multi: replace DefaultDustLimit with script-specific DustLimitForSize

This commit updates call-sites to use the proper dust limits for
various script types. This also updates the default dust limit used
in the funding flow to be 354 satoshis instead of 573 satoshis.

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
 	}

funding/manager.go

@@ -3114,19 +3114,10 @@ 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,
-		msg.PushAmt, msg.ChainHash, peerKey.SerializeCompressed(),
-		ourDustLimit, msg.MinConfs)
+		"min_confs=%v)", localAmt, msg.SubtractFees, msg.PushAmt,
+		msg.ChainHash, peerKey.SerializeCompressed(), msg.MinConfs)
 
 	// We set the channel flags to indicate whether we want this channel to
 	// be announced to the network.
@@ -3300,6 +3291,12 @@ 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 +3310,7 @@ 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/txrules v1.0.0
+	github.com/btcsuite/btcwallet/wallet/txauthor v1.1.0
+	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 v1.0.2-0.20210803004036-eebed51155ec/go.mod h1:VufDts7bd/zs3GV13f/lXc/0lXrPnvxD/NvmpG/FEKU=
-github.com/btcsuite/btcwallet/wallet/txrules v1.0.0 h1:2VsfS0sBedcM5KmDzRMT3+b6xobqWveZGvjb+jFez5w=
+github.com/btcsuite/btcwallet/wallet/txauthor v1.1.0 h1:8pO0pvPX1rFRfRiol4oV6kX7dY5y4chPwhfVwUfvwtk=
+github.com/btcsuite/btcwallet/wallet/txauthor v1.1.0/go.mod h1:ktYuJyumYtwG+QQ832Q+kqvxWJRAei3Nqs5qhSn4nww=
 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)