From a3b3df8d0891ff83b61f62020652798d365299c0 Mon Sep 17 00:00:00 2001

From: Michael Trapp <michael.trapp@sap.com>

Date: Mon, 20 Jun 2022 17:10:36 +0200

Subject: libuuid: Implement continuous clock handling for time based UUIDs

In a uuidd setup, the daemon is a singleton and can maintain it's own

resources for time based UUID generation. This requires a dedicated

'clock sequence range' but does not need any further lock/update of

the LIBUUID_CLOCK_FILE from uuidd. The range of available clock values

is extended by a continuous handling of the clock updates - instead of

updating the value to the current timestamp, it is incremented by

the number of requested UUIDs.

Upstream: http://github.com/util-linux/util-linux/commit/3cfba7d39b66eff4307218fefd8bb34bb1621f83

Addresses: https://bugzilla.redhat.com/show_bug.cgi?id=2141970

Signed-off-by: Karel Zak <kzak@redhat.com>

---

 libuuid/src/gen_uuid.c  | 91 ++++++++++++++++++++++++++++++++++++++---

 libuuid/src/libuuid.sym |  1 +

 libuuid/src/uuidd.h     |  1 +

 misc-utils/uuidd.8.adoc |  3 ++

 misc-utils/uuidd.c      | 54 +++++++++++++++++++++---

 5 files changed, 140 insertions(+), 10 deletions(-)

diff --git a/libuuid/src/gen_uuid.c b/libuuid/src/gen_uuid.c

index d353fa1a0..ac682a1d8 100644

--- a/libuuid/src/gen_uuid.c

+++ b/libuuid/src/gen_uuid.c

@@ -209,6 +209,8 @@ static int get_node_id(unsigned char *node_id)

 /* Assume that the gettimeofday() has microsecond granularity */

 #define MAX_ADJUSTMENT 10

+/* Reserve a clock_seq value for the 'continuous clock' implementation */

+#define CLOCK_SEQ_CONT 0

 /*

  * Get clock from global sequence clock counter.

@@ -275,8 +277,10 @@ static int get_clock(uint32_t *clock_high, uint32_t *clock_low,

 	}

 	if ((last.tv_sec == 0) && (last.tv_usec == 0)) {

-		ul_random_get_bytes(&clock_seq, sizeof(clock_seq));

-		clock_seq &= 0x3FFF;

+		do {

+			ul_random_get_bytes(&clock_seq, sizeof(clock_seq));

+			clock_seq &= 0x3FFF;

+		} while (clock_seq == CLOCK_SEQ_CONT);

 		gettimeofday(&last, NULL);

 		last.tv_sec--;

 	}

@@ -286,7 +290,9 @@ try_again:

 	if ((tv.tv_sec < last.tv_sec) ||

 	    ((tv.tv_sec == last.tv_sec) &&

 	     (tv.tv_usec < last.tv_usec))) {

-		clock_seq = (clock_seq+1) & 0x3FFF;

+		do {

+			clock_seq = (clock_seq+1) & 0x3FFF;

+		} while (clock_seq == CLOCK_SEQ_CONT);

 		adjustment = 0;

 		last = tv;

 	} else if ((tv.tv_sec == last.tv_sec) &&

@@ -331,6 +337,64 @@ try_again:

 	return ret;

 }

+/*

+ * Get current time in 100ns ticks.

+ */

+static uint64_t get_clock_counter(void)

+{

+	struct timeval tv;

+	uint64_t clock_reg;

+

+	gettimeofday(&tv, NULL);

+	clock_reg = tv.tv_usec*10;

+	clock_reg += ((uint64_t) tv.tv_sec) * 10000000ULL;

+

+	return clock_reg;

+}

+

+/*

+ * Get continuous clock value.

+ *

+ * Return -1 if there is no further clock counter available,

+ * otherwise return 0.

+ *

+ * This implementation doesn't deliver clock counters based on

+ * the current time because last_clock_reg is only incremented

+ * by the number of requested UUIDs.

+ * max_clock_offset is used to limit the offset of last_clock_reg.

+ */

+static int get_clock_cont(uint32_t *clock_high,

+			  uint32_t *clock_low,

+			  int num,

+			  uint32_t max_clock_offset)

+{

+	/* 100ns based time offset according to RFC 4122. 4.1.4. */

+	const uint64_t reg_offset = (((uint64_t) 0x01B21DD2) << 32) + 0x13814000;

+	static uint64_t last_clock_reg = 0;

+	uint64_t clock_reg;

+

+	if (last_clock_reg == 0)

+		last_clock_reg = get_clock_counter();

+

+	clock_reg = get_clock_counter();

+	if (max_clock_offset) {

+		uint64_t clock_offset = max_clock_offset * 10000000ULL;

+		if (last_clock_reg < (clock_reg - clock_offset))

+			last_clock_reg = clock_reg - clock_offset;

+	}

+

+	clock_reg += MAX_ADJUSTMENT;

+

+	if ((last_clock_reg + num) >= clock_reg)

+		return -1;

+

+	*clock_high = (last_clock_reg + reg_offset) >> 32;

+	*clock_low = last_clock_reg + reg_offset;

+	last_clock_reg += num;

+

+	return 0;

+}

+

 #if defined(HAVE_UUIDD) && defined(HAVE_SYS_UN_H)

 /*

@@ -403,7 +467,7 @@ static int get_uuid_via_daemon(int op __attribute__((__unused__)),

 }

 #endif

-int __uuid_generate_time(uuid_t out, int *num)

+static int __uuid_generate_time_internal(uuid_t out, int *num, uint32_t cont_offset)

 {

 	static unsigned char node_id[6];

 	static int has_init = 0;

@@ -423,7 +487,14 @@ int __uuid_generate_time(uuid_t out, int *num)

 		}

 		has_init = 1;

 	}

-	ret = get_clock(&clock_mid, &uu.time_low, &uu.clock_seq, num);

+	if (cont_offset) {

+		ret = get_clock_cont(&clock_mid, &uu.time_low, *num, cont_offset);

+		uu.clock_seq = CLOCK_SEQ_CONT;

+		if (ret != 0)	/* fallback to previous implpementation */

+			ret = get_clock(&clock_mid, &uu.time_low, &uu.clock_seq, num);

+	} else {

+		ret = get_clock(&clock_mid, &uu.time_low, &uu.clock_seq, num);

+	}

 	uu.clock_seq |= 0x8000;

 	uu.time_mid = (uint16_t) clock_mid;

 	uu.time_hi_and_version = ((clock_mid >> 16) & 0x0FFF) | 0x1000;

@@ -432,6 +503,16 @@ int __uuid_generate_time(uuid_t out, int *num)

 	return ret;

 }

+int __uuid_generate_time(uuid_t out, int *num)

+{

+	return __uuid_generate_time_internal(out, num, 0);

+}

+

+int __uuid_generate_time_cont(uuid_t out, int *num, uint32_t cont_offset)

+{

+	return __uuid_generate_time_internal(out, num, cont_offset);

+}

+

 /*

  * Generate time-based UUID and store it to @out

  *

diff --git a/libuuid/src/libuuid.sym b/libuuid/src/libuuid.sym

index 342453368..96372a857 100644

--- a/libuuid/src/libuuid.sym

+++ b/libuuid/src/libuuid.sym

@@ -60,6 +60,7 @@ global:

 UUIDD_PRIVATE {

 global:

 	__uuid_generate_time;

+	__uuid_generate_time_cont;

 	__uuid_generate_random;

 local:

 	*;

diff --git a/libuuid/src/uuidd.h b/libuuid/src/uuidd.h

index fbe821ff3..f76acc8b2 100644

--- a/libuuid/src/uuidd.h

+++ b/libuuid/src/uuidd.h

@@ -49,6 +49,7 @@

 #define UUIDD_MAX_OP			UUIDD_OP_BULK_RANDOM_UUID

 extern int __uuid_generate_time(uuid_t out, int *num);

+extern int __uuid_generate_time_cont(uuid_t out, int *num, uint32_t cont);

 extern int __uuid_generate_random(uuid_t out, int *num);

 #endif /* _UUID_UUID_H */

diff --git a/misc-utils/uuidd.8.adoc b/misc-utils/uuidd.8.adoc

index 77ee2b3e6..c87125901 100644

--- a/misc-utils/uuidd.8.adoc

+++ b/misc-utils/uuidd.8.adoc

@@ -24,6 +24,9 @@ The *uuidd* daemon is used by the UUID library to generate universally unique id

 == OPTIONS

+*-C*, *--cont-clock* _opt_arg_::

+Activate continuous clock handling for time based UUIDs. *uuidd* could use all possible clock values, beginning with the daemon's start time. The optional argument can be used to set a value for the max_clock_offset. This gurantees, that a clock value of a UUID will always be within the range of the max_clock_offset. '-C' or '--cont-clock' enables the feature with a default max_clock_offset of 2 hours. '-C<NUM>[hd]' or '--cont-clock=<NUM>[hd]' enables the feature with a max_clock_offset of NUM seconds. In case of an appended h or d, the NUM value is read in hours or days. The minimum value is 60 seconds, the maximum value is 365 days.

+

 *-d*, *--debug*::

 Run uuidd in debugging mode. This prevents uuidd from running as a daemon.

diff --git a/misc-utils/uuidd.c b/misc-utils/uuidd.c

index 78a37d2e8..b859ccb8c 100644

--- a/misc-utils/uuidd.c

+++ b/misc-utils/uuidd.c

@@ -72,6 +72,8 @@ struct uuidd_cxt_t {

 	const char	*cleanup_pidfile;

 	const char	*cleanup_socket;

 	uint32_t	timeout;

+	uint32_t	cont_clock_offset;

+

 	unsigned int	debug: 1,

 			quiet: 1,

 			no_fork: 1,

@@ -106,6 +108,8 @@ static void __attribute__((__noreturn__)) usage(void)

 	fputs(_(" -P, --no-pid            do not create pid file\n"), out);

 	fputs(_(" -F, --no-fork           do not daemonize using double-fork\n"), out);

 	fputs(_(" -S, --socket-activation do not create listening socket\n"), out);

+	fputs(_(" -C, --cont-clock[=<NUM>[hd]]\n"), out);

+	fputs(_("                         activate continuous clock handling\n"), out);

 	fputs(_(" -d, --debug             run in debugging mode\n"), out);

 	fputs(_(" -q, --quiet             turn on quiet mode\n"), out);

 	fputs(USAGE_SEPARATOR, out);

@@ -438,6 +442,15 @@ static void server_loop(const char *socket_path, const char *pidfile_path,

 	pfd[POLLFD_SOCKET].fd = s;

 	pfd[POLLFD_SIGNAL].events = pfd[POLLFD_SOCKET].events = POLLIN | POLLERR | POLLHUP;

+	num = 1;

+	if (uuidd_cxt->cont_clock_offset) {

+		/* trigger initialization */

+		(void) __uuid_generate_time_cont(uu, &num, uuidd_cxt->cont_clock_offset);

+		if (uuidd_cxt->debug)

+			fprintf(stderr, _("max_clock_offset = %u sec\n"),

+				uuidd_cxt->cont_clock_offset);

+	}

+

 	while (1) {

 		ret = poll(pfd, ARRAY_SIZE(pfd),

 				uuidd_cxt->timeout ?

@@ -494,7 +507,8 @@ static void server_loop(const char *socket_path, const char *pidfile_path,

 			break;

 		case UUIDD_OP_TIME_UUID:

 			num = 1;

-			if (__uuid_generate_time(uu, &num) < 0 && !uuidd_cxt->quiet)

+			ret = __uuid_generate_time_cont(uu, &num, uuidd_cxt->cont_clock_offset);

+			if (ret < 0 && !uuidd_cxt->quiet)

 				warnx(_("failed to open/lock clock counter"));

 			if (uuidd_cxt->debug) {

 				uuid_unparse(uu, str);

@@ -505,7 +519,8 @@ static void server_loop(const char *socket_path, const char *pidfile_path,

 			break;

 		case UUIDD_OP_RANDOM_UUID:

 			num = 1;

-			if (__uuid_generate_time(uu, &num) < 0 && !uuidd_cxt->quiet)

+			ret = __uuid_generate_time_cont(uu, &num, uuidd_cxt->cont_clock_offset);

+			if (ret < 0 && !uuidd_cxt->quiet)

 				warnx(_("failed to open/lock clock counter"));

 			if (uuidd_cxt->debug) {

 				uuid_unparse(uu, str);

@@ -515,7 +530,8 @@ static void server_loop(const char *socket_path, const char *pidfile_path,

 			reply_len = sizeof(uu);

 			break;

 		case UUIDD_OP_BULK_TIME_UUID:

-			if (__uuid_generate_time(uu, &num) < 0 && !uuidd_cxt->quiet)

+			ret = __uuid_generate_time_cont(uu, &num, uuidd_cxt->cont_clock_offset);

+			if (ret < 0 && !uuidd_cxt->quiet)

 				warnx(_("failed to open/lock clock counter"));

 			if (uuidd_cxt->debug) {

 				uuid_unparse(uu, str);

@@ -567,6 +583,27 @@ static void __attribute__ ((__noreturn__)) unexpected_size(int size)

 	errx(EXIT_FAILURE, _("Unexpected reply length from server %d"), size);

 }

+static uint32_t parse_cont_clock(char *arg)

+{

+	uint32_t min_val = 60,

+		 max_val = (3600 * 24 * 365),

+		 factor = 1;

+	char *p = &arg[strlen(arg)-1];

+

+	if ('h' == *p) {

+		*p = '\0';

+		factor = 3600;

+		min_val = 1;

+	}

+	if ('d' == *p) {

+		*p = '\0';

+		factor = 24 * 3600;

+		min_val = 1;

+	}

+	return factor * str2num_or_err(optarg, 10, _("failed to parse --cont-clock/-C"),

+				       min_val, max_val / factor);

+}

+

 static void parse_options(int argc, char **argv, struct uuidd_cxt_t *uuidd_cxt,

 			  struct uuidd_options_t *uuidd_opts)

 {

@@ -581,6 +618,7 @@ static void parse_options(int argc, char **argv, struct uuidd_cxt_t *uuidd_cxt,

 		{"no-pid", no_argument, NULL, 'P'},

 		{"no-fork", no_argument, NULL, 'F'},

 		{"socket-activation", no_argument, NULL, 'S'},

+		{"cont-clock", optional_argument, NULL, 'C'},

 		{"debug", no_argument, NULL, 'd'},

 		{"quiet", no_argument, NULL, 'q'},

 		{"version", no_argument, NULL, 'V'},

@@ -596,9 +634,15 @@ static void parse_options(int argc, char **argv, struct uuidd_cxt_t *uuidd_cxt,

 	int excl_st[ARRAY_SIZE(excl)] = UL_EXCL_STATUS_INIT;

 	int c;

-	while ((c = getopt_long(argc, argv, "p:s:T:krtn:PFSdqVh", longopts, NULL)) != -1) {

+	while ((c = getopt_long(argc, argv, "p:s:T:krtn:PFSC::dqVh", longopts, NULL)) != -1) {

 		err_exclusive_options(c, longopts, excl, excl_st);

 		switch (c) {

+		case 'C':

+			if (optarg != NULL)

+				uuidd_cxt->cont_clock_offset = parse_cont_clock(optarg);

+			else

+				uuidd_cxt->cont_clock_offset = 7200; /* default 2h */

+			break;

 		case 'd':

 			uuidd_cxt->debug = 1;

 			break;

@@ -673,7 +717,7 @@ int main(int argc, char **argv)

 	char		*cp;

 	int		ret;

-	struct uuidd_cxt_t uuidd_cxt = { .timeout = 0 };

+	struct uuidd_cxt_t uuidd_cxt = { .timeout = 0, .cont_clock_offset = 0 };

 	struct uuidd_options_t uuidd_opts = { .socket_path = UUIDD_SOCKET_PATH };

 	setlocale(LC_ALL, "");

-- 

2.39.1