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 #ifndef _GNU_SOURCE
  21 #define _GNU_SOURCE 1
  22 #endif
  23 #include <errno.h>
  24 #include <fcntl.h>
  25 #include <linux/magic.h>
  26 #include <stdlib.h>
  27 #include <sys/stat.h>
  28 #include <sys/sendfile.h>
  29 #include <sys/types.h>
  30
  31 #include "config.h"
  32 #include "file_utils.h"
  33 #include "log.h"
  34 #include "macro.h"
  35 #include "string.h"
  36
  37 lxc_log_define(file_utils, lxc);
  38
  39 int lxc_write_to_file(const char *filename, const void *buf, size_t count,
  40                       bool add_newline, mode_t mode)
  41 {
  42         int fd, saved_errno;
  43         ssize_t ret;
  44
  45         fd = open(filename, O_WRONLY | O_TRUNC | O_CREAT | O_CLOEXEC, mode);
  46         if (fd < 0)
  47                 return -1;
  48
  49         ret = lxc_write_nointr(fd, buf, count);
  50         if (ret < 0)
  51                 goto out_error;
  52
  53         if ((size_t)ret != count)
  54                 goto out_error;
  55
  56         if (add_newline) {
  57                 ret = lxc_write_nointr(fd, "\n", 1);
  58                 if (ret != 1)
  59                         goto out_error;
  60         }
  61
  62         close(fd);
  63         return 0;
  64
  65 out_error:
  66         saved_errno = errno;
  67         close(fd);
  68         errno = saved_errno;
  69         return -1;
  70 }
  71
  72 int lxc_read_from_file(const char *filename, void *buf, size_t count)
  73 {
  74         int fd = -1, saved_errno;
  75         ssize_t ret;
  76
  77         fd = open(filename, O_RDONLY | O_CLOEXEC);
  78         if (fd < 0)
  79                 return -1;
  80
  81         if (!buf || !count) {
  82                 char buf2[100];
  83                 size_t count2 = 0;
  84
  85                 while ((ret = lxc_read_nointr(fd, buf2, 100)) > 0)
  86                         count2 += ret;
  87
  88                 if (ret >= 0)
  89                         ret = count2;
  90         } else {
  91                 memset(buf, 0, count);
  92                 ret = lxc_read_nointr(fd, buf, count);
  93         }
  94
  95         saved_errno = errno;
  96         close(fd);
  97         errno = saved_errno;
  98         return ret;
  99 }
 100
 101 ssize_t lxc_write_nointr(int fd, const void *buf, size_t count)
 102 {
 103         ssize_t ret;
 104 again:
 105         ret = write(fd, buf, count);
 106         if (ret < 0 && errno == EINTR)
 107                 goto again;
 108
 109         return ret;
 110 }
 111
 112 ssize_t lxc_send_nointr(int sockfd, void *buf, size_t len, int flags)
 113 {
 114         ssize_t ret;
 115 again:
 116         ret = send(sockfd, buf, len, flags);
 117         if (ret < 0 && errno == EINTR)
 118                 goto again;
 119
 120         return ret;
 121 }
 122
 123 ssize_t lxc_read_nointr(int fd, void *buf, size_t count)
 124 {
 125         ssize_t ret;
 126 again:
 127         ret = read(fd, buf, count);
 128         if (ret < 0 && errno == EINTR)
 129                 goto again;
 130
 131         return ret;
 132 }
 133
 134 ssize_t lxc_recv_nointr(int sockfd, void *buf, size_t len, int flags)
 135 {
 136         ssize_t ret;
 137 again:
 138         ret = recv(sockfd, buf, len, flags);
 139         if (ret < 0 && errno == EINTR)
 140                 goto again;
 141
 142         return ret;
 143 }
 144
 145 ssize_t lxc_read_nointr_expect(int fd, void *buf, size_t count, const void *expected_buf)
 146 {
 147         ssize_t ret;
 148
 149         ret = lxc_read_nointr(fd, buf, count);
 150         if (ret <= 0)
 151                 return ret;
 152
 153         if ((size_t)ret != count)
 154                 return -1;
 155
 156         if (expected_buf && memcmp(buf, expected_buf, count) != 0) {
 157                 errno = EINVAL;
 158                 return -1;
 159         }
 160
 161         return ret;
 162 }
 163
 164 bool file_exists(const char *f)
 165 {
 166         struct stat statbuf;
 167
 168         return stat(f, &statbuf) == 0;
 169 }
 170
 171 int print_to_file(const char *file, const char *content)
 172 {
 173         FILE *f;
 174         int ret = 0;
 175
 176         f = fopen(file, "w");
 177         if (!f)
 178                 return -1;
 179
 180         if (fprintf(f, "%s", content) != strlen(content))
 181                 ret = -1;
 182
 183         fclose(f);
 184         return ret;
 185 }
 186
 187 int is_dir(const char *path)
 188 {
 189         struct stat statbuf;
 190         int ret;
 191
 192         ret = stat(path, &statbuf);
 193         if (ret == 0 && S_ISDIR(statbuf.st_mode))
 194                 return 1;
 195
 196         return 0;
 197 }
 198
 199 /*
 200  * Return the number of lines in file @fn, or -1 on error
 201  */
 202 int lxc_count_file_lines(const char *fn)
 203 {
 204         FILE *f;
 205         char *line = NULL;
 206         size_t sz = 0;
 207         int n = 0;
 208
 209         f = fopen_cloexec(fn, "r");
 210         if (!f)
 211                 return -1;
 212
 213         while (getline(&line, &sz, f) != -1) {
 214                 n++;
 215         }
 216
 217         free(line);
 218         fclose(f);
 219         return n;
 220 }
 221
 222 int lxc_make_tmpfile(char *template, bool rm)
 223 {
 224         int fd, ret;
 225         mode_t msk;
 226
 227         msk = umask(0022);
 228         fd = mkstemp(template);
 229         umask(msk);
 230         if (fd < 0)
 231                 return -1;
 232
 233         if (!rm)
 234                 return fd;
 235
 236         ret = unlink(template);
 237         if (ret < 0) {
 238                 close(fd);
 239                 return -1;
 240         }
 241
 242         return fd;
 243 }
 244
 245 bool is_fs_type(const struct statfs *fs, fs_type_magic magic_val)
 246 {
 247         return (fs->f_type == (fs_type_magic)magic_val);
 248 }
 249
 250 bool has_fs_type(const char *path, fs_type_magic magic_val)
 251 {
 252         int ret;
 253         struct statfs sb;
 254
 255         ret = statfs(path, &sb);
 256         if (ret < 0)
 257                 return false;
 258
 259         return is_fs_type(&sb, magic_val);
 260 }
 261
 262 bool fhas_fs_type(int fd, fs_type_magic magic_val)
 263 {
 264         int ret;
 265         struct statfs sb;
 266
 267         ret = fstatfs(fd, &sb);
 268         if (ret < 0)
 269                 return false;
 270
 271         return is_fs_type(&sb, magic_val);
 272 }
 273
 274 FILE *fopen_cloexec(const char *path, const char *mode)
 275 {
 276         int open_mode = 0;
 277         int step = 0;
 278         int fd;
 279         int saved_errno = 0;
 280         FILE *ret;
 281
 282         if (!strncmp(mode, "r+", 2)) {
 283                 open_mode = O_RDWR;
 284                 step = 2;
 285         } else if (!strncmp(mode, "r", 1)) {
 286                 open_mode = O_RDONLY;
 287                 step = 1;
 288         } else if (!strncmp(mode, "w+", 2)) {
 289                 open_mode = O_RDWR | O_TRUNC | O_CREAT;
 290                 step = 2;
 291         } else if (!strncmp(mode, "w", 1)) {
 292                 open_mode = O_WRONLY | O_TRUNC | O_CREAT;
 293                 step = 1;
 294         } else if (!strncmp(mode, "a+", 2)) {
 295                 open_mode = O_RDWR | O_CREAT | O_APPEND;
 296                 step = 2;
 297         } else if (!strncmp(mode, "a", 1)) {
 298                 open_mode = O_WRONLY | O_CREAT | O_APPEND;
 299                 step = 1;
 300         }
 301         for (; mode[step]; step++)
 302                 if (mode[step] == 'x')
 303                         open_mode |= O_EXCL;
 304         open_mode |= O_CLOEXEC;
 305
 306         fd = open(path, open_mode, 0660);
 307         if (fd < 0)
 308                 return NULL;
 309
 310         ret = fdopen(fd, mode);
 311         saved_errno = errno;
 312         if (!ret)
 313                 close(fd);
 314         errno = saved_errno;
 315         return ret;
 316 }
 317
 318 ssize_t lxc_sendfile_nointr(int out_fd, int in_fd, off_t *offset, size_t count)
 319 {
 320         ssize_t ret;
 321
 322 again:
 323         ret = sendfile(out_fd, in_fd, offset, count);
 324         if (ret < 0) {
 325                 if (errno == EINTR)
 326                         goto again;
 327
 328                 return -1;
 329         }
 330
 331         return ret;
 332 }