From 25b540fec4a22b44cdb9648ab3587a675e5853fd Mon Sep 17 00:00:00 2001
From: Valentine Wallace <valentine.m.wallace@gmail.com>
Date: Fri, 24 May 2019 18:16:33 -0700
Subject: [PATCH] chainregistry+config: add neutrino flag to assert filter
 header chain

---
 chainregistry.go | 38 ++++++++++++++++++++++++++++++++++++++
 config.go        | 13 +++++++------
 2 files changed, 45 insertions(+), 6 deletions(-)

diff --git a/chainregistry.go b/chainregistry.go
index e7b6b841..4962ee02 100644
--- a/chainregistry.go
+++ b/chainregistry.go
@@ -19,6 +19,7 @@ import (
 	"github.com/btcsuite/btcwallet/wallet"
 	"github.com/btcsuite/btcwallet/walletdb"
 	"github.com/lightninglabs/neutrino"
+	"github.com/lightninglabs/neutrino/headerfs"
 	"github.com/lightningnetwork/lnd/chainntnfs"
 	"github.com/lightningnetwork/lnd/chainntnfs/bitcoindnotify"
 	"github.com/lightningnetwork/lnd/chainntnfs/btcdnotify"
@@ -705,6 +706,13 @@ func initNeutrinoBackend(chainDir string) (*neutrino.ChainService, func(), error
 			"database: %v", err)
 	}
 
+	headerStateAssertion, err := parseHeaderStateAssertion(
+		cfg.NeutrinoMode.AssertFilterHeader,
+	)
+	if err != nil {
+		return nil, nil, err
+	}
+
 	// With the database open, we can now create an instance of the
 	// neutrino light client. We pass in relevant configuration parameters
 	// required.
@@ -735,6 +743,7 @@ func initNeutrinoBackend(chainDir string) (*neutrino.ChainService, func(), error
 
 			return ips, nil
 		},
+		AssertFilterHeader: headerStateAssertion,
 	}
 
 	neutrino.MaxPeers = 8
@@ -758,3 +767,32 @@ func initNeutrinoBackend(chainDir string) (*neutrino.ChainService, func(), error
 
 	return neutrinoCS, cleanUp, nil
 }
+
+// parseHeaderStateAssertion parses the user-specified neutrino header state
+// into a headerfs.FilterHeader.
+func parseHeaderStateAssertion(state string) (*headerfs.FilterHeader, error) {
+	if len(state) == 0 {
+		return nil, nil
+	}
+
+	split := strings.Split(state, ":")
+	if len(split) != 2 {
+		return nil, fmt.Errorf("header state assertion %v in "+
+			"unexpected format, expected format height:hash", state)
+	}
+
+	height, err := strconv.ParseUint(split[0], 10, 32)
+	if err != nil {
+		return nil, fmt.Errorf("invalid filter header height: %v", err)
+	}
+
+	hash, err := chainhash.NewHashFromStr(split[1])
+	if err != nil {
+		return nil, fmt.Errorf("invalid filter header hash: %v", err)
+	}
+
+	return &headerfs.FilterHeader{
+		Height:     uint32(height),
+		FilterHash: *hash,
+	}, nil
+}
diff --git a/config.go b/config.go
index c6e4c875..09077620 100644
--- a/config.go
+++ b/config.go
@@ -169,12 +169,13 @@ type chainConfig struct {
 }
 
 type neutrinoConfig struct {
-	AddPeers     []string      `short:"a" long:"addpeer" description:"Add a peer to connect with at startup"`
-	ConnectPeers []string      `long:"connect" description:"Connect only to the specified peers at startup"`
-	MaxPeers     int           `long:"maxpeers" description:"Max number of inbound and outbound peers"`
-	BanDuration  time.Duration `long:"banduration" description:"How long to ban misbehaving peers.  Valid time units are {s, m, h}.  Minimum 1 second"`
-	BanThreshold uint32        `long:"banthreshold" description:"Maximum allowed ban score before disconnecting and banning misbehaving peers."`
-	FeeURL       string        `long:"feeurl" description:"Optional URL for fee estimation. If a URL is not specified, static fees will be used for estimation."`
+	AddPeers           []string      `short:"a" long:"addpeer" description:"Add a peer to connect with at startup"`
+	ConnectPeers       []string      `long:"connect" description:"Connect only to the specified peers at startup"`
+	MaxPeers           int           `long:"maxpeers" description:"Max number of inbound and outbound peers"`
+	BanDuration        time.Duration `long:"banduration" description:"How long to ban misbehaving peers.  Valid time units are {s, m, h}.  Minimum 1 second"`
+	BanThreshold       uint32        `long:"banthreshold" description:"Maximum allowed ban score before disconnecting and banning misbehaving peers."`
+	FeeURL             string        `long:"feeurl" description:"Optional URL for fee estimation. If a URL is not specified, static fees will be used for estimation."`
+	AssertFilterHeader string        `long:"assertfilterheader" description:"Optional filter header in height:hash format to assert the state of neutrino's filter header chain on startup. If the assertion does not hold, then the filter header chain will be re-synced from the genesis block."`
 }
 
 type btcdConfig struct {