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
  37 #include "list.h"
  38 #include "udev.h"
  39 #include "udev_version.h"
  40 #include "udevd.h"
  41 #include "logging.h"
  42
  43 static int expected_seqnum = 0;
  44 volatile static int children_waiting;
  45 volatile static int msg_q_timeout;
  46
  47 LIST_HEAD(msg_list);
  48 LIST_HEAD(exec_list);
  49 LIST_HEAD(running_list);
  50
  51 static void exec_queue_manager(void);
  52 static void msg_queue_manager(void);
  53
  54 #ifdef LOG
  55 unsigned char logname[42];
  56 void log_message (int level, const char *format, ...)
  57 {
  58         va_list args;
  59
  60         va_start(args, format);
  61         vsyslog(level, format, args);
  62         va_end(args);
  63 }
  64 #endif
  65
  66 static void msg_dump_queue(void)
  67 {
  68         struct hotplug_msg *msg;
  69
  70         list_for_each_entry(msg, &msg_list, list)
  71                 dbg("sequence %d in queue", msg->seqnum);
  72 }
  73
  74 static void msg_dump(struct hotplug_msg *msg)
  75 {
  76         dbg("sequence %d, '%s', '%s', '%s'",
  77             msg->seqnum, msg->action, msg->devpath, msg->subsystem);
  78 }
  79
  80 static struct hotplug_msg *msg_create(void)
  81 {
  82         struct hotplug_msg *new_msg;
  83
  84         new_msg = malloc(sizeof(struct hotplug_msg));
  85         if (new_msg == NULL)
  86                 dbg("error malloc");
  87         return new_msg;
  88 }
  89
  90 static void run_queue_delete(struct hotplug_msg *msg)
  91 {
  92         list_del(&msg->list);
  93         free(msg);
  94         exec_queue_manager();
  95 }
  96
  97 /* orders the message in the queue by sequence number */
  98 static void msg_queue_insert(struct hotplug_msg *msg)
  99 {
 100         struct hotplug_msg *loop_msg;
 101
 102         /* sort message by sequence number into list*/
 103         list_for_each_entry(loop_msg, &msg_list, list)
 104                 if (loop_msg->seqnum > msg->seqnum)
 105                         break;
 106         list_add_tail(&msg->list, &loop_msg->list);
 107         dbg("queued message seq %d", msg->seqnum);
 108
 109         /* store timestamp of queuing */
 110         msg->queue_time = time(NULL);
 111
 112         /* run msg queue manager */
 113         msg_queue_manager();
 114
 115         return ;
 116 }
 117
 118 /* forks event and removes event from run queue when finished */
 119 static void udev_run(struct hotplug_msg *msg)
 120 {
 121         pid_t pid;
 122         char action[32];
 123         char devpath[256];
 124         char *env[] = { action, devpath, NULL };
 125
 126         snprintf(action, sizeof(action), "ACTION=%s", msg->action);
 127         snprintf(devpath, sizeof(devpath), "DEVPATH=%s", msg->devpath);
 128
 129         pid = fork();
 130         switch (pid) {
 131         case 0:
 132                 /* child */
 133                 execle(UDEV_BIN, "udev", msg->subsystem, NULL, env);
 134                 dbg("exec of child failed");
 135                 exit(1);
 136                 break;
 137         case -1:
 138                 dbg("fork of child failed");
 139                 run_queue_delete(msg);
 140                 break;
 141         default:
 142                 /* get SIGCHLD in main loop */
 143                 dbg("==> exec seq %d [%d] working at '%s'", msg->seqnum, pid, msg->devpath);
 144                 msg->pid = pid;
 145         }
 146 }
 147
 148 /* returns already running task with devpath */
 149 static struct hotplug_msg *running_with_devpath(struct hotplug_msg *msg)
 150 {
 151         struct hotplug_msg *loop_msg;
 152         list_for_each_entry(loop_msg, &running_list, list)
 153                 if (strncmp(loop_msg->devpath, msg->devpath, sizeof(loop_msg->devpath)) == 0)
 154                         return loop_msg;
 155         return NULL;
 156 }
 157
 158 /* exec queue management routine executes the events and delays events for the same devpath */
 159 static void exec_queue_manager()
 160 {
 161         struct hotplug_msg *loop_msg;
 162         struct hotplug_msg *tmp_msg;
 163         struct hotplug_msg *msg;
 164
 165         list_for_each_entry_safe(loop_msg, tmp_msg, &exec_list, list) {
 166                 msg = running_with_devpath(loop_msg);
 167                 if (!msg) {
 168                         /* move event to run list */
 169                         list_move_tail(&loop_msg->list, &running_list);
 170                         udev_run(loop_msg);
 171                         dbg("moved seq %d to running list", loop_msg->seqnum);
 172                 } else {
 173                         dbg("delay seq %d, cause seq %d already working on '%s'",
 174                                 loop_msg->seqnum, msg->seqnum, msg->devpath);
 175                 }
 176         }
 177 }
 178
 179 static void msg_move_exec(struct hotplug_msg *msg)
 180 {
 181         list_move_tail(&msg->list, &exec_list);
 182         exec_queue_manager();
 183         expected_seqnum = msg->seqnum+1;
 184         dbg("moved seq %d to exec, next expected is %d",
 185                 msg->seqnum, expected_seqnum);
 186 }
 187
 188 /* msg queue management routine handles the timeouts and dispatches the events */
 189 static void msg_queue_manager()
 190 {
 191         struct hotplug_msg *loop_msg;
 192         struct hotplug_msg *tmp_msg;
 193         time_t msg_age = 0;
 194
 195         dbg("msg queue manager, next expected is %d", expected_seqnum);
 196 recheck:
 197         list_for_each_entry_safe(loop_msg, tmp_msg, &msg_list, list) {
 198                 /* move event with expected sequence to the exec list */
 199                 if (loop_msg->seqnum == expected_seqnum) {
 200                         msg_move_exec(loop_msg);
 201                         continue;
 202                 }
 203
 204                 /* move event with expired timeout to the exec list */
 205                 msg_age = time(NULL) - loop_msg->queue_time;
 206                 if (msg_age > EVENT_TIMEOUT_SEC-1) {
 207                         msg_move_exec(loop_msg);
 208                         goto recheck;
 209                 } else {
 210                         break;
 211                 }
 212         }
 213
 214         msg_dump_queue();
 215
 216         if (list_empty(&msg_list) == 0) {
 217                 /* set timeout for remaining queued events */
 218                 struct itimerval itv = {{0, 0}, {EVENT_TIMEOUT_SEC - msg_age, 0}};
 219                 dbg("next event expires in %li seconds",
 220                     EVENT_TIMEOUT_SEC - msg_age);
 221                 setitimer(ITIMER_REAL, &itv, 0);
 222         }
 223 }
 224
 225 /* receive the msg, do some basic sanity checks, and queue it */
 226 static void handle_msg(int sock)
 227 {
 228         struct hotplug_msg *msg;
 229         int retval;
 230         struct msghdr smsg;
 231         struct cmsghdr *cmsg;
 232         struct iovec iov;
 233         struct ucred *cred;
 234         char cred_msg[CMSG_SPACE(sizeof(struct ucred))];
 235
 236         msg = msg_create();
 237         if (msg == NULL) {
 238                 dbg("unable to store message");
 239                 return;
 240         }
 241
 242         iov.iov_base = msg;
 243         iov.iov_len = sizeof(struct hotplug_msg);
 244
 245         memset(&smsg, 0x00, sizeof(struct msghdr));
 246         smsg.msg_iov = &iov;
 247         smsg.msg_iovlen = 1;
 248         smsg.msg_control = cred_msg;
 249         smsg.msg_controllen = sizeof(cred_msg);
 250
 251         retval = recvmsg(sock, &smsg, 0);
 252         if (retval <  0) {
 253                 if (errno != EINTR)
 254                         dbg("unable to receive message");
 255                 return;
 256         }
 257         cmsg = CMSG_FIRSTHDR(&smsg);
 258         cred = (struct ucred *) CMSG_DATA(cmsg);
 259
 260         if (cmsg == NULL || cmsg->cmsg_type != SCM_CREDENTIALS) {
 261                 dbg("no sender credentials received, message ignored");
 262                 goto skip;
 263         }
 264
 265         if (cred->uid != 0) {
 266                 dbg("sender uid=%i, message ignored", cred->uid);
 267                 goto skip;
 268         }
 269
 270         if (strncmp(msg->magic, UDEV_MAGIC, sizeof(UDEV_MAGIC)) != 0 ) {
 271                 dbg("message magic '%s' doesn't match, ignore it", msg->magic);
 272                 goto skip;
 273         }
 274
 275         /* if no seqnum is given, we move straight to exec queue */
 276         if (msg->seqnum == -1) {
 277                 list_add(&msg->list, &exec_list);
 278                 exec_queue_manager();
 279         } else {
 280                 msg_queue_insert(msg);
 281         }
 282         return;
 283
 284 skip:
 285         free(msg);
 286         return;
 287 }
 288
 289 static void sig_handler(int signum)
 290 {
 291         switch (signum) {
 292                 case SIGINT:
 293                 case SIGTERM:
 294                         exit(20 + signum);
 295                         break;
 296                 case SIGALRM:
 297                         msg_q_timeout = 1;
 298                         break;
 299                 case SIGCHLD:
 300                         children_waiting = 1;
 301                         break;
 302                 default:
 303                         dbg("unhandled signal");
 304         }
 305 }
 306
 307 static void udev_done(int pid)
 308 {
 309         /* find msg associated with pid and delete it */
 310         struct hotplug_msg *msg;
 311
 312         list_for_each_entry(msg, &running_list, list) {
 313                 if (msg->pid == pid) {
 314                         dbg("<== exec seq %d came back", msg->seqnum);
 315                         run_queue_delete(msg);
 316                         return;
 317                 }
 318         }
 319 }
 320
 321 int main(int argc, char *argv[])
 322 {
 323         int ssock;
 324         struct sockaddr_un saddr;
 325         socklen_t addrlen;
 326         int retval;
 327         const int on = 1;
 328         struct sigaction act;
 329
 330         init_logging("udevd");
 331         dbg("version %s", UDEV_VERSION);
 332
 333         if (getuid() != 0) {
 334                 dbg("need to be root, exit");
 335                 exit(1);
 336         }
 337
 338         /* set signal handler */
 339         act.sa_handler = sig_handler;
 340         sigemptyset (&act.sa_mask);
 341         act.sa_flags = SA_RESTART;
 342         sigaction(SIGINT, &act, NULL);
 343         sigaction(SIGTERM, &act, NULL);
 344
 345         /* we want these two to interrupt system calls */
 346         act.sa_flags = 0;
 347         sigaction(SIGALRM, &act, NULL);
 348         sigaction(SIGCHLD, &act, NULL);
 349
 350         memset(&saddr, 0x00, sizeof(saddr));
 351         saddr.sun_family = AF_LOCAL;
 352         /* use abstract namespace for socket path */
 353         strcpy(&saddr.sun_path[1], UDEVD_SOCK_PATH);
 354         addrlen = offsetof(struct sockaddr_un, sun_path) + strlen(saddr.sun_path+1) + 1;
 355
 356         ssock = socket(AF_LOCAL, SOCK_DGRAM, 0);
 357         if (ssock == -1) {
 358                 dbg("error getting socket, exit");
 359                 exit(1);
 360         }
 361
 362         /* the bind takes care of ensuring only one copy running */
 363         retval = bind(ssock, (struct sockaddr *) &saddr, addrlen);
 364         if (retval < 0) {
 365                 dbg("bind failed, exit");
 366                 goto exit;
 367         }
 368
 369         /* enable receiving of the sender credentials */
 370         setsockopt(ssock, SOL_SOCKET, SO_PASSCRED, &on, sizeof(on));
 371
 372         while (1) {
 373                 handle_msg(ssock);
 374
 375                 while(msg_q_timeout) {
 376                         msg_q_timeout = 0;
 377                         msg_queue_manager();
 378                 }
 379
 380                 while(children_waiting) {
 381                         children_waiting = 0;
 382                         /* reap all dead children */
 383                         while(1) {
 384                                 int pid = waitpid(-1, 0, WNOHANG);
 385                                 if ((pid == -1) || (pid == 0))
 386                                         break;
 387                                 udev_done(pid);
 388                         }
 389                 }
 390         }
 391 exit:
 392         close(ssock);
 393         exit(1);
 394 }