nmblookup returns NULL mac Address from linux samba servers

[Jeremy Allison]

On Thu, Aug 24, 2017 at 03:30:30AM -0700, shivappa Sangapur via samba-technical wrote:
> Hi List,
> 
> When I was checking nmblookup utility, MAC address returned is always
> 00-00-00-00-00-00
> #nmblookup -A 192.168.10.10
> 
> Looking up status of 192.168.10.10
>         SHIVAPPAS     <00> -         H <ACTIVE>
>         SHIVAPPAS     <03> -         H <ACTIVE>
>         SHIVAPPAS     <20> -         H <ACTIVE>
>         SHIVAPPAS     <1e> - <GROUP> H <ACTIVE>
>         SHIVAPPAS     <00> - <GROUP> H <ACTIVE>
> 
>         MAC Address = 00-00-00-00-00-00
> 
> But there is one old thread on the same. The result is same even though
> samba server is on same subnet (execute nmblookup on same samba server.)
> https://lists.samba.org/archive/samba/1999-September/014495.html
> 
> This behavior is same in samba-4.5, 4.6.
> Can somebody help me to identify the cause.
> nmb->answers structure is always having 00000000 for mac address field.
> 
> Addition info: Windows clients return MAC address when nmblookup is executed
> for windows IP.

Yeah, I remember changing that a long time ago. It was deliberate
to prevent information leakage via NetBIOS. There is no good reason
a potentially off-local-net query should return MAC address info.