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-rw-r--r--lib/lib.c23
1 files changed, 8 insertions, 15 deletions
diff --git a/lib/lib.c b/lib/lib.c
index 8c46678f..3bfe7fc4 100644
--- a/lib/lib.c
+++ b/lib/lib.c
@@ -1138,29 +1138,22 @@ int qstrcmp(const void *a, const void *b)
return strcmp(*(char **)a, *(char **)b);
}
-// According to http://www.opengroup.org/onlinepubs/9629399/apdxa.htm
-// we should generate a uuid structure by reading a clock with 100 nanosecond
-// precision, normalizing it to the start of the gregorian calendar in 1582,
-// and looking up our eth0 mac address.
-//
-// On the other hand, we have 128 bits to come up with a unique identifier, of
-// which 6 have a defined value. /dev/urandom it is.
-
+// See https://tools.ietf.org/html/rfc4122, specifically section 4.4
+// "Algorithms for Creating a UUID from Truly Random or Pseudo-Random
+// Numbers".
void create_uuid(char *uuid)
{
- // Read 128 random bits
+ // "Set all the ... bits to randomly (or pseudo-randomly) chosen values".
int fd = xopenro("/dev/urandom");
xreadall(fd, uuid, 16);
close(fd);
- // Claim to be a DCE format UUID.
+ // "Set the four most significant bits ... of the time_hi_and_version
+ // field to the 4-bit version number [4]".
uuid[6] = (uuid[6] & 0x0F) | 0x40;
+ // "Set the two most significant bits (bits 6 and 7) of
+ // clock_seq_hi_and_reserved to zero and one, respectively".
uuid[8] = (uuid[8] & 0x3F) | 0x80;
-
- // rfc2518 section 6.4.1 suggests if we're not using a macaddr, we should
- // set bit 1 of the node ID, which is the mac multicast bit. This means we
- // should never collide with anybody actually using a macaddr.
- uuid[11] |= 128;
}
char *show_uuid(char *uuid)