[PATCH 8/9] libuuid: introduce uuid_generate_time_safe()

[Petr Uzel <petr.uzel@xxxxxxx>]

The problem with libuuid interface is that it is impossible to
inform the caller of uuid_generate_time() if the UUID was generated
in a safe manner (either via uuidd, or using the global clock state
counter).

This patch introduces new function,

int uuid_generate_time_safe(uuid_t out)

which can report whether the generated UUID is safe.

Signed-off-by: Petr Uzel <petr.uzel@xxxxxxx>
---
 shlibs/uuid/src/gen_uuid.c |   35 +++++++++++++++++++++++++++++------
 shlibs/uuid/src/uuid.h     |    1 +
 shlibs/uuid/src/uuid.sym   |   10 +++++++++-
 3 files changed, 39 insertions(+), 7 deletions(-)

diff --git a/shlibs/uuid/src/gen_uuid.c b/shlibs/uuid/src/gen_uuid.c
index 6bd1f1d..b47c13f 100644
--- a/shlibs/uuid/src/gen_uuid.c
+++ b/shlibs/uuid/src/gen_uuid.c
@@ -595,8 +595,15 @@ int __uuid_generate_time(uuid_t out, int *num)
 	return ret;
 }
 
-void uuid_generate_time(uuid_t out)
-{
+/*
+ * Generate time-based UUID and store it to @out
+ *
+ * Tries to guarantee uniqueness of the generated UUIDs by obtaining them from the uuidd daemon,
+ * or, if uuidd is not usable, by using the global clock state counter (see get_clock()).
+ * If neither of these is possible (e.g. because of insufficient permissions), it generates
+ * the UUID anyway, but returns -1. Otherwise, returns 0.
+ */
+static int uuid_generate_time_generic(uuid_t out) {
 #ifdef HAVE_TLS
 	THREAD_LOCAL int		num = 0;
 	THREAD_LOCAL struct uuid	uu;
@@ -615,7 +622,7 @@ void uuid_generate_time(uuid_t out)
 			last_time = time(0);
 			uuid_unpack(out, &uu);
 			num--;
-			return;
+			return 0;
 		}
 		num = 0;
 	}
@@ -628,14 +635,30 @@ void uuid_generate_time(uuid_t out)
 		}
 		num--;
 		uuid_pack(&uu, out);
-		return;
+		return 0;
 	}
 #else
 	if (get_uuid_via_daemon(UUIDD_OP_TIME_UUID, out, 0) == 0)
-		return;
+		return 0;
 #endif
 
-	__uuid_generate_time(out, 0);
+	return __uuid_generate_time(out, 0);
+}
+
+/*
+ * Generate time-based UUID and store it to @out.
+ *
+ * Discards return value from uuid_generate_time_generic()
+ */
+void uuid_generate_time(uuid_t out)
+{
+	(void)uuid_generate_time_generic(out);
+}
+
+
+int uuid_generate_time_safe(uuid_t out)
+{
+	return uuid_generate_time_generic(out);
 }
 
 
diff --git a/shlibs/uuid/src/uuid.h b/shlibs/uuid/src/uuid.h
index e329bf7..874d65a 100644
--- a/shlibs/uuid/src/uuid.h
+++ b/shlibs/uuid/src/uuid.h
@@ -79,6 +79,7 @@ void uuid_copy(uuid_t dst, const uuid_t src);
 void uuid_generate(uuid_t out);
 void uuid_generate_random(uuid_t out);
 void uuid_generate_time(uuid_t out);
+int uuid_generate_time_safe(uuid_t out);
 
 /* isnull.c */
 int uuid_is_null(const uuid_t uu);
diff --git a/shlibs/uuid/src/uuid.sym b/shlibs/uuid/src/uuid.sym
index eb57c33..d859ca7 100644
--- a/shlibs/uuid/src/uuid.sym
+++ b/shlibs/uuid/src/uuid.sym
@@ -1,6 +1,6 @@
 /*
  * The symbol versioning ensures that a new application requiring symbol foo()
- * can't run with old libblkid.so not providing foo() - the global SONAME
+ * can't run with old libuuid.so not providing foo() - the global SONAME
  * version info can't enforce this since we never change the SONAME.
  *
  * The original libuuid from e2fsprogs (<=1.41.5) does not to use
@@ -31,3 +31,11 @@ global:
 local:
 	*;
 };
+
+/*
+ * version(s) since util-linux 2.20
+ */
+UUID_2.20 {
+global:
+	uuid_generate_time_safe;
+} UUID_1.0;
-- 
1.7.1

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