control/controlclient: refactor some internals

Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>

control/controlclient/direct.go

@@ -274,7 +274,7 @@ func (c *Direct) TryLogout(ctx context.Context) error {
 
 func (c *Direct) TryLogin(ctx context.Context, t *tailcfg.Oauth2Token, flags LoginFlags) (url string, err error) {
 	c.logf("direct.TryLogin(token=%v, flags=%v)", t != nil, flags)
-	return c.doLoginOrRegen(ctx, t, flags, false, "")
+	return c.doLoginOrRegen(ctx, loginOpt{Token: t, Flags: flags})
 }
 
 // WaitLoginURL sits in a long poll waiting for the user to authenticate at url.
@@ -282,22 +282,29 @@ func (c *Direct) TryLogin(ctx context.Context, t *tailcfg.Oauth2Token, flags Log
 // On success, newURL and err will both be nil.
 func (c *Direct) WaitLoginURL(ctx context.Context, url string) (newURL string, err error) {
 	c.logf("direct.WaitLoginURL")
-	return c.doLoginOrRegen(ctx, nil, LoginDefault, false, url)
+	return c.doLoginOrRegen(ctx, loginOpt{URL: url})
 }
 
-func (c *Direct) doLoginOrRegen(ctx context.Context, t *tailcfg.Oauth2Token, flags LoginFlags, regen bool, url string) (newURL string, err error) {
-	mustregen, url, err := c.doLogin(ctx, t, flags, regen, url)
+func (c *Direct) doLoginOrRegen(ctx context.Context, opt loginOpt) (newURL string, err error) {
+	mustRegen, url, err := c.doLogin(ctx, opt)
 	if err != nil {
 		return url, err
 	}
-	if mustregen {
-		_, url, err = c.doLogin(ctx, t, flags, true, url)
+	if mustRegen {
+		opt.Regen = true
+		_, url, err = c.doLogin(ctx, opt)
 	}
-
 	return url, err
 }
 
-func (c *Direct) doLogin(ctx context.Context, t *tailcfg.Oauth2Token, flags LoginFlags, regen bool, url string) (mustregen bool, newurl string, err error) {
+type loginOpt struct {
+	Token *tailcfg.Oauth2Token
+	Flags LoginFlags
+	Regen bool
+	URL   string
+}
+
+func (c *Direct) doLogin(ctx context.Context, opt loginOpt) (mustRegen bool, newURL string, err error) {
 	c.mu.Lock()
 	persist := c.persist
 	tryingNewKey := c.tryingNewKey
@@ -316,22 +323,23 @@ func (c *Direct) doLogin(ctx context.Context, t *tailcfg.Oauth2Token, flags Logi
 		return false, "", errors.New("getMachinePrivKey returned zero key")
 	}
 
+	regen := opt.Regen
 	if expired {
 		c.logf("Old key expired -> regen=true")
 		systemd.Status("key expired; run 'tailscale up' to authenticate")
 		regen = true
 	}
-	if (flags & LoginInteractive) != 0 {
+	if (opt.Flags & LoginInteractive) != 0 {
 		c.logf("LoginInteractive -> regen=true")
 		regen = true
 	}
 
-	c.logf("doLogin(regen=%v, hasUrl=%v)", regen, url != "")
+	c.logf("doLogin(regen=%v, hasUrl=%v)", regen, opt.URL != "")
 	if serverKey.IsZero() {
 		var err error
 		serverKey, err = loadServerKey(ctx, c.httpc, c.serverURL)
 		if err != nil {
-			return regen, url, err
+			return regen, opt.URL, err
 		}
 
 		c.mu.Lock()
@@ -340,14 +348,14 @@ func (c *Direct) doLogin(ctx context.Context, t *tailcfg.Oauth2Token, flags Logi
 	}
 
 	var oldNodeKey wgkey.Key
-	if url != "" {
+	if opt.URL != "" {
 	} else if regen || persist.PrivateNodeKey.IsZero() {
 		c.logf("Generating a new nodekey.")
 		persist.OldPrivateNodeKey = persist.PrivateNodeKey
 		key, err := wgkey.NewPrivate()
 		if err != nil {
 			c.logf("login keygen: %v", err)
-			return regen, url, err
+			return regen, opt.URL, err
 		}
 		tryingNewKey = key
 	} else {
@@ -363,7 +371,7 @@ func (c *Direct) doLogin(ctx context.Context, t *tailcfg.Oauth2Token, flags Logi
 	}
 	if backendLogID == "" {
 		err = errors.New("hostinfo: BackendLogID missing")
-		return regen, url, err
+		return regen, opt.URL, err
 	}
 	now := time.Now().Round(time.Second)
 	request := tailcfg.RegisterRequest{
@@ -371,13 +379,13 @@ func (c *Direct) doLogin(ctx context.Context, t *tailcfg.Oauth2Token, flags Logi
 		OldNodeKey: tailcfg.NodeKey(oldNodeKey),
 		NodeKey:    tailcfg.NodeKey(tryingNewKey.Public()),
 		Hostinfo:   hostinfo,
-		Followup:   url,
+		Followup:   opt.URL,
 		Timestamp:  &now,
 	}
 	c.logf("RegisterReq: onode=%v node=%v fup=%v",
 		request.OldNodeKey.ShortString(),
-		request.NodeKey.ShortString(), url != "")
-	request.Auth.Oauth2Token = t
+		request.NodeKey.ShortString(), opt.URL != "")
+	request.Auth.Oauth2Token = opt.Token
 	request.Auth.Provider = persist.Provider
 	request.Auth.LoginName = persist.LoginName
 	request.Auth.AuthKey = authKey
@@ -397,31 +405,31 @@ func (c *Direct) doLogin(ctx context.Context, t *tailcfg.Oauth2Token, flags Logi
 	}
 	bodyData, err := encode(request, &serverKey, &machinePrivKey)
 	if err != nil {
-		return regen, url, err
+		return regen, opt.URL, err
 	}
 	body := bytes.NewReader(bodyData)
 
 	u := fmt.Sprintf("%s/machine/%s", c.serverURL, machinePrivKey.Public().HexString())
 	req, err := http.NewRequest("POST", u, body)
 	if err != nil {
-		return regen, url, err
+		return regen, opt.URL, err
 	}
 	req = req.WithContext(ctx)
 
 	res, err := c.httpc.Do(req)
 	if err != nil {
-		return regen, url, fmt.Errorf("register request: %v", err)
+		return regen, opt.URL, fmt.Errorf("register request: %v", err)
 	}
 	if res.StatusCode != 200 {
 		msg, _ := ioutil.ReadAll(res.Body)
 		res.Body.Close()
-		return regen, url, fmt.Errorf("register request: http %d: %.200s",
+		return regen, opt.URL, fmt.Errorf("register request: http %d: %.200s",
 			res.StatusCode, strings.TrimSpace(string(msg)))
 	}
 	resp := tailcfg.RegisterResponse{}
 	if err := decode(res, &resp, &serverKey, &machinePrivKey); err != nil {
 		c.logf("error decoding RegisterResponse with server key %s and machine key %s: %v", serverKey, machinePrivKey.Public(), err)
-		return regen, url, fmt.Errorf("register request: %v", err)
+		return regen, opt.URL, fmt.Errorf("register request: %v", err)
 	}
 	// Log without PII:
 	c.logf("RegisterReq: got response; nodeKeyExpired=%v, machineAuthorized=%v; authURL=%v",