This commit is the first stage of several that are planned to convert
the blockchain package into a concurrent safe package that will
ultimately allow support for multi-peer download and concurrent chain
processing. The goal is to update btcd proper after each step so it can
take advantage of the enhancements as they are developed.
In addition to the aforementioned benefit, this staged approach has been
chosen since it is absolutely critical to maintain consensus.
Separating the changes into several stages makes it easier for reviewers
to logically follow what is happening and therefore helps prevent
consensus bugs. Naturally there are significant automated tests to help
prevent consensus issues as well.
The main focus of this stage is to convert the blockchain package to use
the new database interface and implement the chain-related functionality
which it no longer handles. It also aims to improve efficiency in
various areas by making use of the new database and chain capabilities.
The following is an overview of the chain changes:
- Update to use the new database interface
- Add chain-related functionality that the old database used to handle
- Main chain structure and state
- Transaction spend tracking
- Implement a new pruned unspent transaction output (utxo) set
- Provides efficient direct access to the unspent transaction outputs
- Uses a domain specific compression algorithm that understands the
standard transaction scripts in order to significantly compress them
- Removes reliance on the transaction index and paves the way toward
eventually enabling block pruning
- Modify the New function to accept a Config struct instead of
inidividual parameters
- Replace the old TxStore type with a new UtxoViewpoint type that makes
use of the new pruned utxo set
- Convert code to treat the new UtxoViewpoint as a rolling view that is
used between connects and disconnects to improve efficiency
- Make best chain state always set when the chain instance is created
- Remove now unnecessary logic for dealing with unset best state
- Make all exported functions concurrent safe
- Currently using a single chain state lock as it provides a straight
forward and easy to review path forward however this can be improved
with more fine grained locking
- Optimize various cases where full blocks were being loaded when only
the header is needed to help reduce the I/O load
- Add the ability for callers to get a snapshot of the current best
chain stats in a concurrent safe fashion
- Does not block callers while new blocks are being processed
- Make error messages that reference transaction outputs consistently
use <transaction hash>:<output index>
- Introduce a new AssertError type an convert internal consistency
checks to use it
- Update tests and examples to reflect the changes
- Add a full suite of tests to ensure correct functionality of the new
code
The following is an overview of the btcd changes:
- Update to use the new database and chain interfaces
- Temporarily remove all code related to the transaction index
- Temporarily remove all code related to the address index
- Convert all code that uses transaction stores to use the new utxo
view
- Rework several calls that required the block manager for safe
concurrency to use the chain package directly now that it is
concurrent safe
- Change all calls to obtain the best hash to use the new best state
snapshot capability from the chain package
- Remove workaround for limits on fetching height ranges since the new
database interface no longer imposes them
- Correct the gettxout RPC handler to return the best chain hash as
opposed the hash the txout was found in
- Optimize various RPC handlers:
- Change several of the RPC handlers to use the new chain snapshot
capability to avoid needlessly loading data
- Update several handlers to use new functionality to avoid accessing
the block manager so they are able to return the data without
blocking when the server is busy processing blocks
- Update non-verbose getblock to avoid deserialization and
serialization overhead
- Update getblockheader to request the block height directly from
chain and only load the header
- Update getdifficulty to use the new cached data from chain
- Update getmininginfo to use the new cached data from chain
- Update non-verbose getrawtransaction to avoid deserialization and
serialization overhead
- Update gettxout to use the new utxo store versus loading
full transactions using the transaction index
The following is an overview of the utility changes:
- Update addblock to use the new database and chain interfaces
- Update findcheckpoint to use the new database and chain interfaces
- Remove the dropafter utility which is no longer supported
NOTE: The transaction index and address index will be reimplemented in
another commit.
Contains the following upstream commits:
- ef9c50be57
- eb882f39f8
In addition to merging the fixes in the commits, this also fixes a few
more misspellings that were introduced in the new Decred code.
Corrected or added many comments.
Update test code to follow format go vet wants.
The code doesn't pass the checks 100% yet. That will come in a later
commit but these all seemed related so I'd rather get them in now.
See https://github.com/bitcoin/bips/blob/master/bip-0065.mediawiki for
more information.
This commit mimics Bitcoin Core commit bc60b2b4b401f0adff5b8b9678903ff8feb5867b
and includes additional tests from Bitcoin Core commit
cb54d17355864fa08826d6511a0d7692b21ef2c9
Introduce an ECDSA signature verification into btcd in order to
mitigate a certain DoS attack and as a performance optimization.
The benefits of SigCache are two fold. Firstly, usage of SigCache
mitigates a DoS attack wherein an attacker causes a victim's client to
hang due to worst-case behavior triggered while processing attacker
crafted invalid transactions. A detailed description of the mitigated
DoS attack can be found here: https://bitslog.wordpress.com/2013/01/23/fixed-bitcoin-vulnerability-explanation-why-the-signature-cache-is-a-dos-protection/
Secondly, usage of the SigCache introduces a signature verification
optimization which speeds up the validation of transactions within a
block, if they've already been seen and verified within the mempool.
The server itself manages the sigCache instance. The blockManager and
txMempool respectively now receive pointers to the created sigCache
instance. All read (sig triplet existence) operations on the sigCache
will not block unless a separate goroutine is adding an entry (writing)
to the sigCache. GetBlockTemplate generation now also utilizes the
sigCache in order to avoid unnecessarily double checking signatures
when generating a template after previously accepting a txn to the
mempool. Consequently, the CPU miner now also employs the same
optimization.
The maximum number of entries for the sigCache has been introduced as a
config parameter in order to allow users to configure the amount of
memory consumed by this new additional caching.
This commit moves all code related to standard scripts into a separate
file named standard.go as well as the associated tests into
standard_test.go. Since the code in address.go and address_test.go is
only related to standard scripts, it has been combined into the new
files and the old files deleted.
The intent here is to make it clear that the code in standard.go is not
related to consensus.
This commit implements a new type, named scriptNum, for handling all
numeric values used in scripts and converts the code over to make use of
it. This is being done for a few of reasons.
First, the consensus rules for handling numeric values in the scripts
require special handling with subtle semantics. By encapsulating those
details into a type specifically dedicated to that purpose, it
simplifies the code and generally helps prevent improper usage.
Second, the new type is quite a bit more efficient than big.Ints which
are designed to be arbitrarily large and thus involve a lot of heap
allocations and additional multi-precision bookkeeping. Because this
new type is based on an int64, it allows the numbers to be stack
allocated thereby eliminating a lot of GC and also eliminates the extra
multi-precision arithmetic bookkeeping.
The use of an int64 is possible because the consensus rules dictate that
when data is interpreted as a number, it is limited to an int32 even
though results outside of this range are allowed so long as they are not
interpreted as integers again themselves. Thus, the maximum possible
result comes from multiplying a max int32 by itself which safely fits
into an int64 and can then still appropriately provide the serialization
of the larger number as required by consensus.
Finally, it more closely resembles the implementation used by Bitcoin
Core and thus makes is easier to compare the behavior between the two
implementations.
This commit also includes a full suite of tests with 100% coverage of
the semantics of the new type.
This commit contains a lot of cleanup on the txscript code to make it
more consistent with the code throughout the rest of the project. It
doesn't change any operational logic.
The following is an overview of the changes:
- Add a significant number of comments throughout in order to better
explain what the code is doing
- Fix several comment typos
- Move a couple of constants only used by the engine to engine.go
- Move a variable only used by the engine to engine.go
- Fix a couple of format specifiers in the test prints
- Reorder functions so they're defined before/closer to use
- Make the code lint clean with the exception of the opcode definitions
This commit moves the opcode execution logic from the opcode type to the
engine type because execution of an opcode modifies the engine state
(primarily the main and alternate data stacks) as opposed to the state
of the opcode. Making the engine the receiver more clearly indicates
this fact.
This commit unexports the Stack type since it is only intended to be
used internally during script execution. Further, the engine exposes
the {G,S}etStack and {G,S}etAltStack functions which return the items as
a slice of byte slices ([][]byte) for caller access while stepping.
This commit improves the way the conditional execution stack is handled in
a few ways.
First, the current execution state is now pushed onto the end of the slice
rather than the front of it. This has been done because it results in
fewer allocations and is therefore more efficient.
Second, the need for allocating and setting an initial true in the
conditional stack has been eliminated. The vast majority of scripts don't
contain any conditionals, so there is no reason to allocate a slice when
it isn't needed.
Third, a new function has been added to the engine to determine if the
current conditional branch is executing named isBranchExecuting which
handles the fact the conditional execution stack can now be empty and
improves the readability of the code.
Finally, it removes a couple of TODOs which I have verified do not apply.
Rather than storing a separate bool for whether or not each flag is set in
every script engine instance, store the flags and check if the relevant
flag is set from each specific location.
This reduces the memory needed by each script engine instance and means
future flags will not require new fields.
This commit renames the Script type to Engine to better reflect its
purpose. It also renames the NewScript function to NewEngine to match.
This is being done because name Script for the engine is confusing since
it implies it is an actual script rather than the execution environment
for the script. It also paves the way for eventually supplying a
ParsedScript type which will be less likely to be confused with the
execution environment.
While moving the code, some additional variable names and comments have
been updated to better match the style used throughout the rest of the
code base. In addition, an attempt has been made to use consistent naming
of the engine as 'vm' instead of using different variables names as it was
previously.
Finally, the relevant engine code has been moved into a new file named
engine.go and related tests moved to engine_test.go.
