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"
31 * SECTION:libudev-monitor
32 * @short_description: device event source
34 * Connects to a device event source.
40 * Opaque object handling one event source.
46 struct sockaddr_nl snl;
47 struct sockaddr_nl snl_trusted_sender;
48 struct sockaddr_nl snl_destination;
49 struct sockaddr_un sun;
51 struct udev_list_node filter_subsystem_list;
52 struct udev_list_node filter_tag_list;
55 enum udev_monitor_netlink_group {
61 #define UDEV_MONITOR_MAGIC 0xfeedcafe
62 struct udev_monitor_netlink_header {
63 /* "libudev" prefix to distinguish libudev and kernel messages */
66 * magic to protect against daemon <-> library message format mismatch
67 * used in the kernel from socket filter rules; needs to be stored in network order
70 /* total length of header structure known to the sender */
71 unsigned int header_size;
72 /* properties string buffer */
73 unsigned int properties_off;
74 unsigned int properties_len;
76 * hashes of primary device properties strings, to let libudev subscribers
77 * use in-kernel socket filters; values need to be stored in network order
79 unsigned int filter_subsystem_hash;
80 unsigned int filter_devtype_hash;
81 unsigned int filter_tag_bloom_hi;
82 unsigned int filter_tag_bloom_lo;
85 static struct udev_monitor *udev_monitor_new(struct udev *udev)
87 struct udev_monitor *udev_monitor;
89 udev_monitor = calloc(1, sizeof(struct udev_monitor));
90 if (udev_monitor == NULL)
92 udev_monitor->refcount = 1;
93 udev_monitor->udev = udev;
94 udev_list_init(&udev_monitor->filter_subsystem_list);
95 udev_list_init(&udev_monitor->filter_tag_list);
100 * udev_monitor_new_from_socket:
101 * @udev: udev library context
102 * @socket_path: unix socket path
104 * Create new udev monitor and connect to a specified socket. The
105 * path to a socket either points to an existing socket file, or if
106 * the socket path starts with a '@' character, an abstract namespace
107 * socket will be used.
109 * A socket file will not be created. If it does not already exist,
110 * it will fall-back and connect to an abstract namespace socket with
111 * the given path. The permissions adjustment of a socket file, as
112 * well as the later cleanup, needs to be done by the caller.
114 * The initial refcount is 1, and needs to be decremented to
115 * release the resources of the udev monitor.
117 * Returns: a new udev monitor, or #NULL, in case of an error
119 struct udev_monitor *udev_monitor_new_from_socket(struct udev *udev, const char *socket_path)
121 struct udev_monitor *udev_monitor;
126 if (socket_path == NULL)
128 udev_monitor = udev_monitor_new(udev);
129 if (udev_monitor == NULL)
132 udev_monitor->sun.sun_family = AF_LOCAL;
133 if (socket_path[0] == '@') {
134 /* translate leading '@' to abstract namespace */
135 util_strscpy(udev_monitor->sun.sun_path, sizeof(udev_monitor->sun.sun_path), socket_path);
136 udev_monitor->sun.sun_path[0] = '\0';
137 udev_monitor->addrlen = offsetof(struct sockaddr_un, sun_path) + strlen(socket_path);
138 } else if (stat(socket_path, &statbuf) == 0 && S_ISSOCK(statbuf.st_mode)) {
139 /* existing socket file */
140 util_strscpy(udev_monitor->sun.sun_path, sizeof(udev_monitor->sun.sun_path), socket_path);
141 udev_monitor->addrlen = offsetof(struct sockaddr_un, sun_path) + strlen(socket_path);
143 /* no socket file, assume abstract namespace socket */
144 util_strscpy(&udev_monitor->sun.sun_path[1], sizeof(udev_monitor->sun.sun_path)-1, socket_path);
145 udev_monitor->addrlen = offsetof(struct sockaddr_un, sun_path) + strlen(socket_path)+1;
147 udev_monitor->sock = socket(AF_LOCAL, SOCK_DGRAM|SOCK_CLOEXEC, 0);
148 if (udev_monitor->sock == -1) {
149 err(udev, "error getting socket: %m\n");
154 dbg(udev, "monitor %p created with '%s'\n", udev_monitor, socket_path);
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
171 * Accessing devices at the same time as udev, might result
172 * in unpredictable behavior.
174 * The "udev" events are sent out after udev has finished its
175 * event processing, all rules have been processed, and needed
176 * device nodes are created.
178 * The initial refcount is 1, and needs to be decremented to
179 * release the resources of the udev monitor.
181 * Returns: a new udev monitor, or #NULL, in case of an error
183 struct udev_monitor *udev_monitor_new_from_netlink(struct udev *udev, const char *name)
185 struct udev_monitor *udev_monitor;
192 group = UDEV_MONITOR_NONE;
193 else if (strcmp(name, "udev") == 0)
194 group = UDEV_MONITOR_UDEV;
195 else if (strcmp(name, "kernel") == 0)
196 group = UDEV_MONITOR_KERNEL;
200 udev_monitor = udev_monitor_new(udev);
201 if (udev_monitor == NULL)
204 udev_monitor->sock = socket(PF_NETLINK, SOCK_DGRAM|SOCK_CLOEXEC, NETLINK_KOBJECT_UEVENT);
205 if (udev_monitor->sock == -1) {
206 err(udev, "error getting socket: %m\n");
211 udev_monitor->snl.nl_family = AF_NETLINK;
212 udev_monitor->snl.nl_groups = group;
214 /* default destination for sending */
215 udev_monitor->snl_destination.nl_family = AF_NETLINK;
216 udev_monitor->snl_destination.nl_groups = UDEV_MONITOR_UDEV;
218 dbg(udev, "monitor %p created with NETLINK_KOBJECT_UEVENT (%u)\n", udev_monitor, group);
222 static inline void bpf_stmt(struct sock_filter *inss, unsigned int *i,
223 unsigned short code, unsigned int data)
225 struct sock_filter *ins = &inss[*i];
232 static inline void bpf_jmp(struct sock_filter *inss, unsigned int *i,
233 unsigned short code, unsigned int data,
234 unsigned short jt, unsigned short jf)
236 struct sock_filter *ins = &inss[*i];
246 * udev_monitor_filter_update:
247 * @udev_monitor: monitor
249 * Update the installed filter. This might only be needed, if the filter was removed or changed.
251 * Returns: 0 on success, otherwise a negative error value.
253 int udev_monitor_filter_update(struct udev_monitor *udev_monitor)
255 struct sock_filter ins[512];
256 struct sock_fprog filter;
258 struct udev_list_entry *list_entry;
261 if (udev_list_get_entry(&udev_monitor->filter_subsystem_list) == NULL &&
262 udev_list_get_entry(&udev_monitor->filter_tag_list) == NULL)
265 memset(ins, 0x00, sizeof(ins));
268 /* load magic in A */
269 bpf_stmt(ins, &i, BPF_LD|BPF_W|BPF_ABS, offsetof(struct udev_monitor_netlink_header, magic));
270 /* jump if magic matches */
271 bpf_jmp(ins, &i, BPF_JMP|BPF_JEQ|BPF_K, UDEV_MONITOR_MAGIC, 1, 0);
272 /* wrong magic, pass packet */
273 bpf_stmt(ins, &i, BPF_RET|BPF_K, 0xffffffff);
275 if (udev_list_get_entry(&udev_monitor->filter_tag_list) != NULL) {
278 /* count tag matches, to calculate end of tag match block */
280 udev_list_entry_foreach(list_entry, udev_list_get_entry(&udev_monitor->filter_tag_list))
283 /* add all tags matches */
284 udev_list_entry_foreach(list_entry, udev_list_get_entry(&udev_monitor->filter_tag_list)) {
285 uint64_t tag_bloom_bits = util_string_bloom64(udev_list_entry_get_name(list_entry));
286 uint32_t tag_bloom_hi = tag_bloom_bits >> 32;
287 uint32_t tag_bloom_lo = tag_bloom_bits & 0xffffffff;
289 /* load device bloom bits in A */
290 bpf_stmt(ins, &i, BPF_LD|BPF_W|BPF_ABS, offsetof(struct udev_monitor_netlink_header, filter_tag_bloom_hi));
291 /* clear bits (tag bits & bloom bits) */
292 bpf_stmt(ins, &i, BPF_ALU|BPF_AND|BPF_K, tag_bloom_hi);
293 /* jump to next tag if it does not match */
294 bpf_jmp(ins, &i, BPF_JMP|BPF_JEQ|BPF_K, tag_bloom_hi, 0, 3);
296 /* load device bloom bits in A */
297 bpf_stmt(ins, &i, BPF_LD|BPF_W|BPF_ABS, offsetof(struct udev_monitor_netlink_header, filter_tag_bloom_lo));
298 /* clear bits (tag bits & bloom bits) */
299 bpf_stmt(ins, &i, BPF_ALU|BPF_AND|BPF_K, tag_bloom_lo);
300 /* jump behind end of tag match block if tag matches */
302 bpf_jmp(ins, &i, BPF_JMP|BPF_JEQ|BPF_K, tag_bloom_lo, 1 + (tag_matches * 6), 0);
305 /* nothing matched, drop packet */
306 bpf_stmt(ins, &i, BPF_RET|BPF_K, 0);
309 /* add all subsystem matches */
310 if (udev_list_get_entry(&udev_monitor->filter_subsystem_list) != NULL) {
311 udev_list_entry_foreach(list_entry, udev_list_get_entry(&udev_monitor->filter_subsystem_list)) {
312 unsigned int hash = util_string_hash32(udev_list_entry_get_name(list_entry));
314 /* load device subsystem value in A */
315 bpf_stmt(ins, &i, BPF_LD|BPF_W|BPF_ABS, offsetof(struct udev_monitor_netlink_header, filter_subsystem_hash));
316 if (udev_list_entry_get_value(list_entry) == NULL) {
317 /* jump if subsystem does not match */
318 bpf_jmp(ins, &i, BPF_JMP|BPF_JEQ|BPF_K, hash, 0, 1);
320 /* jump if subsystem does not match */
321 bpf_jmp(ins, &i, BPF_JMP|BPF_JEQ|BPF_K, hash, 0, 3);
323 /* load device devtype value in A */
324 bpf_stmt(ins, &i, BPF_LD|BPF_W|BPF_ABS, offsetof(struct udev_monitor_netlink_header, filter_devtype_hash));
325 /* jump if value does not match */
326 hash = util_string_hash32(udev_list_entry_get_value(list_entry));
327 bpf_jmp(ins, &i, BPF_JMP|BPF_JEQ|BPF_K, hash, 0, 1);
330 /* matched, pass packet */
331 bpf_stmt(ins, &i, BPF_RET|BPF_K, 0xffffffff);
333 if (i+1 >= ARRAY_SIZE(ins))
337 /* nothing matched, drop packet */
338 bpf_stmt(ins, &i, BPF_RET|BPF_K, 0);
341 /* matched, pass packet */
342 bpf_stmt(ins, &i, BPF_RET|BPF_K, 0xffffffff);
347 err = setsockopt(udev_monitor->sock, SOL_SOCKET, SO_ATTACH_FILTER, &filter, sizeof(filter));
351 int udev_monitor_allow_unicast_sender(struct udev_monitor *udev_monitor, struct udev_monitor *sender)
353 udev_monitor->snl_trusted_sender.nl_pid = sender->snl.nl_pid;
357 * udev_monitor_enable_receiving:
358 * @udev_monitor: the monitor which should receive events
360 * Binds the @udev_monitor socket to the event source.
362 * Returns: 0 on success, otherwise a negative error value.
364 int udev_monitor_enable_receiving(struct udev_monitor *udev_monitor)
369 if (udev_monitor->sun.sun_family != 0) {
370 err = bind(udev_monitor->sock,
371 (struct sockaddr *)&udev_monitor->sun, udev_monitor->addrlen);
372 } else if (udev_monitor->snl.nl_family != 0) {
373 udev_monitor_filter_update(udev_monitor);
374 err = bind(udev_monitor->sock,
375 (struct sockaddr *)&udev_monitor->snl, sizeof(struct sockaddr_nl));
377 struct sockaddr_nl snl;
381 * get the address the kernel has assigned us
382 * it is usually, but not necessarily the pid
384 addrlen = sizeof(struct sockaddr_nl);
385 err = getsockname(udev_monitor->sock, (struct sockaddr *)&snl, &addrlen);
387 udev_monitor->snl.nl_pid = snl.nl_pid;
394 err(udev_monitor->udev, "bind failed: %m\n");
398 /* enable receiving of sender credentials */
399 setsockopt(udev_monitor->sock, SOL_SOCKET, SO_PASSCRED, &on, sizeof(on));
403 int udev_monitor_set_receive_buffer_size(struct udev_monitor *udev_monitor, int size)
405 if (udev_monitor == NULL)
407 return setsockopt(udev_monitor->sock, SOL_SOCKET, SO_RCVBUFFORCE, &size, sizeof(size));
410 int udev_monitor_disconnect(struct udev_monitor *udev_monitor)
414 err = close(udev_monitor->sock);
415 udev_monitor->sock = -1;
421 * @udev_monitor: udev monitor
423 * Take a reference of a udev monitor.
425 * Returns: the passed udev monitor
427 struct udev_monitor *udev_monitor_ref(struct udev_monitor *udev_monitor)
429 if (udev_monitor == NULL)
431 udev_monitor->refcount++;
436 * udev_monitor_unref:
437 * @udev_monitor: udev monitor
439 * Drop a reference of a udev monitor. If the refcount reaches zero,
440 * the bound socket will be closed, and the resources of the monitor
444 void udev_monitor_unref(struct udev_monitor *udev_monitor)
446 if (udev_monitor == NULL)
448 udev_monitor->refcount--;
449 if (udev_monitor->refcount > 0)
451 if (udev_monitor->sock >= 0)
452 close(udev_monitor->sock);
453 udev_list_cleanup_entries(udev_monitor->udev, &udev_monitor->filter_subsystem_list);
454 udev_list_cleanup_entries(udev_monitor->udev, &udev_monitor->filter_tag_list);
455 dbg(udev_monitor->udev, "monitor %p released\n", udev_monitor);
460 * udev_monitor_get_udev:
461 * @udev_monitor: udev monitor
463 * Retrieve the udev library context the monitor was created with.
465 * Returns: the udev library context
467 struct udev *udev_monitor_get_udev(struct udev_monitor *udev_monitor)
469 if (udev_monitor == NULL)
471 return udev_monitor->udev;
475 * udev_monitor_get_fd:
476 * @udev_monitor: udev monitor
478 * Retrieve the socket file descriptor associated with the monitor.
480 * Returns: the socket file descriptor
482 int udev_monitor_get_fd(struct udev_monitor *udev_monitor)
484 if (udev_monitor == NULL)
486 return udev_monitor->sock;
489 static int passes_filter(struct udev_monitor *udev_monitor, struct udev_device *udev_device)
491 struct udev_list_entry *list_entry;
493 if (udev_list_get_entry(&udev_monitor->filter_subsystem_list) == NULL)
495 udev_list_entry_foreach(list_entry, udev_list_get_entry(&udev_monitor->filter_subsystem_list)) {
496 const char *subsys = udev_list_entry_get_name(list_entry);
497 const char *dsubsys = udev_device_get_subsystem(udev_device);
499 const char *ddevtype;
501 if (strcmp(dsubsys, subsys) != 0)
504 devtype = udev_list_entry_get_value(list_entry);
507 ddevtype = udev_device_get_devtype(udev_device);
508 if (ddevtype == NULL)
510 if (strcmp(ddevtype, devtype) == 0)
516 if (udev_list_get_entry(&udev_monitor->filter_tag_list) == NULL)
518 udev_list_entry_foreach(list_entry, udev_list_get_entry(&udev_monitor->filter_tag_list)) {
519 const char *tag = udev_list_entry_get_name(list_entry);
521 if (udev_device_has_tag(udev_device, tag))
528 * udev_monitor_receive_device:
529 * @udev_monitor: udev monitor
531 * Receive data from the udev monitor socket, allocate a new udev
532 * device, fill in the received data, and return the device.
534 * Only socket connections with uid=0 are accepted. The caller
535 * needs to make sure that there is data to read from the socket.
536 * The call will block until the socket becomes readable.
538 * The initial refcount is 1, and needs to be decremented to
539 * release the resources of the udev device.
541 * Returns: a new udev device, or #NULL, in case of an error
543 struct udev_device *udev_monitor_receive_device(struct udev_monitor *udev_monitor)
545 struct udev_device *udev_device;
548 char cred_msg[CMSG_SPACE(sizeof(struct ucred))];
549 struct cmsghdr *cmsg;
550 struct sockaddr_nl snl;
555 struct udev_monitor_netlink_header *nlh;
558 if (udev_monitor == NULL)
560 memset(buf, 0x00, sizeof(buf));
562 iov.iov_len = sizeof(buf);
563 memset (&smsg, 0x00, sizeof(struct msghdr));
566 smsg.msg_control = cred_msg;
567 smsg.msg_controllen = sizeof(cred_msg);
569 if (udev_monitor->snl.nl_family != 0) {
570 smsg.msg_name = &snl;
571 smsg.msg_namelen = sizeof(snl);
574 buflen = recvmsg(udev_monitor->sock, &smsg, 0);
577 info(udev_monitor->udev, "unable to receive message\n");
581 if (buflen < 32 || (size_t)buflen >= sizeof(buf)) {
582 info(udev_monitor->udev, "invalid message length\n");
586 if (udev_monitor->snl.nl_family != 0) {
587 if (snl.nl_groups == 0) {
588 /* unicast message, check if we trust the sender */
589 if (udev_monitor->snl_trusted_sender.nl_pid == 0 ||
590 snl.nl_pid != udev_monitor->snl_trusted_sender.nl_pid) {
591 info(udev_monitor->udev, "unicast netlink message ignored\n");
594 } else if (snl.nl_groups == UDEV_MONITOR_KERNEL) {
595 if (snl.nl_pid > 0) {
596 info(udev_monitor->udev, "multicast kernel netlink message from pid %d ignored\n",
603 cmsg = CMSG_FIRSTHDR(&smsg);
604 if (cmsg == NULL || cmsg->cmsg_type != SCM_CREDENTIALS) {
605 info(udev_monitor->udev, "no sender credentials received, message ignored\n");
609 cred = (struct ucred *)CMSG_DATA(cmsg);
610 if (cred->uid != 0) {
611 info(udev_monitor->udev, "sender uid=%d, message ignored\n", cred->uid);
615 if (memcmp(buf, "libudev", 8) == 0) {
616 /* udev message needs proper version magic */
617 nlh = (struct udev_monitor_netlink_header *) buf;
618 if (nlh->magic != htonl(UDEV_MONITOR_MAGIC))
620 if (nlh->properties_off+32 > buflen)
622 bufpos = nlh->properties_off;
624 /* kernel message with header */
625 bufpos = strlen(buf) + 1;
626 if ((size_t)bufpos < sizeof("a@/d") || bufpos >= buflen) {
627 info(udev_monitor->udev, "invalid message length\n");
631 /* check message header */
632 if (strstr(buf, "@/") == NULL) {
633 info(udev_monitor->udev, "unrecognized message header\n");
638 udev_device = udev_device_new(udev_monitor->udev);
639 if (udev_device == NULL)
641 udev_device_set_info_loaded(udev_device);
643 while (bufpos < buflen) {
648 keylen = strlen(key);
651 bufpos += keylen + 1;
652 udev_device_add_property_from_string_parse(udev_device, key);
655 if (udev_device_add_property_from_string_parse_finish(udev_device) < 0) {
656 info(udev_monitor->udev, "missing values, invalid device\n");
657 udev_device_unref(udev_device);
661 /* skip device, if it does not pass the current filter */
662 if (!passes_filter(udev_monitor, udev_device)) {
663 struct pollfd pfd[1];
666 udev_device_unref(udev_device);
668 /* if something is queued, get next device */
669 pfd[0].fd = udev_monitor->sock;
670 pfd[0].events = POLLIN;
671 rc = poll(pfd, 1, 0);
680 int udev_monitor_send_device(struct udev_monitor *udev_monitor,
681 struct udev_monitor *destination, struct udev_device *udev_device)
687 blen = udev_device_get_properties_monitor_buf(udev_device, &buf);
691 if (udev_monitor->sun.sun_family != 0) {
698 /* header <action>@<devpath> */
699 action = udev_device_get_action(udev_device);
703 if (util_strpcpyl(&s, sizeof(header), action, "@", udev_device_get_devpath(udev_device), NULL) == 0)
705 iov[0].iov_base = header;
706 iov[0].iov_len = (s - header)+1;
708 /* add properties list */
709 iov[1].iov_base = (char *)buf;
710 iov[1].iov_len = blen;
712 memset(&smsg, 0x00, sizeof(struct msghdr));
715 smsg.msg_name = &udev_monitor->sun;
716 smsg.msg_namelen = udev_monitor->addrlen;
717 count = sendmsg(udev_monitor->sock, &smsg, 0);
718 info(udev_monitor->udev, "passed %zi bytes to socket monitor %p\n", count, udev_monitor);
722 if (udev_monitor->snl.nl_family != 0) {
726 struct udev_monitor_netlink_header nlh;
727 struct udev_list_entry *list_entry;
728 uint64_t tag_bloom_bits;
730 /* add versioned header */
731 memset(&nlh, 0x00, sizeof(struct udev_monitor_netlink_header));
732 memcpy(nlh.prefix, "libudev", 8);
733 nlh.magic = htonl(UDEV_MONITOR_MAGIC);
734 nlh.header_size = sizeof(struct udev_monitor_netlink_header);
735 val = udev_device_get_subsystem(udev_device);
736 nlh.filter_subsystem_hash = htonl(util_string_hash32(val));
737 val = udev_device_get_devtype(udev_device);
739 nlh.filter_devtype_hash = htonl(util_string_hash32(val));
740 iov[0].iov_base = &nlh;
741 iov[0].iov_len = sizeof(struct udev_monitor_netlink_header);
743 /* add tag bloom filter */
745 udev_list_entry_foreach(list_entry, udev_device_get_tags_list_entry(udev_device))
746 tag_bloom_bits |= util_string_bloom64(udev_list_entry_get_name(list_entry));
747 if (tag_bloom_bits > 0) {
748 nlh.filter_tag_bloom_hi = htonl(tag_bloom_bits >> 32);
749 nlh.filter_tag_bloom_lo = htonl(tag_bloom_bits & 0xffffffff);
752 /* add properties list */
753 nlh.properties_off = iov[0].iov_len;
754 nlh.properties_len = blen;
755 iov[1].iov_base = (char *)buf;
756 iov[1].iov_len = blen;
758 memset(&smsg, 0x00, sizeof(struct msghdr));
762 * Use custom address for target, or the default one.
764 * If we send to a multicast group, we will get
765 * ECONNREFUSED, which is expected.
767 if (destination != NULL)
768 smsg.msg_name = &destination->snl;
770 smsg.msg_name = &udev_monitor->snl_destination;
771 smsg.msg_namelen = sizeof(struct sockaddr_nl);
772 count = sendmsg(udev_monitor->sock, &smsg, 0);
773 info(udev_monitor->udev, "passed %zi bytes to netlink monitor %p\n", count, udev_monitor);
781 * udev_monitor_filter_add_match_subsystem_devtype:
782 * @udev_monitor: the monitor
783 * @subsystem: the subsystem value to match the incoming devices against
784 * @devtype: the devtype value to match the incoming devices against
786 * This filer is efficiently executed inside the kernel, and libudev subscribers
787 * will usually not be woken up for devices which do not match.
789 * The filter must be installed before the monitor is switched to listening mode.
791 * Returns: 0 on success, otherwise a negative error value.
793 int udev_monitor_filter_add_match_subsystem_devtype(struct udev_monitor *udev_monitor, const char *subsystem, const char *devtype)
795 if (udev_monitor == NULL)
797 if (subsystem == NULL)
799 if (udev_list_entry_add(udev_monitor->udev,
800 &udev_monitor->filter_subsystem_list, subsystem, devtype, 0, 0) == NULL)
806 * udev_monitor_filter_add_match_tag:
807 * @udev_monitor: the monitor
808 * @tag: the name of a tag
810 * This filer is efficiently executed inside the kernel, and libudev subscribers
811 * will usually not be woken up for devices which do not match.
813 * The filter must be installed before the monitor is switched to listening mode.
815 * Returns: 0 on success, otherwise a negative error value.
817 int udev_monitor_filter_add_match_tag(struct udev_monitor *udev_monitor, const char *tag)
819 if (udev_monitor == NULL)
823 if (udev_list_entry_add(udev_monitor->udev,
824 &udev_monitor->filter_tag_list, tag, NULL, 0, 0) == NULL)
830 * udev_monitor_filter_remove:
831 * @udev_monitor: monitor
833 * Remove all filters from monitor.
835 * Returns: 0 on success, otherwise a negative error value.
837 int udev_monitor_filter_remove(struct udev_monitor *udev_monitor)
839 static struct sock_fprog filter = { 0, NULL };
841 udev_list_cleanup_entries(udev_monitor->udev, &udev_monitor->filter_subsystem_list);
842 return setsockopt(udev_monitor->sock, SOL_SOCKET, SO_ATTACH_FILTER, &filter, sizeof(filter));