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