plugin/proxy: return client error (#1646)

Return the client error if there was one instead of the generic
"no healthy upstream or error"

1 files changed, 7 insertions, 1 deletions

diff --git a/plugin/forward/forward.go b/plugin/forward/forward.go
index 34864d4a3..96b7e4c24 100644
--- a/plugin/forward/forward.go
+++ b/plugin/forward/forward.go
@@ -65,6 +65,7 @@ func (f *Forward) ServeDNS(ctx context.Context, w dns.ResponseWriter, r *dns.Msg
 
 	fails := 0
 	var span, child ot.Span
+	var upstreamErr error
 	span = ot.SpanFromContext(ctx)
 
 	for _, proxy := range f.list() {
@@ -93,6 +94,7 @@ func (f *Forward) ServeDNS(ctx context.Context, w dns.ResponseWriter, r *dns.Msg
 		}
 
 		ret, err = truncated(ret, err)
+		upstreamErr = err
 
 		if err != nil {
 			// Kick off health check to see if *our* upstream is broken.
@@ -124,6 +126,10 @@ func (f *Forward) ServeDNS(ctx context.Context, w dns.ResponseWriter, r *dns.Msg
 		return 0, nil
 	}
 
+	if upstreamErr != nil {
+		return dns.RcodeServerFailure, upstreamErr
+	}
+
 	return dns.RcodeServerFailure, errNoHealthy
 }
 
@@ -155,7 +161,7 @@ func (f *Forward) list() []*Proxy { return f.p.List(f.proxies) }
 
 var (
 	errInvalidDomain = errors.New("invalid domain for forward")
-	errNoHealthy     = errors.New("no healthy proxies or upstream error")
+	errNoHealthy     = errors.New("no healthy proxies")
 	errNoForward     = errors.New("no forwarder defined")
 )