Feature request: exclude IP/network in allow_nets extra field

[Zhang Huangbin]

Dear all,

We use `allow_nets`[1] to restrict login clients, it works fine.
Recently we need to allow some users to login from everywhere except some IP/networks, how can we accomplish this with "allow_nets"?

Tried allow_nets="!a.b.c.d", but Dovecot reports error "allow_nets: Invalid network '!a.b.c.d'".

Can we have this feature?

i guess it should be done in function "auth_request_validate_networks"[2] in file src/auth/auth-request.c.

[1] allow_nets: https://wiki.dovecot.org/PasswordDatabase/ExtraFields/AllowNets
[2] https://github.com/dovecot/core/blob/fbc3ccc4a9a02b82073585a33254eacedc6a9950/src/auth/auth-request.c#L1990