From ccb80ac79b5ef74dd710f3b5f2e546555154cfa2 Mon Sep 17 00:00:00 2001
From: Arnaud <arnaud@status.im>
Date: Fri, 5 Jun 2026 17:41:24 +0400
Subject: [PATCH] Announce the mapped external UDP port instead of the
 discovery port

---
 storage/nat.nim           |  8 +++++++-
 storage/storage.nim       |  5 ++---
 tests/storage/testnat.nim | 25 +++++++++++++++++++++++--
 3 files changed, 32 insertions(+), 6 deletions(-)

diff --git a/storage/nat.nim b/storage/nat.nim
index 4a709ab6..e9769011 100644
--- a/storage/nat.nim
+++ b/storage/nat.nim
@@ -140,7 +140,10 @@ proc announcePeerInfoAddrs*(discovery: Discovery, peerInfo: PeerInfo, udpPort: P
   discovery.updateRecordsAndSpr(addrs, udpPort = udpPort)
 
 proc setupPeerInfoObserver*(
-    switch: Switch, autonat: AutonatV2Service, discovery: Discovery, udpPort: Port
+    switch: Switch,
+    autonat: AutonatV2Service,
+    discovery: Discovery,
+    natMapper: NatPortMapper,
 ): PeerInfoObserver =
   ## AutoNAT's address mapper resolves peerInfo.addrs into public addresses
   ## once the node is Reachable; peerInfo.update() then notifies observers.
@@ -150,6 +153,9 @@ proc setupPeerInfoObserver*(
       addrs = peerInfo.addrs, reachability = autonat.networkReachability
     if autonat.networkReachability != NetworkReachability.Reachable:
       return
+    # When a NAT mapping is active, announce its external UDP port: the router
+    # may have assigned a different port than the requested discoveryPort.
+    let udpPort = natMapper.activeUdpPort.get(natMapper.discoveryPort)
     announcePeerInfoAddrs(discovery, peerInfo, udpPort)
 
   switch.peerInfo.addObserver(observer)
diff --git a/storage/storage.nim b/storage/storage.nim
index 79b098da..18a5270f 100644
--- a/storage/storage.nim
+++ b/storage/storage.nim
@@ -490,9 +490,8 @@ proc new*(
     if natRouter.isSome:
       natRouter.get.natMapper = natMapper
 
-    peerInfoObserver = some(
-      setupPeerInfoObserver(switch, autonatService.get, discovery, config.discoveryPort)
-    )
+    peerInfoObserver =
+      some(setupPeerInfoObserver(switch, autonatService.get, discovery, natMapper.get))
 
     autonatService.get.setStatusAndConfidenceHandler(
       proc(
diff --git a/tests/storage/testnat.nim b/tests/storage/testnat.nim
index a64fa0f3..8dd87b1e 100644
--- a/tests/storage/testnat.nim
+++ b/tests/storage/testnat.nim
@@ -135,7 +135,9 @@ asyncchecksuite "NAT - handleNatStatus":
 
   test "peerInfo observer announces addresses when Reachable":
     let autonat = AutonatV2Service.new(Rng.instance())
-    discard setupPeerInfoObserver(sw, autonat, disc, discoveryPort)
+    discard setupPeerInfoObserver(
+      sw, autonat, disc, NatPortMapper(discoveryPort: discoveryPort)
+    )
     autonat.networkReachability = Reachable
 
     sw.peerInfo.listenAddrs.add(
@@ -145,9 +147,28 @@ asyncchecksuite "NAT - handleNatStatus":
 
     check disc.announceAddrs == sw.peerInfo.addrs
 
+  test "peerInfo observer announces the mapped external UDP port when a mapping is active":
+    let autonat = AutonatV2Service.new(Rng.instance())
+    let mapper =
+      NatPortMapper(discoveryPort: discoveryPort, activeUdpPort: some(Port(40001)))
+    discard setupPeerInfoObserver(sw, autonat, disc, mapper)
+    autonat.networkReachability = Reachable
+
+    sw.peerInfo.listenAddrs.add(
+      MultiAddress.init("/ip4/1.2.3.4/tcp/9999").expect("valid")
+    )
+    await sw.peerInfo.update()
+
+    let sprAddrs = disc.getSpr().data.addresses.mapIt(it.address)
+    check MultiAddress.init("/ip4/1.2.3.4/udp/40001").expect("valid") in sprAddrs
+    check MultiAddress.init("/ip4/1.2.3.4/udp/" & $discoveryPort).expect("valid") notin
+      sprAddrs
+
   test "peerInfo observer does not announce when the node is not Reachable":
     let autonat = AutonatV2Service.new(Rng.instance())
-    discard setupPeerInfoObserver(sw, autonat, disc, discoveryPort)
+    discard setupPeerInfoObserver(
+      sw, autonat, disc, NatPortMapper(discoveryPort: discoveryPort)
+    )
     autonat.networkReachability = NotReachable
 
     sw.peerInfo.listenAddrs.add(