zeek/scripts/base/frameworks/netcontrol/shunt.zeek
Benjamin Bannier d5fd29edcd Prefer explicit construction to coercion in record initialization
While we support initializing records via coercion from an expression
list, e.g.,

    local x: X = [$x1=1, $x2=2];

this can sometimes obscure the code to readers, e.g., when assigning to
value declared and typed elsewhere. The language runtime has a similar
overhead since instead of just constructing a known type it needs to
check at runtime that the coercion from the expression list is valid;
this can be slower than just writing the readible code in the first
place, see #4559.

With this patch we use explicit construction, e.g.,

    local x = X($x1=1, $x2=2);
2025-07-11 16:28:37 -07:00

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##! Implementation of the shunt functionality for NetControl.
module NetControl;
@load ./main
export {
redef enum Log::ID += { SHUNT };
global log_policy_shunt: Log::PolicyHook;
## Stops forwarding a uni-directional flow's packets to Zeek.
##
## f: The flow to shunt.
##
## t: How long to leave the shunt in place, with 0 being indefinitely.
##
## location: An optional string describing where the shunt was triggered.
##
## Returns: The id of the inserted rule on success and zero on failure.
global shunt_flow: function(f: flow_id, t: interval, location: string &default="") : string;
type ShuntInfo: record {
## Time at which the recorded activity occurred.
ts: time &log;
## ID of the rule; unique during each Zeek run.
rule_id: string &log;
## Flow ID of the shunted flow.
f: flow_id &log;
## Expiry time of the shunt.
expire: interval &log;
## Location where the underlying action was triggered.
location: string &log &optional;
};
## Event that can be handled to access the :zeek:type:`NetControl::ShuntInfo`
## record as it is sent on to the logging framework.
global log_netcontrol_shunt: event(rec: ShuntInfo);
}
event zeek_init() &priority=5
{
Log::create_stream(NetControl::SHUNT, Log::Stream($columns=ShuntInfo, $ev=log_netcontrol_shunt, $path="netcontrol_shunt", $policy=log_policy_shunt));
}
function shunt_flow(f: flow_id, t: interval, location: string &default="") : string
{
local flow = NetControl::Flow(
$src_h=addr_to_subnet(f$src_h),
$src_p=f$src_p,
$dst_h=addr_to_subnet(f$dst_h),
$dst_p=f$dst_p
);
local e = Entity($ty=FLOW, $flow=flow);
local r = Rule($ty=DROP, $target=MONITOR, $entity=e, $expire=t, $location=location);
local id = add_rule(r);
# Error should already be logged
if ( id == "" )
return id;
local log = ShuntInfo($ts=network_time(), $rule_id=id, $f=f, $expire=t);
if ( location != "" )
log$location=location;
Log::write(SHUNT, log);
return id;
}