Merge pull request #193 from carlaKC/40-clientpreimagepush

loopout: push preimage to server to speed up off chain claim

Author: carlaKC

client.go

@@ -315,10 +315,7 @@ func (s *Client) Run(ctx context.Context,
 func (s *Client) resumeSwaps(ctx context.Context,
 	loopOutSwaps []*loopdb.LoopOut, loopInSwaps []*loopdb.LoopIn) {
 
-	swapCfg := &swapConfig{
-		lnd:   s.lndServices,
-		store: s.Store,
-	}
+	swapCfg := newSwapConfig(s.lndServices, s.Store, s.Server)
 
 	for _, pend := range loopOutSwaps {
 		if pend.State().State.Type() != loopdb.StateTypePending {
@@ -369,11 +366,7 @@ func (s *Client) LoopOut(globalCtx context.Context,
 
 	// Create a new swap object for this swap.
 	initiationHeight := s.executor.height()
-	swapCfg := &swapConfig{
-		lnd:    s.lndServices,
-		store:  s.Store,
-		server: s.Server,
-	}
+	swapCfg := newSwapConfig(s.lndServices, s.Store, s.Server)
 	swap, err := newLoopOutSwap(
 		globalCtx, swapCfg, initiationHeight, request,
 	)
@@ -486,13 +479,9 @@ func (s *Client) LoopIn(globalCtx context.Context,
 
 	// Create a new swap object for this swap.
 	initiationHeight := s.executor.height()
-	swapCfg := swapConfig{
-		lnd:    s.lndServices,
-		store:  s.Store,
-		server: s.Server,
-	}
+	swapCfg := newSwapConfig(s.lndServices, s.Store, s.Server)
 	swap, err := newLoopInSwap(
-		globalCtx, &swapCfg, initiationHeight, request,
+		globalCtx, swapCfg, initiationHeight, request,
 	)
 	if err != nil {
 		return nil, err

client_test.go

@@ -12,7 +12,9 @@ import (
 	"github.com/lightninglabs/loop/lndclient"
 	"github.com/lightninglabs/loop/loopdb"
 	"github.com/lightninglabs/loop/test"
+	"github.com/lightningnetwork/lnd/lnrpc"
 	"github.com/lightningnetwork/lnd/lntypes"
+	"github.com/stretchr/testify/require"
 )
 
 var (
@@ -261,6 +263,10 @@ func testSuccess(ctx *testContext, amt btcutil.Amount, hash lntypes.Hash,
 
 	ctx.AssertRegisterSpendNtfn(confIntent.PkScript)
 
+	// Assert that a call to track payment was sent, and respond with status
+	// in flight so that our swap will push its preimage to the server.
+	ctx.trackPayment(lnrpc.Payment_IN_FLIGHT)
+
 	// Publish tick.
 	ctx.expiryChan <- testTime
 
@@ -287,6 +293,13 @@ func testSuccess(ctx *testContext, amt btcutil.Amount, hash lntypes.Hash,
 		ctx.T.Fatalf("incorrect preimage")
 	}
 
+	// Since we successfully published our sweep, we expect the preimage to
+	// have been pushed to our mock server.
+	preimage, err := lntypes.MakePreimage(clientPreImage)
+	require.NoError(ctx.T, err)
+
+	ctx.assertPreimagePush(preimage)
+
 	// Simulate server pulling payment.
 	signalSwapPaymentResult(nil)
 

go.mod

@@ -13,6 +13,7 @@ require (
 	github.com/lightninglabs/protobuf-hex-display v1.3.3-0.20191212020323-b444784ce75d
 	github.com/lightningnetwork/lnd v0.10.0-beta.rc6.0.20200603030653-09bb9db78246
 	github.com/lightningnetwork/lnd/queue v1.0.4
+	github.com/stretchr/testify v1.4.0
 	github.com/urfave/cli v1.20.0
 	golang.org/x/net v0.0.0-20191002035440-2ec189313ef0
 	golang.org/x/text v0.3.2 // indirect

go.sum

@@ -1,14 +1,10 @@
 cloud.google.com/go v0.26.0/go.mod h1:aQUYkXzVsufM+DwF1aE+0xfcU+56JwCaLick0ClmMTw=
-git.schwanenlied.me/yawning/bsaes.git v0.0.0-20180720073208-c0276d75487e h1:F2x1bq7RaNCIuqYpswggh1+c1JmwdnkHNC9wy1KDip0=
 git.schwanenlied.me/yawning/bsaes.git v0.0.0-20180720073208-c0276d75487e/go.mod h1:BWqTsj8PgcPriQJGl7el20J/7TuT1d/hSyFDXMEpoEo=
 github.com/BurntSushi/toml v0.3.1 h1:WXkYYl6Yr3qBf1K79EBnL4mak0OimBfB0XUf9Vl28OQ=
 github.com/BurntSushi/toml v0.3.1/go.mod h1:xHWCNGjB5oqiDr8zfno3MHue2Ht5sIBksp03qcyfWMU=
-github.com/NebulousLabs/fastrand v0.0.0-20181203155948-6fb6489aac4e h1:n+DcnTNkQnHlwpsrHoQtkrJIO7CBx029fw6oR4vIob4=
 github.com/NebulousLabs/fastrand v0.0.0-20181203155948-6fb6489aac4e/go.mod h1:Bdzq+51GR4/0DIhaICZEOm+OHvXGwwB2trKZ8B4Y6eQ=
-github.com/NebulousLabs/go-upnp v0.0.0-20180202185039-29b680b06c82 h1:MG93+PZYs9PyEsj/n5/haQu2gK0h4tUtSy9ejtMwWa0=
 github.com/NebulousLabs/go-upnp v0.0.0-20180202185039-29b680b06c82/go.mod h1:GbuBk21JqF+driLX3XtJYNZjGa45YDoa9IqCTzNSfEc=
 github.com/OneOfOne/xxhash v1.2.2/go.mod h1:HSdplMjZKSmBqAxg5vPj2TmRDmfkzw+cTzAElWljhcU=
-github.com/Yawning/aez v0.0.0-20180114000226-4dad034d9db2 h1:2be4ykKKov3M1yISM2E8gnGXZ/N2SsPawfnGiXxaYEU=
 github.com/Yawning/aez v0.0.0-20180114000226-4dad034d9db2/go.mod h1:9pIqrY6SXNL8vjRQE5Hd/OL5GyK/9MrGUWs87z/eFfk=
 github.com/aead/chacha20 v0.0.0-20180709150244-8b13a72661da h1:KjTM2ks9d14ZYCvmHS9iAKVt9AyzRSqNU1qabPih5BY=
 github.com/aead/chacha20 v0.0.0-20180709150244-8b13a72661da/go.mod h1:eHEWzANqSiWQsof+nXEI9bUVUyV6F53Fp89EuCh2EAA=
@@ -23,14 +19,12 @@ github.com/beorn7/perks v1.0.0 h1:HWo1m869IqiPhD389kmkxeTalrjNbbJTC8LXupb+sl0=
 github.com/beorn7/perks v1.0.0/go.mod h1:KWe93zE9D1o94FZ5RNwFwVgaQK1VOXiVxmqh+CedLV8=
 github.com/btcsuite/btcd v0.0.0-20190629003639-c26ffa870fd8/go.mod h1:3J08xEfcugPacsc34/LKRU2yO7YmuT8yt28J8k2+rrI=
 github.com/btcsuite/btcd v0.0.0-20190824003749-130ea5bddde3/go.mod h1:3J08xEfcugPacsc34/LKRU2yO7YmuT8yt28J8k2+rrI=
-github.com/btcsuite/btcd v0.20.1-beta h1:Ik4hyJqN8Jfyv3S4AGBOmyouMsYE3EdYODkMbQjwPGw=
 github.com/btcsuite/btcd v0.20.1-beta/go.mod h1:wVuoA8VJLEcwgqHBwHmzLRazpKxTv13Px/pDuV7OomQ=
 github.com/btcsuite/btcd v0.20.1-beta.0.20200513120220-b470eee47728/go.mod h1:wVuoA8VJLEcwgqHBwHmzLRazpKxTv13Px/pDuV7OomQ=
 github.com/btcsuite/btcd v0.20.1-beta.0.20200515232429-9f0179fd2c46 h1:QyTpiR5nQe94vza2qkvf7Ns8XX2Rjh/vdIhO3RzGj4o=
 github.com/btcsuite/btcd v0.20.1-beta.0.20200515232429-9f0179fd2c46/go.mod h1:Yktc19YNjh/Iz2//CX0vfRTS4IJKM/RKO5YZ9Fn+Pgo=
 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 h1:yJzD/yFppdVCf6ApMkVy8cUxV0XrxdP9rVf6D87/Mng=
 github.com/btcsuite/btcutil v0.0.0-20190425235716-9e5f4b9a998d/go.mod h1:+5NJ2+qvTyV9exUAL/rxXi3DcLg2Ts+ymUAY5y4NvMg=
 github.com/btcsuite/btcutil v1.0.2 h1:9iZ1Terx9fMIOtq1VrwdqfsATL9MC2l8ZrUY6YZ2uts=
 github.com/btcsuite/btcutil v1.0.2/go.mod h1:j9HUFwoQRsZL3V4n+qG+CUnEGHOarIxfC3Le2Yhbcts=
@@ -48,7 +42,6 @@ github.com/btcsuite/btcwallet/walletdb v1.0.0/go.mod h1:bZTy9RyYZh9fLnSua+/CD48T
 github.com/btcsuite/btcwallet/walletdb v1.2.0/go.mod h1:9cwc1Yyg4uvd4ZdfdoMnALji+V9gfWSMfxEdLdR5Vwc=
 github.com/btcsuite/btcwallet/walletdb v1.3.1 h1:lW1Ac3F1jJY4K11P+YQtRNcP5jFk27ASfrV7C6mvRU0=
 github.com/btcsuite/btcwallet/walletdb v1.3.1/go.mod h1:9cwc1Yyg4uvd4ZdfdoMnALji+V9gfWSMfxEdLdR5Vwc=
-github.com/btcsuite/btcwallet/wtxmgr v1.0.0 h1:aIHgViEmZmZfe0tQQqF1xyd2qBqFWxX5vZXkkbjtbeA=
 github.com/btcsuite/btcwallet/wtxmgr v1.0.0/go.mod h1:vc4gBprll6BP0UJ+AIGDaySoc7MdAmZf8kelfNb8CFY=
 github.com/btcsuite/btcwallet/wtxmgr v1.1.1-0.20200515224913-e0e62245ecbe h1:yQbJVYfsKbdqDQNLxd4hhiLSiMkIygefW5mSHMsdKpc=
 github.com/btcsuite/btcwallet/wtxmgr v1.1.1-0.20200515224913-e0e62245ecbe/go.mod h1:OwC0W0HhUszbWdvJvH6xvgabKSJ0lXl11YbmmqF9YXQ=
@@ -135,9 +128,7 @@ github.com/grpc-ecosystem/grpc-gateway v1.12.2 h1:D0EVSTwQoQOyfY35QNSuPJA4jpZRtk
 github.com/grpc-ecosystem/grpc-gateway v1.12.2/go.mod h1:8XEsbTttt/W+VvjtQhLACqCisSPWTxCZ7sBRjU6iH9c=
 github.com/hpcloud/tail v1.0.0 h1:nfCOvKYfkgYP8hkirhJocXT2+zOD8yUNjXaWfTlyFKI=
 github.com/hpcloud/tail v1.0.0/go.mod h1:ab1qPbhIpdTxEkNHXyeSf5vhxWSCs/tWer42PpOxQnU=
-github.com/jackpal/gateway v1.0.5 h1:qzXWUJfuMdlLMtt0a3Dgt+xkWQiA5itDEITVJtuSwMc=
 github.com/jackpal/gateway v1.0.5/go.mod h1:lTpwd4ACLXmpyiCTRtfiNyVnUmqT9RivzCDQetPfnjA=
-github.com/jackpal/go-nat-pmp v0.0.0-20170405195558-28a68d0c24ad h1:heFfj7z0pGsNCekUlsFhO2jstxO4b5iQ665LjwM5mDc=
 github.com/jackpal/go-nat-pmp v0.0.0-20170405195558-28a68d0c24ad/go.mod h1:QPH045xvCAeXUZOxsnwmrtiCoxIr9eob+4orBN1SBKc=
 github.com/jedib0t/go-pretty v4.3.0+incompatible/go.mod h1:XemHduiw8R651AF9Pt4FwCTKeG3oo7hrHJAoznj9nag=
 github.com/jessevdk/go-flags v0.0.0-20141203071132-1679536dcc89/go.mod h1:4FA24M0QyGHXBuZZK/XkWh8h0e1EYbRYJSGM75WSRxI=
@@ -178,7 +169,6 @@ github.com/kr/text v0.1.0 h1:45sCR5RtlFHMR4UwH9sdQ5TC8v0qDQCHnXt+kaKSTVE=
 github.com/kr/text v0.1.0/go.mod h1:4Jbv+DJW3UT/LiOwJeYQe1efqtUx/iVham/4vfdArNI=
 github.com/lightninglabs/gozmq v0.0.0-20191113021534-d20a764486bf h1:HZKvJUHlcXI/f/O0Avg7t8sqkPo78HFzjmeYFl6DPnc=
 github.com/lightninglabs/gozmq v0.0.0-20191113021534-d20a764486bf/go.mod h1:vxmQPeIQxPf6Jf9rM8R+B4rKBqLA2AjttNxkFBL2Plk=
-github.com/lightninglabs/neutrino v0.11.0 h1:lPpYFCtsfJX2W5zI4pWycPmbbBdr7zU+BafYdLoD6k0=
 github.com/lightninglabs/neutrino v0.11.0/go.mod h1:CuhF0iuzg9Sp2HO6ZgXgayviFTn1QHdSTJlMncK80wg=
 github.com/lightninglabs/neutrino v0.11.1-0.20200316235139-bffc52e8f200 h1:j4iZ1XlUAPQmW6oSzMcJGILYsRHNs+4O3Gk+2Ms5Dww=
 github.com/lightninglabs/neutrino v0.11.1-0.20200316235139-bffc52e8f200/go.mod h1:MlZmoKa7CJP3eR1s5yB7Rm5aSyadpKkxqAwLQmog7N0=
@@ -191,7 +181,6 @@ github.com/lightningnetwork/lnd v0.10.0-beta.rc6.0.20200603030653-09bb9db78246/g
 github.com/lightningnetwork/lnd/cert v1.0.2/go.mod h1:fmtemlSMf5t4hsQmcprSoOykypAPp+9c+0d0iqTScMo=
 github.com/lightningnetwork/lnd/clock v1.0.0 h1:U9uknV7DwBsNUzc+x11tx1bPvoXiEYcJ9wrIemRibKE=
 github.com/lightningnetwork/lnd/clock v1.0.0/go.mod h1:KnQudQ6w0IAMZi1SgvecLZQZ43ra2vpDNj7H/aasemg=
-github.com/lightningnetwork/lnd/queue v1.0.1 h1:jzJKcTy3Nj5lQrooJ3aaw9Lau3I0IwvQR5sqtjdv2R0=
 github.com/lightningnetwork/lnd/queue v1.0.1/go.mod h1:vaQwexir73flPW43Mrm7JOgJHmcEFBWWSl9HlyASoms=
 github.com/lightningnetwork/lnd/queue v1.0.4 h1:8Dq3vxAFSACPy+pKN88oPFhuCpCoAAChPBwa4BJxH4k=
 github.com/lightningnetwork/lnd/queue v1.0.4/go.mod h1:YTkTVZCxz8tAYreH27EO3s8572ODumWrNdYW2E/YKxg=
@@ -256,7 +245,6 @@ github.com/stretchr/testify v1.4.0/go.mod h1:j7eGeouHqKxXV5pUuKE4zz7dFj8WfuZ+81P
 github.com/tidwall/pretty v1.0.0/go.mod h1:XNkn88O1ChpSDQmQeStsy+sBenx6DDtFZJxhVysOjyk=
 github.com/tmc/grpc-websocket-proxy v0.0.0-20190109142713-0ad062ec5ee5 h1:LnC5Kc/wtumK+WB441p7ynQJzVuNRJiqddSIE3IlSEQ=
 github.com/tmc/grpc-websocket-proxy v0.0.0-20190109142713-0ad062ec5ee5/go.mod h1:ncp9v5uamzpCO7NfCPTXjqaC+bZgJeR0sMTm6dMHP7U=
-github.com/tv42/zbase32 v0.0.0-20160707012821-501572607d02 h1:tcJ6OjwOMvExLlzrAVZute09ocAGa7KqOON60++Gz4E=
 github.com/tv42/zbase32 v0.0.0-20160707012821-501572607d02/go.mod h1:tHlrkM198S068ZqfrO6S8HsoJq2bF3ETfTL+kt4tInY=
 github.com/urfave/cli v1.18.0/go.mod h1:70zkFmudgCuE/ngEzBv17Jvp/497gISqfk5gWijbERA=
 github.com/urfave/cli v1.20.0 h1:fDqGv3UG/4jbVl/QkFwEdddtEDjh/5Ov6X+0B/3bPaw=
@@ -280,7 +268,6 @@ golang.org/x/crypto v0.0.0-20180904163835-0709b304e793/go.mod h1:6SG95UA2DQfeDnf
 golang.org/x/crypto v0.0.0-20190211182817-74369b46fc67/go.mod h1:6SG95UA2DQfeDnfUPMdvaQW0Q7yPrPDi9nlGo2tz2b4=
 golang.org/x/crypto v0.0.0-20190308221718-c2843e01d9a2/go.mod h1:djNgcEr1/C05ACkg1iLfiJU5Ep61QUkGW8qpdssI0+w=
 golang.org/x/crypto v0.0.0-20190510104115-cbcb75029529/go.mod h1:yigFU9vqHzYiE8UmvKecakEJjdnWj3jj499lnFckfCI=
-golang.org/x/crypto v0.0.0-20200115085410-6d4e4cb37c7d h1:2+ZP7EfsZV7Vvmx3TIqSlSzATMkTAKqM14YGFPoSKjI=
 golang.org/x/crypto v0.0.0-20200115085410-6d4e4cb37c7d/go.mod h1:LzIPMQfyMNhhGPhUkYOs5KpL4U8rLKemX1yGLhDgUto=
 golang.org/x/crypto v0.0.0-20200510223506-06a226fb4e37 h1:cg5LA/zNPRzIXIWSCxQW10Rvpy94aQh3LT/ShoCpkHw=
 golang.org/x/crypto v0.0.0-20200510223506-06a226fb4e37/go.mod h1:LzIPMQfyMNhhGPhUkYOs5KpL4U8rLKemX1yGLhDgUto=
@@ -320,7 +307,6 @@ golang.org/x/sys v0.0.0-20181116152217-5ac8a444bdc5/go.mod h1:STP8DvDyc/dI5b8T5h
 golang.org/x/sys v0.0.0-20190209173611-3b5209105503/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
 golang.org/x/sys v0.0.0-20190215142949-d0b11bdaac8a/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
 golang.org/x/sys v0.0.0-20190412213103-97732733099d/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
-golang.org/x/sys v0.0.0-20190904154756-749cb33beabd h1:DBH9mDw0zluJT/R+nGuV3jWFWLFaHyYZWD4tOT+cjn0=
 golang.org/x/sys v0.0.0-20190904154756-749cb33beabd/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
 golang.org/x/sys v0.0.0-20200116001909-b77594299b42 h1:vEOn+mP2zCOVzKckCZy6YsCtDblrpj/w7B9nxGNELpg=
 golang.org/x/sys v0.0.0-20200116001909-b77594299b42/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
@@ -373,7 +359,6 @@ gopkg.in/tomb.v1 v1.0.0-20141024135613-dd632973f1e7 h1:uRGJdciOHaEIrze2W8Q3AKkep
 gopkg.in/tomb.v1 v1.0.0-20141024135613-dd632973f1e7/go.mod h1:dt/ZhP58zS4L8KSrWDmTeBkI65Dw0HsyUHuEVlX15mw=
 gopkg.in/yaml.v2 v2.0.0-20170812160011-eb3733d160e7/go.mod h1:JAlM8MvJe8wmxCU4Bli9HhUf9+ttbYbLASfIpnQbh74=
 gopkg.in/yaml.v2 v2.2.1/go.mod h1:hI93XBmqTisBFMUTm0b8Fm+jr3Dg1NNxqwp+5A1VGuI=
-gopkg.in/yaml.v2 v2.2.2 h1:ZCJp+EgiOT7lHqUV2J862kp8Qj64Jo6az82+3Td9dZw=
 gopkg.in/yaml.v2 v2.2.2/go.mod h1:hI93XBmqTisBFMUTm0b8Fm+jr3Dg1NNxqwp+5A1VGuI=
 gopkg.in/yaml.v2 v2.2.3 h1:fvjTMHxHEw/mxHbtzPi3JCcKXQRAnQTBRo6YCJSVHKI=
 gopkg.in/yaml.v2 v2.2.3/go.mod h1:hI93XBmqTisBFMUTm0b8Fm+jr3Dg1NNxqwp+5A1VGuI=

lndclient/router_client.go

@@ -5,6 +5,7 @@ import (
 	"crypto/rand"
 	"encoding/hex"
 	"fmt"
+	"io"
 	"time"
 
 	"github.com/btcsuite/btcutil"
@@ -225,6 +226,8 @@ func (r *routerClient) TrackPayment(ctx context.Context,
 
 // trackPayment takes an update stream from either a SendPayment or a
 // TrackPayment rpc call and converts it into distinct update and error streams.
+// Once the payment reaches a final state, the status and error channels will
+// be closed to signal that we are finished sending into them.
 func (r *routerClient) trackPayment(ctx context.Context,
 	stream routerrpc.Router_TrackPaymentV2Client) (chan PaymentStatus,
 	chan error, error) {
@@ -235,6 +238,17 @@ func (r *routerClient) trackPayment(ctx context.Context,
 		for {
 			payment, err := stream.Recv()
 			if err != nil {
+				// If we get an EOF error, the payment has
+				// reached a final state and the server is
+				// finished sending us updates. We close both
+				// channels to signal that we are done sending
+				// values on them and return.
+				if err == io.EOF {
+					close(statusChan)
+					close(errorChan)
+					return
+				}
+
 				switch status.Convert(err).Code() {
 
 				// NotFound is only expected as a response to

loopin_test.go

@@ -32,11 +32,7 @@ func TestLoopInSuccess(t *testing.T) {
 
 	height := int32(600)
 
-	cfg := &swapConfig{
-		lnd:    &ctx.lnd.LndServices,
-		store:  ctx.store,
-		server: ctx.server,
-	}
+	cfg := newSwapConfig(&ctx.lnd.LndServices, ctx.store, ctx.server)
 
 	swap, err := newLoopInSwap(
 		context.Background(), cfg,
@@ -151,11 +147,7 @@ func testLoopInTimeout(t *testing.T,
 
 	height := int32(600)
 
-	cfg := &swapConfig{
-		lnd:    &ctx.lnd.LndServices,
-		store:  ctx.store,
-		server: ctx.server,
-	}
+	cfg := newSwapConfig(&ctx.lnd.LndServices, ctx.store, ctx.server)
 
 	req := testLoopInRequest
 	if externalValue != 0 {
@@ -282,12 +274,7 @@ func testLoopInResume(t *testing.T, state loopdb.SwapState, expired bool) {
 	defer test.Guard(t)()
 
 	ctx := newLoopInTestContext(t)
-
-	cfg := &swapConfig{
-		lnd:    &ctx.lnd.LndServices,
-		store:  ctx.store,
-		server: ctx.server,
-	}
+	cfg := newSwapConfig(&ctx.lnd.LndServices, ctx.store, ctx.server)
 
 	senderKey := [33]byte{4}
 	receiverKey := [33]byte{5}

loopout.go

@@ -706,6 +706,20 @@ func (s *loopOutSwap) waitForHtlcSpendConfirmed(globalCtx context.Context,
 		return nil, fmt.Errorf("register spend ntfn: %v", err)
 	}
 
+	// Track our payment status so that we can detect whether our off chain
+	// htlc is settled. We track this information to determine whether it is
+	// necessary to continue trying to push our preimage to the server.
+	trackChan, trackErrChan, err := s.lnd.Router.TrackPayment(
+		ctx, s.hash,
+	)
+	if err != nil {
+		return nil, fmt.Errorf("track payment: %v", err)
+	}
+
+	// paymentComplete tracks whether our payment is complete, and is used
+	// to decide whether we need to push our preimage to the server.
+	var paymentComplete bool
+
 	timerChan := s.timerFactory(republishDelay)
 	for {
 		select {
@@ -719,6 +733,45 @@ func (s *loopOutSwap) waitForHtlcSpendConfirmed(globalCtx context.Context,
 		case err := <-spendErr:
 			return nil, err
 
+		// Receive status updates for our payment so that we can detect
+		// whether we've successfully pushed our preimage.
+		case status, ok := <-trackChan:
+			// If our channel has been closed, indicating that the
+			// server is finished providing updates because the
+			// payment has reached a terminal state, we replace
+			// the closed channel with nil so that we will no longer
+			// listen on it.
+			if !ok {
+				trackChan = nil
+				continue
+			}
+
+			if status.State == lnrpc.Payment_SUCCEEDED {
+				s.log.Infof("Off chain payment succeeded")
+
+				paymentComplete = true
+			}
+
+		// If we receive a track payment error that indicates that the
+		// server stream is complete, we ignore it because we want to
+		// continue this loop beyond the completion of the payment.
+		case err, ok := <-trackErrChan:
+			// If our channel has been closed, indicating that the
+			// server is finished providing updates because the
+			// payment has reached a terminal state, we replace
+			// the closed channel with nil so that we will no longer
+			// listen on it.
+			if !ok {
+				trackErrChan = nil
+				continue
+			}
+
+			// Otherwise, if we receive a non-nil error, we return
+			// it.
+			if err != nil {
+				return nil, err
+			}
+
 		// New block arrived, update height and restart the republish
 		// timer.
 		case notification := <-s.blockEpochChan:
@@ -733,13 +786,39 @@ func (s *loopOutSwap) waitForHtlcSpendConfirmed(globalCtx context.Context,
 				return nil, err
 			}
 
+			// If our off chain payment is not yet complete, we
+			// try to push our preimage to the server.
+			if !paymentComplete {
+				s.pushPreimage(ctx)
+			}
+
 		// Context canceled.
 		case <-globalCtx.Done():
 			return nil, globalCtx.Err()
 		}
 	}
 }
 
+// pushPreimage pushes our preimage to the server if we have already revealed
+// our preimage on chain with a sweep attempt.
+func (s *loopOutSwap) pushPreimage(ctx context.Context) {
+	// If we have not yet revealed our preimage through a sweep, we do not
+	// push the preimage because we may choose to never sweep if fees are
+	// too high.
+	if s.state != loopdb.StatePreimageRevealed {
+		return
+	}
+
+	s.log.Infof("Pushing preimage to server")
+
+	// Push the preimage to the server, just log server errors since we rely
+	// on our payment state rather than the server response to judge the
+	// outcome of our preimage push.
+	if err := s.server.PushLoopOutPreimage(ctx, s.Preimage); err != nil {
+		s.log.Warnf("Could not push preimage: %v", err)
+	}
+}
+
 // sweep tries to sweep the given htlc to a destination address. It takes into
 // account the max miner fee and marks the preimage as revealed when it
 // published the tx.