/* * libudev - interface to udev device information * * Copyright (C) 2008-2009 Kay Sievers * * This library 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. */ #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include "libudev.h" #include "libudev-private.h" /** * SECTION:libudev-monitor * @short_description: device event source * * Connects to a device event source. */ /** * udev_monitor: * * Opaque object handling one event source. */ struct udev_monitor { struct udev *udev; int refcount; int sock; struct sockaddr_nl snl; struct sockaddr_nl snl_trusted_sender; struct sockaddr_nl snl_destination; struct sockaddr_un sun; socklen_t addrlen; struct udev_list_node filter_subsystem_list; }; enum udev_monitor_netlink_group { UDEV_MONITOR_NONE, UDEV_MONITOR_KERNEL, UDEV_MONITOR_UDEV, }; #define UDEV_MONITOR_MAGIC 0xcafe1dea struct udev_monitor_netlink_header { /* udev version text */ char version[16]; /* * 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; /* properties buffer */ unsigned short properties_off; unsigned short properties_len; /* * hashes of some common device properties strings to filter with socket filters in * the client used in the kernel from socket filter rules; needs to be stored in * network order */ unsigned int filter_subsystem; unsigned int filter_devtype; }; static struct udev_monitor *udev_monitor_new(struct udev *udev) { struct udev_monitor *udev_monitor; udev_monitor = calloc(1, sizeof(struct udev_monitor)); if (udev_monitor == NULL) return NULL; udev_monitor->refcount = 1; udev_monitor->udev = udev; udev_list_init(&udev_monitor->filter_subsystem_list); return udev_monitor; } /** * udev_monitor_new_from_socket: * @udev: udev library context * @socket_path: unix socket path * * Create new udev monitor and connect to a specified socket. The * path to a socket either points to an existing socket file, or if * the socket path starts with a '@' character, an abstract namespace * socket will be used. * * A socket file will not be created. If it does not already exist, * it will fall-back and connect to an abstract namespace socket with * the given path. The permissions adjustment of a socket file, as * well as the later cleanup, needs to be done by the caller. * * 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 **/ struct udev_monitor *udev_monitor_new_from_socket(struct udev *udev, const char *socket_path) { struct udev_monitor *udev_monitor; struct stat statbuf; if (udev == NULL) return NULL; if (socket_path == NULL) return NULL; udev_monitor = udev_monitor_new(udev); if (udev_monitor == NULL) return NULL; udev_monitor->sun.sun_family = AF_LOCAL; if (socket_path[0] == '@') { /* translate leading '@' to abstract namespace */ util_strscpy(udev_monitor->sun.sun_path, sizeof(udev_monitor->sun.sun_path), socket_path); udev_monitor->sun.sun_path[0] = '\0'; udev_monitor->addrlen = offsetof(struct sockaddr_un, sun_path) + strlen(socket_path); } else if (stat(socket_path, &statbuf) == 0 && S_ISSOCK(statbuf.st_mode)) { /* existing socket file */ util_strscpy(udev_monitor->sun.sun_path, sizeof(udev_monitor->sun.sun_path), socket_path); udev_monitor->addrlen = offsetof(struct sockaddr_un, sun_path) + strlen(socket_path); } else { /* no socket file, assume abstract namespace socket */ util_strscpy(&udev_monitor->sun.sun_path[1], sizeof(udev_monitor->sun.sun_path)-1, socket_path); udev_monitor->addrlen = offsetof(struct sockaddr_un, sun_path) + strlen(socket_path)+1; } udev_monitor->sock = socket(AF_LOCAL, SOCK_DGRAM|SOCK_CLOEXEC, 0); if (udev_monitor->sock == -1) { err(udev, "error getting socket: %m\n"); free(udev_monitor); return NULL; } dbg(udev, "monitor %p created with '%s'\n", udev_monitor, socket_path); 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 **/ struct udev_monitor *udev_monitor_new_from_netlink(struct udev *udev, const char *name) { struct udev_monitor *udev_monitor; unsigned int group; if (udev == NULL) return NULL; if (name == NULL) group = UDEV_MONITOR_NONE; else if (strcmp(name, "udev") == 0) group = UDEV_MONITOR_UDEV; else if (strcmp(name, "kernel") == 0) group = UDEV_MONITOR_KERNEL; else return NULL; udev_monitor = udev_monitor_new(udev); if (udev_monitor == NULL) return NULL; udev_monitor->sock = socket(PF_NETLINK, SOCK_DGRAM|SOCK_CLOEXEC, NETLINK_KOBJECT_UEVENT); if (udev_monitor->sock == -1) { err(udev, "error getting socket: %m\n"); free(udev_monitor); return NULL; } udev_monitor->snl.nl_family = AF_NETLINK; udev_monitor->snl.nl_groups = group; /* default destination for sending */ udev_monitor->snl_destination.nl_family = AF_NETLINK; udev_monitor->snl_destination.nl_groups = UDEV_MONITOR_UDEV; dbg(udev, "monitor %p created with NETLINK_KOBJECT_UEVENT (%u)\n", udev_monitor, group); return udev_monitor; } 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 filter. This might only be needed, if the filter was removed or changed. * * Returns: 0 on success, otherwise a negative error value. */ int udev_monitor_filter_update(struct udev_monitor *udev_monitor) { static struct sock_filter ins[256]; static 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) return 0; memset(ins, 0x00, 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); /* add all subsystem match values */ udev_list_entry_foreach(list_entry, udev_list_get_entry(&udev_monitor->filter_subsystem_list)) { unsigned int hash; /* load filter_subsystem value in A */ bpf_stmt(ins, &i, BPF_LD|BPF_W|BPF_ABS, offsetof(struct udev_monitor_netlink_header, filter_subsystem)); hash = util_string_hash32(udev_list_entry_get_name(list_entry)); 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 filter_devtype value in A */ bpf_stmt(ins, &i, BPF_LD|BPF_W|BPF_ABS, offsetof(struct udev_monitor_netlink_header, filter_devtype)); /* 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 >= ARRAY_SIZE(ins)) return -1; } /* nothing matched, drop packet */ bpf_stmt(ins, &i, BPF_RET|BPF_K, 0); /* install filter */ filter.len = i; filter.filter = ins; err = setsockopt(udev_monitor->sock, SOL_SOCKET, SO_ATTACH_FILTER, &filter, sizeof(filter)); return err; } int udev_monitor_allow_unicast_sender(struct udev_monitor *udev_monitor, struct udev_monitor *sender) { udev_monitor->snl_trusted_sender.nl_pid = sender->snl.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. */ int udev_monitor_enable_receiving(struct udev_monitor *udev_monitor) { int err; const int on = 1; if (udev_monitor->sun.sun_family != 0) { err = bind(udev_monitor->sock, (struct sockaddr *)&udev_monitor->sun, udev_monitor->addrlen); } else if (udev_monitor->snl.nl_family != 0) { udev_monitor_filter_update(udev_monitor); err = bind(udev_monitor->sock, (struct sockaddr *)&udev_monitor->snl, sizeof(struct sockaddr_nl)); if (err == 0) { struct sockaddr_nl 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, (struct sockaddr *)&snl, &addrlen); if (err == 0) udev_monitor->snl.nl_pid = snl.nl_pid; } } else { return -EINVAL; } if (err < 0) { err(udev_monitor->udev, "bind failed: %m\n"); return err; } /* enable receiving of sender credentials */ setsockopt(udev_monitor->sock, SOL_SOCKET, SO_PASSCRED, &on, sizeof(on)); return 0; } int udev_monitor_set_receive_buffer_size(struct udev_monitor *udev_monitor, int size) { if (udev_monitor == NULL) return -1; 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; } /** * udev_monitor_ref: * @udev_monitor: udev monitor * * Take a reference of a udev monitor. * * Returns: the passed udev monitor **/ 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. * **/ void udev_monitor_unref(struct udev_monitor *udev_monitor) { if (udev_monitor == NULL) return; udev_monitor->refcount--; if (udev_monitor->refcount > 0) return; if (udev_monitor->sock >= 0) close(udev_monitor->sock); udev_list_cleanup_entries(udev_monitor->udev, &udev_monitor->filter_subsystem_list); dbg(udev_monitor->udev, "monitor %p released\n", udev_monitor); free(udev_monitor); } /** * udev_monitor_get_udev: * @udev_monitor: udev monitor * * Retrieve the udev library context the monitor was created with. * * Returns: the udev library context **/ 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 **/ int udev_monitor_get_fd(struct udev_monitor *udev_monitor) { if (udev_monitor == NULL) return -1; 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) return 1; 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 (strcmp(dsubsys, subsys) != 0) continue; devtype = udev_list_entry_get_value(list_entry); if (devtype == NULL) return 1; ddevtype = udev_device_get_devtype(udev_device); if (ddevtype == NULL) continue; if (strcmp(ddevtype, devtype) == 0) 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 caller * needs to make sure that there is data to read from the socket. * The call will block until the socket becomes readable. * * 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 **/ 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; struct sockaddr_nl snl; struct ucred *cred; char buf[8192]; ssize_t buflen; ssize_t bufpos; struct udev_monitor_netlink_header *nlh; retry: if (udev_monitor == NULL) return NULL; memset(buf, 0x00, sizeof(buf)); iov.iov_base = &buf; iov.iov_len = sizeof(buf); memset (&smsg, 0x00, sizeof(struct msghdr)); smsg.msg_iov = &iov; smsg.msg_iovlen = 1; smsg.msg_control = cred_msg; smsg.msg_controllen = sizeof(cred_msg); if (udev_monitor->snl.nl_family != 0) { smsg.msg_name = &snl; smsg.msg_namelen = sizeof(snl); } buflen = recvmsg(udev_monitor->sock, &smsg, 0); if (buflen < 0) { if (errno != EINTR) info(udev_monitor->udev, "unable to receive message\n"); return NULL; } if (buflen < 32 || (size_t)buflen >= sizeof(buf)) { info(udev_monitor->udev, "invalid message length\n"); return NULL; } if (udev_monitor->snl.nl_family != 0) { if (snl.nl_groups == 0) { /* unicast message, check if we trust the sender */ if (udev_monitor->snl_trusted_sender.nl_pid == 0 || snl.nl_pid != udev_monitor->snl_trusted_sender.nl_pid) { info(udev_monitor->udev, "unicast netlink message ignored\n"); return NULL; } } else if (snl.nl_groups == UDEV_MONITOR_KERNEL) { if (snl.nl_pid > 0) { info(udev_monitor->udev, "multicast kernel netlink message from pid %d ignored\n", snl.nl_pid); return NULL; } } } cmsg = CMSG_FIRSTHDR(&smsg); if (cmsg == NULL || cmsg->cmsg_type != SCM_CREDENTIALS) { info(udev_monitor->udev, "no sender credentials received, message ignored\n"); return NULL; } cred = (struct ucred *)CMSG_DATA(cmsg); if (cred->uid != 0) { info(udev_monitor->udev, "sender uid=%d, message ignored\n", cred->uid); return NULL; } if (strncmp(buf, "udev-", 5) == 0) { /* udev message needs proper version magic */ nlh = (struct udev_monitor_netlink_header *) buf; if (nlh->magic != htonl(UDEV_MONITOR_MAGIC)) return NULL; if (nlh->properties_off < sizeof(struct udev_monitor_netlink_header)) return NULL; if (nlh->properties_off+32 > buflen) return NULL; bufpos = nlh->properties_off; } else { /* kernel message with header */ bufpos = strlen(buf) + 1; if ((size_t)bufpos < sizeof("a@/d") || bufpos >= buflen) { info(udev_monitor->udev, "invalid message length\n"); return NULL; } /* check message header */ if (strstr(buf, "@/") == NULL) { info(udev_monitor->udev, "unrecognized message header\n"); return NULL; } } udev_device = udev_device_new(udev_monitor->udev); if (udev_device == NULL) 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) { info(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) { struct msghdr smsg; struct iovec iov[2]; const char *buf; ssize_t blen; ssize_t count; blen = udev_device_get_properties_monitor_buf(udev_device, &buf); if (blen < 32) return -1; if (udev_monitor->sun.sun_family != 0) { const char *action; char header[2048]; char *s; /* header @ */ action = udev_device_get_action(udev_device); if (action == NULL) return -EINVAL; s = header; if (util_strpcpyl(&s, sizeof(header), action, "@", udev_device_get_devpath(udev_device), NULL) == 0) return -EINVAL; iov[0].iov_base = header; iov[0].iov_len = (s - header)+1; /* add properties list */ iov[1].iov_base = (char *)buf; iov[1].iov_len = blen; memset(&smsg, 0x00, sizeof(struct msghdr)); smsg.msg_iov = iov; smsg.msg_iovlen = 2; smsg.msg_name = &udev_monitor->sun; smsg.msg_namelen = udev_monitor->addrlen; } else if (udev_monitor->snl.nl_family != 0) { const char *val; struct udev_monitor_netlink_header nlh; /* add versioned header */ memset(&nlh, 0x00, sizeof(struct udev_monitor_netlink_header)); util_strscpy(nlh.version, sizeof(nlh.version), "udev-" VERSION); nlh.magic = htonl(UDEV_MONITOR_MAGIC); val = udev_device_get_subsystem(udev_device); nlh.filter_subsystem = htonl(util_string_hash32(val)); val = udev_device_get_devtype(udev_device); if (val != NULL) nlh.filter_devtype = htonl(util_string_hash32(val)); iov[0].iov_base = &nlh; iov[0].iov_len = sizeof(struct udev_monitor_netlink_header); /* 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; memset(&smsg, 0x00, 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); } else { return -1; } count = sendmsg(udev_monitor->sock, &smsg, 0); info(udev_monitor->udev, "passed %zi bytes to 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 * * The filter must be installed before the monitor is switched to listening mode. * * Returns: 0 on success, otherwise a negative error value. */ 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 0; if (udev_list_entry_add(udev_monitor->udev, &udev_monitor->filter_subsystem_list, subsystem, devtype, 0, 0) == 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. */ int udev_monitor_filter_remove(struct udev_monitor *udev_monitor) { static struct sock_fprog filter = { 0, NULL }; udev_list_cleanup_entries(udev_monitor->udev, &udev_monitor->filter_subsystem_list); return setsockopt(udev_monitor->sock, SOL_SOCKET, SO_ATTACH_FILTER, &filter, sizeof(filter)); }