C API

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libcriu is a C API for CRIU, a simple wrapper around our RPC. Although you can use RPC directly, libcriu is a wrapper providing the interface that is much easier to use from C code. Note that RPC is supported in the first place, and if you want the most recent set of features you should probably use RPC directly.

Introduction[edit]

libcriu functions are defined in lib/criu.h.

To create a library lib/libcriu.so, run make in the main directory.

Preparation[edit]

init options[edit]

Call int criu_init_opts(void) to initialize request options.

Note: it should be called before using any other functions from libcriu, except criu_check(). Also you should use it to reinitialize options. It returns 0 on success and -1 on fail.

set service address[edit]

Use void criu_set_service_address(char *address) to specify path to a CRIU service socket. Call it with NULL to make libcriu use the default address (currently /var/run/criu_service.socket).

set dump/restore options[edit]

Use criu_set_* functions to setup dump/restore options.

void criu_set_pid(int pid);
void criu_set_images_dir_fd(int fd); /* must be set for dump/restore */
void criu_set_leave_running(bool leave_running);
void criu_set_ext_unix_sk(bool ext_unix_sk);
void criu_set_tcp_established(bool tcp_established);
void criu_set_evasive_devices(bool evasive_devices);
void criu_set_shell_job(bool shell_job);
void criu_set_file_locks(bool file_locks);
void criu_set_log_level(int log_level);
void criu_set_log_file(char *log_file);
Note.svg Note: This set of calls is not thread safe! For thread safety the same calls with _local suffix should be used

If no pid is set on dump, CRIU will dump the calling process itself.

Note.svg Note: If a calling process is not run as root, the whole process tree to be dumped must have the same uid, otherwise CRIU refuses to dump. See Usage#Security.
Note.svg Note: images_dir_fd is required at dump/restore, all other options might be left unset.

The client must open directory for/with images by itself and set images_dir_fd to the opened directory fd. CRIU will open /proc/client_pid/fd/images_dir_fd, so it will work even if the client is in another namespace.

The logic of setting request is the same as when setting options in console. Here is an example:

# criu restore -D /path/to/imgs_dir -v4 -o restore.log

is equal to:

criu_init_opts();
criu_set_service_address("/path/to/criu/service/socket");

int fd = open("/path/to/imgs_dir", O_DIRECTORY);
criu_set_images_dir_fd(fd);

criu_set_log_file("restore.log");
criu_set_log_level(4);

criu_restore();

Operations[edit]

Use the following functions to perform CRIU actions.

check[edit]

int criu_check(void);

dump[edit]

int criu_dump(void);

restore[edit]

int criu_restore(void);

restore as a child[edit]

This one is special. It will fork and exec criu swrk (Service WoRKer) to allow restoring process as a caller child. Calling "exec" implies some restrictions, as, for example, one should make sure, that criu binary is present in PATH and has suid bit set (see Usage#Security).

int criu_restore_child(void);

Return values[edit]

Here is a table of return and errno values of the above functions:

Return value errno Description
0 undefined Success
>0 undefined Success (criu_restore() only)
-EBADE RPC error (if provided(see include/cr-errno.h), 0 otherwise) RPC has returned fail.
-ECONNREFUSED errno Unable to connect to CRIU.
-ECOMM errno Unable to send/recv msg to/from CRIU.
-EINVAL undefined CRIU doesn't support this type of request. You should probably update CRIU.
-EBADMSG undefined Unexpected response from CRIU. You should probably update CRIU.

Examples[edit]

You could find example of using libcriu at test/others/ibcriu.