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@winehq.org ReportedBy: rse@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;