Gossipsub: test extension

pubsub/gossipsub/extensions/experimental/test-extension.md

@@ -0,0 +1,37 @@
+# Test Extension
+
+| Lifecycle Stage | Maturity      | Status | Latest Revision |
+| --------------- | ------------- | ------ | --------------- |
+| 1A              | Working Draft | Active | r0, 2025-06-23  |
+
+Authors: [@marcopolo]
+
+Interest Group: @jxs
+
+[@marcopolo]: https://github.com/marcopolo
+[@jxs]: https://github.com/jxs
+
+See the [lifecycle document][lifecycle-spec] for context about the maturity level
+and spec status.
+
+[lifecycle-spec]: https://github.com/libp2p/specs/blob/master/00-framework-01-spec-lifecycle.md
+
+## Overview
+
+This introduces a minimal extension to Gossipsub. The only motivation is to
+test the interoperability of Gossipsub Extensions Control Message across
+implementations. One way for example, is to connect different implementations
+together and assert that both peers send the TestExtension message.
+
+## The Protocol
+
+If both Peers support the Test Extension, each peer MUST send a TestExtension
+Message.
+
+## Protobuf
+
+```protobuf
+syntax = "proto2";
+
+message TestExtension {}
+```

pubsub/gossipsub/gossipsub-v1.3.md

@@ -111,6 +111,8 @@ message ControlExtensions {
 
   // Experimental extensions must use field numbers larger than 0x200000 to be
   // encoded with at least 4 bytes
+
+  optional bool testExtension = 6492434;
 }
 
 message ControlMessage {
@@ -133,5 +135,6 @@ message RPC {
 	// Experimental Extensions should register their messages here. They
 	// must use field numbers larger than 0x200000 to be encoded with at least 4
 	// bytes
+	optional TestExtension testExtension = 6492434;
 }
 ```