Merge pull request #5781 from Crypt-iQ/accurate_dust0922

multi: replace DefaultDustLimit with accurate dust limit

chainreg/chainregistry.go

@@ -174,15 +174,6 @@ const (
 	BtcToLtcConversionRate = 60
 )
 
-// DefaultBtcChannelConstraints is the default set of channel constraints that are
-// meant to be used when initially funding a Bitcoin channel.
-//
-// TODO(halseth): make configurable at startup?
-var DefaultBtcChannelConstraints = channeldb.ChannelConstraints{
-	DustLimit:        lnwallet.DefaultDustLimit(),
-	MaxAcceptedHtlcs: input.MaxHTLCNumber / 2,
-}
-
 // DefaultLtcChannelConstraints is the default set of channel constraints that are
 // meant to be used when initially funding a Litecoin channel.
 var DefaultLtcChannelConstraints = channeldb.ChannelConstraints{
@@ -235,6 +226,19 @@ type ChainControl struct {
 	MinHtlcIn lnwire.MilliSatoshi
 }
 
+// GenDefaultBtcChannelConstraints generates the default set of channel
+// constraints that are to be used when funding a Bitcoin channel.
+func GenDefaultBtcConstraints() channeldb.ChannelConstraints {
+	// We use the dust limit for the maximally sized witness program with
+	// a 40-byte data push.
+	dustLimit := lnwallet.DustLimitForSize(input.UnknownWitnessSize)
+
+	return channeldb.ChannelConstraints{
+		DustLimit:        dustLimit,
+		MaxAcceptedHtlcs: input.MaxHTLCNumber / 2,
+	}
+}
+
 // NewChainControl attempts to create a ChainControl instance according
 // to the parameters in the passed configuration. Currently three
 // branches of ChainControl instances exist: one backed by a running btcd
@@ -674,7 +678,7 @@ func NewChainControl(cfg *Config, blockCache *blockcache.BlockCache) (
 	cc.Wc = wc
 
 	// Select the default channel constraints for the primary chain.
-	channelConstraints := DefaultBtcChannelConstraints
+	channelConstraints := GenDefaultBtcConstraints()
 	if cfg.PrimaryChain() == LitecoinChain {
 		channelConstraints = DefaultLtcChannelConstraints
 	}

docs/release-notes/release-notes-0.13.3.md

@@ -0,0 +1,9 @@
+# Release Notes
+
+## Wallet
+
+* [The `DefaultDustLimit` method has been removed in favor of `DustLimitForSize` which calculates the proper network dust limit for a given output size. This also fixes certain APIs like SendCoins to be able to send 294 sats to a P2WPKH script.](https://github.com/lightningnetwork/lnd/pull/5781)
+
+# Contributors (Alphabetical Order)
+
+* Eugene Siegel

funding/manager.go

@@ -1340,7 +1340,7 @@ func (f *Manager) handleFundingOpen(peer lnpeer.Peer,
 		CsvDelay:         msg.CsvDelay,
 	}
 	err = reservation.CommitConstraints(
-		channelConstraints, f.cfg.MaxLocalCSVDelay,
+		channelConstraints, f.cfg.MaxLocalCSVDelay, true,
 	)
 	if err != nil {
 		log.Errorf("Unacceptable channel constraints: %v", err)
@@ -1386,7 +1386,19 @@ func (f *Manager) handleFundingOpen(peer lnpeer.Peer,
 		remoteCsvDelay = acceptorResp.CSVDelay
 	}
 
-	chanReserve := f.cfg.RequiredRemoteChanReserve(amt, msg.DustLimit)
+	// If our default dust limit was above their ChannelReserve, we change
+	// it to the ChannelReserve. We must make sure the ChannelReserve we
+	// send in the AcceptChannel message is above both dust limits.
+	// Therefore, take the maximum of msg.DustLimit and our dust limit.
+	//
+	// NOTE: Even with this bounding, the ChannelAcceptor may return an
+	// BOLT#02-invalid ChannelReserve.
+	maxDustLimit := reservation.OurContribution().DustLimit
+	if msg.DustLimit > maxDustLimit {
+		maxDustLimit = msg.DustLimit
+	}
+
+	chanReserve := f.cfg.RequiredRemoteChanReserve(amt, maxDustLimit)
 	if acceptorResp.Reserve != 0 {
 		chanReserve = acceptorResp.Reserve
 	}
@@ -1576,7 +1588,7 @@ func (f *Manager) handleFundingAccept(peer lnpeer.Peer,
 		CsvDelay:         msg.CsvDelay,
 	}
 	err = resCtx.reservation.CommitConstraints(
-		channelConstraints, resCtx.maxLocalCsv,
+		channelConstraints, resCtx.maxLocalCsv, false,
 	)
 	if err != nil {
 		log.Warnf("Unacceptable channel constraints: %v", err)
@@ -1586,8 +1598,11 @@ func (f *Manager) handleFundingAccept(peer lnpeer.Peer,
 
 	// As they've accepted our channel constraints, we'll regenerate them
 	// here so we can properly commit their accepted constraints to the
-	// reservation.
+	// reservation. Also make sure that we re-generate the ChannelReserve
-	chanReserve := f.cfg.RequiredRemoteChanReserve(resCtx.chanAmt, msg.DustLimit)
+	// with our dust limit or we can get stuck channels.
+	chanReserve := f.cfg.RequiredRemoteChanReserve(
+		resCtx.chanAmt, resCtx.reservation.OurContribution().DustLimit,
+	)
 
 	// The remote node has responded with their portion of the channel
 	// contribution. At this point, we can process their contribution which
@@ -3114,19 +3129,10 @@ func (f *Manager) handleInitFundingMsg(msg *InitFundingMsg) {
 		maxCSV = f.cfg.MaxLocalCSVDelay
 	}
 
-	// We'll determine our dust limit depending on which chain is active.
-	var ourDustLimit btcutil.Amount
-	switch f.cfg.RegisteredChains.PrimaryChain() {
-	case chainreg.BitcoinChain:
-		ourDustLimit = lnwallet.DefaultDustLimit()
-	case chainreg.LitecoinChain:
-		ourDustLimit = chainreg.DefaultLitecoinDustLimit
-	}
 	log.Infof("Initiating fundingRequest(local_amt=%v "+
 		"(subtract_fees=%v), push_amt=%v, chain_hash=%v, peer=%x, "+
-		"dust_limit=%v, min_confs=%v)", localAmt, msg.SubtractFees,
+		"min_confs=%v)", localAmt, msg.SubtractFees, msg.PushAmt,
-		msg.PushAmt, msg.ChainHash, peerKey.SerializeCompressed(),
+		msg.ChainHash, peerKey.SerializeCompressed(), msg.MinConfs)
-		ourDustLimit, msg.MinConfs)
 
 	// We set the channel flags to indicate whether we want this channel to
 	// be announced to the network.
@@ -3300,6 +3306,12 @@ func (f *Manager) handleInitFundingMsg(msg *InitFundingMsg) {
 	// request to the remote peer, kicking off the funding workflow.
 	ourContribution := reservation.OurContribution()
 
+	// Fetch our dust limit which is part of the default channel
+	// constraints, and log it.
+	ourDustLimit := ourContribution.DustLimit
+
+	log.Infof("Dust limit for pendingID(%x): %v", chanID, ourDustLimit)
+
 	// Finally, we'll use the current value of the channels and our default
 	// policy to determine of required commitment constraints for the
 	// remote party.
@@ -3313,7 +3325,7 @@ func (f *Manager) handleInitFundingMsg(msg *InitFundingMsg) {
 		PendingChannelID:      chanID,
 		FundingAmount:         capacity,
 		PushAmount:            msg.PushAmt,
-		DustLimit:             ourContribution.DustLimit,
+		DustLimit:             ourDustLimit,
 		MaxValueInFlight:      maxValue,
 		ChannelReserve:        chanReserve,
 		HtlcMinimum:           minHtlcIn,

funding/manager_test.go

@@ -276,7 +276,7 @@ func createTestWallet(cdb *channeldb.DB, netParams *chaincfg.Params,
 		ChainIO:            bio,
 		FeeEstimator:       estimator,
 		NetParams:          *netParams,
-		DefaultConstraints: chainreg.DefaultBtcChannelConstraints,
+		DefaultConstraints: chainreg.GenDefaultBtcConstraints(),
 	})
 	if err != nil {
 		return nil, err

go.mod

@@ -5,13 +5,14 @@ require (
 	github.com/NebulousLabs/fastrand v0.0.0-20181203155948-6fb6489aac4e // indirect
 	github.com/NebulousLabs/go-upnp v0.0.0-20180202185039-29b680b06c82
 	github.com/Yawning/aez v0.0.0-20180114000226-4dad034d9db2
-	github.com/btcsuite/btcd v0.22.0-beta.0.20210803133449-f5a1fb9965e4
+	github.com/btcsuite/btcd v0.22.0-beta.0.20210916191717-f8e6854197cd
 	github.com/btcsuite/btclog v0.0.0-20170628155309-84c8d2346e9f
 	github.com/btcsuite/btcutil v1.0.3-0.20210527170813-e2ba6805a890
 	github.com/btcsuite/btcutil/psbt v1.0.3-0.20210527170813-e2ba6805a890
 	github.com/btcsuite/btcwallet v0.12.1-0.20210826004415-4ef582f76b02
-	github.com/btcsuite/btcwallet/wallet/txauthor v1.0.2-0.20210803004036-eebed51155ec
+	github.com/btcsuite/btcwallet/wallet/txauthor v1.1.0
-	github.com/btcsuite/btcwallet/wallet/txrules v1.0.0
+	github.com/btcsuite/btcwallet/wallet/txrules v1.1.0
+	github.com/btcsuite/btcwallet/wallet/txsizes v1.1.0 // indirect
 	github.com/btcsuite/btcwallet/walletdb v1.3.6-0.20210803004036-eebed51155ec
 	github.com/btcsuite/btcwallet/wtxmgr v1.3.1-0.20210822222949-9b5a201c344c
 	github.com/coreos/go-systemd v0.0.0-20190719114852-fd7a80b32e1f
@@ -37,7 +38,7 @@ require (
 	github.com/juju/testing v0.0.0-20190723135506-ce30eb24acd2 // indirect
 	github.com/juju/utils v0.0.0-20180820210520-bf9cc5bdd62d // indirect
 	github.com/juju/version v0.0.0-20180108022336-b64dbd566305 // indirect
-	github.com/kkdai/bstream v0.0.0-20181106074824-b3251f7901ec
+	github.com/kkdai/bstream v1.0.0
 	github.com/lightninglabs/neutrino v0.12.1
 	github.com/lightninglabs/protobuf-hex-display v1.4.3-hex-display
 	github.com/lightningnetwork/lightning-onion v1.0.2-0.20210520211913-522b799e65b1
@@ -56,7 +57,7 @@ require (
 	github.com/urfave/cli v1.20.0
 	go.etcd.io/etcd/client/pkg/v3 v3.5.0
 	go.etcd.io/etcd/client/v3 v3.5.0
-	golang.org/x/crypto v0.0.0-20210711020723-a769d52b0f97
+	golang.org/x/crypto v0.0.0-20210921155107-089bfa567519
 	golang.org/x/net v0.0.0-20210913180222-943fd674d43e
 	golang.org/x/sync v0.0.0-20210220032951-036812b2e83c
 	golang.org/x/sys v0.0.0-20210915083310-ed5796bab164 // indirect

go.sum

@@ -76,8 +76,9 @@ github.com/btcsuite/btcd v0.0.0-20190629003639-c26ffa870fd8/go.mod h1:3J08xEfcug
 github.com/btcsuite/btcd v0.0.0-20190824003749-130ea5bddde3/go.mod h1:3J08xEfcugPacsc34/LKRU2yO7YmuT8yt28J8k2+rrI=
 github.com/btcsuite/btcd v0.20.1-beta/go.mod h1:wVuoA8VJLEcwgqHBwHmzLRazpKxTv13Px/pDuV7OomQ=
 github.com/btcsuite/btcd v0.21.0-beta.0.20201208033208-6bd4c64a54fa/go.mod h1:Sv4JPQ3/M+teHz9Bo5jBpkNcP0x6r7rdihlNL/7tTAs=
-github.com/btcsuite/btcd v0.22.0-beta.0.20210803133449-f5a1fb9965e4 h1:EmyLrldY44jDVa3dQ2iscj1S6ExuVJhRzCZBOXo93r0=
 github.com/btcsuite/btcd v0.22.0-beta.0.20210803133449-f5a1fb9965e4/go.mod h1:9n5ntfhhHQBIhUvlhDvD3Qg6fRUj4jkN0VB8L8svzOA=
+github.com/btcsuite/btcd v0.22.0-beta.0.20210916191717-f8e6854197cd h1:Nq1fLF6IA8XfW0HTpLaVZoDKazt05J1C2AAeswYloBE=
+github.com/btcsuite/btcd v0.22.0-beta.0.20210916191717-f8e6854197cd/go.mod h1:9n5ntfhhHQBIhUvlhDvD3Qg6fRUj4jkN0VB8L8svzOA=
 github.com/btcsuite/btclog v0.0.0-20170628155309-84c8d2346e9f h1:bAs4lUbRJpnnkd9VhRV3jjAVU7DJVjMaK+IsvSeZvFo=
 github.com/btcsuite/btclog v0.0.0-20170628155309-84c8d2346e9f/go.mod h1:TdznJufoqS23FtqVCzL0ZqgP5MqXbb4fg/WgDys70nA=
 github.com/btcsuite/btcutil v0.0.0-20190425235716-9e5f4b9a998d/go.mod h1:+5NJ2+qvTyV9exUAL/rxXi3DcLg2Ts+ymUAY5y4NvMg=
@@ -92,13 +93,15 @@ github.com/btcsuite/btcwallet v0.12.1-0.20210826004415-4ef582f76b02 h1:Q8Scm1SXN
 github.com/btcsuite/btcwallet v0.12.1-0.20210826004415-4ef582f76b02/go.mod h1:SdqXKJoEEi5LJq6zU67PcKiyqF97AcUOfBfyQHC7rqQ=
 github.com/btcsuite/btcwallet/wallet/txauthor v1.0.0/go.mod h1:VufDts7bd/zs3GV13f/lXc/0lXrPnvxD/NvmpG/FEKU=
 github.com/btcsuite/btcwallet/wallet/txauthor v1.0.1-0.20210329233242-e0607006dce6/go.mod h1:VufDts7bd/zs3GV13f/lXc/0lXrPnvxD/NvmpG/FEKU=
-github.com/btcsuite/btcwallet/wallet/txauthor v1.0.2-0.20210803004036-eebed51155ec h1:nuO8goa4gbgDM4iegCztF7mTq8io9NT1DAMoPrEI6S4=
+github.com/btcsuite/btcwallet/wallet/txauthor v1.1.0 h1:8pO0pvPX1rFRfRiol4oV6kX7dY5y4chPwhfVwUfvwtk=
-github.com/btcsuite/btcwallet/wallet/txauthor v1.0.2-0.20210803004036-eebed51155ec/go.mod h1:VufDts7bd/zs3GV13f/lXc/0lXrPnvxD/NvmpG/FEKU=
+github.com/btcsuite/btcwallet/wallet/txauthor v1.1.0/go.mod h1:ktYuJyumYtwG+QQ832Q+kqvxWJRAei3Nqs5qhSn4nww=
-github.com/btcsuite/btcwallet/wallet/txrules v1.0.0 h1:2VsfS0sBedcM5KmDzRMT3+b6xobqWveZGvjb+jFez5w=
 github.com/btcsuite/btcwallet/wallet/txrules v1.0.0/go.mod h1:UwQE78yCerZ313EXZwEiu3jNAtfXj2n2+c8RWiE/WNA=
+github.com/btcsuite/btcwallet/wallet/txrules v1.1.0 h1:Vg8G8zhNVjaCdwJg2QOmLoWn4RTP7K0J9xlwY8CJnLY=
+github.com/btcsuite/btcwallet/wallet/txrules v1.1.0/go.mod h1:Zn9UTqpiTH+HOd5BLzSBzULzlOPmcoeyQIA0cp0WbQQ=
 github.com/btcsuite/btcwallet/wallet/txsizes v1.0.0/go.mod h1:pauEU8UuMFiThe5PB3EO+gO5kx87Me5NvdQDsTuq6cs=
-github.com/btcsuite/btcwallet/wallet/txsizes v1.0.1-0.20210519225359-6ab9b615576f h1:bzrmHuQ3ZGWWhGDyTL0OqihQWXGXSXNuBPkDoDB8SS4=
 github.com/btcsuite/btcwallet/wallet/txsizes v1.0.1-0.20210519225359-6ab9b615576f/go.mod h1:pauEU8UuMFiThe5PB3EO+gO5kx87Me5NvdQDsTuq6cs=
+github.com/btcsuite/btcwallet/wallet/txsizes v1.1.0 h1:wZnOolEAeNOHzHTnznw/wQv+j35ftCIokNrnOTOU5o8=
+github.com/btcsuite/btcwallet/wallet/txsizes v1.1.0/go.mod h1:pauEU8UuMFiThe5PB3EO+gO5kx87Me5NvdQDsTuq6cs=
 github.com/btcsuite/btcwallet/walletdb v1.3.4/go.mod h1:oJDxAEUHVtnmIIBaa22wSBPTVcs6hUp5NKWmI8xDwwU=
 github.com/btcsuite/btcwallet/walletdb v1.3.5/go.mod h1:oJDxAEUHVtnmIIBaa22wSBPTVcs6hUp5NKWmI8xDwwU=
 github.com/btcsuite/btcwallet/walletdb v1.3.6-0.20210803004036-eebed51155ec h1:zcAU3Ij8SmqaE+ITtS76fua2Niq7DRNp46sJRhi8PiI=
@@ -408,8 +411,9 @@ github.com/kisielk/errcheck v1.2.0/go.mod h1:/BMXB+zMLi60iA8Vv6Ksmxu/1UDYcXs4uQL
 github.com/kisielk/errcheck v1.5.0/go.mod h1:pFxgyoBC7bSaBwPgfKdkLd5X25qrDl4LWUI2bnpBCr8=
 github.com/kisielk/gotool v1.0.0/go.mod h1:XhKaO+MFFWcvkIS/tQcRk01m1F5IRFswLeQ+oQHNcck=
 github.com/kkdai/bstream v0.0.0-20161212061736-f391b8402d23/go.mod h1:J+Gs4SYgM6CZQHDETBtE9HaSEkGmuNXF86RwHhHUvq4=
-github.com/kkdai/bstream v0.0.0-20181106074824-b3251f7901ec h1:n1NeQ3SgUHyISrjFFoO5dR748Is8dBL9qpaTNfphQrs=
 github.com/kkdai/bstream v0.0.0-20181106074824-b3251f7901ec/go.mod h1:J+Gs4SYgM6CZQHDETBtE9HaSEkGmuNXF86RwHhHUvq4=
+github.com/kkdai/bstream v1.0.0 h1:Se5gHwgp2VT2uHfDrkbbgbgEvV9cimLELwrPJctSjg8=
+github.com/kkdai/bstream v1.0.0/go.mod h1:FDnDOHt5Yx4p3FaHcioFT0QjDOtgUpvjeZqAs+NVZZA=
 github.com/klauspost/compress v1.4.1/go.mod h1:RyIbtBH6LamlWaDj8nUwkbUhJ87Yi3uG0guNDohfE1A=
 github.com/klauspost/compress v1.10.10 h1:a/y8CglcM7gLGYmlbP/stPE5sR3hbhFRUjCBfd/0B3I=
 github.com/klauspost/compress v1.10.10/go.mod h1:aoV0uJVorq1K+umq18yTdKaF57EivdYsUV+/s2qKfXs=
@@ -674,8 +678,9 @@ golang.org/x/crypto v0.0.0-20200622213623-75b288015ac9/go.mod h1:LzIPMQfyMNhhGPh
 golang.org/x/crypto v0.0.0-20201002170205-7f63de1d35b0/go.mod h1:LzIPMQfyMNhhGPhUkYOs5KpL4U8rLKemX1yGLhDgUto=
 golang.org/x/crypto v0.0.0-20201203163018-be400aefbc4c/go.mod h1:jdWPYTVW3xRLrWPugEBEK3UY2ZEsg3UU495nc5E+M+I=
 golang.org/x/crypto v0.0.0-20210616213533-5ff15b29337e/go.mod h1:GvvjBRRGRdwPK5ydBHafDWAxML/pGHZbMvKqRZ5+Abc=
-golang.org/x/crypto v0.0.0-20210711020723-a769d52b0f97 h1:/UOmuWzQfxxo9UtlXMwuQU8CMgg1eZXqTRwkSQJWKOI=
 golang.org/x/crypto v0.0.0-20210711020723-a769d52b0f97/go.mod h1:GvvjBRRGRdwPK5ydBHafDWAxML/pGHZbMvKqRZ5+Abc=
+golang.org/x/crypto v0.0.0-20210921155107-089bfa567519 h1:7I4JAnoQBe7ZtJcBaYHi5UtiO8tQHbUSXxL+pnGRANg=
+golang.org/x/crypto v0.0.0-20210921155107-089bfa567519/go.mod h1:GvvjBRRGRdwPK5ydBHafDWAxML/pGHZbMvKqRZ5+Abc=
 golang.org/x/exp v0.0.0-20190121172915-509febef88a4/go.mod h1:CJ0aWSM057203Lf6IL+f9T1iT9GByDxfZKAQTCR3kQA=
 golang.org/x/exp v0.0.0-20190306152737-a1d7652674e8/go.mod h1:CJ0aWSM057203Lf6IL+f9T1iT9GByDxfZKAQTCR3kQA=
 golang.org/x/exp v0.0.0-20190510132918-efd6b22b2522/go.mod h1:ZjyILWgesfNpC6sMxTJOJm9Kp84zZh5NQWvqDGG3Qr8=

input/script_utils.go

@@ -45,6 +45,55 @@ func WitnessScriptHash(witnessScript []byte) ([]byte, error) {
 	return bldr.Script()
 }
 
+// WitnessPubKeyHash generates a pay-to-witness-pubkey-hash public key script
+// paying to a version 0 witness program containing the passed serialized
+// public key.
+func WitnessPubKeyHash(pubkey []byte) ([]byte, error) {
+	bldr := txscript.NewScriptBuilder()
+
+	bldr.AddOp(txscript.OP_0)
+	pkhash := btcutil.Hash160(pubkey)
+	bldr.AddData(pkhash)
+	return bldr.Script()
+}
+
+// GenerateP2SH generates a pay-to-script-hash public key script paying to the
+// passed redeem script.
+func GenerateP2SH(script []byte) ([]byte, error) {
+	bldr := txscript.NewScriptBuilder()
+
+	bldr.AddOp(txscript.OP_HASH160)
+	scripthash := btcutil.Hash160(script)
+	bldr.AddData(scripthash)
+	bldr.AddOp(txscript.OP_EQUAL)
+	return bldr.Script()
+}
+
+// GenerateP2PKH generates a pay-to-public-key-hash public key script paying to
+// the passed serialized public key.
+func GenerateP2PKH(pubkey []byte) ([]byte, error) {
+	bldr := txscript.NewScriptBuilder()
+
+	bldr.AddOp(txscript.OP_DUP)
+	bldr.AddOp(txscript.OP_HASH160)
+	pkhash := btcutil.Hash160(pubkey)
+	bldr.AddData(pkhash)
+	bldr.AddOp(txscript.OP_EQUALVERIFY)
+	bldr.AddOp(txscript.OP_CHECKSIG)
+	return bldr.Script()
+}
+
+// GenerateUnknownWitness generates the maximum-sized witness public key script
+// consisting of a version push and a 40-byte data push.
+func GenerateUnknownWitness() ([]byte, error) {
+	bldr := txscript.NewScriptBuilder()
+
+	bldr.AddOp(txscript.OP_0)
+	witnessScript := make([]byte, 40)
+	bldr.AddData(witnessScript)
+	return bldr.Script()
+}
+
 // GenMultiSigScript generates the non-p2sh'd multisig script for 2 of 2
 // pubkeys.
 func GenMultiSigScript(aPub, bPub []byte) ([]byte, error) {

input/size.go

@@ -41,11 +41,20 @@ const (
 	//      - P2WSHWitnessProgram: 34 bytes
 	NestedP2WSHSize = 1 + P2WSHSize
 
+	// UnknownWitnessSize 42 bytes
+	//      - OP_x: 1 byte
+	//      - OP_DATA: 1 byte (max-size length)
+	//      - max-size: 40 bytes
+	UnknownWitnessSize = 1 + 1 + 40
+
+	// P2PKHSize 25 bytes
+	P2PKHSize = 25
+
 	// P2PKHOutputSize 34 bytes
 	//      - value: 8 bytes
 	//      - var_int: 1 byte (pkscript_length)
 	//      - pkscript (p2pkh): 25 bytes
-	P2PKHOutputSize = 8 + 1 + 25
+	P2PKHOutputSize = 8 + 1 + P2PKHSize
 
 	// P2WKHOutputSize 31 bytes
 	//      - value: 8 bytes
@@ -59,11 +68,14 @@ const (
 	//      - pkscript (p2wsh): 34 bytes
 	P2WSHOutputSize = 8 + 1 + P2WSHSize
 
+	// P2SHSize 23 bytes
+	P2SHSize = 23
+
 	// P2SHOutputSize 32 bytes
 	//      - value: 8 bytes
 	//      - var_int: 1 byte (pkscript_length)
 	//      - pkscript (p2sh): 23 bytes
-	P2SHOutputSize = 8 + 1 + 23
+	P2SHOutputSize = 8 + 1 + P2SHSize
 
 	// P2PKHScriptSigSize 108 bytes
 	//      - OP_DATA: 1 byte (signature length)

lntest/itest/lnd_misc_test.go

@@ -16,6 +16,7 @@ import (
 	"github.com/davecgh/go-spew/spew"
 	"github.com/lightningnetwork/lnd/chainreg"
 	"github.com/lightningnetwork/lnd/funding"
+	"github.com/lightningnetwork/lnd/input"
 	"github.com/lightningnetwork/lnd/lncfg"
 	"github.com/lightningnetwork/lnd/lnrpc"
 	"github.com/lightningnetwork/lnd/lnrpc/routerrpc"
@@ -417,12 +418,15 @@ func testListChannels(net *lntest.NetworkHarness, t *harnessTest) {
 	// Check the returned response is correct.
 	aliceChannel := resp.Channels[0]
 
+	// Calculate the dust limit we'll use for the test.
+	dustLimit := lnwallet.DustLimitForSize(input.UnknownWitnessSize)
+
 	// defaultConstraints is a ChannelConstraints with default values. It is
 	// used to test against Alice's local channel constraints.
 	defaultConstraints := &lnrpc.ChannelConstraints{
 		CsvDelay:          4,
 		ChanReserveSat:    1000,
-		DustLimitSat:      uint64(lnwallet.DefaultDustLimit()),
+		DustLimitSat:      uint64(dustLimit),
 		MaxPendingAmtMsat: 99000000,
 		MinHtlcMsat:       1,
 		MaxAcceptedHtlcs:  bobRemoteMaxHtlcs,
@@ -438,7 +442,7 @@ func testListChannels(net *lntest.NetworkHarness, t *harnessTest) {
 	customizedConstraints := &lnrpc.ChannelConstraints{
 		CsvDelay:          4,
 		ChanReserveSat:    1000,
-		DustLimitSat:      uint64(lnwallet.DefaultDustLimit()),
+		DustLimitSat:      uint64(dustLimit),
 		MaxPendingAmtMsat: 99000000,
 		MinHtlcMsat:       customizedMinHtlc,
 		MaxAcceptedHtlcs:  aliceRemoteMaxHtlcs,

lnwallet/chanfunding/coin_select.go

@@ -219,7 +219,7 @@ func CoinSelectSubtractFees(feeRate chainfee.SatPerKWeight, amt,
 
 	// If the the output is too small after subtracting the fee, the coin
 	// selection cannot be performed with an amount this small.
-	if outputAmt <= dustLimit {
+	if outputAmt < dustLimit {
 		return nil, 0, 0, fmt.Errorf("output amount(%v) after "+
 			"subtracting fees(%v) below dust limit(%v)", outputAmt,
 			requiredFeeNoChange, dustLimit)
@@ -233,7 +233,7 @@ func CoinSelectSubtractFees(feeRate chainfee.SatPerKWeight, amt,
 	// If adding a change output leads to both outputs being above
 	// the dust limit, we'll add the change output. Otherwise we'll
 	// go with the no change tx we originally found.
-	if newChange > dustLimit && newOutput > dustLimit {
+	if newChange >= dustLimit && newOutput >= dustLimit {
 		outputAmt = newOutput
 		changeAmt = newChange
 	}

lnwallet/chanfunding/coin_select_test.go

@@ -383,7 +383,7 @@ func TestCoinSelectSubtractFees(t *testing.T) {
 				{
 					TxOut: wire.TxOut{
 						PkScript: p2wkhScript,
-						Value:    int64(fundingFee(feeRate, 1, false) + dustLimit),
+						Value:    int64(fundingFee(feeRate, 1, false) + dustLimit - 1),
 					},
 				},
 			},

lnwallet/chanfunding/wallet_assembler.go

@@ -304,7 +304,7 @@ func (w *WalletAssembler) ProvisionChannel(r *Request) (Intent, error) {
 
 		// Sanity check: The addition of the outputs should not lead to the
 		// creation of dust.
-		if changeAmt != 0 && changeAmt <= w.cfg.DustLimit {
+		if changeAmt != 0 && changeAmt < w.cfg.DustLimit {
 			return fmt.Errorf("change amount(%v) after coin "+
 				"select is below dust limit(%v)", changeAmt,
 				w.cfg.DustLimit)

lnwallet/errors.go

@@ -152,6 +152,14 @@ func ErrChanTooLarge(chanSize, maxChanSize btcutil.Amount) ReservationError {
 	}
 }
 
+// ErrInvalidDustLimit returns an error indicating that a proposed DustLimit
+// was rejected.
+func ErrInvalidDustLimit(dustLimit btcutil.Amount) ReservationError {
+	return ReservationError{
+		fmt.Errorf("dust limit %v is invalid", dustLimit),
+	}
+}
+
 // ErrHtlcIndexAlreadyFailed is returned when the HTLC index has already been
 // failed, but has not been committed by our commitment state.
 type ErrHtlcIndexAlreadyFailed uint64

lnwallet/parameters.go

@@ -1,13 +1,50 @@
 package lnwallet
 
 import (
+	"github.com/btcsuite/btcd/mempool"
+	"github.com/btcsuite/btcd/wire"
 	"github.com/btcsuite/btcutil"
-	"github.com/btcsuite/btcwallet/wallet/txrules"
 	"github.com/lightningnetwork/lnd/input"
 )
 
-// DefaultDustLimit is used to calculate the dust HTLC amount which will be
+// DustLimitForSize retrieves the dust limit for a given pkscript size. Given
-// send to other node during funding process.
+// the size, it automatically determines whether the script is a witness script
-func DefaultDustLimit() btcutil.Amount {
+// or not. It calls btcd's GetDustThreshold method under the hood. It must be
-	return txrules.GetDustThreshold(input.P2WSHSize, txrules.DefaultRelayFeePerKb)
+// called with a proper size parameter or else a panic occurs.
+func DustLimitForSize(scriptSize int) btcutil.Amount {
+	var (
+		dustlimit btcutil.Amount
+		pkscript  []byte
+	)
+
+	// With the size of the script, determine which type of pkscript to
+	// create. This will be used in the call to GetDustThreshold. We pass
+	// in an empty byte slice since the contents of the script itself don't
+	// matter.
+	switch scriptSize {
+	case input.P2WPKHSize:
+		pkscript, _ = input.WitnessPubKeyHash([]byte{})
+
+	case input.P2WSHSize:
+		pkscript, _ = input.WitnessScriptHash([]byte{})
+
+	case input.P2SHSize:
+		pkscript, _ = input.GenerateP2SH([]byte{})
+
+	case input.P2PKHSize:
+		pkscript, _ = input.GenerateP2PKH([]byte{})
+
+	case input.UnknownWitnessSize:
+		pkscript, _ = input.GenerateUnknownWitness()
+
+	default:
+		panic("invalid script size")
+	}
+
+	// Call GetDustThreshold with a TxOut containing the generated
+	// pkscript.
+	txout := &wire.TxOut{PkScript: pkscript}
+	dustlimit = btcutil.Amount(mempool.GetDustThreshold(txout))
+
+	return dustlimit
 }

lnwallet/parameters_test.go

@@ -0,0 +1,56 @@
+package lnwallet
+
+import (
+	"testing"
+
+	"github.com/btcsuite/btcutil"
+	"github.com/lightningnetwork/lnd/input"
+	"github.com/stretchr/testify/require"
+)
+
+// TestDustLimitForSize tests that we receive the expected dust limits for
+// various script types from btcd's GetDustThreshold function.
+func TestDustLimitForSize(t *testing.T) {
+	t.Parallel()
+
+	tests := []struct {
+		name          string
+		size          int
+		expectedLimit btcutil.Amount
+	}{
+		{
+			name:          "p2pkh dust limit",
+			size:          input.P2PKHSize,
+			expectedLimit: btcutil.Amount(546),
+		},
+		{
+			name:          "p2sh dust limit",
+			size:          input.P2SHSize,
+			expectedLimit: btcutil.Amount(540),
+		},
+		{
+			name:          "p2wpkh dust limit",
+			size:          input.P2WPKHSize,
+			expectedLimit: btcutil.Amount(294),
+		},
+		{
+			name:          "p2wsh dust limit",
+			size:          input.P2WSHSize,
+			expectedLimit: btcutil.Amount(330),
+		},
+		{
+			name:          "unknown witness limit",
+			size:          input.UnknownWitnessSize,
+			expectedLimit: btcutil.Amount(354),
+		},
+	}
+
+	for _, test := range tests {
+		test := test
+
+		t.Run(test.name, func(t *testing.T) {
+			dustlimit := DustLimitForSize(test.size)
+			require.Equal(t, test.expectedLimit, dustlimit)
+		})
+	}
+}

lnwallet/reservation.go

@@ -205,6 +205,9 @@ func NewChannelReservation(capacity, localFundingAmt btcutil.Amount,
 		feeMSat += 2 * lnwire.NewMSatFromSatoshis(anchorSize)
 	}
 
+	// Used to cut down on verbosity.
+	defaultDust := wallet.Cfg.DefaultConstraints.DustLimit
+
 	// If we're the responder to a single-funder reservation, then we have
 	// no initial balance in the channel unless the remote party is pushing
 	// some funds to us within the first commitment state.
@@ -218,7 +221,7 @@ func NewChannelReservation(capacity, localFundingAmt btcutil.Amount,
 		if int64(theirBalance) < 0 {
 			return nil, ErrFunderBalanceDust(
 				int64(commitFee), int64(theirBalance.ToSatoshis()),
-				int64(2*DefaultDustLimit()),
+				int64(2*defaultDust),
 			)
 		}
 	} else {
@@ -247,7 +250,7 @@ func NewChannelReservation(capacity, localFundingAmt btcutil.Amount,
 		if int64(ourBalance) < 0 {
 			return nil, ErrFunderBalanceDust(
 				int64(commitFee), int64(ourBalance),
-				int64(2*DefaultDustLimit()),
+				int64(2*defaultDust),
 			)
 		}
 	}
@@ -257,21 +260,21 @@ func NewChannelReservation(capacity, localFundingAmt btcutil.Amount,
 	// reject this channel creation request.
 	//
 	// TODO(roasbeef): reject if 30% goes to fees? dust channel
-	if initiator && ourBalance.ToSatoshis() <= 2*DefaultDustLimit() {
+	if initiator && ourBalance.ToSatoshis() <= 2*defaultDust {
 		return nil, ErrFunderBalanceDust(
 			int64(commitFee),
 			int64(ourBalance.ToSatoshis()),
-			int64(2*DefaultDustLimit()),
+			int64(2*defaultDust),
 		)
 	}
 
 	// Similarly we ensure their balance is reasonable if we are not the
 	// initiator.
-	if !initiator && theirBalance.ToSatoshis() <= 2*DefaultDustLimit() {
+	if !initiator && theirBalance.ToSatoshis() <= 2*defaultDust {
 		return nil, ErrFunderBalanceDust(
 			int64(commitFee),
 			int64(theirBalance.ToSatoshis()),
-			int64(2*DefaultDustLimit()),
+			int64(2*defaultDust),
 		)
 	}
 
@@ -391,7 +394,7 @@ func (r *ChannelReservation) SetNumConfsRequired(numConfs uint16) {
 // will also attempt to verify the constraints for sanity, returning an error
 // if the parameters are seemed unsound.
 func (r *ChannelReservation) CommitConstraints(c *channeldb.ChannelConstraints,
-	maxLocalCSVDelay uint16) error {
+	maxLocalCSVDelay uint16, responder bool) error {
 	r.Lock()
 	defer r.Unlock()
 
@@ -406,6 +409,13 @@ func (r *ChannelReservation) CommitConstraints(c *channeldb.ChannelConstraints,
 		return ErrChanReserveTooSmall(c.ChanReserve, c.DustLimit)
 	}
 
+	// Validate against the maximum-sized witness script dust limit, and
+	// also ensure that the DustLimit is not too large.
+	maxWitnessLimit := DustLimitForSize(input.UnknownWitnessSize)
+	if c.DustLimit < maxWitnessLimit || c.DustLimit > 3*maxWitnessLimit {
+		return ErrInvalidDustLimit(c.DustLimit)
+	}
+
 	// Fail if we consider the channel reserve to be too large.  We
 	// currently fail if it is greater than 20% of the channel capacity.
 	maxChanReserve := r.partialState.Capacity / 5
@@ -446,7 +456,7 @@ func (r *ChannelReservation) CommitConstraints(c *channeldb.ChannelConstraints,
 
 	// Our dust limit should always be less than or equal to our proposed
 	// channel reserve.
-	if r.ourContribution.DustLimit > c.ChanReserve {
+	if responder && r.ourContribution.DustLimit > c.ChanReserve {
 		r.ourContribution.DustLimit = c.ChanReserve
 	}
 
@@ -459,6 +469,31 @@ func (r *ChannelReservation) CommitConstraints(c *channeldb.ChannelConstraints,
 	return nil
 }
 
+// validateReserveBounds checks that both ChannelReserve values are above both
+// DustLimit values. This not only avoids stuck channels, but is also mandated
+// by BOLT#02 even if it's not explicit. This returns true if the bounds are
+// valid. This function should be called with the lock held.
+func (r *ChannelReservation) validateReserveBounds() bool {
+	ourDustLimit := r.ourContribution.DustLimit
+	ourRequiredReserve := r.ourContribution.ChanReserve
+	theirDustLimit := r.theirContribution.DustLimit
+	theirRequiredReserve := r.theirContribution.ChanReserve
+
+	// We take the smaller of the two ChannelReserves and compare it
+	// against the larger of the two DustLimits.
+	minChanReserve := ourRequiredReserve
+	if minChanReserve > theirRequiredReserve {
+		minChanReserve = theirRequiredReserve
+	}
+
+	maxDustLimit := ourDustLimit
+	if maxDustLimit < theirDustLimit {
+		maxDustLimit = theirDustLimit
+	}
+
+	return minChanReserve >= maxDustLimit
+}
+
 // OurContribution returns the wallet's fully populated contribution to the
 // pending payment channel. See 'ChannelContribution' for further details
 // regarding the contents of a contribution.

lnwallet/test/test_interface.go

@@ -446,7 +446,7 @@ func testDualFundingReservationWorkflow(miner *rpctest.Harness,
 	}
 	aliceChanReservation.SetNumConfsRequired(numReqConfs)
 	channelConstraints := &channeldb.ChannelConstraints{
-		DustLimit:        lnwallet.DefaultDustLimit(),
+		DustLimit:        alice.Cfg.DefaultConstraints.DustLimit,
 		ChanReserve:      fundingAmount / 100,
 		MaxPendingAmount: lnwire.NewMSatFromSatoshis(fundingAmount),
 		MinHTLC:          1,
@@ -454,7 +454,7 @@ func testDualFundingReservationWorkflow(miner *rpctest.Harness,
 		CsvDelay:         csvDelay,
 	}
 	err = aliceChanReservation.CommitConstraints(
-		channelConstraints, defaultMaxLocalCsvDelay,
+		channelConstraints, defaultMaxLocalCsvDelay, false,
 	)
 	if err != nil {
 		t.Fatalf("unable to verify constraints: %v", err)
@@ -490,7 +490,7 @@ func testDualFundingReservationWorkflow(miner *rpctest.Harness,
 		t.Fatalf("bob unable to init channel reservation: %v", err)
 	}
 	err = bobChanReservation.CommitConstraints(
-		channelConstraints, defaultMaxLocalCsvDelay,
+		channelConstraints, defaultMaxLocalCsvDelay, true,
 	)
 	if err != nil {
 		t.Fatalf("unable to verify constraints: %v", err)
@@ -896,7 +896,7 @@ func testSingleFunderReservationWorkflow(miner *rpctest.Harness,
 	}
 	aliceChanReservation.SetNumConfsRequired(numReqConfs)
 	channelConstraints := &channeldb.ChannelConstraints{
-		DustLimit:        lnwallet.DefaultDustLimit(),
+		DustLimit:        alice.Cfg.DefaultConstraints.DustLimit,
 		ChanReserve:      fundingAmt / 100,
 		MaxPendingAmount: lnwire.NewMSatFromSatoshis(fundingAmt),
 		MinHTLC:          1,
@@ -904,7 +904,7 @@ func testSingleFunderReservationWorkflow(miner *rpctest.Harness,
 		CsvDelay:         csvDelay,
 	}
 	err = aliceChanReservation.CommitConstraints(
-		channelConstraints, defaultMaxLocalCsvDelay,
+		channelConstraints, defaultMaxLocalCsvDelay, false,
 	)
 	if err != nil {
 		t.Fatalf("unable to verify constraints: %v", err)
@@ -947,7 +947,7 @@ func testSingleFunderReservationWorkflow(miner *rpctest.Harness,
 		t.Fatalf("unable to create bob reservation: %v", err)
 	}
 	err = bobChanReservation.CommitConstraints(
-		channelConstraints, defaultMaxLocalCsvDelay,
+		channelConstraints, defaultMaxLocalCsvDelay, true,
 	)
 	if err != nil {
 		t.Fatalf("unable to verify constraints: %v", err)

lnwallet/transactions_test.go

@@ -542,16 +542,19 @@ func testSpendValidation(t *testing.T, tweakless bool) {
 		Privkeys: []*btcec.PrivateKey{aliceKeyPriv},
 	}
 
+	// Calculate the dust limit we'll use for the test.
+	dustLimit := DustLimitForSize(input.UnknownWitnessSize)
+
 	aliceChanCfg := &channeldb.ChannelConfig{
 		ChannelConstraints: channeldb.ChannelConstraints{
-			DustLimit: DefaultDustLimit(),
+			DustLimit: dustLimit,
 			CsvDelay:  csvTimeout,
 		},
 	}
 
 	bobChanCfg := &channeldb.ChannelConfig{
 		ChannelConstraints: channeldb.ChannelConstraints{
-			DustLimit: DefaultDustLimit(),
+			DustLimit: dustLimit,
 			CsvDelay:  csvTimeout,
 		},
 	}

lnwallet/wallet.go

@@ -689,12 +689,15 @@ func (l *LightningWallet) handleFundingReserveRequest(req *InitFundingReserveMsg
 	// If no chanFunder was provided, then we'll assume the default
 	// assembler, which is backed by the wallet's internal coin selection.
 	if req.ChanFunder == nil {
+		// We use the P2WSH dust limit since it is larger than the
+		// P2WPKH dust limit and to avoid threading through two
+		// different dust limits.
 		cfg := chanfunding.WalletConfig{
 			CoinSource:       &CoinSource{l},
 			CoinSelectLocker: l,
 			CoinLocker:       l,
 			Signer:           l.Cfg.Signer,
-			DustLimit:        DefaultDustLimit(),
+			DustLimit:        DustLimitForSize(input.P2WSHSize),
 		}
 		req.ChanFunder = chanfunding.NewWalletAssembler(cfg)
 	}
@@ -1263,6 +1266,13 @@ func (l *LightningWallet) handleContributionMsg(req *addContributionMsg) {
 	theirContribution := req.contribution
 	ourContribution := pendingReservation.ourContribution
 
+	// Perform bounds-checking on both ChannelReserve and DustLimit
+	// parameters.
+	if !pendingReservation.validateReserveBounds() {
+		req.err <- fmt.Errorf("invalid reserve and dust bounds")
+		return
+	}
+
 	var (
 		chanPoint *wire.OutPoint
 		err       error
@@ -1561,9 +1571,6 @@ func (l *LightningWallet) handleSingleContribution(req *addSingleContributionMsg
 	pendingReservation.Lock()
 	defer pendingReservation.Unlock()
 
-	// TODO(roasbeef): verify sanity of remote party's parameters, fail if
-	// disagree
-
 	// Validate that the remote's UpfrontShutdownScript is a valid script
 	// if it's set.
 	shutdown := req.contribution.UpfrontShutdown
@@ -1581,6 +1588,14 @@ func (l *LightningWallet) handleSingleContribution(req *addSingleContributionMsg
 	theirContribution := pendingReservation.theirContribution
 	chanState := pendingReservation.partialState
 
+	// Perform bounds checking on both ChannelReserve and DustLimit
+	// parameters. The ChannelReserve may have been changed by the
+	// ChannelAcceptor RPC, so this is necessary.
+	if !pendingReservation.validateReserveBounds() {
+		req.err <- fmt.Errorf("invalid reserve and dust bounds")
+		return
+	}
+
 	// Initialize an empty sha-chain for them, tracking the current pending
 	// revocation hash (we don't yet know the preimage so we can't add it
 	// to the chain).

rpcserver.go

@@ -1227,8 +1227,7 @@ func (r *rpcServer) SendCoins(ctx context.Context,
 		// pay to the change address created above if we needed to
 		// reserve any value, the rest will go to targetAddr.
 		sweepTxPkg, err := sweep.CraftSweepAllTx(
-			feePerKw, lnwallet.DefaultDustLimit(),
+			feePerKw, uint32(bestHeight), nil, targetAddr, wallet,
-			uint32(bestHeight), nil, targetAddr, wallet,
 			wallet, wallet.WalletController,
 			r.server.cc.FeeEstimator, r.server.cc.Signer,
 			minConfs,
@@ -1280,9 +1279,9 @@ func (r *rpcServer) SendCoins(ctx context.Context,
 			}
 
 			sweepTxPkg, err = sweep.CraftSweepAllTx(
-				feePerKw, lnwallet.DefaultDustLimit(),
+				feePerKw, uint32(bestHeight), outputs,
-				uint32(bestHeight), outputs, targetAddr, wallet,
+				targetAddr, wallet, wallet,
-				wallet, wallet.WalletController,
+				wallet.WalletController,
 				r.server.cc.FeeEstimator, r.server.cc.Signer,
 				minConfs,
 			)

sweep/sweeper.go

@@ -1150,7 +1150,7 @@ func (s *UtxoSweeper) getInputLists(cluster inputCluster,
 	if len(retryInputs) > 0 {
 		var err error
 		allSets, err = generateInputPartitionings(
-			append(retryInputs, newInputs...), s.relayFeeRate,
+			append(retryInputs, newInputs...),
 			cluster.sweepFeeRate, s.cfg.MaxInputsPerTx,
 			s.cfg.Wallet,
 		)
@@ -1161,8 +1161,8 @@ func (s *UtxoSweeper) getInputLists(cluster inputCluster,
 
 	// Create sets for just the new inputs.
 	newSets, err := generateInputPartitionings(
-		newInputs, s.relayFeeRate, cluster.sweepFeeRate,
+		newInputs, cluster.sweepFeeRate, s.cfg.MaxInputsPerTx,
-		s.cfg.MaxInputsPerTx, s.cfg.Wallet,
+		s.cfg.Wallet,
 	)
 	if err != nil {
 		return nil, fmt.Errorf("input partitionings: %v", err)
@@ -1193,7 +1193,7 @@ func (s *UtxoSweeper) sweep(inputs inputSet, feeRate chainfee.SatPerKWeight,
 	// Create sweep tx.
 	tx, err := createSweepTx(
 		inputs, nil, s.currentOutputScript, uint32(currentHeight),
-		feeRate, dustLimit(s.relayFeeRate), s.cfg.Signer,
+		feeRate, s.cfg.Signer,
 	)
 	if err != nil {
 		return fmt.Errorf("create sweep tx: %v", err)
@@ -1488,7 +1488,7 @@ func (s *UtxoSweeper) CreateSweepTx(inputs []input.Input, feePref FeePreference,
 
 	return createSweepTx(
 		inputs, nil, pkScript, currentBlockHeight, feePerKw,
-		dustLimit(s.relayFeeRate), s.cfg.Signer,
+		s.cfg.Signer,
 	)
 }
 

sweep/sweeper_test.go

@@ -136,7 +136,8 @@ func createSweeperTestContext(t *testing.T) *sweeperTestContext {
 		Store:  store,
 		Signer: &mock.DummySigner{},
 		GenSweepScript: func() ([]byte, error) {
-			script := []byte{outputScriptCount}
+			script := make([]byte, input.P2WPKHSize)
+			script[0] = outputScriptCount
 			outputScriptCount++
 			return script, nil
 		},
@@ -1801,6 +1802,24 @@ func TestRequiredTxOuts(t *testing.T) {
 	locktime2 := uint32(52)
 	locktime3 := uint32(53)
 
+	aPkScript := make([]byte, input.P2WPKHSize)
+	aPkScript[0] = 'a'
+
+	bPkScript := make([]byte, input.P2WSHSize)
+	bPkScript[0] = 'b'
+
+	cPkScript := make([]byte, input.P2PKHSize)
+	cPkScript[0] = 'c'
+
+	dPkScript := make([]byte, input.P2SHSize)
+	dPkScript[0] = 'd'
+
+	ePkScript := make([]byte, input.UnknownWitnessSize)
+	ePkScript[0] = 'e'
+
+	fPkScript := make([]byte, input.P2WSHSize)
+	fPkScript[0] = 'f'
+
 	testCases := []struct {
 		name         string
 		inputs       []*testInput
@@ -1815,7 +1834,7 @@ func TestRequiredTxOuts(t *testing.T) {
 				{
 					BaseInput: inputs[0],
 					reqTxOut: &wire.TxOut{
-						PkScript: []byte("aaa"),
+						PkScript: aPkScript,
 						Value:    100000,
 					},
 				},
@@ -1836,7 +1855,7 @@ func TestRequiredTxOuts(t *testing.T) {
 				// output must be the first one.
 				require.Equal(t, 2, len(tx.TxOut))
 				out := tx.TxOut[0]
-				require.Equal(t, []byte("aaa"), out.PkScript)
+				require.Equal(t, aPkScript, out.PkScript)
 				require.Equal(t, int64(100000), out.Value)
 			},
 		},
@@ -1848,13 +1867,13 @@ func TestRequiredTxOuts(t *testing.T) {
 				{
 					BaseInput: inputs[0],
 					reqTxOut: &wire.TxOut{
-						PkScript: []byte("aaa"),
+						PkScript: aPkScript,
 
 						// Fee will be about 5340 sats.
 						// Subtract a bit more to
 						// ensure no dust change output
 						// is manifested.
-						Value: inputs[0].SignDesc().Output.Value - 5600,
+						Value: inputs[0].SignDesc().Output.Value - 6300,
 					},
 				},
 			},
@@ -1871,10 +1890,10 @@ func TestRequiredTxOuts(t *testing.T) {
 
 				require.Equal(t, 1, len(tx.TxOut))
 				out := tx.TxOut[0]
-				require.Equal(t, []byte("aaa"), out.PkScript)
+				require.Equal(t, aPkScript, out.PkScript)
 				require.Equal(
 					t,
-					inputs[0].SignDesc().Output.Value-5600,
+					inputs[0].SignDesc().Output.Value-6300,
 					out.Value,
 				)
 			},
@@ -1897,7 +1916,7 @@ func TestRequiredTxOuts(t *testing.T) {
 					// The second input requires a TxOut.
 					BaseInput: inputs[0],
 					reqTxOut: &wire.TxOut{
-						PkScript: []byte("aaa"),
+						PkScript: aPkScript,
 						Value:    inputs[0].SignDesc().Output.Value,
 					},
 				},
@@ -1916,7 +1935,7 @@ func TestRequiredTxOuts(t *testing.T) {
 
 				// The required TxOut should be the first one.
 				out := tx.TxOut[0]
-				require.Equal(t, []byte("aaa"), out.PkScript)
+				require.Equal(t, aPkScript, out.PkScript)
 				require.Equal(
 					t, inputs[0].SignDesc().Output.Value,
 					out.Value,
@@ -1947,7 +1966,7 @@ func TestRequiredTxOuts(t *testing.T) {
 				{
 					BaseInput: inputs[0],
 					reqTxOut: &wire.TxOut{
-						PkScript: []byte("aaa"),
+						PkScript: aPkScript,
 						Value:    inputs[0].SignDesc().Output.Value,
 					},
 				},
@@ -1965,7 +1984,7 @@ func TestRequiredTxOuts(t *testing.T) {
 
 				require.Equal(t, 2, len(tx.TxOut))
 				out := tx.TxOut[0]
-				require.Equal(t, []byte("aaa"), out.PkScript)
+				require.Equal(t, aPkScript, out.PkScript)
 				require.Equal(
 					t, inputs[0].SignDesc().Output.Value,
 					out.Value,
@@ -1980,21 +1999,21 @@ func TestRequiredTxOuts(t *testing.T) {
 				{
 					BaseInput: inputs[0],
 					reqTxOut: &wire.TxOut{
-						PkScript: []byte("aaa"),
+						PkScript: aPkScript,
 						Value:    inputs[0].SignDesc().Output.Value,
 					},
 				},
 				{
 					BaseInput: inputs[1],
 					reqTxOut: &wire.TxOut{
-						PkScript: []byte("bbb"),
+						PkScript: bPkScript,
 						Value:    inputs[1].SignDesc().Output.Value,
 					},
 				},
 				{
 					BaseInput: inputs[2],
 					reqTxOut: &wire.TxOut{
-						PkScript: []byte("ccc"),
+						PkScript: cPkScript,
 						Value:    inputs[2].SignDesc().Output.Value,
 					},
 				},
@@ -2041,7 +2060,7 @@ func TestRequiredTxOuts(t *testing.T) {
 					BaseInput: inputs[0],
 					locktime:  &locktime1,
 					reqTxOut: &wire.TxOut{
-						PkScript: []byte("aaa"),
+						PkScript: aPkScript,
 						Value:    inputs[0].SignDesc().Output.Value,
 					},
 				},
@@ -2049,7 +2068,7 @@ func TestRequiredTxOuts(t *testing.T) {
 					BaseInput: inputs[1],
 					locktime:  &locktime1,
 					reqTxOut: &wire.TxOut{
-						PkScript: []byte("bbb"),
+						PkScript: bPkScript,
 						Value:    inputs[1].SignDesc().Output.Value,
 					},
 				},
@@ -2057,7 +2076,7 @@ func TestRequiredTxOuts(t *testing.T) {
 					BaseInput: inputs[2],
 					locktime:  &locktime2,
 					reqTxOut: &wire.TxOut{
-						PkScript: []byte("ccc"),
+						PkScript: cPkScript,
 						Value:    inputs[2].SignDesc().Output.Value,
 					},
 				},
@@ -2065,7 +2084,7 @@ func TestRequiredTxOuts(t *testing.T) {
 					BaseInput: inputs[3],
 					locktime:  &locktime2,
 					reqTxOut: &wire.TxOut{
-						PkScript: []byte("ddd"),
+						PkScript: dPkScript,
 						Value:    inputs[3].SignDesc().Output.Value,
 					},
 				},
@@ -2073,7 +2092,7 @@ func TestRequiredTxOuts(t *testing.T) {
 					BaseInput: inputs[4],
 					locktime:  &locktime3,
 					reqTxOut: &wire.TxOut{
-						PkScript: []byte("eee"),
+						PkScript: ePkScript,
 						Value:    inputs[4].SignDesc().Output.Value,
 					},
 				},
@@ -2081,7 +2100,7 @@ func TestRequiredTxOuts(t *testing.T) {
 					BaseInput: inputs[5],
 					locktime:  &locktime3,
 					reqTxOut: &wire.TxOut{
-						PkScript: []byte("fff"),
+						PkScript: fPkScript,
 						Value:    inputs[5].SignDesc().Output.Value,
 					},
 				},

sweep/tx_input_set.go

@@ -7,7 +7,6 @@ import (
 	"github.com/btcsuite/btcd/txscript"
 	"github.com/btcsuite/btcd/wire"
 	"github.com/btcsuite/btcutil"
-	"github.com/btcsuite/btcwallet/wallet/txrules"
 	"github.com/lightningnetwork/lnd/input"
 	"github.com/lightningnetwork/lnd/lnwallet"
 	"github.com/lightningnetwork/lnd/lnwallet/chainfee"
@@ -109,9 +108,6 @@ func (t *txInputSetState) clone() txInputSetState {
 type txInputSet struct {
 	txInputSetState
 
-	// dustLimit is the minimum output value of the tx.
-	dustLimit btcutil.Amount
-
 	// maxInputs is the maximum number of inputs that will be accepted in
 	// the set.
 	maxInputs int
@@ -121,25 +117,15 @@ type txInputSet struct {
 	wallet Wallet
 }
 
-func dustLimit(relayFee chainfee.SatPerKWeight) btcutil.Amount {
-	return txrules.GetDustThreshold(
-		input.P2WPKHSize,
-		btcutil.Amount(relayFee.FeePerKVByte()),
-	)
-}
-
 // newTxInputSet constructs a new, empty input set.
-func newTxInputSet(wallet Wallet, feePerKW,
+func newTxInputSet(wallet Wallet, feePerKW chainfee.SatPerKWeight,
-	relayFee chainfee.SatPerKWeight, maxInputs int) *txInputSet {
+	maxInputs int) *txInputSet {
-
-	dustLimit := dustLimit(relayFee)
 
 	state := txInputSetState{
 		feeRate: feePerKW,
 	}
 
 	b := txInputSet{
-		dustLimit:       dustLimit,
 		maxInputs:       maxInputs,
 		wallet:          wallet,
 		txInputSetState: state,
@@ -153,7 +139,7 @@ func newTxInputSet(wallet Wallet, feePerKW,
 func (t *txInputSet) enoughInput() bool {
 	// If we have a change output above dust, then we certainly have enough
 	// inputs to the transaction.
-	if t.changeOutput >= t.dustLimit {
+	if t.changeOutput >= lnwallet.DustLimitForSize(input.P2WPKHSize) {
 		return true
 	}
 
@@ -192,8 +178,12 @@ func (t *txInputSet) addToState(inp input.Input, constraints addConstraints) *tx
 	// If the input comes with a required tx out that is below dust, we
 	// won't add it.
 	reqOut := inp.RequiredTxOut()
-	if reqOut != nil && btcutil.Amount(reqOut.Value) < t.dustLimit {
+	if reqOut != nil {
-		return nil
+		// Fetch the dust limit for this output.
+		dustLimit := lnwallet.DustLimitForSize(len(reqOut.PkScript))
+		if btcutil.Amount(reqOut.Value) < dustLimit {
+			return nil
+		}
 	}
 
 	// Clone the current set state.

sweep/tx_input_set_test.go

@@ -14,14 +14,9 @@ import (
 func TestTxInputSet(t *testing.T) {
 	const (
 		feeRate   = 1000
-		relayFee  = 300
 		maxInputs = 10
 	)
-	set := newTxInputSet(nil, feeRate, relayFee, maxInputs)
+	set := newTxInputSet(nil, feeRate, maxInputs)
-
-	if set.dustLimit != 537 {
-		t.Fatalf("incorrect dust limit")
-	}
 
 	// Create a 300 sat input. The fee to sweep this input to a P2WKH output
 	// is 439 sats. That means that this input yields -139 sats and we
@@ -66,16 +61,15 @@ func TestTxInputSet(t *testing.T) {
 func TestTxInputSetFromWallet(t *testing.T) {
 	const (
 		feeRate   = 500
-		relayFee  = 300
 		maxInputs = 10
 	)
 
 	wallet := &mockWallet{}
-	set := newTxInputSet(wallet, feeRate, relayFee, maxInputs)
+	set := newTxInputSet(wallet, feeRate, maxInputs)
 
-	// Add a 700 sat input to the set. It yields positively, but doesn't
+	// Add a 500 sat input to the set. It yields positively, but doesn't
 	// reach the output dust limit.
-	if !set.add(createP2WKHInput(700), constraintsRegular) {
+	if !set.add(createP2WKHInput(500), constraintsRegular) {
 		t.Fatal("expected add of positively yielding input to succeed")
 	}
 	if set.enoughInput() {
@@ -138,13 +132,9 @@ func (r *reqInput) RequiredTxOut() *wire.TxOut {
 func TestTxInputSetRequiredOutput(t *testing.T) {
 	const (
 		feeRate   = 1000
-		relayFee  = 300
 		maxInputs = 10
 	)
-	set := newTxInputSet(nil, feeRate, relayFee, maxInputs)
+	set := newTxInputSet(nil, feeRate, maxInputs)
-	if set.dustLimit != 537 {
-		t.Fatalf("incorrect dust limit")
-	}
 
 	// Attempt to add an input with a required txout below the dust limit.
 	// This should fail since we cannot trim such outputs.
@@ -152,7 +142,7 @@ func TestTxInputSetRequiredOutput(t *testing.T) {
 		Input: createP2WKHInput(500),
 		txOut: &wire.TxOut{
 			Value:    500,
-			PkScript: make([]byte, 33),
+			PkScript: make([]byte, input.P2PKHSize),
 		},
 	}
 	require.False(t, set.add(inp, constraintsRegular),
@@ -164,7 +154,7 @@ func TestTxInputSetRequiredOutput(t *testing.T) {
 		Input: createP2WKHInput(1000),
 		txOut: &wire.TxOut{
 			Value:    1000,
-			PkScript: make([]byte, 22),
+			PkScript: make([]byte, input.P2WPKHSize),
 		},
 	}
 	require.True(t, set.add(inp, constraintsRegular), "failed adding input")

sweep/txgenerator.go

@@ -10,6 +10,7 @@ import (
 	"github.com/btcsuite/btcd/wire"
 	"github.com/btcsuite/btcutil"
 	"github.com/lightningnetwork/lnd/input"
+	"github.com/lightningnetwork/lnd/lnwallet"
 	"github.com/lightningnetwork/lnd/lnwallet/chainfee"
 )
 
@@ -37,8 +38,8 @@ type inputSet []input.Input
 // inputs are skipped. No input sets with a total value after fees below the
 // dust limit are returned.
 func generateInputPartitionings(sweepableInputs []txInput,
-	relayFeePerKW, feePerKW chainfee.SatPerKWeight,
+	feePerKW chainfee.SatPerKWeight, maxInputsPerTx int,
-	maxInputsPerTx int, wallet Wallet) ([]inputSet, error) {
+	wallet Wallet) ([]inputSet, error) {
 
 	// Sort input by yield. We will start constructing input sets starting
 	// with the highest yield inputs. This is to prevent the construction
@@ -85,9 +86,7 @@ func generateInputPartitionings(sweepableInputs []txInput,
 		// Start building a set of positive-yield tx inputs under the
 		// condition that the tx will be published with the specified
 		// fee rate.
-		txInputs := newTxInputSet(
+		txInputs := newTxInputSet(wallet, feePerKW, maxInputsPerTx)
-			wallet, feePerKW, relayFeePerKW, maxInputsPerTx,
-		)
 
 		// From the set of sweepable inputs, keep adding inputs to the
 		// input set until the tx output value no longer goes up or the
@@ -111,10 +110,12 @@ func generateInputPartitionings(sweepableInputs []txInput,
 		// continuing with the remaining inputs will only lead to sets
 		// with an even lower output value.
 		if !txInputs.enoughInput() {
+			// The change output is always a p2wpkh here.
+			dl := lnwallet.DustLimitForSize(input.P2WPKHSize)
 			log.Debugf("Set value %v (r=%v, c=%v) below dust "+
 				"limit of %v", txInputs.totalOutput(),
 				txInputs.requiredOutput, txInputs.changeOutput,
-				txInputs.dustLimit)
+				dl)
 			return sets, nil
 		}
 
@@ -135,8 +136,8 @@ func generateInputPartitionings(sweepableInputs []txInput,
 // sending any leftover change to the change script.
 func createSweepTx(inputs []input.Input, outputs []*wire.TxOut,
 	changePkScript []byte, currentBlockHeight uint32,
-	feePerKw chainfee.SatPerKWeight, dustLimit btcutil.Amount,
+	feePerKw chainfee.SatPerKWeight, signer input.Signer) (*wire.MsgTx,
-	signer input.Signer) (*wire.MsgTx, error) {
+	error) {
 
 	inputs, estimator := getWeightEstimate(inputs, outputs, feePerKw)
 	txFee := estimator.fee()
@@ -227,16 +228,20 @@ func createSweepTx(inputs []input.Input, outputs []*wire.TxOut,
 	// sweep tx has a change output.
 	changeAmt := totalInput - requiredOutput - txFee
 
+	// We'll calculate the dust limit for the given changePkScript since it
+	// is variable.
+	changeLimit := lnwallet.DustLimitForSize(len(changePkScript))
+
 	// The txn will sweep the amount after fees to the pkscript generated
 	// above.
-	if changeAmt >= dustLimit {
+	if changeAmt >= changeLimit {
 		sweepTx.AddTxOut(&wire.TxOut{
 			PkScript: changePkScript,
 			Value:    int64(changeAmt),
 		})
 	} else {
 		log.Infof("Change amt %v below dustlimit %v, not adding "+
-			"change output", changeAmt, dustLimit)
+			"change output", changeAmt, changeLimit)
 	}
 
 	// We'll default to using the current block height as locktime, if none

sweep/walletsweep.go

@@ -165,8 +165,8 @@ type DeliveryAddr struct {
 // output, as specified by the change address. The sweep transaction will be
 // crafted with the target fee rate, and will use the utxoSource and
 // outpointLocker as sources for wallet funds.
-func CraftSweepAllTx(feeRate chainfee.SatPerKWeight, dustLimit btcutil.Amount,
+func CraftSweepAllTx(feeRate chainfee.SatPerKWeight, blockHeight uint32,
-	blockHeight uint32, deliveryAddrs []DeliveryAddr, changeAddr btcutil.Address,
+	deliveryAddrs []DeliveryAddr, changeAddr btcutil.Address,
 	coinSelectLocker CoinSelectionLocker, utxoSource UtxoSource,
 	outpointLocker OutpointLocker, feeEstimator chainfee.Estimator,
 	signer input.Signer, minConfs int32) (*WalletSweepPackage, error) {
@@ -302,7 +302,7 @@ func CraftSweepAllTx(feeRate chainfee.SatPerKWeight, dustLimit btcutil.Amount,
 	// respects our fee preference and targets all the UTXOs of the wallet.
 	sweepTx, err := createSweepTx(
 		inputsToSweep, txOuts, changePkScript, blockHeight, feeRate,
-		dustLimit, signer,
+		signer,
 	)
 	if err != nil {
 		unlockOutputs()

sweep/walletsweep_test.go

@@ -288,8 +288,8 @@ func TestCraftSweepAllTxCoinSelectFail(t *testing.T) {
 	utxoLocker := newMockOutpointLocker()
 
 	_, err := CraftSweepAllTx(
-		0, 100, 10, nil, nil, coinSelectLocker, utxoSource,
+		0, 10, nil, nil, coinSelectLocker, utxoSource, utxoLocker, nil,
-		utxoLocker, nil, nil, 0,
+		nil, 0,
 	)
 
 	// Since we instructed the coin select locker to fail above, we should
@@ -314,8 +314,8 @@ func TestCraftSweepAllTxUnknownWitnessType(t *testing.T) {
 	utxoLocker := newMockOutpointLocker()
 
 	_, err := CraftSweepAllTx(
-		0, 100, 10, nil, nil, coinSelectLocker, utxoSource,
+		0, 10, nil, nil, coinSelectLocker, utxoSource, utxoLocker, nil,
-		utxoLocker, nil, nil, 0,
+		nil, 0,
 	)
 
 	// Since passed in a p2wsh output, which is unknown, we should fail to
@@ -349,7 +349,7 @@ func TestCraftSweepAllTx(t *testing.T) {
 	utxoLocker := newMockOutpointLocker()
 
 	sweepPkg, err := CraftSweepAllTx(
-		0, 100, 10, nil, deliveryAddr, coinSelectLocker, utxoSource,
+		0, 10, nil, deliveryAddr, coinSelectLocker, utxoSource,
 		utxoLocker, feeEstimator, signer, 0,
 	)
 	if err != nil {

watchtower/wtclient/backup_task_internal_test.go

@@ -300,7 +300,7 @@ func TestBackupTask(t *testing.T) {
 			expSweepCommitRewardLocal      int64                  = 197390
 			expSweepCommitRewardRemote     int64                  = 98437
 			sweepFeeRateNoRewardRemoteDust chainfee.SatPerKWeight = 227500
-			sweepFeeRateRewardRemoteDust   chainfee.SatPerKWeight = 175000
+			sweepFeeRateRewardRemoteDust   chainfee.SatPerKWeight = 175350
 		)
 		if chanType.HasAnchors() {
 			expSweepCommitNoRewardBoth = 299236
@@ -309,8 +309,8 @@ func TestBackupTask(t *testing.T) {
 			expSweepCommitRewardBoth = 296112
 			expSweepCommitRewardLocal = 197389
 			expSweepCommitRewardRemote = 98433
-			sweepFeeRateNoRewardRemoteDust = 225000
+			sweepFeeRateNoRewardRemoteDust = 225400
-			sweepFeeRateRewardRemoteDust = 173750
+			sweepFeeRateRewardRemoteDust = 174100
 		}
 
 		backupTaskTests = append(backupTaskTests, []backupTaskTest{

watchtower/wtpolicy/policy.go

@@ -6,6 +6,7 @@ import (
 
 	"github.com/btcsuite/btcd/wire"
 	"github.com/btcsuite/btcutil"
+	"github.com/lightningnetwork/lnd/input"
 	"github.com/lightningnetwork/lnd/lnwallet"
 	"github.com/lightningnetwork/lnd/lnwallet/chainfee"
 	"github.com/lightningnetwork/lnd/watchtower/blob"
@@ -165,10 +166,9 @@ func (p *Policy) ComputeAltruistOutput(totalAmt btcutil.Amount,
 	sweepAmt := totalAmt - txFee
 
 	// TODO(conner): replace w/ configurable dust limit
-	dustLimit := lnwallet.DefaultDustLimit()
+	// Check that the created outputs won't be dusty. The sweep pkscript is
-
+	// currently a p2wpkh, so we'll use that script's dust limit.
-	// Check that the created outputs won't be dusty.
+	if sweepAmt < lnwallet.DustLimitForSize(input.P2WPKHSize) {
-	if sweepAmt <= dustLimit {
 		return 0, ErrCreatesDust
 	}
 
@@ -199,10 +199,9 @@ func (p *Policy) ComputeRewardOutputs(totalAmt btcutil.Amount,
 	sweepAmt := totalAmt - rewardAmt - txFee
 
 	// TODO(conner): replace w/ configurable dust limit
-	dustLimit := lnwallet.DefaultDustLimit()
+	// Check that the created outputs won't be dusty. The sweep pkscript is
-
+	// currently a p2wpkh, so we'll use that script's dust limit.
-	// Check that the created outputs won't be dusty.
+	if sweepAmt < lnwallet.DustLimitForSize(input.P2WPKHSize) {
-	if sweepAmt <= dustLimit {
 		return 0, 0, ErrCreatesDust
 	}