Milter-greylist

Interesting off-topic came up today... I wonder if name resolution
(via res_nquery()) can fall-back to file-based nsswitch as well, or
if it just resolves its host's own name, at least on Solaris?

Today there is a problem with LAN DNS (not available), and the internet
DNS apparently does and should not know names for private IP addresses.
Still, I see the host's own names resolved (yes, not calling greylist
for $self at all - is on the menu):

Aug  5 13:41:59 ucs milter-greylist: [ID 471652 mail.debug] Incoming 
connection from host '[10.0.16.60]'
Aug  5 13:41:59 ucs milter-greylist: [ID 308029 mail.debug] Got an 
unresolved host name [10.0.16.60], will try to resolve
Aug  5 13:41:59 ucs milter-greylist: [ID 682236 mail.debug] Requesting 
PTR entry for 60.16.0.10.in-addr.arpa.
Aug  5 13:41:59 ucs milter-greylist: [ID 646443 mail.debug] Got name 
'ucs.domain.com' (1)
Aug  5 13:41:59 ucs milter-greylist: [ID 779078 mail.debug] User 
jimklimov@... authenticated, bypassing greylisting
Aug  5 13:41:59 ucs milter-greylist: [ID 703198 mail.debug] 
0MR100I02XLZW500: addr = ucs.domain.com[10.0.16.60], from = 
<jimklimov@...>, rcpt = <jim@...>


# nslookup 60.16.0.10.in-addr.arpa. 8.8.8.8
Server:         8.8.8.8
Address:        8.8.8.8#53

** server can't find 60.16.0.10.in-addr.arpa.: NXDOMAIN


# nslookup 10.0.16.60 8.8.8.8
Server:         8.8.8.8
Address:        8.8.8.8#53

Non-authoritative answer:
60.16.0.10.in-addr.arpa name = ucs.domain.com.

Authoritative answers can be found from:

# nslookup -q=ptr 60.16.0.10.in-addr.arpa. 8.8.8.8
Server:         8.8.8.8
Address:        8.8.8.8#53

Non-authoritative answer:
60.16.0.10.in-addr.arpa name = ucs.domain.com.

Authoritative answers can be found from:


I am pretty sure that the name-serivce clients were restarted recently
and the name should not be cached from previous DNS replies... Still,
interesting :)

Other names, including local zones on same machine also with entries
in the /etc/hosts file, are not resolved this way...


# nslookup -q=ptr 61.16.0.10.in-addr.arpa. 8.8.8.8
Server:         8.8.8.8
Address:        8.8.8.8#53

** server can't find 61.16.0.10.in-addr.arpa.: NXDOMAIN


So... here's a random bit of experience to contemplate ;)

HTH,
//Jim