From df9f1485a7de068e60d3c93241a7ae962d6e0fb8 Mon Sep 17 00:00:00 2001
From: Mohamed Awnallah <mohamedmohey2352@gmail.com>
Date: Sun, 31 Mar 2024 07:31:20 +0200
Subject: [PATCH 1/2] chainreg: add `checkOutboundPeers` function

In this commit we add `checkOutboundPeers` function
to the `cc.HealthCheck` function.
---
 chainreg/chainregistry.go | 65 +++++++++++++++++++++++++++++++++++++--
 1 file changed, 63 insertions(+), 2 deletions(-)

diff --git a/chainreg/chainregistry.go b/chainreg/chainregistry.go
index 02da263912..c3d4286117 100644
--- a/chainreg/chainregistry.go
+++ b/chainreg/chainregistry.go
@@ -122,6 +122,11 @@ const (
 	// DefaultBitcoinStaticMinRelayFeeRate is the min relay fee used for
 	// static estimators.
 	DefaultBitcoinStaticMinRelayFeeRate = chainfee.FeePerKwFloor
+
+	// DefaultMinOutboundPeers is the min number of connected
+	// outbound peers the chain backend should have to maintain a
+	// healthy connection to the network.
+	DefaultMinOutboundPeers = 6
 )
 
 // PartialChainControl contains all the primary interfaces of the chain control
@@ -504,7 +509,21 @@ func NewPartialChainControl(cfg *Config) (*PartialChainControl, func(), error) {
 
 		cc.HealthCheck = func() error {
 			_, err := chainConn.RawRequest(cmd, nil)
-			return err
+			if err != nil {
+				return err
+			}
+
+			// On local test networks we usually don't have multiple
+			// chain backend peers, so we can skip
+			// the checkOutboundPeers test.
+			if cfg.Bitcoin.SimNet || cfg.Bitcoin.RegTest {
+				return nil
+			}
+
+			// Make sure the bitcoind chain backend maintains a
+			// healthy connection to the network by checking the
+			// number of outbound peers.
+			return checkOutboundPeers(chainConn)
 		}
 
 	case "btcd":
@@ -613,7 +632,21 @@ func NewPartialChainControl(cfg *Config) (*PartialChainControl, func(), error) {
 		// Use a query for our best block as a health check.
 		cc.HealthCheck = func() error {
 			_, _, err := cc.ChainSource.GetBestBlock()
-			return err
+			if err != nil {
+				return err
+			}
+
+			// On local test networks we usually don't have multiple
+			// chain backend peers, so we can skip
+			// the checkOutboundPeers test.
+			if cfg.Bitcoin.SimNet || cfg.Bitcoin.RegTest {
+				return nil
+			}
+
+			// Make sure the btcd chain backend maintains a
+			// healthy connection to the network by checking the
+			// number of outbound peers.
+			return checkOutboundPeers(chainRPC.Client)
 		}
 
 		// If we're not in simnet or regtest mode, then we'll attempt
@@ -840,3 +873,31 @@ var (
 		},
 	}
 )
+
+// checkOutboundPeers checks the number of outbound peers connected to the
+// provided RPC client. If the number of outbound peers is below 6, a warning
+// is logged. This function is intended to ensure that the chain backend
+// maintains a healthy connection to the network.
+func checkOutboundPeers(client *rpcclient.Client) error {
+	peers, err := client.GetPeerInfo()
+	if err != nil {
+		return err
+	}
+
+	var outboundPeers int
+	for _, peer := range peers {
+		if !peer.Inbound {
+			outboundPeers++
+		}
+	}
+
+	if outboundPeers < DefaultMinOutboundPeers {
+		log.Warnf("The chain backend has an insufficient number "+
+			"of connected outbound peers (%d connected, expected "+
+			"minimum is %d) which can be a security issue. "+
+			"Connect to more trusted nodes manually if necessary.",
+			outboundPeers, DefaultMinOutboundPeers)
+	}
+
+	return nil
+}

From 130fdbde73c4943723b04c9b9f0adce8ba62cf02 Mon Sep 17 00:00:00 2001
From: Mohamed Awnallah <mohamedmohey2352@gmail.com>
Date: Tue, 2 Apr 2024 15:02:02 +0200
Subject: [PATCH 2/2] docs: update the release-notes-0.18.0.md

---
 docs/release-notes/release-notes-0.18.0.md | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/docs/release-notes/release-notes-0.18.0.md b/docs/release-notes/release-notes-0.18.0.md
index f554cd3e80..13685ec935 100644
--- a/docs/release-notes/release-notes-0.18.0.md
+++ b/docs/release-notes/release-notes-0.18.0.md
@@ -265,6 +265,11 @@ bitcoin peers' feefilter values into account](https://github.com/lightningnetwor
   types](https://github.com/lightningnetwork/lnd/pull/8554) defined in
   `btcd/rpcclient`.
 
+* [checkOutboundPeers](https://github.com/lightningnetwork/lnd/pull/8576) is
+  added to `chainHealthCheck` to make sure chain backend `bitcoind` and `btcd`
+  maintain a healthy connection to the network by checking the number of
+  outbound peers if they are below 6.
+
 ### Logging
 * [Add the htlc amount](https://github.com/lightningnetwork/lnd/pull/8156) to
   contract court logs in case of timed-out HTLCs in order to easily spot dust