state: auto-approve routes after an admin tag change

The new tags may approve announced routes. Approval runs once the policy
manager knows the new owner, as after a registration.

hscontrol/servertest/reauth_compat_test.go

@@ -39,10 +39,6 @@ import (
 var reauthSkipReasons = map[string]string{
 	"owner-routes/r-expired-retag/expire/online": expiredPeerOffline,
 
-	"owner-routes/r-admin/owner/enabled":     adminRetagNoApproval,
-	"owner-routes/r-admin/owner/served":      adminRetagNoApproval,
-	"owner-routes/r-admin/owner/self-routes": adminRetagNoApproval,
-
 	"identity/w-tagreq-relogin-tags/w-tagreq/owner":        keyLoginTagsRefused,
 	"identity/w-tagreq-relogin-tags/w-tagreq/outcome":      keyLoginTagsRefused,
 	"identity/w-tagreq-relogin-tags/w-tagreq/node-key":     keyLoginTagsRefused,
@@ -81,10 +77,6 @@ var reauthSkipReasons = map[string]string{
 	"ephemeral-lifecycle/late-expired/late-exp/legacy-text": refusalText,
 }
 
-const (
-	adminRetagNoApproval = "ADMIN_RETAG_NO_APPROVAL: an admin tag change does not auto-approve the routes the new tags may approve; SaaS approves them at once"
-)
-
 const (
 	keyLoginTagsRefused      = "KEY_LOGIN_TAGS_REFUSED: headscale refuses a user's key login that requests tags the user owns; SaaS tags the device, converting it in place or creating it tagged"
 	taggedKeyOwnedTagRefused = "TAGGED_KEY_OWNED_TAG_REFUSED: headscale refuses a tagged key's login that requests a tag the key's tags own; SaaS gives the device the requested tags"

hscontrol/state/autoapprove_test.go

@@ -349,3 +349,27 @@ func TestRegistrationDropsWithdrawnAutoApprovals(t *testing.T) {
 	require.NoError(t, err)
 	assert.Equal(t, []netip.Prefix{kept}, approvedRoutes(t, s, node.ID()))
 }
+
+// TestAdminTagChangeApprovesRoutes: an admin tag change runs route
+// auto-approval for the routes the new tags may approve.
+func TestAdminTagChangeApprovesRoutes(t *testing.T) {
+	_, s, id := persistTestSetup(t)
+	t.Cleanup(func() { _ = s.Close() })
+
+	_, err := s.SetPolicy([]byte(`{
+		"tagOwners": {"tag:router": ["persist-user@"]},
+		"autoApprovers": {"routes": {"10.0.0.0/16": ["tag:router"]}},
+		"acls": [{"action": "accept", "src": ["*"], "dst": ["*:*"]}]
+	}`))
+	require.NoError(t, err)
+
+	route := netip.MustParsePrefix("10.0.1.0/24")
+
+	announce(t, s, id, route)
+	require.Empty(t, approvedRoutes(t, s, id), "the user may not approve it")
+
+	node, _, err := s.SetNodeTags(id, []string{"tag:router"})
+	require.NoError(t, err)
+	assert.Equal(t, []netip.Prefix{route}, node.ApprovedRoutes().AsSlice())
+	assert.Equal(t, []netip.Prefix{route}, approvedRoutes(t, s, id))
+}

hscontrol/state/state.go

@@ -1150,6 +1150,20 @@ func (s *State) SetNodeTags(nodeID types.NodeID, tags []string) (types.NodeView,
 	// Setting OriginNode ensures the node gets a self-update with the new tags.
 	c.OriginNode = nodeID
 
+	// The new tags may approve announced routes, as on Tailscale SaaS. This
+	// runs after the policy refresh above, which teaches the policy manager
+	// the node's new owner.
+	routesChange, err := s.AutoApproveRoutes(nodeView)
+	c = c.Merge(routesChange)
+
+	if fresh, ok := s.nodeStore.GetNode(nodeID); ok {
+		nodeView = fresh
+	}
+
+	if err != nil {
+		return nodeView, c, fmt.Errorf("auto approving routes: %w", err)
+	}
+
 	return nodeView, c, nil
 }