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