src/bin/lttng/conf.cpp

   1 /*
   2  * Copyright (C) 2011 David Goulet <david.goulet@polymtl.ca>
   3  *
   4  * SPDX-License-Identifier: GPL-2.0-only
   5  *
   6  */
   7
   8 #define _LGPL_SOURCE
   9 #include <limits.h>
  10 #include <stdio.h>
  11 #include <stdlib.h>
  12 #include <string.h>
  13 #include <sys/stat.h>
  14 #include <sys/types.h>
  15 #include <unistd.h>
  16
  17 #include <common/compat/errno.h>
  18 #include <common/common.h>
  19 #include <common/utils.h>
  20
  21 #include "conf.h"
  22
  23 /*
  24  * Returns the path with '/CONFIG_FILENAME' added to it;
  25  * path will be NULL if an error occurs.
  26  */
  27 char *config_get_file_path(const char *path)
  28 {
  29         int ret;
  30         char *file_path;
  31
  32         ret = asprintf(&file_path, "%s/%s", path, CONFIG_FILENAME);
  33         if (ret < 0) {
  34                 ERR("Fail allocating config file path");
  35                 file_path = NULL;
  36         }
  37
  38         return file_path;
  39 }
  40
  41 /*
  42  * Returns an open FILE pointer to the config file;
  43  * on error, NULL is returned.
  44  */
  45 static FILE *open_config(const char *path, const char *mode)
  46 {
  47         FILE *fp = NULL;
  48         char *file_path;
  49
  50         file_path = config_get_file_path(path);
  51         if (file_path == NULL) {
  52                 goto error;
  53         }
  54
  55         fp = fopen(file_path, mode);
  56         if (fp == NULL) {
  57                 goto error;
  58         }
  59
  60 error:
  61         free(file_path);
  62         return fp;
  63 }
  64
  65 /*
  66  * Creates the empty config file at the path.
  67  * On success, returns 0;
  68  * on error, returns -1.
  69  */
  70 static int create_config_file(const char *path)
  71 {
  72         int ret;
  73         FILE *fp;
  74
  75         fp = open_config(path, "w+");
  76         if (fp == NULL) {
  77                 ERR("Unable to create config file");
  78                 ret = -1;
  79                 goto error;
  80         }
  81
  82         ret = fclose(fp);
  83
  84 error:
  85         return ret;
  86 }
  87
  88 /*
  89  * Append data to the config file in file_path
  90  * On success, returns 0;
  91  * on error, returns -1.
  92  */
  93 static int write_config(const char *file_path, size_t size, char *data)
  94 {
  95         FILE *fp;
  96         size_t len;
  97         int ret = 0;
  98
  99         fp = open_config(file_path, "a");
 100         if (fp == NULL) {
 101                 ret = -1;
 102                 goto end;
 103         }
 104
 105         /* Write session name into config file */
 106         len = fwrite(data, size, 1, fp);
 107         if (len != 1) {
 108                 ret = -1;
 109         }
 110         if (fclose(fp)) {
 111                 PERROR("close write_config");
 112         }
 113 end:
 114         return ret;
 115 }
 116
 117 /*
 118  * Destroys directory config and file config.
 119  */
 120 void config_destroy(const char *path)
 121 {
 122         int ret;
 123         char *config_path;
 124
 125         config_path = config_get_file_path(path);
 126         if (config_path == NULL) {
 127                 return;
 128         }
 129
 130         if (!config_exists(config_path)) {
 131                 goto end;
 132         }
 133
 134         DBG("Removing %s\n", config_path);
 135         ret = remove(config_path);
 136         if (ret < 0) {
 137                 PERROR("remove config file");
 138         }
 139 end:
 140         free(config_path);
 141 }
 142
 143 /*
 144  * Destroys the default config
 145  */
 146 void config_destroy_default(void)
 147 {
 148         const char *path = utils_get_home_dir();
 149         if (path == NULL) {
 150                 return;
 151         }
 152         config_destroy(path);
 153 }
 154
 155 /*
 156  * Returns 1 if config exists, 0 otherwise
 157  */
 158 int config_exists(const char *path)
 159 {
 160         int ret;
 161         struct stat info;
 162
 163         ret = stat(path, &info);
 164         if (ret < 0) {
 165                 return 0;
 166         }
 167         return S_ISREG(info.st_mode) || S_ISDIR(info.st_mode);
 168 }
 169
 170 static
 171 int _config_read_session_name(const char *path, char **name)
 172 {
 173         int ret = 0;
 174         FILE *fp;
 175         char var[NAME_MAX], *session_name;
 176
 177 #if (NAME_MAX == 255)
 178 #define NAME_MAX_SCANF_IS_A_BROKEN_API  "254"
 179 #endif
 180
 181         session_name = (char *) zmalloc(NAME_MAX);
 182         if (session_name == NULL) {
 183                 ret = -ENOMEM;
 184                 ERR("Out of memory");
 185                 goto error;
 186         }
 187
 188         fp = open_config(path, "r");
 189         if (fp == NULL) {
 190                 ret = -ENOENT;
 191                 goto error;
 192         }
 193
 194         while (!feof(fp)) {
 195                 if ((ret = fscanf(fp, "%" NAME_MAX_SCANF_IS_A_BROKEN_API
 196                                 "[^'=']=%" NAME_MAX_SCANF_IS_A_BROKEN_API "s\n",
 197                                 var, session_name)) != 2) {
 198                         if (ret == -1) {
 199                                 ERR("Missing session=NAME in config file.");
 200                                 goto error_close;
 201                         }
 202                         continue;
 203                 }
 204
 205                 if (strcmp(var, "session") == 0) {
 206                         goto found;
 207                 }
 208         }
 209
 210 error_close:
 211         if (fclose(fp) < 0) {
 212                 PERROR("close config read session name");
 213         }
 214 error:
 215         free(session_name);
 216         return ret;
 217 found:
 218         *name = session_name;
 219         if (fclose(fp) < 0) {
 220                 PERROR("close config read session name found");
 221         }
 222         return ret;
 223 }
 224
 225 /*
 226  * Returns the session name from the config file.
 227  *
 228  * The caller is responsible for freeing the returned string.
 229  * On error, NULL is returned.
 230  */
 231 char *config_read_session_name(const char *path)
 232 {
 233         int ret;
 234         char *name = NULL;
 235
 236         ret = _config_read_session_name(path, &name);
 237         if (ret == -ENOENT) {
 238                 const char *home_dir = utils_get_home_dir();
 239
 240                 ERR("Can't find valid lttng config %s/.lttngrc", home_dir);
 241                 MSG("Did you create a session? (lttng create <my_session>)");
 242         }
 243
 244         return name;
 245 }
 246
 247 /*
 248  * Returns the session name from the config file. (no warnings/errors emitted)
 249  *
 250  * The caller is responsible for freeing the returned string.
 251  * On error, NULL is returned.
 252  */
 253 char *config_read_session_name_quiet(const char *path)
 254 {
 255         char *name = NULL;
 256
 257         (void) _config_read_session_name(path, &name);
 258         return name;
 259 }
 260
 261 /*
 262  * Write session name option to the config file.
 263  * On success, returns 0;
 264  * on error, returns -1.
 265  */
 266 int config_add_session_name(const char *path, const char *name)
 267 {
 268         int ret;
 269         const char *attr = "session=";
 270         /* Max name len accepted plus attribute's len and the NULL byte. */
 271         char session_name[NAME_MAX + strlen(attr) + 1];
 272
 273         /*
 274          * With GNU C <  2.1, snprintf returns -1 if the target buffer is too small;
 275          * With GNU C >= 2.1, snprintf returns the required size (excluding closing null)
 276          */
 277         ret = snprintf(session_name, sizeof(session_name), "%s%s\n", attr, name);
 278         if (ret < 0) {
 279                 ret = -1;
 280                 goto error;
 281         }
 282         ret = write_config(path, ret, session_name);
 283 error:
 284         return ret;
 285 }
 286
 287 /*
 288  * Init configuration directory and file.
 289  * On success, returns 0;
 290  * on error, returns -1.
 291  */
 292 int config_init(const char *session_name)
 293 {
 294         int ret;
 295         const char *path;
 296
 297         path = utils_get_home_dir();
 298         if (path == NULL) {
 299                 ret = -1;
 300                 goto error;
 301         }
 302
 303         /* Create default config file */
 304         ret = create_config_file(path);
 305         if (ret < 0) {
 306                 goto error;
 307         }
 308
 309         ret = config_add_session_name(path, session_name);
 310         if (ret < 0) {
 311                 goto error;
 312         }
 313
 314         DBG("Init config session in %s", path);
 315
 316 error:
 317         return ret;
 318 }