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Fix underflow issue for XRP:

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In some cases multiplying or dividing STAmounts gave incorrect results.

This happens when:

1) The result should be rounded up
2) The STAmount represents a native value (XRP)
3) The rounded up value was less than one drop

In this case, the result was zero, instead of one drop. This could
cause funded offers to be removed as unfunded.
This commit is contained in:
seelabs
2016-02-25 10:07:32 -05:00
parent 3605bf1f60
commit d8ee487c19
4 changed files with 148 additions and 9 deletions
Download Patch File Download Diff File Expand all files Collapse all files

105
src/ripple/app/tests/Offer.test.cpp
View File

@@ -181,6 +181,110 @@ public:
}
}
void testXRPTinyPayment ()
{
testcase ("XRP Tiny payments");
// Regression test for tiny xrp payments
// In some cases, when the payment code calculates
// the amount of xrp needed as input to an xrp->iou offer
// it would incorrectly round the amount to zero (even when
// round-up was set to true).
// The bug would cause funded offers to be incorrectly removed
// because the code thought they were unfunded.
// The conditions to trigger the bug are:
// 1) When we calculate the amount of input xrp needed for an offer from
// xrp->iou, the amount is less than 1 drop (after rounding up the float
// representation).
// 2) There is another offer in the same book with a quality sufficiently bad that
// when calculating the input amount needed the amount is not set to zero.
using namespace jtx;
using namespace std::chrono_literals;
auto const alice = Account ("alice");
auto const bob = Account ("bob");
auto const carol = Account ("carol");
auto const dan = Account ("dan");
auto const erin = Account ("erin");
auto const gw = Account ("gw");
auto const USD = gw["USD"];
for (auto withFix : {false, true})
{
Env env (*this);
auto closeTime = [&]
{
auto const delta =
100 * env.closed ()->info ().closeTimeResolution;
if (withFix)
return STAmountSO::soTime2 + delta;
else
return STAmountSO::soTime2 - delta;
}();
auto offerCount = [&env](jtx::Account const& account)
{
auto count = 0;
forEachItem (*env.current (), account,
[&](std::shared_ptr<SLE const> const& sle)
{
if (sle->getType () == ltOFFER)
++count;
});
return count;
};
env.fund (XRP (10000), alice, bob, carol, dan, erin, gw);
env.trust (USD (1000), alice, bob, carol, dan, erin);
env (pay (gw, carol, USD (0.99999)));
env (pay (gw, dan, USD (1)));
env (pay (gw, erin, USD (1)));
// Carol doen't quite have enough funds for this offer
// The amount left after this offer is taken will cause
// STAmount to incorrectly round to zero when the next offer
// (at a good quality) is considered. (when the
// stAmountCalcSwitchover2 patch is inactive)
env (offer (carol, drops (1), USD (1)));
// Offer at a quality poor enough so when the input xrp is calculated
// in the reverse pass, the amount is not zero.
env (offer (dan, XRP (100), USD (1)));
env.close (closeTime);
// This is the funded offer that will be incorrectly removed.
// It is considered after the offer from carol, which leaves a
// tiny amount left to pay. When calculating the amount of xrp
// needed for this offer, it will incorrectly compute zero in both
// the forward and reverse passes (when the stAmountCalcSwitchover2 is
// inactive.)
env (offer (erin, drops (1), USD (1)));
{
env (pay (alice, bob, USD (1)), path (~USD),
sendmax (XRP (102)),
txflags (tfNoRippleDirect | tfPartialPayment));
expect (offerCount (carol) == 0);
expect (offerCount (dan) == 1);
if (!withFix)
{
// funded offer was removed
expect (offerCount (erin) == 0);
env.require (balance ("erin", USD (1)));
}
else
{
// offer was correctly consumed. There is stil some
// liquidity left on that offer.
expect (offerCount (erin) == 1);
env.require (balance ("erin", USD (0.99999)));
}
}
}
}
void testEnforceNoRipple ()
{
testcase ("Enforce No Ripple");
@@ -696,6 +800,7 @@ public:
testCanceledOffer ();
testRmFundedOffer ();
testTinyPayment ();
testXRPTinyPayment ();
testEnforceNoRipple ();
testInsufficientReserve ();
testFillModes ();

8
src/ripple/protocol/STAmount.h
View File

@@ -402,6 +402,7 @@ inline bool isXRP(STAmount const& amount)
}
extern LocalValue<bool> stAmountCalcSwitchover;
extern LocalValue<bool> stAmountCalcSwitchover2;
/** RAII class to set and restore the STAmount calc switchover.*/
class STAmountSO
@@ -409,20 +410,27 @@ class STAmountSO
public:
explicit STAmountSO(NetClock::time_point const closeTime)
: saved_(*stAmountCalcSwitchover)
, saved2_(*stAmountCalcSwitchover2)
{
*stAmountCalcSwitchover = closeTime > soTime;
*stAmountCalcSwitchover2 = closeTime > soTime2;
}
~STAmountSO()
{
*stAmountCalcSwitchover = saved_;
*stAmountCalcSwitchover2 = saved2_;
}
// Mon Dec 28, 2015 10:00:00am PST
static NetClock::time_point const soTime;
// Mon Mar 28, 2015 10:00:00am PST
static NetClock::time_point const soTime2;
private:
bool saved_;
bool saved2_;
};
} // ripple

37
src/ripple/protocol/impl/STAmount.cpp
View File

@@ -36,9 +36,14 @@
namespace ripple {
LocalValue<bool> stAmountCalcSwitchover(true);
LocalValue<bool> stAmountCalcSwitchover2(true);
using namespace std::chrono_literals;
const NetClock::time_point STAmountSO::soTime{504640800s};
// Fri Feb 26, 2016 9:00:00pm PST
const NetClock::time_point STAmountSO::soTime2{509864400s};
static const std::uint64_t tenTo14 = 100000000000000ull;
static const std::uint64_t tenTo14m1 = tenTo14 - 1;
static const std::uint64_t tenTo17 = tenTo14 * 1000;
@@ -1199,9 +1204,18 @@ mulRound (STAmount const& v1, STAmount const& v2, Issue const& issue,
// Control when bugfixes that require switchover dates are enabled
if (roundUp && !resultNegative && !result && *stAmountCalcSwitchover)
{
// return the smallest value above zero
amount = STAmount::cMinValue;
offset = STAmount::cMinOffset;
if (isXRP(issue) && *stAmountCalcSwitchover2)
{
// return the smallest value above zero
amount = 1;
offset = 0;
}
else
{
// return the smallest value above zero
amount = STAmount::cMinValue;
offset = STAmount::cMinOffset;
}
return STAmount(issue, amount, offset, resultNegative);
}
return result;
@@ -1259,10 +1273,19 @@ divRound (STAmount const& num, STAmount const& den,
// Control when bugfixes that require switchover dates are enabled
if (roundUp && !resultNegative && !result && *stAmountCalcSwitchover)
{
// return the smallest value above zero
amount = STAmount::cMinValue;
offset = STAmount::cMinOffset;
return STAmount (issue, amount, offset, resultNegative);
if (isXRP(issue) && *stAmountCalcSwitchover2)
{
// return the smallest value above zero
amount = 1;
offset = 0;
}
else
{
// return the smallest value above zero
amount = STAmount::cMinValue;
offset = STAmount::cMinOffset;
}
return STAmount(issue, amount, offset, resultNegative);
}
return result;
}

5
test/discrepancy-test.coffee
View File

@@ -94,7 +94,10 @@ suite 'Discrepancy test', ->
suite 'RIPD 304', ->
get_context = server_setup_teardown({server_opts: {ledger_file: 'ledger-7145315.json'}})
test 'B1A305038D43BCDF3EA1D096E6A0ACC5FB0ECAE0C8F5D3A54AD76A2AA1E20EC4', (done) ->
# Skip - the new rounding code makes this legacy test produce different
# results. Skip this test for now, as new tests which exercise the payment
# engine and the new rounding code are coming soon.
test.skip 'B1A305038D43BCDF3EA1D096E6A0ACC5FB0ECAE0C8F5D3A54AD76A2AA1E20EC4', (done) ->
{remote} = get_context()
txns_to_submit = [