Welcome, fellow coder!
This repository contains a code to run a lightning protocol daemon. It’s broken into subdaemons, with the idea being that we can add more layers of separation between different clients and extra barriers to exploits.
It is designed to implement the lightning protocol as specified in various BOLTs.
It’s in C, to encourage alternate implementations. Patches are welcome! You should read our Style Guide.
To read the code, you should start from lightningd.c and hop your way through the ‘~’ comments at the head of each daemon in the suggested order.
Here’s a list of parts, with notes:
- ccan - useful routines from http://ccodearchive.net
- Use make update-ccan to update it.
- Use make update-ccan CCAN_NEW=”mod1 mod2…” to add modules
- Do not edit this! If you want a wrapper, add one to common/utils.h.
- bitcoin/ - bitcoin script, signature and transaction routines.
- Not a complete set, but enough for our purposes.
- external/ - external libraries from other sources
- libbacktrace - library to provide backtraces when things go wrong.
- libsodium - encryption library (should be replaced soon with built-in)
- libwally-core - bitcoin helper library
- secp256k1 - bitcoin curve encryption library within libwally-core
- jsmn - tiny JSON parsing helper
- tools/ - tools for building
- check-bolt.c: check the source code contains correct BOLT quotes (as used by check-source)
- generate-wire.py: generates wire marshal/unmarshal-ing routines for subdaemons and BOLT specs.
- mockup.sh / update-mocks.sh: tools to generate mock functions for unit tests.
- tests/ - blackbox tests (mainly)
- unit tests are in tests/ subdirectories in each other directory.
- doc/ - you are here
- devtools/ - tools for developers
- Generally for decoding our formats.
- contrib/ - python support and other stuff which doesn’t belong :)
- wire/ - basic marshalling/un for messages defined in the BOLTs
- common/ - routines needed by any two or more of the directories below
- cli/ - commandline utility to control lightning daemon.
- lightningd/ - master daemon which controls the subdaemons and passes peer file descriptors between them.
- wallet/ - database code used by master for tracking what’s happening.
- hsmd/ - daemon which looks after the cryptographic secret, and performs commitment signing.
- gossipd/ - daemon to maintain routing information and broadcast gossip.
- connectd/ - daemon to connect to other peers, and receive incoming.
- openingd/ - daemon to open a channel for a single peer, and chat to a peer which doesn’t have any channels/
- channeld/ - daemon to operate a single peer once channel is operating normally.
- closingd/ - daemon to handle mutual closing negotiation with a single peer.
- onchaind/ - daemon to handle a single channel which has had its funding transaction spent.
You can build c-lightning with DEVELOPER=1 to use dev commands listed in
./configure --enable-developer will do that.
You can log console messages with log_info() in lightningd and status_debug()
in other subdaemons.
You can debug crashing subdaemons with the argument
channeld is the subdaemon name. It
gnome-terminal by default with a gdb attached to the
subdaemon when it starts. You can change the terminal used by setting
DEBUG_TERM environment variable, such as
It will also print out (to stderr) the gdb command for manual connection. The
subdaemon will be stopped (it sends itself a SIGSTOP); you’ll need to
continue in gdb.
c-lightning state is persisted in
It is a sqlite database stored in the
lightningd.sqlite3 file, typically
You can run queries against this file like so:
$ sqlite3 ~/.lightning/bitcoin/lightningd.sqlite3 \ "SELECT HEX(prev_out_tx), prev_out_index, status FROM outputs"
Or you can launch into the sqlite3 repl and check things out from there:
$ sqlite3 ~/.lightning/bitcoin/lightningd.sqlite3 SQLite version 3.21.0 2017-10-24 18:55:49 Enter ".help" for usage hints. sqlite> .tables channel_configs invoices peers vars channel_htlcs outputs shachain_known version channels payments shachains sqlite> .schema outputs ...
Some data is stored as raw bytes, use
HEX(column) to pretty print these.
Make sure that clightning is not running when you query the database, as some queries may lock the database and cause crashes.
vars contains global variables used by lightning node.
$ sqlite3 ~/.lightning/bitcoin/lightningd.sqlite3 SQLite version 3.21.0 2017-10-24 18:55:49 Enter ".help" for usage hints. sqlite> .headers on sqlite> select * from vars; name|val next_pay_index|2 bip32_max_index|4 ...
next_pay_indexnext resolved invoice counter that will get assigned.
bip32_max_indexlast wallet derivation counter.
Note: Each time
newaddr command is called,
is increased to the last derivation index.
Each address generated after
bip32_max_index is not included as
Build and Development¶
valgrind and the python dependencies for best results:
sudo apt update sudo apt install valgrind cppcheck shellcheck libsecp256k1-dev libpq-dev pip3 install --upgrade pip pip3 install --user -r requirements.txt
configure for the python dependencies and build using
./configure --enable-developer make -j$(nproc)
Tests are run with:
make check [flags] where the pertinent flags are:
DEVELOPER=[0|1] - developer mode increases test coverage VALGRIND=[0|1] - detects memory leaks during test execution but adds a significant delay PYTEST_PAR=n - runs pytests in parallel
A modern desktop can build and run through all the tests in a couple of minutes with:
make -j12 full-check PYTEST_PAR=24 DEVELOPER=1 VALGRIND=0
PYTEST_PAR accordingly for your hardware.
There are three kinds of tests:
source tests - run by
make check-source, looks for whitespace, header order, and checks formatted quotes from BOLTs if BOLTDIR exists.
unit tests - standalone programs that can be run individually. You can also run all of the unit tests with
make check-units. They are
run-*.cfiles in test/ subdirectories used to test routines inside C source files.
You should insert the lines when implementing a unit test:
/* AUTOGENERATED MOCKS START */
/* AUTOGENERATED MOCKS END */
make update-mockswill automatically generate stub functions which will allow you to link (and conveniently crash if they’re called).
blackbox tests - These tests setup a mini-regtest environment and test lightningd as a whole. They can be run individually:
PYTHONPATH=contrib/pylightning:contrib/pyln-client:contrib/pyln-testing:contrib/pyln-proto py.test -v tests/
You can also append
-k TESTNAMEto run a single test. Environment variables
TIMEOUT=<seconds>can be useful for debugging subdaemons on individual tests.
pylightning tests - will check contrib pylightning for codestyle and run the tests in
Our Travis CI instance (see
.travis.yml) runs all these for each
Additional Environment Variables¶
TEST_CHECK_DBSTMTS=[0|1] - When running blackbox tests, this will load a plugin that logs all compiled and expanded database statements. Note: Only SQLite3. TEST_DB_PROVIDER=[sqlite3|postgres] - Selects the database to use when running blackbox tests. EXPERIMENTAL_DUAL_FUND=[0|1] - Enable dual-funding tests.
Making BOLT Modifications¶
All of code for marshalling/unmarshalling BOLT protocol messages is generated
directly from the spec. These are pegged to the BOLTVERSION, as specified in
Source code analysis¶
An updated version of the NCC source code analysis tool is available at
It can be used to analyze the lightningd source code by running
make clean && make ncc. The output (which is built in parallel with the
binaries) is stored in .nccout files. You can browse it, for instance, with
a command like
There are a few subtleties you should be aware of as you modify deeper parts of the code:
ccan/structeq’s STRUCTEQ_DEF will define safe comparison function foo_eq() for struct foo, failing the build if the structure has implied padding.
command_fail_detailedwill free the
cmdyou pass in. This also means that if you
tal-allocated anything from the
cmd, they will also get freed at those points and will no longer be accessible afterwards.
- When making a structure part of a list, you will instance a
struct list_node. This has to be the first field of the structure, or else
dev-memleakcommand will think your structure has leaked.
The source tree contains CSV files extracted from the v1.0 BOLT
specifications (wire/extracted_peer_wire_csv and
wire/extracted_onion_wire_csv). You can regenerate these by setting
BOLTVERSION appropriately, and running
Feel free to ask questions on the lightning-dev mailing list, or on
#c-lightning on IRC, or email me at email@example.com.