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1 | /* SPDX-License-Identifier: LGPL-2.1-or-later */ | |
2 | ||
3 | #include <net/if_arp.h> | |
4 | ||
5 | #include "sd-netlink.h" | |
6 | ||
7 | #include "alloc-util.h" | |
8 | #include "fd-util.h" | |
9 | #include "local-addresses.h" | |
10 | #include "macro.h" | |
11 | #include "netlink-util.h" | |
12 | #include "sort-util.h" | |
13 | ||
14 | static int address_compare(const struct local_address *a, const struct local_address *b) { | |
15 | int r; | |
16 | ||
17 | /* Order lowest scope first, IPv4 before IPv6, lowest interface index first */ | |
18 | ||
19 | if (a->family == AF_INET && b->family == AF_INET6) | |
20 | return -1; | |
21 | if (a->family == AF_INET6 && b->family == AF_INET) | |
22 | return 1; | |
23 | ||
24 | r = CMP(a->scope, b->scope); | |
25 | if (r != 0) | |
26 | return r; | |
27 | ||
28 | r = CMP(a->metric, b->metric); | |
29 | if (r != 0) | |
30 | return r; | |
31 | ||
32 | r = CMP(a->ifindex, b->ifindex); | |
33 | if (r != 0) | |
34 | return r; | |
35 | ||
36 | return memcmp(&a->address, &b->address, FAMILY_ADDRESS_SIZE(a->family)); | |
37 | } | |
38 | ||
39 | static void suppress_duplicates(struct local_address *list, size_t *n_list) { | |
40 | size_t old_size, new_size; | |
41 | ||
42 | /* Removes duplicate entries, assumes the list of addresses is already sorted. Updates in-place. */ | |
43 | ||
44 | if (*n_list < 2) /* list with less than two entries can't have duplicates */ | |
45 | return; | |
46 | ||
47 | old_size = *n_list; | |
48 | new_size = 1; | |
49 | ||
50 | for (size_t i = 1; i < old_size; i++) { | |
51 | ||
52 | if (address_compare(list + i, list + new_size - 1) == 0) | |
53 | continue; | |
54 | ||
55 | list[new_size++] = list[i]; | |
56 | } | |
57 | ||
58 | *n_list = new_size; | |
59 | } | |
60 | ||
61 | int local_addresses( | |
62 | sd_netlink *context, | |
63 | int ifindex, | |
64 | int af, | |
65 | struct local_address **ret) { | |
66 | ||
67 | _cleanup_(sd_netlink_message_unrefp) sd_netlink_message *req = NULL, *reply = NULL; | |
68 | _cleanup_(sd_netlink_unrefp) sd_netlink *rtnl = NULL; | |
69 | _cleanup_free_ struct local_address *list = NULL; | |
70 | size_t n_list = 0; | |
71 | sd_netlink_message *m; | |
72 | int r; | |
73 | ||
74 | if (context) | |
75 | rtnl = sd_netlink_ref(context); | |
76 | else { | |
77 | r = sd_netlink_open(&rtnl); | |
78 | if (r < 0) | |
79 | return r; | |
80 | } | |
81 | ||
82 | r = sd_rtnl_message_new_addr(rtnl, &req, RTM_GETADDR, 0, af); | |
83 | if (r < 0) | |
84 | return r; | |
85 | ||
86 | r = sd_netlink_message_request_dump(req, true); | |
87 | if (r < 0) | |
88 | return r; | |
89 | ||
90 | r = sd_netlink_call(rtnl, req, 0, &reply); | |
91 | if (r < 0) | |
92 | return r; | |
93 | ||
94 | for (m = reply; m; m = sd_netlink_message_next(m)) { | |
95 | struct local_address *a; | |
96 | unsigned char flags; | |
97 | uint16_t type; | |
98 | int ifi, family; | |
99 | ||
100 | r = sd_netlink_message_get_errno(m); | |
101 | if (r < 0) | |
102 | return r; | |
103 | ||
104 | r = sd_netlink_message_get_type(m, &type); | |
105 | if (r < 0) | |
106 | return r; | |
107 | if (type != RTM_NEWADDR) | |
108 | continue; | |
109 | ||
110 | r = sd_rtnl_message_addr_get_ifindex(m, &ifi); | |
111 | if (r < 0) | |
112 | return r; | |
113 | if (ifindex > 0 && ifi != ifindex) | |
114 | continue; | |
115 | ||
116 | r = sd_rtnl_message_addr_get_family(m, &family); | |
117 | if (r < 0) | |
118 | return r; | |
119 | if (af != AF_UNSPEC && af != family) | |
120 | continue; | |
121 | ||
122 | r = sd_rtnl_message_addr_get_flags(m, &flags); | |
123 | if (r < 0) | |
124 | return r; | |
125 | if (flags & IFA_F_DEPRECATED) | |
126 | continue; | |
127 | ||
128 | if (!GREEDY_REALLOC0(list, n_list+1)) | |
129 | return -ENOMEM; | |
130 | ||
131 | a = list + n_list; | |
132 | ||
133 | r = sd_rtnl_message_addr_get_scope(m, &a->scope); | |
134 | if (r < 0) | |
135 | return r; | |
136 | ||
137 | if (ifindex == 0 && IN_SET(a->scope, RT_SCOPE_HOST, RT_SCOPE_NOWHERE)) | |
138 | continue; | |
139 | ||
140 | switch (family) { | |
141 | ||
142 | case AF_INET: | |
143 | r = sd_netlink_message_read_in_addr(m, IFA_LOCAL, &a->address.in); | |
144 | if (r < 0) { | |
145 | r = sd_netlink_message_read_in_addr(m, IFA_ADDRESS, &a->address.in); | |
146 | if (r < 0) | |
147 | continue; | |
148 | } | |
149 | break; | |
150 | ||
151 | case AF_INET6: | |
152 | r = sd_netlink_message_read_in6_addr(m, IFA_LOCAL, &a->address.in6); | |
153 | if (r < 0) { | |
154 | r = sd_netlink_message_read_in6_addr(m, IFA_ADDRESS, &a->address.in6); | |
155 | if (r < 0) | |
156 | continue; | |
157 | } | |
158 | break; | |
159 | ||
160 | default: | |
161 | continue; | |
162 | } | |
163 | ||
164 | a->ifindex = ifi; | |
165 | a->family = family; | |
166 | ||
167 | n_list++; | |
168 | }; | |
169 | ||
170 | if (ret) { | |
171 | typesafe_qsort(list, n_list, address_compare); | |
172 | suppress_duplicates(list, &n_list); | |
173 | *ret = TAKE_PTR(list); | |
174 | } | |
175 | ||
176 | return (int) n_list; | |
177 | } | |
178 | ||
179 | static int add_local_gateway( | |
180 | struct local_address **list, | |
181 | size_t *n_list, | |
182 | int af, | |
183 | int ifindex, | |
184 | uint32_t metric, | |
185 | const RouteVia *via) { | |
186 | ||
187 | assert(list); | |
188 | assert(n_list); | |
189 | assert(via); | |
190 | ||
191 | if (af != AF_UNSPEC && af != via->family) | |
192 | return 0; | |
193 | ||
194 | if (!GREEDY_REALLOC(*list, *n_list + 1)) | |
195 | return -ENOMEM; | |
196 | ||
197 | (*list)[(*n_list)++] = (struct local_address) { | |
198 | .ifindex = ifindex, | |
199 | .metric = metric, | |
200 | .family = via->family, | |
201 | .address = via->address, | |
202 | }; | |
203 | ||
204 | return 0; | |
205 | } | |
206 | ||
207 | int local_gateways( | |
208 | sd_netlink *context, | |
209 | int ifindex, | |
210 | int af, | |
211 | struct local_address **ret) { | |
212 | ||
213 | _cleanup_(sd_netlink_message_unrefp) sd_netlink_message *req = NULL, *reply = NULL; | |
214 | _cleanup_(sd_netlink_unrefp) sd_netlink *rtnl = NULL; | |
215 | _cleanup_free_ struct local_address *list = NULL; | |
216 | size_t n_list = 0; | |
217 | int r; | |
218 | ||
219 | if (context) | |
220 | rtnl = sd_netlink_ref(context); | |
221 | else { | |
222 | r = sd_netlink_open(&rtnl); | |
223 | if (r < 0) | |
224 | return r; | |
225 | } | |
226 | ||
227 | r = sd_rtnl_message_new_route(rtnl, &req, RTM_GETROUTE, af, RTPROT_UNSPEC); | |
228 | if (r < 0) | |
229 | return r; | |
230 | ||
231 | r = sd_rtnl_message_route_set_type(req, RTN_UNICAST); | |
232 | if (r < 0) | |
233 | return r; | |
234 | ||
235 | r = sd_rtnl_message_route_set_table(req, RT_TABLE_MAIN); | |
236 | if (r < 0) | |
237 | return r; | |
238 | ||
239 | r = sd_netlink_message_request_dump(req, true); | |
240 | if (r < 0) | |
241 | return r; | |
242 | ||
243 | r = sd_netlink_call(rtnl, req, 0, &reply); | |
244 | if (r < 0) | |
245 | return r; | |
246 | ||
247 | for (sd_netlink_message *m = reply; m; m = sd_netlink_message_next(m)) { | |
248 | _cleanup_ordered_set_free_free_ OrderedSet *multipath_routes = NULL; | |
249 | _cleanup_free_ void *rta_multipath = NULL; | |
250 | union in_addr_union gateway; | |
251 | uint16_t type; | |
252 | unsigned char dst_len, src_len, table; | |
253 | uint32_t ifi = 0, metric = 0; | |
254 | size_t rta_len; | |
255 | int family; | |
256 | RouteVia via; | |
257 | ||
258 | r = sd_netlink_message_get_errno(m); | |
259 | if (r < 0) | |
260 | return r; | |
261 | ||
262 | r = sd_netlink_message_get_type(m, &type); | |
263 | if (r < 0) | |
264 | return r; | |
265 | if (type != RTM_NEWROUTE) | |
266 | continue; | |
267 | ||
268 | /* We only care for default routes */ | |
269 | r = sd_rtnl_message_route_get_dst_prefixlen(m, &dst_len); | |
270 | if (r < 0) | |
271 | return r; | |
272 | if (dst_len != 0) | |
273 | continue; | |
274 | ||
275 | r = sd_rtnl_message_route_get_src_prefixlen(m, &src_len); | |
276 | if (r < 0) | |
277 | return r; | |
278 | if (src_len != 0) | |
279 | continue; | |
280 | ||
281 | r = sd_rtnl_message_route_get_table(m, &table); | |
282 | if (r < 0) | |
283 | return r; | |
284 | if (table != RT_TABLE_MAIN) | |
285 | continue; | |
286 | ||
287 | r = sd_netlink_message_read_u32(m, RTA_PRIORITY, &metric); | |
288 | if (r < 0 && r != -ENODATA) | |
289 | return r; | |
290 | ||
291 | r = sd_rtnl_message_route_get_family(m, &family); | |
292 | if (r < 0) | |
293 | return r; | |
294 | if (!IN_SET(family, AF_INET, AF_INET6)) | |
295 | continue; | |
296 | ||
297 | r = sd_netlink_message_read_u32(m, RTA_OIF, &ifi); | |
298 | if (r < 0 && r != -ENODATA) | |
299 | return r; | |
300 | if (r >= 0) { | |
301 | if (ifi <= 0) | |
302 | return -EINVAL; | |
303 | if (ifindex > 0 && (int) ifi != ifindex) | |
304 | continue; | |
305 | ||
306 | r = netlink_message_read_in_addr_union(m, RTA_GATEWAY, family, &gateway); | |
307 | if (r < 0 && r != -ENODATA) | |
308 | return r; | |
309 | if (r >= 0) { | |
310 | via.family = family; | |
311 | via.address = gateway; | |
312 | r = add_local_gateway(&list, &n_list, af, ifi, metric, &via); | |
313 | if (r < 0) | |
314 | return r; | |
315 | ||
316 | continue; | |
317 | } | |
318 | ||
319 | if (family != AF_INET) | |
320 | continue; | |
321 | ||
322 | r = sd_netlink_message_read(m, RTA_VIA, sizeof(via), &via); | |
323 | if (r < 0 && r != -ENODATA) | |
324 | return r; | |
325 | if (r >= 0) { | |
326 | r = add_local_gateway(&list, &n_list, af, ifi, metric, &via); | |
327 | if (r < 0) | |
328 | return r; | |
329 | ||
330 | continue; | |
331 | } | |
332 | } | |
333 | ||
334 | r = sd_netlink_message_read_data(m, RTA_MULTIPATH, &rta_len, &rta_multipath); | |
335 | if (r < 0 && r != -ENODATA) | |
336 | return r; | |
337 | if (r >= 0) { | |
338 | MultipathRoute *mr; | |
339 | ||
340 | r = rtattr_read_nexthop(rta_multipath, rta_len, family, &multipath_routes); | |
341 | if (r < 0) | |
342 | return r; | |
343 | ||
344 | ORDERED_SET_FOREACH(mr, multipath_routes) { | |
345 | if (ifindex > 0 && mr->ifindex != ifindex) | |
346 | continue; | |
347 | ||
348 | r = add_local_gateway(&list, &n_list, af, ifi, metric, &mr->gateway); | |
349 | if (r < 0) | |
350 | return r; | |
351 | } | |
352 | } | |
353 | } | |
354 | ||
355 | if (ret) { | |
356 | typesafe_qsort(list, n_list, address_compare); | |
357 | suppress_duplicates(list, &n_list); | |
358 | *ret = TAKE_PTR(list); | |
359 | } | |
360 | ||
361 | return (int) n_list; | |
362 | } | |
363 | ||
364 | int local_outbounds( | |
365 | sd_netlink *context, | |
366 | int ifindex, | |
367 | int af, | |
368 | struct local_address **ret) { | |
369 | ||
370 | _cleanup_free_ struct local_address *list = NULL, *gateways = NULL; | |
371 | size_t n_list = 0; | |
372 | int r, n_gateways; | |
373 | ||
374 | /* Determines our default outbound addresses, i.e. the "primary" local addresses we use to talk to IP | |
375 | * addresses behind the default routes. This is still an address of the local host (i.e. this doesn't | |
376 | * resolve NAT or so), but it's the set of addresses the local IP stack most likely uses to talk to | |
377 | * other hosts. | |
378 | * | |
379 | * This works by connect()ing a SOCK_DGRAM socket to the local gateways, and then reading the IP | |
380 | * address off the socket that was chosen for the routing decision. */ | |
381 | ||
382 | n_gateways = local_gateways(context, ifindex, af, &gateways); | |
383 | if (n_gateways < 0) | |
384 | return n_gateways; | |
385 | if (n_gateways == 0) { | |
386 | /* No gateways? Then we have no outbound addresses either. */ | |
387 | if (ret) | |
388 | *ret = NULL; | |
389 | ||
390 | return 0; | |
391 | } | |
392 | ||
393 | for (int i = 0; i < n_gateways; i++) { | |
394 | _cleanup_close_ int fd = -1; | |
395 | union sockaddr_union sa; | |
396 | socklen_t salen; | |
397 | ||
398 | fd = socket(gateways[i].family, SOCK_DGRAM|SOCK_CLOEXEC|SOCK_NONBLOCK, 0); | |
399 | if (fd < 0) | |
400 | return -errno; | |
401 | ||
402 | switch (gateways[i].family) { | |
403 | ||
404 | case AF_INET: | |
405 | sa.in = (struct sockaddr_in) { | |
406 | .sin_family = AF_INET, | |
407 | .sin_addr = gateways[i].address.in, | |
408 | .sin_port = htobe16(53), /* doesn't really matter which port we pick — | |
409 | * we just care about the routing decision */ | |
410 | }; | |
411 | ||
412 | break; | |
413 | ||
414 | case AF_INET6: | |
415 | sa.in6 = (struct sockaddr_in6) { | |
416 | .sin6_family = AF_INET6, | |
417 | .sin6_addr = gateways[i].address.in6, | |
418 | .sin6_port = htobe16(53), | |
419 | .sin6_scope_id = gateways[i].ifindex, | |
420 | }; | |
421 | ||
422 | break; | |
423 | ||
424 | default: | |
425 | assert_not_reached("Unexpected protocol"); | |
426 | } | |
427 | ||
428 | /* So ideally we'd just use IP_UNICAST_IF here to pass the ifindex info to the kernel before | |
429 | * connect()ing, sot that it influences the routing decision. However, on current kernels | |
430 | * IP_UNICAST_IF doesn't actually influence the routing decision for UDP — which I think | |
431 | * should probably just be considered a bug. Once that bug is fixed this is the best API to | |
432 | * use, since it is the most lightweight. */ | |
433 | r = socket_set_unicast_if(fd, gateways[i].family, gateways[i].ifindex); | |
434 | if (r < 0) | |
435 | log_debug_errno(r, "Failed to set unicast interface index %i, ignoring: %m", gateways[i].ifindex); | |
436 | ||
437 | /* We'll also use SO_BINDTOINDEX. This requires CAP_NET_RAW on old kernels, hence there's a | |
438 | * good chance this fails. Since 5.7 this restriction was dropped and the first | |
439 | * SO_BINDTOINDEX on a socket may be done without privileges. This one has the benefit of | |
440 | * really influencing the routing decision, i.e. this one definitely works for us — as long | |
441 | * as we have the privileges for it. */ | |
442 | r = socket_bind_to_ifindex(fd, gateways[i].ifindex); | |
443 | if (r < 0) | |
444 | log_debug_errno(r, "Failed to bind socket to interface %i, ignoring: %m", gateways[i].ifindex); | |
445 | ||
446 | /* Let's now connect() to the UDP socket, forcing the kernel to make a routing decision and | |
447 | * auto-bind the socket. We ignore failures on this, since that failure might happen for a | |
448 | * multitude of reasons (policy/firewall issues, who knows?) and some of them might be | |
449 | * *after* the routing decision and the auto-binding already took place. If so we can still | |
450 | * make use of the binding and return it. Hence, let's not unnecessarily fail early here: we | |
451 | * can still easily detect if the auto-binding worked or not, by comparing the bound IP | |
452 | * address with zero — which we do below. */ | |
453 | if (connect(fd, &sa.sa, SOCKADDR_LEN(sa)) < 0) | |
454 | log_debug_errno(errno, "Failed to connect SOCK_DGRAM socket to gateway, ignoring: %m"); | |
455 | ||
456 | /* Let's now read the socket address of the socket. A routing decision should have been | |
457 | * made. Let's verify that and use the data. */ | |
458 | salen = SOCKADDR_LEN(sa); | |
459 | if (getsockname(fd, &sa.sa, &salen) < 0) | |
460 | return -errno; | |
461 | assert(sa.sa.sa_family == gateways[i].family); | |
462 | assert(salen == SOCKADDR_LEN(sa)); | |
463 | ||
464 | switch (gateways[i].family) { | |
465 | ||
466 | case AF_INET: | |
467 | if (in4_addr_is_null(&sa.in.sin_addr)) /* Auto-binding didn't work. :-( */ | |
468 | continue; | |
469 | ||
470 | if (!GREEDY_REALLOC(list, n_list+1)) | |
471 | return -ENOMEM; | |
472 | ||
473 | list[n_list++] = (struct local_address) { | |
474 | .family = gateways[i].family, | |
475 | .ifindex = gateways[i].ifindex, | |
476 | .address.in = sa.in.sin_addr, | |
477 | }; | |
478 | ||
479 | break; | |
480 | ||
481 | case AF_INET6: | |
482 | if (in6_addr_is_null(&sa.in6.sin6_addr)) | |
483 | continue; | |
484 | ||
485 | if (!GREEDY_REALLOC(list, n_list+1)) | |
486 | return -ENOMEM; | |
487 | ||
488 | list[n_list++] = (struct local_address) { | |
489 | .family = gateways[i].family, | |
490 | .ifindex = gateways[i].ifindex, | |
491 | .address.in6 = sa.in6.sin6_addr, | |
492 | }; | |
493 | break; | |
494 | ||
495 | default: | |
496 | assert_not_reached("Unexpected protocol"); | |
497 | } | |
498 | } | |
499 | ||
500 | if (ret) { | |
501 | typesafe_qsort(list, n_list, address_compare); | |
502 | suppress_duplicates(list, &n_list); | |
503 | *ret = TAKE_PTR(list); | |
504 | } | |
505 | ||
506 | return (int) n_list; | |
507 | } |