nodemap: Extend fake node map for use in tests

The fake node ID map currently only defines the minimum set of functions
needed for the interface. This commit extends it to simulate the actual
behavior of the BPF map with an in-memory Golang map.

This will allow us to use check that the map content matches our
expectations for various events of the node object lifecycle.

Signed-off-by: Paul Chaignon <paul.chaignon@gmail.com>

pkg/maps/nodemap/fake/node_map.go

@@ -4,28 +4,42 @@
 package fake
 
 import (
+	"fmt"
 	"net"
 
 	"github.com/cilium/cilium/pkg/maps/nodemap"
 )
 
 type fakeNodeMap struct {
+	ids map[string]uint16
 }
 
 var _ nodemap.Map = &fakeNodeMap{}
 
 func NewFakeNodeMap() *fakeNodeMap {
-	return &fakeNodeMap{}
+	return &fakeNodeMap{
+		ids: map[string]uint16{},
+	}
 }
 
 func (f fakeNodeMap) Update(ip net.IP, nodeID uint16) error {
+	f.ids[ip.String()] = nodeID
 	return nil
 }
 
 func (f fakeNodeMap) Delete(ip net.IP) error {
+	delete(f.ids, ip.String())
 	return nil
 }
 
+// This function is used only for tests.
+func (f fakeNodeMap) Lookup(ip net.IP) (uint16, error) {
+	if nodeID, exists := f.ids[ip.String()]; exists {
+		return nodeID, nil
+	}
+	return 0, fmt.Errorf("IP not found in node ID map")
+}
+
 func (f fakeNodeMap) IterateWithCallback(cb nodemap.NodeIterateCallback) error {
 	return nil
 }