2 * libudev - interface to udev device information
4 * Copyright (C) 2008-2010 Kay Sievers <kay.sievers@vrfy.org>
6 * This library is free software; you can redistribute it and/or
7 * modify it under the terms of the GNU Lesser General Public
8 * License as published by the Free Software Foundation; either
9 * version 2.1 of the License, or (at your option) any later version.
21 #include <sys/socket.h>
23 #include <arpa/inet.h>
24 #include <linux/netlink.h>
25 #include <linux/filter.h>
28 #include "libudev-private.h"
29 #include "socket-util.h"
32 * SECTION:libudev-monitor
33 * @short_description: device event source
35 * Connects to a device event source.
41 * Opaque object handling an event source.
47 union sockaddr_union snl;
48 union sockaddr_union snl_trusted_sender;
49 union sockaddr_union snl_destination;
51 struct udev_list filter_subsystem_list;
52 struct udev_list filter_tag_list;
56 enum udev_monitor_netlink_group {
62 #define UDEV_MONITOR_MAGIC 0xfeedcafe
63 struct udev_monitor_netlink_header {
64 /* "libudev" prefix to distinguish libudev and kernel messages */
67 * magic to protect against daemon <-> library message format mismatch
68 * used in the kernel from socket filter rules; needs to be stored in network order
71 /* total length of header structure known to the sender */
72 unsigned int header_size;
73 /* properties string buffer */
74 unsigned int properties_off;
75 unsigned int properties_len;
77 * hashes of primary device properties strings, to let libudev subscribers
78 * use in-kernel socket filters; values need to be stored in network order
80 unsigned int filter_subsystem_hash;
81 unsigned int filter_devtype_hash;
82 unsigned int filter_tag_bloom_hi;
83 unsigned int filter_tag_bloom_lo;
86 static struct udev_monitor *udev_monitor_new(struct udev *udev)
88 struct udev_monitor *udev_monitor;
90 udev_monitor = calloc(1, sizeof(struct udev_monitor));
91 if (udev_monitor == NULL)
93 udev_monitor->refcount = 1;
94 udev_monitor->udev = udev;
95 udev_list_init(udev, &udev_monitor->filter_subsystem_list, false);
96 udev_list_init(udev, &udev_monitor->filter_tag_list, true);
101 * udev_monitor_new_from_socket:
102 * @udev: udev library context
103 * @socket_path: unix socket path
105 * This function is removed from libudev and will not do anything.
109 _public_ struct udev_monitor *udev_monitor_new_from_socket(struct udev *udev, const char *socket_path)
115 struct udev_monitor *udev_monitor_new_from_netlink_fd(struct udev *udev, const char *name, int fd)
117 struct udev_monitor *udev_monitor;
124 group = UDEV_MONITOR_NONE;
125 else if (strcmp(name, "udev") == 0)
126 group = UDEV_MONITOR_UDEV;
127 else if (strcmp(name, "kernel") == 0)
128 group = UDEV_MONITOR_KERNEL;
132 udev_monitor = udev_monitor_new(udev);
133 if (udev_monitor == NULL)
137 udev_monitor->sock = socket(PF_NETLINK, SOCK_RAW|SOCK_CLOEXEC|SOCK_NONBLOCK, NETLINK_KOBJECT_UEVENT);
138 if (udev_monitor->sock == -1) {
139 err(udev, "error getting socket: %m\n");
144 udev_monitor->bound = true;
145 udev_monitor->sock = fd;
148 udev_monitor->snl.nl.nl_family = AF_NETLINK;
149 udev_monitor->snl.nl.nl_groups = group;
151 /* default destination for sending */
152 udev_monitor->snl_destination.nl.nl_family = AF_NETLINK;
153 udev_monitor->snl_destination.nl.nl_groups = UDEV_MONITOR_UDEV;
159 * udev_monitor_new_from_netlink:
160 * @udev: udev library context
161 * @name: name of event source
163 * Create new udev monitor and connect to a specified event
164 * source. Valid sources identifiers are "udev" and "kernel".
166 * Applications should usually not connect directly to the
167 * "kernel" events, because the devices might not be useable
168 * at that time, before udev has configured them, and created
169 * device nodes. Accessing devices at the same time as udev,
170 * might result in unpredictable behavior. The "udev" events
171 * are sent out after udev has finished its event processing,
172 * all rules have been processed, and needed device nodes are
175 * The initial refcount is 1, and needs to be decremented to
176 * release the resources of the udev monitor.
178 * Returns: a new udev monitor, or #NULL, in case of an error
180 _public_ struct udev_monitor *udev_monitor_new_from_netlink(struct udev *udev, const char *name)
182 return udev_monitor_new_from_netlink_fd(udev, name, -1);
185 static inline void bpf_stmt(struct sock_filter *inss, unsigned int *i,
186 unsigned short code, unsigned int data)
188 struct sock_filter *ins = &inss[*i];
195 static inline void bpf_jmp(struct sock_filter *inss, unsigned int *i,
196 unsigned short code, unsigned int data,
197 unsigned short jt, unsigned short jf)
199 struct sock_filter *ins = &inss[*i];
209 * udev_monitor_filter_update:
210 * @udev_monitor: monitor
212 * Update the installed socket filter. This is only needed,
213 * if the filter was removed or changed.
215 * Returns: 0 on success, otherwise a negative error value.
217 _public_ int udev_monitor_filter_update(struct udev_monitor *udev_monitor)
219 struct sock_filter ins[512];
220 struct sock_fprog filter;
222 struct udev_list_entry *list_entry;
225 if (udev_list_get_entry(&udev_monitor->filter_subsystem_list) == NULL &&
226 udev_list_get_entry(&udev_monitor->filter_tag_list) == NULL)
229 memset(ins, 0x00, sizeof(ins));
232 /* load magic in A */
233 bpf_stmt(ins, &i, BPF_LD|BPF_W|BPF_ABS, offsetof(struct udev_monitor_netlink_header, magic));
234 /* jump if magic matches */
235 bpf_jmp(ins, &i, BPF_JMP|BPF_JEQ|BPF_K, UDEV_MONITOR_MAGIC, 1, 0);
236 /* wrong magic, pass packet */
237 bpf_stmt(ins, &i, BPF_RET|BPF_K, 0xffffffff);
239 if (udev_list_get_entry(&udev_monitor->filter_tag_list) != NULL) {
242 /* count tag matches, to calculate end of tag match block */
244 udev_list_entry_foreach(list_entry, udev_list_get_entry(&udev_monitor->filter_tag_list))
247 /* add all tags matches */
248 udev_list_entry_foreach(list_entry, udev_list_get_entry(&udev_monitor->filter_tag_list)) {
249 uint64_t tag_bloom_bits = util_string_bloom64(udev_list_entry_get_name(list_entry));
250 uint32_t tag_bloom_hi = tag_bloom_bits >> 32;
251 uint32_t tag_bloom_lo = tag_bloom_bits & 0xffffffff;
253 /* load device bloom bits in A */
254 bpf_stmt(ins, &i, BPF_LD|BPF_W|BPF_ABS, offsetof(struct udev_monitor_netlink_header, filter_tag_bloom_hi));
255 /* clear bits (tag bits & bloom bits) */
256 bpf_stmt(ins, &i, BPF_ALU|BPF_AND|BPF_K, tag_bloom_hi);
257 /* jump to next tag if it does not match */
258 bpf_jmp(ins, &i, BPF_JMP|BPF_JEQ|BPF_K, tag_bloom_hi, 0, 3);
260 /* load device bloom bits in A */
261 bpf_stmt(ins, &i, BPF_LD|BPF_W|BPF_ABS, offsetof(struct udev_monitor_netlink_header, filter_tag_bloom_lo));
262 /* clear bits (tag bits & bloom bits) */
263 bpf_stmt(ins, &i, BPF_ALU|BPF_AND|BPF_K, tag_bloom_lo);
264 /* jump behind end of tag match block if tag matches */
266 bpf_jmp(ins, &i, BPF_JMP|BPF_JEQ|BPF_K, tag_bloom_lo, 1 + (tag_matches * 6), 0);
269 /* nothing matched, drop packet */
270 bpf_stmt(ins, &i, BPF_RET|BPF_K, 0);
273 /* add all subsystem matches */
274 if (udev_list_get_entry(&udev_monitor->filter_subsystem_list) != NULL) {
275 udev_list_entry_foreach(list_entry, udev_list_get_entry(&udev_monitor->filter_subsystem_list)) {
276 unsigned int hash = util_string_hash32(udev_list_entry_get_name(list_entry));
278 /* load device subsystem value in A */
279 bpf_stmt(ins, &i, BPF_LD|BPF_W|BPF_ABS, offsetof(struct udev_monitor_netlink_header, filter_subsystem_hash));
280 if (udev_list_entry_get_value(list_entry) == NULL) {
281 /* jump if subsystem does not match */
282 bpf_jmp(ins, &i, BPF_JMP|BPF_JEQ|BPF_K, hash, 0, 1);
284 /* jump if subsystem does not match */
285 bpf_jmp(ins, &i, BPF_JMP|BPF_JEQ|BPF_K, hash, 0, 3);
287 /* load device devtype value in A */
288 bpf_stmt(ins, &i, BPF_LD|BPF_W|BPF_ABS, offsetof(struct udev_monitor_netlink_header, filter_devtype_hash));
289 /* jump if value does not match */
290 hash = util_string_hash32(udev_list_entry_get_value(list_entry));
291 bpf_jmp(ins, &i, BPF_JMP|BPF_JEQ|BPF_K, hash, 0, 1);
294 /* matched, pass packet */
295 bpf_stmt(ins, &i, BPF_RET|BPF_K, 0xffffffff);
297 if (i+1 >= ARRAY_SIZE(ins))
301 /* nothing matched, drop packet */
302 bpf_stmt(ins, &i, BPF_RET|BPF_K, 0);
305 /* matched, pass packet */
306 bpf_stmt(ins, &i, BPF_RET|BPF_K, 0xffffffff);
309 memset(&filter, 0x00, sizeof(filter));
312 err = setsockopt(udev_monitor->sock, SOL_SOCKET, SO_ATTACH_FILTER, &filter, sizeof(filter));
316 int udev_monitor_allow_unicast_sender(struct udev_monitor *udev_monitor, struct udev_monitor *sender)
318 udev_monitor->snl_trusted_sender.nl.nl_pid = sender->snl.nl.nl_pid;
322 * udev_monitor_enable_receiving:
323 * @udev_monitor: the monitor which should receive events
325 * Binds the @udev_monitor socket to the event source.
327 * Returns: 0 on success, otherwise a negative error value.
329 _public_ int udev_monitor_enable_receiving(struct udev_monitor *udev_monitor)
334 if (udev_monitor->snl.nl.nl_family == 0)
337 udev_monitor_filter_update(udev_monitor);
339 if (!udev_monitor->bound) {
340 err = bind(udev_monitor->sock,
341 &udev_monitor->snl.sa, sizeof(struct sockaddr_nl));
343 udev_monitor->bound = true;
347 union sockaddr_union snl;
351 * get the address the kernel has assigned us
352 * it is usually, but not necessarily the pid
354 addrlen = sizeof(struct sockaddr_nl);
355 err = getsockname(udev_monitor->sock, &snl.sa, &addrlen);
357 udev_monitor->snl.nl.nl_pid = snl.nl.nl_pid;
359 err(udev_monitor->udev, "bind failed: %m\n");
363 /* enable receiving of sender credentials */
364 setsockopt(udev_monitor->sock, SOL_SOCKET, SO_PASSCRED, &on, sizeof(on));
369 * udev_monitor_set_receive_buffer_size:
370 * @udev_monitor: the monitor which should receive events
371 * @size: the size in bytes
373 * Set the size of the kernel socket buffer. This call needs the
374 * appropriate privileges to succeed.
376 * Returns: 0 on success, otherwise -1 on error.
378 _public_ int udev_monitor_set_receive_buffer_size(struct udev_monitor *udev_monitor, int size)
380 if (udev_monitor == NULL)
382 return setsockopt(udev_monitor->sock, SOL_SOCKET, SO_RCVBUFFORCE, &size, sizeof(size));
385 int udev_monitor_disconnect(struct udev_monitor *udev_monitor)
389 err = close(udev_monitor->sock);
390 udev_monitor->sock = -1;
396 * @udev_monitor: udev monitor
398 * Take a reference of a udev monitor.
400 * Returns: the passed udev monitor
402 _public_ struct udev_monitor *udev_monitor_ref(struct udev_monitor *udev_monitor)
404 if (udev_monitor == NULL)
406 udev_monitor->refcount++;
411 * udev_monitor_unref:
412 * @udev_monitor: udev monitor
414 * Drop a reference of a udev monitor. If the refcount reaches zero,
415 * the bound socket will be closed, and the resources of the monitor
419 _public_ void udev_monitor_unref(struct udev_monitor *udev_monitor)
421 if (udev_monitor == NULL)
423 udev_monitor->refcount--;
424 if (udev_monitor->refcount > 0)
426 if (udev_monitor->sock >= 0)
427 close(udev_monitor->sock);
428 udev_list_cleanup(&udev_monitor->filter_subsystem_list);
429 udev_list_cleanup(&udev_monitor->filter_tag_list);
434 * udev_monitor_get_udev:
435 * @udev_monitor: udev monitor
437 * Retrieve the udev library context the monitor was created with.
439 * Returns: the udev library context
441 _public_ struct udev *udev_monitor_get_udev(struct udev_monitor *udev_monitor)
443 if (udev_monitor == NULL)
445 return udev_monitor->udev;
449 * udev_monitor_get_fd:
450 * @udev_monitor: udev monitor
452 * Retrieve the socket file descriptor associated with the monitor.
454 * Returns: the socket file descriptor
456 _public_ int udev_monitor_get_fd(struct udev_monitor *udev_monitor)
458 if (udev_monitor == NULL)
460 return udev_monitor->sock;
463 static int passes_filter(struct udev_monitor *udev_monitor, struct udev_device *udev_device)
465 struct udev_list_entry *list_entry;
467 if (udev_list_get_entry(&udev_monitor->filter_subsystem_list) == NULL)
469 udev_list_entry_foreach(list_entry, udev_list_get_entry(&udev_monitor->filter_subsystem_list)) {
470 const char *subsys = udev_list_entry_get_name(list_entry);
471 const char *dsubsys = udev_device_get_subsystem(udev_device);
473 const char *ddevtype;
475 if (strcmp(dsubsys, subsys) != 0)
478 devtype = udev_list_entry_get_value(list_entry);
481 ddevtype = udev_device_get_devtype(udev_device);
482 if (ddevtype == NULL)
484 if (strcmp(ddevtype, devtype) == 0)
490 if (udev_list_get_entry(&udev_monitor->filter_tag_list) == NULL)
492 udev_list_entry_foreach(list_entry, udev_list_get_entry(&udev_monitor->filter_tag_list)) {
493 const char *tag = udev_list_entry_get_name(list_entry);
495 if (udev_device_has_tag(udev_device, tag))
502 * udev_monitor_receive_device:
503 * @udev_monitor: udev monitor
505 * Receive data from the udev monitor socket, allocate a new udev
506 * device, fill in the received data, and return the device.
508 * Only socket connections with uid=0 are accepted.
510 * The initial refcount is 1, and needs to be decremented to
511 * release the resources of the udev device.
513 * Returns: a new udev device, or #NULL, in case of an error
515 _public_ struct udev_device *udev_monitor_receive_device(struct udev_monitor *udev_monitor)
517 struct udev_device *udev_device;
520 char cred_msg[CMSG_SPACE(sizeof(struct ucred))];
521 struct cmsghdr *cmsg;
522 union sockaddr_union snl;
527 struct udev_monitor_netlink_header *nlh;
530 if (udev_monitor == NULL)
533 iov.iov_len = sizeof(buf);
534 memset (&smsg, 0x00, sizeof(struct msghdr));
537 smsg.msg_control = cred_msg;
538 smsg.msg_controllen = sizeof(cred_msg);
540 if (udev_monitor->snl.nl.nl_family != 0) {
541 smsg.msg_name = &snl;
542 smsg.msg_namelen = sizeof(snl);
545 buflen = recvmsg(udev_monitor->sock, &smsg, 0);
548 dbg(udev_monitor->udev, "unable to receive message\n");
552 if (buflen < 32 || (size_t)buflen >= sizeof(buf)) {
553 dbg(udev_monitor->udev, "invalid message length\n");
557 if (udev_monitor->snl.nl.nl_family != 0) {
558 if (snl.nl.nl_groups == 0) {
559 /* unicast message, check if we trust the sender */
560 if (udev_monitor->snl_trusted_sender.nl.nl_pid == 0 ||
561 snl.nl.nl_pid != udev_monitor->snl_trusted_sender.nl.nl_pid) {
562 dbg(udev_monitor->udev, "unicast netlink message ignored\n");
565 } else if (snl.nl.nl_groups == UDEV_MONITOR_KERNEL) {
566 if (snl.nl.nl_pid > 0) {
567 dbg(udev_monitor->udev, "multicast kernel netlink message from pid %d ignored\n",
574 cmsg = CMSG_FIRSTHDR(&smsg);
575 if (cmsg == NULL || cmsg->cmsg_type != SCM_CREDENTIALS) {
576 dbg(udev_monitor->udev, "no sender credentials received, message ignored\n");
580 cred = (struct ucred *)CMSG_DATA(cmsg);
581 if (cred->uid != 0) {
582 dbg(udev_monitor->udev, "sender uid=%d, message ignored\n", cred->uid);
586 if (memcmp(buf, "libudev", 8) == 0) {
587 /* udev message needs proper version magic */
588 nlh = (struct udev_monitor_netlink_header *) buf;
589 if (nlh->magic != htonl(UDEV_MONITOR_MAGIC)) {
590 err(udev_monitor->udev, "unrecognized message signature (%x != %x)\n",
591 nlh->magic, htonl(UDEV_MONITOR_MAGIC));
594 if (nlh->properties_off+32 > buflen)
596 bufpos = nlh->properties_off;
598 /* kernel message with header */
599 bufpos = strlen(buf) + 1;
600 if ((size_t)bufpos < sizeof("a@/d") || bufpos >= buflen) {
601 dbg(udev_monitor->udev, "invalid message length\n");
605 /* check message header */
606 if (strstr(buf, "@/") == NULL) {
607 dbg(udev_monitor->udev, "unrecognized message header\n");
612 udev_device = udev_device_new(udev_monitor->udev);
613 if (udev_device == NULL)
615 udev_device_set_info_loaded(udev_device);
617 while (bufpos < buflen) {
622 keylen = strlen(key);
625 bufpos += keylen + 1;
626 udev_device_add_property_from_string_parse(udev_device, key);
629 if (udev_device_add_property_from_string_parse_finish(udev_device) < 0) {
630 dbg(udev_monitor->udev, "missing values, invalid device\n");
631 udev_device_unref(udev_device);
635 /* skip device, if it does not pass the current filter */
636 if (!passes_filter(udev_monitor, udev_device)) {
637 struct pollfd pfd[1];
640 udev_device_unref(udev_device);
642 /* if something is queued, get next device */
643 pfd[0].fd = udev_monitor->sock;
644 pfd[0].events = POLLIN;
645 rc = poll(pfd, 1, 0);
654 int udev_monitor_send_device(struct udev_monitor *udev_monitor,
655 struct udev_monitor *destination, struct udev_device *udev_device)
663 struct udev_monitor_netlink_header nlh;
664 struct udev_list_entry *list_entry;
665 uint64_t tag_bloom_bits;
667 if (udev_monitor->snl.nl.nl_family == 0)
670 blen = udev_device_get_properties_monitor_buf(udev_device, &buf);
674 /* add versioned header */
675 memset(&nlh, 0x00, sizeof(struct udev_monitor_netlink_header));
676 memcpy(nlh.prefix, "libudev", 8);
677 nlh.magic = htonl(UDEV_MONITOR_MAGIC);
678 nlh.header_size = sizeof(struct udev_monitor_netlink_header);
679 val = udev_device_get_subsystem(udev_device);
680 nlh.filter_subsystem_hash = htonl(util_string_hash32(val));
681 val = udev_device_get_devtype(udev_device);
683 nlh.filter_devtype_hash = htonl(util_string_hash32(val));
684 iov[0].iov_base = &nlh;
685 iov[0].iov_len = sizeof(struct udev_monitor_netlink_header);
687 /* add tag bloom filter */
689 udev_list_entry_foreach(list_entry, udev_device_get_tags_list_entry(udev_device))
690 tag_bloom_bits |= util_string_bloom64(udev_list_entry_get_name(list_entry));
691 if (tag_bloom_bits > 0) {
692 nlh.filter_tag_bloom_hi = htonl(tag_bloom_bits >> 32);
693 nlh.filter_tag_bloom_lo = htonl(tag_bloom_bits & 0xffffffff);
696 /* add properties list */
697 nlh.properties_off = iov[0].iov_len;
698 nlh.properties_len = blen;
699 iov[1].iov_base = (char *)buf;
700 iov[1].iov_len = blen;
702 memset(&smsg, 0x00, sizeof(struct msghdr));
706 * Use custom address for target, or the default one.
708 * If we send to a multicast group, we will get
709 * ECONNREFUSED, which is expected.
711 if (destination != NULL)
712 smsg.msg_name = &destination->snl;
714 smsg.msg_name = &udev_monitor->snl_destination;
715 smsg.msg_namelen = sizeof(struct sockaddr_nl);
716 count = sendmsg(udev_monitor->sock, &smsg, 0);
717 dbg(udev_monitor->udev, "passed %zi bytes to netlink monitor %p\n", count, udev_monitor);
722 * udev_monitor_filter_add_match_subsystem_devtype:
723 * @udev_monitor: the monitor
724 * @subsystem: the subsystem value to match the incoming devices against
725 * @devtype: the devtype value to match the incoming devices against
727 * This filter is efficiently executed inside the kernel, and libudev subscribers
728 * will usually not be woken up for devices which do not match.
730 * The filter must be installed before the monitor is switched to listening mode.
732 * Returns: 0 on success, otherwise a negative error value.
734 _public_ int udev_monitor_filter_add_match_subsystem_devtype(struct udev_monitor *udev_monitor, const char *subsystem, const char *devtype)
736 if (udev_monitor == NULL)
738 if (subsystem == NULL)
740 if (udev_list_entry_add(&udev_monitor->filter_subsystem_list, subsystem, devtype) == NULL)
746 * udev_monitor_filter_add_match_tag:
747 * @udev_monitor: the monitor
748 * @tag: the name of a tag
750 * This filter is efficiently executed inside the kernel, and libudev subscribers
751 * will usually not be woken up for devices which do not match.
753 * The filter must be installed before the monitor is switched to listening mode.
755 * Returns: 0 on success, otherwise a negative error value.
757 _public_ int udev_monitor_filter_add_match_tag(struct udev_monitor *udev_monitor, const char *tag)
759 if (udev_monitor == NULL)
763 if (udev_list_entry_add(&udev_monitor->filter_tag_list, tag, NULL) == NULL)
769 * udev_monitor_filter_remove:
770 * @udev_monitor: monitor
772 * Remove all filters from monitor.
774 * Returns: 0 on success, otherwise a negative error value.
776 _public_ int udev_monitor_filter_remove(struct udev_monitor *udev_monitor)
778 static struct sock_fprog filter = { 0, NULL };
780 udev_list_cleanup(&udev_monitor->filter_subsystem_list);
781 return setsockopt(udev_monitor->sock, SOL_SOCKET, SO_ATTACH_FILTER, &filter, sizeof(filter));