udev/lib/libudev-monitor.c

   1 /*
   2  * libudev - interface to udev device information
   3  *
   4  * Copyright (C) 2008 Kay Sievers <kay.sievers@vrfy.org>
   5  *
   6  * This library is free software; you can redistribute it and/or
   7  * modify it under the terms of the GNU Lesser General Public
   8  * License as published by the Free Software Foundation; either
   9  * version 2.1 of the License, or (at your option) any later version.
  10  */
  11
  12 #include <stdio.h>
  13 #include <stdlib.h>
  14 #include <stddef.h>
  15 #include <unistd.h>
  16 #include <errno.h>
  17 #include <string.h>
  18 #include <dirent.h>
  19 #include <sys/stat.h>
  20 #include <sys/socket.h>
  21 #include <sys/un.h>
  22 #include <linux/netlink.h>
  23
  24 #include "libudev.h"
  25 #include "libudev-private.h"
  26
  27 struct udev_monitor {
  28         struct udev *udev;
  29         int refcount;
  30         int sock;
  31         struct sockaddr_nl snl;
  32         struct sockaddr_nl snl_peer;
  33         struct sockaddr_un sun;
  34         socklen_t addrlen;
  35 };
  36
  37 enum udev_monitor_netlink_group {
  38         UDEV_MONITOR_KERNEL     = 1,
  39         UDEV_MONITOR_UDEV       = 2,
  40 };
  41
  42 /**
  43  * udev_monitor_new_from_socket:
  44  * @udev: udev library context
  45  * @socket_path: unix socket path
  46  *
  47  * Create new udev monitor, setup and connect to a specified socket. The
  48  * path to a socket can point to an existing socket file, or it will be
  49  * created if needed. If neccessary, the permissions adjustment as well as
  50  * the later cleanup of the socket file, needs to be done by the caller.
  51  * If the socket path starts with a '@' character, an abstract namespace
  52  * socket will be used.
  53  *
  54  * The initial refcount is 1, and needs to be decremented to
  55  * release the resources of the udev monitor.
  56  *
  57  * Returns: a new udev monitor, or #NULL, in case of an error
  58  **/
  59 struct udev_monitor *udev_monitor_new_from_socket(struct udev *udev, const char *socket_path)
  60 {
  61         struct udev_monitor *udev_monitor;
  62         struct stat statbuf;
  63
  64         if (udev == NULL)
  65                 return NULL;
  66         if (socket_path == NULL)
  67                 return NULL;
  68         udev_monitor = calloc(1, sizeof(struct udev_monitor));
  69         if (udev_monitor == NULL)
  70                 return NULL;
  71         udev_monitor->refcount = 1;
  72         udev_monitor->udev = udev;
  73
  74         udev_monitor->sun.sun_family = AF_LOCAL;
  75         if (socket_path[0] == '@') {
  76                 /* translate leading '@' to abstract namespace */
  77                 util_strlcpy(udev_monitor->sun.sun_path, socket_path, sizeof(udev_monitor->sun.sun_path));
  78                 udev_monitor->sun.sun_path[0] = '\0';
  79                 udev_monitor->addrlen = offsetof(struct sockaddr_un, sun_path) + strlen(socket_path);
  80         } else if (stat(socket_path, &statbuf) == 0 && S_ISSOCK(statbuf.st_mode)) {
  81                 /* existing socket file */
  82                 util_strlcpy(udev_monitor->sun.sun_path, socket_path, sizeof(udev_monitor->sun.sun_path));
  83                 udev_monitor->addrlen = offsetof(struct sockaddr_un, sun_path) + strlen(socket_path);
  84         } else {
  85                 /* no socket file, assume abstract namespace socket */
  86                 util_strlcpy(&udev_monitor->sun.sun_path[1], socket_path, sizeof(udev_monitor->sun.sun_path)-1);
  87                 udev_monitor->addrlen = offsetof(struct sockaddr_un, sun_path) + strlen(socket_path)+1;
  88         }
  89         udev_monitor->sock = socket(AF_LOCAL, SOCK_DGRAM, 0);
  90         if (udev_monitor->sock == -1) {
  91                 err(udev, "error getting socket: %m\n");
  92                 free(udev_monitor);
  93                 return NULL;
  94         }
  95         dbg(udev, "monitor %p created with '%s'\n", udev_monitor, socket_path);
  96         return udev_monitor;
  97 }
  98
  99 struct udev_monitor *udev_monitor_new_from_netlink(struct udev *udev, const char *name)
 100 {
 101         struct udev_monitor *udev_monitor;
 102         unsigned int group;
 103
 104         if (udev == NULL)
 105                 return NULL;
 106
 107         if (name == NULL)
 108                 return NULL;
 109         if (strcmp(name, "kernel") == 0)
 110                 group = UDEV_MONITOR_KERNEL;
 111         else if (strcmp(name, "udev") == 0)
 112                 group = UDEV_MONITOR_UDEV;
 113         else
 114                 return NULL;
 115
 116         udev_monitor = calloc(1, sizeof(struct udev_monitor));
 117         if (udev_monitor == NULL)
 118                 return NULL;
 119         udev_monitor->refcount = 1;
 120         udev_monitor->udev = udev;
 121
 122         udev_monitor->sock = socket(PF_NETLINK, SOCK_DGRAM, NETLINK_KOBJECT_UEVENT);
 123         if (udev_monitor->sock == -1) {
 124                 err(udev, "error getting socket: %m\n");
 125                 free(udev_monitor);
 126                 return NULL;
 127         }
 128
 129         udev_monitor->snl.nl_family = AF_NETLINK;
 130         udev_monitor->snl.nl_groups = group;
 131         udev_monitor->snl_peer.nl_family = AF_NETLINK;
 132         udev_monitor->snl_peer.nl_groups = UDEV_MONITOR_UDEV;
 133
 134         dbg(udev, "monitor %p created with NETLINK_KOBJECT_UEVENT (%u)\n", udev_monitor, group);
 135         return udev_monitor;
 136 }
 137
 138 int udev_monitor_enable_receiving(struct udev_monitor *udev_monitor)
 139 {
 140         int err;
 141         const int on = 1;
 142
 143         if (udev_monitor->snl.nl_family != 0) {
 144                 err = bind(udev_monitor->sock,
 145                            (struct sockaddr *)&udev_monitor->snl, sizeof(struct sockaddr_nl));
 146                 if (err < 0) {
 147                         err(udev_monitor->udev, "bind failed: %m\n");
 148                         return err;
 149                 }
 150                 dbg(udev_monitor->udev, "monitor %p listening on netlink\n", udev_monitor);
 151         } else if (udev_monitor->sun.sun_family != 0) {
 152                 err = bind(udev_monitor->sock,
 153                            (struct sockaddr *)&udev_monitor->sun, udev_monitor->addrlen);
 154                 if (err < 0) {
 155                         err(udev_monitor->udev, "bind failed: %m\n");
 156                         return err;
 157                 }
 158                 /* enable receiving of the sender credentials */
 159                 setsockopt(udev_monitor->sock, SOL_SOCKET, SO_PASSCRED, &on, sizeof(on));
 160                 dbg(udev_monitor->udev, "monitor %p listening on socket\n", udev_monitor);
 161         }
 162         return 0;
 163 }
 164
 165 int udev_monitor_set_receive_buffer_size(struct udev_monitor *udev_monitor, int size)
 166 {
 167         if (udev_monitor == NULL)
 168                 return -1;
 169         return setsockopt(udev_monitor->sock, SOL_SOCKET, SO_RCVBUFFORCE, &size, sizeof(size));
 170 }
 171
 172 /**
 173  * udev_monitor_ref:
 174  * @udev_monitor: udev monitor
 175  *
 176  * Take a reference of a udev monitor.
 177  *
 178  * Returns: the passed udev monitor
 179  **/
 180 struct udev_monitor *udev_monitor_ref(struct udev_monitor *udev_monitor)
 181 {
 182         if (udev_monitor == NULL)
 183                 return NULL;
 184         udev_monitor->refcount++;
 185         return udev_monitor;
 186 }
 187
 188 /**
 189  * udev_monitor_unref:
 190  * @udev_monitor: udev monitor
 191  *
 192  * Drop a reference ofa udev monitor. If the refcount reaches zero,
 193  * the bound socket will be closed, and the resources of the monitor
 194  * will be released.
 195  *
 196  **/
 197 void udev_monitor_unref(struct udev_monitor *udev_monitor)
 198 {
 199         if (udev_monitor == NULL)
 200                 return;
 201         udev_monitor->refcount--;
 202         if (udev_monitor->refcount > 0)
 203                 return;
 204         if (udev_monitor->sock >= 0)
 205                 close(udev_monitor->sock);
 206         dbg(udev_monitor->udev, "monitor %p released\n", udev_monitor);
 207         free(udev_monitor);
 208 }
 209
 210 /**
 211  * udev_monitor_get_udev:
 212  * @udev_monitor: udev monitor
 213  *
 214  * Retrieve the udev library context the monitor was created with.
 215  *
 216  * Returns: the udev library context
 217  **/
 218 struct udev *udev_monitor_get_udev(struct udev_monitor *udev_monitor)
 219 {
 220         if (udev_monitor == NULL)
 221                 return NULL;
 222         return udev_monitor->udev;
 223 }
 224
 225 /**
 226  * udev_monitor_get_fd:
 227  * @udev_monitor: udev monitor
 228  *
 229  * Retrieve the socket file descriptor associated with the monitor.
 230  *
 231  * Returns: the socket file descriptor
 232  **/
 233 int udev_monitor_get_fd(struct udev_monitor *udev_monitor)
 234 {
 235         if (udev_monitor == NULL)
 236                 return -1;
 237         return udev_monitor->sock;
 238 }
 239
 240 /**
 241  * udev_monitor_receive_device:
 242  * @udev_monitor: udev monitor
 243  *
 244  * Receive data from the udev monitor socket, allocate a new udev
 245  * device, fill in the received data, and return the device.
 246  *
 247  * Only socket connections with uid=0 are accepted. The caller
 248  * needs to make sure that there is data to read from the socket.
 249  * The call will block until the socket becomes readable.
 250  *
 251  * The initial refcount is 1, and needs to be decremented to
 252  * release the resources of the udev device.
 253  *
 254  * Returns: a new udev device, or #NULL, in case of an error
 255  **/
 256 struct udev_device *udev_monitor_receive_device(struct udev_monitor *udev_monitor)
 257 {
 258         struct udev_device *udev_device;
 259         struct msghdr smsg;
 260         struct iovec iov;
 261         char cred_msg[CMSG_SPACE(sizeof(struct ucred))];
 262         char buf[4096];
 263         size_t bufpos;
 264         int devpath_set = 0;
 265         int subsystem_set = 0;
 266         int action_set = 0;
 267         int maj = 0;
 268         int min = 0;
 269
 270         if (udev_monitor == NULL)
 271                 return NULL;
 272         memset(buf, 0x00, sizeof(buf));
 273         iov.iov_base = &buf;
 274         iov.iov_len = sizeof(buf);
 275         memset (&smsg, 0x00, sizeof(struct msghdr));
 276         smsg.msg_iov = &iov;
 277         smsg.msg_iovlen = 1;
 278         smsg.msg_control = cred_msg;
 279         smsg.msg_controllen = sizeof(cred_msg);
 280
 281         if (recvmsg(udev_monitor->sock, &smsg, 0) < 0) {
 282                 if (errno != EINTR)
 283                         info(udev_monitor->udev, "unable to receive message");
 284                 return NULL;
 285         }
 286
 287         if (udev_monitor->sun.sun_family != 0) {
 288                 struct cmsghdr *cmsg = CMSG_FIRSTHDR(&smsg);
 289                 struct ucred *cred = (struct ucred *)CMSG_DATA (cmsg);
 290
 291                 if (cmsg == NULL || cmsg->cmsg_type != SCM_CREDENTIALS) {
 292                         info(udev_monitor->udev, "no sender credentials received, message ignored");
 293                         return NULL;
 294                 }
 295
 296                 if (cred->uid != 0) {
 297                         info(udev_monitor->udev, "sender uid=%d, message ignored", cred->uid);
 298                         return NULL;
 299                 }
 300         }
 301
 302         /* skip header */
 303         bufpos = strlen(buf) + 1;
 304         if (bufpos < sizeof("a@/d") || bufpos >= sizeof(buf)) {
 305                 info(udev_monitor->udev, "invalid message length");
 306                 return NULL;
 307         }
 308
 309         /* check message header */
 310         if (strstr(buf, "@/") == NULL) {
 311                 info(udev_monitor->udev, "unrecognized message header");
 312                 return NULL;
 313         }
 314
 315         udev_device = device_new(udev_monitor->udev);
 316         if (udev_device == NULL) {
 317                 return NULL;
 318         }
 319
 320         while (bufpos < sizeof(buf)) {
 321                 char *key;
 322                 size_t keylen;
 323
 324                 key = &buf[bufpos];
 325                 keylen = strlen(key);
 326                 if (keylen == 0)
 327                         break;
 328                 bufpos += keylen + 1;
 329
 330                 if (strncmp(key, "DEVPATH=", 8) == 0) {
 331                         char path[UTIL_PATH_SIZE];
 332
 333                         util_strlcpy(path, udev_get_sys_path(udev_monitor->udev), sizeof(path));
 334                         util_strlcat(path, &key[8], sizeof(path));
 335                         udev_device_set_syspath(udev_device, path);
 336                         devpath_set = 1;
 337                 } else if (strncmp(key, "SUBSYSTEM=", 10) == 0) {
 338                         udev_device_set_subsystem(udev_device, &key[10]);
 339                         subsystem_set = 1;
 340                 } else if (strncmp(key, "DEVTYPE=", 8) == 0) {
 341                         udev_device_set_devtype(udev_device, &key[8]);
 342                 } else if (strncmp(key, "DEVNAME=", 8) == 0) {
 343                         udev_device_set_devnode(udev_device, &key[8]);
 344                 } else if (strncmp(key, "DEVLINKS=", 9) == 0) {
 345                         char devlinks[UTIL_PATH_SIZE];
 346                         char *slink;
 347                         char *next;
 348
 349                         util_strlcpy(devlinks, &key[9], sizeof(devlinks));
 350                         slink = devlinks;
 351                         next = strchr(slink, ' ');
 352                         while (next != NULL) {
 353                                 next[0] = '\0';
 354                                 udev_device_add_devlink(udev_device, slink);
 355                                 slink = &next[1];
 356                                 next = strchr(slink, ' ');
 357                         }
 358                         if (slink[0] != '\0')
 359                                 udev_device_add_devlink(udev_device, slink);
 360                 } else if (strncmp(key, "DRIVER=", 7) == 0) {
 361                         udev_device_set_driver(udev_device, &key[7]);
 362                 } else if (strncmp(key, "ACTION=", 7) == 0) {
 363                         udev_device_set_action(udev_device, &key[7]);
 364                         action_set = 1;
 365                 } else if (strncmp(key, "MAJOR=", 6) == 0) {
 366                         maj = strtoull(&key[6], NULL, 10);
 367                 } else if (strncmp(key, "MINOR=", 6) == 0) {
 368                         min = strtoull(&key[6], NULL, 10);
 369                 } else if (strncmp(key, "DEVPATH_OLD=", 12) == 0) {
 370                         udev_device_set_devpath_old(udev_device, &key[12]);
 371                 } else if (strncmp(key, "PHYSDEVPATH=", 12) == 0) {
 372                         udev_device_set_physdevpath(udev_device, &key[12]);
 373                 } else if (strncmp(key, "SEQNUM=", 7) == 0) {
 374                         udev_device_set_seqnum(udev_device, strtoull(&key[7], NULL, 10));
 375                 } else if (strncmp(key, "TIMEOUT=", 8) == 0) {
 376                         udev_device_set_timeout(udev_device, strtoull(&key[8], NULL, 10));
 377                 } else if (strncmp(key, "PHYSDEV", 7) == 0) {
 378                         /* skip deprecated values */
 379                         continue;
 380                 } else {
 381                         udev_device_add_property_from_string(udev_device, key);
 382                 }
 383         }
 384         if (!devpath_set || !subsystem_set || !action_set) {
 385                 info(udev_monitor->udev, "missing values, skip\n");
 386                 udev_device_unref(udev_device);
 387                 return NULL;
 388         }
 389         if (maj > 0)
 390                 udev_device_set_devnum(udev_device, makedev(maj, min));
 391         udev_device_set_info_loaded(udev_device);
 392         return udev_device;
 393 }
 394
 395 int udev_monitor_send_device(struct udev_monitor *udev_monitor, struct udev_device *udev_device)
 396 {
 397         const char *buf;
 398         ssize_t len;
 399         ssize_t count;
 400
 401         len = udev_device_get_properties_monitor_buf(udev_device, &buf);
 402         if (len < 32)
 403                 return -1;
 404         if (udev_monitor->sun.sun_family != 0) {
 405                 count = sendto(udev_monitor->sock,
 406                                buf, len, 0,
 407                                (struct sockaddr *)&udev_monitor->sun,
 408                                udev_monitor->addrlen);
 409         } else {
 410                 /* no destination besides the muticast group, we will always get -1 ECONNREFUSED */
 411                 count = sendto(udev_monitor->sock,
 412                                buf, len, 0,
 413                                (struct sockaddr *)&udev_monitor->snl_peer,
 414                                sizeof(struct sockaddr_nl));
 415         }
 416         info(udev_monitor->udev, "passed %zi bytes to monitor %p, \n", count, udev_monitor);
 417         return count;
 418 }