[Bug 1956] New: [PATCH] Incorrect random multicast MAC address creation in UUID generator
Wine Bugs
wine-bugs at winehq.org
Fri Jan 23 02:58:37 CST 2004
http://bugs.winehq.org/show_bug.cgi?id=1956
Summary: [PATCH] Incorrect random multicast MAC address creation
in UUID generator
Product: Wine
Version: 20031212
Platform: All
OS/Version: other
Status: UNCONFIRMED
Severity: normal
Priority: P2
Component: wine-kernel
AssignedTo: wine-bugs at winehq.org
ReportedBy: rse at engelschall.com
In case no real/physical IEEE 802 address is available, both the expired
"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."
Unfortunately, this incorrectly explains how to implement this and
this UUID generator code inherited this generation bug from the broken
reference code in the standards draft. They 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.
This standards bug arised 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 standards authors
forgot 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).
The following patch fixes this:
--- wine/dlls/rpcrt4/rpcrt4_main.c.orig Thu Sep 11 03:05:19 2003
+++ wine/dlls/rpcrt4/rpcrt4_main.c Thu Jan 15 18:18:08 2004
@@ -351,7 +351,7 @@
if (sd < 0) {
/* if we can't open a socket, just use random numbers */
/* set the multicast bit to prevent conflicts with real cards */
- a[0] = (rand() & 0xff) | 0x80;
+ a[0] = (rand() & 0xff) | 0x01;
a[1] = rand() & 0xff;
a[2] = rand() & 0xff;
a[3] = rand() & 0xff;
@@ -366,7 +366,7 @@
close(sd);
/* no ifconf, so just use random numbers */
/* set the multicast bit to prevent conflicts with real cards */
- a[0] = (rand() & 0xff) | 0x80;
+ a[0] = (rand() & 0xff) | 0x01;
a[1] = rand() & 0xff;
a[2] = rand() & 0xff;
a[3] = rand() & 0xff;
@@ -403,7 +403,7 @@
}
/* if we didn't find a valid address, make a random one */
/* once again, set multicast bit to avoid conflicts */
- a[0] = (rand() & 0xff) | 0x80;
+ a[0] = (rand() & 0xff) | 0x01;
a[1] = rand() & 0xff;
a[2] = rand() & 0xff;
a[3] = rand() & 0xff;
@@ -416,7 +416,7 @@
}
#else
/* no networking info, so generate a random address */
- a[0] = (rand() & 0xff) | 0x80;
+ a[0] = (rand() & 0xff) | 0x01;
a[1] = rand() & 0xff;
a[2] = rand() & 0xff;
a[3] = rand() & 0xff;
--
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