dabbad/misc.c

   1 /* __LICENSE_HEADER_BEGIN__ */
   2
   3 /*
   4  * Copyright (C) 2012   Emmanuel Roullit <emmanuel.roullit@gmail.com>
   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 2 of the License, or (at
   9  * your option) any later version.
  10  *
  11  * This program is distributed in the hope that it will be useful, but
  12  * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
  13  * or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
  14  * for more details.
  15  *
  16  * You should have received a copy of the GNU General Public License along
  17  * with this program; if not, write to the Free Software Foundation, Inc.,
  18  * 51 Franklin St, Fifth Floor, Boston, MA 02110, USA
  19  *
  20  */
  21
  22 /* __LICENSE_HEADER_END__ */
  23
  24 #include <stdio.h>
  25 #include <string.h>
  26 #include <stdlib.h>
  27 #include <assert.h>
  28 #include <errno.h>
  29 #include <sys/types.h>
  30 #include <sys/stat.h>
  31 #include <dirent.h>
  32
  33 #include <dabbacore/strlcpy.h>
  34
  35 #define PROC_FD_PATH "/proc/self/fd/"
  36
  37 int fd_to_path(const int fd, char *path, const size_t path_len)
  38 {
  39         char proc_path[PATH_MAX], fdstr[16];
  40         struct stat fd_stat, path_stat;
  41         DIR *dir;
  42         struct dirent *dir_entry;
  43         char *resolved_path;
  44         int rc = 0;
  45
  46         assert(fd > 0);
  47         assert(path);
  48         assert(path_len);
  49
  50         memset(&proc_path, 0, sizeof(proc_path));
  51         memset(&fd_stat, 0, sizeof(fd_stat));
  52         memset(&resolved_path, 0, sizeof(resolved_path));
  53         memset(&path_stat, 0, sizeof(path_stat));
  54         memset(&fdstr, 0, sizeof(fdstr));
  55
  56         if (snprintf(fdstr, sizeof(fdstr), "%i", fd) <= 0)
  57                 return errno;
  58
  59         dir = opendir(PROC_FD_PATH);
  60
  61         if (!dir)
  62                 return errno;
  63
  64         /* /proc/self/fd/<fdstr> is a symlink to the actual file */
  65         for (dir_entry = readdir(dir); dir_entry; dir_entry = readdir(dir)) {
  66                 if (strcmp(dir_entry->d_name, fdstr) == 0)
  67                         break;
  68         }
  69
  70         if (!dir_entry) {
  71                 rc = ENOENT;
  72                 goto out;
  73         }
  74
  75         if (snprintf
  76             (proc_path, sizeof(proc_path), PROC_FD_PATH "%s",
  77              dir_entry->d_name) <= 0) {
  78                 rc = errno;
  79                 goto out;
  80         }
  81
  82         if (fstat(fd, &fd_stat) < 0 || stat(proc_path, &path_stat) < 0) {
  83                 rc = errno;
  84                 goto out;
  85         }
  86
  87         /* filenames are not accurate, interface and inode ID need to checked too */
  88         if (fd_stat.st_dev != path_stat.st_dev
  89             || fd_stat.st_ino != path_stat.st_ino) {
  90                 rc = EINVAL;
  91                 goto out;
  92         }
  93
  94         /* resolve /proc/self/fd/<fdstr> symlink now */
  95         resolved_path = realpath(proc_path, NULL);
  96
  97         if (!resolved_path) {
  98                 rc = errno;
  99                 goto out;
 100         }
 101
 102         strlcpy(path, resolved_path, path_len);
 103
 104         free(resolved_path);
 105
 106  out:
 107         closedir(dir);
 108         return rc;
 109 }