source3/lib/messages_dgm.c

   1 /*
   2  * Unix SMB/CIFS implementation.
   3  * Samba internal messaging functions
   4  * Copyright (C) 2013 by Volker Lendecke
   5  *
   6  * This program is free software; you can redistribute it and/or modify
   7  * it under the terms of the GNU General Public License as published by
   8  * the Free Software Foundation; either version 3 of the License, or
   9  * (at your option) any later version.
  10  *
  11  * This program is distributed in the hope that it will be useful,
  12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14  * GNU General Public License for more details.
  15  *
  16  * You should have received a copy of the GNU General Public License
  17  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
  18  */
  19
  20 #include "includes.h"
  21 #include "lib/util/data_blob.h"
  22 #include "lib/util/debug.h"
  23 #include "lib/unix_msg/unix_msg.h"
  24 #include "system/filesys.h"
  25 #include "messages.h"
  26 #include "lib/param/param.h"
  27 #include "poll_funcs/poll_funcs_tevent.h"
  28 #include "unix_msg/unix_msg.h"
  29
  30 struct messaging_dgm_context {
  31         struct server_id pid;
  32         struct poll_funcs *msg_callbacks;
  33         void *tevent_handle;
  34         struct unix_msg_ctx *dgm_ctx;
  35         char *cache_dir;
  36         int lockfile_fd;
  37
  38         void (*recv_cb)(int msg_type,
  39                         struct server_id src, struct server_id dst,
  40                         const uint8_t *msg, size_t msg_len,
  41                         void *private_data);
  42         void *recv_cb_private_data;
  43 };
  44
  45 struct messaging_dgm_hdr {
  46         int msg_type;
  47         struct server_id dst;
  48         struct server_id src;
  49 };
  50
  51 static void messaging_dgm_recv(struct unix_msg_ctx *ctx,
  52                                uint8_t *msg, size_t msg_len,
  53                                void *private_data);
  54
  55 static int messaging_dgm_context_destructor(struct messaging_dgm_context *c);
  56
  57 static int messaging_dgm_lockfile_create(TALLOC_CTX *tmp_ctx,
  58                                          const char *cache_dir,
  59                                          uid_t dir_owner, pid_t pid,
  60                                          int *plockfile_fd, uint64_t unique)
  61 {
  62         fstring buf;
  63         char *dir;
  64         char *lockfile_name;
  65         int lockfile_fd;
  66         struct flock lck = {};
  67         int unique_len, ret;
  68         ssize_t written;
  69         bool ok;
  70
  71         dir = talloc_asprintf(tmp_ctx, "%s/lck", cache_dir);
  72         if (dir == NULL) {
  73                 return ENOMEM;
  74         }
  75
  76         ok = directory_create_or_exist_strict(dir, dir_owner, 0755);
  77         if (!ok) {
  78                 ret = errno;
  79                 DEBUG(1, ("%s: Could not create lock directory: %s\n",
  80                           __func__, strerror(ret)));
  81                 TALLOC_FREE(dir);
  82                 return ret;
  83         }
  84
  85         lockfile_name = talloc_asprintf(tmp_ctx, "%s/%u", dir,
  86                                         (unsigned)pid);
  87         TALLOC_FREE(dir);
  88         if (lockfile_name == NULL) {
  89                 DEBUG(1, ("%s: talloc_asprintf failed\n", __func__));
  90                 return ENOMEM;
  91         }
  92
  93         /* no O_EXCL, existence check is via the fcntl lock */
  94
  95         lockfile_fd = open(lockfile_name, O_NONBLOCK|O_CREAT|O_WRONLY, 0644);
  96         if (lockfile_fd == -1) {
  97                 ret = errno;
  98                 DEBUG(1, ("%s: open failed: %s\n", __func__, strerror(errno)));
  99                 goto fail_free;
 100         }
 101
 102         lck.l_type = F_WRLCK;
 103         lck.l_whence = SEEK_SET;
 104         lck.l_start = 0;
 105         lck.l_len = 0;
 106
 107         ret = fcntl(lockfile_fd, F_SETLK, &lck);
 108         if (ret == -1) {
 109                 ret = errno;
 110                 DEBUG(1, ("%s: fcntl failed: %s\n", __func__, strerror(ret)));
 111                 goto fail_close;
 112         }
 113
 114         unique_len = snprintf(buf, sizeof(buf), "%"PRIu64, unique);
 115
 116         /* shorten a potentially preexisting file */
 117
 118         ret = ftruncate(lockfile_fd, unique_len);
 119         if (ret == -1) {
 120                 ret = errno;
 121                 DEBUG(1, ("%s: ftruncate failed: %s\n", __func__,
 122                           strerror(ret)));
 123                 goto fail_unlink;
 124         }
 125
 126         written = write(lockfile_fd, buf, unique_len);
 127         if (written != unique_len) {
 128                 ret = errno;
 129                 DEBUG(1, ("%s: write failed: %s\n", __func__, strerror(ret)));
 130                 goto fail_unlink;
 131         }
 132
 133         TALLOC_FREE(lockfile_name);
 134         *plockfile_fd = lockfile_fd;
 135         return 0;
 136
 137 fail_unlink:
 138         unlink(lockfile_name);
 139 fail_close:
 140         close(lockfile_fd);
 141 fail_free:
 142         TALLOC_FREE(lockfile_name);
 143         return ret;
 144 }
 145
 146 static int messaging_dgm_lockfile_remove(TALLOC_CTX *tmp_ctx,
 147                                          const char *cache_dir, pid_t pid)
 148 {
 149         char *lockfile_name;
 150         int ret;
 151
 152         lockfile_name = talloc_asprintf(
 153                 tmp_ctx, "%s/lck/%u", cache_dir, (unsigned)pid);
 154         if (lockfile_name == NULL) {
 155                 return ENOMEM;
 156         }
 157
 158         ret = unlink(lockfile_name);
 159         if (ret == -1) {
 160                 ret = errno;
 161                 DEBUG(10, ("%s: unlink(%s) failed: %s\n", __func__,
 162                            lockfile_name, strerror(ret)));
 163         }
 164
 165         TALLOC_FREE(lockfile_name);
 166         return ret;
 167 }
 168
 169 int messaging_dgm_init(TALLOC_CTX *mem_ctx,
 170                        struct tevent_context *ev,
 171                        struct server_id pid,
 172                        const char *cache_dir,
 173                        uid_t dir_owner,
 174                        void (*recv_cb)(int msg_type,
 175                                        struct server_id src,
 176                                        struct server_id dst,
 177                                        const uint8_t *msg,
 178                                        size_t msg_len,
 179                                        void *private_data),
 180                        void *recv_cb_private_data,
 181                        struct messaging_dgm_context **pctx)
 182 {
 183         struct messaging_dgm_context *ctx;
 184         int ret;
 185         bool ok;
 186         char *socket_dir;
 187         struct sockaddr_un socket_address;
 188         size_t sockname_len;
 189         uint64_t cookie;
 190
 191         ctx = talloc_zero(mem_ctx, struct messaging_dgm_context);
 192         if (ctx == NULL) {
 193                 goto fail_nomem;
 194         }
 195         ctx->pid = pid;
 196         ctx->recv_cb = recv_cb;
 197         ctx->recv_cb_private_data = recv_cb_private_data;
 198
 199         ctx->cache_dir = talloc_strdup(ctx, cache_dir);
 200         if (ctx->cache_dir == NULL) {
 201                 goto fail_nomem;
 202         }
 203         socket_dir = talloc_asprintf(ctx, "%s/msg", cache_dir);
 204         if (socket_dir == NULL) {
 205                 goto fail_nomem;
 206         }
 207
 208         socket_address = (struct sockaddr_un) { .sun_family = AF_UNIX };
 209         sockname_len = snprintf(socket_address.sun_path,
 210                                 sizeof(socket_address.sun_path),
 211                                 "%s/%u", socket_dir, (unsigned)pid.pid);
 212         if (sockname_len >= sizeof(socket_address.sun_path)) {
 213                 TALLOC_FREE(ctx);
 214                 return ENAMETOOLONG;
 215         }
 216
 217         ret = messaging_dgm_lockfile_create(ctx, cache_dir, dir_owner, pid.pid,
 218                                             &ctx->lockfile_fd, pid.unique_id);
 219         if (ret != 0) {
 220                 DEBUG(1, ("%s: messaging_dgm_create_lockfile failed: %s\n",
 221                           __func__, strerror(ret)));
 222                 TALLOC_FREE(ctx);
 223                 return ret;
 224         }
 225
 226         ctx->msg_callbacks = poll_funcs_init_tevent(ctx);
 227         if (ctx->msg_callbacks == NULL) {
 228                 goto fail_nomem;
 229         }
 230
 231         ctx->tevent_handle = poll_funcs_tevent_register(
 232                 ctx, ctx->msg_callbacks, ev);
 233         if (ctx->tevent_handle == NULL) {
 234                 goto fail_nomem;
 235         }
 236
 237         ok = directory_create_or_exist_strict(socket_dir, dir_owner, 0700);
 238         if (!ok) {
 239                 DEBUG(1, ("Could not create socket directory\n"));
 240                 TALLOC_FREE(ctx);
 241                 return EACCES;
 242         }
 243         TALLOC_FREE(socket_dir);
 244
 245         unlink(socket_address.sun_path);
 246
 247         generate_random_buffer((uint8_t *)&cookie, sizeof(cookie));
 248
 249         ret = unix_msg_init(&socket_address, ctx->msg_callbacks, 1024, cookie,
 250                             messaging_dgm_recv, ctx, &ctx->dgm_ctx);
 251         if (ret != 0) {
 252                 DEBUG(1, ("unix_msg_init failed: %s\n", strerror(ret)));
 253                 TALLOC_FREE(ctx);
 254                 return ret;
 255         }
 256         talloc_set_destructor(ctx, messaging_dgm_context_destructor);
 257
 258         *pctx = ctx;
 259         return 0;
 260
 261 fail_nomem:
 262         TALLOC_FREE(ctx);
 263         return ENOMEM;
 264 }
 265
 266 static int messaging_dgm_context_destructor(struct messaging_dgm_context *c)
 267 {
 268         struct server_id pid = c->pid;
 269
 270         /*
 271          * First delete the socket to avoid races. The lockfile is the
 272          * indicator that we're still around.
 273          */
 274         unix_msg_free(c->dgm_ctx);
 275
 276         if (getpid() == pid.pid) {
 277                 (void)messaging_dgm_lockfile_remove(c, c->cache_dir, pid.pid);
 278         }
 279         close(c->lockfile_fd);
 280         return 0;
 281 }
 282
 283 int messaging_dgm_send(struct messaging_dgm_context *ctx,
 284                        struct server_id src, struct server_id pid,
 285                        int msg_type, const struct iovec *iov, int iovlen)
 286 {
 287         struct messaging_dgm_hdr hdr;
 288         struct iovec iov2[iovlen + 1];
 289         struct server_id_buf idbuf;
 290         struct sockaddr_un dst;
 291         ssize_t dst_pathlen;
 292         int ret;
 293
 294         dst = (struct sockaddr_un) { .sun_family = AF_UNIX };
 295
 296         dst_pathlen = snprintf(dst.sun_path, sizeof(dst.sun_path),
 297                                "%s/msg/%u", ctx->cache_dir, (unsigned)pid.pid);
 298         if (dst_pathlen >= sizeof(dst.sun_path)) {
 299                 return ENAMETOOLONG;
 300         }
 301
 302         hdr.msg_type = msg_type & MSG_TYPE_MASK;
 303         hdr.dst = pid;
 304         hdr.src = src;
 305
 306         DEBUG(10, ("%s: Sending message 0x%x to %s\n", __func__,
 307                    (unsigned)hdr.msg_type,
 308                    server_id_str_buf(pid, &idbuf)));
 309
 310         iov2[0].iov_base = &hdr;
 311         iov2[0].iov_len = sizeof(hdr);
 312         memcpy(iov2+1, iov, iovlen*sizeof(struct iovec));
 313
 314         ret = unix_msg_send(ctx->dgm_ctx, &dst, iov2, iovlen + 1);
 315
 316         return ret;
 317 }
 318
 319 static void messaging_dgm_recv(struct unix_msg_ctx *ctx,
 320                                uint8_t *msg, size_t msg_len,
 321                                void *private_data)
 322 {
 323         struct messaging_dgm_context *dgm_ctx = talloc_get_type_abort(
 324                 private_data, struct messaging_dgm_context);
 325         struct messaging_dgm_hdr *hdr;
 326         struct server_id_buf idbuf;
 327
 328         if (msg_len < sizeof(*hdr)) {
 329                 DEBUG(1, ("message too short: %u\n", (unsigned)msg_len));
 330                 return;
 331         }
 332
 333         /*
 334          * unix_msg guarantees alignment, so we can cast here
 335          */
 336         hdr = (struct messaging_dgm_hdr *)msg;
 337
 338         DEBUG(10, ("%s: Received message 0x%x len %u from %s\n", __func__,
 339                    (unsigned)hdr->msg_type, (unsigned)(msg_len - sizeof(*hdr)),
 340                    server_id_str_buf(hdr->src, &idbuf)));
 341
 342         dgm_ctx->recv_cb(hdr->msg_type, hdr->src, hdr->dst,
 343                          msg + sizeof(*hdr), msg_len - sizeof(*hdr),
 344                          dgm_ctx->recv_cb_private_data);
 345 }
 346
 347 int messaging_dgm_cleanup(struct messaging_dgm_context *ctx, pid_t pid)
 348 {
 349         char *lockfile_name, *socket_name;
 350         int fd, ret;
 351         struct flock lck = {};
 352
 353         lockfile_name = talloc_asprintf(talloc_tos(), "%s/lck/%u",
 354                                         ctx->cache_dir, (unsigned)pid);
 355         if (lockfile_name == NULL) {
 356                 return ENOMEM;
 357         }
 358         socket_name = talloc_asprintf(lockfile_name, "%s/msg/%u",
 359                                       ctx->cache_dir, (unsigned)pid);
 360         if (socket_name == NULL) {
 361                 TALLOC_FREE(lockfile_name);
 362                 return ENOMEM;
 363         }
 364
 365         fd = open(lockfile_name, O_NONBLOCK|O_WRONLY, 0);
 366         if (fd == -1) {
 367                 ret = errno;
 368                 DEBUG(10, ("%s: open(%s) failed: %s\n", __func__,
 369                            lockfile_name, strerror(ret)));
 370                 TALLOC_FREE(lockfile_name);
 371                 return ret;
 372         }
 373
 374         lck.l_type = F_WRLCK;
 375         lck.l_whence = SEEK_SET;
 376         lck.l_start = 0;
 377         lck.l_len = 0;
 378
 379         ret = fcntl(fd, F_SETLK, &lck);
 380         if (ret != 0) {
 381                 ret = errno;
 382                 DEBUG(10, ("%s: Could not get lock: %s\n", __func__,
 383                            strerror(ret)));
 384                 TALLOC_FREE(lockfile_name);
 385                 close(fd);
 386                 return ret;
 387         }
 388
 389         (void)unlink(socket_name);
 390         (void)unlink(lockfile_name);
 391         (void)close(fd);
 392
 393         TALLOC_FREE(lockfile_name);
 394         return 0;
 395 }
 396
 397 int messaging_dgm_wipe(struct messaging_dgm_context *ctx)
 398 {
 399         char *msgdir_name;
 400         DIR *msgdir;
 401         struct dirent *dp;
 402         pid_t our_pid = getpid();
 403         int ret;
 404
 405         /*
 406          * We scan the socket directory and not the lock directory. Otherwise
 407          * we would race against messaging_dgm_lockfile_create's open(O_CREAT)
 408          * and fcntl(SETLK).
 409          */
 410
 411         msgdir_name = talloc_asprintf(talloc_tos(), "%s/msg", ctx->cache_dir);
 412         if (msgdir_name == NULL) {
 413                 return ENOMEM;
 414         }
 415
 416         msgdir = opendir(msgdir_name);
 417         if (msgdir == NULL) {
 418                 ret = errno;
 419                 TALLOC_FREE(msgdir_name);
 420                 return ret;
 421         }
 422         TALLOC_FREE(msgdir_name);
 423
 424         while ((dp = readdir(msgdir)) != NULL) {
 425                 unsigned long pid;
 426
 427                 pid = strtoul(dp->d_name, NULL, 10);
 428                 if (pid == 0) {
 429                         /*
 430                          * . and .. and other malformed entries
 431                          */
 432                         continue;
 433                 }
 434                 if (pid == our_pid) {
 435                         /*
 436                          * fcntl(F_GETLK) will succeed for ourselves, we hold
 437                          * that lock ourselves.
 438                          */
 439                         continue;
 440                 }
 441
 442                 ret = messaging_dgm_cleanup(ctx, pid);
 443                 DEBUG(10, ("messaging_dgm_cleanup(%lu) returned %s\n",
 444                            pid, ret ? strerror(ret) : "ok"));
 445         }
 446         closedir(msgdir);
 447
 448         return 0;
 449 }
 450
 451 void *messaging_dgm_register_tevent_context(TALLOC_CTX *mem_ctx,
 452                                             struct messaging_dgm_context *ctx,
 453                                             struct tevent_context *ev)
 454 {
 455         return poll_funcs_tevent_register(mem_ctx, ctx->msg_callbacks, ev);
 456 }