[Bug 283400] if_bridge(4) contains false statement about link address selection

https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=283400

            Bug ID: 283400
           Summary: if_bridge(4) contains false statement about link
                    address selection
           Product: Documentation
           Version: Latest
          Hardware: Any
                OS: Any
            Status: New
          Severity: Affects Many People
          Priority: ---
         Component: Manual Pages
          Assignee: bugs@FreeBSD.org
          Reporter: jason.mann@gmail.com
                CC: doc@FreeBSD.org

if_bridge(4) contains the following paragraph:

     The if_bridge interface randomly chooses a link (MAC) address in the
     range reserved for locally administered addresses when it is created.
     This address is guaranteed to be unique only across all if_bridge
     interfaces on the local machine.  Thus you can theoretically have two
     bridges on different machines with the same link addresses.  The address
     can be changed by assigning the desired link address using ifconfig(8).

It appears that the choice of bridge link address is not random, but is instead
based on the value of kern.hostid.

If two systems mistakenly end up with the same hostid, when using disk cloning
for example, then the MAC address chosen for bridge interfaces will also be the
same.

To avoid confusion, this should be clarified.

Also, the MAC address chosen for a bridge appears to always begin with the
octets 58:9c:fc:10:xx:xx.  The '8' as the second digit of the first octet
indicates a universally administered address, not a locally administered one.

https://en.wikipedia.org/wiki/MAC_address#Ranges_of_group_and_locally_administered_addresses

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