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 char *udev_bin;
  64
  65 #ifdef LOG
  66 unsigned char logname[LOGNAME_SIZE];
  67 void log_message (int level, const char *format, ...)
  68 {
  69         va_list args;
  70
  71         va_start(args, format);
  72         vsyslog(level, format, args);
  73         va_end(args);
  74 }
  75 #endif
  76
  77 #define msg_dump(msg) \
  78         dbg("msg_dump: sequence %d, '%s', '%s', '%s'", \
  79         msg->seqnum, msg->action, msg->devpath, msg->subsystem);
  80
  81 static void msg_dump_queue(void)
  82 {
  83 #ifdef DEBUG
  84         struct hotplug_msg *msg;
  85
  86         list_for_each_entry(msg, &msg_list, list)
  87                 dbg("sequence %d in queue", msg->seqnum);
  88 #endif
  89 }
  90
  91 static struct hotplug_msg *msg_create(void)
  92 {
  93         struct hotplug_msg *new_msg;
  94
  95         new_msg = malloc(sizeof(struct hotplug_msg));
  96         if (new_msg == NULL)
  97                 dbg("error malloc");
  98         return new_msg;
  99 }
 100
 101 static void run_queue_delete(struct hotplug_msg *msg)
 102 {
 103         list_del(&msg->list);
 104         free(msg);
 105 }
 106
 107 /* orders the message in the queue by sequence number */
 108 static void msg_queue_insert(struct hotplug_msg *msg)
 109 {
 110         struct hotplug_msg *loop_msg;
 111         struct sysinfo info;
 112
 113         /* sort message by sequence number into list. events
 114          * will tend to come in order, so scan the list backwards
 115          */
 116         list_for_each_entry_reverse(loop_msg, &msg_list, list)
 117                 if (loop_msg->seqnum < msg->seqnum)
 118                         break;
 119
 120         /* store timestamp of queuing */
 121         sysinfo(&info);
 122         msg->queue_time = info.uptime;
 123
 124         list_add(&msg->list, &loop_msg->list);
 125         dbg("queued message seq %d", msg->seqnum);
 126
 127         /* run msg queue manager */
 128         run_msg_q = 1;
 129
 130         return ;
 131 }
 132
 133 /* forks event and removes event from run queue when finished */
 134 static void udev_run(struct hotplug_msg *msg)
 135 {
 136         pid_t pid;
 137         char action[ACTION_SIZE];
 138         char devpath[DEVPATH_SIZE];
 139         char *env[] = { action, devpath, NULL };
 140
 141         strcpy(action, "ACTION=");
 142         strfieldcat(action, msg->action);
 143         strcpy(devpath, "DEVPATH=");
 144         strfieldcat(devpath, msg->devpath);
 145
 146         pid = fork();
 147         switch (pid) {
 148         case 0:
 149                 /* child */
 150                 execle(udev_bin, "udev", msg->subsystem, NULL, env);
 151                 dbg("exec of child failed");
 152                 exit(1);
 153                 break;
 154         case -1:
 155                 dbg("fork of child failed");
 156                 run_queue_delete(msg);
 157                 /* note: we never managed to run, so we had no impact on
 158                  * running_with_devpath(), so don't bother setting run_exec_q
 159                  */
 160                 break;
 161         default:
 162                 /* get SIGCHLD in main loop */
 163                 dbg("==> exec seq %d [%d] working at '%s'", msg->seqnum, pid, msg->devpath);
 164                 msg->pid = pid;
 165         }
 166 }
 167
 168 /* returns already running task with devpath */
 169 static struct hotplug_msg *running_with_devpath(struct hotplug_msg *msg)
 170 {
 171         struct hotplug_msg *loop_msg;
 172         list_for_each_entry(loop_msg, &running_list, list)
 173                 if (strncmp(loop_msg->devpath, msg->devpath, sizeof(loop_msg->devpath)) == 0)
 174                         return loop_msg;
 175         return NULL;
 176 }
 177
 178 /* exec queue management routine executes the events and delays events for the same devpath */
 179 static void exec_queue_manager()
 180 {
 181         struct hotplug_msg *loop_msg;
 182         struct hotplug_msg *tmp_msg;
 183         struct hotplug_msg *msg;
 184
 185         list_for_each_entry_safe(loop_msg, tmp_msg, &exec_list, list) {
 186                 msg = running_with_devpath(loop_msg);
 187                 if (!msg) {
 188                         /* move event to run list */
 189                         list_move_tail(&loop_msg->list, &running_list);
 190                         udev_run(loop_msg);
 191                         dbg("moved seq %d to running list", loop_msg->seqnum);
 192                 } else {
 193                         dbg("delay seq %d, cause seq %d already working on '%s'",
 194                                 loop_msg->seqnum, msg->seqnum, msg->devpath);
 195                 }
 196         }
 197 }
 198
 199 static void msg_move_exec(struct hotplug_msg *msg)
 200 {
 201         list_move_tail(&msg->list, &exec_list);
 202         run_exec_q = 1;
 203         expected_seqnum = msg->seqnum+1;
 204         dbg("moved seq %d to exec, next expected is %d",
 205                 msg->seqnum, expected_seqnum);
 206 }
 207
 208 /* msg queue management routine handles the timeouts and dispatches the events */
 209 static void msg_queue_manager()
 210 {
 211         struct hotplug_msg *loop_msg;
 212         struct hotplug_msg *tmp_msg;
 213         struct sysinfo info;
 214         long msg_age = 0;
 215
 216         dbg("msg queue manager, next expected is %d", expected_seqnum);
 217 recheck:
 218         list_for_each_entry_safe(loop_msg, tmp_msg, &msg_list, list) {
 219                 /* move event with expected sequence to the exec list */
 220                 if (loop_msg->seqnum == expected_seqnum) {
 221                         msg_move_exec(loop_msg);
 222                         continue;
 223                 }
 224
 225                 /* move event with expired timeout to the exec list */
 226                 sysinfo(&info);
 227                 msg_age = info.uptime - loop_msg->queue_time;
 228                 dbg("seq %d is %li seconds old", loop_msg->seqnum, msg_age);
 229                 if (msg_age > EVENT_TIMEOUT_SEC-1) {
 230                         msg_move_exec(loop_msg);
 231                         goto recheck;
 232                 } else {
 233                         break;
 234                 }
 235         }
 236
 237         msg_dump_queue();
 238
 239         /* set timeout for remaining queued events */
 240         if (list_empty(&msg_list) == 0) {
 241                 struct itimerval itv = {{0, 0}, {EVENT_TIMEOUT_SEC - msg_age, 0}};
 242                 dbg("next event expires in %li seconds", EVENT_TIMEOUT_SEC - msg_age);
 243                 setitimer(ITIMER_REAL, &itv, 0);
 244         }
 245 }
 246
 247 /* receive the msg, do some basic sanity checks, and queue it */
 248 static void handle_msg(int sock)
 249 {
 250         struct hotplug_msg *msg;
 251         int retval;
 252         struct msghdr smsg;
 253         struct cmsghdr *cmsg;
 254         struct iovec iov;
 255         struct ucred *cred;
 256         char cred_msg[CMSG_SPACE(sizeof(struct ucred))];
 257
 258         msg = msg_create();
 259         if (msg == NULL) {
 260                 dbg("unable to store message");
 261                 return;
 262         }
 263
 264         iov.iov_base = msg;
 265         iov.iov_len = sizeof(struct hotplug_msg);
 266
 267         memset(&smsg, 0x00, sizeof(struct msghdr));
 268         smsg.msg_iov = &iov;
 269         smsg.msg_iovlen = 1;
 270         smsg.msg_control = cred_msg;
 271         smsg.msg_controllen = sizeof(cred_msg);
 272
 273         retval = recvmsg(sock, &smsg, 0);
 274         if (retval <  0) {
 275                 if (errno != EINTR)
 276                         dbg("unable to receive message");
 277                 return;
 278         }
 279         cmsg = CMSG_FIRSTHDR(&smsg);
 280         cred = (struct ucred *) CMSG_DATA(cmsg);
 281
 282         if (cmsg == NULL || cmsg->cmsg_type != SCM_CREDENTIALS) {
 283                 dbg("no sender credentials received, message ignored");
 284                 goto skip;
 285         }
 286
 287         if (cred->uid != 0) {
 288                 dbg("sender uid=%i, message ignored", cred->uid);
 289                 goto skip;
 290         }
 291
 292         if (strncmp(msg->magic, UDEV_MAGIC, sizeof(UDEV_MAGIC)) != 0 ) {
 293                 dbg("message magic '%s' doesn't match, ignore it", msg->magic);
 294                 goto skip;
 295         }
 296
 297         /* if no seqnum is given, we move straight to exec queue */
 298         if (msg->seqnum == -1) {
 299                 list_add(&msg->list, &exec_list);
 300                 run_exec_q = 1;
 301         } else {
 302                 msg_queue_insert(msg);
 303         }
 304         return;
 305
 306 skip:
 307         free(msg);
 308         return;
 309 }
 310
 311 static void sig_handler(int signum)
 312 {
 313         int rc;
 314         switch (signum) {
 315                 case SIGINT:
 316                 case SIGTERM:
 317                         exit(20 + signum);
 318                         break;
 319                 case SIGALRM:
 320                         /* set flag, then write to pipe if needed */
 321                         run_msg_q = 1;
 322                         goto do_write;
 323                         break;
 324                 case SIGCHLD:
 325                         /* set flag, then write to pipe if needed */
 326                         children_waiting = 1;
 327                         goto do_write;
 328                         break;
 329                 default:
 330                         dbg("unhandled signal");
 331                         return;
 332         }
 333
 334 do_write:
 335         /* if pipe is empty, write to pipe to force select to return
 336          * immediately when it gets called
 337          */
 338         if (!sig_flag) {
 339                 rc = write(pipefds[1],&signum,sizeof(signum));
 340                 if (rc < 0)
 341                         dbg("unable to write to pipe");
 342                 else
 343                         sig_flag = 1;
 344         }
 345 }
 346
 347 static void udev_done(int pid)
 348 {
 349         /* find msg associated with pid and delete it */
 350         struct hotplug_msg *msg;
 351
 352         list_for_each_entry(msg, &running_list, list) {
 353                 if (msg->pid == pid) {
 354                         dbg("<== exec seq %d came back", msg->seqnum);
 355                         run_queue_delete(msg);
 356
 357                         /* we want to run the exec queue manager since there may
 358                          * be events waiting with the devpath of the one that
 359                          * just finished
 360                          */
 361                         run_exec_q = 1;
 362                         return;
 363                 }
 364         }
 365 }
 366
 367 static void reap_kids()
 368 {
 369         /* reap all dead children */
 370         while(1) {
 371                 int pid = waitpid(-1, 0, WNOHANG);
 372                 if ((pid == -1) || (pid == 0))
 373                         break;
 374                 udev_done(pid);
 375         }
 376 }
 377
 378 /* just read everything from the pipe and clear the flag,
 379  * the useful flags were set in the signal handler
 380  */
 381 static void user_sighandler()
 382 {
 383         int sig;
 384         while(1) {
 385                 int rc = read(pipefds[0],&sig,sizeof(sig));
 386                 if (rc < 0)
 387                         break;
 388
 389                 sig_flag = 0;
 390         }
 391 }
 392
 393
 394 int main(int argc, char *argv[])
 395 {
 396         int ssock, maxsockplus;
 397         struct sockaddr_un saddr;
 398         socklen_t addrlen;
 399         int retval;
 400         const int on = 1;
 401         struct sigaction act;
 402         fd_set readfds;
 403
 404         init_logging("udevd");
 405         dbg("version %s", UDEV_VERSION);
 406
 407         if (getuid() != 0) {
 408                 dbg("need to be root, exit");
 409                 exit(1);
 410         }
 411
 412         /* setup signal handler pipe */
 413         retval = pipe(pipefds);
 414         if (retval < 0) {
 415                 dbg("error getting pipes: %s", strerror(errno));
 416                 exit(1);
 417         }
 418
 419         retval = fcntl(pipefds[0], F_SETFL, O_NONBLOCK);
 420                 if (retval < 0) {
 421                 dbg("error fcntl on read pipe: %s", strerror(errno));
 422                 exit(1);
 423         }
 424
 425         retval = fcntl(pipefds[1], F_SETFL, O_NONBLOCK);
 426         if (retval < 0) {
 427                 dbg("error fcntl on write pipe: %s", strerror(errno));
 428                 exit(1);
 429         }
 430
 431         /* set signal handlers */
 432         act.sa_handler = sig_handler;
 433         sigemptyset(&act.sa_mask);
 434         act.sa_flags = SA_RESTART;
 435         sigaction(SIGINT, &act, NULL);
 436         sigaction(SIGTERM, &act, NULL);
 437         sigaction(SIGALRM, &act, NULL);
 438         sigaction(SIGCHLD, &act, NULL);
 439
 440         memset(&saddr, 0x00, sizeof(saddr));
 441         saddr.sun_family = AF_LOCAL;
 442         /* use abstract namespace for socket path */
 443         strcpy(&saddr.sun_path[1], UDEVD_SOCK_PATH);
 444         addrlen = offsetof(struct sockaddr_un, sun_path) + strlen(saddr.sun_path+1) + 1;
 445
 446         ssock = socket(AF_LOCAL, SOCK_DGRAM, 0);
 447         if (ssock == -1) {
 448                 dbg("error getting socket, exit");
 449                 exit(1);
 450         }
 451
 452         /* the bind takes care of ensuring only one copy running */
 453         retval = bind(ssock, (struct sockaddr *) &saddr, addrlen);
 454         if (retval < 0) {
 455                 dbg("bind failed, exit");
 456                 goto exit;
 457         }
 458
 459         /* enable receiving of the sender credentials */
 460         setsockopt(ssock, SOL_SOCKET, SO_PASSCRED, &on, sizeof(on));
 461
 462         /* possible override of udev binary, used for testing */
 463         udev_bin = getenv("UDEV_BIN");
 464         if (udev_bin != NULL)
 465                 dbg("udev binary is set to '%s'", udev_bin);
 466         else
 467                 udev_bin = UDEV_BIN;
 468
 469         FD_ZERO(&readfds);
 470         FD_SET(ssock, &readfds);
 471         FD_SET(pipefds[0], &readfds);
 472         maxsockplus = ssock+1;
 473         while (1) {
 474                 fd_set workreadfds = readfds;
 475                 retval = select(maxsockplus, &workreadfds, NULL, NULL, NULL);
 476
 477                 if (retval < 0) {
 478                         if (errno != EINTR)
 479                                 dbg("error in select: %s", strerror(errno));
 480                         continue;
 481                 }
 482
 483                 if (FD_ISSET(ssock, &workreadfds))
 484                         handle_msg(ssock);
 485
 486                 if (FD_ISSET(pipefds[0], &workreadfds))
 487                         user_sighandler();
 488
 489                 if (children_waiting) {
 490                         children_waiting = 0;
 491                         reap_kids();
 492                 }
 493
 494                 if (run_msg_q) {
 495                         run_msg_q = 0;
 496                         msg_queue_manager();
 497                 }
 498
 499                 if (run_exec_q) {
 500                         /* this is tricky.  exec_queue_manager() loops over exec_list, and
 501                          * calls running_with_devpath(), which loops over running_list. This gives
 502                          * O(N*M), which can get *nasty*.  Clean up running_list before
 503                          * calling exec_queue_manager().
 504                          */
 505                         if (children_waiting) {
 506                                 children_waiting = 0;
 507                                 reap_kids();
 508                         }
 509
 510                         run_exec_q = 0;
 511                         exec_queue_manager();
 512                 }
 513         }
 514 exit:
 515         close(ssock);
 516         exit(1);
 517 }