROR);
411 
412 			if (index_decode(&value->var, sub, iidx, addr, &port))
413 				return (SNMP_ERR_NO_CREATION);
414 			return (udp_open_port(addr, port, &p));
415 
416 		} else {
417 			/* close SNMP port - do in commit */
418 		}
419 		return (SNMP_ERR_NOERROR);
420 
421 	  case SNMP_OP_ROLLBACK:
422 		p = (struct udp_port *)trans_find_port(my_trans,
423 		    &value->var, sub);
424 		if (ctx->scratch->int1 == 0) {
425 			/* did not exist */
426 			if (ctx->scratch->int2 == 1) {
427 				/* created */
428 				if (p != NULL)
429 					udp_close_port(&p->tport);
430 			}
431 		}
432 		return (SNMP_ERR_NOERROR);
433 
434 	  case SNMP_OP_COMMIT:
435 		p = (struct udp_port *)trans_find_port(my_trans,
436 		    &value->var, sub);
437 		if (ctx->scratch->int1 == 1) {
438 			/* did exist */
439 			if (ctx->scratch->int2 == 0) {
440 				/* delete */
441 				if (p != NULL)
442 					udp_close_port(&p->tport);
443 			}
444 		}
445 		return (SNMP_ERR_NOERROR);
446 
447 	  default:
448 		abort();
449 	}
450 
451 	/*
452 	 * Come here to fetch the value
453 	 */
454 	switch (which) {
455 
456 	  case LEAF_begemotSnmpdPortStatus:
457 		value->v.integer = 1;
458 		break;
459 
460 	  default:
461 		abort();
462 	}
463 
464 	return (SNMP_ERR_NOERROR);
465 }
466