root / qemu-bridge-helper.c @ 89db9987
History | View | Annotate | Download (11.1 kB)
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 "config-host.h" |
17 |
|
18 |
#include <stdio.h> |
19 |
#include <errno.h> |
20 |
#include <fcntl.h> |
21 |
#include <unistd.h> |
22 |
#include <string.h> |
23 |
#include <stdlib.h> |
24 |
#include <stdbool.h> |
25 |
#include <ctype.h> |
26 |
#include <glib.h> |
27 |
|
28 |
#include <sys/types.h> |
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 (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 |
fclose(f); |
106 |
errno = EINVAL; |
107 |
return -1; |
108 |
} |
109 |
|
110 |
*arg = 0;
|
111 |
arg++; |
112 |
while (isspace(*arg)) {
|
113 |
arg++; |
114 |
} |
115 |
|
116 |
argend = arg + strlen(arg); |
117 |
while (arg != argend && isspace(*(argend - 1))) { |
118 |
argend--; |
119 |
} |
120 |
*argend = 0;
|
121 |
|
122 |
if (strcmp(cmd, "deny") == 0) { |
123 |
acl_rule = g_malloc(sizeof(*acl_rule));
|
124 |
if (strcmp(arg, "all") == 0) { |
125 |
acl_rule->type = ACL_DENY_ALL; |
126 |
} else {
|
127 |
acl_rule->type = ACL_DENY; |
128 |
snprintf(acl_rule->iface, IFNAMSIZ, "%s", arg);
|
129 |
} |
130 |
QSIMPLEQ_INSERT_TAIL(acl_list, acl_rule, entry); |
131 |
} else if (strcmp(cmd, "allow") == 0) { |
132 |
acl_rule = g_malloc(sizeof(*acl_rule));
|
133 |
if (strcmp(arg, "all") == 0) { |
134 |
acl_rule->type = ACL_ALLOW_ALL; |
135 |
} else {
|
136 |
acl_rule->type = ACL_ALLOW; |
137 |
snprintf(acl_rule->iface, IFNAMSIZ, "%s", arg);
|
138 |
} |
139 |
QSIMPLEQ_INSERT_TAIL(acl_list, acl_rule, entry); |
140 |
} else if (strcmp(cmd, "include") == 0) { |
141 |
/* ignore errors */
|
142 |
parse_acl_file(arg, acl_list); |
143 |
} else {
|
144 |
fprintf(stderr, "Unknown command `%s'\n", cmd);
|
145 |
fclose(f); |
146 |
errno = EINVAL; |
147 |
return -1; |
148 |
} |
149 |
} |
150 |
|
151 |
fclose(f); |
152 |
|
153 |
return 0; |
154 |
} |
155 |
|
156 |
static bool has_vnet_hdr(int fd) |
157 |
{ |
158 |
unsigned int features = 0; |
159 |
|
160 |
if (ioctl(fd, TUNGETFEATURES, &features) == -1) { |
161 |
return false; |
162 |
} |
163 |
|
164 |
if (!(features & IFF_VNET_HDR)) {
|
165 |
return false; |
166 |
} |
167 |
|
168 |
return true; |
169 |
} |
170 |
|
171 |
static void prep_ifreq(struct ifreq *ifr, const char *ifname) |
172 |
{ |
173 |
memset(ifr, 0, sizeof(*ifr)); |
174 |
snprintf(ifr->ifr_name, IFNAMSIZ, "%s", ifname);
|
175 |
} |
176 |
|
177 |
static int send_fd(int c, int fd) |
178 |
{ |
179 |
char msgbuf[CMSG_SPACE(sizeof(fd))]; |
180 |
struct msghdr msg = {
|
181 |
.msg_control = msgbuf, |
182 |
.msg_controllen = sizeof(msgbuf),
|
183 |
}; |
184 |
struct cmsghdr *cmsg;
|
185 |
struct iovec iov;
|
186 |
char req[1] = { 0x00 }; |
187 |
|
188 |
cmsg = CMSG_FIRSTHDR(&msg); |
189 |
cmsg->cmsg_level = SOL_SOCKET; |
190 |
cmsg->cmsg_type = SCM_RIGHTS; |
191 |
cmsg->cmsg_len = CMSG_LEN(sizeof(fd));
|
192 |
msg.msg_controllen = cmsg->cmsg_len; |
193 |
|
194 |
iov.iov_base = req; |
195 |
iov.iov_len = sizeof(req);
|
196 |
|
197 |
msg.msg_iov = &iov; |
198 |
msg.msg_iovlen = 1;
|
199 |
memcpy(CMSG_DATA(cmsg), &fd, sizeof(fd));
|
200 |
|
201 |
return sendmsg(c, &msg, 0); |
202 |
} |
203 |
|
204 |
#ifdef CONFIG_LIBCAP
|
205 |
static int drop_privileges(void) |
206 |
{ |
207 |
/* clear all capabilities */
|
208 |
capng_clear(CAPNG_SELECT_BOTH); |
209 |
|
210 |
if (capng_update(CAPNG_ADD, CAPNG_EFFECTIVE | CAPNG_PERMITTED,
|
211 |
CAP_NET_ADMIN) < 0) {
|
212 |
return -1; |
213 |
} |
214 |
|
215 |
/* change to calling user's real uid and gid, retaining supplemental
|
216 |
* groups and CAP_NET_ADMIN */
|
217 |
if (capng_change_id(getuid(), getgid(), CAPNG_CLEAR_BOUNDING)) {
|
218 |
return -1; |
219 |
} |
220 |
|
221 |
return 0; |
222 |
} |
223 |
#endif
|
224 |
|
225 |
int main(int argc, char **argv) |
226 |
{ |
227 |
struct ifreq ifr;
|
228 |
#ifndef SIOCBRADDIF
|
229 |
unsigned long ifargs[4]; |
230 |
#endif
|
231 |
int ifindex;
|
232 |
int fd, ctlfd, unixfd = -1; |
233 |
int use_vnet = 0; |
234 |
int mtu;
|
235 |
const char *bridge = NULL; |
236 |
char iface[IFNAMSIZ];
|
237 |
int index;
|
238 |
ACLRule *acl_rule; |
239 |
ACLList acl_list; |
240 |
int access_allowed, access_denied;
|
241 |
int ret = EXIT_SUCCESS;
|
242 |
|
243 |
#ifdef CONFIG_LIBCAP
|
244 |
/* if we're run from an suid binary, immediately drop privileges preserving
|
245 |
* cap_net_admin */
|
246 |
if (geteuid() == 0 && getuid() != geteuid()) { |
247 |
if (drop_privileges() == -1) { |
248 |
fprintf(stderr, "failed to drop privileges\n");
|
249 |
return 1; |
250 |
} |
251 |
} |
252 |
#endif
|
253 |
|
254 |
/* parse arguments */
|
255 |
for (index = 1; index < argc; index++) { |
256 |
if (strcmp(argv[index], "--use-vnet") == 0) { |
257 |
use_vnet = 1;
|
258 |
} else if (strncmp(argv[index], "--br=", 5) == 0) { |
259 |
bridge = &argv[index][5];
|
260 |
} else if (strncmp(argv[index], "--fd=", 5) == 0) { |
261 |
unixfd = atoi(&argv[index][5]);
|
262 |
} else {
|
263 |
usage(); |
264 |
return EXIT_FAILURE;
|
265 |
} |
266 |
} |
267 |
|
268 |
if (bridge == NULL || unixfd == -1) { |
269 |
usage(); |
270 |
return EXIT_FAILURE;
|
271 |
} |
272 |
|
273 |
/* parse default acl file */
|
274 |
QSIMPLEQ_INIT(&acl_list); |
275 |
if (parse_acl_file(DEFAULT_ACL_FILE, &acl_list) == -1) { |
276 |
fprintf(stderr, "failed to parse default acl file `%s'\n",
|
277 |
DEFAULT_ACL_FILE); |
278 |
ret = EXIT_FAILURE; |
279 |
goto cleanup;
|
280 |
} |
281 |
|
282 |
/* validate bridge against acl -- default policy is to deny
|
283 |
* according acl policy if we have a deny and allow both
|
284 |
* then deny should always win over allow
|
285 |
*/
|
286 |
access_allowed = 0;
|
287 |
access_denied = 0;
|
288 |
QSIMPLEQ_FOREACH(acl_rule, &acl_list, entry) { |
289 |
switch (acl_rule->type) {
|
290 |
case ACL_ALLOW_ALL:
|
291 |
access_allowed = 1;
|
292 |
break;
|
293 |
case ACL_ALLOW:
|
294 |
if (strcmp(bridge, acl_rule->iface) == 0) { |
295 |
access_allowed = 1;
|
296 |
} |
297 |
break;
|
298 |
case ACL_DENY_ALL:
|
299 |
access_denied = 1;
|
300 |
break;
|
301 |
case ACL_DENY:
|
302 |
if (strcmp(bridge, acl_rule->iface) == 0) { |
303 |
access_denied = 1;
|
304 |
} |
305 |
break;
|
306 |
} |
307 |
} |
308 |
|
309 |
if ((access_allowed == 0) || (access_denied == 1)) { |
310 |
fprintf(stderr, "access denied by acl file\n");
|
311 |
ret = EXIT_FAILURE; |
312 |
goto cleanup;
|
313 |
} |
314 |
|
315 |
/* open a socket to use to control the network interfaces */
|
316 |
ctlfd = socket(AF_INET, SOCK_STREAM, 0);
|
317 |
if (ctlfd == -1) { |
318 |
fprintf(stderr, "failed to open control socket: %s\n", strerror(errno));
|
319 |
ret = EXIT_FAILURE; |
320 |
goto cleanup;
|
321 |
} |
322 |
|
323 |
/* open the tap device */
|
324 |
fd = open("/dev/net/tun", O_RDWR);
|
325 |
if (fd == -1) { |
326 |
fprintf(stderr, "failed to open /dev/net/tun: %s\n", strerror(errno));
|
327 |
ret = EXIT_FAILURE; |
328 |
goto cleanup;
|
329 |
} |
330 |
|
331 |
/* request a tap device, disable PI, and add vnet header support if
|
332 |
* requested and it's available. */
|
333 |
prep_ifreq(&ifr, "tap%d");
|
334 |
ifr.ifr_flags = IFF_TAP|IFF_NO_PI; |
335 |
if (use_vnet && has_vnet_hdr(fd)) {
|
336 |
ifr.ifr_flags |= IFF_VNET_HDR; |
337 |
} |
338 |
|
339 |
if (ioctl(fd, TUNSETIFF, &ifr) == -1) { |
340 |
fprintf(stderr, "failed to create tun device: %s\n", strerror(errno));
|
341 |
ret = EXIT_FAILURE; |
342 |
goto cleanup;
|
343 |
} |
344 |
|
345 |
/* save tap device name */
|
346 |
snprintf(iface, sizeof(iface), "%s", ifr.ifr_name); |
347 |
|
348 |
/* get the mtu of the bridge */
|
349 |
prep_ifreq(&ifr, bridge); |
350 |
if (ioctl(ctlfd, SIOCGIFMTU, &ifr) == -1) { |
351 |
fprintf(stderr, "failed to get mtu of bridge `%s': %s\n",
|
352 |
bridge, strerror(errno)); |
353 |
ret = EXIT_FAILURE; |
354 |
goto cleanup;
|
355 |
} |
356 |
|
357 |
/* save mtu */
|
358 |
mtu = ifr.ifr_mtu; |
359 |
|
360 |
/* set the mtu of the interface based on the bridge */
|
361 |
prep_ifreq(&ifr, iface); |
362 |
ifr.ifr_mtu = mtu; |
363 |
if (ioctl(ctlfd, SIOCSIFMTU, &ifr) == -1) { |
364 |
fprintf(stderr, "failed to set mtu of device `%s' to %d: %s\n",
|
365 |
iface, mtu, strerror(errno)); |
366 |
ret = EXIT_FAILURE; |
367 |
goto cleanup;
|
368 |
} |
369 |
|
370 |
/* Linux uses the lowest enslaved MAC address as the MAC address of
|
371 |
* the bridge. Set MAC address to a high value so that it doesn't
|
372 |
* affect the MAC address of the bridge.
|
373 |
*/
|
374 |
if (ioctl(ctlfd, SIOCGIFHWADDR, &ifr) < 0) { |
375 |
fprintf(stderr, "failed to get MAC address of device `%s': %s\n",
|
376 |
iface, strerror(errno)); |
377 |
ret = EXIT_FAILURE; |
378 |
goto cleanup;
|
379 |
} |
380 |
ifr.ifr_hwaddr.sa_data[0] = 0xFE; |
381 |
if (ioctl(ctlfd, SIOCSIFHWADDR, &ifr) < 0) { |
382 |
fprintf(stderr, "failed to set MAC address of device `%s': %s\n",
|
383 |
iface, strerror(errno)); |
384 |
ret = EXIT_FAILURE; |
385 |
goto cleanup;
|
386 |
} |
387 |
|
388 |
/* add the interface to the bridge */
|
389 |
prep_ifreq(&ifr, bridge); |
390 |
ifindex = if_nametoindex(iface); |
391 |
#ifndef SIOCBRADDIF
|
392 |
ifargs[0] = BRCTL_ADD_IF;
|
393 |
ifargs[1] = ifindex;
|
394 |
ifargs[2] = 0; |
395 |
ifargs[3] = 0; |
396 |
ifr.ifr_data = (void *)ifargs;
|
397 |
ret = ioctl(ctlfd, SIOCDEVPRIVATE, &ifr); |
398 |
#else
|
399 |
ifr.ifr_ifindex = ifindex; |
400 |
ret = ioctl(ctlfd, SIOCBRADDIF, &ifr); |
401 |
#endif
|
402 |
if (ret == -1) { |
403 |
fprintf(stderr, "failed to add interface `%s' to bridge `%s': %s\n",
|
404 |
iface, bridge, strerror(errno)); |
405 |
ret = EXIT_FAILURE; |
406 |
goto cleanup;
|
407 |
} |
408 |
|
409 |
/* bring the interface up */
|
410 |
prep_ifreq(&ifr, iface); |
411 |
if (ioctl(ctlfd, SIOCGIFFLAGS, &ifr) == -1) { |
412 |
fprintf(stderr, "failed to get interface flags for `%s': %s\n",
|
413 |
iface, strerror(errno)); |
414 |
ret = EXIT_FAILURE; |
415 |
goto cleanup;
|
416 |
} |
417 |
|
418 |
ifr.ifr_flags |= IFF_UP; |
419 |
if (ioctl(ctlfd, SIOCSIFFLAGS, &ifr) == -1) { |
420 |
fprintf(stderr, "failed to bring up interface `%s': %s\n",
|
421 |
iface, strerror(errno)); |
422 |
ret = EXIT_FAILURE; |
423 |
goto cleanup;
|
424 |
} |
425 |
|
426 |
/* write fd to the domain socket */
|
427 |
if (send_fd(unixfd, fd) == -1) { |
428 |
fprintf(stderr, "failed to write fd to unix socket: %s\n",
|
429 |
strerror(errno)); |
430 |
ret = EXIT_FAILURE; |
431 |
goto cleanup;
|
432 |
} |
433 |
|
434 |
/* ... */
|
435 |
|
436 |
/* profit! */
|
437 |
|
438 |
cleanup:
|
439 |
|
440 |
while ((acl_rule = QSIMPLEQ_FIRST(&acl_list)) != NULL) { |
441 |
QSIMPLEQ_REMOVE_HEAD(&acl_list, entry); |
442 |
g_free(acl_rule); |
443 |
} |
444 |
|
445 |
return ret;
|
446 |
} |