wip: migrate to mono-repo. SPN has already been moved to spn/

service/nameserver/response.go

@@ -0,0 +1,72 @@
+package nameserver
+
+import (
+	"context"
+	"fmt"
+
+	"github.com/miekg/dns"
+
+	"github.com/safing/portbase/log"
+	"github.com/safing/portmaster/service/nameserver/nsutil"
+)
+
+// 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
+	}
+	// Signify that we are a recursive resolver.
+	// While we do not handle recursion directly, we can safely assume, that we
+	// always forward to a recursive resolver.
+	reply.RecursionAvailable = true
+
+	// Add extra RRs through a custom RRProvider.
+	for _, rrProvider := range rrProviders {
+		if rrProvider != nil {
+			rrs := rrProvider.GetExtraRRs(ctx, request)
+			reply.Extra = append(reply.Extra, rrs...)
+		}
+	}
+
+	// Write reply.
+	if err := writeDNSResponse(ctx, w, reply); err != nil {
+		return fmt.Errorf("failed to send response: %w", err)
+	}
+
+	return nil
+}
+
+func writeDNSResponse(ctx context.Context, 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.Tracer(ctx).Debugf("nameserver: panic caused by this msg: %#v", m)
+		}
+	}()
+
+	err = w.WriteMsg(m)
+	if err != nil {
+		// If we receive an error we might have exceeded the message size with all
+		// our extra information records. Retry again without the extra section.
+		log.Tracer(ctx).Tracef("nameserver: retrying to write dns message without extra section, error was: %s", err)
+		m.Extra = nil
+		noExtraErr := w.WriteMsg(m)
+		if noExtraErr == nil {
+			return fmt.Errorf("failed to write dns message without extra section: %w", err)
+		}
+	}
+	return
+}