Update version for v4.2.0-rc4 release
[qemu.git] / qemu-bridge-helper.c
1 /*
2 * QEMU Bridge Helper
3 *
4 * Copyright IBM, Corp. 2011
5 *
6 * Authors:
7 * Anthony Liguori <aliguori@us.ibm.com>
8 * Richa Marwaha <rmarwah@linux.vnet.ibm.com>
9 * Corey Bryant <coreyb@linux.vnet.ibm.com>
10 *
11 * This work is licensed under the terms of the GNU GPL, version 2. See
12 * the COPYING file in the top-level directory.
13 */
14
15 /*
16 * Known shortcomings:
17 * - There is no manual page
18 * - The syntax of the ACL file is not documented anywhere
19 * - parse_acl_file() doesn't report fopen() failure properly, fails
20 * to check ferror() after fgets() failure, arbitrarily truncates
21 * long lines, handles whitespace inconsistently, error messages
22 * don't point to the offending file and line, errors in included
23 * files are reported, but otherwise ignored, ...
24 */
25
26 #include "qemu/osdep.h"
27
28
29 #include <sys/ioctl.h>
30 #include <sys/socket.h>
31 #include <sys/un.h>
32 #include <sys/prctl.h>
33
34 #include <net/if.h>
35
36 #include <linux/sockios.h>
37
38 #ifndef SIOCBRADDIF
39 #include <linux/if_bridge.h>
40 #endif
41
42 #include "qemu/queue.h"
43
44 #include "net/tap-linux.h"
45
46 #ifdef CONFIG_LIBCAP
47 #include <cap-ng.h>
48 #endif
49
50 #define DEFAULT_ACL_FILE CONFIG_QEMU_CONFDIR "/bridge.conf"
51
52 enum {
53 ACL_ALLOW = 0,
54 ACL_ALLOW_ALL,
55 ACL_DENY,
56 ACL_DENY_ALL,
57 };
58
59 typedef struct ACLRule {
60 int type;
61 char iface[IFNAMSIZ];
62 QSIMPLEQ_ENTRY(ACLRule) entry;
63 } ACLRule;
64
65 typedef QSIMPLEQ_HEAD(ACLList, ACLRule) ACLList;
66
67 static void usage(void)
68 {
69 fprintf(stderr,
70 "Usage: qemu-bridge-helper [--use-vnet] --br=bridge --fd=unixfd\n");
71 }
72
73 static int parse_acl_file(const char *filename, ACLList *acl_list)
74 {
75 FILE *f;
76 char line[4096];
77 ACLRule *acl_rule;
78
79 f = fopen(filename, "r");
80 if (f == NULL) {
81 return -1;
82 }
83
84 while (fgets(line, sizeof(line), f) != NULL) {
85 char *ptr = line;
86 char *cmd, *arg, *argend;
87
88 while (g_ascii_isspace(*ptr)) {
89 ptr++;
90 }
91
92 /* skip comments and empty lines */
93 if (*ptr == '#' || *ptr == 0) {
94 continue;
95 }
96
97 cmd = ptr;
98 arg = strchr(cmd, ' ');
99 if (arg == NULL) {
100 arg = strchr(cmd, '\t');
101 }
102
103 if (arg == NULL) {
104 fprintf(stderr, "Invalid config line:\n %s\n", line);
105 goto err;
106 }
107
108 *arg = 0;
109 arg++;
110 while (g_ascii_isspace(*arg)) {
111 arg++;
112 }
113
114 argend = arg + strlen(arg);
115 while (arg != argend && g_ascii_isspace(*(argend - 1))) {
116 argend--;
117 }
118 *argend = 0;
119
120 if (!g_str_equal(cmd, "include") && strlen(arg) >= IFNAMSIZ) {
121 fprintf(stderr, "name `%s' too long: %zu\n", arg, strlen(arg));
122 goto err;
123 }
124
125 if (strcmp(cmd, "deny") == 0) {
126 acl_rule = g_malloc(sizeof(*acl_rule));
127 if (strcmp(arg, "all") == 0) {
128 acl_rule->type = ACL_DENY_ALL;
129 } else {
130 acl_rule->type = ACL_DENY;
131 snprintf(acl_rule->iface, IFNAMSIZ, "%s", arg);
132 }
133 QSIMPLEQ_INSERT_TAIL(acl_list, acl_rule, entry);
134 } else if (strcmp(cmd, "allow") == 0) {
135 acl_rule = g_malloc(sizeof(*acl_rule));
136 if (strcmp(arg, "all") == 0) {
137 acl_rule->type = ACL_ALLOW_ALL;
138 } else {
139 acl_rule->type = ACL_ALLOW;
140 snprintf(acl_rule->iface, IFNAMSIZ, "%s", arg);
141 }
142 QSIMPLEQ_INSERT_TAIL(acl_list, acl_rule, entry);
143 } else if (strcmp(cmd, "include") == 0) {
144 /* ignore errors */
145 parse_acl_file(arg, acl_list);
146 } else {
147 fprintf(stderr, "Unknown command `%s'\n", cmd);
148 goto err;
149 }
150 }
151
152 fclose(f);
153 return 0;
154
155 err:
156 fclose(f);
157 errno = EINVAL;
158 return -1;
159
160 }
161
162 static bool has_vnet_hdr(int fd)
163 {
164 unsigned int features = 0;
165
166 if (ioctl(fd, TUNGETFEATURES, &features) == -1) {
167 return false;
168 }
169
170 if (!(features & IFF_VNET_HDR)) {
171 return false;
172 }
173
174 return true;
175 }
176
177 static void prep_ifreq(struct ifreq *ifr, const char *ifname)
178 {
179 memset(ifr, 0, sizeof(*ifr));
180 snprintf(ifr->ifr_name, IFNAMSIZ, "%s", ifname);
181 }
182
183 static int send_fd(int c, int fd)
184 {
185 char msgbuf[CMSG_SPACE(sizeof(fd))];
186 struct msghdr msg = {
187 .msg_control = msgbuf,
188 .msg_controllen = sizeof(msgbuf),
189 };
190 struct cmsghdr *cmsg;
191 struct iovec iov;
192 char req[1] = { 0x00 };
193
194 cmsg = CMSG_FIRSTHDR(&msg);
195 cmsg->cmsg_level = SOL_SOCKET;
196 cmsg->cmsg_type = SCM_RIGHTS;
197 cmsg->cmsg_len = CMSG_LEN(sizeof(fd));
198 msg.msg_controllen = cmsg->cmsg_len;
199
200 iov.iov_base = req;
201 iov.iov_len = sizeof(req);
202
203 msg.msg_iov = &iov;
204 msg.msg_iovlen = 1;
205 memcpy(CMSG_DATA(cmsg), &fd, sizeof(fd));
206
207 return sendmsg(c, &msg, 0);
208 }
209
210 #ifdef CONFIG_LIBCAP
211 static int drop_privileges(void)
212 {
213 /* clear all capabilities */
214 capng_clear(CAPNG_SELECT_BOTH);
215
216 if (capng_update(CAPNG_ADD, CAPNG_EFFECTIVE | CAPNG_PERMITTED,
217 CAP_NET_ADMIN) < 0) {
218 return -1;
219 }
220
221 /* change to calling user's real uid and gid, retaining supplemental
222 * groups and CAP_NET_ADMIN */
223 if (capng_change_id(getuid(), getgid(), CAPNG_CLEAR_BOUNDING)) {
224 return -1;
225 }
226
227 return 0;
228 }
229 #endif
230
231 int main(int argc, char **argv)
232 {
233 struct ifreq ifr;
234 #ifndef SIOCBRADDIF
235 unsigned long ifargs[4];
236 #endif
237 int ifindex;
238 int fd = -1, ctlfd = -1, unixfd = -1;
239 int use_vnet = 0;
240 int mtu;
241 const char *bridge = NULL;
242 char iface[IFNAMSIZ];
243 int index;
244 ACLRule *acl_rule;
245 ACLList acl_list;
246 int access_allowed, access_denied;
247 int ret = EXIT_SUCCESS;
248
249 #ifdef CONFIG_LIBCAP
250 /* if we're run from an suid binary, immediately drop privileges preserving
251 * cap_net_admin */
252 if (geteuid() == 0 && getuid() != geteuid()) {
253 if (drop_privileges() == -1) {
254 fprintf(stderr, "failed to drop privileges\n");
255 return 1;
256 }
257 }
258 #endif
259
260 /* parse arguments */
261 for (index = 1; index < argc; index++) {
262 if (strcmp(argv[index], "--use-vnet") == 0) {
263 use_vnet = 1;
264 } else if (strncmp(argv[index], "--br=", 5) == 0) {
265 bridge = &argv[index][5];
266 } else if (strncmp(argv[index], "--fd=", 5) == 0) {
267 unixfd = atoi(&argv[index][5]);
268 } else {
269 usage();
270 return EXIT_FAILURE;
271 }
272 }
273
274 if (bridge == NULL || unixfd == -1) {
275 usage();
276 return EXIT_FAILURE;
277 }
278 if (strlen(bridge) >= IFNAMSIZ) {
279 fprintf(stderr, "name `%s' too long: %zu\n", bridge, strlen(bridge));
280 return EXIT_FAILURE;
281 }
282
283 /* parse default acl file */
284 QSIMPLEQ_INIT(&acl_list);
285 if (parse_acl_file(DEFAULT_ACL_FILE, &acl_list) == -1) {
286 fprintf(stderr, "failed to parse default acl file `%s'\n",
287 DEFAULT_ACL_FILE);
288 ret = EXIT_FAILURE;
289 goto cleanup;
290 }
291
292 /* validate bridge against acl -- default policy is to deny
293 * according acl policy if we have a deny and allow both
294 * then deny should always win over allow
295 */
296 access_allowed = 0;
297 access_denied = 0;
298 QSIMPLEQ_FOREACH(acl_rule, &acl_list, entry) {
299 switch (acl_rule->type) {
300 case ACL_ALLOW_ALL:
301 access_allowed = 1;
302 break;
303 case ACL_ALLOW:
304 if (strcmp(bridge, acl_rule->iface) == 0) {
305 access_allowed = 1;
306 }
307 break;
308 case ACL_DENY_ALL:
309 access_denied = 1;
310 break;
311 case ACL_DENY:
312 if (strcmp(bridge, acl_rule->iface) == 0) {
313 access_denied = 1;
314 }
315 break;
316 }
317 }
318
319 if ((access_allowed == 0) || (access_denied == 1)) {
320 fprintf(stderr, "access denied by acl file\n");
321 ret = EXIT_FAILURE;
322 goto cleanup;
323 }
324
325 /* open a socket to use to control the network interfaces */
326 ctlfd = socket(AF_INET, SOCK_STREAM, 0);
327 if (ctlfd == -1) {
328 fprintf(stderr, "failed to open control socket: %s\n", strerror(errno));
329 ret = EXIT_FAILURE;
330 goto cleanup;
331 }
332
333 /* open the tap device */
334 fd = open("/dev/net/tun", O_RDWR);
335 if (fd == -1) {
336 fprintf(stderr, "failed to open /dev/net/tun: %s\n", strerror(errno));
337 ret = EXIT_FAILURE;
338 goto cleanup;
339 }
340
341 /* request a tap device, disable PI, and add vnet header support if
342 * requested and it's available. */
343 prep_ifreq(&ifr, "tap%d");
344 ifr.ifr_flags = IFF_TAP|IFF_NO_PI;
345 if (use_vnet && has_vnet_hdr(fd)) {
346 ifr.ifr_flags |= IFF_VNET_HDR;
347 }
348
349 if (ioctl(fd, TUNSETIFF, &ifr) == -1) {
350 fprintf(stderr, "failed to create tun device: %s\n", strerror(errno));
351 ret = EXIT_FAILURE;
352 goto cleanup;
353 }
354
355 /* save tap device name */
356 snprintf(iface, sizeof(iface), "%s", ifr.ifr_name);
357
358 /* get the mtu of the bridge */
359 prep_ifreq(&ifr, bridge);
360 if (ioctl(ctlfd, SIOCGIFMTU, &ifr) == -1) {
361 fprintf(stderr, "failed to get mtu of bridge `%s': %s\n",
362 bridge, strerror(errno));
363 ret = EXIT_FAILURE;
364 goto cleanup;
365 }
366
367 /* save mtu */
368 mtu = ifr.ifr_mtu;
369
370 /* set the mtu of the interface based on the bridge */
371 prep_ifreq(&ifr, iface);
372 ifr.ifr_mtu = mtu;
373 if (ioctl(ctlfd, SIOCSIFMTU, &ifr) == -1) {
374 fprintf(stderr, "failed to set mtu of device `%s' to %d: %s\n",
375 iface, mtu, strerror(errno));
376 ret = EXIT_FAILURE;
377 goto cleanup;
378 }
379
380 /* Linux uses the lowest enslaved MAC address as the MAC address of
381 * the bridge. Set MAC address to a high value so that it doesn't
382 * affect the MAC address of the bridge.
383 */
384 if (ioctl(ctlfd, SIOCGIFHWADDR, &ifr) < 0) {
385 fprintf(stderr, "failed to get MAC address of device `%s': %s\n",
386 iface, strerror(errno));
387 ret = EXIT_FAILURE;
388 goto cleanup;
389 }
390 ifr.ifr_hwaddr.sa_data[0] = 0xFE;
391 if (ioctl(ctlfd, SIOCSIFHWADDR, &ifr) < 0) {
392 fprintf(stderr, "failed to set MAC address of device `%s': %s\n",
393 iface, strerror(errno));
394 ret = EXIT_FAILURE;
395 goto cleanup;
396 }
397
398 /* add the interface to the bridge */
399 prep_ifreq(&ifr, bridge);
400 ifindex = if_nametoindex(iface);
401 #ifndef SIOCBRADDIF
402 ifargs[0] = BRCTL_ADD_IF;
403 ifargs[1] = ifindex;
404 ifargs[2] = 0;
405 ifargs[3] = 0;
406 ifr.ifr_data = (void *)ifargs;
407 ret = ioctl(ctlfd, SIOCDEVPRIVATE, &ifr);
408 #else
409 ifr.ifr_ifindex = ifindex;
410 ret = ioctl(ctlfd, SIOCBRADDIF, &ifr);
411 #endif
412 if (ret == -1) {
413 fprintf(stderr, "failed to add interface `%s' to bridge `%s': %s\n",
414 iface, bridge, strerror(errno));
415 ret = EXIT_FAILURE;
416 goto cleanup;
417 }
418
419 /* bring the interface up */
420 prep_ifreq(&ifr, iface);
421 if (ioctl(ctlfd, SIOCGIFFLAGS, &ifr) == -1) {
422 fprintf(stderr, "failed to get interface flags for `%s': %s\n",
423 iface, strerror(errno));
424 ret = EXIT_FAILURE;
425 goto cleanup;
426 }
427
428 ifr.ifr_flags |= IFF_UP;
429 if (ioctl(ctlfd, SIOCSIFFLAGS, &ifr) == -1) {
430 fprintf(stderr, "failed to bring up interface `%s': %s\n",
431 iface, strerror(errno));
432 ret = EXIT_FAILURE;
433 goto cleanup;
434 }
435
436 /* write fd to the domain socket */
437 if (send_fd(unixfd, fd) == -1) {
438 fprintf(stderr, "failed to write fd to unix socket: %s\n",
439 strerror(errno));
440 ret = EXIT_FAILURE;
441 goto cleanup;
442 }
443
444 /* ... */
445
446 /* profit! */
447
448 cleanup:
449 if (fd >= 0) {
450 close(fd);
451 }
452 if (ctlfd >= 0) {
453 close(ctlfd);
454 }
455 while ((acl_rule = QSIMPLEQ_FIRST(&acl_list)) != NULL) {
456 QSIMPLEQ_REMOVE_HEAD(&acl_list, entry);
457 g_free(acl_rule);
458 }
459
460 return ret;
461 }