--- uuid.c 2004/01/19 14:56:35 1.44
+++ uuid.c 2004/02/13 21:01:41 1.45
@@ -61,69 +61,9 @@
Unix UTC base time is January 1, 1970) */
#define UUID_TIMEOFFSET "01B21DD213814000"
-/* IEEE 802 MAC address encoding/decoding bit fields
-
- ATTENTION:
-
- In case no real/physical IEEE 802 address is available, both
- "draft-leach-uuids-guids-01" (section "4. Node IDs when no IEEE 802
- network card is available") and RFC 2518 (section "6.4.1 Node Field
- Generation Without the IEEE 802 Address") recommend (quoted from RFC
- 2518):
-
- "The ideal solution is to obtain a 47 bit cryptographic quality
- random number, and use it as the low 47 bits of the node ID, with
- the most significant bit of the first octet of the node ID set to
- 1. This bit is the unicast/multicast bit, which will never be set
- in IEEE 802 addresses obtained from network cards; hence, there can
- never be a conflict between UUIDs generated by machines with and
- without network cards."
-
- This passage clearly explains the intention to use IEEE 802 multicast
- addresses. Unfortunately, it incorrectly explains how to implement
- this! It should instead specify the "*LEAST* significant bit of the
- first octet of the node ID" as the multicast bit in a memory and
- hexadecimal string representation of a 48-bit IEEE 802 MAC address.
-
- Unfortunately, even the reference implementation included in the
- expired IETF "draft-leach-uuids-guids-01" incorrectly set the
- multicast bit with an OR bit operation and an incorrect mask of
- 0x80. Hence, several other UUID implementations found on the
- Internet have inherited this bug.
-
- Luckily, neither DCE 1.1 nor ISO/IEC 11578:1996 are affected by this
- problem. They disregard the topic of missing IEEE 802 addresses
- entirely, and thus avoid adopting this bug from the original draft
- and code ;-)
-
- It seems that this standards bug arises from a false interpretation,
- as the multicast bit is actually the *MOST* significant bit in IEEE
- 802.3 (Ethernet) _transmission order_ of an IEEE 802 MAC address. The
- authors were likely not aware that the bitwise order of an octet from
- a MAC address memory and hexadecimal string representation is still
- always from left (MSB, bit 7) to right (LSB, bit 0).
-
- For more information, see "Understanding Physical Addresses" in
- "Ethernet -- The Definitive Guide", p.43, and the section "ETHERNET
- MULTICAST ADDRESSES" in http://www.iana.org/assignments/ethernet-numbers.
-
- At OSSP, we do it the intended/correct way and generate a real
- IEEE 802 multicast address. Those wanting to encode broken IEEE
- 802 MAC addresses (as specified) can nevertheless use a brain dead
- compile-time option to switch off the correct behavior. When decoding
- we always use the correct behavior of course. */
-
-/* encoding */
-#ifdef WITH_RFC2518
-#define IEEE_MAC_MCBIT_ENC BM_OCTET(1,0,0,0,0,0,0,0)
-#else
-#define IEEE_MAC_MCBIT_ENC BM_OCTET(0,0,0,0,0,0,0,1)
-#endif
-#define IEEE_MAC_LOBIT_ENC BM_OCTET(0,0,0,0,0,0,1,0)
-
-/* decoding */
-#define IEEE_MAC_MCBIT_DEC BM_OCTET(0,0,0,0,0,0,0,1)
-#define IEEE_MAC_LOBIT_DEC BM_OCTET(0,0,0,0,0,0,1,0)
+/* IEEE 802 MAC address encoding/decoding bit fields */
+#define IEEE_MAC_MCBIT BM_OCTET(0,0,0,0,0,0,0,1)
+#define IEEE_MAC_LOBIT BM_OCTET(0,0,0,0,0,0,1,0)
/* IEEE 802 MAC address octet length */
#define IEEE_MAC_OCTETS 6
@@ -622,8 +562,8 @@
(unsigned int)uuid->obj.node[3],
(unsigned int)uuid->obj.node[4],
(unsigned int)uuid->obj.node[5],
- (uuid->obj.node[0] & IEEE_MAC_LOBIT_DEC ? "local" : "global"),
- (uuid->obj.node[0] & IEEE_MAC_MCBIT_DEC ? "multicast" : "unicast"));
+ (uuid->obj.node[0] & IEEE_MAC_LOBIT ? "local" : "global"),
+ (uuid->obj.node[0] & IEEE_MAC_MCBIT ? "multicast" : "unicast"));
}
else {
/* decode anything else as hexadecimal byte-string only */
@@ -843,8 +783,8 @@
if ((mode & UUID_MAKE_MC) || (uuid->mac[0] & BM_OCTET(1,0,0,0,0,0,0,0))) {
/* generate random IEEE 802 local multicast MAC address */
prng_data(uuid->prng, (void *)&(uuid->obj.node), sizeof(uuid->obj.node));
- uuid->obj.node[0] |= IEEE_MAC_MCBIT_ENC;
- uuid->obj.node[0] |= IEEE_MAC_LOBIT_ENC;
+ uuid->obj.node[0] |= IEEE_MAC_MCBIT;
+ uuid->obj.node[0] |= IEEE_MAC_LOBIT;
}
else {
/* use real regular MAC address */
|
