Fill out TODO.md into a useful list (mainly by grepping for FIXMEs).

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

HACKING.md

@@ -5,7 +5,7 @@ This repository contains a prototype for testing the lightning protocols.
 Getting Started
 ---------------
 It's in C, to encourage alternate implementations.  It uses the Linux
-coding style.  Patches are welcome!  Just look for FIXME if you want
+coding style.  Patches are welcome!  See the TODO.md file if you want
 ideas.
 
 To read the code, you'll probably need to understand ccan/tal: it's a

TODO.md

@@ -1,7 +1,69 @@
-Looking for things to hack on?  Great, here's a partial list:
+# Looking for things to hack on? #
 
-* Wean off openssl's -lcrypto: use libsodium for all RNG, gmp for base58.
+I've marked things as simple if you want something easy to work on!
-* Grep for FIXME and fix one :)
+
-* Look on https://github.com/ElementsProject/lightning/issues
+## Cleanups ##
+
+* Wean off openssl's -lcrypto
+  * (simple) use libsodium for all RNG
+  * (simple) use libbase58
+
+* Remove our specific libsecp256k1 in secp256k1/ and use the installed one.
+  * Implement `sig_valid`, using `secp256k1_ecdsa_signature_normalize`
+  * Use `secp256k1_ecdsa_signature_parse_compact`/`_serialize_compact` in `signature_to_proto`
+
+## Minor improvements ##
+
+* Optimize `bitcoind_poll_transactions` not to list all transactions every time
+* Make `json_get_params` fail if unknown parameters are specified by user.
+* Print backtrace in `log_crash`
+* Support locktime in blocks in `accept_pkt_open`, `accept_pkt_htlc_add`, `commit_tx_depth`
+* Get bitcoind's idea of time for `commit_tx_depth`, not our wall clock.
+* When unpacking a packet, reject any with an unknown odd-numbered field as per BOLT #2.
+* Provide details (string) when a command fails because state() returns CMD_FAIL
+* logging: add `log_struct()` for common structs.
+* `state_single` should only kill the specific peer when it enters an error state.
+* Limit total number of peers in `new_peer`, or at least in `peer_connected_in`.
+* logging: add IO logging for peers.
+* implement on-chain HTLCs correctly (`peer_watch_our_htlc_outputs` etc in peer.c).
+* 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)
+* Add timers to drop peer if we approach timeout for HTLCs and they're still
+uncommitted to closing it (see BOLT #2 "Risks With HTLC Timeouts").
+
+## Testing: ##
+
+* Add more unit tests in bitcoin/test.
+* Test more scenarios with daemon/test/test.sh
+* 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: ##
+
+* Use dynamic fee calculation for initial commitment fee rate.
+  * (MAJOR) Implement fee renegotiation acceptance.
+  * (MAJOR) Implement fee renegotiation as fee rate changes.
+
+* Don't fail funding if fees insufficient, fall back as per BOLT #2.
+
+* (MAJOR) Do proper close, still allowing ongoing HTLCs to resolve.
+
+* (MAJOR) Use segregated witness for all transactions.
+* (MAJOR) Implement reconnection.
+* Save preimages in shachain.
+  * (MAJOR) Implement persistence.
+* (MAJOR) Implement onion
+  * (MAJOR) Implement routing
+  * (MAJOR) Implement failure messages
+
+## Other ##
+
+* Grep for other FIXMEs and fix one :)
+* Look on https://github.com/ElementsProject/lightning/issues
+
+Happy hacking!<br>
+Rusty.