/*** 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 <stdio.h> #include <stdlib.h> #include <stddef.h> #include <unistd.h> #include <errno.h> #include <string.h> #include <dirent.h> #include <sys/poll.h> #include <sys/stat.h> #include <sys/socket.h> #include <sys/un.h> #include <arpa/inet.h> #include <linux/netlink.h> #include <linux/filter.h> #include "libudev.h" #include "libudev-private.h" #include "socket-util.h" #include "missing.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 = { .handle.handle_bytes = MAX_HANDLE_SZ }; _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) udev_err(udev, "name_to_handle_at on /dev: %m\n"); 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; } 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)) { udev_dbg(udev, "the udev service seems not to be active, disable the monitor\n"); 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 == -1) { udev_err(udev, "error getting socket: %m\n"); free(udev_monitor); return NULL; } } else { udev_monitor->bound = true; udev_monitor->sock = fd; } 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) { union sockaddr_union snl; socklen_t addrlen; /* * get the address the kernel has assigned us * it is usually, but not necessarily the pid */ addrlen = sizeof(struct sockaddr_nl); err = getsockname(udev_monitor->sock, &snl.sa, &addrlen); if (err == 0) udev_monitor->snl.nl.nl_pid = snl.nl.nl_pid; } else { udev_err(udev_monitor->udev, "bind failed: %m\n"); return -errno; } /* enable receiving of sender credentials */ setsockopt(udev_monitor->sock, SOL_SOCKET, SO_PASSCRED, &on, sizeof(on)); 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; char buf[8192]; ssize_t buflen; ssize_t bufpos; 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) udev_dbg(udev_monitor->udev, "unable to receive message\n"); return NULL; } if (buflen < 32 || (size_t)buflen >= sizeof(buf)) { udev_dbg(udev_monitor->udev, "invalid message length\n"); 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) { udev_dbg(udev_monitor->udev, "unicast netlink message ignored\n"); return NULL; } } else if (snl.nl.nl_groups == UDEV_MONITOR_KERNEL) { if (snl.nl.nl_pid > 0) { udev_dbg(udev_monitor->udev, "multicast kernel netlink message from pid %d ignored\n", snl.nl.nl_pid); return NULL; } } cmsg = CMSG_FIRSTHDR(&smsg); if (cmsg == NULL || cmsg->cmsg_type != SCM_CREDENTIALS) { udev_dbg(udev_monitor->udev, "no sender credentials received, message ignored\n"); return NULL; } cred = (struct ucred *)CMSG_DATA(cmsg); if (cred->uid != 0) { udev_dbg(udev_monitor->udev, "sender uid=%d, message ignored\n", cred->uid); return NULL; } udev_device = udev_device_new(udev_monitor->udev); if (udev_device == NULL) return NULL; if (memcmp(buf, "libudev", 8) == 0) { struct udev_monitor_netlink_header *nlh; /* udev message needs proper version magic */ nlh = (struct udev_monitor_netlink_header *) buf; if (nlh->magic != htonl(UDEV_MONITOR_MAGIC)) { udev_err(udev_monitor->udev, "unrecognized message signature (%x != %x)\n", nlh->magic, htonl(UDEV_MONITOR_MAGIC)); udev_device_unref(udev_device); return NULL; } if (nlh->properties_off+32 > (size_t)buflen) { udev_device_unref(udev_device); return NULL; } bufpos = nlh->properties_off; /* devices received from udev are always initialized */ udev_device_set_is_initialized(udev_device); } else { /* kernel message with header */ bufpos = strlen(buf) + 1; if ((size_t)bufpos < sizeof("a@/d") || bufpos >= buflen) { udev_dbg(udev_monitor->udev, "invalid message length\n"); udev_device_unref(udev_device); return NULL; } /* check message header */ if (strstr(buf, "@/") == NULL) { udev_dbg(udev_monitor->udev, "unrecognized message header\n"); udev_device_unref(udev_device); return NULL; } } udev_device_set_info_loaded(udev_device); while (bufpos < buflen) { char *key; size_t keylen; key = &buf[bufpos]; keylen = strlen(key); if (keylen == 0) break; bufpos += keylen + 1; udev_device_add_property_from_string_parse(udev_device, key); } if (udev_device_add_property_from_string_parse_finish(udev_device) < 0) { udev_dbg(udev_monitor->udev, "missing values, invalid device\n"); udev_device_unref(udev_device); return NULL; } /* 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; ssize_t blen; ssize_t count; struct msghdr smsg; struct iovec iov[2]; const char *val; struct udev_monitor_netlink_header nlh; struct udev_list_entry *list_entry; uint64_t tag_bloom_bits; blen = udev_device_get_properties_monitor_buf(udev_device, &buf); if (blen < 32) return -EINVAL; /* add versioned header */ memzero(&nlh, sizeof(struct udev_monitor_netlink_header)); memcpy(nlh.prefix, "libudev", 8); nlh.magic = htonl(UDEV_MONITOR_MAGIC); nlh.header_size = sizeof(struct udev_monitor_netlink_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)); iov[0].iov_base = &nlh; iov[0].iov_len = sizeof(struct udev_monitor_netlink_header); /* 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; memzero(&smsg, sizeof(struct msghdr)); smsg.msg_iov = iov; smsg.msg_iovlen = 2; /* * 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 != NULL) 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); udev_dbg(udev_monitor->udev, "passed %zi bytes to netlink monitor %p\n", 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)); }