pkg/node: give priority to nodeName from K8S_NODE_NAME env variable

If Cilium is running in k8s mode, K8S_NODE_NAME is available so we
can set the node name directly upon node initialization. This prevents
Cilium from setting the node name with a different name at a later
stage as the os.Hostname() can be return a different value than
K8S_NODE_NAME.

Fixes: dbfc2c3 ("k8s: remove waiting for node spec on k8s client init")
Signed-off-by: André Martins <andre@cilium.io>

pkg/node/types/nodename.go

@@ -1,4 +1,4 @@
-// Copyright 2016-2017 Authors of Cilium
+// Copyright 2016-2020 Authors of Cilium
 //
 // Licensed under the Apache License, Version 2.0 (the "License");
 // you may not use this file except in compliance with the License.
@@ -17,6 +17,7 @@ package types
 import (
 	"os"
 
+	k8sConsts "github.com/cilium/cilium/pkg/k8s/constants"
 	"github.com/cilium/cilium/pkg/logging/logfields"
 )
 
@@ -42,6 +43,11 @@ func GetName() string {
 }
 
 func init() {
+	// Give priority to the environment variable available in the Cilium agent
+	if name := os.Getenv(k8sConsts.EnvNodeNameSpec); name != "" {
+		nodeName = name
+		return
+	}
 	if h, err := os.Hostname(); err != nil {
 		log.WithError(err).Warn("Unable to retrieve local hostname")
 	} else {