Introduce metrics_port to supervisor and management framework.

This only adds the port value in the various required places. Its actual use
follows in the next commits.

scripts/base/frameworks/supervisor/api.zeek

@@ -30,6 +30,8 @@ export {
 		## The PCAP file name from which the node will read/analyze packets.
 		## Typically used by worker nodes.
 		pcap_file: string &optional;
+		## The TCP port at which the cluster node exposes metrics for Prometheus.
+		metrics_port: port &optional;
 	};
 
 	## Configuration options that influence behavior of a supervised Zeek node.

scripts/policy/frameworks/management/agent/main.zeek

@@ -521,6 +521,9 @@ function deploy_request_finish(areq: Management::Request::Request)
 		if ( node?$interface )
 			cep$interface = node$interface;
 
+		if ( node?$metrics_port )
+			cep$metrics_port = node$metrics_port;
+
 		g_cluster[node$name] = cep;
 		}
 
@@ -630,6 +633,9 @@ function get_nodes_request_finish(areq: Management::Request::Request)
 			# serialization always assumes TCP.
 			if ( sns$node$cluster[node]$p != 0/tcp )
 				cns$p = sns$node$cluster[node]$p;
+
+			if ( sns$node$cluster[node]?$metrics_port )
+				cns$metrics_port = sns$node$cluster[node]$metrics_port;
 			}
 		else
 			{

scripts/policy/frameworks/management/types.zeek

@@ -60,6 +60,7 @@ export {
 		interface: string &optional;         ##< Interface to sniff
 		cpu_affinity: int &optional;         ##< CPU/core number to pin to
 		env: table[string] of string &default=table(); ##< Custom environment vars
+		metrics_port: port &optional;        ##< Metrics exposure port for Prometheus
 	};
 
 	## Data structure capturing a cluster's complete configuration.
@@ -88,6 +89,8 @@ export {
 		pid: int &optional;
 		## The node's Broker peering listening port, if any.
 		p: port &optional;
+		## The node's metrics port for Prometheus, if any.
+		metrics_port: port &optional;
 	};
 
 	type NodeStatusVec: vector of NodeStatus;

src/supervisor/Supervisor.cc

@@ -1269,6 +1269,11 @@ Supervisor::NodeConfig Supervisor::NodeConfig::FromRecord(const RecordVal* node)
         if ( pcap_file )
             ep.pcap_file = pcap_file->AsStringVal()->ToStdString();
 
+        const auto& metrics_port = rv->GetField("metrics_port");
+
+        if ( metrics_port )
+            ep.metrics_port = rv->GetFieldAs<PortVal>("metrics_port")->Port();
+
         rval.cluster.emplace(name, std::move(ep));
     }
 
@@ -1337,6 +1342,9 @@ Supervisor::NodeConfig Supervisor::NodeConfig::FromJSON(std::string_view json) {
         if ( auto it = val.FindMember("pcap_file"); it != val.MemberEnd() )
             ep.pcap_file = it->value.GetString();
 
+        if ( auto it = val.FindMember("metrics_port"); it != val.MemberEnd() )
+            ep.metrics_port = it->value["port"].GetInt();
+
         rval.cluster.emplace(key, std::move(ep));
     }
 
@@ -1421,6 +1429,9 @@ RecordValPtr Supervisor::NodeConfig::ToRecord() const {
         if ( ep.pcap_file )
             val->AssignField("pcap_file", *ep.pcap_file);
 
+        if ( ep.metrics_port )
+            val->AssignField("metrics_port", val_mgr->Port(*ep.metrics_port, TRANSPORT_TCP));
+
         cluster_val->Assign(std::move(key), std::move(val));
     }
 
@@ -1488,6 +1499,9 @@ bool SupervisedNode::InitCluster() const {
         if ( manager_name && ep.role != BifEnum::Supervisor::MANAGER )
             val->AssignField("manager", *manager_name);
 
+        if ( ep.metrics_port )
+            val->AssignField("metrics_port", val_mgr->Port(*ep.metrics_port, TRANSPORT_TCP));
+
         cluster_nodes->Assign(std::move(key), std::move(val));
     }
 
@@ -1551,6 +1565,14 @@ void SupervisedNode::Init(Options* options) const {
             fprintf(stderr, "node '%s' failed to setenv: %s\n", node_name.data(), strerror(errno));
             exit(1);
         }
+
+        if ( const auto& ep = config.cluster.find(node_name); ep != config.cluster.end() && ep->second.metrics_port ) {
+            auto metrics_port_str = std::to_string(*(ep->second.metrics_port));
+            if ( setenv("ZEEK_METRICS_PORT", metrics_port_str.c_str(), true) == -1 ) {
+                fprintf(stderr, "metrics port '%s' failed to setenv: %s\n", metrics_port_str.c_str(), strerror(errno));
+                exit(1);
+            }
+        }
     }
 
     options->filter_supervised_node_options();

src/supervisor/Supervisor.h

@@ -137,6 +137,10 @@ public:
          * Typically used by worker nodes.
          */
         std::optional<std::string> pcap_file;
+        /**
+         * The TCP port number at which the cluster node exposes metrics for Prometheus.
+         */
+        std::optional<int> metrics_port;
     };
 
     /**