Looking for things to hack on?

Cleanups

Remove our specific libsecp256k1 in secp256k1/ and use the installed one.

Minor improvements

Make json_get_params fail if unknown parameters are specified by user.
Print backtrace in log_crash
When unpacking a packet, reject any with an unknown odd-numbered field as per BOLT #2.
Limit total number of peers in new_peer, or at least in peer_connected_in.
logging: add IO logging for peers.
Add history RPC command which shows all prior commit txs.
Improve getpeers to show status of peers when connecting, DNS lookups etc.
Add pings to protocol
- Timeout a peer if they don't respond in a given time (eg. 2 pings)

Testing:

Add more unit tests in bitcoin/test and daemon/test
Test more scenarios with daemon/test/test.sh, and split it up.
Implement compile-time crypto-free mode
- Implement canned conversation files for fuzz testing (eg AFL).
Write canned input/output test cases for various conversations, and include them in a form suitable for other implementations to test.

Major improvements:

(MAJOR) Implement onion
- (MAJOR) Implement failure message encryption

Other

Grep for other FIXMEs and fix one :)
Look on https://github.com/ElementsProject/lightning/issues

Happy hacking!
Rusty.