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