#2140 Fixed reflection of hostname change (#2199)

* #2140 Fixed updating of hostname and givenName when it is updated in HostInfo

* #2140 Added integration tests

* #2140 Fix unit tests

* Changed IsAutomaticNameMode to GivenNameHasBeenChanged. Fixed errors in files according to golangci-lint rules

hscontrol/types/node.go

@@ -97,6 +97,11 @@ type (
 	Nodes []*Node
 )
 
+// GivenNameHasBeenChanged returns whether the `givenName` can be automatically changed based on the `Hostname` of the node.
+func (node *Node) GivenNameHasBeenChanged() bool {
+	return node.GivenName == util.ConvertWithFQDNRules(node.Hostname)
+}
+
 // IsExpired returns whether the node registration has expired.
 func (node Node) IsExpired() bool {
 	// If Expiry is not set, the client has not indicated that
@@ -347,6 +352,21 @@ func (node *Node) RegisterMethodToV1Enum() v1.RegisterMethod {
 	}
 }
 
+// ApplyHostnameFromHostInfo takes a Hostinfo struct and updates the node.
+func (node *Node) ApplyHostnameFromHostInfo(hostInfo *tailcfg.Hostinfo) {
+	if hostInfo == nil {
+		return
+	}
+
+	if node.Hostname != hostInfo.Hostname {
+		if node.GivenNameHasBeenChanged() {
+			node.GivenName = util.ConvertWithFQDNRules(hostInfo.Hostname)
+		}
+
+		node.Hostname = hostInfo.Hostname
+	}
+}
+
 // ApplyPeerChange takes a PeerChange struct and updates the node.
 func (node *Node) ApplyPeerChange(change *tailcfg.PeerChange) {
 	if change.Key != nil {

hscontrol/types/node_test.go

@@ -337,6 +337,66 @@ func TestPeerChangeFromMapRequest(t *testing.T) {
 	}
 }
 
+func TestApplyHostnameFromHostInfo(t *testing.T) {
+	tests := []struct {
+		name       string
+		nodeBefore Node
+		change     *tailcfg.Hostinfo
+		want       Node
+	}{
+		{
+			name: "hostinfo-not-exists",
+			nodeBefore: Node{
+				GivenName: "manual-test.local",
+				Hostname:  "TestHost.Local",
+			},
+			change: nil,
+			want: Node{
+				GivenName: "manual-test.local",
+				Hostname:  "TestHost.Local",
+			},
+		},
+		{
+			name: "hostinfo-exists-no-automatic-givenName",
+			nodeBefore: Node{
+				GivenName: "manual-test.local",
+				Hostname:  "TestHost.Local",
+			},
+			change: &tailcfg.Hostinfo{
+				Hostname: "NewHostName.Local",
+			},
+			want: Node{
+				GivenName: "manual-test.local",
+				Hostname:  "NewHostName.Local",
+			},
+		},
+		{
+			name: "hostinfo-exists-automatic-givenName",
+			nodeBefore: Node{
+				GivenName: "automaticname.test",
+				Hostname:  "AutomaticName.Test",
+			},
+			change: &tailcfg.Hostinfo{
+				Hostname: "NewHostName.Local",
+			},
+			want: Node{
+				GivenName: "newhostname.local",
+				Hostname:  "NewHostName.Local",
+			},
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			tt.nodeBefore.ApplyHostnameFromHostInfo(tt.change)
+
+			if diff := cmp.Diff(tt.want, tt.nodeBefore, util.Comparers...); diff != "" {
+				t.Errorf("Patch unexpected result (-want +got):\n%s", diff)
+			}
+		})
+	}
+}
+
 func TestApplyPeerChange(t *testing.T) {
 	tests := []struct {
 		name       string