src/kmsg-syslogd.c

   1 /*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/
   2
   3 /***
   4   This file is part of systemd.
   5
   6   Copyright 2010 Lennart Poettering
   7
   8   systemd is free software; you can redistribute it and/or modify it
   9   under the terms of the GNU General Public License as published by
  10   the Free Software Foundation; either version 2 of the License, or
  11   (at your option) any later version.
  12
  13   systemd is distributed in the hope that it will be useful, but
  14   WITHOUT ANY WARRANTY; without even the implied warranty of
  15   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  16   General Public License for more details.
  17
  18   You should have received a copy of the GNU General Public License
  19   along with systemd; If not, see <http://www.gnu.org/licenses/>.
  20 ***/
  21
  22 #include <sys/socket.h>
  23 #include <sys/types.h>
  24 #include <assert.h>
  25 #include <time.h>
  26 #include <string.h>
  27 #include <stdio.h>
  28 #include <errno.h>
  29 #include <unistd.h>
  30 #include <sys/poll.h>
  31 #include <sys/epoll.h>
  32 #include <sys/un.h>
  33 #include <fcntl.h>
  34 #include <sys/signalfd.h>
  35
  36 #include "util.h"
  37 #include "log.h"
  38 #include "sd-daemon.h"
  39 #include "fdset.h"
  40
  41 #define SERVER_FD_MAX 16
  42
  43 typedef struct Stream Stream;
  44
  45 typedef struct Server {
  46         FDSet *syslog_fds;
  47         int kmsg_fd;
  48         int epoll_fd;
  49         int signal_fd;
  50 } Server;
  51
  52 static void server_done(Server *s) {
  53         assert(s);
  54
  55         if (s->epoll_fd >= 0)
  56                 close_nointr_nofail(s->epoll_fd);
  57
  58         if (s->kmsg_fd >= 0)
  59                 close_nointr_nofail(s->kmsg_fd);
  60
  61         if (s->signal_fd >= 0)
  62                 close_nointr_nofail(s->signal_fd);
  63
  64         if (s->syslog_fds)
  65                 fdset_free(s->syslog_fds);
  66 }
  67
  68 static int server_init(Server *s, unsigned n_sockets) {
  69         int r;
  70         unsigned i;
  71         struct epoll_event ev;
  72         sigset_t mask;
  73
  74         assert(s);
  75         assert(n_sockets > 0);
  76
  77         zero(*s);
  78
  79         s->kmsg_fd = s->signal_fd = -1;
  80
  81         if ((s->epoll_fd = epoll_create1(EPOLL_CLOEXEC)) < 0) {
  82                 r = -errno;
  83                 log_error("Failed to create epoll object: %s", strerror(errno));
  84                 goto fail;
  85         }
  86
  87         if (!(s->syslog_fds = fdset_new())) {
  88                 r = -ENOMEM;
  89                 log_error("Failed to allocate file descriptor set: %s", strerror(errno));
  90                 goto fail;
  91         }
  92
  93         for (i = 0; i < n_sockets; i++) {
  94                 int fd, one = 1;
  95
  96                 fd = SD_LISTEN_FDS_START+i;
  97
  98                 if ((r = sd_is_socket(fd, AF_UNSPEC, SOCK_DGRAM, -1)) < 0) {
  99                         log_error("Failed to determine file descriptor type: %s", strerror(-r));
 100                         goto fail;
 101                 }
 102
 103                 if (!r) {
 104                         log_error("Wrong file descriptor type.");
 105                         r = -EINVAL;
 106                         goto fail;
 107                 }
 108
 109                 if (setsockopt(fd, SOL_SOCKET, SO_PASSCRED, &one, sizeof(one)) < 0)
 110                         log_error("SO_PASSCRED failed: %m");
 111
 112                 zero(ev);
 113                 ev.events = EPOLLIN;
 114                 ev.data.fd = fd;
 115                 if (epoll_ctl(s->epoll_fd, EPOLL_CTL_ADD, fd, &ev) < 0) {
 116                         r = -errno;
 117                         log_error("Failed to add server fd to epoll object: %s", strerror(errno));
 118                         goto fail;
 119                 }
 120
 121                 if ((r = fdset_put(s->syslog_fds, fd)) < 0) {
 122                         log_error("Failed to store file descriptor in set: %s", strerror(-r));
 123                         goto fail;
 124                 }
 125         }
 126
 127         if ((s->kmsg_fd = open("/dev/kmsg", O_WRONLY|O_NOCTTY|O_CLOEXEC)) < 0) {
 128                 log_error("Failed to open /dev/kmsg for logging: %m");
 129                 return -errno;
 130         }
 131
 132         assert_se(sigemptyset(&mask) == 0);
 133         sigset_add_many(&mask, SIGINT, SIGTERM, -1);
 134         assert_se(sigprocmask(SIG_SETMASK, &mask, NULL) == 0);
 135
 136         if ((s->signal_fd = signalfd(-1, &mask, SFD_NONBLOCK|SFD_CLOEXEC)) < 0) {
 137                 log_error("signalfd(): %m");
 138                 return -errno;
 139         }
 140
 141         zero(ev);
 142         ev.events = EPOLLIN;
 143         ev.data.fd = s->signal_fd;
 144
 145         if (epoll_ctl(s->epoll_fd, EPOLL_CTL_ADD, s->signal_fd, &ev) < 0) {
 146                 log_error("epoll_ctl(): %m");
 147                 return -errno;
 148         }
 149
 150         return 0;
 151
 152 fail:
 153         server_done(s);
 154         return r;
 155 }
 156
 157 static void skip_date(const char **buf) {
 158         enum {
 159                 LETTER,
 160                 SPACE,
 161                 NUMBER,
 162                 SPACE_OR_NUMBER,
 163                 COLON
 164         } sequence[] = {
 165                 LETTER, LETTER, LETTER,
 166                 SPACE,
 167                 SPACE_OR_NUMBER, NUMBER,
 168                 SPACE,
 169                 SPACE_OR_NUMBER, NUMBER,
 170                 COLON,
 171                 SPACE_OR_NUMBER, NUMBER,
 172                 COLON,
 173                 SPACE_OR_NUMBER, NUMBER,
 174                 SPACE
 175         };
 176
 177         const char *p;
 178         unsigned i;
 179
 180         assert(buf);
 181         assert(*buf);
 182
 183         p = *buf;
 184
 185         for (i = 0; i < ELEMENTSOF(sequence); i++, p++) {
 186
 187                 if (!*p)
 188                         return;
 189
 190                 switch (sequence[i]) {
 191
 192                 case SPACE:
 193                         if (*p != ' ')
 194                                 return;
 195                         break;
 196
 197                 case SPACE_OR_NUMBER:
 198                         if (*p == ' ')
 199                                 break;
 200
 201                         /* fall through */
 202
 203                 case NUMBER:
 204                         if (*p < '0' || *p > '9')
 205                                 return;
 206
 207                         break;
 208
 209                 case LETTER:
 210                         if (!(*p >= 'A' && *p <= 'Z') &&
 211                             !(*p >= 'a' && *p <= 'z'))
 212                                 return;
 213
 214                         break;
 215
 216                 case COLON:
 217                         if (*p != ':')
 218                                 return;
 219                         break;
 220
 221                 }
 222         }
 223
 224         *buf = p;
 225 }
 226
 227 static int read_process(const char **buf, struct iovec *iovec) {
 228         const char *p;
 229         size_t l;
 230
 231         assert(buf);
 232         assert(*buf);
 233         assert(iovec);
 234
 235         p = *buf;
 236
 237         p += strspn(p, WHITESPACE);
 238         l = strcspn(p, WHITESPACE);
 239
 240         if (l <= 0 ||
 241             p[l-1] != ':')
 242                 return 0;
 243
 244         l--;
 245
 246         if (p[l-1] == ']') {
 247                 size_t k = l-1;
 248
 249                 for (;;) {
 250
 251                         if (p[k] == '[') {
 252                                 l = k;
 253                                 break;
 254                         }
 255
 256                         if (k == 0)
 257                                 break;
 258
 259                         k--;
 260                 }
 261         }
 262
 263         iovec->iov_base = (char*) p;
 264         iovec->iov_len = l;
 265         *buf = p + l;
 266         return 1;
 267 }
 268
 269 static void skip_pid(const char **buf) {
 270         const char *p;
 271
 272         assert(buf);
 273         assert(*buf);
 274
 275         p = *buf;
 276
 277         if (*p != '[')
 278                 return;
 279
 280         p++;
 281         p += strspn(p, "0123456789");
 282
 283         if (*p != ']')
 284                 return;
 285
 286         p++;
 287
 288         *buf = p;
 289 }
 290
 291 static int write_message(Server *s, const char *buf, struct ucred *ucred) {
 292         ssize_t k;
 293         char priority[6], pid[16];
 294         struct iovec iovec[5];
 295         unsigned i = 0;
 296         char *process = NULL;
 297         int r = 0;
 298         int prio = LOG_USER | LOG_INFO;
 299
 300         assert(s);
 301         assert(buf);
 302
 303         parse_syslog_priority((char**) &buf, &prio);
 304
 305         if (*buf == 0)
 306                 return 0;
 307
 308         if ((prio & LOG_FACMASK) == 0)
 309                 prio = LOG_USER | LOG_PRI(prio);
 310
 311         /* First, set priority field */
 312         snprintf(priority, sizeof(priority), "<%i>", prio);
 313         char_array_0(priority);
 314         IOVEC_SET_STRING(iovec[i++], priority);
 315
 316         /* Second, skip date */
 317         skip_date(&buf);
 318
 319         /* Then, add process if set */
 320         if (read_process(&buf, &iovec[i]) > 0)
 321                 i++;
 322         else if (ucred &&
 323                  ucred->pid > 0 &&
 324                  get_process_name(ucred->pid, &process) >= 0)
 325                 IOVEC_SET_STRING(iovec[i++], process);
 326
 327         /* Skip the stored PID if we have a better one */
 328         if (ucred) {
 329                 snprintf(pid, sizeof(pid), "[%lu]: ", (unsigned long) ucred->pid);
 330                 char_array_0(pid);
 331                 IOVEC_SET_STRING(iovec[i++], pid);
 332
 333                 skip_pid(&buf);
 334
 335                 if (*buf == ':')
 336                         buf++;
 337
 338                 buf += strspn(buf, WHITESPACE);
 339         }
 340
 341         /* Is the remaining message empty? */
 342         if (*buf) {
 343
 344                 /* And the rest is the message */
 345                 IOVEC_SET_STRING(iovec[i++], buf);
 346                 IOVEC_SET_STRING(iovec[i++], "\n");
 347
 348                 if ((k = writev(s->kmsg_fd, iovec, i)) <= 0) {
 349                         log_error("Failed to write log message to kmsg: %s", k < 0 ? strerror(errno) : "short write");
 350                         r = k < 0 ? -errno : -EIO;
 351                 }
 352         }
 353
 354         free(process);
 355
 356         return r;
 357 }
 358
 359 static int process_event(Server *s, struct epoll_event *ev) {
 360         assert(s);
 361
 362         if (ev->events != EPOLLIN) {
 363                 log_info("Got invalid event from epoll.");
 364                 return -EIO;
 365         }
 366
 367         if (ev->data.fd == s->signal_fd) {
 368                 struct signalfd_siginfo sfsi;
 369                 ssize_t n;
 370
 371                 if ((n = read(s->signal_fd, &sfsi, sizeof(sfsi))) != sizeof(sfsi)) {
 372
 373                         if (n >= 0)
 374                                 return -EIO;
 375
 376                         if (errno == EINTR || errno == EAGAIN)
 377                                 return 0;
 378
 379                         return -errno;
 380                 }
 381
 382                 log_debug("Received SIG%s", strna(signal_to_string(sfsi.ssi_signo)));
 383                 return 0;
 384
 385         } else {
 386                 for (;;) {
 387                         char buf[LINE_MAX+1];
 388                         struct msghdr msghdr;
 389                         struct iovec iovec;
 390                         struct ucred *ucred;
 391                         union {
 392                                 struct cmsghdr cmsghdr;
 393                                 uint8_t buf[CMSG_SPACE(sizeof(struct ucred))];
 394                         } control;
 395                         ssize_t n;
 396                         int k;
 397                         char *e;
 398
 399                         zero(iovec);
 400                         iovec.iov_base = buf;
 401                         iovec.iov_len = sizeof(buf)-1;
 402
 403                         zero(control);
 404                         zero(msghdr);
 405                         msghdr.msg_iov = &iovec;
 406                         msghdr.msg_iovlen = 1;
 407                         msghdr.msg_control = &control;
 408                         msghdr.msg_controllen = sizeof(control);
 409
 410                         if ((n = recvmsg(ev->data.fd, &msghdr, MSG_DONTWAIT)) < 0) {
 411
 412                                 if (errno == EINTR || errno == EAGAIN)
 413                                         return 1;
 414
 415                                 log_error("recvmsg() failed: %m");
 416                                 return -errno;
 417                         }
 418
 419                         if (msghdr.msg_controllen >= CMSG_LEN(sizeof(struct ucred)) &&
 420                             control.cmsghdr.cmsg_level == SOL_SOCKET &&
 421                             control.cmsghdr.cmsg_type == SCM_CREDENTIALS &&
 422                             control.cmsghdr.cmsg_len == CMSG_LEN(sizeof(struct ucred)))
 423                                 ucred = (struct ucred*) CMSG_DATA(&control.cmsghdr);
 424                         else
 425                                 ucred = NULL;
 426
 427                         if ((e = memchr(buf, '\n', n)))
 428                                 *e = 0;
 429                         else
 430                                 buf[n] = 0;
 431
 432                         if ((k = write_message(s, strstrip(buf), ucred)) < 0)
 433                                 return k;
 434                 }
 435         }
 436
 437         return 1;
 438 }
 439
 440 int main(int argc, char *argv[]) {
 441         Server server;
 442         int r = EXIT_FAILURE, n;
 443
 444         if (getppid() != 1) {
 445                 log_error("This program should be invoked by init only.");
 446                 return EXIT_FAILURE;
 447         }
 448
 449         if (argc > 1) {
 450                 log_error("This program does not take arguments.");
 451                 return EXIT_FAILURE;
 452         }
 453
 454         log_set_target(LOG_TARGET_KMSG);
 455         log_parse_environment();
 456         log_open();
 457
 458         if ((n = sd_listen_fds(true)) < 0) {
 459                 log_error("Failed to read listening file descriptors from environment: %s", strerror(-r));
 460                 return EXIT_FAILURE;
 461         }
 462
 463         if (n <= 0 || n > SERVER_FD_MAX) {
 464                 log_error("No or too many file descriptors passed.");
 465                 return EXIT_FAILURE;
 466         }
 467
 468         if (server_init(&server, (unsigned) n) < 0)
 469                 return EXIT_FAILURE;
 470
 471         log_debug("systemd-kmsg-syslogd running as pid %lu", (unsigned long) getpid());
 472
 473         sd_notify(false,
 474                   "READY=1\n"
 475                   "STATUS=Processing messages...");
 476
 477         for (;;) {
 478                 struct epoll_event event;
 479                 int k;
 480
 481                 if ((k = epoll_wait(server.epoll_fd, &event, 1, -1)) < 0) {
 482
 483                         if (errno == EINTR)
 484                                 continue;
 485
 486                         log_error("epoll_wait() failed: %m");
 487                         goto fail;
 488                 }
 489
 490                 if (k <= 0)
 491                         break;
 492
 493                 if ((k = process_event(&server, &event)) < 0)
 494                         goto fail;
 495
 496                 if (k == 0)
 497                         break;
 498         }
 499
 500         r = EXIT_SUCCESS;
 501
 502         log_debug("systemd-kmsg-syslogd stopped as pid %lu", (unsigned long) getpid());
 503
 504 fail:
 505         sd_notify(false,
 506                   "STATUS=Shutting down...");
 507
 508         server_done(&server);
 509
 510         return r;
 511 }