Hello.

I would like to ask if it would be acceptable to merge feature
into BIND, that would allow using subnet instead of just specific
IP address in the also-notify configuration statement.

Based on documentation and our testing, it is not possible.

The idea is to modify

[ also-notify { ip_addr [port ip_port] [dscp ip_dscp] ;
              [ ip_addr [port ip_port] [dscp ip_dscp] ; ... ] }; ]

to something like

[ also-notify { ip_addr [/length] [port ip_port] [dscp ip_dscp] ;
              [ ip_addr [/length] [port ip_port] [dscp ip_dscp] ; ... ] }; ]

where [/length] would specify the prefix length and if not used
it would default to "32" in case of IPv4 or "128" in case of IPv6.

Another possibility would be to modify the also-notify to accept
"address_match_list". Although I don't think all of its elements
make sense in the context of also-notify (e.g. "key" and the possibility
to negate it using "!").

The use case for this is that one is able to specify the subnet
in allow-transfer statement. However if the administrator needs
to notify all slaves in the subnet, then their IPs need to be
explicitly listed. This may not be feasible if the list is extensive.

I'll start working on the patch once you agree on some of proposed
approaches (and on the feature itself).

Thank you!

Regards,
-- 
Tomas Hozza
Software Engineer - EMEA ENG Developer Experience

PGP: 1D9F3C2D
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