From 4b565fe58a65f044a32ec23c225d0c4c7bd36467 Mon Sep 17 00:00:00 2001
From: Gui <gui@altermundi.net>
Date: Wed, 19 Jan 2022 19:46:30 +0100
Subject: [PATCH] p2p: always advertise self, to enable mutual address
 discovery (#7620)

Fixes #7593
---
 CHANGELOG_PENDING.md             |  1 +
 internal/p2p/peermanager.go      | 11 +++++++++++
 internal/p2p/peermanager_test.go | 18 ++++++++++++++++++
 node/setup.go                    |  6 ++++++
 4 files changed, 36 insertions(+)

diff --git a/CHANGELOG_PENDING.md b/CHANGELOG_PENDING.md
index 88a36d2c5..7349128be 100644
--- a/CHANGELOG_PENDING.md
+++ b/CHANGELOG_PENDING.md
@@ -19,6 +19,7 @@ Special thanks to external contributors on this release:
 - P2P Protocol
 
   - [p2p] [\#7265](https://github.com/tendermint/tendermint/pull/7265) Peer manager reduces peer score for each failed dial attempts for peers that have not successfully dialed. (@tychoish)
+  - [p2p] [\#7594](https://github.com/tendermint/tendermint/pull/7594) always advertise self, to enable mutual address discovery. (@altergui)
 
 - Go API
 
diff --git a/internal/p2p/peermanager.go b/internal/p2p/peermanager.go
index 397b16941..99ea85692 100644
--- a/internal/p2p/peermanager.go
+++ b/internal/p2p/peermanager.go
@@ -154,6 +154,10 @@ type PeerManagerOptions struct {
 	// consider private and never gossip.
 	PrivatePeers map[types.NodeID]struct{}
 
+	// SelfAddress is the address that will be advertised to peers for them to dial back to us.
+	// If Hostname and Port are unset, Advertise() will include no self-announcement
+	SelfAddress NodeAddress
+
 	// persistentPeers provides fast PersistentPeers lookups. It is built
 	// by optimize().
 	persistentPeers map[types.NodeID]bool
@@ -814,6 +818,13 @@ func (m *PeerManager) Advertise(peerID types.NodeID, limit uint16) []NodeAddress
 	defer m.mtx.Unlock()
 
 	addresses := make([]NodeAddress, 0, limit)
+
+	// advertise ourselves, to let everyone know how to dial us back
+	// and enable mutual address discovery
+	if m.options.SelfAddress.Hostname != "" && m.options.SelfAddress.Port != 0 {
+		addresses = append(addresses, m.options.SelfAddress)
+	}
+
 	for _, peer := range m.store.Ranked() {
 		if peer.ID == peerID {
 			continue
diff --git a/internal/p2p/peermanager_test.go b/internal/p2p/peermanager_test.go
index 69c798d2d..f1dda6543 100644
--- a/internal/p2p/peermanager_test.go
+++ b/internal/p2p/peermanager_test.go
@@ -1760,6 +1760,24 @@ func TestPeerManager_Advertise(t *testing.T) {
 	}, peerManager.Advertise(dID, 2))
 }
 
+func TestPeerManager_Advertise_Self(t *testing.T) {
+	dID := types.NodeID(strings.Repeat("d", 40))
+
+	self := p2p.NodeAddress{Protocol: "tcp", NodeID: selfID, Hostname: "2001:db8::1", Port: 26657}
+
+	// Create a peer manager with SelfAddress defined.
+	peerManager, err := p2p.NewPeerManager(selfID, dbm.NewMemDB(), p2p.PeerManagerOptions{
+		SelfAddress: self,
+	})
+	require.NoError(t, err)
+	defer peerManager.Close()
+
+	// peer manager should always advertise its SelfAddress.
+	require.ElementsMatch(t, []p2p.NodeAddress{
+		self,
+	}, peerManager.Advertise(dID, 100))
+}
+
 func TestPeerManager_SetHeight_GetHeight(t *testing.T) {
 	a := p2p.NodeAddress{Protocol: "memory", NodeID: types.NodeID(strings.Repeat("a", 40))}
 	b := p2p.NodeAddress{Protocol: "memory", NodeID: types.NodeID(strings.Repeat("b", 40))}
diff --git a/node/setup.go b/node/setup.go
index f1ee533ac..e36fe6522 100644
--- a/node/setup.go
+++ b/node/setup.go
@@ -423,6 +423,11 @@ func createPeerManager(
 	nodeID types.NodeID,
 ) (*p2p.PeerManager, error) {
 
+	selfAddr, err := p2p.ParseNodeAddress(nodeID.AddressString(cfg.P2P.ExternalAddress))
+	if err != nil {
+		return nil, fmt.Errorf("couldn't parse ExternalAddress %q: %w", cfg.P2P.ExternalAddress, err)
+	}
+
 	var maxConns uint16
 
 	switch {
@@ -452,6 +457,7 @@ func createPeerManager(
 	}
 
 	options := p2p.PeerManagerOptions{
+		SelfAddress:            selfAddr,
 		MaxConnected:           maxConns,
 		MaxConnectedUpgrade:    4,
 		MaxPeers:               1000,