src/lxc/utils.h

   1 /*
   2  * lxc: linux Container library
   3  *
   4  * (C) Copyright IBM Corp. 2007, 2008
   5  *
   6  * Authors:
   7  * Daniel Lezcano <daniel.lezcano at free.fr>
   8  *
   9  * This library is free software; you can redistribute it and/or
  10  * modify it under the terms of the GNU Lesser General Public
  11  * License as published by the Free Software Foundation; either
  12  * version 2.1 of the License, or (at your option) any later version.
  13  *
  14  * This library is distributed in the hope that it will be useful,
  15  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  16  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  17  * Lesser General Public License for more details.
  18  *
  19  * You should have received a copy of the GNU Lesser General Public
  20  * License along with this library; if not, write to the Free Software
  21  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  22  */
  23 #ifndef __LXC_UTILS_H
  24 #define __LXC_UTILS_H
  25
  26 /* Properly support loop devices on 32bit systems. */
  27 #define _FILE_OFFSET_BITS 64
  28
  29 #include <errno.h>
  30 #include <linux/loop.h>
  31 #include <linux/types.h>
  32 #include <stdarg.h>
  33 #include <stdbool.h>
  34 #include <stdio.h>
  35 #include <sys/syscall.h>
  36 #include <sys/types.h>
  37 #include <sys/vfs.h>
  38 #include <unistd.h>
  39
  40 #include "file_utils.h"
  41 #include "initutils.h"
  42 #include "macro.h"
  43 #include "raw_syscalls.h"
  44 #include "string_utils.h"
  45
  46 /* returns 1 on success, 0 if there were any failures */
  47 extern int lxc_rmdir_onedev(const char *path, const char *exclude);
  48 extern int get_u16(unsigned short *val, const char *arg, int base);
  49 extern int mkdir_p(const char *dir, mode_t mode);
  50 extern char *get_rundir(void);
  51
  52 /* Define getline() if missing from the C library */
  53 #ifndef HAVE_GETLINE
  54 #ifdef HAVE_FGETLN
  55 #include <../include/getline.h>
  56 #endif
  57 #endif
  58
  59 static inline int lxc_set_cloexec(int fd)
  60 {
  61         return fcntl(fd, F_SETFD, FD_CLOEXEC);
  62 }
  63
  64 /* Struct to carry child pid from lxc_popen() to lxc_pclose().
  65  * Not an opaque struct to allow direct access to the underlying FILE *
  66  * (i.e., struct lxc_popen_FILE *file; fgets(buf, sizeof(buf), file->f))
  67  * without additional wrappers.
  68  */
  69 struct lxc_popen_FILE {
  70         int pipe;
  71         FILE *f;
  72         pid_t child_pid;
  73 };
  74
  75 /* popen(command, "re") replacement that restores default signal mask
  76  * via sigprocmask(2) (unblocks all signals) after fork(2) but prior to calling exec(3).
  77  * In short, popen(command, "re") does pipe() + fork()                 + exec()
  78  * while lxc_popen(command)       does pipe() + fork() + sigprocmask() + exec().
  79  * Returns pointer to struct lxc_popen_FILE, that should be freed with lxc_pclose().
  80  * On error returns NULL.
  81  */
  82 extern struct lxc_popen_FILE *lxc_popen(const char *command);
  83
  84 /* pclose() replacement to be used on struct lxc_popen_FILE *,
  85  * returned by lxc_popen().
  86  * Waits for associated process to terminate, returns its exit status and
  87  * frees resources, pointed to by struct lxc_popen_FILE *.
  88  */
  89 extern int lxc_pclose(struct lxc_popen_FILE *fp);
  90
  91 /*
  92  * wait on a child we forked
  93  */
  94 extern int wait_for_pid(pid_t pid);
  95 extern int lxc_wait_for_pid_status(pid_t pid);
  96
  97 #if HAVE_LIBGNUTLS
  98 #define SHA_DIGEST_LENGTH 20
  99 extern int sha1sum_file(char *fnam, unsigned char *md_value);
 100 #endif
 101
 102 /* initialize rand with urandom */
 103 extern int randseed(bool);
 104
 105 /* are we unprivileged with respect to our namespaces */
 106 inline static bool am_guest_unpriv(void) {
 107         return geteuid() != 0;
 108 }
 109
 110 /* are we unprivileged with respect to init_user_ns */
 111 inline static bool am_host_unpriv(void)
 112 {
 113         FILE *f;
 114         uid_t user, host, count;
 115         int ret;
 116
 117         if (geteuid() != 0)
 118                 return true;
 119
 120         /* Now: are we in a user namespace? Because then we're also
 121          * unprivileged.
 122          */
 123         f = fopen("/proc/self/uid_map", "r");
 124         if (!f) {
 125                 return false;
 126         }
 127
 128         ret = fscanf(f, "%u %u %u", &user, &host, &count);
 129         fclose(f);
 130         if (ret != 3) {
 131                 return false;
 132         }
 133
 134         if (user != 0 || host != 0 || count != UINT32_MAX)
 135                 return true;
 136         return false;
 137 }
 138
 139 /*
 140  * parse /proc/self/uid_map to find what @orig maps to
 141  */
 142 extern uid_t get_ns_uid(uid_t orig);
 143 /*
 144  * parse /proc/self/gid_map to find what @orig maps to
 145  */
 146 extern gid_t get_ns_gid(gid_t orig);
 147
 148 extern bool dir_exists(const char *path);
 149
 150 #define FNV1A_64_INIT ((uint64_t)0xcbf29ce484222325ULL)
 151 extern uint64_t fnv_64a_buf(void *buf, size_t len, uint64_t hval);
 152
 153 extern bool is_shared_mountpoint(const char *path);
 154 extern int detect_shared_rootfs(void);
 155 extern bool detect_ramfs_rootfs(void);
 156 extern char *on_path(const char *cmd, const char *rootfs);
 157 extern bool cgns_supported(void);
 158 extern char *choose_init(const char *rootfs);
 159 extern bool switch_to_ns(pid_t pid, const char *ns);
 160 extern char *get_template_path(const char *t);
 161 extern int safe_mount(const char *src, const char *dest, const char *fstype,
 162                       unsigned long flags, const void *data,
 163                       const char *rootfs);
 164 extern int lxc_mount_proc_if_needed(const char *rootfs);
 165 extern int open_devnull(void);
 166 extern int set_stdfds(int fd);
 167 extern int null_stdfds(void);
 168 extern int lxc_preserve_ns(const int pid, const char *ns);
 169
 170 /* Check whether a signal is blocked by a process. */
 171 extern bool task_blocks_signal(pid_t pid, int signal);
 172
 173 /* Switch to a new uid and gid.
 174  * If LXC_INVALID_{G,U}ID is passed then the set{g,u}id() will not be called.
 175  */
 176 extern bool lxc_switch_uid_gid(uid_t uid, gid_t gid);
 177 extern bool lxc_setgroups(int size, gid_t list[]);
 178
 179 /* Find an unused loop device and associate it with source. */
 180 extern int lxc_prepare_loop_dev(const char *source, char *loop_dev, int flags);
 181
 182 /* Clear all mounts on a given node.
 183  * >= 0 successfully cleared. The number returned is the number of umounts
 184  *      performed.
 185  * < 0  error umounting. Return -errno.
 186  */
 187 extern int lxc_unstack_mountpoint(const char *path, bool lazy);
 188
 189 /*
 190  * run_command runs a command and collect it's std{err,out} output in buf.
 191  *
 192  * @param[out] buf     The buffer where the commands std{err,out] output will be
 193  *                     read into. If no output was produced, buf will be memset
 194  *                     to 0.
 195  * @param[in] buf_size The size of buf. This function will reserve one byte for
 196  *                     \0-termination.
 197  * @param[in] child_fn The function to be run in the child process. This
 198  *                     function must exec.
 199  * @param[in] args     Arguments to be passed to child_fn.
 200  */
 201 extern int run_command(char *buf, size_t buf_size, int (*child_fn)(void *),
 202                        void *args);
 203
 204 /* Concatenate all passed-in strings into one path. Do not fail. If any piece
 205  * is not prefixed with '/', add a '/'.
 206  */
 207 __attribute__((sentinel)) extern char *must_concat(const char *first, ...);
 208 __attribute__((sentinel)) extern char *must_make_path(const char *first, ...);
 209 __attribute__((sentinel)) extern char *must_append_path(char *first, ...);
 210
 211 /* return copy of string @entry;  do not fail. */
 212 extern char *must_copy_string(const char *entry);
 213
 214 /* Re-allocate a pointer, do not fail */
 215 extern void *must_realloc(void *orig, size_t sz);
 216
 217 extern bool lxc_nic_exists(char *nic);
 218
 219 static inline uint64_t lxc_getpagesize(void)
 220 {
 221         int64_t pgsz;
 222
 223         pgsz = sysconf(_SC_PAGESIZE);
 224         if (pgsz <= 0)
 225                 pgsz = 1 << 12;
 226
 227         return pgsz;
 228 }
 229
 230 /* If n is not a power of 2 this function will return the next power of 2
 231  * greater than that number. Note that this function always returns the *next*
 232  * power of 2 *greater* that number not the *nearest*. For example, passing 1025
 233  * as argument this function will return 2048 although the closest power of 2
 234  * would be 1024.
 235  * If the caller passes in 0 they will receive 0 in return since this is invalid
 236  * input and 0 is not a power of 2.
 237  */
 238 extern uint64_t lxc_find_next_power2(uint64_t n);
 239
 240 /* Set a signal the child process will receive after the parent has died. */
 241 extern int lxc_set_death_signal(int signal, pid_t parent);
 242 extern int fd_cloexec(int fd, bool cloexec);
 243 extern int recursive_destroy(char *dirname);
 244 extern int lxc_setup_keyring(void);
 245
 246 #endif /* __LXC_UTILS_H */