udevd.c

   1 /*
   2  * udevd.c - hotplug event serializer
   3  *
   4  * Copyright (C) 2004 Kay Sievers <kay.sievers@vrfy.org>
   5  * Copyright (C) 2004 Chris Friesen <chris_friesen@sympatico.ca>
   6  *
   7  *
   8  *      This program is free software; you can redistribute it and/or modify it
   9  *      under the terms of the GNU General Public License as published by the
  10  *      Free Software Foundation version 2 of the License.
  11  *
  12  *      This program is distributed in the hope that it will be useful, but
  13  *      WITHOUT ANY WARRANTY; without even the implied warranty of
  14  *      MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  15  *      General Public License for more details.
  16  *
  17  *      You should have received a copy of the GNU General Public License along
  18  *      with this program; if not, write to the Free Software Foundation, Inc.,
  19  *      675 Mass Ave, Cambridge, MA 02139, USA.
  20  *
  21  */
  22
  23 #include <stddef.h>
  24 #include <sys/wait.h>
  25 #include <signal.h>
  26 #include <unistd.h>
  27 #include <errno.h>
  28 #include <stdio.h>
  29 #include <stdlib.h>
  30 #include <string.h>
  31 #include <sys/time.h>
  32 #include <sys/types.h>
  33 #include <sys/socket.h>
  34 #include <sys/un.h>
  35 #include <fcntl.h>
  36 #include "klibc_fixups.h"
  37 #ifndef __KLIBC__
  38 #include <sys/sysinfo.h>
  39 #endif
  40
  41 #include "list.h"
  42 #include "udev.h"
  43 #include "udev_lib.h"
  44 #include "udev_version.h"
  45 #include "udevd.h"
  46 #include "logging.h"
  47
  48 static int pipefds[2];
  49 static int expected_seqnum = 0;
  50 volatile static int children_waiting;
  51 volatile static int run_msg_q;
  52 volatile static int sig_flag;
  53 static int run_exec_q;
  54
  55 static LIST_HEAD(msg_list);
  56 static LIST_HEAD(exec_list);
  57 static LIST_HEAD(running_list);
  58
  59 static void exec_queue_manager(void);
  60 static void msg_queue_manager(void);
  61 static void user_sighandler(void);
  62 static void reap_kids(void);
  63
  64 #ifdef LOG
  65 unsigned char logname[LOGNAME_SIZE];
  66 void log_message (int level, const char *format, ...)
  67 {
  68         va_list args;
  69
  70         va_start(args, format);
  71         vsyslog(level, format, args);
  72         va_end(args);
  73 }
  74 #endif
  75
  76 #define msg_dump(msg) \
  77         dbg("msg_dump: sequence %d, '%s', '%s', '%s'", \
  78         msg->seqnum, msg->action, msg->devpath, msg->subsystem);
  79
  80 static void msg_dump_queue(void)
  81 {
  82 #ifdef DEBUG
  83         struct hotplug_msg *msg;
  84
  85         list_for_each_entry(msg, &msg_list, list)
  86                 dbg("sequence %d in queue", msg->seqnum);
  87 #endif
  88 }
  89
  90 static struct hotplug_msg *msg_create(void)
  91 {
  92         struct hotplug_msg *new_msg;
  93
  94         new_msg = malloc(sizeof(struct hotplug_msg));
  95         if (new_msg == NULL)
  96                 dbg("error malloc");
  97         return new_msg;
  98 }
  99
 100 static void run_queue_delete(struct hotplug_msg *msg)
 101 {
 102         list_del(&msg->list);
 103         free(msg);
 104 }
 105
 106 /* orders the message in the queue by sequence number */
 107 static void msg_queue_insert(struct hotplug_msg *msg)
 108 {
 109         struct hotplug_msg *loop_msg;
 110         struct sysinfo info;
 111
 112         /* sort message by sequence number into list. events
 113          * will tend to come in order, so scan the list backwards
 114          */
 115         list_for_each_entry_reverse(loop_msg, &msg_list, list)
 116                 if (loop_msg->seqnum < msg->seqnum)
 117                         break;
 118
 119         /* store timestamp of queuing */
 120         sysinfo(&info);
 121         msg->queue_time = info.uptime;
 122
 123         list_add(&msg->list, &loop_msg->list);
 124         dbg("queued message seq %d", msg->seqnum);
 125
 126         /* run msg queue manager */
 127         run_msg_q = 1;
 128
 129         return ;
 130 }
 131
 132 /* forks event and removes event from run queue when finished */
 133 static void udev_run(struct hotplug_msg *msg)
 134 {
 135         pid_t pid;
 136         char action[ACTION_SIZE];
 137         char devpath[DEVPATH_SIZE];
 138         char *env[] = { action, devpath, NULL };
 139
 140         strcpy(action, "ACTION=");
 141         strfieldcat(action, msg->action);
 142         strcpy(devpath, "DEVPATH=");
 143         strfieldcat(devpath, msg->devpath);
 144
 145         pid = fork();
 146         switch (pid) {
 147         case 0:
 148                 /* child */
 149                 execle(UDEV_BIN, "udev", msg->subsystem, NULL, env);
 150                 dbg("exec of child failed");
 151                 exit(1);
 152                 break;
 153         case -1:
 154                 dbg("fork of child failed");
 155                 run_queue_delete(msg);
 156                 /* note: we never managed to run, so we had no impact on
 157                  * running_with_devpath(), so don't bother setting run_exec_q
 158                  */
 159                 break;
 160         default:
 161                 /* get SIGCHLD in main loop */
 162                 dbg("==> exec seq %d [%d] working at '%s'", msg->seqnum, pid, msg->devpath);
 163                 msg->pid = pid;
 164         }
 165 }
 166
 167 /* returns already running task with devpath */
 168 static struct hotplug_msg *running_with_devpath(struct hotplug_msg *msg)
 169 {
 170         struct hotplug_msg *loop_msg;
 171         list_for_each_entry(loop_msg, &running_list, list)
 172                 if (strncmp(loop_msg->devpath, msg->devpath, sizeof(loop_msg->devpath)) == 0)
 173                         return loop_msg;
 174         return NULL;
 175 }
 176
 177 /* exec queue management routine executes the events and delays events for the same devpath */
 178 static void exec_queue_manager()
 179 {
 180         struct hotplug_msg *loop_msg;
 181         struct hotplug_msg *tmp_msg;
 182         struct hotplug_msg *msg;
 183
 184         list_for_each_entry_safe(loop_msg, tmp_msg, &exec_list, list) {
 185                 msg = running_with_devpath(loop_msg);
 186                 if (!msg) {
 187                         /* move event to run list */
 188                         list_move_tail(&loop_msg->list, &running_list);
 189                         udev_run(loop_msg);
 190                         dbg("moved seq %d to running list", loop_msg->seqnum);
 191                 } else {
 192                         dbg("delay seq %d, cause seq %d already working on '%s'",
 193                                 loop_msg->seqnum, msg->seqnum, msg->devpath);
 194                 }
 195         }
 196 }
 197
 198 static void msg_move_exec(struct hotplug_msg *msg)
 199 {
 200         list_move_tail(&msg->list, &exec_list);
 201         run_exec_q = 1;
 202         expected_seqnum = msg->seqnum+1;
 203         dbg("moved seq %d to exec, next expected is %d",
 204                 msg->seqnum, expected_seqnum);
 205 }
 206
 207 /* msg queue management routine handles the timeouts and dispatches the events */
 208 static void msg_queue_manager()
 209 {
 210         struct hotplug_msg *loop_msg;
 211         struct hotplug_msg *tmp_msg;
 212         struct sysinfo info;
 213         long msg_age = 0;
 214
 215         dbg("msg queue manager, next expected is %d", expected_seqnum);
 216 recheck:
 217         list_for_each_entry_safe(loop_msg, tmp_msg, &msg_list, list) {
 218                 /* move event with expected sequence to the exec list */
 219                 if (loop_msg->seqnum == expected_seqnum) {
 220                         msg_move_exec(loop_msg);
 221                         continue;
 222                 }
 223
 224                 /* move event with expired timeout to the exec list */
 225                 sysinfo(&info);
 226                 msg_age = info.uptime - loop_msg->queue_time;
 227                 dbg("seq %d is %li seconds old", loop_msg->seqnum, msg_age);
 228                 if (msg_age > EVENT_TIMEOUT_SEC-1) {
 229                         msg_move_exec(loop_msg);
 230                         goto recheck;
 231                 } else {
 232                         break;
 233                 }
 234         }
 235
 236         msg_dump_queue();
 237
 238         /* set timeout for remaining queued events */
 239         if (list_empty(&msg_list) == 0) {
 240                 struct itimerval itv = {{0, 0}, {EVENT_TIMEOUT_SEC - msg_age, 0}};
 241                 dbg("next event expires in %li seconds", EVENT_TIMEOUT_SEC - msg_age);
 242                 setitimer(ITIMER_REAL, &itv, 0);
 243         }
 244 }
 245
 246 /* receive the msg, do some basic sanity checks, and queue it */
 247 static void handle_msg(int sock)
 248 {
 249         struct hotplug_msg *msg;
 250         int retval;
 251         struct msghdr smsg;
 252         struct cmsghdr *cmsg;
 253         struct iovec iov;
 254         struct ucred *cred;
 255         char cred_msg[CMSG_SPACE(sizeof(struct ucred))];
 256
 257         msg = msg_create();
 258         if (msg == NULL) {
 259                 dbg("unable to store message");
 260                 return;
 261         }
 262
 263         iov.iov_base = msg;
 264         iov.iov_len = sizeof(struct hotplug_msg);
 265
 266         memset(&smsg, 0x00, sizeof(struct msghdr));
 267         smsg.msg_iov = &iov;
 268         smsg.msg_iovlen = 1;
 269         smsg.msg_control = cred_msg;
 270         smsg.msg_controllen = sizeof(cred_msg);
 271
 272         retval = recvmsg(sock, &smsg, 0);
 273         if (retval <  0) {
 274                 if (errno != EINTR)
 275                         dbg("unable to receive message");
 276                 return;
 277         }
 278         cmsg = CMSG_FIRSTHDR(&smsg);
 279         cred = (struct ucred *) CMSG_DATA(cmsg);
 280
 281         if (cmsg == NULL || cmsg->cmsg_type != SCM_CREDENTIALS) {
 282                 dbg("no sender credentials received, message ignored");
 283                 goto skip;
 284         }
 285
 286         if (cred->uid != 0) {
 287                 dbg("sender uid=%i, message ignored", cred->uid);
 288                 goto skip;
 289         }
 290
 291         if (strncmp(msg->magic, UDEV_MAGIC, sizeof(UDEV_MAGIC)) != 0 ) {
 292                 dbg("message magic '%s' doesn't match, ignore it", msg->magic);
 293                 goto skip;
 294         }
 295
 296         /* if no seqnum is given, we move straight to exec queue */
 297         if (msg->seqnum == -1) {
 298                 list_add(&msg->list, &exec_list);
 299                 run_exec_q = 1;
 300         } else {
 301                 msg_queue_insert(msg);
 302         }
 303         return;
 304
 305 skip:
 306         free(msg);
 307         return;
 308 }
 309
 310 static void sig_handler(int signum)
 311 {
 312         int rc;
 313         switch (signum) {
 314                 case SIGINT:
 315                 case SIGTERM:
 316                         exit(20 + signum);
 317                         break;
 318                 case SIGALRM:
 319                         /* set flag, then write to pipe if needed */
 320                         run_msg_q = 1;
 321                         goto do_write;
 322                         break;
 323                 case SIGCHLD:
 324                         /* set flag, then write to pipe if needed */
 325                         children_waiting = 1;
 326                         goto do_write;
 327                         break;
 328                 default:
 329                         dbg("unhandled signal");
 330                         return;
 331         }
 332
 333 do_write:
 334         /* if pipe is empty, write to pipe to force select to return
 335          * immediately when it gets called
 336          */
 337         if (!sig_flag) {
 338                 rc = write(pipefds[1],&signum,sizeof(signum));
 339                 if (rc < 0)
 340                         dbg("unable to write to pipe");
 341                 else
 342                         sig_flag = 1;
 343         }
 344 }
 345
 346 static void udev_done(int pid)
 347 {
 348         /* find msg associated with pid and delete it */
 349         struct hotplug_msg *msg;
 350
 351         list_for_each_entry(msg, &running_list, list) {
 352                 if (msg->pid == pid) {
 353                         dbg("<== exec seq %d came back", msg->seqnum);
 354                         run_queue_delete(msg);
 355
 356                         /* we want to run the exec queue manager since there may
 357                          * be events waiting with the devpath of the one that
 358                          * just finished
 359                          */
 360                         run_exec_q = 1;
 361                         return;
 362                 }
 363         }
 364 }
 365
 366 static void reap_kids()
 367 {
 368         /* reap all dead children */
 369         while(1) {
 370                 int pid = waitpid(-1, 0, WNOHANG);
 371                 if ((pid == -1) || (pid == 0))
 372                         break;
 373                 udev_done(pid);
 374         }
 375 }
 376
 377 /* just read everything from the pipe and clear the flag,
 378  * the useful flags were set in the signal handler
 379  */
 380 static void user_sighandler()
 381 {
 382         int sig;
 383         while(1) {
 384                 int rc = read(pipefds[0],&sig,sizeof(sig));
 385                 if (rc < 0)
 386                         break;
 387
 388                 sig_flag = 0;
 389         }
 390 }
 391
 392
 393 int main(int argc, char *argv[])
 394 {
 395         int ssock, maxsockplus;
 396         struct sockaddr_un saddr;
 397         socklen_t addrlen;
 398         int retval;
 399         const int on = 1;
 400         struct sigaction act;
 401         fd_set readfds;
 402
 403         init_logging("udevd");
 404         dbg("version %s", UDEV_VERSION);
 405
 406         if (getuid() != 0) {
 407                 dbg("need to be root, exit");
 408                 exit(1);
 409         }
 410
 411         /* setup signal handler pipe */
 412         retval = pipe(pipefds);
 413         if (retval < 0) {
 414                 dbg("error getting pipes: %s", strerror(errno));
 415                 exit(1);
 416         }
 417
 418         retval = fcntl(pipefds[0], F_SETFL, O_NONBLOCK);
 419                 if (retval < 0) {
 420                 dbg("error fcntl on read pipe: %s", strerror(errno));
 421                 exit(1);
 422         }
 423
 424         retval = fcntl(pipefds[1], F_SETFL, O_NONBLOCK);
 425         if (retval < 0) {
 426                 dbg("error fcntl on write pipe: %s", strerror(errno));
 427                 exit(1);
 428         }
 429
 430         /* set signal handlers */
 431         act.sa_handler = sig_handler;
 432         sigemptyset(&act.sa_mask);
 433         act.sa_flags = SA_RESTART;
 434         sigaction(SIGINT, &act, NULL);
 435         sigaction(SIGTERM, &act, NULL);
 436         sigaction(SIGALRM, &act, NULL);
 437         sigaction(SIGCHLD, &act, NULL);
 438
 439         memset(&saddr, 0x00, sizeof(saddr));
 440         saddr.sun_family = AF_LOCAL;
 441         /* use abstract namespace for socket path */
 442         strcpy(&saddr.sun_path[1], UDEVD_SOCK_PATH);
 443         addrlen = offsetof(struct sockaddr_un, sun_path) + strlen(saddr.sun_path+1) + 1;
 444
 445         ssock = socket(AF_LOCAL, SOCK_DGRAM, 0);
 446         if (ssock == -1) {
 447                 dbg("error getting socket, exit");
 448                 exit(1);
 449         }
 450
 451         /* the bind takes care of ensuring only one copy running */
 452         retval = bind(ssock, (struct sockaddr *) &saddr, addrlen);
 453         if (retval < 0) {
 454                 dbg("bind failed, exit");
 455                 goto exit;
 456         }
 457
 458         /* enable receiving of the sender credentials */
 459         setsockopt(ssock, SOL_SOCKET, SO_PASSCRED, &on, sizeof(on));
 460
 461         FD_ZERO(&readfds);
 462         FD_SET(ssock, &readfds);
 463         FD_SET(pipefds[0], &readfds);
 464         maxsockplus = ssock+1;
 465         while (1) {
 466                 fd_set workreadfds = readfds;
 467                 retval = select(maxsockplus, &workreadfds, NULL, NULL, NULL);
 468
 469                 if (retval < 0) {
 470                         if (errno != EINTR)
 471                                 dbg("error in select: %s", strerror(errno));
 472                         continue;
 473                 }
 474
 475                 if (FD_ISSET(ssock, &workreadfds))
 476                         handle_msg(ssock);
 477
 478                 if (FD_ISSET(pipefds[0], &workreadfds))
 479                         user_sighandler();
 480
 481                 if (children_waiting) {
 482                         children_waiting = 0;
 483                         reap_kids();
 484                 }
 485
 486                 if (run_msg_q) {
 487                         run_msg_q = 0;
 488                         msg_queue_manager();
 489                 }
 490
 491                 if (run_exec_q) {
 492                         /* this is tricky.  exec_queue_manager() loops over exec_list, and
 493                          * calls running_with_devpath(), which loops over running_list. This gives
 494                          * O(N*M), which can get *nasty*.  Clean up running_list before
 495                          * calling exec_queue_manager().
 496                          */
 497                         if (children_waiting) {
 498                                 children_waiting = 0;
 499                                 reap_kids();
 500                         }
 501
 502                         run_exec_q = 0;
 503                         exec_queue_manager();
 504                 }
 505         }
 506 exit:
 507         close(ssock);
 508         exit(1);
 509 }