If the mantissas of two non-native amounts differ by less than 10, then
subtracting them leaves a result of zero. This can cause situations
where `a>b`, yet `a-b == 0`.
One consequence of this is unfunded offers were incorrectly left in
order books. The code would check if the offer would be
consumed (`amount in offer > amount needed`), assume it wouldn't be,
yet when `amount needed` was subtracted from `amount in offer` the
result was zero and the offer was unfunded. This unfunded offer
incorrectly remained on the order book.
This patch fixes this bug.
Payment channels permit off-ledger checkpoints of XRP payments flowing
in a single direction. A channel sequesters the owner's XRP in its own
ledger entry. The owner can authorize the recipient to claim up to a
give balance by giving the receiver a signed message (off-ledger). The
recipient can use this signed message to claim any unpaid balance while
the channel remains open. The owner can top off the line as needed. If
the channel has not paid out all its funds, the owner must wait out a
delay to close the channel to give the recipient a chance to supply any
claims. The recipient can close the channel at any time. Any transaction
that touches the channel after the expiration time will close the
channel. The total amount paid increases monotonically as newer claims
are issued. When the channel is closed any remaining balance is returned
to the owner. Channels are intended to permit intermittent off-ledger
settlement of ILP trust lines as balances get substantial. For
bidirectional channels, a payment channel can be used in each direction.
The Ripple protocol represent transfer rates and trust line
qualities as fractions of one billion. For example, a transfer
rate of 1% is represented as 1010000000.
Previously, such rates where represented either as std::uint32_t
or std::uint64_t. Other, nominally related types, also used an
integral representation and could be unintentionally substituted.
The new Rate class addresses this by providing a simple, type
safe alternative which also helps make the code self-documenting
since arithmetic operations now can be clearly understood to
involve the scaling of an amount by a rate.
The Owner count could decrease while evaluating a strand, causing
different behavior in forward passes and reverses passes. The fix treats
a decreased owner count like a deferred credit.
In some situations, deferred credits could cause an XRP balance to be
calculated as negative, triggering some asserts.
When XRP is used as a bridge currency, a path could be falsely marked as
dry. This happens when the XRP/XXX offer recursively checks the XXX/XRP
offer and the XXX/XRP offer could not satisfy the request in a single
call.
With a single strand and limit quality the old payment code incorrectly
computed with multiquailty set to true. This could cause the total
quality to go below the requested quality even if there was liquidity
available above the requested quality value.
Before this change, the deferred credits algorithm took the current
balance and subtracted the recorded credits. Conceptually, this is the
same as taking the original balance, adding all the credits,
subtracting all the debits, and subtracting all the credits. The new
algorithm records the original balance and subtracts the debits. This
prevents errors that occur when the original balance and the recorded
credits have large differences in magnitude.
Additionally, XRP credits were recorded incorrectly in the deferred
credits table (the line was between the sender and receiver, rather than
the root account).
Replace Journal public data members with member function accessors
in order to make Journal lighter weight. The change makes a
Journal cheaper to pass by value.
Also add missing stream checks (e.g., calls to JLOG) to avoid
text processing that ultimately will not be stored in the log.
Add a new algorithm for finding the liquidity in a payment path. There
is still a reverse and forward pass, but the forward pass starts at the
limiting step rather than the payment source. This insures the limiting
step is completely consumed rather than potentially leaving a 'dust'
amount in the forward pass.
Each step in a payment is either a book step, a direct step (account to
account step), or an xrp endpoint. Each step in the existing
implementation is a triple, where each element in the triple is either
an account of a book, for a total of eight step types.
Since accounts are considered in pairs, rather than triples, transfer
fees are handled differently. In V1 of payments, in the payment path
A -> gw ->B, if A redeems to gw, and gw issues to B, a transfer fee is
changed. In the new code, a transfer fee is changed even if A issues to
gw.
Since a non-default STAccount is now guaranteed to always be
160 bits, it was possible to reduce the number of methods that
it provides.
In the process of narrowing the STAccount interface it became
reasonable to remove some methods that duplicated functionality.
A few classes offered both a value() and a getValue() method.
The getValue() method is removed from those classes.
The first few transactions are added to the open ledger at
the base fee (ie. 10 drops). Once enough transactions are
added, the required fee will jump dramatically. If additional
transactions are added, the fee will grow exponentially.
Transactions that don't have a high enough fee to be applied to
the ledger are added to the queue in order from highest fee to
lowest. Whenever a new ledger is accepted as validated, transactions
are first applied from the queue to the open ledger in fee order
until either all transactions are applied or the fee again jumps
too high for the remaining transactions.
Current implementation is restricted to one transaction in the
queue per account. Some groundwork has been laid to expand in
the future.
Note that this fee logic escalates independently of the load-based
fee logic (ie. LoadFeeTrack). Submitted transactions must meet
the load fee to be considered for the queue, and must meet both
fees to be put into open ledger.
The server's open ledger is now an instance of the OpenView
class, managed by an instance of the OpenLedger class. This
should improve the performance of operations on open ledgers
because they are no longer Ledger/SHAMap operation.
* Consider ledgers incompatible based on last valid ledger
* Test against even ledgers not acquired yet
* Don't validate an incompatible ledger
* Don't switch to an incompatible ledger
* Protect against an unreasonably small quorum
This non-production config section allows features to be enabled
by listing their text descriptions, one line each, in the config
section titled "features".
NOTE: Feature names with leading or trailing whitespace, or
containing an equals sign ('=') are not supported.
* Remove ltCURRENT
* Change getOwnerInfo
* Use ReadView in TransactionSign
* Change AcceptedLedger and ProposedTransaction to use ReadView
* Change RPC::accounts
An instance of Rules provides information on the tx
processing rules in a particular ledger.
* OpenView allows rules to be set on construction.
Conflicts:
src/ripple/unity/ledger.cpp
