uuid.c File Reference

Universally unique identifier support. More...

#include "asterisk.h"
#include <uuid/uuid.h>
#include <fcntl.h>
#include "asterisk/uuid.h"
#include "asterisk/utils.h"
#include "asterisk/strings.h"
#include "asterisk/logger.h"
#include "asterisk/lock.h"

Include dependency graph for uuid.c:

Go to the source code of this file.

Data Structures
struct	ast_uuid

Functions
struct ast_uuid *	ast_str_to_uuid (char *str)
	Convert a string to a UUID. More...
void	ast_uuid_clear (struct ast_uuid *uuid)
	Clear a UUID by setting it to be a nil UUID (all 0s) More...
int	ast_uuid_compare (struct ast_uuid *left, struct ast_uuid *right)
	Compare two UUIDs. More...
struct ast_uuid *	ast_uuid_copy (struct ast_uuid *src)
	Make a copy of a UUID. More...
struct ast_uuid *	ast_uuid_generate (void)
	Generate a UUID. More...
char *	ast_uuid_generate_str (char *buf, size_t size)
	Generate a UUID string. More...
void	ast_uuid_init (void)
	Initialize the UUID system. More...
int	ast_uuid_is_nil (struct ast_uuid *uuid)
	Check if a UUID is a nil UUID (all 0s) More...
char *	ast_uuid_to_str (struct ast_uuid *uuid, char *buf, size_t size)
	Convert a UUID to a string. More...
static void	generate_uuid (struct ast_uuid *uuid)

Variables
static int	has_dev_urandom
static ast_mutex_t	uuid_lock = { PTHREAD_RECURSIVE_MUTEX_INITIALIZER_NP , NULL, {1, 0} }

Detailed Description

Universally unique identifier support.

ExtRef:

Depends on libuuid, a component of the e2fsprogs package - http://e2fsprogs.sourceforge.net/

Definition in file uuid.c.

Function Documentation

ast_str_to_uuid()

struct ast_uuid * ast_str_to_uuid

(

char *

str

)

Convert a string to a UUID.

This function allocates memory on the heap. The returned pointer must be freed using ast_free()

Parameters

str	The string to convert to a UUID

Return values

NULL	Failed to convert
non-NULL	The heap-allocated converted UUID

Definition at line 149 of file uuid.c.

{
    struct ast_uuid *uuid = ast_malloc(sizeof(*uuid));
    int res;
 
    if (!uuid) {
        return NULL;
    }
    res = uuid_parse(str, uuid->uu);
    if (res) {
        ast_log(LOG_WARNING, "Unable to convert string %s into a UUID\n", str);
        ast_free(uuid);
        return NULL;
    }
    return uuid;
}

References ast_free, ast_log, ast_malloc, LOG_WARNING, NULL, str, and ast_uuid::uu.

Referenced by AST_TEST_DEFINE(), and is_valid_uuid().

ast_uuid_clear()

void ast_uuid_clear

(

struct ast_uuid *

uuid

)

Clear a UUID by setting it to be a nil UUID (all 0s)

Parameters

uuid	UUID to clear

Definition at line 182 of file uuid.c.

{
    uuid_clear(uuid->uu);
}

References ast_uuid::uu.

Referenced by AST_TEST_DEFINE().

ast_uuid_compare()

int ast_uuid_compare	(	struct ast_uuid *	left,
		struct ast_uuid *	right
	)

Compare two UUIDs.

Parameters

left	First UUID to compare
right	Second UUID to compare

Return values

<0	left is lexicographically less than right
0	left and right are the same
>0	left is lexicographically greater than right

Definition at line 177 of file uuid.c.

{
    return uuid_compare(left->uu, right->uu);
}

References ast_uuid::uu.

Referenced by AST_TEST_DEFINE().

ast_uuid_copy()

struct ast_uuid * ast_uuid_copy

(

struct ast_uuid *

src

)

Make a copy of a UUID.

This function allocates memory on the heap. The returned pointer must be freed using ast_free()

Parameters

src	The source UUID to copy

Return values

NULL	Failed to copy
non-NULL	The heap-allocated duplicate UUID

Definition at line 166 of file uuid.c.

{
    struct ast_uuid *dst = ast_malloc(sizeof(*dst));
 
    if (!dst) {
        return NULL;
    }
    uuid_copy(dst->uu, src->uu);
    return dst;
}

References ast_malloc, NULL, and ast_uuid::uu.

Referenced by AST_TEST_DEFINE().

ast_uuid_generate()

struct ast_uuid * ast_uuid_generate

(

void

)

Generate a UUID.

This function allocates memory on the heap. The returned pointer must be freed using ast_free()

Return values

NULL	Generation failed
non-NULL	heap-allocated UUID

Definition at line 123 of file uuid.c.

{
    struct ast_uuid *uuid = ast_malloc(sizeof(*uuid));
 
    if (!uuid) {
        return NULL;
    }
    generate_uuid(uuid);
    return uuid;
}

References ast_malloc, generate_uuid(), and NULL.

Referenced by AST_TEST_DEFINE().

ast_uuid_generate_str()

char * ast_uuid_generate_str	(	char *	buf,
		size_t	size
	)

Generate a UUID string.

Since

12.0.0

Parameters

buf	The buffer where the UUID string will be stored
size	The size of the buffer. Must be at least AST_UUID_STR_LEN.

Returns

The UUID string (a pointer to buf)

Definition at line 141 of file uuid.c.

{
    struct ast_uuid uuid;
 
    generate_uuid(&uuid);
    return ast_uuid_to_str(&uuid, buf, size);
}

References ast_uuid_to_str(), buf, and generate_uuid().

Referenced by add_msid_to_stream(), ast_aeap_message_id_generate(), ast_datastores_alloc_datastore(), ast_rtp_new(), ast_sip_publish_client_alloc_datastore(), ast_sip_session_alloc_datastore(), ast_sorcery_alloc(), AST_TEST_DEFINE(), ast_websocket_uri_cb(), asterisk_daemon(), bridge_base_init(), build_entity_id(), generate_exchange_uuid(), pack_payload(), playback_create(), and sorcery_config_open().

ast_uuid_init()

void ast_uuid_init

(

void

)

Initialize the UUID system.

Definition at line 192 of file uuid.c.

{
    /* This requires some explanation.
     *
     * libuuid generates UUIDs based on random number generation. This involves
     * opening a handle to /dev/urandom or /dev/random in order to get random
     * data for the UUIDs.
     *
     * This is thread-safe, to a point. The problem is that the first attempt
     * to generate a UUID will result in opening the random number handle. Once
     * the handle is opened, all further generation is thread safe. This
     * first generation can be potentially risky if multiple threads attempt
     * to generate a UUID at the same time, though, since there is no thread
     * synchronization used within libuuid. To get around this potential
     * issue, we go ahead and generate a UUID up front so that the underlying
     * work is done before we start requesting UUIDs for real.
     *
     * Think of this along the same lines as initializing a singleton.
     */
    uuid_t uu;
    int dev_urandom_fd;
 
    dev_urandom_fd = open("/dev/urandom", O_RDONLY);
    if (dev_urandom_fd < 0) {
        ast_log(LOG_WARNING, "It appears your system does not have /dev/urandom on it. This\n"
                "means that UUID generation will use a pseudorandom number generator. Since\n"
                "the thread-safety of your system's random number generator cannot\n"
                "be guaranteed, we have to synchronize UUID generation. This may result\n"
                "in decreased performance. It is highly recommended that you set up your\n"
                "system to have /dev/urandom\n");
    } else {
        has_dev_urandom = 1;
        close(dev_urandom_fd);
    }
    uuid_generate_random(uu);
 
    ast_debug(1, "UUID system initiated\n");
}

References ast_debug, ast_log, dev_urandom_fd, has_dev_urandom, LOG_WARNING, and ast_uuid::uu.

Referenced by asterisk_daemon().

ast_uuid_is_nil()

int ast_uuid_is_nil

(

struct ast_uuid *

uuid

)

Check if a UUID is a nil UUID (all 0s)

Parameters

uuid	UUID to check

Return values

0	The UUID is not nil
non-zero	The UUID is nil

Definition at line 187 of file uuid.c.

{
    return uuid_is_null(uuid->uu);
}

References ast_uuid::uu.

Referenced by AST_TEST_DEFINE().

ast_uuid_to_str()

char * ast_uuid_to_str	(	struct ast_uuid *	uuid,
		char *	buf,
		size_t	size
	)

Convert a UUID to a string.

Parameters

	uuid	The UUID to convert to a string
[out]	buf	The buffer where the UUID string will be stored
	size	The size of the buffer. Must be at least AST_UUID_STR_LEN.

Returns

The UUID string (a pointer to buf)

Definition at line 134 of file uuid.c.

{
    ast_assert(size >= AST_UUID_STR_LEN);
    uuid_unparse(uuid->uu, buf);
    return ast_str_to_lower(buf);
}

References ast_assert, ast_str_to_lower(), AST_UUID_STR_LEN, buf, and ast_uuid::uu.

Referenced by AST_TEST_DEFINE(), and ast_uuid_generate_str().

generate_uuid()

static void generate_uuid ( struct ast_uuid *  uuid )

static

Definition at line 50 of file uuid.c.

{
    /* libuuid provides three methods of generating uuids,
     * uuid_generate(), uuid_generate_random(), and uuid_generate_time().
     *
     * uuid_generate_random() creates a UUID based on random numbers. The method
     * attempts to use either /dev/urandom or /dev/random to generate random values.
     * If these resources are unavailable, then random numbers will be generated
     * using C library calls to generate pseudorandom numbers.
     * This method of generating UUIDs corresponds to section 4.4 of RFC 4122.
     *
     * uuid_generate_time() creates a UUID based on the current time plus
     * a system identifier (MAC address of the ethernet interface). This
     * method of generating UUIDs corresponds to section 4.2 of RFC 4122.
     *
     * uuid_generate() will check if /dev/urandom or /dev/random is available to
     * use. If so, it will use uuid_generate_random(). Otherwise, it will use
     * uuid_generate_time(). The idea is that it avoids using pseudorandom
     * numbers if necessary.
     *
     * For our purposes, we do not use the time-based UUID at all. There are
     * several reasons for this:
     *
     * 1) The time-based algorithm makes use of a daemon process (uuidd) in order
     * to ensure that any concurrent requests for UUIDs result in unique results.
     * Use of this daemon is a bit dodgy for a few reasons
     *
     *     a) libuuid assumes a hardcoded location for the .pid file of the daemon.
     *     However, the daemon could already be running on the system in a different
     *     location than expected. If this is the case, then attempting to connect
     *     to the daemon will fail, and attempting to launch another instance in
     *     the expected location will also fail.
     *
     *     b) If the daemon is not running, then the first attempt to create a
     *     time-based UUID will result in launching the daemon. Because of the hard-
     *     coded locations that libuuid assumes for the daemon, Asterisk must be
     *     run with permissions that will allow for the daemon to be launched in
     *     the expected directories.
     *
     *     c) Once the daemon is running, concurrent requests for UUIDs are thread-safe.
     *     However, the actual launching of the daemon is not thread-safe since libuuid
     *     uses no synchronization primitives to ensure that only one thread (or process)
     *     launches the daemon.
     *
     *     d) When libuuid launches the daemon, it sets an inactivity timer.
     *     If no UUID generation requests are issued in that time period,
     *     then the daemon will exit. If a new request should occur after the daemon
     *     exits, then the daemon will be relaunched. Given point c), we cannot
     *     necessarily guarantee the thread-safety of time-based UUID generation since
     *     we cannot necessarily guarantee the daemon is running as we expect.
     *     We could set up a watchdog thread to generate UUIDs at regular intervals to
     *     prevent the daemon from exiting, but frankly, that sucks.
     *
     * 2) Since the MAC address of the Ethernet interface is part of the UUID when
     * using the time-based method, there is information leaked.
     *
     * Given these drawbacks, we stick to only using random UUIDs. The chance of /dev/random
     * or /dev/urandom not existing on systems in this age is next to none.
     */
 
    /* XXX Currently, we only protect this call if the user has no /dev/urandom on their system.
     * If it turns out that there are issues with UUID generation despite the presence of
     * /dev/urandom, then we may need to make the locking/unlocking unconditional.
     */
    if (!has_dev_urandom) {
        ast_mutex_lock(&uuid_lock);
    }
    uuid_generate_random(uuid->uu);
    if (!has_dev_urandom) {
        ast_mutex_unlock(&uuid_lock);
    }
}

References ast_mutex_lock, ast_mutex_unlock, has_dev_urandom, ast_uuid::uu, and uuid_lock.

Referenced by ast_uuid_generate(), and ast_uuid_generate_str().

Variable Documentation

has_dev_urandom

int has_dev_urandom

static

Definition at line 37 of file uuid.c.

Referenced by ast_uuid_init(), and generate_uuid().

uuid_lock

ast_mutex_t uuid_lock = { PTHREAD_RECURSIVE_MUTEX_INITIALIZER_NP , NULL, {1, 0} }

static

Definition at line 35 of file uuid.c.

Referenced by generate_uuid().