plugin/log - Support for Metadata (#2251)

* - add metadata support to Log

* - adapt ctx after rebase

plugin/log/README.md

@@ -61,6 +61,7 @@ The following place holders are supported:
 * `{class}`: qclass of the request
 * `{proto}`: protocol used (tcp or udp)
 * `{remote}`: client's IP address, for IPv6 addresses these are enclosed in brackets: `[::1]`
+* `{local}`: server's IP address, for IPv6 addresses these are enclosed in brackets: `[::1]`
 * `{size}`: request size in bytes
 * `{port}`: client's port
 * `{duration}`: response duration
@@ -72,6 +73,10 @@ The following place holders are supported:
 * `{>do}`: is the EDNS0 DO (DNSSEC OK) bit set in the query
 * `{>id}`: query ID
 * `{>opcode}`: query OPCODE
+* `{/[LABEL]}`: any metadata label is accepted as a place holder if it is enclosed between `{/` and  `}`.
+the place holder will be replaced by the corresponding metadata value or the default value `-` if label is not defined.
+
+
 
 The default Common Log Format is:
 

plugin/log/log.go

@@ -57,7 +57,7 @@ func (l Logger) ServeDNS(ctx context.Context, w dns.ResponseWriter, r *dns.Msg)
 		// If we don't set up a class in config, the default "all" will be added
 		// and we shouldn't have an empty rule.Class.
 		if rule.Class[response.All] || rule.Class[class] {
-			rep := replacer.New(r, rrw, CommonLogEmptyValue)
+			rep := replacer.New(ctx, r, rrw, CommonLogEmptyValue)
 			clog.Infof(rep.Replace(rule.Format))
 		}