Improve debug information in DNS responses

nameserver/response.go

@@ -1,36 +1,55 @@
 package nameserver
 
 import (
+	"context"
+	"fmt"
+
 	"github.com/miekg/dns"
 	"github.com/safing/portbase/log"
 	"github.com/safing/portmaster/nameserver/nsutil"
-	"github.com/safing/portmaster/network"
 )
 
-// sendResponse sends a response to query using w. If reasonCtx is not
-// nil and implements either the Responder or RRProvider interface then
-// those functions are used to craft a DNS response. If reasonCtx is nil
-// or does not implement the Responder interface and verdict is not set
-// to failed a ZeroIP response will be sent. If verdict is set to failed
-// then a ServFail will be sent instead.
-func sendResponse(w dns.ResponseWriter, query *dns.Msg, verdict network.Verdict, reason string, reasonCtx interface{}) {
-	responder, ok := reasonCtx.(nsutil.Responder)
-	if !ok {
-		if verdict == network.VerdictFailed {
-			responder = nsutil.ServeFail()
-		} else {
-			responder = nsutil.ZeroIP()
-		}
+// sendResponse sends a response to query using w. The response message is
+// created by responder. If addExtraRRs is not nil and implements the
+// RRProvider interface then it will be also used to add more RRs in the
+// extra section.
+func sendResponse(
+	ctx context.Context,
+	w dns.ResponseWriter,
+	request *dns.Msg,
+	responder nsutil.Responder,
+	rrProviders ...nsutil.RRProvider,
+) error {
+	// Have the Responder craft a DNS reply.
+	reply := responder.ReplyWithDNS(ctx, request)
+	if reply == nil {
+		// Dropping query.
+		return nil
 	}
 
-	reply := responder.ReplyWithDNS(query, reason, reasonCtx)
-
-	if extra, ok := reasonCtx.(nsutil.RRProvider); ok {
-		rrs := extra.GetExtraRR(query, reason, reasonCtx)
+	// Add extra RRs through a custom RRProvider.
+	for _, rrProvider := range rrProviders {
+		rrs := rrProvider.GetExtraRRs(ctx, request)
 		reply.Extra = append(reply.Extra, rrs...)
 	}
 
+	// Write reply.
 	if err := writeDNSResponse(w, reply); err != nil {
-		log.Errorf("nameserver: failed to send response: %s", err)
+		return fmt.Errorf("nameserver: failed to send response: %w", err)
 	}
+
+	return nil
+}
+
+func writeDNSResponse(w dns.ResponseWriter, m *dns.Msg) (err error) {
+	defer func() {
+		// recover from panic
+		if panicErr := recover(); panicErr != nil {
+			err = fmt.Errorf("panic: %s", panicErr)
+			log.Warningf("nameserver: panic caused by this msg: %#v", m)
+		}
+	}()
+
+	err = w.WriteMsg(m)
+	return
 }