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/>.
21 #include <linux/filter.h>
22 #include <linux/netlink.h>
28 #include <sys/socket.h>
33 #include "alloc-util.h"
36 #include "formats-util.h"
37 #include "libudev-private.h"
39 #include "socket-util.h"
40 #include "string-util.h"
43 * SECTION:libudev-monitor
44 * @short_description: device event source
46 * Connects to a device event source.
52 * Opaque object handling an event source.
58 union sockaddr_union snl
;
59 union sockaddr_union snl_trusted_sender
;
60 union sockaddr_union snl_destination
;
62 struct udev_list filter_subsystem_list
;
63 struct udev_list filter_tag_list
;
67 enum udev_monitor_netlink_group
{
73 #define UDEV_MONITOR_MAGIC 0xfeedcafe
74 struct udev_monitor_netlink_header
{
75 /* "libudev" prefix to distinguish libudev and kernel messages */
78 * magic to protect against daemon <-> library message format mismatch
79 * used in the kernel from socket filter rules; needs to be stored in network order
82 /* total length of header structure known to the sender */
83 unsigned int header_size
;
84 /* properties string buffer */
85 unsigned int properties_off
;
86 unsigned int properties_len
;
88 * hashes of primary device properties strings, to let libudev subscribers
89 * use in-kernel socket filters; values need to be stored in network order
91 unsigned int filter_subsystem_hash
;
92 unsigned int filter_devtype_hash
;
93 unsigned int filter_tag_bloom_hi
;
94 unsigned int filter_tag_bloom_lo
;
97 static struct udev_monitor
*udev_monitor_new(struct udev
*udev
)
99 struct udev_monitor
*udev_monitor
;
101 udev_monitor
= new0(struct udev_monitor
, 1);
102 if (udev_monitor
== NULL
)
104 udev_monitor
->refcount
= 1;
105 udev_monitor
->udev
= udev
;
106 udev_list_init(udev
, &udev_monitor
->filter_subsystem_list
, false);
107 udev_list_init(udev
, &udev_monitor
->filter_tag_list
, true);
111 /* we consider udev running when /dev is on devtmpfs */
112 static bool udev_has_devtmpfs(struct udev
*udev
) {
114 union file_handle_union h
= FILE_HANDLE_INIT
;
115 _cleanup_fclose_
FILE *f
= NULL
;
116 char line
[LINE_MAX
], *e
;
120 r
= name_to_handle_at(AT_FDCWD
, "/dev", &h
.handle
, &mount_id
, 0);
122 if (errno
!= EOPNOTSUPP
)
123 log_debug_errno(errno
, "name_to_handle_at on /dev: %m");
127 f
= fopen("/proc/self/mountinfo", "re");
131 FOREACH_LINE(line
, f
, return false) {
134 if (sscanf(line
, "%i", &mid
) != 1)
140 e
= strstr(line
, " - ");
144 /* accept any name that starts with the currently expected type */
145 if (startswith(e
+ 3, "devtmpfs"))
152 static void monitor_set_nl_address(struct udev_monitor
*udev_monitor
) {
153 union sockaddr_union snl
;
157 assert(udev_monitor
);
159 /* get the address the kernel has assigned us
160 * it is usually, but not necessarily the pid
162 addrlen
= sizeof(struct sockaddr_nl
);
163 r
= getsockname(udev_monitor
->sock
, &snl
.sa
, &addrlen
);
165 udev_monitor
->snl
.nl
.nl_pid
= snl
.nl
.nl_pid
;
168 struct udev_monitor
*udev_monitor_new_from_netlink_fd(struct udev
*udev
, const char *name
, int fd
)
170 struct udev_monitor
*udev_monitor
;
177 group
= UDEV_MONITOR_NONE
;
178 else if (streq(name
, "udev")) {
180 * We do not support subscribing to uevents if no instance of
181 * udev is running. Uevents would otherwise broadcast the
182 * processing data of the host into containers, which is not
185 * Containers will currently not get any udev uevents, until
186 * a supporting infrastructure is available.
188 * We do not set a netlink multicast group here, so the socket
189 * will not receive any messages.
191 if (access("/run/udev/control", F_OK
) < 0 && !udev_has_devtmpfs(udev
)) {
192 log_debug("the udev service seems not to be active, disable the monitor");
193 group
= UDEV_MONITOR_NONE
;
195 group
= UDEV_MONITOR_UDEV
;
196 } else if (streq(name
, "kernel"))
197 group
= UDEV_MONITOR_KERNEL
;
201 udev_monitor
= udev_monitor_new(udev
);
202 if (udev_monitor
== NULL
)
206 udev_monitor
->sock
= socket(PF_NETLINK
, SOCK_RAW
|SOCK_CLOEXEC
|SOCK_NONBLOCK
, NETLINK_KOBJECT_UEVENT
);
207 if (udev_monitor
->sock
< 0) {
208 log_debug_errno(errno
, "error getting socket: %m");
213 udev_monitor
->bound
= true;
214 udev_monitor
->sock
= fd
;
215 monitor_set_nl_address(udev_monitor
);
218 udev_monitor
->snl
.nl
.nl_family
= AF_NETLINK
;
219 udev_monitor
->snl
.nl
.nl_groups
= group
;
221 /* default destination for sending */
222 udev_monitor
->snl_destination
.nl
.nl_family
= AF_NETLINK
;
223 udev_monitor
->snl_destination
.nl
.nl_groups
= UDEV_MONITOR_UDEV
;
229 * udev_monitor_new_from_netlink:
230 * @udev: udev library context
231 * @name: name of event source
233 * Create new udev monitor and connect to a specified event
234 * source. Valid sources identifiers are "udev" and "kernel".
236 * Applications should usually not connect directly to the
237 * "kernel" events, because the devices might not be useable
238 * at that time, before udev has configured them, and created
239 * device nodes. Accessing devices at the same time as udev,
240 * might result in unpredictable behavior. The "udev" events
241 * are sent out after udev has finished its event processing,
242 * all rules have been processed, and needed device nodes are
245 * The initial refcount is 1, and needs to be decremented to
246 * release the resources of the udev monitor.
248 * Returns: a new udev monitor, or #NULL, in case of an error
250 _public_
struct udev_monitor
*udev_monitor_new_from_netlink(struct udev
*udev
, const char *name
)
252 return udev_monitor_new_from_netlink_fd(udev
, name
, -1);
255 static inline void bpf_stmt(struct sock_filter
*inss
, unsigned int *i
,
256 unsigned short code
, unsigned int data
)
258 struct sock_filter
*ins
= &inss
[*i
];
265 static inline void bpf_jmp(struct sock_filter
*inss
, unsigned int *i
,
266 unsigned short code
, unsigned int data
,
267 unsigned short jt
, unsigned short jf
)
269 struct sock_filter
*ins
= &inss
[*i
];
279 * udev_monitor_filter_update:
280 * @udev_monitor: monitor
282 * Update the installed socket filter. This is only needed,
283 * if the filter was removed or changed.
285 * Returns: 0 on success, otherwise a negative error value.
287 _public_
int udev_monitor_filter_update(struct udev_monitor
*udev_monitor
)
289 struct sock_filter ins
[512];
290 struct sock_fprog filter
;
292 struct udev_list_entry
*list_entry
;
295 if (udev_list_get_entry(&udev_monitor
->filter_subsystem_list
) == NULL
&&
296 udev_list_get_entry(&udev_monitor
->filter_tag_list
) == NULL
)
299 memzero(ins
, sizeof(ins
));
302 /* load magic in A */
303 bpf_stmt(ins
, &i
, BPF_LD
|BPF_W
|BPF_ABS
, offsetof(struct udev_monitor_netlink_header
, magic
));
304 /* jump if magic matches */
305 bpf_jmp(ins
, &i
, BPF_JMP
|BPF_JEQ
|BPF_K
, UDEV_MONITOR_MAGIC
, 1, 0);
306 /* wrong magic, pass packet */
307 bpf_stmt(ins
, &i
, BPF_RET
|BPF_K
, 0xffffffff);
309 if (udev_list_get_entry(&udev_monitor
->filter_tag_list
) != NULL
) {
312 /* count tag matches, to calculate end of tag match block */
314 udev_list_entry_foreach(list_entry
, udev_list_get_entry(&udev_monitor
->filter_tag_list
))
317 /* add all tags matches */
318 udev_list_entry_foreach(list_entry
, udev_list_get_entry(&udev_monitor
->filter_tag_list
)) {
319 uint64_t tag_bloom_bits
= util_string_bloom64(udev_list_entry_get_name(list_entry
));
320 uint32_t tag_bloom_hi
= tag_bloom_bits
>> 32;
321 uint32_t tag_bloom_lo
= tag_bloom_bits
& 0xffffffff;
323 /* load device bloom bits in A */
324 bpf_stmt(ins
, &i
, BPF_LD
|BPF_W
|BPF_ABS
, offsetof(struct udev_monitor_netlink_header
, filter_tag_bloom_hi
));
325 /* clear bits (tag bits & bloom bits) */
326 bpf_stmt(ins
, &i
, BPF_ALU
|BPF_AND
|BPF_K
, tag_bloom_hi
);
327 /* jump to next tag if it does not match */
328 bpf_jmp(ins
, &i
, BPF_JMP
|BPF_JEQ
|BPF_K
, tag_bloom_hi
, 0, 3);
330 /* load device bloom bits in A */
331 bpf_stmt(ins
, &i
, BPF_LD
|BPF_W
|BPF_ABS
, offsetof(struct udev_monitor_netlink_header
, filter_tag_bloom_lo
));
332 /* clear bits (tag bits & bloom bits) */
333 bpf_stmt(ins
, &i
, BPF_ALU
|BPF_AND
|BPF_K
, tag_bloom_lo
);
334 /* jump behind end of tag match block if tag matches */
336 bpf_jmp(ins
, &i
, BPF_JMP
|BPF_JEQ
|BPF_K
, tag_bloom_lo
, 1 + (tag_matches
* 6), 0);
339 /* nothing matched, drop packet */
340 bpf_stmt(ins
, &i
, BPF_RET
|BPF_K
, 0);
343 /* add all subsystem matches */
344 if (udev_list_get_entry(&udev_monitor
->filter_subsystem_list
) != NULL
) {
345 udev_list_entry_foreach(list_entry
, udev_list_get_entry(&udev_monitor
->filter_subsystem_list
)) {
346 unsigned int hash
= util_string_hash32(udev_list_entry_get_name(list_entry
));
348 /* load device subsystem value in A */
349 bpf_stmt(ins
, &i
, BPF_LD
|BPF_W
|BPF_ABS
, offsetof(struct udev_monitor_netlink_header
, filter_subsystem_hash
));
350 if (udev_list_entry_get_value(list_entry
) == NULL
) {
351 /* jump if subsystem does not match */
352 bpf_jmp(ins
, &i
, BPF_JMP
|BPF_JEQ
|BPF_K
, hash
, 0, 1);
354 /* jump if subsystem does not match */
355 bpf_jmp(ins
, &i
, BPF_JMP
|BPF_JEQ
|BPF_K
, hash
, 0, 3);
357 /* load device devtype value in A */
358 bpf_stmt(ins
, &i
, BPF_LD
|BPF_W
|BPF_ABS
, offsetof(struct udev_monitor_netlink_header
, filter_devtype_hash
));
359 /* jump if value does not match */
360 hash
= util_string_hash32(udev_list_entry_get_value(list_entry
));
361 bpf_jmp(ins
, &i
, BPF_JMP
|BPF_JEQ
|BPF_K
, hash
, 0, 1);
364 /* matched, pass packet */
365 bpf_stmt(ins
, &i
, BPF_RET
|BPF_K
, 0xffffffff);
367 if (i
+1 >= ELEMENTSOF(ins
))
371 /* nothing matched, drop packet */
372 bpf_stmt(ins
, &i
, BPF_RET
|BPF_K
, 0);
375 /* matched, pass packet */
376 bpf_stmt(ins
, &i
, BPF_RET
|BPF_K
, 0xffffffff);
379 memzero(&filter
, sizeof(filter
));
382 err
= setsockopt(udev_monitor
->sock
, SOL_SOCKET
, SO_ATTACH_FILTER
, &filter
, sizeof(filter
));
383 return err
< 0 ? -errno
: 0;
386 int udev_monitor_allow_unicast_sender(struct udev_monitor
*udev_monitor
, struct udev_monitor
*sender
)
388 udev_monitor
->snl_trusted_sender
.nl
.nl_pid
= sender
->snl
.nl
.nl_pid
;
393 * udev_monitor_enable_receiving:
394 * @udev_monitor: the monitor which should receive events
396 * Binds the @udev_monitor socket to the event source.
398 * Returns: 0 on success, otherwise a negative error value.
400 _public_
int udev_monitor_enable_receiving(struct udev_monitor
*udev_monitor
)
405 udev_monitor_filter_update(udev_monitor
);
407 if (!udev_monitor
->bound
) {
408 err
= bind(udev_monitor
->sock
,
409 &udev_monitor
->snl
.sa
, sizeof(struct sockaddr_nl
));
411 udev_monitor
->bound
= true;
415 monitor_set_nl_address(udev_monitor
);
417 log_debug_errno(errno
, "bind failed: %m");
421 /* enable receiving of sender credentials */
422 err
= setsockopt(udev_monitor
->sock
, SOL_SOCKET
, SO_PASSCRED
, &on
, sizeof(on
));
424 log_debug_errno(errno
, "setting SO_PASSCRED failed: %m");
430 * udev_monitor_set_receive_buffer_size:
431 * @udev_monitor: the monitor which should receive events
432 * @size: the size in bytes
434 * Set the size of the kernel socket buffer. This call needs the
435 * appropriate privileges to succeed.
437 * Returns: 0 on success, otherwise -1 on error.
439 _public_
int udev_monitor_set_receive_buffer_size(struct udev_monitor
*udev_monitor
, int size
)
441 if (udev_monitor
== NULL
)
443 return setsockopt(udev_monitor
->sock
, SOL_SOCKET
, SO_RCVBUFFORCE
, &size
, sizeof(size
));
446 int udev_monitor_disconnect(struct udev_monitor
*udev_monitor
)
450 err
= close(udev_monitor
->sock
);
451 udev_monitor
->sock
= -1;
452 return err
< 0 ? -errno
: 0;
457 * @udev_monitor: udev monitor
459 * Take a reference of a udev monitor.
461 * Returns: the passed udev monitor
463 _public_
struct udev_monitor
*udev_monitor_ref(struct udev_monitor
*udev_monitor
)
465 if (udev_monitor
== NULL
)
467 udev_monitor
->refcount
++;
472 * udev_monitor_unref:
473 * @udev_monitor: udev monitor
475 * Drop a reference of a udev monitor. If the refcount reaches zero,
476 * the bound socket will be closed, and the resources of the monitor
481 _public_
struct udev_monitor
*udev_monitor_unref(struct udev_monitor
*udev_monitor
)
483 if (udev_monitor
== NULL
)
485 udev_monitor
->refcount
--;
486 if (udev_monitor
->refcount
> 0)
488 if (udev_monitor
->sock
>= 0)
489 close(udev_monitor
->sock
);
490 udev_list_cleanup(&udev_monitor
->filter_subsystem_list
);
491 udev_list_cleanup(&udev_monitor
->filter_tag_list
);
497 * udev_monitor_get_udev:
498 * @udev_monitor: udev monitor
500 * Retrieve the udev library context the monitor was created with.
502 * Returns: the udev library context
504 _public_
struct udev
*udev_monitor_get_udev(struct udev_monitor
*udev_monitor
)
506 if (udev_monitor
== NULL
)
508 return udev_monitor
->udev
;
512 * udev_monitor_get_fd:
513 * @udev_monitor: udev monitor
515 * Retrieve the socket file descriptor associated with the monitor.
517 * Returns: the socket file descriptor
519 _public_
int udev_monitor_get_fd(struct udev_monitor
*udev_monitor
)
521 if (udev_monitor
== NULL
)
523 return udev_monitor
->sock
;
526 static int passes_filter(struct udev_monitor
*udev_monitor
, struct udev_device
*udev_device
)
528 struct udev_list_entry
*list_entry
;
530 if (udev_list_get_entry(&udev_monitor
->filter_subsystem_list
) == NULL
)
532 udev_list_entry_foreach(list_entry
, udev_list_get_entry(&udev_monitor
->filter_subsystem_list
)) {
533 const char *subsys
= udev_list_entry_get_name(list_entry
);
534 const char *dsubsys
= udev_device_get_subsystem(udev_device
);
536 const char *ddevtype
;
538 if (!streq(dsubsys
, subsys
))
541 devtype
= udev_list_entry_get_value(list_entry
);
544 ddevtype
= udev_device_get_devtype(udev_device
);
545 if (ddevtype
== NULL
)
547 if (streq(ddevtype
, devtype
))
553 if (udev_list_get_entry(&udev_monitor
->filter_tag_list
) == NULL
)
555 udev_list_entry_foreach(list_entry
, udev_list_get_entry(&udev_monitor
->filter_tag_list
)) {
556 const char *tag
= udev_list_entry_get_name(list_entry
);
558 if (udev_device_has_tag(udev_device
, tag
))
565 * udev_monitor_receive_device:
566 * @udev_monitor: udev monitor
568 * Receive data from the udev monitor socket, allocate a new udev
569 * device, fill in the received data, and return the device.
571 * Only socket connections with uid=0 are accepted.
573 * The monitor socket is by default set to NONBLOCK. A variant of poll() on
574 * the file descriptor returned by udev_monitor_get_fd() should to be used to
575 * wake up when new devices arrive, or alternatively the file descriptor
576 * switched into blocking mode.
578 * The initial refcount is 1, and needs to be decremented to
579 * release the resources of the udev device.
581 * Returns: a new udev device, or #NULL, in case of an error
583 _public_
struct udev_device
*udev_monitor_receive_device(struct udev_monitor
*udev_monitor
)
585 struct udev_device
*udev_device
;
588 char cred_msg
[CMSG_SPACE(sizeof(struct ucred
))];
589 struct cmsghdr
*cmsg
;
590 union sockaddr_union snl
;
593 struct udev_monitor_netlink_header nlh
;
598 bool is_initialized
= false;
601 if (udev_monitor
== NULL
)
604 iov
.iov_len
= sizeof(buf
);
605 memzero(&smsg
, sizeof(struct msghdr
));
608 smsg
.msg_control
= cred_msg
;
609 smsg
.msg_controllen
= sizeof(cred_msg
);
610 smsg
.msg_name
= &snl
;
611 smsg
.msg_namelen
= sizeof(snl
);
613 buflen
= recvmsg(udev_monitor
->sock
, &smsg
, 0);
616 log_debug("unable to receive message");
620 if (buflen
< 32 || (smsg
.msg_flags
& MSG_TRUNC
)) {
621 log_debug("invalid message length");
625 if (snl
.nl
.nl_groups
== 0) {
626 /* unicast message, check if we trust the sender */
627 if (udev_monitor
->snl_trusted_sender
.nl
.nl_pid
== 0 ||
628 snl
.nl
.nl_pid
!= udev_monitor
->snl_trusted_sender
.nl
.nl_pid
) {
629 log_debug("unicast netlink message ignored");
632 } else if (snl
.nl
.nl_groups
== UDEV_MONITOR_KERNEL
) {
633 if (snl
.nl
.nl_pid
> 0) {
634 log_debug("multicast kernel netlink message from PID %"PRIu32
" ignored",
640 cmsg
= CMSG_FIRSTHDR(&smsg
);
641 if (cmsg
== NULL
|| cmsg
->cmsg_type
!= SCM_CREDENTIALS
) {
642 log_debug("no sender credentials received, message ignored");
646 cred
= (struct ucred
*)CMSG_DATA(cmsg
);
647 if (cred
->uid
!= 0) {
648 log_debug("sender uid="UID_FMT
", message ignored", cred
->uid
);
652 if (memcmp(buf
.raw
, "libudev", 8) == 0) {
653 /* udev message needs proper version magic */
654 if (buf
.nlh
.magic
!= htonl(UDEV_MONITOR_MAGIC
)) {
655 log_debug("unrecognized message signature (%x != %x)",
656 buf
.nlh
.magic
, htonl(UDEV_MONITOR_MAGIC
));
659 if (buf
.nlh
.properties_off
+32 > (size_t)buflen
) {
660 log_debug("message smaller than expected (%u > %zd)",
661 buf
.nlh
.properties_off
+32, buflen
);
665 bufpos
= buf
.nlh
.properties_off
;
667 /* devices received from udev are always initialized */
668 is_initialized
= true;
670 /* kernel message with header */
671 bufpos
= strlen(buf
.raw
) + 1;
672 if ((size_t)bufpos
< sizeof("a@/d") || bufpos
>= buflen
) {
673 log_debug("invalid message length");
677 /* check message header */
678 if (strstr(buf
.raw
, "@/") == NULL
) {
679 log_debug("unrecognized message header");
684 udev_device
= udev_device_new_from_nulstr(udev_monitor
->udev
, &buf
.raw
[bufpos
], buflen
- bufpos
);
686 log_debug("could not create device: %m");
691 udev_device_set_is_initialized(udev_device
);
693 /* skip device, if it does not pass the current filter */
694 if (!passes_filter(udev_monitor
, udev_device
)) {
695 struct pollfd pfd
[1];
698 udev_device_unref(udev_device
);
700 /* if something is queued, get next device */
701 pfd
[0].fd
= udev_monitor
->sock
;
702 pfd
[0].events
= POLLIN
;
703 rc
= poll(pfd
, 1, 0);
712 int udev_monitor_send_device(struct udev_monitor
*udev_monitor
,
713 struct udev_monitor
*destination
, struct udev_device
*udev_device
)
715 const char *buf
, *val
;
717 struct udev_monitor_netlink_header nlh
= {
719 .magic
= htonl(UDEV_MONITOR_MAGIC
),
720 .header_size
= sizeof nlh
,
722 struct iovec iov
[2] = {
723 { .iov_base
= &nlh
, .iov_len
= sizeof nlh
},
725 struct msghdr smsg
= {
729 struct udev_list_entry
*list_entry
;
730 uint64_t tag_bloom_bits
;
732 blen
= udev_device_get_properties_monitor_buf(udev_device
, &buf
);
734 log_debug("device buffer is too small to contain a valid device");
738 /* fill in versioned header */
739 val
= udev_device_get_subsystem(udev_device
);
740 nlh
.filter_subsystem_hash
= htonl(util_string_hash32(val
));
742 val
= udev_device_get_devtype(udev_device
);
744 nlh
.filter_devtype_hash
= htonl(util_string_hash32(val
));
746 /* add tag bloom filter */
748 udev_list_entry_foreach(list_entry
, udev_device_get_tags_list_entry(udev_device
))
749 tag_bloom_bits
|= util_string_bloom64(udev_list_entry_get_name(list_entry
));
750 if (tag_bloom_bits
> 0) {
751 nlh
.filter_tag_bloom_hi
= htonl(tag_bloom_bits
>> 32);
752 nlh
.filter_tag_bloom_lo
= htonl(tag_bloom_bits
& 0xffffffff);
755 /* add properties list */
756 nlh
.properties_off
= iov
[0].iov_len
;
757 nlh
.properties_len
= blen
;
758 iov
[1].iov_base
= (char *)buf
;
759 iov
[1].iov_len
= blen
;
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.
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);
774 if (!destination
&& errno
== ECONNREFUSED
) {
775 log_debug("passed device to netlink monitor %p", udev_monitor
);
781 log_debug("passed %zi byte device to netlink monitor %p", count
, udev_monitor
);
786 * udev_monitor_filter_add_match_subsystem_devtype:
787 * @udev_monitor: the monitor
788 * @subsystem: the subsystem value to match the incoming devices against
789 * @devtype: the devtype value to match the incoming devices against
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_subsystem_devtype(struct udev_monitor
*udev_monitor
, const char *subsystem
, const char *devtype
)
800 if (udev_monitor
== NULL
)
802 if (subsystem
== NULL
)
804 if (udev_list_entry_add(&udev_monitor
->filter_subsystem_list
, subsystem
, devtype
) == NULL
)
810 * udev_monitor_filter_add_match_tag:
811 * @udev_monitor: the monitor
812 * @tag: the name of a tag
814 * This filter is efficiently executed inside the kernel, and libudev subscribers
815 * will usually not be woken up for devices which do not match.
817 * The filter must be installed before the monitor is switched to listening mode.
819 * Returns: 0 on success, otherwise a negative error value.
821 _public_
int udev_monitor_filter_add_match_tag(struct udev_monitor
*udev_monitor
, const char *tag
)
823 if (udev_monitor
== NULL
)
827 if (udev_list_entry_add(&udev_monitor
->filter_tag_list
, tag
, NULL
) == NULL
)
833 * udev_monitor_filter_remove:
834 * @udev_monitor: monitor
836 * Remove all filters from monitor.
838 * Returns: 0 on success, otherwise a negative error value.
840 _public_
int udev_monitor_filter_remove(struct udev_monitor
*udev_monitor
)
842 static struct sock_fprog filter
= { 0, NULL
};
844 udev_list_cleanup(&udev_monitor
->filter_subsystem_list
);
845 return setsockopt(udev_monitor
->sock
, SOL_SOCKET
, SO_ATTACH_FILTER
, &filter
, sizeof(filter
));