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 static void msg_dump_queue(void)
  77 {
  78 #ifdef DEBUG
  79         struct hotplug_msg *msg;
  80
  81         list_for_each_entry(msg, &msg_list, list)
  82                 dbg("sequence %d in queue", msg->seqnum);
  83 #endif
  84 }
  85
  86 #if 0
  87 static void msg_dump(struct hotplug_msg *msg)
  88 {
  89         dbg("sequence %d, '%s', '%s', '%s'",
  90             msg->seqnum, msg->action, msg->devpath, msg->subsystem);
  91 }
  92 #endif
  93
  94 static struct hotplug_msg *msg_create(void)
  95 {
  96         struct hotplug_msg *new_msg;
  97
  98         new_msg = malloc(sizeof(struct hotplug_msg));
  99         if (new_msg == NULL)
 100                 dbg("error malloc");
 101         return new_msg;
 102 }
 103
 104 static void run_queue_delete(struct hotplug_msg *msg)
 105 {
 106         list_del(&msg->list);
 107         free(msg);
 108 }
 109
 110 /* orders the message in the queue by sequence number */
 111 static void msg_queue_insert(struct hotplug_msg *msg)
 112 {
 113         struct hotplug_msg *loop_msg;
 114         struct sysinfo info;
 115
 116         /* sort message by sequence number into list. events
 117          * will tend to come in order, so scan the list backwards
 118          */
 119         list_for_each_entry_reverse(loop_msg, &msg_list, list)
 120                 if (loop_msg->seqnum < msg->seqnum)
 121                         break;
 122
 123         /* store timestamp of queuing */
 124         sysinfo(&info);
 125         msg->queue_time = info.uptime;
 126
 127         list_add(&msg->list, &loop_msg->list);
 128         dbg("queued message seq %d", msg->seqnum);
 129
 130         /* run msg queue manager */
 131         run_msg_q = 1;
 132
 133         return ;
 134 }
 135
 136 /* forks event and removes event from run queue when finished */
 137 static void udev_run(struct hotplug_msg *msg)
 138 {
 139         pid_t pid;
 140         char action[ACTION_SIZE];
 141         char devpath[DEVPATH_SIZE];
 142         char *env[] = { action, devpath, NULL };
 143
 144         strcpy(action, "ACTION=");
 145         strfieldcat(action, msg->action);
 146         strcpy(devpath, "DEVPATH=");
 147         strfieldcat(devpath, msg->devpath);
 148
 149         pid = fork();
 150         switch (pid) {
 151         case 0:
 152                 /* child */
 153                 execle(UDEV_BIN, "udev", msg->subsystem, NULL, env);
 154                 dbg("exec of child failed");
 155                 exit(1);
 156                 break;
 157         case -1:
 158                 dbg("fork of child failed");
 159                 run_queue_delete(msg);
 160                 /* note: we never managed to run, so we had no impact on
 161                  * running_with_devpath(), so don't bother setting run_exec_q
 162                  */
 163                 break;
 164         default:
 165                 /* get SIGCHLD in main loop */
 166                 dbg("==> exec seq %d [%d] working at '%s'", msg->seqnum, pid, msg->devpath);
 167                 msg->pid = pid;
 168         }
 169 }
 170
 171 /* returns already running task with devpath */
 172 static struct hotplug_msg *running_with_devpath(struct hotplug_msg *msg)
 173 {
 174         struct hotplug_msg *loop_msg;
 175         list_for_each_entry(loop_msg, &running_list, list)
 176                 if (strncmp(loop_msg->devpath, msg->devpath, sizeof(loop_msg->devpath)) == 0)
 177                         return loop_msg;
 178         return NULL;
 179 }
 180
 181 /* exec queue management routine executes the events and delays events for the same devpath */
 182 static void exec_queue_manager()
 183 {
 184         struct hotplug_msg *loop_msg;
 185         struct hotplug_msg *tmp_msg;
 186         struct hotplug_msg *msg;
 187
 188         list_for_each_entry_safe(loop_msg, tmp_msg, &exec_list, list) {
 189                 msg = running_with_devpath(loop_msg);
 190                 if (!msg) {
 191                         /* move event to run list */
 192                         list_move_tail(&loop_msg->list, &running_list);
 193                         udev_run(loop_msg);
 194                         dbg("moved seq %d to running list", loop_msg->seqnum);
 195                 } else {
 196                         dbg("delay seq %d, cause seq %d already working on '%s'",
 197                                 loop_msg->seqnum, msg->seqnum, msg->devpath);
 198                 }
 199         }
 200 }
 201
 202 static void msg_move_exec(struct hotplug_msg *msg)
 203 {
 204         list_move_tail(&msg->list, &exec_list);
 205         run_exec_q = 1;
 206         expected_seqnum = msg->seqnum+1;
 207         dbg("moved seq %d to exec, next expected is %d",
 208                 msg->seqnum, expected_seqnum);
 209 }
 210
 211 /* msg queue management routine handles the timeouts and dispatches the events */
 212 static void msg_queue_manager()
 213 {
 214         struct hotplug_msg *loop_msg;
 215         struct hotplug_msg *tmp_msg;
 216         struct sysinfo info;
 217         long msg_age = 0;
 218
 219         dbg("msg queue manager, next expected is %d", expected_seqnum);
 220 recheck:
 221         list_for_each_entry_safe(loop_msg, tmp_msg, &msg_list, list) {
 222                 /* move event with expected sequence to the exec list */
 223                 if (loop_msg->seqnum == expected_seqnum) {
 224                         msg_move_exec(loop_msg);
 225                         continue;
 226                 }
 227
 228                 /* move event with expired timeout to the exec list */
 229                 sysinfo(&info);
 230                 msg_age = info.uptime - loop_msg->queue_time;
 231                 dbg("seq %d is %li seconds old", loop_msg->seqnum, msg_age);
 232                 if (msg_age > EVENT_TIMEOUT_SEC-1) {
 233                         msg_move_exec(loop_msg);
 234                         goto recheck;
 235                 } else {
 236                         break;
 237                 }
 238         }
 239
 240         msg_dump_queue();
 241
 242         /* set timeout for remaining queued events */
 243         if (list_empty(&msg_list) == 0) {
 244                 struct itimerval itv = {{0, 0}, {EVENT_TIMEOUT_SEC - msg_age, 0}};
 245                 dbg("next event expires in %li seconds", EVENT_TIMEOUT_SEC - msg_age);
 246                 setitimer(ITIMER_REAL, &itv, 0);
 247         }
 248 }
 249
 250 /* receive the msg, do some basic sanity checks, and queue it */
 251 static void handle_msg(int sock)
 252 {
 253         struct hotplug_msg *msg;
 254         int retval;
 255         struct msghdr smsg;
 256         struct cmsghdr *cmsg;
 257         struct iovec iov;
 258         struct ucred *cred;
 259         char cred_msg[CMSG_SPACE(sizeof(struct ucred))];
 260
 261         msg = msg_create();
 262         if (msg == NULL) {
 263                 dbg("unable to store message");
 264                 return;
 265         }
 266
 267         iov.iov_base = msg;
 268         iov.iov_len = sizeof(struct hotplug_msg);
 269
 270         memset(&smsg, 0x00, sizeof(struct msghdr));
 271         smsg.msg_iov = &iov;
 272         smsg.msg_iovlen = 1;
 273         smsg.msg_control = cred_msg;
 274         smsg.msg_controllen = sizeof(cred_msg);
 275
 276         retval = recvmsg(sock, &smsg, 0);
 277         if (retval <  0) {
 278                 if (errno != EINTR)
 279                         dbg("unable to receive message");
 280                 return;
 281         }
 282         cmsg = CMSG_FIRSTHDR(&smsg);
 283         cred = (struct ucred *) CMSG_DATA(cmsg);
 284
 285         if (cmsg == NULL || cmsg->cmsg_type != SCM_CREDENTIALS) {
 286                 dbg("no sender credentials received, message ignored");
 287                 goto skip;
 288         }
 289
 290         if (cred->uid != 0) {
 291                 dbg("sender uid=%i, message ignored", cred->uid);
 292                 goto skip;
 293         }
 294
 295         if (strncmp(msg->magic, UDEV_MAGIC, sizeof(UDEV_MAGIC)) != 0 ) {
 296                 dbg("message magic '%s' doesn't match, ignore it", msg->magic);
 297                 goto skip;
 298         }
 299
 300         /* if no seqnum is given, we move straight to exec queue */
 301         if (msg->seqnum == -1) {
 302                 list_add(&msg->list, &exec_list);
 303                 run_exec_q = 1;
 304         } else {
 305                 msg_queue_insert(msg);
 306         }
 307         return;
 308
 309 skip:
 310         free(msg);
 311         return;
 312 }
 313
 314 static void sig_handler(int signum)
 315 {
 316         int rc;
 317         switch (signum) {
 318                 case SIGINT:
 319                 case SIGTERM:
 320                         exit(20 + signum);
 321                         break;
 322                 case SIGALRM:
 323                         /* set flag, then write to pipe if needed */
 324                         run_msg_q = 1;
 325                         goto do_write;
 326                         break;
 327                 case SIGCHLD:
 328                         /* set flag, then write to pipe if needed */
 329                         children_waiting = 1;
 330                         goto do_write;
 331                         break;
 332                 default:
 333                         dbg("unhandled signal");
 334                         return;
 335         }
 336
 337 do_write:
 338         /* if pipe is empty, write to pipe to force select to return
 339          * immediately when it gets called
 340          */
 341         if (!sig_flag) {
 342                 rc = write(pipefds[1],&signum,sizeof(signum));
 343                 if (rc < 0)
 344                         dbg("unable to write to pipe");
 345                 else
 346                         sig_flag = 1;
 347         }
 348 }
 349
 350 static void udev_done(int pid)
 351 {
 352         /* find msg associated with pid and delete it */
 353         struct hotplug_msg *msg;
 354
 355         list_for_each_entry(msg, &running_list, list) {
 356                 if (msg->pid == pid) {
 357                         dbg("<== exec seq %d came back", msg->seqnum);
 358                         run_queue_delete(msg);
 359
 360                         /* we want to run the exec queue manager since there may
 361                          * be events waiting with the devpath of the one that
 362                          * just finished
 363                          */
 364                         run_exec_q = 1;
 365                         return;
 366                 }
 367         }
 368 }
 369
 370 static void reap_kids()
 371 {
 372         /* reap all dead children */
 373         while(1) {
 374                 int pid = waitpid(-1, 0, WNOHANG);
 375                 if ((pid == -1) || (pid == 0))
 376                         break;
 377                 udev_done(pid);
 378         }
 379 }
 380
 381 /* just read everything from the pipe and clear the flag,
 382  * the useful flags were set in the signal handler
 383  */
 384 static void user_sighandler()
 385 {
 386         int sig;
 387         while(1) {
 388                 int rc = read(pipefds[0],&sig,sizeof(sig));
 389                 if (rc < 0)
 390                         break;
 391
 392                 sig_flag = 0;
 393         }
 394 }
 395
 396
 397 int main(int argc, char *argv[])
 398 {
 399         int ssock, maxsockplus;
 400         struct sockaddr_un saddr;
 401         socklen_t addrlen;
 402         int retval;
 403         const int on = 1;
 404         struct sigaction act;
 405         fd_set readfds;
 406
 407         init_logging("udevd");
 408         dbg("version %s", UDEV_VERSION);
 409
 410         if (getuid() != 0) {
 411                 dbg("need to be root, exit");
 412                 exit(1);
 413         }
 414
 415         /* setup signal handler pipe */
 416         retval = pipe(pipefds);
 417         if (retval < 0) {
 418                 dbg("error getting pipes: %s", strerror(errno));
 419                 exit(1);
 420         }
 421
 422         retval = fcntl(pipefds[0], F_SETFL, O_NONBLOCK);
 423                 if (retval < 0) {
 424                 dbg("error fcntl on read pipe: %s", strerror(errno));
 425                 exit(1);
 426         }
 427
 428         retval = fcntl(pipefds[1], F_SETFL, O_NONBLOCK);
 429         if (retval < 0) {
 430                 dbg("error fcntl on write pipe: %s", strerror(errno));
 431                 exit(1);
 432         }
 433
 434         /* set signal handlers */
 435         act.sa_handler = sig_handler;
 436         sigemptyset(&act.sa_mask);
 437         act.sa_flags = SA_RESTART;
 438         sigaction(SIGINT, &act, NULL);
 439         sigaction(SIGTERM, &act, NULL);
 440         sigaction(SIGALRM, &act, NULL);
 441         sigaction(SIGCHLD, &act, NULL);
 442
 443         memset(&saddr, 0x00, sizeof(saddr));
 444         saddr.sun_family = AF_LOCAL;
 445         /* use abstract namespace for socket path */
 446         strcpy(&saddr.sun_path[1], UDEVD_SOCK_PATH);
 447         addrlen = offsetof(struct sockaddr_un, sun_path) + strlen(saddr.sun_path+1) + 1;
 448
 449         ssock = socket(AF_LOCAL, SOCK_DGRAM, 0);
 450         if (ssock == -1) {
 451                 dbg("error getting socket, exit");
 452                 exit(1);
 453         }
 454
 455         /* the bind takes care of ensuring only one copy running */
 456         retval = bind(ssock, (struct sockaddr *) &saddr, addrlen);
 457         if (retval < 0) {
 458                 dbg("bind failed, exit");
 459                 goto exit;
 460         }
 461
 462         /* enable receiving of the sender credentials */
 463         setsockopt(ssock, SOL_SOCKET, SO_PASSCRED, &on, sizeof(on));
 464
 465         FD_ZERO(&readfds);
 466         FD_SET(ssock, &readfds);
 467         FD_SET(pipefds[0], &readfds);
 468         maxsockplus = ssock+1;
 469         while (1) {
 470                 fd_set workreadfds = readfds;
 471                 retval = select(maxsockplus, &workreadfds, NULL, NULL, NULL);
 472
 473                 if (retval < 0) {
 474                         if (errno != EINTR)
 475                                 dbg("error in select: %s", strerror(errno));
 476                         continue;
 477                 }
 478
 479                 if (FD_ISSET(ssock, &workreadfds))
 480                         handle_msg(ssock);
 481
 482                 if (FD_ISSET(pipefds[0], &workreadfds))
 483                         user_sighandler();
 484
 485                 if (children_waiting) {
 486                         children_waiting = 0;
 487                         reap_kids();
 488                 }
 489
 490                 if (run_msg_q) {
 491                         run_msg_q = 0;
 492                         msg_queue_manager();
 493                 }
 494
 495                 if (run_exec_q) {
 496                         /* this is tricky.  exec_queue_manager() loops over exec_list, and
 497                          * calls running_with_devpath(), which loops over running_list. This gives
 498                          * O(N*M), which can get *nasty*.  Clean up running_list before
 499                          * calling exec_queue_manager().
 500                          */
 501                         if (children_waiting) {
 502                                 children_waiting = 0;
 503                                 reap_kids();
 504                         }
 505
 506                         run_exec_q = 0;
 507                         exec_queue_manager();
 508                 }
 509         }
 510 exit:
 511         close(ssock);
 512         exit(1);
 513 }