Merge pull request #6798 from Roasbeef/backend-must-taproot

chainreg: shutdown if backend node doesn't support taproot

Author: Roasbeef

chainreg/chainregistry.go

@@ -496,6 +496,14 @@ func NewPartialChainControl(cfg *Config) (*PartialChainControl, func(), error) {
 			return nil, nil, err
 		}
 
+		// Before we continue any further, we'll ensure that the
+		// backend understands Taproot. If not, then all the default
+		// features can't be used.
+		if !backendSupportsTaproot(chainConn) {
+			return nil, nil, fmt.Errorf("node backend does not " +
+				"support taproot")
+		}
+
 		// The api we will use for our health check depends on the
 		// bitcoind version.
 		cmd, ver, err := getBitcoindHealthCheckCmd(chainConn)
@@ -675,6 +683,21 @@ func NewPartialChainControl(cfg *Config) (*PartialChainControl, func(), error) {
 			return nil, nil, err
 		}
 
+		// Before we continue any further, we'll ensure that the
+		// backend understands Taproot. If not, then all the default
+		// features can't be used.
+		restConfCopy := *rpcConfig
+		restConfCopy.Endpoint = ""
+		restConfCopy.HTTPPostMode = true
+		chainConn, err := rpcclient.New(&restConfCopy, nil)
+		if err != nil {
+			return nil, nil, err
+		}
+		if !backendSupportsTaproot(chainConn) {
+			return nil, nil, fmt.Errorf("node backend does not " +
+				"support taproot")
+		}
+
 		cc.ChainSource = chainRPC
 
 		// Use a query for our best block as a health check.

chainreg/taproot_check.go

@@ -0,0 +1,53 @@
+package chainreg
+
+import (
+	"encoding/json"
+
+	"github.com/btcsuite/btcd/rpcclient"
+)
+
+// backendSupportsTaproot returns true if the backend understands the taproot
+// soft fork.
+func backendSupportsTaproot(rpc *rpcclient.Client) bool {
+	// First, we'll try to access the normal getblockchaininfo call.
+	chainInfo, err := rpc.GetBlockChainInfo()
+	if err == nil {
+		// If this call worked, then we'll check that the taproot
+		// deployment is defined.
+		if chainInfo.SoftForks != nil {
+			_, ok := chainInfo.SoftForks.Bip9SoftForks["taproot"]
+			if ok {
+				return ok
+			}
+		}
+	}
+
+	// The user might be running a newer version of bitcoind that doesn't
+	// implement the getblockchaininfo call any longer, so we'll fall back
+	// here.
+	//
+	// Alternatively, the fork wasn't specified, but the user might be
+	// running a newer version of bitcoind that still has the
+	// getblockchaininfo call, but doesn't populate the data, so we'll hit
+	// the new getdeploymentinfo call.
+	resp, err := rpc.RawRequest("getdeploymentinfo", nil)
+	if err != nil {
+		log.Warnf("unable to make getdeploymentinfo request: %v", err)
+		return false
+	}
+
+	info := struct {
+		Deployments map[string]struct {
+			Type   string `json:"type"`
+			Active bool   `json:"active"`
+			Height int32  `json:"height"`
+		} `json:"deployments"`
+	}{}
+	if err := json.Unmarshal(resp, &info); err != nil {
+		log.Warnf("unable to decode getdeploymentinfo resp: %v", err)
+		return false
+	}
+
+	_, ok := info.Deployments["taproot"]
+	return ok
+}

docs/release-notes/release-notes-0.15.1.md

@@ -11,6 +11,12 @@
   binary digest to be different whether that folder exists or
   not](https://github.com/lightningnetwork/lnd/pull/6676).
 
+## Taproot
+
+[`lnd` will now refuse to start if it detects the full node backned does not
+support Tapoot](https://github.com/lightningnetwork/lnd/pull/6798).
+
+
 ## `lncli`
 
 * [Add `payment_addr` flag to