dns: recreate the DoH forwarder when query fail

When query with DoH forwarder return an error, we assume that there is
a problem with the connection.  To mitigate the problem when subsequent
query using broken connection return an error, we close the forwarder
connection and create a new one.

1 files changed, 13 insertions, 4 deletions

diff --git a/lib/dns/server.go b/lib/dns/server.go
index df6a728d..cc224e2c 100644
--- a/lib/dns/server.go
+++ b/lib/dns/server.go
@@ -700,6 +700,8 @@ func (srv *Server) runForwarders() {
 }
 
 func (srv *Server) runDohForwarder(nameserver string, primaryq, fallbackq chan *request) {
+	var isSuccess bool
+
 	srv.fwGroup.Add(1)
 	log.Printf("dns: starting DoH forwarder at %s", nameserver)
 
@@ -709,7 +711,8 @@ func (srv *Server) runDohForwarder(nameserver string, primaryq, fallbackq chan *
 			log.Fatal("dns: failed to create DoH forwarder: " + err.Error())
 		}
 
-		for srv.isForwarding { //nolint:gosimple
+		isSuccess = true
+		for srv.isForwarding && isSuccess { //nolint:gosimple
 			select {
 			case req, ok := <-primaryq:
 				if !ok {
@@ -727,12 +730,18 @@ func (srv *Server) runDohForwarder(nameserver string, primaryq, fallbackq chan *
 					if fallbackq != nil {
 						fallbackq <- req
 					}
-					continue
+					isSuccess = false
+				} else {
+					srv.processResponse(req, res, fallbackq)
 				}
-
-				srv.processResponse(req, res, fallbackq)
 			}
 		}
+
+		forwarder.Close()
+
+		if srv.isForwarding {
+			log.Println("dns: restarting DoH forwarder for " + nameserver)
+		}
 	}
 out:
 	srv.fwGroup.Done()