[Samba] Samba AD - Join MAC

[Micha Ballmann]

Hello Community,

im joining several macintosh workstations to my samba AD. First of all, 
it works pretty well and im able to authenticate/login my AD user on a mac.

Server: Ubuntu 16.04

SAMBA: 4.7.7

First:

Everytime when a mac starts up, some log entries are shown in log.samba. 
Looks like (Its not a flood, about 4 messages for each client):

[2018/04/19 14:35:04.645001,  0] 
../source4/dns_server/dns_update.c:407(handle_one_update)
   Can't handle updates of type 255 yet
[2018/04/19 14:52:43.556390,  0] 
../source4/dns_server/dns_update.c:407(handle_one_update)
   Can't handle updates of type 255 yet
[2018/04/19 14:52:43.915746,  0] 
../source4/dns_server/dns_update.c:407(handle_one_update)
   Can't handle updates of type 255 yet
[2018/04/19 15:02:25.312616,  0] 
../source4/dns_server/dns_update.c:407(handle_one_update)
   Can't handle updates of type 255 yet
[2018/04/19 15:02:25.692692,  0] 
../source4/dns_server/dns_update.c:407(handle_one_update)
   Can't handle updates of type 255 yet

Second:

Everytime when a mac starts up, during the login process, one samba 
process/CPU core is running on 100%. After successful login there is no 
more CPU peak to see. The login time is about 30-60 second.

I hope you can help me to understand these messages or behavior.

Withe best regards

Micha