cmd/hello: chop DNS name at first dot

cmd/hello/hello.go

@@ -131,7 +131,7 @@ func root(w http.ResponseWriter, r *http.Request) {
 			DisplayName:   who.UserProfile.DisplayName,
 			LoginName:     who.UserProfile.LoginName,
 			ProfilePicURL: who.UserProfile.ProfilePicURL,
-			MachineName:   who.Node.ComputedName,
+			MachineName:   firstLabel(who.Node.ComputedName),
 			MachineOS:     who.Node.Hostinfo.OS,
 			IP:            ip,
 		}
@@ -140,6 +140,14 @@ func root(w http.ResponseWriter, r *http.Request) {
 	tmpl.Execute(w, data)
 }
 
+// firstLabel s up until the first period, if any.
+func firstLabel(s string) string {
+	if i := strings.Index(s, "."); i != -1 {
+		return s[:i]
+	}
+	return s
+}
+
 // tsSockClient does HTTP requests to the local Tailscale daemon.
 // The hostname in the HTTP request is ignored.
 var tsSockClient = &http.Client{