Corey Bryant | 7b93fad | 2012-01-26 09:42:24 -0500 | [diff] [blame] | 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 | |
Peter Maydell | d38ea87 | 2016-01-29 17:50:05 +0000 | [diff] [blame] | 16 | #include "qemu/osdep.h" |
Corey Bryant | 7b93fad | 2012-01-26 09:42:24 -0500 | [diff] [blame] | 17 | |
Corey Bryant | bdef79a | 2012-01-26 09:42:25 -0500 | [diff] [blame] | 18 | #include <glib.h> |
Corey Bryant | 7b93fad | 2012-01-26 09:42:24 -0500 | [diff] [blame] | 19 | |
Corey Bryant | 7b93fad | 2012-01-26 09:42:24 -0500 | [diff] [blame] | 20 | #include <sys/ioctl.h> |
| 21 | #include <sys/socket.h> |
| 22 | #include <sys/un.h> |
| 23 | #include <sys/prctl.h> |
| 24 | |
| 25 | #include <net/if.h> |
| 26 | |
| 27 | #include <linux/sockios.h> |
| 28 | |
Corey Bryant | 34309d2 | 2012-07-12 09:24:31 -0400 | [diff] [blame] | 29 | #ifndef SIOCBRADDIF |
| 30 | #include <linux/if_bridge.h> |
| 31 | #endif |
| 32 | |
Paolo Bonzini | 1de7afc | 2012-12-17 18:20:00 +0100 | [diff] [blame] | 33 | #include "qemu/queue.h" |
Corey Bryant | bdef79a | 2012-01-26 09:42:25 -0500 | [diff] [blame] | 34 | |
Corey Bryant | 7b93fad | 2012-01-26 09:42:24 -0500 | [diff] [blame] | 35 | #include "net/tap-linux.h" |
| 36 | |
Corey Bryant | 47e9865 | 2012-01-26 09:42:26 -0500 | [diff] [blame] | 37 | #ifdef CONFIG_LIBCAP |
| 38 | #include <cap-ng.h> |
| 39 | #endif |
| 40 | |
Corey Bryant | bdef79a | 2012-01-26 09:42:25 -0500 | [diff] [blame] | 41 | #define DEFAULT_ACL_FILE CONFIG_QEMU_CONFDIR "/bridge.conf" |
| 42 | |
| 43 | enum { |
| 44 | ACL_ALLOW = 0, |
| 45 | ACL_ALLOW_ALL, |
| 46 | ACL_DENY, |
| 47 | ACL_DENY_ALL, |
| 48 | }; |
| 49 | |
| 50 | typedef struct ACLRule { |
| 51 | int type; |
| 52 | char iface[IFNAMSIZ]; |
| 53 | QSIMPLEQ_ENTRY(ACLRule) entry; |
| 54 | } ACLRule; |
| 55 | |
| 56 | typedef QSIMPLEQ_HEAD(ACLList, ACLRule) ACLList; |
| 57 | |
Corey Bryant | 7b93fad | 2012-01-26 09:42:24 -0500 | [diff] [blame] | 58 | static void usage(void) |
| 59 | { |
| 60 | fprintf(stderr, |
| 61 | "Usage: qemu-bridge-helper [--use-vnet] --br=bridge --fd=unixfd\n"); |
| 62 | } |
| 63 | |
Corey Bryant | bdef79a | 2012-01-26 09:42:25 -0500 | [diff] [blame] | 64 | static int parse_acl_file(const char *filename, ACLList *acl_list) |
| 65 | { |
| 66 | FILE *f; |
| 67 | char line[4096]; |
| 68 | ACLRule *acl_rule; |
| 69 | |
| 70 | f = fopen(filename, "r"); |
| 71 | if (f == NULL) { |
| 72 | return -1; |
| 73 | } |
| 74 | |
| 75 | while (fgets(line, sizeof(line), f) != NULL) { |
| 76 | char *ptr = line; |
| 77 | char *cmd, *arg, *argend; |
| 78 | |
| 79 | while (isspace(*ptr)) { |
| 80 | ptr++; |
| 81 | } |
| 82 | |
| 83 | /* skip comments and empty lines */ |
| 84 | if (*ptr == '#' || *ptr == 0) { |
| 85 | continue; |
| 86 | } |
| 87 | |
| 88 | cmd = ptr; |
| 89 | arg = strchr(cmd, ' '); |
| 90 | if (arg == NULL) { |
| 91 | arg = strchr(cmd, '\t'); |
| 92 | } |
| 93 | |
| 94 | if (arg == NULL) { |
| 95 | fprintf(stderr, "Invalid config line:\n %s\n", line); |
| 96 | fclose(f); |
| 97 | errno = EINVAL; |
| 98 | return -1; |
| 99 | } |
| 100 | |
| 101 | *arg = 0; |
| 102 | arg++; |
| 103 | while (isspace(*arg)) { |
| 104 | arg++; |
| 105 | } |
| 106 | |
| 107 | argend = arg + strlen(arg); |
| 108 | while (arg != argend && isspace(*(argend - 1))) { |
| 109 | argend--; |
| 110 | } |
| 111 | *argend = 0; |
| 112 | |
| 113 | if (strcmp(cmd, "deny") == 0) { |
| 114 | acl_rule = g_malloc(sizeof(*acl_rule)); |
| 115 | if (strcmp(arg, "all") == 0) { |
| 116 | acl_rule->type = ACL_DENY_ALL; |
| 117 | } else { |
| 118 | acl_rule->type = ACL_DENY; |
| 119 | snprintf(acl_rule->iface, IFNAMSIZ, "%s", arg); |
| 120 | } |
| 121 | QSIMPLEQ_INSERT_TAIL(acl_list, acl_rule, entry); |
| 122 | } else if (strcmp(cmd, "allow") == 0) { |
| 123 | acl_rule = g_malloc(sizeof(*acl_rule)); |
| 124 | if (strcmp(arg, "all") == 0) { |
| 125 | acl_rule->type = ACL_ALLOW_ALL; |
| 126 | } else { |
| 127 | acl_rule->type = ACL_ALLOW; |
| 128 | snprintf(acl_rule->iface, IFNAMSIZ, "%s", arg); |
| 129 | } |
| 130 | QSIMPLEQ_INSERT_TAIL(acl_list, acl_rule, entry); |
| 131 | } else if (strcmp(cmd, "include") == 0) { |
| 132 | /* ignore errors */ |
| 133 | parse_acl_file(arg, acl_list); |
| 134 | } else { |
| 135 | fprintf(stderr, "Unknown command `%s'\n", cmd); |
| 136 | fclose(f); |
| 137 | errno = EINVAL; |
| 138 | return -1; |
| 139 | } |
| 140 | } |
| 141 | |
| 142 | fclose(f); |
| 143 | |
| 144 | return 0; |
| 145 | } |
| 146 | |
Corey Bryant | 7b93fad | 2012-01-26 09:42:24 -0500 | [diff] [blame] | 147 | static bool has_vnet_hdr(int fd) |
| 148 | { |
| 149 | unsigned int features = 0; |
| 150 | |
| 151 | if (ioctl(fd, TUNGETFEATURES, &features) == -1) { |
| 152 | return false; |
| 153 | } |
| 154 | |
| 155 | if (!(features & IFF_VNET_HDR)) { |
| 156 | return false; |
| 157 | } |
| 158 | |
| 159 | return true; |
| 160 | } |
| 161 | |
| 162 | static void prep_ifreq(struct ifreq *ifr, const char *ifname) |
| 163 | { |
| 164 | memset(ifr, 0, sizeof(*ifr)); |
| 165 | snprintf(ifr->ifr_name, IFNAMSIZ, "%s", ifname); |
| 166 | } |
| 167 | |
| 168 | static int send_fd(int c, int fd) |
| 169 | { |
| 170 | char msgbuf[CMSG_SPACE(sizeof(fd))]; |
| 171 | struct msghdr msg = { |
| 172 | .msg_control = msgbuf, |
| 173 | .msg_controllen = sizeof(msgbuf), |
| 174 | }; |
| 175 | struct cmsghdr *cmsg; |
| 176 | struct iovec iov; |
| 177 | char req[1] = { 0x00 }; |
| 178 | |
| 179 | cmsg = CMSG_FIRSTHDR(&msg); |
| 180 | cmsg->cmsg_level = SOL_SOCKET; |
| 181 | cmsg->cmsg_type = SCM_RIGHTS; |
| 182 | cmsg->cmsg_len = CMSG_LEN(sizeof(fd)); |
| 183 | msg.msg_controllen = cmsg->cmsg_len; |
| 184 | |
| 185 | iov.iov_base = req; |
| 186 | iov.iov_len = sizeof(req); |
| 187 | |
| 188 | msg.msg_iov = &iov; |
| 189 | msg.msg_iovlen = 1; |
| 190 | memcpy(CMSG_DATA(cmsg), &fd, sizeof(fd)); |
| 191 | |
| 192 | return sendmsg(c, &msg, 0); |
| 193 | } |
| 194 | |
Corey Bryant | 47e9865 | 2012-01-26 09:42:26 -0500 | [diff] [blame] | 195 | #ifdef CONFIG_LIBCAP |
| 196 | static int drop_privileges(void) |
| 197 | { |
| 198 | /* clear all capabilities */ |
| 199 | capng_clear(CAPNG_SELECT_BOTH); |
| 200 | |
| 201 | if (capng_update(CAPNG_ADD, CAPNG_EFFECTIVE | CAPNG_PERMITTED, |
| 202 | CAP_NET_ADMIN) < 0) { |
| 203 | return -1; |
| 204 | } |
| 205 | |
| 206 | /* change to calling user's real uid and gid, retaining supplemental |
| 207 | * groups and CAP_NET_ADMIN */ |
| 208 | if (capng_change_id(getuid(), getgid(), CAPNG_CLEAR_BOUNDING)) { |
| 209 | return -1; |
| 210 | } |
| 211 | |
| 212 | return 0; |
| 213 | } |
| 214 | #endif |
| 215 | |
Corey Bryant | 7b93fad | 2012-01-26 09:42:24 -0500 | [diff] [blame] | 216 | int main(int argc, char **argv) |
| 217 | { |
| 218 | struct ifreq ifr; |
Corey Bryant | 34309d2 | 2012-07-12 09:24:31 -0400 | [diff] [blame] | 219 | #ifndef SIOCBRADDIF |
| 220 | unsigned long ifargs[4]; |
| 221 | #endif |
| 222 | int ifindex; |
Gonglei | eb3f45c | 2014-06-10 17:20:25 +0800 | [diff] [blame] | 223 | int fd = -1, ctlfd = -1, unixfd = -1; |
Corey Bryant | 7b93fad | 2012-01-26 09:42:24 -0500 | [diff] [blame] | 224 | int use_vnet = 0; |
| 225 | int mtu; |
| 226 | const char *bridge = NULL; |
| 227 | char iface[IFNAMSIZ]; |
| 228 | int index; |
Corey Bryant | bdef79a | 2012-01-26 09:42:25 -0500 | [diff] [blame] | 229 | ACLRule *acl_rule; |
| 230 | ACLList acl_list; |
| 231 | int access_allowed, access_denied; |
Corey Bryant | 7b93fad | 2012-01-26 09:42:24 -0500 | [diff] [blame] | 232 | int ret = EXIT_SUCCESS; |
| 233 | |
Corey Bryant | 47e9865 | 2012-01-26 09:42:26 -0500 | [diff] [blame] | 234 | #ifdef CONFIG_LIBCAP |
| 235 | /* if we're run from an suid binary, immediately drop privileges preserving |
| 236 | * cap_net_admin */ |
| 237 | if (geteuid() == 0 && getuid() != geteuid()) { |
| 238 | if (drop_privileges() == -1) { |
| 239 | fprintf(stderr, "failed to drop privileges\n"); |
| 240 | return 1; |
| 241 | } |
| 242 | } |
| 243 | #endif |
| 244 | |
Corey Bryant | 7b93fad | 2012-01-26 09:42:24 -0500 | [diff] [blame] | 245 | /* parse arguments */ |
| 246 | for (index = 1; index < argc; index++) { |
| 247 | if (strcmp(argv[index], "--use-vnet") == 0) { |
| 248 | use_vnet = 1; |
| 249 | } else if (strncmp(argv[index], "--br=", 5) == 0) { |
| 250 | bridge = &argv[index][5]; |
| 251 | } else if (strncmp(argv[index], "--fd=", 5) == 0) { |
| 252 | unixfd = atoi(&argv[index][5]); |
| 253 | } else { |
| 254 | usage(); |
| 255 | return EXIT_FAILURE; |
| 256 | } |
| 257 | } |
| 258 | |
| 259 | if (bridge == NULL || unixfd == -1) { |
| 260 | usage(); |
| 261 | return EXIT_FAILURE; |
| 262 | } |
| 263 | |
Corey Bryant | bdef79a | 2012-01-26 09:42:25 -0500 | [diff] [blame] | 264 | /* parse default acl file */ |
| 265 | QSIMPLEQ_INIT(&acl_list); |
| 266 | if (parse_acl_file(DEFAULT_ACL_FILE, &acl_list) == -1) { |
| 267 | fprintf(stderr, "failed to parse default acl file `%s'\n", |
| 268 | DEFAULT_ACL_FILE); |
| 269 | ret = EXIT_FAILURE; |
| 270 | goto cleanup; |
| 271 | } |
| 272 | |
| 273 | /* validate bridge against acl -- default policy is to deny |
| 274 | * according acl policy if we have a deny and allow both |
| 275 | * then deny should always win over allow |
| 276 | */ |
| 277 | access_allowed = 0; |
| 278 | access_denied = 0; |
| 279 | QSIMPLEQ_FOREACH(acl_rule, &acl_list, entry) { |
| 280 | switch (acl_rule->type) { |
| 281 | case ACL_ALLOW_ALL: |
| 282 | access_allowed = 1; |
| 283 | break; |
| 284 | case ACL_ALLOW: |
| 285 | if (strcmp(bridge, acl_rule->iface) == 0) { |
| 286 | access_allowed = 1; |
| 287 | } |
| 288 | break; |
| 289 | case ACL_DENY_ALL: |
| 290 | access_denied = 1; |
| 291 | break; |
| 292 | case ACL_DENY: |
| 293 | if (strcmp(bridge, acl_rule->iface) == 0) { |
| 294 | access_denied = 1; |
| 295 | } |
| 296 | break; |
| 297 | } |
| 298 | } |
| 299 | |
| 300 | if ((access_allowed == 0) || (access_denied == 1)) { |
| 301 | fprintf(stderr, "access denied by acl file\n"); |
| 302 | ret = EXIT_FAILURE; |
| 303 | goto cleanup; |
| 304 | } |
| 305 | |
Corey Bryant | 7b93fad | 2012-01-26 09:42:24 -0500 | [diff] [blame] | 306 | /* open a socket to use to control the network interfaces */ |
| 307 | ctlfd = socket(AF_INET, SOCK_STREAM, 0); |
| 308 | if (ctlfd == -1) { |
| 309 | fprintf(stderr, "failed to open control socket: %s\n", strerror(errno)); |
| 310 | ret = EXIT_FAILURE; |
| 311 | goto cleanup; |
| 312 | } |
| 313 | |
| 314 | /* open the tap device */ |
| 315 | fd = open("/dev/net/tun", O_RDWR); |
| 316 | if (fd == -1) { |
| 317 | fprintf(stderr, "failed to open /dev/net/tun: %s\n", strerror(errno)); |
| 318 | ret = EXIT_FAILURE; |
| 319 | goto cleanup; |
| 320 | } |
| 321 | |
| 322 | /* request a tap device, disable PI, and add vnet header support if |
| 323 | * requested and it's available. */ |
| 324 | prep_ifreq(&ifr, "tap%d"); |
| 325 | ifr.ifr_flags = IFF_TAP|IFF_NO_PI; |
| 326 | if (use_vnet && has_vnet_hdr(fd)) { |
| 327 | ifr.ifr_flags |= IFF_VNET_HDR; |
| 328 | } |
| 329 | |
| 330 | if (ioctl(fd, TUNSETIFF, &ifr) == -1) { |
| 331 | fprintf(stderr, "failed to create tun device: %s\n", strerror(errno)); |
| 332 | ret = EXIT_FAILURE; |
| 333 | goto cleanup; |
| 334 | } |
| 335 | |
| 336 | /* save tap device name */ |
| 337 | snprintf(iface, sizeof(iface), "%s", ifr.ifr_name); |
| 338 | |
| 339 | /* get the mtu of the bridge */ |
| 340 | prep_ifreq(&ifr, bridge); |
| 341 | if (ioctl(ctlfd, SIOCGIFMTU, &ifr) == -1) { |
| 342 | fprintf(stderr, "failed to get mtu of bridge `%s': %s\n", |
| 343 | bridge, strerror(errno)); |
| 344 | ret = EXIT_FAILURE; |
| 345 | goto cleanup; |
| 346 | } |
| 347 | |
| 348 | /* save mtu */ |
| 349 | mtu = ifr.ifr_mtu; |
| 350 | |
| 351 | /* set the mtu of the interface based on the bridge */ |
| 352 | prep_ifreq(&ifr, iface); |
| 353 | ifr.ifr_mtu = mtu; |
| 354 | if (ioctl(ctlfd, SIOCSIFMTU, &ifr) == -1) { |
| 355 | fprintf(stderr, "failed to set mtu of device `%s' to %d: %s\n", |
| 356 | iface, mtu, strerror(errno)); |
| 357 | ret = EXIT_FAILURE; |
| 358 | goto cleanup; |
| 359 | } |
| 360 | |
Paolo Bonzini | 226ecab | 2013-03-22 17:57:48 +0100 | [diff] [blame] | 361 | /* Linux uses the lowest enslaved MAC address as the MAC address of |
| 362 | * the bridge. Set MAC address to a high value so that it doesn't |
| 363 | * affect the MAC address of the bridge. |
| 364 | */ |
| 365 | if (ioctl(ctlfd, SIOCGIFHWADDR, &ifr) < 0) { |
| 366 | fprintf(stderr, "failed to get MAC address of device `%s': %s\n", |
| 367 | iface, strerror(errno)); |
| 368 | ret = EXIT_FAILURE; |
| 369 | goto cleanup; |
| 370 | } |
| 371 | ifr.ifr_hwaddr.sa_data[0] = 0xFE; |
| 372 | if (ioctl(ctlfd, SIOCSIFHWADDR, &ifr) < 0) { |
| 373 | fprintf(stderr, "failed to set MAC address of device `%s': %s\n", |
| 374 | iface, strerror(errno)); |
| 375 | ret = EXIT_FAILURE; |
| 376 | goto cleanup; |
| 377 | } |
| 378 | |
Corey Bryant | 7b93fad | 2012-01-26 09:42:24 -0500 | [diff] [blame] | 379 | /* add the interface to the bridge */ |
| 380 | prep_ifreq(&ifr, bridge); |
Corey Bryant | 34309d2 | 2012-07-12 09:24:31 -0400 | [diff] [blame] | 381 | ifindex = if_nametoindex(iface); |
| 382 | #ifndef SIOCBRADDIF |
| 383 | ifargs[0] = BRCTL_ADD_IF; |
| 384 | ifargs[1] = ifindex; |
| 385 | ifargs[2] = 0; |
| 386 | ifargs[3] = 0; |
| 387 | ifr.ifr_data = (void *)ifargs; |
| 388 | ret = ioctl(ctlfd, SIOCDEVPRIVATE, &ifr); |
| 389 | #else |
| 390 | ifr.ifr_ifindex = ifindex; |
| 391 | ret = ioctl(ctlfd, SIOCBRADDIF, &ifr); |
| 392 | #endif |
| 393 | if (ret == -1) { |
Corey Bryant | 7b93fad | 2012-01-26 09:42:24 -0500 | [diff] [blame] | 394 | fprintf(stderr, "failed to add interface `%s' to bridge `%s': %s\n", |
| 395 | iface, bridge, strerror(errno)); |
| 396 | ret = EXIT_FAILURE; |
| 397 | goto cleanup; |
| 398 | } |
| 399 | |
| 400 | /* bring the interface up */ |
| 401 | prep_ifreq(&ifr, iface); |
| 402 | if (ioctl(ctlfd, SIOCGIFFLAGS, &ifr) == -1) { |
| 403 | fprintf(stderr, "failed to get interface flags for `%s': %s\n", |
| 404 | iface, strerror(errno)); |
| 405 | ret = EXIT_FAILURE; |
| 406 | goto cleanup; |
| 407 | } |
| 408 | |
| 409 | ifr.ifr_flags |= IFF_UP; |
| 410 | if (ioctl(ctlfd, SIOCSIFFLAGS, &ifr) == -1) { |
| 411 | fprintf(stderr, "failed to bring up interface `%s': %s\n", |
| 412 | iface, strerror(errno)); |
| 413 | ret = EXIT_FAILURE; |
| 414 | goto cleanup; |
| 415 | } |
| 416 | |
| 417 | /* write fd to the domain socket */ |
| 418 | if (send_fd(unixfd, fd) == -1) { |
| 419 | fprintf(stderr, "failed to write fd to unix socket: %s\n", |
| 420 | strerror(errno)); |
| 421 | ret = EXIT_FAILURE; |
| 422 | goto cleanup; |
| 423 | } |
| 424 | |
| 425 | /* ... */ |
| 426 | |
| 427 | /* profit! */ |
| 428 | |
| 429 | cleanup: |
Gonglei | eb3f45c | 2014-06-10 17:20:25 +0800 | [diff] [blame] | 430 | if (fd >= 0) { |
| 431 | close(fd); |
| 432 | } |
| 433 | if (ctlfd >= 0) { |
| 434 | close(ctlfd); |
| 435 | } |
Corey Bryant | bdef79a | 2012-01-26 09:42:25 -0500 | [diff] [blame] | 436 | while ((acl_rule = QSIMPLEQ_FIRST(&acl_list)) != NULL) { |
| 437 | QSIMPLEQ_REMOVE_HEAD(&acl_list, entry); |
| 438 | g_free(acl_rule); |
| 439 | } |
| 440 | |
Corey Bryant | 7b93fad | 2012-01-26 09:42:24 -0500 | [diff] [blame] | 441 | return ret; |
| 442 | } |