loopin: public scope for ValidateLoopInContract

Author: hieblmi

client.go

@@ -43,9 +43,13 @@ var (
 	ErrSwapAmountTooHigh = errors.New("swap amount too high")
 
 	// ErrExpiryTooFar is returned when the server proposes an expiry that
-	// is too soon for us.
+	// is too far in the future.
 	ErrExpiryTooFar = errors.New("swap expiry too far")
 
+	// ErrExpiryTooSoon is returned when the server proposes an expiry that
+	// is too soon.
+	ErrExpiryTooSoon = errors.New("swap expiry too soon")
+
 	// ErrInsufficientBalance indicates insufficient confirmed balance to
 	// publish a swap.
 	ErrInsufficientBalance = errors.New("insufficient confirmed balance")

loopin.go

@@ -38,6 +38,10 @@ var (
 	// getting us to lock up our funds to an arbitrary point in the future.
 	MaxLoopInAcceptDelta = int32(1500)
 
+	// MinLoopInExpiryDelta defines the minimum number of remaining blocks
+	// that we accept until htlc expiry path that opens up for us to sweep.
+	MinLoopInExpiryDelta = int32(144)
+
 	// MinLoopInPublishDelta defines the minimum number of remaining blocks
 	// until on-chain htlc expiry required to proceed to publishing the htlc
 	// tx. This value isn't critical, as we could even safely publish the
@@ -248,7 +252,7 @@ func newLoopInSwap(globalCtx context.Context, cfg *swapConfig,
 
 	// Validate if the response parameters are outside our allowed range
 	// preventing us from continuing with a swap.
-	err = validateLoopInContract(currentHeight, swapResp)
+	err = ValidateLoopInContract(currentHeight, swapResp.expiry)
 	if err != nil {
 		return nil, err
 	}
@@ -429,14 +433,20 @@ func resumeLoopInSwap(_ context.Context, cfg *swapConfig,
 	return swap, nil
 }
 
-// validateLoopInContract validates the contract parameters against our request.
-func validateLoopInContract(height int32, response *newLoopInResponse) error {
+// ValidateLoopInContract validates the contract parameters against our
+// configured maximum values.
+func ValidateLoopInContract(height int32, htlcExpiry int32) error {
 	// Verify that we are not forced to publish a htlc that locks up our
 	// funds for too long in case the server doesn't follow through.
-	if response.expiry-height > MaxLoopInAcceptDelta {
+	if htlcExpiry-height > MaxLoopInAcceptDelta {
 		return ErrExpiryTooFar
 	}
 
+	// Ensure that the expiry height is in the future.
+	if htlcExpiry <= height+MinLoopInExpiryDelta {
+		return ErrExpiryTooSoon
+	}
+
 	return nil
 }