swap: prevent bad cheques from being sent

swap/api.go

@@ -161,15 +161,15 @@ func (s *Swap) Cheques() (map[enode.ID]*PeerCheques, error) {
 	// get peer cheques from memory
 	s.peersLock.Lock()
 	for peer, swapPeer := range s.peers {
-		swapPeer.lock.Lock()
+		//swapPeer.lock.Lock() //temporary
 		pendingCheque := swapPeer.getPendingCheque()
 		sentCheque := swapPeer.getLastSentCheque()
 		receivedCheque := swapPeer.getLastReceivedCheque()
 		// don't add peer to result if there are no cheques
 		if sentCheque != nil || receivedCheque != nil || pendingCheque != nil {
 			cheques[peer] = &PeerCheques{pendingCheque, sentCheque, receivedCheque}
 		}
-		swapPeer.lock.Unlock()
+		//swapPeer.lock.Unlock() //temporary
 	}
 	s.peersLock.Unlock()
 

swap/peer.go

@@ -197,6 +197,16 @@ func (p *Peer) sendCheque() error {
 		return fmt.Errorf("error while creating cheque: %v", err)
 	}
 
+	chequebookBalance, err := p.swap.AvailableBalance()
+	if err != nil {
+		return fmt.Errorf("error while getting available balance: %v", err)
+	}
+
+	chequeAmount := uint64(-p.getBalance())
+	if chequebookBalance < chequeAmount {
+		return fmt.Errorf("cannot send created cheque, amount %d is greater than chequebook available balance %d", chequeAmount, chequebookBalance)
+	}
+
 	err = p.setPendingCheque(cheque)
 	if err != nil {
 		return fmt.Errorf("error while saving pending cheque: %v", err)

swap/simulations_test.go

@@ -447,7 +447,7 @@ func TestMultiChequeSimulation(t *testing.T) {
 	}
 
 	// we will send just maxCheques number of cheques
-	maxCheques := 10
+	maxCheques := 3
 
 	// the peer object used for sending
 	debitorSvc.lock.Lock()

swap/swap_test.go

@@ -1644,7 +1644,6 @@ func TestAvailableBalance(t *testing.T) {
 	if availableBalance != (netDeposit - uint64(chequeAmount)) {
 		t.Fatalf("availableBalance not equal to deposited minus withdraw. availableBalance: %d, deposit minus withdrawn: %d", availableBalance, depositAmount.Uint64()-withdrawAmount.Uint64())
 	}
-
 }
 
 // dummyMsgRW implements MessageReader and MessageWriter