This hook can be used to coordinate disabling an analyzer for a given
connection. The contract is simple: Any script can veto a disable_analyzer()
call by breaking from this hook. The decision is local to the script taking
into account any state attached to the connection object or script specific
state stored elsewhere.
A script breaking from the hook takes over the responsibility to call
disable_analyzer() at a later point when it finds the condition due to which
it vetoed fulfilled (which may be never).
Signature:
disabling_analyzer: hook(c: connection, atype: AllAnalyzers::Tag, aid: count);
Example use-cases are keeping the SSL analyzer enabled for finger-printing
until a certain amount of bytes or packets have been transferred or
similarly the connection duration exceed a certain threshold.
Other example use-cases might be keeping analyzers for SSH, RDP or SSL
enabled for connections from specific subnets.
It's a bit quirky as it makes disable_analyzer() a maybe operation. While log
policy hooks and/or the notice hook have similar semantics, they are not as
stateful. It still seems like a quite powerful primitive.
The disable_analyzer() call in dpd/main.zeek may motivate the addition of a
force flag as a follow-up for situations where the caller "knows better" or
absolutely wants to override.
Closes#1678#1593.
