dabbad/misc.c

   1 /**
   2  * \file misc.c
   3  * \author written by Emmanuel Roullit emmanuel.roullit@gmail.com (c) 2012
   4  * \date 2012
   5  */
   6
   7 /* __LICENSE_HEADER_BEGIN__ */
   8
   9 /*
  10  * Copyright (C) 2012   Emmanuel Roullit <emmanuel.roullit@gmail.com>
  11  *
  12  * This program is free software; you can redistribute it and/or modify
  13  * it under the terms of the GNU General Public License as published by
  14  * the Free Software Foundation; either version 2 of the License, or (at
  15  * your option) any later version.
  16  *
  17  * This program is distributed in the hope that it will be useful, but
  18  * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
  19  * or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
  20  * for more details.
  21  *
  22  * You should have received a copy of the GNU General Public License along
  23  * with this program; if not, write to the Free Software Foundation, Inc.,
  24  * 51 Franklin St, Fifth Floor, Boston, MA 02110, USA
  25  *
  26  */
  27
  28 /* __LICENSE_HEADER_END__ */
  29
  30 #include <stdio.h>
  31 #include <string.h>
  32 #include <stdlib.h>
  33 #include <assert.h>
  34 #include <errno.h>
  35 #include <sys/types.h>
  36 #include <sys/stat.h>
  37 #include <dirent.h>
  38
  39 #include <libdabba/strlcpy.h>
  40
  41 /**
  42  * \brief Path to current process open file descriptor information
  43  */
  44
  45 #define PROC_FD_PATH "/proc/self/fd/"
  46
  47 /**
  48  * \brief Get file path from an open file descriptor
  49  * \param[in]           fd              File descriptor
  50  * \param[out]          path            Pointer to the path string buffer
  51  * \param[in]           path_len        Path string buffer size in bytes
  52  * \return 0 on success, else on failure.
  53  *
  54  * This function retrieves the absolute path of a file from its file descriptor.
  55  * It mainly checks the device/inode numbers of the file descriptor and the file
  56  * to correlate them.
  57  */
  58
  59 int fd_to_path(const int fd, char *path, const size_t path_len)
  60 {
  61         char proc_path[PATH_MAX], fdstr[16];
  62         struct stat fd_stat, path_stat;
  63         DIR *dir;
  64         struct dirent *dir_entry;
  65         char *resolved_path;
  66         int rc = 0;
  67
  68         assert(fd > 0);
  69         assert(path);
  70         assert(path_len);
  71
  72         memset(proc_path, 0, sizeof(proc_path));
  73         memset(fdstr, 0, sizeof(fdstr));
  74         memset(&fd_stat, 0, sizeof(fd_stat));
  75         memset(&resolved_path, 0, sizeof(resolved_path));
  76         memset(&path_stat, 0, sizeof(path_stat));
  77
  78         if (snprintf(fdstr, sizeof(fdstr), "%i", fd) <= 0)
  79                 return errno;
  80
  81         dir = opendir(PROC_FD_PATH);
  82
  83         if (!dir)
  84                 return errno;
  85
  86         /* /proc/self/fd/<fdstr> is a symlink to the actual file */
  87         for (dir_entry = readdir(dir); dir_entry; dir_entry = readdir(dir)) {
  88                 if (strcmp(dir_entry->d_name, fdstr) == 0)
  89                         break;
  90         }
  91
  92         if (!dir_entry) {
  93                 rc = ENOENT;
  94                 goto out;
  95         }
  96
  97         if (snprintf
  98             (proc_path, sizeof(proc_path), "%s%s", PROC_FD_PATH, dir_entry->d_name) <= 0) {
  99                 rc = errno;
 100                 goto out;
 101         }
 102
 103         if (fstat(fd, &fd_stat) < 0 || stat(proc_path, &path_stat) < 0) {
 104                 rc = errno;
 105                 goto out;
 106         }
 107
 108         /* filenames are not accurate, interface and inode ID need to checked too */
 109         if (fd_stat.st_dev != path_stat.st_dev
 110             || fd_stat.st_ino != path_stat.st_ino) {
 111                 rc = EINVAL;
 112                 goto out;
 113         }
 114
 115         /* resolve /proc/self/fd/<fdstr> symlink now */
 116         resolved_path = realpath(proc_path, NULL);
 117
 118         if (!resolved_path) {
 119                 rc = errno;
 120                 goto out;
 121         }
 122
 123         strlcpy(path, resolved_path, path_len);
 124
 125         free(resolved_path);
 126
 127  out:
 128         closedir(dir);
 129         return rc;
 130 }