[Samba] DNS internal confusion

[steve]

4.0.6 git
Hi
When I join a Linux client to a domain, upon joining, I notice a dns 
update request reported on the DC. It works. The client IP is handed to 
the DC, we can login etc. However, we can't ping the client by its name 
from the DC. ping: unknown host. sssd maintains the dns and subsequent 
requests work. The dns is updated fine.

With an xp client, it gets as far as:
ping xp_2
PING xp_2.hh3.site (192.168.1.42) 56(84) bytes of data.
so it gets the IP but goes no further.

here is the request from the Linux client:
Got a dns update request.
update count is 1
Looking at record:
      discard_const(update): struct dns_res_rec
         name                     : 'pinoso.hh3.site'
         rr_type                  : DNS_QTYPE_A (0x1)
         rr_class                 : DNS_QCLASS_IN (0x1)
         ttl                      : 0x00000e10 (3600)
         length                   : 0x0004 (4)
         rdata                    : union dns_rdata(case 0x1)
         ipv4_record              : 192.168.1.23
         unexpected               : DATA_BLOB length=0

Here is the xp request:
Got a dns update request.
update count is 2
Looking at record:
      discard_const(update): struct dns_res_rec
         name                     : 'xp_2.hh3.site'
         rr_type                  : DNS_QTYPE_A (0x1)
         rr_class                 : DNS_QCLASS_ANY (0xFF)
         ttl                      : 0x00000000 (0)
         length                   : 0x0000 (0)
         rdata                    : union dns_rdata(case 0x1)
         ipv4_record              : (null)
         unexpected               : DATA_BLOB length=0
Looking at record:
      discard_const(update): struct dns_res_rec
         name                     : 'xp_2.hh3.site'
         rr_type                  : DNS_QTYPE_A (0x1)
         rr_class                 : DNS_QCLASS_IN (0x1)
         ttl                      : 0x000004b0 (1200)
         length                   : 0x0004 (4)
         rdata                    : union dns_rdata(case 0x1)
         ipv4_record              : 192.168.1.42
         unexpected               : DATA_BLOB length=0

Everything on the lan is working fine but why doesn't the ping work to 
the clients? Nothing seems to be written to the forward zone on the DC.
Cheers,
Steve