2 This file is part of systemd.
4 Copyright 2008-2012 Kay Sievers <kay@vrfy.org>
6 systemd is free software; you can redistribute it and/or modify it
7 under the terms of the GNU Lesser General Public License as published by
8 the Free Software Foundation; either version 2.1 of the License, or
9 (at your option) any later version.
11 systemd is distributed in the hope that it will be useful, but
12 WITHOUT ANY WARRANTY; without even the implied warranty of
13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
14 Lesser General Public License for more details.
16 You should have received a copy of the GNU Lesser General Public License
17 along with systemd; If not, see <http://www.gnu.org/licenses/>.
29 #include <sys/socket.h>
31 #include <arpa/inet.h>
32 #include <linux/netlink.h>
33 #include <linux/filter.h>
36 #include "libudev-private.h"
37 #include "socket-util.h"
41 * SECTION:libudev-monitor
42 * @short_description: device event source
44 * Connects to a device event source.
50 * Opaque object handling an event source.
56 union sockaddr_union snl
;
57 union sockaddr_union snl_trusted_sender
;
58 union sockaddr_union snl_destination
;
60 struct udev_list filter_subsystem_list
;
61 struct udev_list filter_tag_list
;
65 enum udev_monitor_netlink_group
{
71 #define UDEV_MONITOR_MAGIC 0xfeedcafe
72 struct udev_monitor_netlink_header
{
73 /* "libudev" prefix to distinguish libudev and kernel messages */
76 * magic to protect against daemon <-> library message format mismatch
77 * used in the kernel from socket filter rules; needs to be stored in network order
80 /* total length of header structure known to the sender */
81 unsigned int header_size
;
82 /* properties string buffer */
83 unsigned int properties_off
;
84 unsigned int properties_len
;
86 * hashes of primary device properties strings, to let libudev subscribers
87 * use in-kernel socket filters; values need to be stored in network order
89 unsigned int filter_subsystem_hash
;
90 unsigned int filter_devtype_hash
;
91 unsigned int filter_tag_bloom_hi
;
92 unsigned int filter_tag_bloom_lo
;
95 static struct udev_monitor
*udev_monitor_new(struct udev
*udev
)
97 struct udev_monitor
*udev_monitor
;
99 udev_monitor
= new0(struct udev_monitor
, 1);
100 if (udev_monitor
== NULL
)
102 udev_monitor
->refcount
= 1;
103 udev_monitor
->udev
= udev
;
104 udev_list_init(udev
, &udev_monitor
->filter_subsystem_list
, false);
105 udev_list_init(udev
, &udev_monitor
->filter_tag_list
, true);
109 /* we consider udev running when /dev is on devtmpfs */
110 static bool udev_has_devtmpfs(struct udev
*udev
) {
112 union file_handle_union h
= FILE_HANDLE_INIT
;
113 _cleanup_fclose_
FILE *f
= NULL
;
114 char line
[LINE_MAX
], *e
;
118 r
= name_to_handle_at(AT_FDCWD
, "/dev", &h
.handle
, &mount_id
, 0);
120 if (errno
!= EOPNOTSUPP
)
121 log_debug_errno(errno
, "name_to_handle_at on /dev: %m");
125 f
= fopen("/proc/self/mountinfo", "re");
129 FOREACH_LINE(line
, f
, return false) {
132 if (sscanf(line
, "%i", &mid
) != 1)
138 e
= strstr(line
, " - ");
142 /* accept any name that starts with the currently expected type */
143 if (startswith(e
+ 3, "devtmpfs"))
150 struct udev_monitor
*udev_monitor_new_from_netlink_fd(struct udev
*udev
, const char *name
, int fd
)
152 struct udev_monitor
*udev_monitor
;
159 group
= UDEV_MONITOR_NONE
;
160 else if (streq(name
, "udev")) {
162 * We do not support subscribing to uevents if no instance of
163 * udev is running. Uevents would otherwise broadcast the
164 * processing data of the host into containers, which is not
167 * Containers will currently not get any udev uevents, until
168 * a supporting infrastructure is available.
170 * We do not set a netlink multicast group here, so the socket
171 * will not receive any messages.
173 if (access("/run/udev/control", F_OK
) < 0 && !udev_has_devtmpfs(udev
)) {
174 log_debug("the udev service seems not to be active, disable the monitor");
175 group
= UDEV_MONITOR_NONE
;
177 group
= UDEV_MONITOR_UDEV
;
178 } else if (streq(name
, "kernel"))
179 group
= UDEV_MONITOR_KERNEL
;
183 udev_monitor
= udev_monitor_new(udev
);
184 if (udev_monitor
== NULL
)
188 udev_monitor
->sock
= socket(PF_NETLINK
, SOCK_RAW
|SOCK_CLOEXEC
|SOCK_NONBLOCK
, NETLINK_KOBJECT_UEVENT
);
189 if (udev_monitor
->sock
== -1) {
190 log_debug_errno(errno
, "error getting socket: %m");
195 udev_monitor
->bound
= true;
196 udev_monitor
->sock
= fd
;
199 udev_monitor
->snl
.nl
.nl_family
= AF_NETLINK
;
200 udev_monitor
->snl
.nl
.nl_groups
= group
;
202 /* default destination for sending */
203 udev_monitor
->snl_destination
.nl
.nl_family
= AF_NETLINK
;
204 udev_monitor
->snl_destination
.nl
.nl_groups
= UDEV_MONITOR_UDEV
;
210 * udev_monitor_new_from_netlink:
211 * @udev: udev library context
212 * @name: name of event source
214 * Create new udev monitor and connect to a specified event
215 * source. Valid sources identifiers are "udev" and "kernel".
217 * Applications should usually not connect directly to the
218 * "kernel" events, because the devices might not be useable
219 * at that time, before udev has configured them, and created
220 * device nodes. Accessing devices at the same time as udev,
221 * might result in unpredictable behavior. The "udev" events
222 * are sent out after udev has finished its event processing,
223 * all rules have been processed, and needed device nodes are
226 * The initial refcount is 1, and needs to be decremented to
227 * release the resources of the udev monitor.
229 * Returns: a new udev monitor, or #NULL, in case of an error
231 _public_
struct udev_monitor
*udev_monitor_new_from_netlink(struct udev
*udev
, const char *name
)
233 return udev_monitor_new_from_netlink_fd(udev
, name
, -1);
236 static inline void bpf_stmt(struct sock_filter
*inss
, unsigned int *i
,
237 unsigned short code
, unsigned int data
)
239 struct sock_filter
*ins
= &inss
[*i
];
246 static inline void bpf_jmp(struct sock_filter
*inss
, unsigned int *i
,
247 unsigned short code
, unsigned int data
,
248 unsigned short jt
, unsigned short jf
)
250 struct sock_filter
*ins
= &inss
[*i
];
260 * udev_monitor_filter_update:
261 * @udev_monitor: monitor
263 * Update the installed socket filter. This is only needed,
264 * if the filter was removed or changed.
266 * Returns: 0 on success, otherwise a negative error value.
268 _public_
int udev_monitor_filter_update(struct udev_monitor
*udev_monitor
)
270 struct sock_filter ins
[512];
271 struct sock_fprog filter
;
273 struct udev_list_entry
*list_entry
;
276 if (udev_list_get_entry(&udev_monitor
->filter_subsystem_list
) == NULL
&&
277 udev_list_get_entry(&udev_monitor
->filter_tag_list
) == NULL
)
280 memzero(ins
, sizeof(ins
));
283 /* load magic in A */
284 bpf_stmt(ins
, &i
, BPF_LD
|BPF_W
|BPF_ABS
, offsetof(struct udev_monitor_netlink_header
, magic
));
285 /* jump if magic matches */
286 bpf_jmp(ins
, &i
, BPF_JMP
|BPF_JEQ
|BPF_K
, UDEV_MONITOR_MAGIC
, 1, 0);
287 /* wrong magic, pass packet */
288 bpf_stmt(ins
, &i
, BPF_RET
|BPF_K
, 0xffffffff);
290 if (udev_list_get_entry(&udev_monitor
->filter_tag_list
) != NULL
) {
293 /* count tag matches, to calculate end of tag match block */
295 udev_list_entry_foreach(list_entry
, udev_list_get_entry(&udev_monitor
->filter_tag_list
))
298 /* add all tags matches */
299 udev_list_entry_foreach(list_entry
, udev_list_get_entry(&udev_monitor
->filter_tag_list
)) {
300 uint64_t tag_bloom_bits
= util_string_bloom64(udev_list_entry_get_name(list_entry
));
301 uint32_t tag_bloom_hi
= tag_bloom_bits
>> 32;
302 uint32_t tag_bloom_lo
= tag_bloom_bits
& 0xffffffff;
304 /* load device bloom bits in A */
305 bpf_stmt(ins
, &i
, BPF_LD
|BPF_W
|BPF_ABS
, offsetof(struct udev_monitor_netlink_header
, filter_tag_bloom_hi
));
306 /* clear bits (tag bits & bloom bits) */
307 bpf_stmt(ins
, &i
, BPF_ALU
|BPF_AND
|BPF_K
, tag_bloom_hi
);
308 /* jump to next tag if it does not match */
309 bpf_jmp(ins
, &i
, BPF_JMP
|BPF_JEQ
|BPF_K
, tag_bloom_hi
, 0, 3);
311 /* load device bloom bits in A */
312 bpf_stmt(ins
, &i
, BPF_LD
|BPF_W
|BPF_ABS
, offsetof(struct udev_monitor_netlink_header
, filter_tag_bloom_lo
));
313 /* clear bits (tag bits & bloom bits) */
314 bpf_stmt(ins
, &i
, BPF_ALU
|BPF_AND
|BPF_K
, tag_bloom_lo
);
315 /* jump behind end of tag match block if tag matches */
317 bpf_jmp(ins
, &i
, BPF_JMP
|BPF_JEQ
|BPF_K
, tag_bloom_lo
, 1 + (tag_matches
* 6), 0);
320 /* nothing matched, drop packet */
321 bpf_stmt(ins
, &i
, BPF_RET
|BPF_K
, 0);
324 /* add all subsystem matches */
325 if (udev_list_get_entry(&udev_monitor
->filter_subsystem_list
) != NULL
) {
326 udev_list_entry_foreach(list_entry
, udev_list_get_entry(&udev_monitor
->filter_subsystem_list
)) {
327 unsigned int hash
= util_string_hash32(udev_list_entry_get_name(list_entry
));
329 /* load device subsystem value in A */
330 bpf_stmt(ins
, &i
, BPF_LD
|BPF_W
|BPF_ABS
, offsetof(struct udev_monitor_netlink_header
, filter_subsystem_hash
));
331 if (udev_list_entry_get_value(list_entry
) == NULL
) {
332 /* jump if subsystem does not match */
333 bpf_jmp(ins
, &i
, BPF_JMP
|BPF_JEQ
|BPF_K
, hash
, 0, 1);
335 /* jump if subsystem does not match */
336 bpf_jmp(ins
, &i
, BPF_JMP
|BPF_JEQ
|BPF_K
, hash
, 0, 3);
338 /* load device devtype value in A */
339 bpf_stmt(ins
, &i
, BPF_LD
|BPF_W
|BPF_ABS
, offsetof(struct udev_monitor_netlink_header
, filter_devtype_hash
));
340 /* jump if value does not match */
341 hash
= util_string_hash32(udev_list_entry_get_value(list_entry
));
342 bpf_jmp(ins
, &i
, BPF_JMP
|BPF_JEQ
|BPF_K
, hash
, 0, 1);
345 /* matched, pass packet */
346 bpf_stmt(ins
, &i
, BPF_RET
|BPF_K
, 0xffffffff);
348 if (i
+1 >= ELEMENTSOF(ins
))
352 /* nothing matched, drop packet */
353 bpf_stmt(ins
, &i
, BPF_RET
|BPF_K
, 0);
356 /* matched, pass packet */
357 bpf_stmt(ins
, &i
, BPF_RET
|BPF_K
, 0xffffffff);
360 memzero(&filter
, sizeof(filter
));
363 err
= setsockopt(udev_monitor
->sock
, SOL_SOCKET
, SO_ATTACH_FILTER
, &filter
, sizeof(filter
));
364 return err
< 0 ? -errno
: 0;
367 int udev_monitor_allow_unicast_sender(struct udev_monitor
*udev_monitor
, struct udev_monitor
*sender
)
369 udev_monitor
->snl_trusted_sender
.nl
.nl_pid
= sender
->snl
.nl
.nl_pid
;
373 * udev_monitor_enable_receiving:
374 * @udev_monitor: the monitor which should receive events
376 * Binds the @udev_monitor socket to the event source.
378 * Returns: 0 on success, otherwise a negative error value.
380 _public_
int udev_monitor_enable_receiving(struct udev_monitor
*udev_monitor
)
385 udev_monitor_filter_update(udev_monitor
);
387 if (!udev_monitor
->bound
) {
388 err
= bind(udev_monitor
->sock
,
389 &udev_monitor
->snl
.sa
, sizeof(struct sockaddr_nl
));
391 udev_monitor
->bound
= true;
395 union sockaddr_union snl
;
399 * get the address the kernel has assigned us
400 * it is usually, but not necessarily the pid
402 addrlen
= sizeof(struct sockaddr_nl
);
403 err
= getsockname(udev_monitor
->sock
, &snl
.sa
, &addrlen
);
405 udev_monitor
->snl
.nl
.nl_pid
= snl
.nl
.nl_pid
;
407 log_debug_errno(errno
, "bind failed: %m");
411 /* enable receiving of sender credentials */
412 err
= setsockopt(udev_monitor
->sock
, SOL_SOCKET
, SO_PASSCRED
, &on
, sizeof(on
));
414 log_debug_errno(errno
, "setting SO_PASSCRED failed: %m");
420 * udev_monitor_set_receive_buffer_size:
421 * @udev_monitor: the monitor which should receive events
422 * @size: the size in bytes
424 * Set the size of the kernel socket buffer. This call needs the
425 * appropriate privileges to succeed.
427 * Returns: 0 on success, otherwise -1 on error.
429 _public_
int udev_monitor_set_receive_buffer_size(struct udev_monitor
*udev_monitor
, int size
)
431 if (udev_monitor
== NULL
)
433 return setsockopt(udev_monitor
->sock
, SOL_SOCKET
, SO_RCVBUFFORCE
, &size
, sizeof(size
));
436 int udev_monitor_disconnect(struct udev_monitor
*udev_monitor
)
440 err
= close(udev_monitor
->sock
);
441 udev_monitor
->sock
= -1;
442 return err
< 0 ? -errno
: 0;
447 * @udev_monitor: udev monitor
449 * Take a reference of a udev monitor.
451 * Returns: the passed udev monitor
453 _public_
struct udev_monitor
*udev_monitor_ref(struct udev_monitor
*udev_monitor
)
455 if (udev_monitor
== NULL
)
457 udev_monitor
->refcount
++;
462 * udev_monitor_unref:
463 * @udev_monitor: udev monitor
465 * Drop a reference of a udev monitor. If the refcount reaches zero,
466 * the bound socket will be closed, and the resources of the monitor
471 _public_
struct udev_monitor
*udev_monitor_unref(struct udev_monitor
*udev_monitor
)
473 if (udev_monitor
== NULL
)
475 udev_monitor
->refcount
--;
476 if (udev_monitor
->refcount
> 0)
478 if (udev_monitor
->sock
>= 0)
479 close(udev_monitor
->sock
);
480 udev_list_cleanup(&udev_monitor
->filter_subsystem_list
);
481 udev_list_cleanup(&udev_monitor
->filter_tag_list
);
487 * udev_monitor_get_udev:
488 * @udev_monitor: udev monitor
490 * Retrieve the udev library context the monitor was created with.
492 * Returns: the udev library context
494 _public_
struct udev
*udev_monitor_get_udev(struct udev_monitor
*udev_monitor
)
496 if (udev_monitor
== NULL
)
498 return udev_monitor
->udev
;
502 * udev_monitor_get_fd:
503 * @udev_monitor: udev monitor
505 * Retrieve the socket file descriptor associated with the monitor.
507 * Returns: the socket file descriptor
509 _public_
int udev_monitor_get_fd(struct udev_monitor
*udev_monitor
)
511 if (udev_monitor
== NULL
)
513 return udev_monitor
->sock
;
516 static int passes_filter(struct udev_monitor
*udev_monitor
, struct udev_device
*udev_device
)
518 struct udev_list_entry
*list_entry
;
520 if (udev_list_get_entry(&udev_monitor
->filter_subsystem_list
) == NULL
)
522 udev_list_entry_foreach(list_entry
, udev_list_get_entry(&udev_monitor
->filter_subsystem_list
)) {
523 const char *subsys
= udev_list_entry_get_name(list_entry
);
524 const char *dsubsys
= udev_device_get_subsystem(udev_device
);
526 const char *ddevtype
;
528 if (!streq(dsubsys
, subsys
))
531 devtype
= udev_list_entry_get_value(list_entry
);
534 ddevtype
= udev_device_get_devtype(udev_device
);
535 if (ddevtype
== NULL
)
537 if (streq(ddevtype
, devtype
))
543 if (udev_list_get_entry(&udev_monitor
->filter_tag_list
) == NULL
)
545 udev_list_entry_foreach(list_entry
, udev_list_get_entry(&udev_monitor
->filter_tag_list
)) {
546 const char *tag
= udev_list_entry_get_name(list_entry
);
548 if (udev_device_has_tag(udev_device
, tag
))
555 * udev_monitor_receive_device:
556 * @udev_monitor: udev monitor
558 * Receive data from the udev monitor socket, allocate a new udev
559 * device, fill in the received data, and return the device.
561 * Only socket connections with uid=0 are accepted.
563 * The monitor socket is by default set to NONBLOCK. A variant of poll() on
564 * the file descriptor returned by udev_monitor_get_fd() should to be used to
565 * wake up when new devices arrive, or alternatively the file descriptor
566 * switched into blocking mode.
568 * The initial refcount is 1, and needs to be decremented to
569 * release the resources of the udev device.
571 * Returns: a new udev device, or #NULL, in case of an error
573 _public_
struct udev_device
*udev_monitor_receive_device(struct udev_monitor
*udev_monitor
)
575 struct udev_device
*udev_device
;
578 char cred_msg
[CMSG_SPACE(sizeof(struct ucred
))];
579 struct cmsghdr
*cmsg
;
580 union sockaddr_union snl
;
583 struct udev_monitor_netlink_header nlh
;
588 bool is_initialized
= false;
591 if (udev_monitor
== NULL
)
594 iov
.iov_len
= sizeof(buf
);
595 memzero(&smsg
, sizeof(struct msghdr
));
598 smsg
.msg_control
= cred_msg
;
599 smsg
.msg_controllen
= sizeof(cred_msg
);
600 smsg
.msg_name
= &snl
;
601 smsg
.msg_namelen
= sizeof(snl
);
603 buflen
= recvmsg(udev_monitor
->sock
, &smsg
, 0);
606 log_debug("unable to receive message");
610 if (buflen
< 32 || (smsg
.msg_flags
& MSG_TRUNC
)) {
611 log_debug("invalid message length");
615 if (snl
.nl
.nl_groups
== 0) {
616 /* unicast message, check if we trust the sender */
617 if (udev_monitor
->snl_trusted_sender
.nl
.nl_pid
== 0 ||
618 snl
.nl
.nl_pid
!= udev_monitor
->snl_trusted_sender
.nl
.nl_pid
) {
619 log_debug("unicast netlink message ignored");
622 } else if (snl
.nl
.nl_groups
== UDEV_MONITOR_KERNEL
) {
623 if (snl
.nl
.nl_pid
> 0) {
624 log_debug("multicast kernel netlink message from PID %"PRIu32
" ignored",
630 cmsg
= CMSG_FIRSTHDR(&smsg
);
631 if (cmsg
== NULL
|| cmsg
->cmsg_type
!= SCM_CREDENTIALS
) {
632 log_debug("no sender credentials received, message ignored");
636 cred
= (struct ucred
*)CMSG_DATA(cmsg
);
637 if (cred
->uid
!= 0) {
638 log_debug("sender uid="UID_FMT
", message ignored", cred
->uid
);
642 if (memcmp(buf
.raw
, "libudev", 8) == 0) {
643 /* udev message needs proper version magic */
644 if (buf
.nlh
.magic
!= htonl(UDEV_MONITOR_MAGIC
)) {
645 log_debug("unrecognized message signature (%x != %x)",
646 buf
.nlh
.magic
, htonl(UDEV_MONITOR_MAGIC
));
649 if (buf
.nlh
.properties_off
+32 > (size_t)buflen
) {
653 bufpos
= buf
.nlh
.properties_off
;
655 /* devices received from udev are always initialized */
656 is_initialized
= true;
658 /* kernel message with header */
659 bufpos
= strlen(buf
.raw
) + 1;
660 if ((size_t)bufpos
< sizeof("a@/d") || bufpos
>= buflen
) {
661 log_debug("invalid message length");
665 /* check message header */
666 if (strstr(buf
.raw
, "@/") == NULL
) {
667 log_debug("unrecognized message header");
672 udev_device
= udev_device_new_from_nulstr(udev_monitor
->udev
, &buf
.raw
[bufpos
], buflen
- bufpos
);
677 udev_device_set_is_initialized(udev_device
);
679 /* skip device, if it does not pass the current filter */
680 if (!passes_filter(udev_monitor
, udev_device
)) {
681 struct pollfd pfd
[1];
684 udev_device_unref(udev_device
);
686 /* if something is queued, get next device */
687 pfd
[0].fd
= udev_monitor
->sock
;
688 pfd
[0].events
= POLLIN
;
689 rc
= poll(pfd
, 1, 0);
698 int udev_monitor_send_device(struct udev_monitor
*udev_monitor
,
699 struct udev_monitor
*destination
, struct udev_device
*udev_device
)
707 struct udev_monitor_netlink_header nlh
;
708 struct udev_list_entry
*list_entry
;
709 uint64_t tag_bloom_bits
;
711 blen
= udev_device_get_properties_monitor_buf(udev_device
, &buf
);
715 /* add versioned header */
716 memzero(&nlh
, sizeof(struct udev_monitor_netlink_header
));
717 memcpy(nlh
.prefix
, "libudev", 8);
718 nlh
.magic
= htonl(UDEV_MONITOR_MAGIC
);
719 nlh
.header_size
= sizeof(struct udev_monitor_netlink_header
);
720 val
= udev_device_get_subsystem(udev_device
);
721 nlh
.filter_subsystem_hash
= htonl(util_string_hash32(val
));
722 val
= udev_device_get_devtype(udev_device
);
724 nlh
.filter_devtype_hash
= htonl(util_string_hash32(val
));
725 iov
[0].iov_base
= &nlh
;
726 iov
[0].iov_len
= sizeof(struct udev_monitor_netlink_header
);
728 /* add tag bloom filter */
730 udev_list_entry_foreach(list_entry
, udev_device_get_tags_list_entry(udev_device
))
731 tag_bloom_bits
|= util_string_bloom64(udev_list_entry_get_name(list_entry
));
732 if (tag_bloom_bits
> 0) {
733 nlh
.filter_tag_bloom_hi
= htonl(tag_bloom_bits
>> 32);
734 nlh
.filter_tag_bloom_lo
= htonl(tag_bloom_bits
& 0xffffffff);
737 /* add properties list */
738 nlh
.properties_off
= iov
[0].iov_len
;
739 nlh
.properties_len
= blen
;
740 iov
[1].iov_base
= (char *)buf
;
741 iov
[1].iov_len
= blen
;
743 memzero(&smsg
, sizeof(struct msghdr
));
747 * Use custom address for target, or the default one.
749 * If we send to a multicast group, we will get
750 * ECONNREFUSED, which is expected.
752 if (destination
!= NULL
)
753 smsg
.msg_name
= &destination
->snl
;
755 smsg
.msg_name
= &udev_monitor
->snl_destination
;
756 smsg
.msg_namelen
= sizeof(struct sockaddr_nl
);
757 count
= sendmsg(udev_monitor
->sock
, &smsg
, 0);
758 log_debug("passed %zi bytes to netlink monitor %p", count
, udev_monitor
);
763 * udev_monitor_filter_add_match_subsystem_devtype:
764 * @udev_monitor: the monitor
765 * @subsystem: the subsystem value to match the incoming devices against
766 * @devtype: the devtype value to match the incoming devices against
768 * This filter is efficiently executed inside the kernel, and libudev subscribers
769 * will usually not be woken up for devices which do not match.
771 * The filter must be installed before the monitor is switched to listening mode.
773 * Returns: 0 on success, otherwise a negative error value.
775 _public_
int udev_monitor_filter_add_match_subsystem_devtype(struct udev_monitor
*udev_monitor
, const char *subsystem
, const char *devtype
)
777 if (udev_monitor
== NULL
)
779 if (subsystem
== NULL
)
781 if (udev_list_entry_add(&udev_monitor
->filter_subsystem_list
, subsystem
, devtype
) == NULL
)
787 * udev_monitor_filter_add_match_tag:
788 * @udev_monitor: the monitor
789 * @tag: the name of a tag
791 * This filter is efficiently executed inside the kernel, and libudev subscribers
792 * will usually not be woken up for devices which do not match.
794 * The filter must be installed before the monitor is switched to listening mode.
796 * Returns: 0 on success, otherwise a negative error value.
798 _public_
int udev_monitor_filter_add_match_tag(struct udev_monitor
*udev_monitor
, const char *tag
)
800 if (udev_monitor
== NULL
)
804 if (udev_list_entry_add(&udev_monitor
->filter_tag_list
, tag
, NULL
) == NULL
)
810 * udev_monitor_filter_remove:
811 * @udev_monitor: monitor
813 * Remove all filters from monitor.
815 * Returns: 0 on success, otherwise a negative error value.
817 _public_
int udev_monitor_filter_remove(struct udev_monitor
*udev_monitor
)
819 static struct sock_fprog filter
= { 0, NULL
};
821 udev_list_cleanup(&udev_monitor
->filter_subsystem_list
);
822 return setsockopt(udev_monitor
->sock
, SOL_SOCKET
, SO_ATTACH_FILTER
, &filter
, sizeof(filter
));