Update metrics config documentation

nsd.conf.5.in

@@ -603,6 +603,30 @@ The port number for proxy protocol service. If the statement is given multiple
 times, additional port numbers can be used for proxy protocol service. The
 interface definitions that use this port number expect PROXYv2 proxy protocol
 traffic, for UDP, TCP and for TLS service.
+.TP
+.B metrics\-enable:\fR <yes or no>
+Enable the prometheus metrics HTTP endpoint. It exposes the same statistics as
+the \fInsd\-control\fR(8) stats_noreset command, but with metric names
+following the prometheus specification.
+
+Beware, that when using \fInsd\-control\fR(8) stats (instead of stats_noreset),
+the statistics will be reset for the HTTP metrics endpoint as well.
+.TP
+.B metrics\-interface:\fR <ip4 or ip6 | interface name>
+NSD will bind to the listed addresses or interfaces to serve the prometheus
+metrics. Can be given multiple times to bind multiple ip\-addresses. Use
+0.0.0.0 and ::0 to bind to the wildcard interface.
+
+If an interface name is used instead of ip4 or ip6, the list of IP addresses
+associated with that interface is picked up and used at server start.
+
+Default is 127.0.0.1 and ::1.
+.TP
+.B metrics\-port:\fR <number>
+The port number for the HTTP service. Default is 9100.
+.TP
+.B metrics\-path:\fR <string>
+The HTTP path to expose the metrics at. Default is /metrics.
 .SS "Remote Control"
 The
 .B remote\-control:

nsd.conf.sample.in

@@ -283,6 +283,23 @@ server:
 	# expect PROXYv2. For UDP and TCP/TLS interfaces.
 	# proxy-protocol-port: portno for each of the port numbers.
 
+	# Enable the prometheus metrics HTTP endpoint. Default is no.
+	# metrics-enable: no
+
+	# Interfaces to expose the HTTP endpoint on, default is on localhost.
+	# Interfaces can be specified by IP address or interface name.
+	# With an interface name, all IP addresses associated with that
+	# interface are used. Default is 127.0.0.1 and ::1.
+	# metrics-interface: 127.0.0.1
+	# metrics-interface: ::1
+	# metrics-interface: lo
+
+	# Port number for the HTTP metrics endpoint. Default is 9100.
+	# metrics-port: 9100
+
+	# HTTP path for the metrics endpoint. Default is /metrics.
+	# metrics-path: "/metrics"
+
 verify:
 	# Enable zone verification. Default is no.
 	# enable: no