src/lxc/file_utils.c

   1 /* liblxcapi
   2  *
   3  * Copyright © 2018 Christian Brauner <christian.brauner@ubuntu.com>.
   4  * Copyright © 2018 Canonical Ltd.
   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 version 2, as
   8  * published by the Free Software Foundation.
   9  *
  10  * This program is distributed in the hope that it will be useful,
  11  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13  * GNU General Public License for more details.
  14  *
  15  * You should have received a copy of the GNU General Public License along
  16  * with this program; if not, write to the Free Software Foundation, Inc.,
  17  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  18  */
  19
  20 #include "config.h"
  21
  22 #include <errno.h>
  23 #include <fcntl.h>
  24 #include <linux/magic.h>
  25 #include <stdlib.h>
  26 #include <sys/stat.h>
  27 #include <sys/types.h>
  28
  29 #include "file_utils.h"
  30 #include "log.h"
  31 #include "macro.h"
  32 #include "string.h"
  33
  34 lxc_log_define(file_utils, lxc);
  35
  36 int lxc_write_to_file(const char *filename, const void *buf, size_t count,
  37                       bool add_newline, mode_t mode)
  38 {
  39         int fd, saved_errno;
  40         ssize_t ret;
  41
  42         fd = open(filename, O_WRONLY | O_TRUNC | O_CREAT | O_CLOEXEC, mode);
  43         if (fd < 0)
  44                 return -1;
  45
  46         ret = lxc_write_nointr(fd, buf, count);
  47         if (ret < 0)
  48                 goto out_error;
  49
  50         if ((size_t)ret != count)
  51                 goto out_error;
  52
  53         if (add_newline) {
  54                 ret = lxc_write_nointr(fd, "\n", 1);
  55                 if (ret != 1)
  56                         goto out_error;
  57         }
  58
  59         close(fd);
  60         return 0;
  61
  62 out_error:
  63         saved_errno = errno;
  64         close(fd);
  65         errno = saved_errno;
  66         return -1;
  67 }
  68
  69 int lxc_read_from_file(const char *filename, void *buf, size_t count)
  70 {
  71         int fd = -1, saved_errno;
  72         ssize_t ret;
  73
  74         fd = open(filename, O_RDONLY | O_CLOEXEC);
  75         if (fd < 0)
  76                 return -1;
  77
  78         if (!buf || !count) {
  79                 char buf2[100];
  80                 size_t count2 = 0;
  81
  82                 while ((ret = lxc_read_nointr(fd, buf2, 100)) > 0)
  83                         count2 += ret;
  84
  85                 if (ret >= 0)
  86                         ret = count2;
  87         } else {
  88                 memset(buf, 0, count);
  89                 ret = lxc_read_nointr(fd, buf, count);
  90         }
  91
  92         saved_errno = errno;
  93         close(fd);
  94         errno = saved_errno;
  95         return ret;
  96 }
  97
  98 ssize_t lxc_write_nointr(int fd, const void *buf, size_t count)
  99 {
 100         ssize_t ret;
 101 again:
 102         ret = write(fd, buf, count);
 103         if (ret < 0 && errno == EINTR)
 104                 goto again;
 105
 106         return ret;
 107 }
 108
 109 ssize_t lxc_read_nointr(int fd, void *buf, size_t count)
 110 {
 111         ssize_t ret;
 112 again:
 113         ret = read(fd, buf, count);
 114         if (ret < 0 && errno == EINTR)
 115                 goto again;
 116
 117         return ret;
 118 }
 119
 120 ssize_t lxc_read_nointr_expect(int fd, void *buf, size_t count, const void *expected_buf)
 121 {
 122         ssize_t ret;
 123
 124         ret = lxc_read_nointr(fd, buf, count);
 125         if (ret <= 0)
 126                 return ret;
 127
 128         if ((size_t)ret != count)
 129                 return -1;
 130
 131         if (expected_buf && memcmp(buf, expected_buf, count) != 0) {
 132                 errno = EINVAL;
 133                 return -1;
 134         }
 135
 136         return ret;
 137 }
 138
 139 bool file_exists(const char *f)
 140 {
 141         struct stat statbuf;
 142
 143         return stat(f, &statbuf) == 0;
 144 }
 145
 146 int print_to_file(const char *file, const char *content)
 147 {
 148         FILE *f;
 149         int ret = 0;
 150
 151         f = fopen(file, "w");
 152         if (!f)
 153                 return -1;
 154
 155         if (fprintf(f, "%s", content) != strlen(content))
 156                 ret = -1;
 157
 158         fclose(f);
 159         return ret;
 160 }
 161
 162 int is_dir(const char *path)
 163 {
 164         struct stat statbuf;
 165         int ret;
 166
 167         ret = stat(path, &statbuf);
 168         if (ret == 0 && S_ISDIR(statbuf.st_mode))
 169                 return 1;
 170
 171         return 0;
 172 }
 173
 174 /*
 175  * Return the number of lines in file @fn, or -1 on error
 176  */
 177 int lxc_count_file_lines(const char *fn)
 178 {
 179         FILE *f;
 180         char *line = NULL;
 181         size_t sz = 0;
 182         int n = 0;
 183
 184         f = fopen_cloexec(fn, "r");
 185         if (!f)
 186                 return -1;
 187
 188         while (getline(&line, &sz, f) != -1) {
 189                 n++;
 190         }
 191
 192         free(line);
 193         fclose(f);
 194         return n;
 195 }
 196
 197 int lxc_make_tmpfile(char *template, bool rm)
 198 {
 199         int fd, ret;
 200         mode_t msk;
 201
 202         msk = umask(0022);
 203         fd = mkstemp(template);
 204         umask(msk);
 205         if (fd < 0)
 206                 return -1;
 207
 208         if (!rm)
 209                 return fd;
 210
 211         ret = unlink(template);
 212         if (ret < 0) {
 213                 close(fd);
 214                 return -1;
 215         }
 216
 217         return fd;
 218 }
 219
 220 /* In overlayfs, st_dev is unreliable. So on overlayfs we don't do the
 221  * lxc_rmdir_onedev()
 222  */
 223 static bool is_native_overlayfs(const char *path)
 224 {
 225         if (has_fs_type(path, OVERLAY_SUPER_MAGIC) ||
 226             has_fs_type(path, OVERLAYFS_SUPER_MAGIC))
 227                 return true;
 228
 229         return false;
 230 }
 231
 232 bool is_fs_type(const struct statfs *fs, fs_type_magic magic_val)
 233 {
 234         return (fs->f_type == (fs_type_magic)magic_val);
 235 }
 236
 237 bool has_fs_type(const char *path, fs_type_magic magic_val)
 238 {
 239         bool has_type;
 240         int ret;
 241         struct statfs sb;
 242
 243         ret = statfs(path, &sb);
 244         if (ret < 0)
 245                 return false;
 246
 247         return is_fs_type(&sb, magic_val);
 248 }
 249
 250 bool fhas_fs_type(int fd, fs_type_magic magic_val)
 251 {
 252         int ret;
 253         struct statfs sb;
 254
 255         ret = fstatfs(fd, &sb);
 256         if (ret < 0)
 257                 return false;
 258
 259         return is_fs_type(&sb, magic_val);
 260 }
 261
 262 FILE *fopen_cloexec(const char *path, const char *mode)
 263 {
 264         int open_mode = 0;
 265         int step = 0;
 266         int fd;
 267         int saved_errno = 0;
 268         FILE *ret;
 269
 270         if (!strncmp(mode, "r+", 2)) {
 271                 open_mode = O_RDWR;
 272                 step = 2;
 273         } else if (!strncmp(mode, "r", 1)) {
 274                 open_mode = O_RDONLY;
 275                 step = 1;
 276         } else if (!strncmp(mode, "w+", 2)) {
 277                 open_mode = O_RDWR | O_TRUNC | O_CREAT;
 278                 step = 2;
 279         } else if (!strncmp(mode, "w", 1)) {
 280                 open_mode = O_WRONLY | O_TRUNC | O_CREAT;
 281                 step = 1;
 282         } else if (!strncmp(mode, "a+", 2)) {
 283                 open_mode = O_RDWR | O_CREAT | O_APPEND;
 284                 step = 2;
 285         } else if (!strncmp(mode, "a", 1)) {
 286                 open_mode = O_WRONLY | O_CREAT | O_APPEND;
 287                 step = 1;
 288         }
 289         for (; mode[step]; step++)
 290                 if (mode[step] == 'x')
 291                         open_mode |= O_EXCL;
 292         open_mode |= O_CLOEXEC;
 293
 294         fd = open(path, open_mode, 0666);
 295         if (fd < 0)
 296                 return NULL;
 297
 298         ret = fdopen(fd, mode);
 299         saved_errno = errno;
 300         if (!ret)
 301                 close(fd);
 302         errno = saved_errno;
 303         return ret;
 304 }