From 0c6b2d54bf97e3af648176796afc172fe22c298f Mon Sep 17 00:00:00 2001
From: ian <ianopolous@protonmail.com>
Date: Mon, 20 May 2024 21:15:15 +0100
Subject: [PATCH] Fix mdns when listening with ipv6 wildcard (which includes
 ipv4)

---
 .../io/libp2p/discovery/MDnsDiscovery.kt      |  6 +++++-
 .../io/libp2p/discovery/MDnsDiscoveryTest.kt  | 21 +++++++++++++++++++
 2 files changed, 26 insertions(+), 1 deletion(-)

diff --git a/libp2p/src/main/kotlin/io/libp2p/discovery/MDnsDiscovery.kt b/libp2p/src/main/kotlin/io/libp2p/discovery/MDnsDiscovery.kt
index 658103db3..e2afcaf61 100644
--- a/libp2p/src/main/kotlin/io/libp2p/discovery/MDnsDiscovery.kt
+++ b/libp2p/src/main/kotlin/io/libp2p/discovery/MDnsDiscovery.kt
@@ -76,7 +76,11 @@ class MDnsDiscovery(
         val address = host.listenAddresses().find {
             it.has(Protocol.IP4)
         }
-        val str = address?.getFirstComponent(Protocol.TCP)?.stringValue!!
+        val ipv6OnlyAddress = if (address == null)
+            host.listenAddresses().find {
+                it.has(Protocol.IP6)
+            } else address
+        val str = ipv6OnlyAddress?.getFirstComponent(Protocol.TCP)?.stringValue!!
         return Integer.parseInt(str)
     }
 
diff --git a/libp2p/src/test/kotlin/io/libp2p/discovery/MDnsDiscoveryTest.kt b/libp2p/src/test/kotlin/io/libp2p/discovery/MDnsDiscoveryTest.kt
index b0cfa93c6..f0acd5790 100644
--- a/libp2p/src/test/kotlin/io/libp2p/discovery/MDnsDiscoveryTest.kt
+++ b/libp2p/src/test/kotlin/io/libp2p/discovery/MDnsDiscoveryTest.kt
@@ -24,6 +24,18 @@ class MDnsDiscoveryTest {
         }
     }
 
+    val hostIpv6 = object : NullHost() {
+        override val peerId: PeerId = PeerId.fromPubKey(
+            generateEcdsaKeyPair().second
+        )
+
+        override fun listenAddresses(): List<Multiaddr> {
+            return listOf(
+                Multiaddr("/ip6/::/tcp/4001")
+            )
+        }
+    }
+
     val otherHost = object : NullHost() {
         override val peerId: PeerId = PeerId.fromPubKey(
             generateEcdsaKeyPair().second
@@ -47,6 +59,15 @@ class MDnsDiscoveryTest {
         discoverer.stop().get(1, TimeUnit.SECONDS)
     }
 
+    @Test
+    fun `start and stop discovery ipv6`() {
+        val discoverer = MDnsDiscovery(hostIpv6, testServiceTag)
+
+        discoverer.start().get(1, TimeUnit.SECONDS)
+        TimeUnit.MILLISECONDS.sleep(100)
+        discoverer.stop().get(1, TimeUnit.SECONDS)
+    }
+
     @Test
     fun `start discovery and listen for self`() {
         var peerInfo: PeerInfo? = null