src/bin/lttng-sessiond/session.c

   1 /*
   2  * Copyright (C)  2011 - David Goulet <david.goulet@polymtl.ca>
   3  *
   4  * This program is free software; you can redistribute it and/or modify
   5  * it under the terms of the GNU General Public License, version 2 only,
   6  * as published by the Free Software Foundation.
   7  *
   8  * This program is distributed in the hope that it will be useful,
   9  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  10  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  11  * GNU General Public License for more details.
  12  *
  13  * You should have received a copy of the GNU General Public License along
  14  * with this program; if not, write to the Free Software Foundation, Inc.,
  15  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  16  */
  17
  18 #define _LGPL_SOURCE
  19 #include <limits.h>
  20 #include <inttypes.h>
  21 #include <stdio.h>
  22 #include <stdlib.h>
  23 #include <string.h>
  24 #include <sys/stat.h>
  25 #include <urcu.h>
  26 #include <dirent.h>
  27 #include <sys/types.h>
  28
  29 #include <common/common.h>
  30 #include <common/sessiond-comm/sessiond-comm.h>
  31
  32 #include "session.h"
  33 #include "utils.h"
  34
  35 /*
  36  * NOTES:
  37  *
  38  * No ltt_session.lock is taken here because those data structure are widely
  39  * spread across the lttng-tools code base so before caling functions below
  40  * that can read/write a session, the caller MUST acquire the session lock
  41  * using session_lock() and session_unlock().
  42  */
  43
  44 /*
  45  * Init tracing session list.
  46  *
  47  * Please see session.h for more explanation and correct usage of the list.
  48  */
  49 static struct ltt_session_list ltt_session_list = {
  50         .head = CDS_LIST_HEAD_INIT(ltt_session_list.head),
  51         .lock = PTHREAD_MUTEX_INITIALIZER,
  52         .next_uuid = 0,
  53 };
  54
  55 /* These characters are forbidden in a session name. Used by validate_name. */
  56 static const char *forbidden_name_chars = "/";
  57
  58 /* Global hash table to keep the sessions, indexed by id. */
  59 static struct lttng_ht *ltt_sessions_ht_by_id = NULL;
  60
  61 /*
  62  * Validate the session name for forbidden characters.
  63  *
  64  * Return 0 on success else -1 meaning a forbidden char. has been found.
  65  */
  66 static int validate_name(const char *name)
  67 {
  68         int ret;
  69         char *tok, *tmp_name;
  70
  71         assert(name);
  72
  73         tmp_name = strdup(name);
  74         if (!tmp_name) {
  75                 /* ENOMEM here. */
  76                 ret = -1;
  77                 goto error;
  78         }
  79
  80         tok = strpbrk(tmp_name, forbidden_name_chars);
  81         if (tok) {
  82                 DBG("Session name %s contains a forbidden character", name);
  83                 /* Forbidden character has been found. */
  84                 ret = -1;
  85                 goto error;
  86         }
  87         ret = 0;
  88
  89 error:
  90         free(tmp_name);
  91         return ret;
  92 }
  93
  94 /*
  95  * Add a ltt_session structure to the global list.
  96  *
  97  * The caller MUST acquire the session list lock before.
  98  * Returns the unique identifier for the session.
  99  */
 100 static uint64_t add_session_list(struct ltt_session *ls)
 101 {
 102         assert(ls);
 103
 104         cds_list_add(&ls->list, &ltt_session_list.head);
 105         return ltt_session_list.next_uuid++;
 106 }
 107
 108 /*
 109  * Delete a ltt_session structure to the global list.
 110  *
 111  * The caller MUST acquire the session list lock before.
 112  */
 113 static void del_session_list(struct ltt_session *ls)
 114 {
 115         assert(ls);
 116
 117         cds_list_del(&ls->list);
 118 }
 119
 120 /*
 121  * Return a pointer to the session list.
 122  */
 123 struct ltt_session_list *session_get_list(void)
 124 {
 125         return &ltt_session_list;
 126 }
 127
 128 /*
 129  * Acquire session list lock
 130  */
 131 void session_lock_list(void)
 132 {
 133         pthread_mutex_lock(&ltt_session_list.lock);
 134 }
 135
 136 /*
 137  * Release session list lock
 138  */
 139 void session_unlock_list(void)
 140 {
 141         pthread_mutex_unlock(&ltt_session_list.lock);
 142 }
 143
 144 /*
 145  * Allocate the ltt_sessions_ht_by_id HT.
 146  *
 147  * The session list lock must be held.
 148  */
 149 int ltt_sessions_ht_alloc(void)
 150 {
 151         int ret = 0;
 152
 153         DBG("Allocating ltt_sessions_ht_by_id");
 154         ltt_sessions_ht_by_id = lttng_ht_new(0, LTTNG_HT_TYPE_U64);
 155         if (!ltt_sessions_ht_by_id) {
 156                 ret = -1;
 157                 ERR("Failed to allocate ltt_sessions_ht_by_id");
 158                 goto end;
 159         }
 160 end:
 161         return ret;
 162 }
 163
 164 /*
 165  * Destroy the ltt_sessions_ht_by_id HT.
 166  *
 167  * The session list lock must be held.
 168  */
 169 static void ltt_sessions_ht_destroy(void)
 170 {
 171         if (!ltt_sessions_ht_by_id) {
 172                 return;
 173         }
 174         ht_cleanup_push(ltt_sessions_ht_by_id);
 175         ltt_sessions_ht_by_id = NULL;
 176 }
 177
 178 /*
 179  * Add a ltt_session to the ltt_sessions_ht_by_id.
 180  * If unallocated, the ltt_sessions_ht_by_id HT is allocated.
 181  * The session list lock must be held.
 182  */
 183 static void add_session_ht(struct ltt_session *ls)
 184 {
 185         int ret;
 186
 187         assert(ls);
 188
 189         if (!ltt_sessions_ht_by_id) {
 190                 ret = ltt_sessions_ht_alloc();
 191                 if (ret) {
 192                         ERR("Error allocating the sessions HT");
 193                         goto end;
 194                 }
 195         }
 196         lttng_ht_node_init_u64(&ls->node, ls->id);
 197         lttng_ht_add_unique_u64(ltt_sessions_ht_by_id, &ls->node);
 198
 199 end:
 200         return;
 201 }
 202
 203 /*
 204  * Test if ltt_sessions_ht_by_id is empty.
 205  * Return 1 if empty, 0 if not empty.
 206  * The session list lock must be held.
 207  */
 208 static int ltt_sessions_ht_empty(void)
 209 {
 210         int ret;
 211
 212         if (!ltt_sessions_ht_by_id) {
 213                 ret = 1;
 214                 goto end;
 215         }
 216
 217         ret = lttng_ht_get_count(ltt_sessions_ht_by_id) ? 0 : 1;
 218 end:
 219         return ret;
 220 }
 221
 222 /*
 223  * Remove a ltt_session from the ltt_sessions_ht_by_id.
 224  * If empty, the ltt_sessions_ht_by_id HT is freed.
 225  * The session list lock must be held.
 226  */
 227 static void del_session_ht(struct ltt_session *ls)
 228 {
 229         struct lttng_ht_iter iter;
 230         int ret;
 231
 232         assert(ls);
 233         assert(ltt_sessions_ht_by_id);
 234
 235         iter.iter.node = &ls->node.node;
 236         ret = lttng_ht_del(ltt_sessions_ht_by_id, &iter);
 237         assert(!ret);
 238
 239         if (ltt_sessions_ht_empty()) {
 240                 DBG("Empty ltt_sessions_ht_by_id, destroying it");
 241                 ltt_sessions_ht_destroy();
 242         }
 243 }
 244
 245 /*
 246  * Acquire session lock
 247  */
 248 void session_lock(struct ltt_session *session)
 249 {
 250         assert(session);
 251
 252         pthread_mutex_lock(&session->lock);
 253 }
 254
 255 /*
 256  * Release session lock
 257  */
 258 void session_unlock(struct ltt_session *session)
 259 {
 260         assert(session);
 261
 262         pthread_mutex_unlock(&session->lock);
 263 }
 264
 265 /*
 266  * Return a ltt_session structure ptr that matches name. If no session found,
 267  * NULL is returned. This must be called with the session list lock held using
 268  * session_lock_list and session_unlock_list.
 269  */
 270 struct ltt_session *session_find_by_name(const char *name)
 271 {
 272         struct ltt_session *iter;
 273
 274         assert(name);
 275
 276         DBG2("Trying to find session by name %s", name);
 277
 278         cds_list_for_each_entry(iter, &ltt_session_list.head, list) {
 279                 if (strncmp(iter->name, name, NAME_MAX) == 0) {
 280                         goto found;
 281                 }
 282         }
 283
 284         iter = NULL;
 285
 286 found:
 287         return iter;
 288 }
 289
 290 /*
 291  * Return an ltt_session that matches the id. If no session is found,
 292  * NULL is returned. This must be called with rcu_read_lock and
 293  * session list lock held (to guarantee the lifetime of the session).
 294  */
 295 struct ltt_session *session_find_by_id(uint64_t id)
 296 {
 297         struct lttng_ht_node_u64 *node;
 298         struct lttng_ht_iter iter;
 299         struct ltt_session *ls;
 300
 301         if (!ltt_sessions_ht_by_id) {
 302                 goto end;
 303         }
 304
 305         lttng_ht_lookup(ltt_sessions_ht_by_id, &id, &iter);
 306         node = lttng_ht_iter_get_node_u64(&iter);
 307         if (node == NULL) {
 308                 goto end;
 309         }
 310         ls = caa_container_of(node, struct ltt_session, node);
 311
 312         DBG3("Session %" PRIu64 " found by id.", id);
 313         return ls;
 314
 315 end:
 316         DBG3("Session %" PRIu64 " NOT found by id", id);
 317         return NULL;
 318 }
 319
 320 /*
 321  * Delete session from the session list and free the memory.
 322  *
 323  * Return -1 if no session is found.  On success, return 1;
 324  * Should *NOT* be called with RCU read-side lock held.
 325  */
 326 int session_destroy(struct ltt_session *session)
 327 {
 328         /* Safety check */
 329         assert(session);
 330
 331         DBG("Destroying session %s (id %" PRIu64 ")", session->name, session->id);
 332         del_session_list(session);
 333         pthread_mutex_destroy(&session->lock);
 334         del_session_ht(session);
 335
 336         consumer_output_put(session->consumer);
 337         snapshot_destroy(&session->snapshot);
 338         free(session);
 339
 340         return LTTNG_OK;
 341 }
 342
 343 /*
 344  * Create a brand new session and add it to the session list.
 345  */
 346 int session_create(char *name, uid_t uid, gid_t gid)
 347 {
 348         int ret;
 349         struct ltt_session *new_session;
 350
 351         /* Allocate session data structure */
 352         new_session = zmalloc(sizeof(struct ltt_session));
 353         if (new_session == NULL) {
 354                 PERROR("zmalloc");
 355                 ret = LTTNG_ERR_FATAL;
 356                 goto error_malloc;
 357         }
 358
 359         /* Define session name */
 360         if (name != NULL) {
 361                 if (snprintf(new_session->name, NAME_MAX, "%s", name) < 0) {
 362                         ret = LTTNG_ERR_FATAL;
 363                         goto error_asprintf;
 364                 }
 365         } else {
 366                 ERR("No session name given");
 367                 ret = LTTNG_ERR_FATAL;
 368                 goto error;
 369         }
 370
 371         ret = validate_name(name);
 372         if (ret < 0) {
 373                 ret = LTTNG_ERR_SESSION_INVALID_CHAR;
 374                 goto error;
 375         }
 376
 377         ret = gethostname(new_session->hostname, sizeof(new_session->hostname));
 378         if (ret < 0) {
 379                 if (errno == ENAMETOOLONG) {
 380                         new_session->hostname[sizeof(new_session->hostname) - 1] = '\0';
 381                 } else {
 382                         ret = LTTNG_ERR_FATAL;
 383                         goto error;
 384                 }
 385         }
 386
 387         /* Init kernel session */
 388         new_session->kernel_session = NULL;
 389         new_session->ust_session = NULL;
 390
 391         /* Init lock */
 392         pthread_mutex_init(&new_session->lock, NULL);
 393
 394         new_session->uid = uid;
 395         new_session->gid = gid;
 396
 397         ret = snapshot_init(&new_session->snapshot);
 398         if (ret < 0) {
 399                 ret = LTTNG_ERR_NOMEM;
 400                 goto error;
 401         }
 402
 403         new_session->rotate_pending = false;
 404         new_session->rotate_pending_relay = false;
 405         new_session->rotate_relay_pending_timer_enabled = false;
 406
 407         /* Add new session to the session list */
 408         session_lock_list();
 409         new_session->id = add_session_list(new_session);
 410         /*
 411          * Add the new session to the ltt_sessions_ht_by_id.
 412          * No ownership is taken by the hash table; it is merely
 413          * a wrapper around the session list used for faster access
 414          * by session id.
 415          */
 416         add_session_ht(new_session);
 417         session_unlock_list();
 418
 419         /*
 420          * Consumer is let to NULL since the create_session_uri command will set it
 421          * up and, if valid, assign it to the session.
 422          */
 423         DBG("Tracing session %s created with ID %" PRIu64 " by UID %d GID %d",
 424                         name, new_session->id, new_session->uid, new_session->gid);
 425
 426         return LTTNG_OK;
 427
 428 error:
 429 error_asprintf:
 430         free(new_session);
 431
 432 error_malloc:
 433         return ret;
 434 }
 435
 436 /*
 437  * Check if the UID or GID match the session. Root user has access to all
 438  * sessions.
 439  */
 440 int session_access_ok(struct ltt_session *session, uid_t uid, gid_t gid)
 441 {
 442         assert(session);
 443
 444         if (uid != session->uid && gid != session->gid && uid != 0) {
 445                 return 0;
 446         } else {
 447                 return 1;
 448         }
 449 }