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fix: greedy forwarding #392

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merged 2 commits into from
Oct 30, 2017
Merged

fix: greedy forwarding #392

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af5f298
fix: greedy forwarding
Oct 22, 2017
886dbdd
chore: address review comments
Oct 25, 2017
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25 changes: 18 additions & 7 deletions src/lib/quoter.js
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Original file line number Diff line number Diff line change
Expand Up @@ -142,27 +142,38 @@ class Quoter {
}

/**
* Note that this function, like most of the ilp-connector code, uses the terms
* source, destination, and final, to refer to what we would normally call
* incoming, outgoing, and destination.
*
* @param {IlpAddress} sourceLedger
* @param {IlpAddress} destination
* @param {Amount} sourceAmount
* @param {Amount} finalAmount
* @returns {Object}
*/
* findBestPathForSourceAmount (sourceLedger, destination, sourceAmount) {
const quote = yield this.quoteBySourceAmount({
* findBestPathForFinalAmount (sourceLedger, destination, finalAmount) {
// This obtains a quote from incoming/"source" ledger to destination/"final" ledger:
const quote = yield this.quoteByDestinationAmount({
sourceAccount: sourceLedger,
destinationAccount: destination,
sourceAmount: sourceAmount,
destinationAmount: finalAmount,
destinationHoldDuration: 10 // dummy value, only used if a remote quote is needed
})
if (!quote) return
if (!quote.hop) {
quote.hop = destination
}

// Now we isolate the head hop (incoming/"source" ledger to outgoing/"destination" ledger):
const headRoute = this.localTables.getLocalPairRoute(sourceLedger, quote.route.nextLedger)
const headCurve = headRoute.curve

return {
isFinal: !quote.hop,
destinationLedger: quote.route.nextLedger,
destinationCreditAccount: quote.hop,
destinationAmount: headCurve.amountAt(sourceAmount).toString(),
finalAmount: quote.liquidityCurve.amountAt(sourceAmount).toString()
sourceAmount: quote.sourceAmount,
destinationAmount: headCurve.amountAt(quote.sourceAmount).toString(),
finalAmount: quote.liquidityCurve.amountAt(quote.sourceAmount).toString()
}
}
}
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27 changes: 10 additions & 17 deletions src/lib/route-builder.js
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Expand Up @@ -176,8 +176,8 @@ class RouteBuilder {
ilpPacket.account, ilpPacket.amount)

const sourceLedger = sourceTransfer.ledger
const nextHop = yield this.quoter.findBestPathForSourceAmount(
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Is findBestPathForSourceAmount still used or was this the only call? If its the latter, the function should be removed.

sourceLedger, ilpPacket.account, sourceTransfer.amount)
const nextHop = yield this.quoter.findBestPathForFinalAmount(
sourceLedger, ilpPacket.account, ilpPacket.amount)
if (!nextHop) {
log.info('could not find quote for source transfer: ' + JSON.stringify(sourceTransfer))
throw new IncomingTransferError(ilpErrors.F02_Unreachable({
Expand All @@ -186,22 +186,15 @@ class RouteBuilder {
}
this._verifyLedgerIsConnected(nextHop.destinationLedger)

// Check if this connector can authorize the final transfer.
if (nextHop.isFinal) {
// Verify expectedFinalAmount ≤ actualFinalAmount
// As long as the fxSpread > slippage, the connector won't lose money.
const expectedFinalAmount = new BigNumber(ilpPacket.amount).times(1 - this.slippage)
if (expectedFinalAmount.greaterThan(nextHop.finalAmount)) {
throw new IncomingTransferError(ilpErrors.R01_Insufficient_Source_Amount({
message: 'Payment rate does not match the rate currently offered'
}))
}
// TODO: Verify atomic mode notaries are trusted
// TODO: Verify expiry is acceptable

nextHop.destinationCreditAccount = ilpPacket.account
nextHop.destinationAmount = ilpPacket.amount
// As long as the fxSpread > slippage, the connector won't lose money.
const expectedSourceAmount = new BigNumber(nextHop.sourceAmount).times(1 - this.slippage)
if (expectedSourceAmount.greaterThan(sourceTransfer.amount)) {
throw new IncomingTransferError(ilpErrors.R01_Insufficient_Source_Amount({
message: 'Payment rate does not match the rate currently offered'
}))
}
// TODO: Verify atomic mode notaries are trusted
// TODO: Verify expiry is acceptable

const noteToSelf = {
source_transfer_ledger: sourceTransfer.ledger,
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2 changes: 1 addition & 1 deletion test/routeBuilderSpec.js
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Expand Up @@ -194,7 +194,7 @@ describe('RouteBuilder', function () {
ledger: ledgerA,
direction: 'incoming',
account: aliceA,
amount: '98', // 98 ⇒ 49 = 50 * (1 - slippage)
amount: '99', // 99 * (1 - slippage) = 100 ⇒ 50
ilp: ilpPacket
})
assert.equal(destinationTransfer.ilp, ilpPacket)
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