core-lightning/lightningd/channel_control.c

#include <bitcoin/pubkey.h>
#include <bitcoin/script.h>
#include <channeld/gen_channel_wire.h>
#include <common/memleak.h>
#include <common/timeout.h>
#include <common/utils.h>
#include <common/wire_error.h>
#include <errno.h>
#include <gossipd/gossip_constants.h>
#include <hsmd/gen_hsm_client_wire.h>
#include <inttypes.h>
#include <lightningd/channel_control.h>
#include <lightningd/closing_control.h>
#include <lightningd/hsm_control.h>
#include <lightningd/lightningd.h>
#include <lightningd/log.h>
#include <lightningd/peer_control.h>
#include <lightningd/subd.h>
#include <wire/wire_sync.h>

static void lockin_complete(struct channel *channel)
{
	/* We set this once we're locked in. */
	assert(channel->scid);
	/* We set this once they're locked in. */
	assert(channel->remote_funding_locked);
	channel_set_state(channel, CHANNELD_AWAITING_LOCKIN, CHANNELD_NORMAL);
}

/* We were informed by channeld that it announced the channel and sent
 * an update, so we can now start sending a node_announcement. The
 * first step is to build the provisional announcement and ask the HSM
 * to sign it. */

static void peer_got_funding_locked(struct channel *channel, const u8 *msg)
{
	struct pubkey next_per_commitment_point;

	if (!fromwire_channel_got_funding_locked(msg,
						 &next_per_commitment_point)) {
		channel_internal_error(channel,
				       "bad channel_got_funding_locked %s",
				       tal_hex(channel, msg));
		return;
	}

	if (channel->remote_funding_locked) {
		channel_internal_error(channel,
				       "channel_got_funding_locked twice");
		return;
	}
	update_per_commit_point(channel, &next_per_commitment_point);

	log_debug(channel->log, "Got funding_locked");
	channel->remote_funding_locked = true;

	if (channel->scid)
		lockin_complete(channel);
}

static void peer_got_shutdown(struct channel *channel, const u8 *msg)
{
	u8 *scriptpubkey;
	struct lightningd *ld = channel->peer->ld;

	if (!fromwire_channel_got_shutdown(channel, msg, &scriptpubkey)) {
		channel_internal_error(channel, "bad channel_got_shutdown %s",
				       tal_hex(msg, msg));
		return;
	}

	/* FIXME: Add to spec that we must allow repeated shutdown! */
	tal_free(channel->remote_shutdown_scriptpubkey);
	channel->remote_shutdown_scriptpubkey = scriptpubkey;

	/* BOLT #2:
	 *
	 * 1. `OP_DUP` `OP_HASH160` `20` 20-bytes `OP_EQUALVERIFY` `OP_CHECKSIG`
	 *   (pay to pubkey hash), OR
	 * 2. `OP_HASH160` `20` 20-bytes `OP_EQUAL` (pay to script hash), OR
	 * 3. `OP_0` `20` 20-bytes (version 0 pay to witness pubkey), OR
	 * 4. `OP_0` `32` 32-bytes (version 0 pay to witness script hash)
	 *
	 * A receiving node:
	 *...
	 *  - if the `scriptpubkey` is not in one of the above forms:
	 *    - SHOULD fail the connection.
	 */
	if (!is_p2pkh(scriptpubkey, NULL) && !is_p2sh(scriptpubkey, NULL)
	    && !is_p2wpkh(scriptpubkey, NULL) && !is_p2wsh(scriptpubkey, NULL)) {
		channel_fail_permanent(channel, "Bad shutdown scriptpubkey %s",
				       tal_hex(channel, scriptpubkey));
		return;
	}

	/* If we weren't already shutting down, we are now */
	if (channel->state != CHANNELD_SHUTTING_DOWN)
		channel_set_state(channel,
				  channel->state, CHANNELD_SHUTTING_DOWN);

	/* TODO(cdecker) Selectively save updated fields to DB */
	wallet_channel_save(ld->wallet, channel);
}

static void channel_fail_fallen_behind(struct channel *channel, const u8 *msg)
{
	struct pubkey per_commitment_point;

	if (!fromwire_channel_fail_fallen_behind(msg, &per_commitment_point)) {
		channel_internal_error(channel,
				       "bad channel_fail_fallen_behind %s",
				       tal_hex(tmpctx, msg));
		return;
	}

	channel->future_per_commitment_point
		= tal_dup(channel, struct pubkey, &per_commitment_point);

	/* Peer sees this, so send a generic msg about unilateral close. */
	channel_fail_permanent(channel,	"Awaiting unilateral close");
}

static void peer_start_closingd_after_shutdown(struct channel *channel,
					       const u8 *msg,
					       const int *fds)
{
	struct crypto_state cs;

	/* We expect 2 fds. */
	assert(tal_count(fds) == 2);

	if (!fromwire_channel_shutdown_complete(msg, &cs)) {
		channel_internal_error(channel, "bad shutdown_complete: %s",
				       tal_hex(msg, msg));
		return;
	}

	/* This sets channel->owner, closes down channeld. */
	peer_start_closingd(channel, &cs, fds[0], fds[1], false, NULL);
	channel_set_state(channel, CHANNELD_SHUTTING_DOWN, CLOSINGD_SIGEXCHANGE);
}

static unsigned channel_msg(struct subd *sd, const u8 *msg, const int *fds)
{
	enum channel_wire_type t = fromwire_peektype(msg);

	switch (t) {
	case WIRE_CHANNEL_SENDING_COMMITSIG:
		peer_sending_commitsig(sd->channel, msg);
		break;
	case WIRE_CHANNEL_GOT_COMMITSIG:
		peer_got_commitsig(sd->channel, msg);
		break;
	case WIRE_CHANNEL_GOT_REVOKE:
		peer_got_revoke(sd->channel, msg);
		break;
	case WIRE_CHANNEL_GOT_FUNDING_LOCKED:
		peer_got_funding_locked(sd->channel, msg);
		break;
	case WIRE_CHANNEL_GOT_SHUTDOWN:
		peer_got_shutdown(sd->channel, msg);
		break;
	case WIRE_CHANNEL_SHUTDOWN_COMPLETE:
		/* We expect 2 fds. */
		if (!fds)
			return 2;
		peer_start_closingd_after_shutdown(sd->channel, msg, fds);
		break;
	case WIRE_CHANNEL_FAIL_FALLEN_BEHIND:
		channel_fail_fallen_behind(sd->channel, msg);
		break;

	/* And we never get these from channeld. */
	case WIRE_CHANNEL_INIT:
	case WIRE_CHANNEL_FUNDING_LOCKED:
	case WIRE_CHANNEL_OFFER_HTLC:
	case WIRE_CHANNEL_FULFILL_HTLC:
	case WIRE_CHANNEL_FAIL_HTLC:
	case WIRE_CHANNEL_GOT_COMMITSIG_REPLY:
	case WIRE_CHANNEL_GOT_REVOKE_REPLY:
	case WIRE_CHANNEL_SENDING_COMMITSIG_REPLY:
	case WIRE_CHANNEL_SEND_SHUTDOWN:
	case WIRE_CHANNEL_DEV_REENABLE_COMMIT:
	case WIRE_CHANNEL_FEERATES:
	/* Replies go to requests. */
	case WIRE_CHANNEL_OFFER_HTLC_REPLY:
	case WIRE_CHANNEL_DEV_REENABLE_COMMIT_REPLY:
		break;
	}

	return 0;
}

void peer_start_channeld(struct channel *channel,
			 const struct crypto_state *cs,
			 int peer_fd, int gossip_fd,
			 const u8 *funding_signed,
			 bool reconnected)
{
	u8 *initmsg;
	int hsmfd;
	struct added_htlc *htlcs;
	enum htlc_state *htlc_states;
	struct fulfilled_htlc *fulfilled_htlcs;
	enum side *fulfilled_sides;
	const struct failed_htlc **failed_htlcs;
	enum side *failed_sides;
	struct short_channel_id funding_channel_id;
	u64 num_revocations;
	struct lightningd *ld = channel->peer->ld;
	const struct config *cfg = &ld->config;
	bool reached_announce_depth;
	struct secret last_remote_per_commit_secret;

	hsmfd = hsm_get_client_fd(ld, &channel->peer->id,
				  channel->dbid,
				  HSM_CAP_SIGN_GOSSIP
				  | HSM_CAP_ECDH
				  | HSM_CAP_COMMITMENT_POINT
				  | HSM_CAP_SIGN_REMOTE_TX);

	channel_set_owner(channel,
			  new_channel_subd(ld,
					   "lightning_channeld", channel,
					   channel->log, true,
					   channel_wire_type_name,
					   channel_msg,
					   channel_errmsg,
					   channel_set_billboard,
					   take(&peer_fd),
					   take(&gossip_fd),
					   take(&hsmfd), NULL),
			  false);

	if (!channel->owner) {
		log_unusual(channel->log, "Could not subdaemon channel: %s",
			    strerror(errno));
		channel_fail_transient(channel, "Failed to subdaemon channel");
		return;
	}

	peer_htlcs(tmpctx, channel, &htlcs, &htlc_states, &fulfilled_htlcs,
		   &fulfilled_sides, &failed_htlcs, &failed_sides);

	if (channel->scid) {
		funding_channel_id = *channel->scid;
		reached_announce_depth
			= (short_channel_id_blocknum(&funding_channel_id)
			   + ANNOUNCE_MIN_DEPTH <= get_block_height(ld->topology));
		log_debug(channel->log, "Already have funding locked in%s",
			  reached_announce_depth
			  ? " (and ready to announce)" : "");
	} else {
		log_debug(channel->log, "Waiting for funding confirmations");
		memset(&funding_channel_id, 0, sizeof(funding_channel_id));
		reached_announce_depth = false;
	}

	num_revocations = revocations_received(&channel->their_shachain.chain);

	/* BOLT #2:
	 *
 	 *   - if it supports `option_data_loss_protect`:
	 *     - if `next_remote_revocation_number` equals 0:
	 *       - MUST set `your_last_per_commitment_secret` to all zeroes
	 *     - otherwise:
	 *       - MUST set `your_last_per_commitment_secret` to the last
	 *         `per_commitment_secret` it received
	 */
	if (num_revocations == 0)
		memset(&last_remote_per_commit_secret, 0,
		       sizeof(last_remote_per_commit_secret));
	else if (!shachain_get_secret(&channel->their_shachain.chain,
				      num_revocations-1,
				      &last_remote_per_commit_secret)) {
		channel_fail_permanent(channel,
				       "Could not get revocation secret %"PRIu64,
				       num_revocations-1);
		return;
	}

	/* Warn once. */
	if (ld->config.ignore_fee_limits)
		log_debug(channel->log, "Ignoring fee limits!");

	initmsg = towire_channel_init(tmpctx,
				      &get_chainparams(ld)->genesis_blockhash,
				      &channel->funding_txid,
				      channel->funding_outnum,
				      channel->funding_satoshi,
				      &channel->our_config,
				      &channel->channel_info.their_config,
				      channel->channel_info.feerate_per_kw,
				      feerate_min(ld),
				      feerate_max(ld),
				      &channel->last_sig,
				      cs,
				      &channel->channel_info.remote_fundingkey,
				      &channel->channel_info.theirbase,
				      &channel->channel_info.remote_per_commit,
				      &channel->channel_info.old_remote_per_commit,
				      channel->funder,
				      cfg->fee_base,
				      cfg->fee_per_satoshi,
				      channel->our_msatoshi,
				      &channel->local_basepoints,
				      &channel->local_funding_pubkey,
				      &ld->id,
				      &channel->peer->id,
				      cfg->commit_time_ms,
				      cfg->cltv_expiry_delta,
				      channel->last_was_revoke,
				      channel->last_sent_commit,
				      channel->next_index[LOCAL],
				      channel->next_index[REMOTE],
				      num_revocations,
				      channel->next_htlc_id,
				      htlcs, htlc_states,
				      fulfilled_htlcs, fulfilled_sides,
				      failed_htlcs, failed_sides,
				      channel->scid != NULL,
				      channel->remote_funding_locked,
				      &funding_channel_id,
				      reconnected,
				      channel->state == CHANNELD_SHUTTING_DOWN,
				      channel->remote_shutdown_scriptpubkey != NULL,
				      p2wpkh_for_keyidx(tmpctx, ld,
							channel->final_key_idx),
				      channel->channel_flags,
				      funding_signed,
				      reached_announce_depth,
				      &last_remote_per_commit_secret);

	/* We don't expect a response: we are triggered by funding_depth_cb. */
	subd_send_msg(channel->owner, take(initmsg));

	/* On restart, feerate might not be what we expect: adjust now. */
	if (channel->funder == LOCAL)
		try_update_feerates(ld, channel);
}

bool channel_tell_funding_locked(struct lightningd *ld,
				 struct channel *channel,
				 const struct bitcoin_txid *txid,
				 u32 depth)
{
	/* If not awaiting lockin/announce, it doesn't care any more */
	if (channel->state != CHANNELD_AWAITING_LOCKIN
	    && channel->state != CHANNELD_NORMAL) {
		log_debug(channel->log,
			  "Funding tx confirmed, but peer in state %s",
			  channel_state_name(channel));
		return true;
	}

	if (!channel->owner) {
		log_debug(channel->log,
			  "Funding tx confirmed, but peer disconnected");
		return false;
	}

	subd_send_msg(channel->owner,
		      take(towire_channel_funding_locked(NULL, channel->scid,
							 depth)));

	if (channel->remote_funding_locked
	    && channel->state == CHANNELD_AWAITING_LOCKIN)
		lockin_complete(channel);

	return true;
}

/* Check if we are the fundee of this channel, the channel
 * funding transaction is still not yet seen onchain, and
 * it has been too long since the channel was first opened.
 * If so, we should forget the channel. */
static bool
is_fundee_should_forget(struct lightningd *ld,
			struct channel *channel,
			u32 block_height)
{
	u32 max_funding_unconfirmed = ld->max_funding_unconfirmed;

	/* BOLT #2:
	 *
	 * A non-funding node (fundee):
	 *   - SHOULD forget the channel if it does not see the
	 * funding transaction after a reasonable timeout.
	 */

	/* Only applies if we are fundee. */
	if (channel->funder == LOCAL)
		return false;

	/* Does not apply if we already saw the funding tx. */
	if (channel->scid)
		return false;

	/* Not even reached previous starting blocknum.
	 * (e.g. if --rescan option is used) */
	if (block_height < channel->first_blocknum)
		return false;

	/* Timeout in blocks not yet reached. */
	if (block_height - channel->first_blocknum < max_funding_unconfirmed)
		return false;

	/* Ah forget it! */
	return true;
}

/* Notify all channels of new blocks. */
void channel_notify_new_block(struct lightningd *ld,
			      u32 block_height)
{
	struct peer *peer;
	struct channel *channel;
	struct channel **to_forget = tal_arr(NULL, struct channel *, 0);
	size_t i;

	list_for_each (&ld->peers, peer, list) {
		list_for_each (&peer->channels, channel, list)
			if (is_fundee_should_forget(ld, channel, block_height)) {
				i = tal_count(to_forget);
				tal_resize(&to_forget, i + 1);
				to_forget[i] = channel;
			}
	}

	/* Need to forget in a separate loop, else the above
	 * nested loops may crash due to the last channel of
	 * a peer also deleting the peer, making the inner
	 * loop crash.
	 * list_for_each_safe does not work because it is not
	 * just the freeing of the channel that occurs, but the
	 * potential destruction of the peer that invalidates
	 * memory the inner loop is accessing. */
	for (i = 0; i < tal_count(to_forget); ++i) {
		channel = to_forget[i];
		/* Report it first. */
		log_unusual(channel->log,
			    "Forgetting channel: "
			    "It has been %"PRIu32" blocks without the "
			    "funding transaction %s getting deeply "
			    "confirmed. "
			    "We are fundee and can forget channel without "
			    "loss of funds.",
			    block_height - channel->first_blocknum,
			    type_to_string(tmpctx, struct bitcoin_txid,
					   &channel->funding_txid));
		/* FIXME: Send an error packet for this case! */
		/* And forget it. */
		delete_channel(channel);
	}

	tal_free(to_forget);
}