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