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Systemd/src/libudev/libudev-monitor.c

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/* SPDX-License-Identifier: LGPL-2.1+ */
#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 "libudev.h"
#include "alloc-util.h"
#include "device-private.h"
#include "device-util.h"
#include "fd-util.h"
#include "fileio.h"
#include "format-util.h"
#include "hashmap.h"
#include "libudev-device-internal.h"
#include "libudev-private.h"
#include "missing.h"
#include "mount-util.h"
#include "set.h"
#include "socket-util.h"
#include "string-util.h"
#include "strv.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;
unsigned n_ref;
int sock;
union sockaddr_union snl;
union sockaddr_union snl_trusted_sender;
union sockaddr_union snl_destination;
socklen_t addrlen;
Hashmap *subsystem_filter;
Set *tag_filter;
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 magic;
/* total length of header structure known to the sender */
unsigned header_size;
/* properties string buffer */
unsigned properties_off;
unsigned 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 filter_subsystem_hash;
unsigned filter_devtype_hash;
unsigned filter_tag_bloom_hi;
unsigned filter_tag_bloom_lo;
};
static int udev_monitor_set_nl_address(struct udev_monitor *udev_monitor) {
union sockaddr_union snl;
socklen_t addrlen;
assert(udev_monitor);
/* Get the address the kernel has assigned us.
* It is usually, but not necessarily the pid. */
addrlen = sizeof(struct sockaddr_nl);
if (getsockname(udev_monitor->sock, &snl.sa, &addrlen) < 0)
return -errno;
udev_monitor->snl.nl.nl_pid = snl.nl.nl_pid;
return 0;
}
struct udev_monitor *udev_monitor_new_from_netlink_fd(struct udev *udev, const char *name, int fd) {
_cleanup_(udev_monitor_unrefp) struct udev_monitor *udev_monitor = NULL;
_cleanup_close_ int sock = -1;
unsigned group;
int r;
assert_return_errno(!name || STR_IN_SET(name, "udev", "kernel"), NULL, EINVAL);
if (!name)
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 && dev_is_devtmpfs() <= 0) {
log_debug("The udev service seems not to be active, disabling the monitor");
group = UDEV_MONITOR_NONE;
} else
group = UDEV_MONITOR_UDEV;
} else {
assert(streq(name, "kernel"));
group = UDEV_MONITOR_KERNEL;
}
if (fd < 0) {
sock = socket(PF_NETLINK, SOCK_RAW|SOCK_CLOEXEC|SOCK_NONBLOCK, NETLINK_KOBJECT_UEVENT);
if (sock < 0) {
log_debug_errno(errno, "Failed to create socket: %m");
return NULL;
}
}
udev_monitor = new(struct udev_monitor, 1);
if (!udev_monitor) {
errno = ENOMEM;
return NULL;
}
*udev_monitor = (struct udev_monitor) {
.udev = udev,
.n_ref = 1,
.sock = fd >= 0 ? fd : TAKE_FD(sock),
.bound = fd >= 0,
.snl.nl.nl_family = AF_NETLINK,
.snl.nl.nl_groups = group,
/* default destination for sending */
.snl_destination.nl.nl_family = AF_NETLINK,
.snl_destination.nl.nl_groups = UDEV_MONITOR_UDEV,
};
if (fd >= 0) {
r = udev_monitor_set_nl_address(udev_monitor);
if (r < 0) {
log_debug_errno(r, "Failed to set netlink address: %m");
return NULL;
}
}
return TAKE_PTR(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 void bpf_stmt(struct sock_filter *ins, unsigned *i,
unsigned short code, unsigned data) {
ins[(*i)++] = (struct sock_filter) {
.code = code,
.k = data,
};
}
static void bpf_jmp(struct sock_filter *ins, unsigned *i,
unsigned short code, unsigned data,
unsigned short jt, unsigned short jf) {
ins[(*i)++] = (struct sock_filter) {
.code = code,
.jt = jt,
.jf = jf,
.k = data,
};
}
/**
* 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;
const char *subsystem, *devtype, *tag;
unsigned i = 0;
Iterator it;
assert_return(udev_monitor, -EINVAL);
if (hashmap_isempty(udev_monitor->subsystem_filter) &&
set_isempty(udev_monitor->tag_filter))
return 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 (!set_isempty(udev_monitor->tag_filter)) {
int tag_matches = set_size(udev_monitor->tag_filter);
/* add all tags matches */
SET_FOREACH(tag, udev_monitor->tag_filter, it) {
uint64_t tag_bloom_bits = util_string_bloom64(tag);
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 (!hashmap_isempty(udev_monitor->subsystem_filter)) {
HASHMAP_FOREACH_KEY(devtype, subsystem, udev_monitor->subsystem_filter, it) {
uint32_t hash = util_string_hash32(subsystem);
/* 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 (!devtype) {
/* jump if subsystem does not match */
bpf_jmp(ins, &i, BPF_JMP|BPF_JEQ|BPF_K, hash, 0, 1);
} else {
hash = util_string_hash32(devtype);
/* 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 */
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 */
filter = (struct sock_fprog) {
.len = i,
.filter = ins,
};
if (setsockopt(udev_monitor->sock, SOL_SOCKET, SO_ATTACH_FILTER, &filter, sizeof(filter)) < 0)
return -errno;
return 0;
}
int udev_monitor_allow_unicast_sender(struct udev_monitor *udev_monitor, struct udev_monitor *sender) {
assert_return(udev_monitor, -EINVAL);
assert_return(sender, -EINVAL);
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) {
const int on = 1;
int r;
assert_return(udev_monitor, -EINVAL);
r = udev_monitor_filter_update(udev_monitor);
if (r < 0)
return log_debug_errno(r, "Failed to update filter: %m");
if (!udev_monitor->bound) {
if (bind(udev_monitor->sock, &udev_monitor->snl.sa, sizeof(struct sockaddr_nl)) < 0)
return log_debug_errno(errno, "Failed to bind udev monitor socket to event source: %m");
udev_monitor->bound = true;
}
r = udev_monitor_set_nl_address(udev_monitor);
if (r < 0)
return log_debug_errno(r, "Failed to set address: %m");
/* enable receiving of sender credentials */
if (setsockopt(udev_monitor->sock, SOL_SOCKET, SO_PASSCRED, &on, sizeof(on)) < 0)
return log_debug_errno(errno, "Failed to set socket option SO_PASSCRED: %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) {
assert_return(udev_monitor, -EINVAL);
if (setsockopt(udev_monitor->sock, SOL_SOCKET, SO_RCVBUFFORCE, &size, sizeof(size)) < 0)
return -errno;
return 0;
}
int udev_monitor_disconnect(struct udev_monitor *udev_monitor) {
assert(udev_monitor);
udev_monitor->sock = safe_close(udev_monitor->sock);
return 0;
}
static struct udev_monitor *udev_monitor_free(struct udev_monitor *udev_monitor) {
assert(udev_monitor);
udev_monitor_disconnect(udev_monitor);
hashmap_free_free_free(udev_monitor->subsystem_filter);
set_free_free(udev_monitor->tag_filter);
return mfree(udev_monitor);
}
/**
* udev_monitor_ref:
* @udev_monitor: udev monitor
*
* Take a reference of a udev monitor.
*
* Returns: the passed 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
**/
DEFINE_PUBLIC_TRIVIAL_REF_UNREF_FUNC(struct udev_monitor, udev_monitor, udev_monitor_free);
/**
* 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) {
assert_return(udev_monitor, 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) {
assert_return(udev_monitor, -EINVAL);
return udev_monitor->sock;
}
static int passes_filter(struct udev_monitor *udev_monitor, sd_device *device) {
const char *tag, *subsystem, *devtype, *s, *d = NULL;
Iterator i;
int r;
assert_return(udev_monitor, -EINVAL);
assert_return(device, -EINVAL);
if (hashmap_isempty(udev_monitor->subsystem_filter))
goto tag;
r = sd_device_get_subsystem(device, &s);
if (r < 0)
return r;
r = sd_device_get_devtype(device, &d);
if (r < 0 && r != -ENOENT)
return r;
HASHMAP_FOREACH_KEY(devtype, subsystem, udev_monitor->subsystem_filter, i) {
if (!streq(s, subsystem))
continue;
if (!devtype)
goto tag;
if (!d)
continue;
if (streq(d, devtype))
goto tag;
}
return 0;
tag:
if (set_isempty(udev_monitor->tag_filter))
return 1;
SET_FOREACH(tag, udev_monitor->tag_filter, i)
if (sd_device_has_tag(device, tag) > 0)
return 1;
return 0;
}
static int udev_monitor_receive_device_one(struct udev_monitor *udev_monitor, sd_device **ret) {
_cleanup_(sd_device_unrefp) sd_device *device = NULL;
union {
struct udev_monitor_netlink_header nlh;
char raw[8192];
} buf;
struct iovec iov = {
.iov_base = &buf,
.iov_len = sizeof(buf)
};
char cred_msg[CMSG_SPACE(sizeof(struct ucred))];
union sockaddr_union snl;
struct msghdr smsg = {
.msg_iov = &iov,
.msg_iovlen = 1,
.msg_control = cred_msg,
.msg_controllen = sizeof(cred_msg),
.msg_name = &snl,
.msg_namelen = sizeof(snl),
};
struct cmsghdr *cmsg;
struct ucred *cred;
ssize_t buflen, bufpos;
bool is_initialized = false;
int r;
assert(ret);
buflen = recvmsg(udev_monitor->sock, &smsg, 0);
if (buflen < 0) {
if (errno != EINTR)
log_debug_errno(errno, "Failed to receive message: %m");
return -errno;
}
if (buflen < 32 || (smsg.msg_flags & MSG_TRUNC))
return log_debug_errno(EINVAL, "Invalid message length.");
if (snl.nl.nl_groups == UDEV_MONITOR_NONE) {
/* 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)
return log_debug_errno(EAGAIN, "Unicast netlink message ignored.");
} else if (snl.nl.nl_groups == UDEV_MONITOR_KERNEL) {
if (snl.nl.nl_pid > 0)
return log_debug_errno(EAGAIN, "Multicast kernel netlink message from PID %"PRIu32" ignored.", snl.nl.nl_pid);
}
cmsg = CMSG_FIRSTHDR(&smsg);
if (!cmsg || cmsg->cmsg_type != SCM_CREDENTIALS)
return log_debug_errno(EAGAIN, "No sender credentials received, message ignored.");
cred = (struct ucred*) CMSG_DATA(cmsg);
if (cred->uid != 0)
return log_debug_errno(EAGAIN, "Sender uid="UID_FMT", message ignored.", cred->uid);
if (streq(buf.raw, "libudev")) {
/* udev message needs proper version magic */
if (buf.nlh.magic != htobe32(UDEV_MONITOR_MAGIC))
return log_debug_errno(EAGAIN, "Invalid message signature (%x != %x)",
buf.nlh.magic, htobe32(UDEV_MONITOR_MAGIC));
if (buf.nlh.properties_off+32 > (size_t) buflen)
return log_debug_errno(EAGAIN, "Invalid message length (%u > %zd)",
buf.nlh.properties_off+32, buflen);
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)
return log_debug_errno(EAGAIN, "Invalid message length");
/* check message header */
if (!strstr(buf.raw, "@/"))
return log_debug_errno(EAGAIN, "Invalid message header");
}
r = device_new_from_nulstr(&device, (uint8_t*) &buf.raw[bufpos], buflen - bufpos);
if (r < 0)
return log_debug_errno(r, "Failed to create device: %m");
if (is_initialized)
device_set_is_initialized(device);
/* skip device, if it does not pass the current filter */
if (passes_filter(udev_monitor, device) <= 0)
return 0;
*ret = TAKE_PTR(device);
return 1;
}
int udev_monitor_receive_sd_device(struct udev_monitor *udev_monitor, sd_device **ret) {
struct pollfd pfd = {
.fd = udev_monitor->sock,
.events = POLLIN,
};
int r;
assert(udev_monitor);
assert(ret);
for (;;) {
/* r == 0 means a device is received but it does not pass the current filter. */
r = udev_monitor_receive_device_one(udev_monitor, ret);
if (r != 0)
return r;
for (;;) {
/* wait next message */
r = poll(&pfd, 1, 0);
if (r < 0) {
if (IN_SET(errno, EINTR, EAGAIN))
continue;
return -errno;
} else if (r == 0)
return -EAGAIN;
/* receive next message */
break;
}
}
}
/**
* 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) {
_cleanup_(sd_device_unrefp) sd_device *device = NULL;
int r;
assert_return(udev_monitor, NULL);
r = udev_monitor_receive_sd_device(udev_monitor, &device);
if (r < 0) {
errno = -r;
return NULL;
}
return udev_device_new(udev_monitor->udev, device);
}
static int udev_monitor_send_sd_device(
struct udev_monitor *udev_monitor,
struct udev_monitor *destination,
sd_device *device) {
struct udev_monitor_netlink_header nlh = {
.prefix = "libudev",
.magic = htobe32(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,
};
uint64_t tag_bloom_bits;
const char *buf, *val;
ssize_t count;
size_t blen;
int r;
assert(udev_monitor);
assert(device);
r = device_get_properties_nulstr(device, (const uint8_t **) &buf, &blen);
if (r < 0)
return log_debug_errno(r, "Failed to get device properties: %m");
if (blen < 32) {
log_debug("Device buffer is too small to contain a valid device");
return -EINVAL;
}
/* fill in versioned header */
r = sd_device_get_subsystem(device, &val);
if (r < 0)
return log_debug_errno(r, "Failed to get device subsystem: %m");
nlh.filter_subsystem_hash = htobe32(util_string_hash32(val));
if (sd_device_get_devtype(device, &val) >= 0 && val)
nlh.filter_devtype_hash = htobe32(util_string_hash32(val));
/* add tag bloom filter */
tag_bloom_bits = 0;
FOREACH_DEVICE_TAG(device, val)
tag_bloom_bits |= util_string_bloom64(val);
if (tag_bloom_bits > 0) {
nlh.filter_tag_bloom_hi = htobe32(tag_bloom_bits >> 32);
nlh.filter_tag_bloom_lo = htobe32(tag_bloom_bits & 0xffffffff);
}
/* add properties list */
nlh.properties_off = iov[0].iov_len;
nlh.properties_len = blen;
iov[1] = (struct iovec) {
.iov_base = (char*) buf,
.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.
*/
smsg.msg_name = destination ? &destination->snl : &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 log_debug_errno(errno, "Failed to send device to netlink monitor %p", udev_monitor);
}
log_debug("Passed %zi byte device to netlink monitor %p", count, udev_monitor);
return count;
}
int udev_monitor_send_device(
struct udev_monitor *udev_monitor,
struct udev_monitor *destination,
struct udev_device *udev_device) {
assert(udev_device);
return udev_monitor_send_sd_device(udev_monitor, destination, udev_device->device);
}
/**
* 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) {
_cleanup_free_ char *s = NULL, *d = NULL;
int r;
assert_return(udev_monitor, -EINVAL);
assert_return(subsystem, -EINVAL);
s = strdup(subsystem);
if (!s)
return -ENOMEM;
if (devtype) {
d = strdup(devtype);
if (!d)
return -ENOMEM;
}
r = hashmap_ensure_allocated(&udev_monitor->subsystem_filter, NULL);
if (r < 0)
return r;
r = hashmap_put(udev_monitor->subsystem_filter, s, d);
if (r < 0)
return r;
s = d = NULL;
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) {
_cleanup_free_ char *t = NULL;
int r;
assert_return(udev_monitor, -EINVAL);
assert_return(tag, -EINVAL);
t = strdup(tag);
if (!t)
return -ENOMEM;
r = set_ensure_allocated(&udev_monitor->tag_filter, &string_hash_ops);
if (r < 0)
return r;
r = set_put(udev_monitor->tag_filter, t);
if (r == -EEXIST)
return 0;
if (r < 0)
return r;
TAKE_PTR(t);
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 const struct sock_fprog filter = { 0, NULL };
assert_return(udev_monitor, -EINVAL);
udev_monitor->subsystem_filter = hashmap_free_free_free(udev_monitor->subsystem_filter);
udev_monitor->tag_filter = set_free_free(udev_monitor->tag_filter);
if (setsockopt(udev_monitor->sock, SOL_SOCKET, SO_ATTACH_FILTER, &filter, sizeof(filter)) < 0)
return -errno;
return 0;
}
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