libnetwork: improve logs for DNS failures

Signed-off-by: Yamazaki Masashi <masi19bw@gmail.com>

libnetwork: fix function call

Signed-off-by: Yamazaki Masashi <masi19bw@gmail.com>

libnetwork/resolver.go

@@ -501,7 +501,7 @@ func (r *resolver) ServeDNS(w dns.ResponseWriter, query *dns.Msg) {
 			// client can retry over TCP
 			if err != nil && (resp == nil || !resp.Truncated) {
 				r.forwardQueryEnd()
-				logrus.WithError(err).Debugf("[resolver] failed to read from DNS server")
+				logrus.WithError(err).Warnf("[resolver] failed to read from DNS server: %s, query: %s", extConn.RemoteAddr().String(), query.Question[0].String())
 				continue
 			}
 			r.forwardQueryEnd()