e9035f867a
3add23454624c4c79c9eebc060b6fbed4e3131a7 ui: show header pre-synchronization progress (Pieter Wuille)
738421c50f2dbd7395b50a5dbdf6168b07435e62 Emit NotifyHeaderTip signals for pre-synchronization progress (Pieter Wuille)
376086fc5a187f5b2ab3a0d1202ed4e6c22bdb50 Make validation interface capable of signalling header presync (Pieter Wuille)
93eae27031a65b4156df49015ae45b2b541b4e5a Test large reorgs with headerssync logic (Suhas Daftuar)
355547334f7d08640ee1fa291227356d61145d1a Track headers presync progress and log it (Pieter Wuille)
03712dddfbb9fe0dc7a2ead53c65106189f5c803 Expose HeadersSyncState::m_current_height in getpeerinfo() (Suhas Daftuar)
150a5486db50ff77c91765392149000029c8a309 Test headers sync using minchainwork threshold (Suhas Daftuar)
0b6aa826b53470c9cc8ef4a153fa710dce80882f Add unit test for HeadersSyncState (Suhas Daftuar)
83c6a0c5249c4ecbd11f7828c84a50fb473faba3 Reduce spurious messages during headers sync (Suhas Daftuar)
ed6cddd98e32263fc116a4380af6d66da20da990 Require callers of AcceptBlockHeader() to perform anti-dos checks (Suhas Daftuar)
551a8d957c4c44afbd0d608fcdf7c6a4352babce Utilize anti-DoS headers download strategy (Suhas Daftuar)
ed470940cddbeb40425960d51cefeec4948febe4 Add functions to construct locators without CChain (Pieter Wuille)
84852bb6bb3579e475ce78fe729fd125ddbc715f Add bitdeque, an std::deque<bool> analogue that does bit packing. (Pieter Wuille)
1d4cfa4272cf2c8b980cc8762c1ff2220d3e8d51 Add function to validate difficulty changes (Suhas Daftuar)
Pull request description:
New nodes starting up for the first time lack protection against DoS from low-difficulty headers. While checkpoints serve as our protection against headers that fork from the main chain below the known checkpointed values, this protection only applies to nodes that have been able to download the honest chain to the checkpointed heights.
We can protect all nodes from DoS from low-difficulty headers by adopting a different strategy: before we commit to storing a header in permanent storage, first verify that the header is part of a chain that has sufficiently high work (either `nMinimumChainWork`, or something comparable to our tip). This means that we will download headers from a given peer twice: once to verify the work on the chain, and a second time when permanently storing the headers.
The p2p protocol doesn't provide an easy way for us to ensure that we receive the same headers during the second download of peer's headers chain. To ensure that a peer doesn't (say) give us the main chain in phase 1 to trick us into permanently storing an alternate, low-work chain in phase 2, we store commitments to the headers during our first download, which we validate in the second download.
Some parameters must be chosen for commitment size/frequency in phase 1, and validation of commitments in phase 2. In this PR, those parameters are chosen to both (a) minimize the per-peer memory usage that an attacker could utilize, and (b) bound the expected amount of permanent memory that an attacker could get us to use to be well-below the memory growth that we'd get from the honest chain (where we expect 1 new block header every 10 minutes).
After this PR, we should be able to remove checkpoints from our code, which is a nice philosophical change for us to make as well, as there has been confusion over the years about the role checkpoints play in Bitcoin's consensus algorithm.
Thanks to Pieter Wuille for collaborating on this design.
ACKs for top commit:
Sjors:
re-tACK 3add23454624c4c79c9eebc060b6fbed4e3131a7
mzumsande:
re-ACK 3add23454624c4c79c9eebc060b6fbed4e3131a7
sipa:
re-ACK 3add23454624c4c79c9eebc060b6fbed4e3131a7
glozow:
ACK 3add234546
Tree-SHA512: e7789d65f62f72141b8899eb4a2fb3d0621278394d2d7adaa004675250118f89a4e4cb42777fe56649d744ec445ad95141e10f6def65f0a58b7b35b2e654a875
Unit tests
The sources in this directory are unit test cases. Boost includes a unit testing framework, and since Bitcoin Core already uses Boost, it makes sense to simply use this framework rather than require developers to configure some other framework (we want as few impediments to creating unit tests as possible).
The build system is set up to compile an executable called test_bitcoin
that runs all of the unit tests. The main source file for the test library is found in
util/setup_common.cpp.
Compiling/running unit tests
Unit tests will be automatically compiled if dependencies were met in ./configure
and tests weren't explicitly disabled.
After configuring, they can be run with make check.
To run the unit tests manually, launch src/test/test_bitcoin. To recompile
after a test file was modified, run make and then run the test again. If you
modify a non-test file, use make -C src/test to recompile only what's needed
to run the unit tests.
To add more unit tests, add BOOST_AUTO_TEST_CASE functions to the existing
.cpp files in the test/ directory or add new .cpp files that
implement new BOOST_AUTO_TEST_SUITE sections.
To run the GUI unit tests manually, launch src/qt/test/test_bitcoin-qt
To add more GUI unit tests, add them to the src/qt/test/ directory and
the src/qt/test/test_main.cpp file.
Running individual tests
test_bitcoin accepts the command line arguments from the boost framework.
For example, to run just the getarg_tests suite of tests:
test_bitcoin --log_level=all --run_test=getarg_tests
log_level controls the verbosity of the test framework, which logs when a
test case is entered, for example. test_bitcoin also accepts the command
line arguments accepted by bitcoind. Use -- to separate both types of
arguments:
test_bitcoin --log_level=all --run_test=getarg_tests -- -printtoconsole=1
The -printtoconsole=1 after the two dashes redirects the debug log, which
would normally go to a file in the test datadir
(BasicTestingSetup::m_path_root), to the standard terminal output.
... or to run just the doubledash test:
test_bitcoin --run_test=getarg_tests/doubledash
Run test_bitcoin --help for the full list.
Adding test cases
To add a new unit test file to our test suite you need
to add the file to src/Makefile.test.include. The pattern is to create
one test file for each class or source file for which you want to create
unit tests. The file naming convention is <source_filename>_tests.cpp
and such files should wrap their tests in a test suite
called <source_filename>_tests. For an example of this pattern,
see uint256_tests.cpp.
Logging and debugging in unit tests
make check will write to a log file foo_tests.cpp.log and display this file
on failure. For running individual tests verbosely, refer to the section
above.
To write to logs from unit tests you need to use specific message methods
provided by Boost. The simplest is BOOST_TEST_MESSAGE.
For debugging you can launch the test_bitcoin executable with gdb or lldb and
start debugging, just like you would with any other program:
gdb src/test/test_bitcoin
Segmentation faults
If you hit a segmentation fault during a test run, you can diagnose where the fault
is happening by running gdb ./src/test/test_bitcoin and then using the bt command
within gdb.
Another tool that can be used to resolve segmentation faults is valgrind.
If for whatever reason you want to produce a core dump file for this fault, you can do
that as well. By default, the boost test runner will intercept system errors and not
produce a core file. To bypass this, add --catch_system_errors=no to the
test_bitcoin arguments and ensure that your ulimits are set properly (e.g. ulimit -c unlimited).
Running the tests and hitting a segmentation fault should now produce a file called core
(on Linux platforms, the file name will likely depend on the contents of
/proc/sys/kernel/core_pattern).
You can then explore the core dump using
gdb src/test/test_bitcoin core
(gbd) bt # produce a backtrace for where a segfault occurred