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 #ifndef MAX_GRBUF_SIZE
  30 #define MAX_GRBUF_SIZE 65536
  31 #endif
  32
  33 #include <errno.h>
  34 #include <linux/loop.h>
  35 #include <linux/types.h>
  36 #include <stdarg.h>
  37 #include <stdbool.h>
  38 #include <stdio.h>
  39 #include <sys/syscall.h>
  40 #include <sys/types.h>
  41 #include <sys/vfs.h>
  42 #include <unistd.h>
  43
  44 #include "file_utils.h"
  45 #include "initutils.h"
  46 #include "macro.h"
  47 #include "raw_syscalls.h"
  48 #include "string_utils.h"
  49
  50 /* returns 1 on success, 0 if there were any failures */
  51 extern int lxc_rmdir_onedev(const char *path, const char *exclude);
  52 extern int get_u16(unsigned short *val, const char *arg, int base);
  53 extern int mkdir_p(const char *dir, mode_t mode);
  54 extern char *get_rundir(void);
  55
  56 /* Define getline() if missing from the C library */
  57 #ifndef HAVE_GETLINE
  58 #ifdef HAVE_FGETLN
  59 #include <../include/getline.h>
  60 #endif
  61 #endif
  62
  63 static inline int lxc_set_cloexec(int fd)
  64 {
  65         return fcntl(fd, F_SETFD, FD_CLOEXEC);
  66 }
  67
  68 /*
  69  * Struct to carry child pid from lxc_popen() to lxc_pclose(). Not an opaque
  70  * struct to allow direct access to the underlying FILE without additional
  71  * wrappers.
  72  */
  73 struct lxc_popen_FILE {
  74         int pipe;
  75         FILE *f;
  76         pid_t child_pid;
  77 };
  78
  79 /* popen(command, "re") replacement that restores default signal mask
  80  * via sigprocmask(2) (unblocks all signals) after fork(2) but prior to calling exec(3).
  81  * In short, popen(command, "re") does pipe() + fork()                 + exec()
  82  * while lxc_popen(command)       does pipe() + fork() + sigprocmask() + exec().
  83  * Returns pointer to struct lxc_popen_FILE, that should be freed with lxc_pclose().
  84  * On error returns NULL.
  85  */
  86 extern struct lxc_popen_FILE *lxc_popen(const char *command);
  87
  88 /* pclose() replacement to be used on struct lxc_popen_FILE *,
  89  * returned by lxc_popen().
  90  * Waits for associated process to terminate, returns its exit status and
  91  * frees resources, pointed to by struct lxc_popen_FILE *.
  92  */
  93 extern int lxc_pclose(struct lxc_popen_FILE *fp);
  94
  95 /*
  96  * wait on a child we forked
  97  */
  98 extern int wait_for_pid(pid_t pid);
  99 extern int lxc_wait_for_pid_status(pid_t pid);
 100
 101 #if HAVE_OPENSSL
 102 extern int sha1sum_file(char *fnam, unsigned char *md_value, int *md_len);
 103 #endif
 104
 105 /* initialize rand with urandom */
 106 extern int randseed(bool);
 107
 108 /* are we unprivileged with respect to our namespaces */
 109 inline static bool am_guest_unpriv(void) {
 110         return geteuid() != 0;
 111 }
 112
 113 /* are we unprivileged with respect to init_user_ns */
 114 inline static bool am_host_unpriv(void)
 115 {
 116         FILE *f;
 117         uid_t user, host, count;
 118         int ret;
 119
 120         if (geteuid() != 0)
 121                 return true;
 122
 123         /* Now: are we in a user namespace? Because then we're also
 124          * unprivileged.
 125          */
 126         f = fopen("/proc/self/uid_map", "r");
 127         if (!f) {
 128                 return false;
 129         }
 130
 131         ret = fscanf(f, "%u %u %u", &user, &host, &count);
 132         fclose(f);
 133         if (ret != 3) {
 134                 return false;
 135         }
 136
 137         if (user != 0 || host != 0 || count != UINT32_MAX)
 138                 return true;
 139         return false;
 140 }
 141
 142 /*
 143  * parse /proc/self/uid_map to find what @orig maps to
 144  */
 145 extern uid_t get_ns_uid(uid_t orig);
 146 /*
 147  * parse /proc/self/gid_map to find what @orig maps to
 148  */
 149 extern gid_t get_ns_gid(gid_t orig);
 150
 151 extern bool dir_exists(const char *path);
 152
 153 #define FNV1A_64_INIT ((uint64_t)0xcbf29ce484222325ULL)
 154 extern uint64_t fnv_64a_buf(void *buf, size_t len, uint64_t hval);
 155
 156 extern bool is_shared_mountpoint(const char *path);
 157 extern int detect_shared_rootfs(void);
 158 extern bool detect_ramfs_rootfs(void);
 159 extern char *on_path(const char *cmd, const char *rootfs);
 160 extern bool cgns_supported(void);
 161 extern char *choose_init(const char *rootfs);
 162 extern bool switch_to_ns(pid_t pid, const char *ns);
 163 extern char *get_template_path(const char *t);
 164 extern int safe_mount(const char *src, const char *dest, const char *fstype,
 165                       unsigned long flags, const void *data,
 166                       const char *rootfs);
 167 extern int lxc_mount_proc_if_needed(const char *rootfs);
 168 extern int open_devnull(void);
 169 extern int set_stdfds(int fd);
 170 extern int null_stdfds(void);
 171 extern int lxc_preserve_ns(const int pid, const char *ns);
 172
 173 /* Check whether a signal is blocked by a process. */
 174 extern bool task_blocks_signal(pid_t pid, int signal);
 175
 176 /* Switch to a new uid and gid.
 177  * If LXC_INVALID_{G,U}ID is passed then the set{g,u}id() will not be called.
 178  */
 179 extern bool lxc_switch_uid_gid(uid_t uid, gid_t gid);
 180 extern bool lxc_setgroups(int size, gid_t list[]);
 181
 182 /* Find an unused loop device and associate it with source. */
 183 extern int lxc_prepare_loop_dev(const char *source, char *loop_dev, int flags);
 184
 185 /* Clear all mounts on a given node.
 186  * >= 0 successfully cleared. The number returned is the number of umounts
 187  *      performed.
 188  * < 0  error umounting. Return -errno.
 189  */
 190 extern int lxc_unstack_mountpoint(const char *path, bool lazy);
 191
 192 /*
 193  * run_command runs a command and collect it's std{err,out} output in buf.
 194  *
 195  * @param[out] buf     The buffer where the commands std{err,out] output will be
 196  *                     read into. If no output was produced, buf will be memset
 197  *                     to 0.
 198  * @param[in] buf_size The size of buf. This function will reserve one byte for
 199  *                     \0-termination.
 200  * @param[in] child_fn The function to be run in the child process. This
 201  *                     function must exec.
 202  * @param[in] args     Arguments to be passed to child_fn.
 203  */
 204 extern int run_command(char *buf, size_t buf_size, int (*child_fn)(void *),
 205                        void *args);
 206
 207 /*
 208  * run_command runs a command and collect it's std{err,out} output in buf, returns exit status.
 209  *
 210  * @param[out] buf     The buffer where the commands std{err,out] output will be
 211  *                     read into. If no output was produced, buf will be memset
 212  *                     to 0.
 213  * @param[in] buf_size The size of buf. This function will reserve one byte for
 214  *                     \0-termination.
 215  * @param[in] child_fn The function to be run in the child process. This
 216  *                     function must exec.
 217  * @param[in] args     Arguments to be passed to child_fn.
 218  */
 219 extern int run_command_status(char *buf, size_t buf_size, int (*child_fn)(void *),
 220                        void *args);
 221
 222 /* Concatenate all passed-in strings into one path. Do not fail. If any piece
 223  * is not prefixed with '/', add a '/'.
 224  */
 225 __attribute__((sentinel)) extern char *must_concat(const char *first, ...);
 226 __attribute__((sentinel)) extern char *must_make_path(const char *first, ...);
 227 __attribute__((sentinel)) extern char *must_append_path(char *first, ...);
 228
 229 /* return copy of string @entry;  do not fail. */
 230 extern char *must_copy_string(const char *entry);
 231
 232 /* Re-allocate a pointer, do not fail */
 233 extern void *must_realloc(void *orig, size_t sz);
 234
 235 extern bool lxc_nic_exists(char *nic);
 236
 237 static inline uint64_t lxc_getpagesize(void)
 238 {
 239         int64_t pgsz;
 240
 241         pgsz = sysconf(_SC_PAGESIZE);
 242         if (pgsz <= 0)
 243                 pgsz = 1 << 12;
 244
 245         return pgsz;
 246 }
 247
 248 /* If n is not a power of 2 this function will return the next power of 2
 249  * greater than that number. Note that this function always returns the *next*
 250  * power of 2 *greater* that number not the *nearest*. For example, passing 1025
 251  * as argument this function will return 2048 although the closest power of 2
 252  * would be 1024.
 253  * If the caller passes in 0 they will receive 0 in return since this is invalid
 254  * input and 0 is not a power of 2.
 255  */
 256 extern uint64_t lxc_find_next_power2(uint64_t n);
 257
 258 /* Set a signal the child process will receive after the parent has died. */
 259 extern int lxc_set_death_signal(int signal, pid_t parent);
 260 extern int fd_cloexec(int fd, bool cloexec);
 261 extern int recursive_destroy(char *dirname);
 262 extern int lxc_setup_keyring(void);
 263
 264 #endif /* __LXC_UTILS_H */