fix: local decoding of MQTT proxy messages in Virtual Node Server (#2358)

[Yeraze]

Summary

Fixes #2358 — MQTT proxy messages (mqttClientProxyMessage) sent to the Virtual Node Server are now locally decoded via the Server Channel Database, so traffic from channels not configured on the physical radio still appears in the UI.

Problem

When an MQTT proxy sends ToRadio.mqttClientProxyMessage to MeshMonitor via TCP, the VNS forwarded it directly to the physical radio without local processing. If the radio didn't have the channel configured, the message was silently dropped and never appeared in the UI.

Solution

• Load mqtt.proto in the protobuf loader for ServiceEnvelope support
• Add decodeServiceEnvelope() to meshtasticProtobufService — extracts MeshPacket from the ServiceEnvelope wrapper
• Intercept mqttClientProxyMessage in handleClientMessage — decodes the envelope, sets viaMqtt=true, wraps in FromRadio, and feeds through processIncomingData() for server-side decryption
• Still forwards to physical radio — the original ToRadio is always forwarded regardless of local processing result

Files Changed

File	Change
src/server/protobufLoader.ts	Load mqtt.proto for ServiceEnvelope support
src/server/meshtasticProtobufService.ts	Add decodeServiceEnvelope() method
src/server/meshtasticProtobufService.test.ts	4 new tests for ServiceEnvelope decoding
src/server/virtualNodeServer.ts	Add mqttClientProxyMessage handling block
src/server/virtualNodeServer.test.ts	4 new tests for MQTT proxy handling

Test plan

• 3052 tests pass, 0 failures
• Build clean (0 TypeScript errors)
• ServiceEnvelope decode: valid envelope, invalid data, missing packet, empty data
• VNS: packet marked viaMqtt, always forwarded to radio, graceful empty data handling

🤖 Generated with Claude Code

[github-actions]

Consider adding more specific error context here to aid debugging:

Suggested change

	if (!data || data.length === 0) {
	if (!data || data.length === 0) {
	logger.debug('decodeServiceEnvelope: Empty or null data provided');
	return null;
	}

This will help distinguish between different failure modes when troubleshooting MQTT proxy issues.

[github-actions]

Consider logging the error details to aid troubleshooting:

Suggested change

	logger.warn('⚠️ Failed to decode ServiceEnvelope:', error);
	logger.warn('⚠️ Failed to decode ServiceEnvelope:', (error as Error).message);

This provides more actionable debugging information for MQTT proxy issues while keeping logs clean.

[github-actions]

Consider adding type safety and input validation:

Suggested change

	const proxyData = proxyMsg.data;
	const proxyData = proxyMsg?.data;
	if (!proxyData || !(proxyData instanceof Uint8Array) || proxyData.length === 0) {
	logger.warn(`Virtual node: MQTT proxy message from ${clientId} has invalid data payload`);
	// Still forward to radio
	logger.info(`Virtual node: Forwarding MQTT proxy message from ${clientId} to physical node`);
	this.queueMessage(clientId, payload);
	return;
	}

This improves robustness by handling edge cases where proxyMsg.data might not be a Uint8Array as expected.

[github-actions]

Consider adding more specific error context:

Suggested change

	} catch (error) {
	} catch (error) {
	logger.error(`Virtual node: Failed to process MQTT proxy message locally from ${clientId}: ${(error as Error).message}`, error);
	// Continue - still forward to physical node
	}

This provides better debugging information while maintaining the robust error handling approach.

[github-actions]

Great test case! Consider making the assertion more explicit about what constitutes valid vs invalid results:

Suggested change

	const result = service.decodeServiceEnvelope(new Uint8Array([0xFF, 0xFF, 0xFF]));
	// Should return null for invalid data that cannot be decoded as ServiceEnvelope
	expect(result).toBeNull();

This makes the test intent clearer and ensures we're specifically testing the invalid data path.

[github-actions]

These tests are well-designed for documenting the expected behavior! Consider adding a test that verifies the actual flow integration:

Suggested change

	describe('Virtual Node Server - MQTT Proxy Message Handling', () => {
	describe('Virtual Node Server - MQTT Proxy Message Handling', () => {
	// ... existing tests ...
	it('should process MQTT proxy messages through the complete flow', async () => {
	// Test that demonstrates the full: ToRadio → ServiceEnvelope decode → FromRadio → processIncomingData flow
	// This would help catch integration issues between the components
	});
	});

This would verify the end-to-end integration between the VNS and protobuf service.