libudev-monitor.c revision cf0fbc49e67b55f8d346fc94de28c90113505297
/***
This file is part of systemd.
Copyright 2008-2012 Kay Sievers <kay@vrfy.org>
systemd is free software; you can redistribute it and/or modify it
under the terms of the GNU Lesser General Public License as published by
the Free Software Foundation; either version 2.1 of the License, or
(at your option) any later version.
systemd is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public License
along with systemd; If not, see <http://www.gnu.org/licenses/>.
***/
#include <errno.h>
#include <linux/filter.h>
#include <linux/netlink.h>
#include <poll.h>
#include <stddef.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/socket.h>
#include <unistd.h>
#include "alloc-util.h"
#include "fd-util.h"
#include "fileio.h"
#include "formats-util.h"
#include "libudev-private.h"
#include "libudev.h"
#include "missing.h"
#include "mount-util.h"
#include "socket-util.h"
#include "string-util.h"
/**
* SECTION:libudev-monitor
* @short_description: device event source
*
* Connects to a device event source.
*/
/**
* udev_monitor:
*
* Opaque object handling an event source.
*/
struct udev_monitor {
struct udev *udev;
int refcount;
int sock;
union sockaddr_union snl;
union sockaddr_union snl_trusted_sender;
union sockaddr_union snl_destination;
socklen_t addrlen;
struct udev_list filter_subsystem_list;
struct udev_list filter_tag_list;
bool bound;
};
enum udev_monitor_netlink_group {
UDEV_MONITOR_NONE,
UDEV_MONITOR_KERNEL,
UDEV_MONITOR_UDEV,
};
#define UDEV_MONITOR_MAGIC 0xfeedcafe
struct udev_monitor_netlink_header {
/* "libudev" prefix to distinguish libudev and kernel messages */
char prefix[8];
/*
* magic to protect against daemon <-> library message format mismatch
* used in the kernel from socket filter rules; needs to be stored in network order
*/
unsigned int magic;
/* total length of header structure known to the sender */
unsigned int header_size;
/* properties string buffer */
unsigned int properties_off;
unsigned int properties_len;
/*
* hashes of primary device properties strings, to let libudev subscribers
* use in-kernel socket filters; values need to be stored in network order
*/
unsigned int filter_subsystem_hash;
unsigned int filter_devtype_hash;
unsigned int filter_tag_bloom_hi;
unsigned int filter_tag_bloom_lo;
};
static struct udev_monitor *udev_monitor_new(struct udev *udev)
{
struct udev_monitor *udev_monitor;
udev_monitor = new0(struct udev_monitor, 1);
if (udev_monitor == NULL)
return NULL;
udev_monitor->refcount = 1;
udev_monitor->udev = udev;
udev_list_init(udev, &udev_monitor->filter_subsystem_list, false);
udev_list_init(udev, &udev_monitor->filter_tag_list, true);
return udev_monitor;
}
/* we consider udev running when /dev is on devtmpfs */
static bool udev_has_devtmpfs(struct udev *udev) {
union file_handle_union h = FILE_HANDLE_INIT;
_cleanup_fclose_ FILE *f = NULL;
char line[LINE_MAX], *e;
int mount_id;
int r;
r = name_to_handle_at(AT_FDCWD, "/dev", &h.handle, &mount_id, 0);
if (r < 0) {
if (errno != EOPNOTSUPP)
log_debug_errno(errno, "name_to_handle_at on /dev: %m");
return false;
}
f = fopen("/proc/self/mountinfo", "re");
if (!f)
return false;
FOREACH_LINE(line, f, return false) {
int mid;
if (sscanf(line, "%i", &mid) != 1)
continue;
if (mid != mount_id)
continue;
e = strstr(line, " - ");
if (!e)
continue;
/* accept any name that starts with the currently expected type */
if (startswith(e + 3, "devtmpfs"))
return true;
}
return false;
}
static void monitor_set_nl_address(struct udev_monitor *udev_monitor) {
union sockaddr_union snl;
socklen_t addrlen;
int r;
assert(udev_monitor);
/* get the address the kernel has assigned us
* it is usually, but not necessarily the pid
*/
addrlen = sizeof(struct sockaddr_nl);
r = getsockname(udev_monitor->sock, &snl.sa, &addrlen);
if (r >= 0)
udev_monitor->snl.nl.nl_pid = snl.nl.nl_pid;
}
struct udev_monitor *udev_monitor_new_from_netlink_fd(struct udev *udev, const char *name, int fd)
{
struct udev_monitor *udev_monitor;
unsigned int group;
if (udev == NULL)
return NULL;
if (name == NULL)
group = UDEV_MONITOR_NONE;
else if (streq(name, "udev")) {
/*
* We do not support subscribing to uevents if no instance of
* udev is running. Uevents would otherwise broadcast the
* processing data of the host into containers, which is not
* desired.
*
* Containers will currently not get any udev uevents, until
* a supporting infrastructure is available.
*
* We do not set a netlink multicast group here, so the socket
* will not receive any messages.
*/
if (access("/run/udev/control", F_OK) < 0 && !udev_has_devtmpfs(udev)) {
log_debug("the udev service seems not to be active, disable the monitor");
group = UDEV_MONITOR_NONE;
} else
group = UDEV_MONITOR_UDEV;
} else if (streq(name, "kernel"))
group = UDEV_MONITOR_KERNEL;
else
return NULL;
udev_monitor = udev_monitor_new(udev);
if (udev_monitor == NULL)
return NULL;
if (fd < 0) {
udev_monitor->sock = socket(PF_NETLINK, SOCK_RAW|SOCK_CLOEXEC|SOCK_NONBLOCK, NETLINK_KOBJECT_UEVENT);
if (udev_monitor->sock < 0) {
log_debug_errno(errno, "error getting socket: %m");
free(udev_monitor);
return NULL;
}
} else {
udev_monitor->bound = true;
udev_monitor->sock = fd;
monitor_set_nl_address(udev_monitor);
}
udev_monitor->snl.nl.nl_family = AF_NETLINK;
udev_monitor->snl.nl.nl_groups = group;
/* default destination for sending */
udev_monitor->snl_destination.nl.nl_family = AF_NETLINK;
udev_monitor->snl_destination.nl.nl_groups = UDEV_MONITOR_UDEV;
return udev_monitor;
}
/**
* udev_monitor_new_from_netlink:
* @udev: udev library context
* @name: name of event source
*
* Create new udev monitor and connect to a specified event
* source. Valid sources identifiers are "udev" and "kernel".
*
* Applications should usually not connect directly to the
* "kernel" events, because the devices might not be useable
* at that time, before udev has configured them, and created
* device nodes. Accessing devices at the same time as udev,
* might result in unpredictable behavior. The "udev" events
* are sent out after udev has finished its event processing,
* all rules have been processed, and needed device nodes are
* created.
*
* The initial refcount is 1, and needs to be decremented to
* release the resources of the udev monitor.
*
* Returns: a new udev monitor, or #NULL, in case of an error
**/
_public_ struct udev_monitor *udev_monitor_new_from_netlink(struct udev *udev, const char *name)
{
return udev_monitor_new_from_netlink_fd(udev, name, -1);
}
static inline void bpf_stmt(struct sock_filter *inss, unsigned int *i,
unsigned short code, unsigned int data)
{
struct sock_filter *ins = &inss[*i];
ins->code = code;
ins->k = data;
(*i)++;
}
static inline void bpf_jmp(struct sock_filter *inss, unsigned int *i,
unsigned short code, unsigned int data,
unsigned short jt, unsigned short jf)
{
struct sock_filter *ins = &inss[*i];
ins->code = code;
ins->jt = jt;
ins->jf = jf;
ins->k = data;
(*i)++;
}
/**
* udev_monitor_filter_update:
* @udev_monitor: monitor
*
* Update the installed socket filter. This is only needed,
* if the filter was removed or changed.
*
* Returns: 0 on success, otherwise a negative error value.
*/
_public_ int udev_monitor_filter_update(struct udev_monitor *udev_monitor)
{
struct sock_filter ins[512];
struct sock_fprog filter;
unsigned int i;
struct udev_list_entry *list_entry;
int err;
if (udev_list_get_entry(&udev_monitor->filter_subsystem_list) == NULL &&
udev_list_get_entry(&udev_monitor->filter_tag_list) == NULL)
return 0;
memzero(ins, sizeof(ins));
i = 0;
/* load magic in A */
bpf_stmt(ins, &i, BPF_LD|BPF_W|BPF_ABS, offsetof(struct udev_monitor_netlink_header, magic));
/* jump if magic matches */
bpf_jmp(ins, &i, BPF_JMP|BPF_JEQ|BPF_K, UDEV_MONITOR_MAGIC, 1, 0);
/* wrong magic, pass packet */
bpf_stmt(ins, &i, BPF_RET|BPF_K, 0xffffffff);
if (udev_list_get_entry(&udev_monitor->filter_tag_list) != NULL) {
int tag_matches;
/* count tag matches, to calculate end of tag match block */
tag_matches = 0;
udev_list_entry_foreach(list_entry, udev_list_get_entry(&udev_monitor->filter_tag_list))
tag_matches++;
/* add all tags matches */
udev_list_entry_foreach(list_entry, udev_list_get_entry(&udev_monitor->filter_tag_list)) {
uint64_t tag_bloom_bits = util_string_bloom64(udev_list_entry_get_name(list_entry));
uint32_t tag_bloom_hi = tag_bloom_bits >> 32;
uint32_t tag_bloom_lo = tag_bloom_bits & 0xffffffff;
/* load device bloom bits in A */
bpf_stmt(ins, &i, BPF_LD|BPF_W|BPF_ABS, offsetof(struct udev_monitor_netlink_header, filter_tag_bloom_hi));
/* clear bits (tag bits & bloom bits) */
bpf_stmt(ins, &i, BPF_ALU|BPF_AND|BPF_K, tag_bloom_hi);
/* jump to next tag if it does not match */
bpf_jmp(ins, &i, BPF_JMP|BPF_JEQ|BPF_K, tag_bloom_hi, 0, 3);
/* load device bloom bits in A */
bpf_stmt(ins, &i, BPF_LD|BPF_W|BPF_ABS, offsetof(struct udev_monitor_netlink_header, filter_tag_bloom_lo));
/* clear bits (tag bits & bloom bits) */
bpf_stmt(ins, &i, BPF_ALU|BPF_AND|BPF_K, tag_bloom_lo);
/* jump behind end of tag match block if tag matches */
tag_matches--;
bpf_jmp(ins, &i, BPF_JMP|BPF_JEQ|BPF_K, tag_bloom_lo, 1 + (tag_matches * 6), 0);
}
/* nothing matched, drop packet */
bpf_stmt(ins, &i, BPF_RET|BPF_K, 0);
}
/* add all subsystem matches */
if (udev_list_get_entry(&udev_monitor->filter_subsystem_list) != NULL) {
udev_list_entry_foreach(list_entry, udev_list_get_entry(&udev_monitor->filter_subsystem_list)) {
unsigned int hash = util_string_hash32(udev_list_entry_get_name(list_entry));
/* load device subsystem value in A */
bpf_stmt(ins, &i, BPF_LD|BPF_W|BPF_ABS, offsetof(struct udev_monitor_netlink_header, filter_subsystem_hash));
if (udev_list_entry_get_value(list_entry) == NULL) {
/* jump if subsystem does not match */
bpf_jmp(ins, &i, BPF_JMP|BPF_JEQ|BPF_K, hash, 0, 1);
} else {
/* jump if subsystem does not match */
bpf_jmp(ins, &i, BPF_JMP|BPF_JEQ|BPF_K, hash, 0, 3);
/* load device devtype value in A */
bpf_stmt(ins, &i, BPF_LD|BPF_W|BPF_ABS, offsetof(struct udev_monitor_netlink_header, filter_devtype_hash));
/* jump if value does not match */
hash = util_string_hash32(udev_list_entry_get_value(list_entry));
bpf_jmp(ins, &i, BPF_JMP|BPF_JEQ|BPF_K, hash, 0, 1);
}
/* matched, pass packet */
bpf_stmt(ins, &i, BPF_RET|BPF_K, 0xffffffff);
if (i+1 >= ELEMENTSOF(ins))
return -E2BIG;
}
/* nothing matched, drop packet */
bpf_stmt(ins, &i, BPF_RET|BPF_K, 0);
}
/* matched, pass packet */
bpf_stmt(ins, &i, BPF_RET|BPF_K, 0xffffffff);
/* install filter */
memzero(&filter, sizeof(filter));
filter.len = i;
filter.filter = ins;
err = setsockopt(udev_monitor->sock, SOL_SOCKET, SO_ATTACH_FILTER, &filter, sizeof(filter));
return err < 0 ? -errno : 0;
}
int udev_monitor_allow_unicast_sender(struct udev_monitor *udev_monitor, struct udev_monitor *sender)
{
udev_monitor->snl_trusted_sender.nl.nl_pid = sender->snl.nl.nl_pid;
return 0;
}
/**
* udev_monitor_enable_receiving:
* @udev_monitor: the monitor which should receive events
*
* Binds the @udev_monitor socket to the event source.
*
* Returns: 0 on success, otherwise a negative error value.
*/
_public_ int udev_monitor_enable_receiving(struct udev_monitor *udev_monitor)
{
int err = 0;
const int on = 1;
udev_monitor_filter_update(udev_monitor);
if (!udev_monitor->bound) {
err = bind(udev_monitor->sock,
&udev_monitor->snl.sa, sizeof(struct sockaddr_nl));
if (err == 0)
udev_monitor->bound = true;
}
if (err >= 0)
monitor_set_nl_address(udev_monitor);
else
return log_debug_errno(errno, "bind failed: %m");
/* enable receiving of sender credentials */
err = setsockopt(udev_monitor->sock, SOL_SOCKET, SO_PASSCRED, &on, sizeof(on));
if (err < 0)
log_debug_errno(errno, "setting SO_PASSCRED failed: %m");
return 0;
}
/**
* udev_monitor_set_receive_buffer_size:
* @udev_monitor: the monitor which should receive events
* @size: the size in bytes
*
* Set the size of the kernel socket buffer. This call needs the
* appropriate privileges to succeed.
*
* Returns: 0 on success, otherwise -1 on error.
*/
_public_ int udev_monitor_set_receive_buffer_size(struct udev_monitor *udev_monitor, int size)
{
if (udev_monitor == NULL)
return -EINVAL;
return setsockopt(udev_monitor->sock, SOL_SOCKET, SO_RCVBUFFORCE, &size, sizeof(size));
}
int udev_monitor_disconnect(struct udev_monitor *udev_monitor)
{
int err;
err = close(udev_monitor->sock);
udev_monitor->sock = -1;
return err < 0 ? -errno : 0;
}
/**
* udev_monitor_ref:
* @udev_monitor: udev monitor
*
* Take a reference of a udev monitor.
*
* Returns: the passed udev monitor
**/
_public_ struct udev_monitor *udev_monitor_ref(struct udev_monitor *udev_monitor)
{
if (udev_monitor == NULL)
return NULL;
udev_monitor->refcount++;
return udev_monitor;
}
/**
* udev_monitor_unref:
* @udev_monitor: udev monitor
*
* Drop a reference of a udev monitor. If the refcount reaches zero,
* the bound socket will be closed, and the resources of the monitor
* will be released.
*
* Returns: #NULL
**/
_public_ struct udev_monitor *udev_monitor_unref(struct udev_monitor *udev_monitor)
{
if (udev_monitor == NULL)
return NULL;
udev_monitor->refcount--;
if (udev_monitor->refcount > 0)
return NULL;
if (udev_monitor->sock >= 0)
close(udev_monitor->sock);
udev_list_cleanup(&udev_monitor->filter_subsystem_list);
udev_list_cleanup(&udev_monitor->filter_tag_list);
free(udev_monitor);
return NULL;
}
/**
* udev_monitor_get_udev:
* @udev_monitor: udev monitor
*
* Retrieve the udev library context the monitor was created with.
*
* Returns: the udev library context
**/
_public_ struct udev *udev_monitor_get_udev(struct udev_monitor *udev_monitor)
{
if (udev_monitor == NULL)
return NULL;
return udev_monitor->udev;
}
/**
* udev_monitor_get_fd:
* @udev_monitor: udev monitor
*
* Retrieve the socket file descriptor associated with the monitor.
*
* Returns: the socket file descriptor
**/
_public_ int udev_monitor_get_fd(struct udev_monitor *udev_monitor)
{
if (udev_monitor == NULL)
return -EINVAL;
return udev_monitor->sock;
}
static int passes_filter(struct udev_monitor *udev_monitor, struct udev_device *udev_device)
{
struct udev_list_entry *list_entry;
if (udev_list_get_entry(&udev_monitor->filter_subsystem_list) == NULL)
goto tag;
udev_list_entry_foreach(list_entry, udev_list_get_entry(&udev_monitor->filter_subsystem_list)) {
const char *subsys = udev_list_entry_get_name(list_entry);
const char *dsubsys = udev_device_get_subsystem(udev_device);
const char *devtype;
const char *ddevtype;
if (!streq(dsubsys, subsys))
continue;
devtype = udev_list_entry_get_value(list_entry);
if (devtype == NULL)
goto tag;
ddevtype = udev_device_get_devtype(udev_device);
if (ddevtype == NULL)
continue;
if (streq(ddevtype, devtype))
goto tag;
}
return 0;
tag:
if (udev_list_get_entry(&udev_monitor->filter_tag_list) == NULL)
return 1;
udev_list_entry_foreach(list_entry, udev_list_get_entry(&udev_monitor->filter_tag_list)) {
const char *tag = udev_list_entry_get_name(list_entry);
if (udev_device_has_tag(udev_device, tag))
return 1;
}
return 0;
}
/**
* udev_monitor_receive_device:
* @udev_monitor: udev monitor
*
* Receive data from the udev monitor socket, allocate a new udev
* device, fill in the received data, and return the device.
*
* Only socket connections with uid=0 are accepted.
*
* The monitor socket is by default set to NONBLOCK. A variant of poll() on
* the file descriptor returned by udev_monitor_get_fd() should to be used to
* wake up when new devices arrive, or alternatively the file descriptor
* switched into blocking mode.
*
* The initial refcount is 1, and needs to be decremented to
* release the resources of the udev device.
*
* Returns: a new udev device, or #NULL, in case of an error
**/
_public_ struct udev_device *udev_monitor_receive_device(struct udev_monitor *udev_monitor)
{
struct udev_device *udev_device;
struct msghdr smsg;
struct iovec iov;
char cred_msg[CMSG_SPACE(sizeof(struct ucred))];
struct cmsghdr *cmsg;
union sockaddr_union snl;
struct ucred *cred;
union {
struct udev_monitor_netlink_header nlh;
char raw[8192];
} buf;
ssize_t buflen;
ssize_t bufpos;
bool is_initialized = false;
retry:
if (udev_monitor == NULL)
return NULL;
iov.iov_base = &buf;
iov.iov_len = sizeof(buf);
memzero(&smsg, sizeof(struct msghdr));
smsg.msg_iov = &iov;
smsg.msg_iovlen = 1;
smsg.msg_control = cred_msg;
smsg.msg_controllen = sizeof(cred_msg);
smsg.msg_name = &snl;
smsg.msg_namelen = sizeof(snl);
buflen = recvmsg(udev_monitor->sock, &smsg, 0);
if (buflen < 0) {
if (errno != EINTR)
log_debug("unable to receive message");
return NULL;
}
if (buflen < 32 || (smsg.msg_flags & MSG_TRUNC)) {
log_debug("invalid message length");
return NULL;
}
if (snl.nl.nl_groups == 0) {
/* unicast message, check if we trust the sender */
if (udev_monitor->snl_trusted_sender.nl.nl_pid == 0 ||
snl.nl.nl_pid != udev_monitor->snl_trusted_sender.nl.nl_pid) {
log_debug("unicast netlink message ignored");
return NULL;
}
} else if (snl.nl.nl_groups == UDEV_MONITOR_KERNEL) {
if (snl.nl.nl_pid > 0) {
log_debug("multicast kernel netlink message from PID %"PRIu32" ignored",
snl.nl.nl_pid);
return NULL;
}
}
cmsg = CMSG_FIRSTHDR(&smsg);
if (cmsg == NULL || cmsg->cmsg_type != SCM_CREDENTIALS) {
log_debug("no sender credentials received, message ignored");
return NULL;
}
cred = (struct ucred *)CMSG_DATA(cmsg);
if (cred->uid != 0) {
log_debug("sender uid="UID_FMT", message ignored", cred->uid);
return NULL;
}
if (memcmp(buf.raw, "libudev", 8) == 0) {
/* udev message needs proper version magic */
if (buf.nlh.magic != htonl(UDEV_MONITOR_MAGIC)) {
log_debug("unrecognized message signature (%x != %x)",
buf.nlh.magic, htonl(UDEV_MONITOR_MAGIC));
return NULL;
}
if (buf.nlh.properties_off+32 > (size_t)buflen) {
log_debug("message smaller than expected (%u > %zd)",
buf.nlh.properties_off+32, buflen);
return NULL;
}
bufpos = buf.nlh.properties_off;
/* devices received from udev are always initialized */
is_initialized = true;
} else {
/* kernel message with header */
bufpos = strlen(buf.raw) + 1;
if ((size_t)bufpos < sizeof("a@/d") || bufpos >= buflen) {
log_debug("invalid message length");
return NULL;
}
/* check message header */
if (strstr(buf.raw, "@/") == NULL) {
log_debug("unrecognized message header");
return NULL;
}
}
udev_device = udev_device_new_from_nulstr(udev_monitor->udev, &buf.raw[bufpos], buflen - bufpos);
if (!udev_device) {
log_debug("could not create device: %m");
return NULL;
}
if (is_initialized)
udev_device_set_is_initialized(udev_device);
/* skip device, if it does not pass the current filter */
if (!passes_filter(udev_monitor, udev_device)) {
struct pollfd pfd[1];
int rc;
udev_device_unref(udev_device);
/* if something is queued, get next device */
pfd[0].fd = udev_monitor->sock;
pfd[0].events = POLLIN;
rc = poll(pfd, 1, 0);
if (rc > 0)
goto retry;
return NULL;
}
return udev_device;
}
int udev_monitor_send_device(struct udev_monitor *udev_monitor,
struct udev_monitor *destination, struct udev_device *udev_device)
{
const char *buf, *val;
ssize_t blen, count;
struct udev_monitor_netlink_header nlh = {
.prefix = "libudev",
.magic = htonl(UDEV_MONITOR_MAGIC),
.header_size = sizeof nlh,
};
struct iovec iov[2] = {
{ .iov_base = &nlh, .iov_len = sizeof nlh },
};
struct msghdr smsg = {
.msg_iov = iov,
.msg_iovlen = 2,
};
struct udev_list_entry *list_entry;
uint64_t tag_bloom_bits;
blen = udev_device_get_properties_monitor_buf(udev_device, &buf);
if (blen < 32) {
log_debug("device buffer is too small to contain a valid device");
return -EINVAL;
}
/* fill in versioned header */
val = udev_device_get_subsystem(udev_device);
nlh.filter_subsystem_hash = htonl(util_string_hash32(val));
val = udev_device_get_devtype(udev_device);
if (val != NULL)
nlh.filter_devtype_hash = htonl(util_string_hash32(val));
/* add tag bloom filter */
tag_bloom_bits = 0;
udev_list_entry_foreach(list_entry, udev_device_get_tags_list_entry(udev_device))
tag_bloom_bits |= util_string_bloom64(udev_list_entry_get_name(list_entry));
if (tag_bloom_bits > 0) {
nlh.filter_tag_bloom_hi = htonl(tag_bloom_bits >> 32);
nlh.filter_tag_bloom_lo = htonl(tag_bloom_bits & 0xffffffff);
}
/* add properties list */
nlh.properties_off = iov[0].iov_len;
nlh.properties_len = blen;
iov[1].iov_base = (char *)buf;
iov[1].iov_len = blen;
/*
* Use custom address for target, or the default one.
*
* If we send to a multicast group, we will get
* ECONNREFUSED, which is expected.
*/
if (destination)
smsg.msg_name = &destination->snl;
else
smsg.msg_name = &udev_monitor->snl_destination;
smsg.msg_namelen = sizeof(struct sockaddr_nl);
count = sendmsg(udev_monitor->sock, &smsg, 0);
if (count < 0) {
if (!destination && errno == ECONNREFUSED) {
log_debug("passed device to netlink monitor %p", udev_monitor);
return 0;
} else
return -errno;
}
log_debug("passed %zi byte device to netlink monitor %p", count, udev_monitor);
return count;
}
/**
* udev_monitor_filter_add_match_subsystem_devtype:
* @udev_monitor: the monitor
* @subsystem: the subsystem value to match the incoming devices against
* @devtype: the devtype value to match the incoming devices against
*
* This filter is efficiently executed inside the kernel, and libudev subscribers
* will usually not be woken up for devices which do not match.
*
* The filter must be installed before the monitor is switched to listening mode.
*
* Returns: 0 on success, otherwise a negative error value.
*/
_public_ int udev_monitor_filter_add_match_subsystem_devtype(struct udev_monitor *udev_monitor, const char *subsystem, const char *devtype)
{
if (udev_monitor == NULL)
return -EINVAL;
if (subsystem == NULL)
return -EINVAL;
if (udev_list_entry_add(&udev_monitor->filter_subsystem_list, subsystem, devtype) == NULL)
return -ENOMEM;
return 0;
}
/**
* udev_monitor_filter_add_match_tag:
* @udev_monitor: the monitor
* @tag: the name of a tag
*
* This filter is efficiently executed inside the kernel, and libudev subscribers
* will usually not be woken up for devices which do not match.
*
* The filter must be installed before the monitor is switched to listening mode.
*
* Returns: 0 on success, otherwise a negative error value.
*/
_public_ int udev_monitor_filter_add_match_tag(struct udev_monitor *udev_monitor, const char *tag)
{
if (udev_monitor == NULL)
return -EINVAL;
if (tag == NULL)
return -EINVAL;
if (udev_list_entry_add(&udev_monitor->filter_tag_list, tag, NULL) == NULL)
return -ENOMEM;
return 0;
}
/**
* udev_monitor_filter_remove:
* @udev_monitor: monitor
*
* Remove all filters from monitor.
*
* Returns: 0 on success, otherwise a negative error value.
*/
_public_ int udev_monitor_filter_remove(struct udev_monitor *udev_monitor)
{
static struct sock_fprog filter = { 0, NULL };
udev_list_cleanup(&udev_monitor->filter_subsystem_list);
return setsockopt(udev_monitor->sock, SOL_SOCKET, SO_ATTACH_FILTER, &filter, sizeof(filter));
}