chore: allow to specify several endpoints

This change relies on protobuf spec, where it doesn't matter how many times the field appears in the byte stream, because decoder will always take the last one for non-repeated fields. We use it to our advantage and simply pass primary endpoint address at the end, but we take it as the first.

Signed-off-by: Dmitriy Matrenichev <dmitry.matrenichev@siderolabs.com>

api/siderolink/provision.go

@@ -0,0 +1,41 @@
+// This Source Code Form is subject to the terms of the Mozilla Public
+// License, v. 2.0. If a copy of the MPL was not distributed with this
+// file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+// Package pb provides protobuf definitions for the SideroLink API.
+package pb
+
+import (
+	"errors"
+	"slices"
+)
+
+// MakeEndpoints sets the endpoints.
+func MakeEndpoints(endpoints ...string) []string {
+	if len(endpoints) == 0 {
+		panic(errors.New("no endpoints provided"))
+	}
+
+	// To preserve GRPC backwards compatibility, we put the first endpoint at the end.
+	if len(endpoints) > 1 {
+		endpoints[0], endpoints[len(endpoints)-1] = endpoints[len(endpoints)-1], endpoints[0]
+	}
+
+	return endpoints
+}
+
+// GetEndpoints returns the endpoints.
+func (m *ProvisionResponse) GetEndpoints() []string {
+	if m == nil || len(m.ServerEndpoint) == 0 {
+		return nil
+	}
+
+	endpoints := slices.Clone(m.ServerEndpoint)
+
+	// To preserve GRPC backwards compatibility, we put the first endpoint at the end.
+	if len(endpoints) > 1 {
+		endpoints[0], endpoints[len(endpoints)-1] = endpoints[len(endpoints)-1], endpoints[0]
+	}
+
+	return endpoints
+}

api/siderolink/provision.proto

@@ -27,7 +27,7 @@ message ProvisionRequest {
 
 message ProvisionResponse {
     // Server Wireguard endpoint IP and port.
-    string server_endpoint = 1;
+    repeated string server_endpoint = 1;
     // Server public Wireguard key encoded as string.
     string server_public_key = 3;
     // Node address with prefix on the Wireguard tunnel.

internal/server/server.go

@@ -93,7 +93,7 @@ func (srv *Server) Provision(_ context.Context, req *pb.ProvisionRequest) (*pb.P
 	)
 
 	return &pb.ProvisionResponse{
-		ServerEndpoint:    srv.cfg.ServerEndpoint.String(),
+		ServerEndpoint:    pb.MakeEndpoints(srv.cfg.ServerEndpoint.String()),
 		ServerPublicKey:   srv.cfg.ServerPublicKey.String(),
 		ServerAddress:     srv.cfg.ServerAddress.String(),
 		NodeAddressPrefix: nodeAddress.String(),

pkg/events/sink_test.go

@@ -49,8 +49,8 @@ func (s *state) HandleEvent(_ context.Context, e events.Event) error {
 	case *pb.ProvisionRequest:
 		s.NodeUUIDs = append(s.NodeUUIDs, msg.NodeUuid)
 	case *pb.ProvisionResponse:
-		if msg.ServerEndpoint != "" {
-			s.ServerEndpoints = append(s.ServerEndpoints, msg.ServerEndpoint)
+		if ep := msg.GetEndpoints(); ep != nil {
+			s.ServerEndpoints = append(s.ServerEndpoints, ep...)
 		}
 
 		if msg.ServerAddress != "" {
@@ -127,7 +127,7 @@ func (suite *SinkSuite) TestPublish() {
 			ServerAddress: "foo",
 		},
 		&pb.ProvisionResponse{
-			ServerEndpoint: "bar:123",
+			ServerEndpoint: []string{"bar:123"},
 		},
 	}