#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 {