core-lightning/lightningd/peer_htlcs.c

#include <bitcoin/preimage.h>
#include <bitcoin/tx.h>
#include <ccan/build_assert/build_assert.h>
#include <ccan/cast/cast.h>
#include <ccan/crypto/ripemd160/ripemd160.h>
#include <ccan/mem/mem.h>
#include <ccan/tal/str/str.h>
#include <channeld/gen_channel_wire.h>
#include <common/json_command.h>
#include <common/jsonrpc_errors.h>
#include <common/overflows.h>
#include <common/param.h>
#include <common/sphinx.h>
#include <common/timeout.h>
#include <gossipd/gen_gossip_wire.h>
#include <lightningd/chaintopology.h>
#include <lightningd/htlc_end.h>
#include <lightningd/json.h>
#include <lightningd/jsonrpc.h>
#include <lightningd/lightningd.h>
#include <lightningd/log.h>
#include <lightningd/options.h>
#include <lightningd/pay.h>
#include <lightningd/peer_control.h>
#include <lightningd/peer_htlcs.h>
#include <lightningd/plugin_hook.h>
#include <lightningd/subd.h>
#include <onchaind/gen_onchain_wire.h>
#include <onchaind/onchain_wire.h>
#include <wallet/wallet.h>
#include <wire/gen_onion_wire.h>

static bool state_update_ok(struct channel *channel,
			    enum htlc_state oldstate, enum htlc_state newstate,
			    u64 htlc_id, const char *dir)
{
	enum htlc_state expected = oldstate + 1;

	/* We never get told about RCVD_REMOVE_HTLC, so skip over that
	 * (we initialize in SENT_ADD_HTLC / RCVD_ADD_COMMIT, so those
	 * work). */
	if (expected == RCVD_REMOVE_HTLC)
		expected = RCVD_REMOVE_COMMIT;

	if (newstate != expected) {
		channel_internal_error(channel,
				       "HTLC %s %"PRIu64" invalid update %s->%s",
				       dir, htlc_id,
				       htlc_state_name(oldstate),
				       htlc_state_name(newstate));
		return false;
	}

	log_debug(channel->log, "HTLC %s %"PRIu64" %s->%s",
		  dir, htlc_id,
		  htlc_state_name(oldstate), htlc_state_name(newstate));
	return true;
}

static bool htlc_in_update_state(struct channel *channel,
				 struct htlc_in *hin,
				 enum htlc_state newstate)
{
	if (!state_update_ok(channel, hin->hstate, newstate, hin->key.id, "in"))
		return false;

	wallet_htlc_update(channel->peer->ld->wallet,
			   hin->dbid, newstate, hin->preimage,
			   hin->failcode, hin->failuremsg);

	hin->hstate = newstate;
	return true;
}

static bool htlc_out_update_state(struct channel *channel,
				 struct htlc_out *hout,
				 enum htlc_state newstate)
{
	if (!state_update_ok(channel, hout->hstate, newstate, hout->key.id,
			     "out"))
		return false;

	wallet_htlc_update(channel->peer->ld->wallet, hout->dbid, newstate,
			   hout->preimage, hout->failcode, hout->failuremsg);

	hout->hstate = newstate;
	return true;
}

static void fail_in_htlc(struct htlc_in *hin,
			 enum onion_type failcode,
			 const u8 *failuremsg,
			 const struct short_channel_id *out_channelid)
{
	struct failed_htlc failed_htlc;
	assert(!hin->preimage);

	assert(failcode || failuremsg);
	hin->failcode = failcode;
	if (failuremsg)
		hin->failuremsg = tal_dup_arr(hin, u8, failuremsg, tal_count(failuremsg), 0);

	/* We need this set, since we send it to channeld. */
	if (hin->failcode & UPDATE)
		hin->failoutchannel = *out_channelid;

	/* We update state now to signal it's in progress, for persistence. */
	htlc_in_update_state(hin->key.channel, hin, SENT_REMOVE_HTLC);
	htlc_in_check(hin, __func__);

	/* Tell peer, if we can. */
	if (!hin->key.channel->owner)
		return;

	/* onchaind doesn't care, it can't do anything but wait */
	if (channel_on_chain(hin->key.channel))
		return;

	failed_htlc.id = hin->key.id;
	failed_htlc.failcode = hin->failcode;
	failed_htlc.failreason = cast_const(u8 *, hin->failuremsg);
	if (failed_htlc.failcode & UPDATE)
		failed_htlc.scid = &hin->failoutchannel;
	else
		failed_htlc.scid = NULL;
	subd_send_msg(hin->key.channel->owner,
		      take(towire_channel_fail_htlc(NULL, &failed_htlc,
						    get_block_height(hin->key.channel->owner->ld->topology))));
}

/* This is used for cases where we can immediately fail the HTLC. */
static void local_fail_htlc(struct htlc_in *hin, enum onion_type failcode,
			    const struct short_channel_id *out_channel)
{
	log_info(hin->key.channel->log, "failed htlc %"PRIu64" code 0x%04x (%s)",
		 hin->key.id, failcode, onion_type_name(failcode));

	fail_in_htlc(hin, failcode, NULL, out_channel);
}

void fail_htlc(struct htlc_in *hin, enum onion_type failcode)
{
	assert(failcode);
	/* Final hop never sends an UPDATE. */
	assert(!(failcode & UPDATE));
	local_fail_htlc(hin, failcode, NULL);
}

/* localfail are for handing to the local payer if it's local. */
static void fail_out_htlc(struct htlc_out *hout, const char *localfail)
{
	htlc_out_check(hout, __func__);
	assert(hout->failcode || hout->failuremsg);

	if (hout->am_origin) {
		payment_failed(hout->key.channel->peer->ld, hout, localfail);
	} else if (hout->in) {
		fail_in_htlc(hout->in, hout->failcode, hout->failuremsg,
			     hout->key.channel->scid);
	}
}

/* BOLT #4:
 *
 * * `amt_to_forward`: The amount, in millisatoshis, to forward to the next
 *   receiving peer specified within the routing information.
 *
 *   This value amount MUST include the origin node's computed _fee_ for the
 *   receiving peer. When processing an incoming Sphinx packet and the HTLC
 *   message that it is encapsulated within, if the following inequality
 *   doesn't hold, then the HTLC should be rejected as it would indicate that
 *   a prior hop has deviated from the specified parameters:
 *
 *     incoming_htlc_amt - fee >= amt_to_forward
 *
 *   Where `fee` is either calculated according to the receiving peer's
 *   advertised fee schema (as described in [BOLT
 *   #7](07-routing-gossip.md#htlc-fees)) or is 0, if the processing node is
 *   the final node.
 */
static bool check_amount(struct htlc_in *hin,
			 struct amount_msat amt_to_forward,
			 struct amount_msat amt_in_htlc,
			 struct amount_msat fee)
{
	struct amount_msat fwd;

	if (amount_msat_sub(&fwd, amt_in_htlc, fee)
	    && amount_msat_greater_eq(fwd, amt_to_forward))
		return true;

	log_debug(hin->key.channel->log, "HTLC %"PRIu64" incorrect amount:"
		  " %s in, %s out, fee reqd %s",
		  hin->key.id,
		  type_to_string(tmpctx, struct amount_msat, &amt_in_htlc),
		  type_to_string(tmpctx, struct amount_msat, &amt_to_forward),
		  type_to_string(tmpctx, struct amount_msat, &fee));
	return false;
}

/* BOLT #4:
 *
 *  * `outgoing_cltv_value`: The CLTV value that the _outgoing_ HTLC carrying
 *     the packet should have.
 *
 *        cltv_expiry - cltv_expiry_delta >= outgoing_cltv_value
 *
 *     Inclusion of this field allows a hop to both authenticate the
 *     information specified by the origin node, and the parameters of the
 *     HTLC forwarded, and ensure the origin node is using the current
 *     `cltv_expiry_delta` value.  If there is no next hop,
 *     `cltv_expiry_delta` is 0.  If the values don't correspond, then the
 *     HTLC should be failed and rejected, as this indicates that either a
 *     forwarding node has tampered with the intended HTLC values or that the
 *     origin node has an obsolete `cltv_expiry_delta` value.  The hop MUST be
 *     consistent in responding to an unexpected `outgoing_cltv_value`,
 *     whether it is the final node or not, to avoid leaking its position in
 *     the route.
 */
static bool check_cltv(struct htlc_in *hin,
		       u32 cltv_expiry, u32 outgoing_cltv_value, u32 delta)
{
	if (delta < cltv_expiry && cltv_expiry - delta >= outgoing_cltv_value)
		return true;
	log_debug(hin->key.channel->log, "HTLC %"PRIu64" incorrect CLTV:"
		  " %u in, %u out, delta reqd %u",
		  hin->key.id, cltv_expiry, outgoing_cltv_value, delta);
	return false;
}

void fulfill_htlc(struct htlc_in *hin, const struct preimage *preimage)
{
	u8 *msg;
	struct channel *channel = hin->key.channel;
	struct wallet *wallet = channel->peer->ld->wallet;

	if (hin->hstate != RCVD_ADD_ACK_REVOCATION) {
		log_debug(channel->log,
			  "HTLC fulfilled, but not ready any more (%s).",
			  htlc_state_name(hin->hstate));
		return;
	}

	hin->preimage = tal_dup(hin, struct preimage, preimage);

	/* We update state now to signal it's in progress, for persistence. */
	htlc_in_update_state(channel, hin, SENT_REMOVE_HTLC);

	htlc_in_check(hin, __func__);

	/* Update channel stats */
	wallet_channel_stats_incr_in_fulfilled(wallet,
					       channel->dbid,
					       hin->msat);

	/* No owner?  We'll either send to channeld in peer_htlcs, or
	 * onchaind in onchaind_tell_fulfill. */
	if (!channel->owner) {
		log_debug(channel->log, "HTLC fulfilled, but no owner.");
		return;
	}

	if (channel_on_chain(channel)) {
		msg = towire_onchain_known_preimage(hin, preimage);
	} else {
		struct fulfilled_htlc fulfilled_htlc;
		fulfilled_htlc.id = hin->key.id;
		fulfilled_htlc.payment_preimage = *preimage;
		msg = towire_channel_fulfill_htlc(hin, &fulfilled_htlc);
	}
	subd_send_msg(channel->owner, take(msg));
}

static void handle_localpay(struct htlc_in *hin,
			    u32 cltv_expiry,
			    const struct sha256 *payment_hash,
			    struct amount_msat amt_to_forward,
			    u32 outgoing_cltv_value)
{
	enum onion_type failcode;
	struct lightningd *ld = hin->key.channel->peer->ld;

	/* BOLT #4:
	 *
	 * 1. type: 19 (`final_incorrect_htlc_amount`)
	 * 2. data:
	 *    * [`u64`:`incoming_htlc_amt`]
	 *
	 * The amount in the HTLC doesn't match the value in the onion.
	 */
	if (!check_amount(hin, amt_to_forward, hin->msat, AMOUNT_MSAT(0))) {
		failcode = WIRE_FINAL_INCORRECT_HTLC_AMOUNT;
		goto fail;
	}

	/* BOLT #4:
	 *
	 * 1. type: 18 (`final_incorrect_cltv_expiry`)
	 * 2. data:
	 *    * [`u32`:`cltv_expiry`]
	 *
	 * The CLTV expiry in the HTLC doesn't match the value in the onion.
	 */
	if (!check_cltv(hin, cltv_expiry, outgoing_cltv_value, 0)) {
		failcode = WIRE_FINAL_INCORRECT_CLTV_EXPIRY;
		goto fail;
	}

	/* BOLT #4:
	 *
	 *   - if the `cltv_expiry` value is unreasonably near the present:
	 *     - MUST fail the HTLC.
	 *     - MUST return an `incorrect_or_unknown_payment_details` error.
	 */
	if (get_block_height(ld->topology) + ld->config.cltv_final
	    > cltv_expiry) {
		log_debug(hin->key.channel->log,
			  "Expiry cltv too soon %u < %u + %u",
			  cltv_expiry,
			  get_block_height(ld->topology),
			  ld->config.cltv_final);
		failcode = WIRE_INCORRECT_OR_UNKNOWN_PAYMENT_DETAILS;
		goto fail;
	}

	invoice_try_pay(ld, hin, payment_hash, amt_to_forward);
	return;

fail:
	fail_htlc(hin, failcode);
}

/*
 * A catchall in case outgoing peer disconnects before getting fwd.
 *
 * We could queue this and wait for it to come back, but this is simple.
 */
static void destroy_hout_subd_died(struct htlc_out *hout)
{
	log_debug(hout->key.channel->log,
		  "Failing HTLC %"PRIu64" due to peer death",
		  hout->key.id);

	hout->failcode = WIRE_TEMPORARY_CHANNEL_FAILURE;

	/* Assign a temporary state (we're about to free it!) so checks
	 * are happy that it has a failure code */
	assert(hout->hstate == SENT_ADD_HTLC);
	hout->hstate = RCVD_REMOVE_HTLC;

	fail_out_htlc(hout, "Outgoing subdaemon died");
}

/* This is where channeld gives us the HTLC id, and also reports if it
 * failed immediately. */
static void rcvd_htlc_reply(struct subd *subd, const u8 *msg, const int *fds UNUSED,
			    struct htlc_out *hout)
{
	u16 failure_code;
	u8 *failurestr;
	struct lightningd *ld = subd->ld;

	if (!fromwire_channel_offer_htlc_reply(msg, msg,
					       &hout->key.id,
					       &failure_code,
					       &failurestr)) {
		channel_internal_error(subd->channel,
				       "Bad channel_offer_htlc_reply");
		tal_free(hout);
		return;
	}

	if (failure_code) {
		hout->failcode = (enum onion_type) failure_code;
		if (hout->am_origin) {
			char *localfail = tal_fmt(msg, "%s: %.*s",
						  onion_type_name(failure_code),
						  (int)tal_count(failurestr),
						  (const char *)failurestr);
			payment_failed(ld, hout, localfail);

		} else if (hout->in) {
			local_fail_htlc(hout->in, failure_code,
					 hout->key.channel->scid);

			/* here we haven't called connect_htlc_out(),
			 * so set htlc field with NULL */
			wallet_forwarded_payment_add(ld->wallet,
					 hout->in, NULL,
					 FORWARD_LOCAL_FAILED,
					 failure_code);
		}

		/* Prevent hout from being failed twice. */
		tal_del_destructor(hout, destroy_hout_subd_died);
		tal_free(hout);
		return;
	}

	if (find_htlc_out(&subd->ld->htlcs_out, hout->key.channel, hout->key.id)
	    || hout->key.id == HTLC_INVALID_ID) {
		channel_internal_error(subd->channel,
				    "Bad offer_htlc_reply HTLC id %"PRIu64
				    " is a duplicate",
				    hout->key.id);
		tal_free(hout);
		return;
	}

	/* Add it to lookup table now we know id. */
	connect_htlc_out(&subd->ld->htlcs_out, hout);

	/* When channeld includes it in commitment, we'll make it persistent. */
}

static void htlc_offer_timeout(struct channel *channel)
{
	/* Unset this in case we reconnect and start again. */
	channel->htlc_timeout = NULL;

	/* If owner died, we should already be taken care of. */
	if (!channel->owner || channel->state != CHANNELD_NORMAL)
		return;

	log_unusual(channel->owner->log,
		    "Adding HTLC too slow: killing connection");
	tal_free(channel->owner);
	channel_set_billboard(channel, false,
			      "Adding HTLC timed out: killed connection");
}

enum onion_type send_htlc_out(struct channel *out,
			      struct amount_msat amount, u32 cltv,
			      const struct sha256 *payment_hash,
			      const u8 *onion_routing_packet,
			      struct htlc_in *in,
			      struct htlc_out **houtp)
{
	struct htlc_out *hout;
	u8 *msg;

	if (!channel_can_add_htlc(out)) {
		log_info(out->log, "Attempt to send HTLC but not ready (%s)",
			 channel_state_name(out));
		return WIRE_UNKNOWN_NEXT_PEER;
	}

	if (!out->owner) {
		log_info(out->log, "Attempt to send HTLC but unowned (%s)",
			 channel_state_name(out));
		return WIRE_TEMPORARY_CHANNEL_FAILURE;
	}

	if (!topology_synced(out->peer->ld->topology)) {
		log_info(out->log, "Attempt to send HTLC but still syncing"
			 " with bitcoin network");
		return WIRE_TEMPORARY_CHANNEL_FAILURE;
	}

	/* Make peer's daemon own it, catch if it dies. */
	hout = new_htlc_out(out->owner, out, amount, cltv,
			    payment_hash, onion_routing_packet, in == NULL, in);
	tal_add_destructor(hout, destroy_hout_subd_died);

	/* Give channel 30 seconds to commit (first) htlc. */
	if (!out->htlc_timeout)
		out->htlc_timeout = new_reltimer(out->peer->ld->timers,
						 out, time_from_sec(30),
						 htlc_offer_timeout,
						 out);
	msg = towire_channel_offer_htlc(out, amount, cltv, payment_hash,
					onion_routing_packet);
	subd_req(out->peer->ld, out->owner, take(msg), -1, 0, rcvd_htlc_reply, hout);

	if (houtp)
		*houtp = hout;
	return 0;
}

static void forward_htlc(struct htlc_in *hin,
			 u32 cltv_expiry,
			 struct amount_msat amt_to_forward,
			 u32 outgoing_cltv_value,
			 const struct node_id *next_hop,
			 const u8 next_onion[TOTAL_PACKET_SIZE])
{
	enum onion_type failcode;
	struct amount_msat fee;
	struct lightningd *ld = hin->key.channel->peer->ld;
	struct channel *next = active_channel_by_id(ld, next_hop, NULL);
	struct htlc_out *hout = NULL;

	/* Unknown peer, or peer not ready. */
	if (!next || !next->scid) {
		local_fail_htlc(hin, WIRE_UNKNOWN_NEXT_PEER, NULL);
		wallet_forwarded_payment_add(hin->key.channel->peer->ld->wallet,
					 hin, NULL,
					 FORWARD_LOCAL_FAILED,
					 hin->failcode);
		return;
	}

	/* BOLT #7:
	 *
	 * The origin node:
	 *   - SHOULD accept HTLCs that pay a fee equal to or greater than:
	 *     - fee_base_msat + ( amount_to_forward * fee_proportional_millionths / 1000000 )
	 */
	if (!amount_msat_fee(&fee, amt_to_forward,
				next->feerate_base,
				next->feerate_ppm)) {
		log_broken(ld->log, "Fee overflow forwarding %s!",
			   type_to_string(tmpctx, struct amount_msat,
					  &amt_to_forward));
		failcode = WIRE_FEE_INSUFFICIENT;
		goto fail;
	}
	if (!check_amount(hin, amt_to_forward, hin->msat, fee)) {
		failcode = WIRE_FEE_INSUFFICIENT;
		goto fail;
	}

	if (!check_cltv(hin, cltv_expiry, outgoing_cltv_value,
			ld->config.cltv_expiry_delta)) {
		failcode = WIRE_INCORRECT_CLTV_EXPIRY;
		goto fail;
	}

	/* BOLT #2:
	 *
	 * An offering node:
	 *   - MUST estimate a timeout deadline for each HTLC it offers.
	 *   - MUST NOT offer an HTLC with a timeout deadline before its
	 *     `cltv_expiry`.
	 */
	/* In our case, G = 1, so we need to expire it one after it's expiration.
	 * But never offer an expired HTLC; that's dumb. */
	if (get_block_height(ld->topology) >= outgoing_cltv_value) {
		log_debug(hin->key.channel->log,
			  "Expiry cltv %u too close to current %u",
			  outgoing_cltv_value,
			  get_block_height(ld->topology));
		failcode = WIRE_EXPIRY_TOO_SOON;
		goto fail;
	}

	/* BOLT #4:
	 *
	 *   - if the `cltv_expiry` is unreasonably far in the future:
	 *     - return an `expiry_too_far` error.
	 */
	if (get_block_height(ld->topology)
	    + ld->config.locktime_max < outgoing_cltv_value) {
		log_debug(hin->key.channel->log,
			  "Expiry cltv %u too far from current %u + max %u",
			  outgoing_cltv_value,
			  get_block_height(ld->topology),
			  ld->config.locktime_max);
		failcode = WIRE_EXPIRY_TOO_FAR;
		goto fail;
	}

	hout = tal(tmpctx, struct htlc_out);
	failcode = send_htlc_out(next, amt_to_forward,
				 outgoing_cltv_value, &hin->payment_hash,
				 next_onion, hin, &hout);
	if (!failcode)
		return;

	/* In fact, we didn't get the new htlc_out in these 2 cases */
	if (failcode == WIRE_UNKNOWN_NEXT_PEER ||
		failcode == WIRE_TEMPORARY_CHANNEL_FAILURE) {
		tal_free(hout);
		hout = NULL;
	}

fail:
	local_fail_htlc(hin, failcode, next->scid);
	wallet_forwarded_payment_add(ld->wallet,
				 hin, hout,
				 FORWARD_LOCAL_FAILED,
				 hin->failcode);
}

/* Temporary information, while we resolve the next hop */
struct gossip_resolve {
	struct short_channel_id next_channel;
	struct amount_msat amt_to_forward;
	u32 outgoing_cltv_value;
	u8 *next_onion;
	struct htlc_in *hin;
};

/* We received a resolver reply, which gives us the node_ids of the
 * channel we want to forward over */
static void channel_resolve_reply(struct subd *gossip, const u8 *msg,
				  const int *fds UNUSED, struct gossip_resolve *gr)
{
	struct node_id *peer_id;

	if (!fromwire_gossip_get_channel_peer_reply(msg, msg, &peer_id)) {
		log_broken(gossip->log,
			   "bad fromwire_gossip_get_channel_peer_reply %s",
			   tal_hex(msg, msg));
		return;
	}

	if (!peer_id) {
		local_fail_htlc(gr->hin, WIRE_UNKNOWN_NEXT_PEER, NULL);
		wallet_forwarded_payment_add(gr->hin->key.channel->peer->ld->wallet,
					 gr->hin, NULL,
					 FORWARD_LOCAL_FAILED,
					 gr->hin->failcode);
		tal_free(gr);
		return;
	}

	forward_htlc(gr->hin, gr->hin->cltv_expiry,
		     gr->amt_to_forward, gr->outgoing_cltv_value, peer_id,
		     gr->next_onion);
	tal_free(gr);
}

/**
 * Data passed to the plugin, and as the context for the hook callback
 */
struct htlc_accepted_hook_payload {
	struct route_step *route_step;
	struct htlc_in *hin;
	struct channel *channel;
	struct lightningd *ld;
	u8 *next_onion;
};

/* The possible return value types that a plugin may return for the
 * `htlc_accepted` hook. */
enum htlc_accepted_result {
	htlc_accepted_continue,
	htlc_accepted_fail,
	htlc_accepted_resolve,
};

/**
 * Parses the JSON-RPC response into a struct understood by the callback.
 */
static enum htlc_accepted_result htlc_accepted_hook_deserialize(const char *buffer, const jsmntok_t *toks,
                                                                /* If accepted */
                                                                struct preimage *payment_preimage,
                                                                /* If rejected */
                                                                enum onion_type *failure_code,
                                                                u8 **channel_update)
{
	const jsmntok_t *resulttok, *failcodetok, *paykeytok, *chanupdtok;
	enum htlc_accepted_result result;

	if (!toks || !buffer)
		return htlc_accepted_continue;

	resulttok = json_get_member(buffer, toks, "result");

	/* If the result is "continue" we can just return NULL since
	 * this is the default behavior for this hook anyway */
	if (!resulttok) {
		fatal("Plugin return value does not contain 'result' key %s",
		      json_strdup(tmpctx, buffer, toks));
	}

	if (json_tok_streq(buffer, resulttok, "continue")) {
		return htlc_accepted_continue;
	}

	if (json_tok_streq(buffer, resulttok, "fail")) {
		result = htlc_accepted_fail;
		failcodetok = json_get_member(buffer, toks, "failure_code");
		chanupdtok = json_get_member(buffer, toks, "channel_update");
		if (failcodetok &&
		    !json_to_number(buffer, failcodetok, failure_code))
			fatal("Plugin provided a non-numeric failcode "
			      "in response to an htlc_accepted hook");

		if (!failcodetok)
			*failure_code = WIRE_TEMPORARY_NODE_FAILURE;

		if (chanupdtok)
			*channel_update =
			    json_tok_bin_from_hex(buffer, buffer, chanupdtok);
		else
			*channel_update = NULL;

	} else if (json_tok_streq(buffer, resulttok, "resolve")) {
		result = htlc_accepted_resolve;
		paykeytok = json_get_member(buffer, toks, "payment_key");
		if (!paykeytok)
			fatal(
			    "Plugin did not specify a 'payment_key' in return "
			    "value to the htlc_accepted hook: %s",
			    json_strdup(tmpctx, buffer, resulttok));

		if (!json_to_preimage(buffer, paykeytok,
				      payment_preimage))
			fatal("Plugin specified an invalid 'payment_key': %s",
			      json_tok_full(buffer, resulttok));
	} else {
		fatal("Plugin responded with an unknown result to the "
		      "htlc_accepted hook: %s",
		      json_strdup(tmpctx, buffer, resulttok));
	}

	return result;
}

static void htlc_accepted_hook_serialize(struct htlc_accepted_hook_payload *p,
					 struct json_stream *s)
{
	const struct route_step *rs = p->route_step;
	const struct htlc_in *hin = p->hin;
	s32 expiry = hin->cltv_expiry, blockheight = p->ld->topology->tip->height;
	json_object_start(s, "onion");

	json_add_hex_talarr (s, "payload", rs->raw_payload);
	if (rs->type == SPHINX_V0_PAYLOAD) {
		json_object_start(s, "per_hop_v0");
		json_add_string(s, "realm", "00");
		json_add_short_channel_id(s, "short_channel_id", &rs->payload.v0.channel_id);
		json_add_amount_msat_only(s, "forward_amount", rs->payload.v0.amt_forward);
		json_add_u64(s, "outgoing_cltv_value", rs->payload.v0.outgoing_cltv);
		json_object_end(s);
	}

	json_add_hex_talarr(s, "next_onion", p->next_onion);
	json_add_secret(s, "shared_secret", hin->shared_secret);
	json_object_end(s);

	json_object_start(s, "htlc");
	json_add_amount_msat_only(s, "amount", hin->msat);
	json_add_u32(s, "cltv_expiry", expiry);
	json_add_s32(s, "cltv_expiry_relative", expiry - blockheight);
	json_add_sha256(s, "payment_hash", &hin->payment_hash);
	json_object_end(s);
}

/**
 * Callback when a plugin answers to the htlc_accepted hook
 */
static void
htlc_accepted_hook_callback(struct htlc_accepted_hook_payload *request,
			    const char *buffer, const jsmntok_t *toks)
{
	struct route_step *rs = request->route_step;
	struct htlc_in *hin = request->hin;
	struct channel *channel = request->channel;
	struct lightningd *ld = request->ld;
	struct preimage payment_preimage;
	u8 *req;
	enum htlc_accepted_result result;
	enum onion_type failure_code;
	u8 *channel_update;
	struct hop_data *hop_data;
	result = htlc_accepted_hook_deserialize(buffer, toks, &payment_preimage, &failure_code, &channel_update);

	hop_data = &rs->payload.v0;
	switch (result) {
	case htlc_accepted_continue:
		if (rs->nextcase == ONION_FORWARD) {
			struct gossip_resolve *gr = tal(ld, struct gossip_resolve);

			gr->next_onion = serialize_onionpacket(gr, rs->next);
			gr->next_channel = hop_data->channel_id;
			gr->amt_to_forward = hop_data->amt_forward;
			gr->outgoing_cltv_value = hop_data->outgoing_cltv;
			gr->hin = hin;

			req = towire_gossip_get_channel_peer(tmpctx, &gr->next_channel);
			log_debug(channel->log, "Asking gossip to resolve channel %s",
				  type_to_string(tmpctx, struct short_channel_id,
						 &gr->next_channel));
			subd_req(hin, ld->gossip, req, -1, 0,
				 channel_resolve_reply, gr);
		} else
			handle_localpay(hin, hin->cltv_expiry, &hin->payment_hash,
					hop_data->amt_forward,
					hop_data->outgoing_cltv);
		break;
	case htlc_accepted_fail:
		log_debug(channel->log,
			  "Failing incoming HTLC as instructed by plugin hook");
		fail_in_htlc(hin, failure_code, NULL, &hop_data->channel_id);
		break;
	case htlc_accepted_resolve:
		fulfill_htlc(hin, &payment_preimage);
		break;
	}

	tal_free(request);
}

REGISTER_PLUGIN_HOOK(htlc_accepted, htlc_accepted_hook_callback,
		     struct htlc_accepted_hook_payload *,
		     htlc_accepted_hook_serialize,
		     struct htlc_accepted_hook_payload *);

/**
 * Everyone is committed to this htlc of theirs
 *
 * @param channel: The channel this HTLC was accepted from.
 * @param id: the ID of the HTLC we accepted
 * @param replay: Are we loading from the database and therefore should not
 *        perform the transition to RCVD_ADD_ACK_REVOCATION?
 * @param[out] failcode: If we decide to fail right away this will be set to a
 *        non-zero failcode.
 */
static bool peer_accepted_htlc(struct channel *channel, u64 id,
			       bool replay, enum onion_type *failcode)
{
	struct htlc_in *hin;
	struct route_step *rs;
	struct onionpacket *op;
	struct lightningd *ld = channel->peer->ld;
	struct htlc_accepted_hook_payload *hook_payload;

	hin = find_htlc_in(&ld->htlcs_in, channel, id);
	if (!hin) {
		channel_internal_error(channel,
				    "peer_got_revoke unknown htlc %"PRIu64, id);
		return false;
	}

	if (!replay && !htlc_in_update_state(channel, hin, RCVD_ADD_ACK_REVOCATION))
		return false;
	htlc_in_check(hin, __func__);

#if DEVELOPER
	if (channel->peer->ignore_htlcs) {
		log_debug(channel->log, "their htlc %"PRIu64" dev_ignore_htlcs",
			  id);
		return true;
	}
#endif
	/* BOLT #2:
	 *
	 *   - SHOULD fail to route any HTLC added after it has sent `shutdown`.
	 */
	if (channel->state == CHANNELD_SHUTTING_DOWN) {
		*failcode = WIRE_PERMANENT_CHANNEL_FAILURE;
		goto out;
	}

	/* BOLT #2:
	 *
	 * A fulfilling node:
	 *   - for each HTLC it is attempting to fulfill:
	 *     - MUST estimate a fulfillment deadline.
	 *   - MUST fail (and not forward) an HTLC whose fulfillment deadline is
	 *     already past.
	 */
	/* Our deadline is half the cltv_delta we insist on, so this check is
	 * a subset of the cltv check done in handle_localpay and
	 * forward_htlc. */

	/* Channeld sets this to NULL if couldn't parse onion */
	if (!hin->shared_secret) {
		*failcode = WIRE_INVALID_ONION_KEY;
		goto out;
	}

	/* FIXME: Have channeld hand through just the route_step! */

	/* channeld tests this, so it should pass. */
	op = parse_onionpacket(tmpctx, hin->onion_routing_packet,
			       sizeof(hin->onion_routing_packet),
			       failcode);
	if (!op) {
		channel_internal_error(channel,
				       "bad onion in got_revoke: %s",
				       tal_hexstr(channel, hin->onion_routing_packet,
						  sizeof(hin->onion_routing_packet)));
		return false;
	}

	/* If it's crap, not channeld's fault, just fail it */
	rs = process_onionpacket(tmpctx, op, hin->shared_secret->data,
				 hin->payment_hash.u.u8,
				 sizeof(hin->payment_hash));
	if (!rs) {
		channel_internal_error(channel,
				       "bad process_onionpacket in got_revoke: %s",
				       tal_hexstr(channel, hin->onion_routing_packet,
						  sizeof(hin->onion_routing_packet)));
		return false;
	}

	/* Unknown realm isn't a bad onion, it's a normal failure. */
	/* FIXME: if we want hooks to handle foreign realms we should
	 * move this check to the hook callback. */
	if (rs->type != SPHINX_V0_PAYLOAD) {
		*failcode = WIRE_INVALID_REALM;
		goto out;
	}

	/* It's time to package up all the information and call the
	 * hook so plugins can interject if they want */
	hook_payload = tal(hin, struct htlc_accepted_hook_payload);
	hook_payload->route_step = tal_steal(hook_payload, rs);
	hook_payload->ld = ld;
	hook_payload->hin = hin;
	hook_payload->channel = channel;
	hook_payload->next_onion = serialize_onionpacket(hook_payload, rs->next);

	plugin_hook_call_htlc_accepted(ld, hook_payload, hook_payload);

	/* Falling through here is ok, after all the HTLC locked */
	*failcode = 0;
out:
	log_debug(channel->log, "their htlc %"PRIu64" %s",
		  id, *failcode ? onion_type_name(*failcode) : "locked");

	return true;
}

static void fulfill_our_htlc_out(struct channel *channel, struct htlc_out *hout,
				 const struct preimage *preimage)
{
	struct lightningd *ld = channel->peer->ld;

	assert(!hout->preimage);
	hout->preimage = tal_dup(hout, struct preimage, preimage);
	htlc_out_check(hout, __func__);

	wallet_htlc_update(ld->wallet, hout->dbid, hout->hstate,
			   hout->preimage, hout->failcode, hout->failuremsg);
	/* Update channel stats */
	wallet_channel_stats_incr_out_fulfilled(ld->wallet,
						channel->dbid,
						hout->msat);

	if (hout->am_origin)
		payment_succeeded(ld, hout, preimage);
	else if (hout->in) {
		fulfill_htlc(hout->in, preimage);
		wallet_forwarded_payment_add(ld->wallet, hout->in, hout,
					     FORWARD_SETTLED, 0);
	}
}

static bool peer_fulfilled_our_htlc(struct channel *channel,
				    const struct fulfilled_htlc *fulfilled)
{
	struct lightningd *ld = channel->peer->ld;
	struct htlc_out *hout;

	hout = find_htlc_out(&ld->htlcs_out, channel, fulfilled->id);
	if (!hout) {
		channel_internal_error(channel,
				    "fulfilled_our_htlc unknown htlc %"PRIu64,
				    fulfilled->id);
		return false;
	}

	if (!htlc_out_update_state(channel, hout, RCVD_REMOVE_COMMIT))
		return false;

	fulfill_our_htlc_out(channel, hout, &fulfilled->payment_preimage);
	return true;
}

void onchain_fulfilled_htlc(struct channel *channel,
			    const struct preimage *preimage)
{
	struct htlc_out_map_iter outi;
	struct htlc_out *hout;
	struct sha256 payment_hash;
	struct lightningd *ld = channel->peer->ld;

	sha256(&payment_hash, preimage, sizeof(*preimage));

	/* FIXME: use db to look this up! */
	for (hout = htlc_out_map_first(&ld->htlcs_out, &outi);
	     hout;
	     hout = htlc_out_map_next(&ld->htlcs_out, &outi)) {
		if (hout->key.channel != channel)
			continue;

		/* It's possible that we failed some and succeeded one,
		 * if we got multiple errors. */
		if (hout->failcode != 0 || hout->failuremsg)
			continue;

		if (!sha256_eq(&hout->payment_hash, &payment_hash))
			continue;

		/* We may have already fulfilled before going onchain, or
		 * we can fulfill onchain multiple times. */
		if (!hout->preimage) {
			/* Force state to something which allows a preimage */
			hout->hstate = RCVD_REMOVE_HTLC;
			fulfill_our_htlc_out(channel, hout, preimage);
		}

		/* We keep going: this is something of a leak, but onchain
		 * we have no real way of distinguishing HTLCs anyway */
	}
}

static bool peer_failed_our_htlc(struct channel *channel,
				 const struct failed_htlc *failed)
{
	struct htlc_out *hout;
	struct lightningd *ld = channel->peer->ld;

	hout = find_htlc_out(&ld->htlcs_out, channel, failed->id);
	if (!hout) {
		channel_internal_error(channel,
				    "failed_our_htlc unknown htlc %"PRIu64,
				    failed->id);
		return false;
	}

	if (!htlc_out_update_state(channel, hout, RCVD_REMOVE_COMMIT))
		return false;

	hout->failcode = failed->failcode;
	if (!failed->failcode)
		hout->failuremsg = tal_dup_arr(hout, u8, failed->failreason,
					       tal_count(failed->failreason), 0);

	else
		hout->failuremsg = NULL;

	log_debug(channel->log, "Our HTLC %"PRIu64" failed (%u)", failed->id,
		  hout->failcode);
	htlc_out_check(hout, __func__);

	if (hout->in)
		wallet_forwarded_payment_add(ld->wallet, hout->in,
					 hout, FORWARD_FAILED, hout->failcode);

	return true;
}

void onchain_failed_our_htlc(const struct channel *channel,
			     const struct htlc_stub *htlc,
			     const char *why)
{
	struct lightningd *ld = channel->peer->ld;
	struct htlc_out *hout;

	hout = find_htlc_out(&ld->htlcs_out, channel, htlc->id);
	if (!hout)
		return;

	/* Don't fail twice (or if already succeeded)! */
	if (hout->failuremsg || hout->failcode || hout->preimage)
		return;

	hout->failcode = WIRE_PERMANENT_CHANNEL_FAILURE;

	/* Force state to something which expects a failure, and save to db */
	hout->hstate = RCVD_REMOVE_HTLC;
	htlc_out_check(hout, __func__);
	wallet_htlc_update(ld->wallet, hout->dbid, hout->hstate,
			   hout->preimage, hout->failcode, hout->failuremsg);

	if (hout->am_origin) {
		assert(why != NULL);
		char *localfail = tal_fmt(channel, "%s: %s",
					  onion_type_name(WIRE_PERMANENT_CHANNEL_FAILURE),
					  why);
		payment_failed(ld, hout, localfail);
		tal_free(localfail);
	} else if (hout->in) {
		local_fail_htlc(hout->in, WIRE_PERMANENT_CHANNEL_FAILURE,
				hout->key.channel->scid);
		wallet_forwarded_payment_add(hout->key.channel->peer->ld->wallet,
					 hout->in, hout,
					 FORWARD_LOCAL_FAILED,
					 hout->failcode);
	}
}

static void remove_htlc_in(struct channel *channel, struct htlc_in *hin)
{
	htlc_in_check(hin, __func__);
	assert(hin->failuremsg || hin->preimage || hin->failcode);

	log_debug(channel->log, "Removing in HTLC %"PRIu64" state %s %s",
		  hin->key.id, htlc_state_name(hin->hstate),
		  hin->preimage ? "FULFILLED"
		  : hin->failcode ? onion_type_name(hin->failcode)
		  : "REMOTEFAIL");

	/* If we fulfilled their HTLC, credit us. */
	if (hin->preimage) {
		struct amount_msat oldamt = channel->our_msat;
		if (!amount_msat_add(&channel->our_msat, channel->our_msat,
				     hin->msat)) {
			channel_internal_error(channel,
					       "Overflow our_msat %s + HTLC %s",
					       type_to_string(tmpctx,
							      struct amount_msat,
							      &channel->our_msat),
					       type_to_string(tmpctx,
							      struct amount_msat,
							      &hin->msat));
		}
		log_debug(channel->log, "Balance %s -> %s",
			  type_to_string(tmpctx, struct amount_msat, &oldamt),
			  type_to_string(tmpctx, struct amount_msat,
					 &channel->our_msat));
		if (amount_msat_greater(channel->our_msat,
					channel->msat_to_us_max))
			channel->msat_to_us_max = channel->our_msat;
	}

	tal_free(hin);
}

static void remove_htlc_out(struct channel *channel, struct htlc_out *hout)
{
	htlc_out_check(hout, __func__);
	assert(hout->failuremsg || hout->preimage || hout->failcode);
	log_debug(channel->log, "Removing out HTLC %"PRIu64" state %s %s",
		  hout->key.id, htlc_state_name(hout->hstate),
		  hout->preimage ? "FULFILLED"
		  : hout->failcode ? onion_type_name(hout->failcode)
		  : "REMOTEFAIL");

	/* If it's failed, now we can forward since it's completely locked-in */
	if (!hout->preimage) {
		fail_out_htlc(hout, NULL);
	} else {
		struct amount_msat oldamt = channel->our_msat;
		/* We paid for this HTLC, so deduct balance. */
		if (!amount_msat_sub(&channel->our_msat, channel->our_msat,
				     hout->msat)) {
			channel_internal_error(channel,
					       "Underflow our_msat %s - HTLC %s",
					       type_to_string(tmpctx,
							      struct amount_msat,
							      &channel->our_msat),
					       type_to_string(tmpctx,
							      struct amount_msat,
							      &hout->msat));
		}

		log_debug(channel->log, "Balance %s -> %s",
			  type_to_string(tmpctx, struct amount_msat, &oldamt),
			  type_to_string(tmpctx, struct amount_msat,
					 &channel->our_msat));
		if (amount_msat_less(channel->our_msat, channel->msat_to_us_min))
			channel->msat_to_us_min = channel->our_msat;
	}

	tal_free(hout);
}

static bool update_in_htlc(struct channel *channel,
			   u64 id, enum htlc_state newstate)
{
	struct htlc_in *hin;
	struct lightningd *ld = channel->peer->ld;

	hin = find_htlc_in(&ld->htlcs_in, channel, id);
	if (!hin) {
		channel_internal_error(channel, "Can't find in HTLC %"PRIu64, id);
		return false;
	}

	if (!htlc_in_update_state(channel, hin, newstate))
		return false;

	htlc_in_check(hin, __func__);
	if (newstate == SENT_REMOVE_ACK_REVOCATION)
		remove_htlc_in(channel, hin);

	return true;
}

static bool update_out_htlc(struct channel *channel,
			    u64 id, enum htlc_state newstate)
{
	struct lightningd *ld = channel->peer->ld;
	struct htlc_out *hout;

	hout = find_htlc_out(&ld->htlcs_out, channel, id);
	if (!hout) {
		channel_internal_error(channel, "Can't find out HTLC %"PRIu64, id);
		return false;
	}

	if (!hout->dbid) {
		wallet_htlc_save_out(ld->wallet, channel, hout);
		/* Update channel stats */
		wallet_channel_stats_incr_out_offered(ld->wallet,
						      channel->dbid,
						      hout->msat);

		if (hout->in) {
			wallet_forwarded_payment_add(ld->wallet, hout->in, hout,
						     FORWARD_OFFERED, 0);
		}

		/* For our own HTLCs, we commit payment to db lazily */
		if (hout->origin_htlc_id == 0)
			payment_store(ld,
				      &hout->payment_hash);
	}

	if (!htlc_out_update_state(channel, hout, newstate))
		return false;

	/* First transition into commitment; now it outlives peer. */
	if (newstate == SENT_ADD_COMMIT) {
		tal_del_destructor(hout, destroy_hout_subd_died);
		tal_steal(ld, hout);

	} else if (newstate == RCVD_REMOVE_ACK_REVOCATION) {
		remove_htlc_out(channel, hout);
	}
	return true;
}

static bool changed_htlc(struct channel *channel,
			 const struct changed_htlc *changed)
{
	if (htlc_state_owner(changed->newstate) == LOCAL)
		return update_out_htlc(channel, changed->id, changed->newstate);
	else
		return update_in_htlc(channel, changed->id, changed->newstate);
}

/* FIXME: This should be a complete check, not just a sanity check.
 * Perhaps that means we need a cookie from the HSM? */
static bool valid_commitment_tx(struct channel *channel,
				const struct bitcoin_tx *tx)
{
	/* We've had past issues where all outputs are trimmed. */
	if (tx->wtx->num_outputs == 0) {
		channel_internal_error(channel,
				       "channel_got_commitsig: zero output tx! %s",
				       type_to_string(tmpctx, struct bitcoin_tx, tx));
		return false;
	}
	return true;
}

static bool peer_save_commitsig_received(struct channel *channel, u64 commitnum,
					 struct bitcoin_tx *tx,
					 const struct bitcoin_signature *commit_sig)
{
	if (commitnum != channel->next_index[LOCAL]) {
		channel_internal_error(channel,
			   "channel_got_commitsig: expected commitnum %"PRIu64
			   " got %"PRIu64,
			   channel->next_index[LOCAL], commitnum);
		return false;
	}

	/* Basic sanity check */
	if (!valid_commitment_tx(channel, tx))
		return false;

	channel->next_index[LOCAL]++;

	/* Update channel->last_sig and channel->last_tx before saving to db */
	channel_set_last_tx(channel, tx, commit_sig, TX_CHANNEL_UNILATERAL);

	return true;
}

static bool peer_save_commitsig_sent(struct channel *channel, u64 commitnum)
{
	struct lightningd *ld = channel->peer->ld;

	if (commitnum != channel->next_index[REMOTE]) {
		channel_internal_error(channel,
			   "channel_sent_commitsig: expected commitnum %"PRIu64
			   " got %"PRIu64,
			   channel->next_index[REMOTE], commitnum);
		return false;
	}

	channel->next_index[REMOTE]++;

	/* FIXME: Save to database, with sig and HTLCs. */
	wallet_channel_save(ld->wallet, channel);
	return true;
}

void peer_sending_commitsig(struct channel *channel, const u8 *msg)
{
	u64 commitnum;
	u32 feerate;
	struct changed_htlc *changed_htlcs;
	size_t i, maxid = 0, num_local_added = 0;
	struct bitcoin_signature commit_sig;
	secp256k1_ecdsa_signature *htlc_sigs;
	struct lightningd *ld = channel->peer->ld;

	channel->htlc_timeout = tal_free(channel->htlc_timeout);

	if (!fromwire_channel_sending_commitsig(msg, msg,
						&commitnum,
						&feerate,
						&changed_htlcs,
						&commit_sig, &htlc_sigs)) {
		channel_internal_error(channel, "bad channel_sending_commitsig %s",
				       tal_hex(channel, msg));
		return;
	}

	for (i = 0; i < tal_count(changed_htlcs); i++) {
		if (!changed_htlc(channel, changed_htlcs + i)) {
			channel_internal_error(channel,
				   "channel_sending_commitsig: update failed");
			return;
		}

		/* While we're here, sanity check added ones are in
		 * ascending order. */
		if (changed_htlcs[i].newstate == SENT_ADD_COMMIT) {
			num_local_added++;
			if (changed_htlcs[i].id > maxid)
				maxid = changed_htlcs[i].id;
		}
	}

	if (num_local_added != 0) {
		if (maxid != channel->next_htlc_id + num_local_added - 1) {
			channel_internal_error(channel,
				   "channel_sending_commitsig:"
				   " Added %"PRIu64", maxid now %"PRIu64
				   " from %"PRIu64,
				   num_local_added, maxid, channel->next_htlc_id);
			return;
		}
		channel->next_htlc_id += num_local_added;
	}

	/* Update their feerate. */
	channel->channel_info.feerate_per_kw[REMOTE] = feerate;
	if (feerate > channel->max_possible_feerate)
		channel->max_possible_feerate = feerate;
	if (feerate < channel->min_possible_feerate)
		channel->min_possible_feerate = feerate;

	if (!peer_save_commitsig_sent(channel, commitnum))
		return;

	/* Last was commit. */
	channel->last_was_revoke = false;
	tal_free(channel->last_sent_commit);
	channel->last_sent_commit = tal_steal(channel, changed_htlcs);
	wallet_channel_save(ld->wallet, channel);

	/* Tell it we've got it, and to go ahead with commitment_signed. */
	subd_send_msg(channel->owner,
		      take(towire_channel_sending_commitsig_reply(msg)));
}

static bool channel_added_their_htlc(struct channel *channel,
				     const struct added_htlc *added,
				     const struct secret *shared_secret)
{
	struct lightningd *ld = channel->peer->ld;
	struct htlc_in *hin;

	/* BOLT #2:
	 *
	 *  - receiving an `amount_msat` equal to 0, OR less than its own `htlc_minimum_msat`:
	 *    - SHOULD fail the channel.
	 */
	if (amount_msat_eq(added->amount, AMOUNT_MSAT(0))
	    || amount_msat_less(added->amount, channel->our_config.htlc_minimum)) {
		channel_internal_error(channel,
				       "trying to add HTLC amount %s"
				       " but minimum is %s",
				       type_to_string(tmpctx,
						      struct amount_msat,
						      &added->amount),
				       type_to_string(tmpctx,
						      struct amount_msat,
						      &channel->our_config.htlc_minimum));
		return false;
	}

	/* FIXME: Our wire generator can't handle optional elems in arrays,
	 * so we translate all-zero-shared-secret to NULL. */
	if (memeqzero(shared_secret, sizeof(&shared_secret)))
		shared_secret = NULL;

	/* This stays around even if we fail it immediately: it *is*
	 * part of the current commitment. */
	hin = new_htlc_in(channel, channel, added->id, added->amount,
			  added->cltv_expiry, &added->payment_hash,
			  shared_secret, added->onion_routing_packet);

	/* Save an incoming htlc to the wallet */
	wallet_htlc_save_in(ld->wallet, channel, hin);
	/* Update channel stats */
	wallet_channel_stats_incr_in_offered(ld->wallet, channel->dbid,
					     added->amount);

	log_debug(channel->log, "Adding their HTLC %"PRIu64, added->id);
	connect_htlc_in(&channel->peer->ld->htlcs_in, hin);
	return true;
}

/* The peer doesn't tell us this separately, but logically it's a separate
 * step to receiving commitsig */
static bool peer_sending_revocation(struct channel *channel,
				    struct added_htlc *added,
				    struct fulfilled_htlc *fulfilled,
				    struct failed_htlc **failed,
				    struct changed_htlc *changed)
{
	size_t i;

	for (i = 0; i < tal_count(added); i++) {
		if (!update_in_htlc(channel, added[i].id, SENT_ADD_REVOCATION))
			return false;
	}
	for (i = 0; i < tal_count(fulfilled); i++) {
		if (!update_out_htlc(channel, fulfilled[i].id,
				     SENT_REMOVE_REVOCATION))
			return false;
	}
	for (i = 0; i < tal_count(failed); i++) {
		if (!update_out_htlc(channel, failed[i]->id, SENT_REMOVE_REVOCATION))
			return false;
	}
	for (i = 0; i < tal_count(changed); i++) {
		if (changed[i].newstate == RCVD_ADD_ACK_COMMIT) {
			if (!update_out_htlc(channel, changed[i].id,
					     SENT_ADD_ACK_REVOCATION))
				return false;
		} else {
			if (!update_in_htlc(channel, changed[i].id,
					    SENT_REMOVE_ACK_REVOCATION))
				return false;
		}
	}

	channel->last_was_revoke = true;
	return true;
}

struct deferred_commitsig {
	struct channel *channel;
	const u8 *msg;
};

static void retry_deferred_commitsig(struct chain_topology *topo,
				     struct deferred_commitsig *d)
{
	peer_got_commitsig(d->channel, d->msg);
	tal_free(d);
}

/* This also implies we're sending revocation */
void peer_got_commitsig(struct channel *channel, const u8 *msg)
{
	u64 commitnum;
	u32 feerate;
	struct bitcoin_signature commit_sig;
	secp256k1_ecdsa_signature *htlc_sigs;
	struct added_htlc *added;
	struct secret *shared_secrets;
	struct fulfilled_htlc *fulfilled;
	struct failed_htlc **failed;
	struct changed_htlc *changed;
	struct bitcoin_tx *tx;
	size_t i;
	struct lightningd *ld = channel->peer->ld;

	/* If we're not synced with bitcoin network, we can't accept
	 * any HTLCs.  We stall at this point, in the hope that it
	 * won't take long! */
	if (!topology_synced(ld->topology)) {
		struct deferred_commitsig *d;

		log_unusual(channel->log,
			    "Deferring incoming commit until we sync");

		/* If subdaemon dies, we want to forget this. */
		d = tal(channel->owner, struct deferred_commitsig);
		d->channel = channel;
		d->msg = tal_dup_arr(d, u8, msg, tal_count(msg), 0);
		topology_add_sync_waiter(d, ld->topology,
					 retry_deferred_commitsig, d);
		return;
	}

	if (!fromwire_channel_got_commitsig(msg, msg,
					    &commitnum,
					    &feerate,
					    &commit_sig,
					    &htlc_sigs,
					    &added,
					    &shared_secrets,
					    &fulfilled,
					    &failed,
					    &changed,
					    &tx)) {
		channel_internal_error(channel,
				    "bad fromwire_channel_got_commitsig %s",
				    tal_hex(channel, msg));
		return;
	}
	tx->chainparams = get_chainparams(ld);

	log_debug(channel->log,
		  "got commitsig %"PRIu64
		  ": feerate %u, %zu added, %zu fulfilled, %zu failed, %zu changed",
		  commitnum, feerate, tal_count(added), tal_count(fulfilled),
		  tal_count(failed), tal_count(changed));

	/* New HTLCs */
	for (i = 0; i < tal_count(added); i++) {
		if (!channel_added_their_htlc(channel, &added[i], &shared_secrets[i]))
			return;
	}

	/* Save information now for fulfilled & failed HTLCs */
	for (i = 0; i < tal_count(fulfilled); i++) {
		if (!peer_fulfilled_our_htlc(channel, &fulfilled[i]))
			return;
	}

	for (i = 0; i < tal_count(failed); i++) {
		if (!peer_failed_our_htlc(channel, failed[i]))
			return;
	}

	for (i = 0; i < tal_count(changed); i++) {
		if (!changed_htlc(channel, &changed[i])) {
			channel_internal_error(channel,
					    "got_commitsig: update failed");
			return;
		}
	}

	/* Update both feerates: if we're funder, REMOTE should already be
	 * that feerate, if we're not, we're about to ACK anyway. */
	channel->channel_info.feerate_per_kw[LOCAL]
		= channel->channel_info.feerate_per_kw[REMOTE]
		= feerate;

	if (feerate > channel->max_possible_feerate)
		channel->max_possible_feerate = feerate;
	if (feerate < channel->min_possible_feerate)
		channel->min_possible_feerate = feerate;

	/* Since we're about to send revoke, bump state again. */
	if (!peer_sending_revocation(channel, added, fulfilled, failed, changed))
		return;

	if (!peer_save_commitsig_received(channel, commitnum, tx, &commit_sig))
		return;

	wallet_channel_save(ld->wallet, channel);

	tal_free(channel->last_htlc_sigs);
	channel->last_htlc_sigs = tal_steal(channel, htlc_sigs);
	wallet_htlc_sigs_save(ld->wallet, channel->dbid,
			      channel->last_htlc_sigs);

	/* Tell it we've committed, and to go ahead with revoke. */
	msg = towire_channel_got_commitsig_reply(msg);
	subd_send_msg(channel->owner, take(msg));
}

/* Shuffle them over, forgetting the ancient one. */
void update_per_commit_point(struct channel *channel,
			     const struct pubkey *per_commitment_point)
{
	struct channel_info *ci = &channel->channel_info;
	ci->old_remote_per_commit = ci->remote_per_commit;
	ci->remote_per_commit = *per_commitment_point;
}

void peer_got_revoke(struct channel *channel, const u8 *msg)
{
	u64 revokenum;
	struct secret per_commitment_secret;
	struct pubkey next_per_commitment_point;
	struct changed_htlc *changed;
	enum onion_type *failcodes;
	size_t i;
	struct lightningd *ld = channel->peer->ld;
	u32 feerate;

	if (!fromwire_channel_got_revoke(msg, msg,
					 &revokenum, &per_commitment_secret,
					 &next_per_commitment_point,
					 &feerate,
					 &changed)) {
		channel_internal_error(channel, "bad fromwire_channel_got_revoke %s",
				    tal_hex(channel, msg));
		return;
	}

	log_debug(channel->log,
		  "got revoke %"PRIu64": %zu changed",
		  revokenum, tal_count(changed));

	/* Save any immediate failures for after we reply. */
	failcodes = tal_arrz(msg, enum onion_type, tal_count(changed));
	for (i = 0; i < tal_count(changed); i++) {
		/* If we're doing final accept, we need to forward */
		if (changed[i].newstate == RCVD_ADD_ACK_REVOCATION) {
			if (!peer_accepted_htlc(channel, changed[i].id, false,
						&failcodes[i]))
				return;
		} else {
			if (!changed_htlc(channel, &changed[i])) {
				channel_internal_error(channel,
						    "got_revoke: update failed");
				return;
			}
		}
	}

	if (revokenum >= (1ULL << 48)) {
		channel_internal_error(channel, "got_revoke: too many txs %"PRIu64,
				    revokenum);
		return;
	}

	if (revokenum != revocations_received(&channel->their_shachain.chain)) {
		channel_internal_error(channel, "got_revoke: expected %"PRIu64
				    " got %"PRIu64,
				    revocations_received(&channel->their_shachain.chain), revokenum);
		return;
	}

	/* BOLT #2:
	 *
	 *   - if the `per_commitment_secret` was not generated by the protocol
	 *     in [BOLT #3](03-transactions.md#per-commitment-secret-requirements):
	 *     - MAY fail the channel.
	 */
	if (!wallet_shachain_add_hash(ld->wallet,
				      &channel->their_shachain,
				      shachain_index(revokenum),
				      &per_commitment_secret)) {
		channel_fail_permanent(channel,
				    "Bad per_commitment_secret %s for %"PRIu64,
				    type_to_string(msg, struct secret,
						   &per_commitment_secret),
				    revokenum);
		return;
	}

	/* Update feerate: if we are funder, their revoke_and_ack has set
	 * this for local feerate. */
	channel->channel_info.feerate_per_kw[LOCAL] = feerate;

	/* FIXME: Check per_commitment_secret -> per_commit_point */
	update_per_commit_point(channel, &next_per_commitment_point);

	/* Tell it we've committed, and to go ahead with revoke. */
	msg = towire_channel_got_revoke_reply(msg);
	subd_send_msg(channel->owner, take(msg));

	/* Now, any HTLCs we need to immediately fail? */
	for (i = 0; i < tal_count(changed); i++) {
		struct htlc_in *hin;

		if (!failcodes[i])
			continue;

		/* These are all errors before finding next hop. */
		assert(!(failcodes[i] & UPDATE));

		hin = find_htlc_in(&ld->htlcs_in, channel, changed[i].id);
		local_fail_htlc(hin, failcodes[i], NULL);
		// in fact, now we don't know if this htlc is a forward or localpay!
		wallet_forwarded_payment_add(ld->wallet,
					 hin, NULL,
					 FORWARD_LOCAL_FAILED,
					 hin->failcode);
	}
	wallet_channel_save(ld->wallet, channel);
}

static void add_htlc(struct added_htlc **htlcs,
		     enum htlc_state **htlc_states,
		     u64 id,
		     struct amount_msat amount,
		     const struct sha256 *payment_hash,
		     u32 cltv_expiry,
		     const u8 onion_routing_packet[TOTAL_PACKET_SIZE],
		     enum htlc_state state)
{
	struct added_htlc a;

	a.id = id;
	a.amount = amount;
	a.payment_hash = *payment_hash;
	a.cltv_expiry = cltv_expiry;
	memcpy(a.onion_routing_packet, onion_routing_packet,
	       sizeof(a.onion_routing_packet));

	tal_arr_expand(htlcs, a);
	tal_arr_expand(htlc_states, state);
}

static void add_fulfill(u64 id, enum side side,
			const struct preimage *payment_preimage,
			struct fulfilled_htlc **fulfilled_htlcs,
			enum side **fulfilled_sides)
{
	struct fulfilled_htlc f;

	f.id = id;
	f.payment_preimage = *payment_preimage;

	tal_arr_expand(fulfilled_htlcs, f);
	tal_arr_expand(fulfilled_sides, side);
}

static void add_fail(u64 id, enum side side,
		     enum onion_type failcode,
		     const struct short_channel_id *failing_channel,
		     const u8 *failuremsg,
		     const struct failed_htlc ***failed_htlcs,
		     enum side **failed_sides)
{
	struct failed_htlc *newf;

	newf = tal(*failed_htlcs, struct failed_htlc);
	newf->id = id;
	newf->failcode = failcode;
	if (failcode & UPDATE) {
		assert(failing_channel);
		newf->scid = tal_dup(newf, struct short_channel_id,
				     failing_channel);
	} else
		newf->scid = NULL;

	if (failuremsg)
		newf->failreason
			= tal_dup_arr(newf, u8, failuremsg, tal_count(failuremsg), 0);
	else
		newf->failreason = NULL;

	tal_arr_expand(failed_htlcs, newf);
	tal_arr_expand(failed_sides, side);
}

/* FIXME: Load direct from db. */
void peer_htlcs(const tal_t *ctx,
		const struct channel *channel,
		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 htlc_in_map_iter ini;
	struct htlc_out_map_iter outi;
	struct htlc_in *hin;
	struct htlc_out *hout;
	struct lightningd *ld = channel->peer->ld;

	*htlcs = tal_arr(ctx, struct added_htlc, 0);
	*htlc_states = tal_arr(ctx, enum htlc_state, 0);
	*fulfilled_htlcs = tal_arr(ctx, struct fulfilled_htlc, 0);
	*fulfilled_sides = tal_arr(ctx, enum side, 0);
	*failed_htlcs = tal_arr(ctx, const struct failed_htlc *, 0);
	*failed_sides = tal_arr(ctx, enum side, 0);

	for (hin = htlc_in_map_first(&ld->htlcs_in, &ini);
	     hin;
	     hin = htlc_in_map_next(&ld->htlcs_in, &ini)) {
		if (hin->key.channel != channel)
			continue;

		add_htlc(htlcs, htlc_states,
			 hin->key.id, hin->msat, &hin->payment_hash,
			 hin->cltv_expiry, hin->onion_routing_packet,
			 hin->hstate);

		if (hin->failuremsg || hin->failcode)
			add_fail(hin->key.id, REMOTE, hin->failcode,
				 &hin->failoutchannel,
				 hin->failuremsg, failed_htlcs, failed_sides);
		if (hin->preimage)
			add_fulfill(hin->key.id, REMOTE, hin->preimage,
				    fulfilled_htlcs, fulfilled_sides);
	}

	for (hout = htlc_out_map_first(&ld->htlcs_out, &outi);
	     hout;
	     hout = htlc_out_map_next(&ld->htlcs_out, &outi)) {
		if (hout->key.channel != channel)
			continue;

		add_htlc(htlcs, htlc_states,
			 hout->key.id, hout->msat, &hout->payment_hash,
			 hout->cltv_expiry, hout->onion_routing_packet,
			 hout->hstate);

		if (hout->failuremsg || hout->failcode)
			add_fail(hout->key.id, LOCAL, hout->failcode,
				 hout->key.channel->scid,
				 hout->failuremsg, failed_htlcs, failed_sides);
		if (hout->preimage)
			add_fulfill(hout->key.id, LOCAL, hout->preimage,
				    fulfilled_htlcs, fulfilled_sides);
	}
}

/* If channel is NULL, free them all (for shutdown) */
void free_htlcs(struct lightningd *ld, const struct channel *channel)
{
	struct htlc_out_map_iter outi;
	struct htlc_out *hout;
	struct htlc_in_map_iter ini;
	struct htlc_in *hin;
	bool deleted;

	/* FIXME: Implement check_htlcs to ensure no dangling hout->in ptrs! */

	do {
		deleted = false;
		for (hout = htlc_out_map_first(&ld->htlcs_out, &outi);
		     hout;
		     hout = htlc_out_map_next(&ld->htlcs_out, &outi)) {
			if (channel && hout->key.channel != channel)
				continue;
			tal_free(hout);
			deleted = true;
		}

		for (hin = htlc_in_map_first(&ld->htlcs_in, &ini);
		     hin;
		     hin = htlc_in_map_next(&ld->htlcs_in, &ini)) {
			if (channel && hin->key.channel != channel)
				continue;
			tal_free(hin);
			deleted = true;
		}
		/* Can skip over elements due to iterating while deleting. */
	} while (deleted);
}

/* BOLT #2:
 *
 * 2. the deadline for offered HTLCs: the deadline after which the channel has
 *    to be failed and timed out on-chain. This is `G` blocks after the HTLC's
 *    `cltv_expiry`: 1 block is reasonable.
 */
static u32 htlc_out_deadline(const struct htlc_out *hout)
{
	return hout->cltv_expiry + 1;
}

/* BOLT #2:
 *
 * 3. the deadline for received HTLCs this node has fulfilled: the deadline
 * after which the channel has to be failed and the HTLC fulfilled on-chain
 * before its `cltv_expiry`. See steps 4-7 above, which imply a deadline of
 * `2R+G+S` blocks before `cltv_expiry`: 7 blocks is reasonable.
 */
/* We approximate this, by using half the cltv_expiry_delta (3R+2G+2S),
 * rounded up. */
static u32 htlc_in_deadline(const struct lightningd *ld,
			    const struct htlc_in *hin)
{
	return hin->cltv_expiry - (ld->config.cltv_expiry_delta + 1)/2;
}

void htlcs_notify_new_block(struct lightningd *ld, u32 height)
{
	bool removed;

	/* BOLT #2:
	 *
	 *   - if an HTLC which it offered is in either node's current
	 *   commitment transaction, AND is past this timeout deadline:
	 *     - MUST fail the channel.
	 */
	/* FIXME: use db to look this up in one go (earliest deadline per-peer) */
	do {
		struct htlc_out *hout;
		struct htlc_out_map_iter outi;

		removed = false;

		for (hout = htlc_out_map_first(&ld->htlcs_out, &outi);
		     hout;
		     hout = htlc_out_map_next(&ld->htlcs_out, &outi)) {
			/* Not timed out yet? */
			if (height < htlc_out_deadline(hout))
				continue;

			/* Peer on chain already? */
			if (channel_on_chain(hout->key.channel))
				continue;

			/* Peer already failed, or we hit it? */
			if (hout->key.channel->error)
				continue;

			channel_fail_permanent(hout->key.channel,
					    "Offered HTLC %"PRIu64
					    " %s cltv %u hit deadline",
					    hout->key.id,
					    htlc_state_name(hout->hstate),
					    hout->cltv_expiry);
			removed = true;
		}
	/* Iteration while removing is safe, but can skip entries! */
	} while (removed);


	/* BOLT #2:
	 *
	 *   - for each HTLC it is attempting to fulfill:
	 *     - MUST estimate a fulfillment deadline.
	 *...
	 *   - if an HTLC it has fulfilled is in either node's current commitment
	 *   transaction, AND is past this fulfillment deadline:
	 *     - MUST fail the channel.
	 */
	do {
		struct htlc_in *hin;
		struct htlc_in_map_iter ini;

		removed = false;

		for (hin = htlc_in_map_first(&ld->htlcs_in, &ini);
		     hin;
		     hin = htlc_in_map_next(&ld->htlcs_in, &ini)) {
			struct channel *channel = hin->key.channel;

			/* Not fulfilled?  If overdue, that's their problem... */
			if (!hin->preimage)
				continue;

			/* Not timed out yet? */
			if (height < htlc_in_deadline(ld, hin))
				continue;

			/* Peer on chain already? */
			if (channel_on_chain(channel))
				continue;

			/* Peer already failed, or we hit it? */
			if (channel->error)
				continue;

			channel_fail_permanent(channel,
					    "Fulfilled HTLC %"PRIu64
					    " %s cltv %u hit deadline",
					    hin->key.id,
					    htlc_state_name(hin->hstate),
					    hin->cltv_expiry);
			removed = true;
		}
	/* Iteration while removing is safe, but can skip entries! */
	} while (removed);
}

#ifdef COMPAT_V061
static void fixup_hout(struct lightningd *ld, struct htlc_out *hout)
{
	const char *fix;

	/* We didn't save HTLC failure information to the database.  So when
	 * busy nodes restarted (y'know, our most important users!) they would
	 * find themselves with missing fields.
	 *
	 * Fortunately, most of the network is honest: re-sending an old HTLC
	 * just causes failure (though we assert() when we try to push the
	 * failure to the incoming HTLC which has already succeeded!).
	 */

	/* We care about HTLCs being removed only, not those being added. */
	if (hout->hstate < RCVD_REMOVE_HTLC)
		return;

	/* Successful ones are fine. */
	if (hout->preimage)
		return;

	/* Failed ones (only happens after db fixed!) OK. */
	if (hout->failcode || hout->failuremsg)
		return;

	/* payment_preimage for HTLC in *was* stored, so look for that. */
	if (hout->in && hout->in->preimage) {
		hout->preimage = tal_dup(hout, struct preimage,
					 hout->in->preimage);
		fix = "restoring preimage from incoming HTLC";
	} else {
		hout->failcode = WIRE_TEMPORARY_CHANNEL_FAILURE;
		fix = "subsituting temporary channel failure";
	}

	log_broken(ld->log, "HTLC #%"PRIu64" (%s) "
		   " for amount %s"
		   " to %s"
		   " is missing a resolution: %s.",
		   hout->key.id, htlc_state_name(hout->hstate),
		   type_to_string(tmpctx, struct amount_msat, &hout->msat),
		   type_to_string(tmpctx, struct node_id,
				  &hout->key.channel->peer->id),
		   fix);
}
#endif /* COMPAT_V061 */

/**
 * htlcs_reconnect -- Link outgoing HTLCs to their origins after initial db load
 *
 * For each outgoing HTLC find the incoming HTLC that triggered it. If
 * we are the origin of the transfer then we cannot resolve the
 * incoming HTLC in which case we just leave it `NULL`.
 *
 * Returns a map of any htlcs we need to retry.
 */
struct htlc_in_map *htlcs_reconnect(struct lightningd *ld,
				    struct htlc_in_map *htlcs_in,
				    struct htlc_out_map *htlcs_out)
{
	struct htlc_in_map_iter ini;
	struct htlc_out_map_iter outi;
	struct htlc_in *hin;
	struct htlc_out *hout;
	struct htlc_in_map *unprocessed = tal(NULL, struct htlc_in_map);

	/* Any HTLCs which happened to be incoming and weren't forwarded before
	 * we shutdown/crashed: fail them now.
	 *
	 * Note that since we do local processing synchronously, so this never
	 * captures local payments.  But if it did, it would be a tiny corner
	 * case. */
	htlc_in_map_init(unprocessed);
	for (hin = htlc_in_map_first(htlcs_in, &ini); hin;
	     hin = htlc_in_map_next(htlcs_in, &ini)) {
		if (hin->hstate == RCVD_ADD_ACK_REVOCATION)
			htlc_in_map_add(unprocessed, hin);
	}

	for (hout = htlc_out_map_first(htlcs_out, &outi); hout;
	     hout = htlc_out_map_next(htlcs_out, &outi)) {

		if (hout->am_origin) {
			continue;
		}

		/* For fulfilled HTLCs, we fulfill incoming before outgoing is
		 * completely resolved, so it's possible that we don't find
		 * the incoming. */
		for (hin = htlc_in_map_first(htlcs_in, &ini); hin;
		     hin = htlc_in_map_next(htlcs_in, &ini)) {
			if (hout->origin_htlc_id == hin->dbid) {
				log_debug(ld->log,
					  "Found corresponding htlc_in %" PRIu64
					  " for htlc_out %" PRIu64,
					  hin->dbid, hout->dbid);
				htlc_out_connect_htlc_in(hout, hin);
				break;
			}
		}

		if (!hout->in && !hout->preimage) {
#ifdef COMPAT_V061
			log_broken(ld->log,
				   "Missing preimage for orphaned HTLC; replacing with zeros");
			hout->preimage = talz(hout, struct preimage);
#else
			fatal("Unable to find corresponding htlc_in %"PRIu64
			      " for unfulfilled htlc_out %"PRIu64,
			      hout->origin_htlc_id, hout->dbid);
#endif
		}
#ifdef COMPAT_V061
		fixup_hout(ld, hout);
#endif

		if (hout->in)
			htlc_in_map_del(unprocessed, hout->in);
	}

	return unprocessed;
}

void htlcs_resubmit(struct lightningd *ld, struct htlc_in_map *unprocessed)
{
	struct htlc_in *hin;
	struct htlc_in_map_iter ini;
	enum onion_type failcode COMPILER_WANTS_INIT("gcc7.4.0 bad, 8.3 OK");

	/* Now fail any which were stuck. */
	for (hin = htlc_in_map_first(unprocessed, &ini);
	     hin;
	     hin = htlc_in_map_next(unprocessed, &ini)) {
		log_unusual(hin->key.channel->log,
			    "Replaying old unprocessed HTLC #%"PRIu64,
			    hin->key.id);
		if (!peer_accepted_htlc(hin->key.channel, hin->key.id, true, &failcode)) {
			fail_in_htlc(hin,
				     failcode != 0
					 ? failcode
					 : WIRE_TEMPORARY_NODE_FAILURE,
				     NULL, NULL);
		}  else if (failcode) {
			fail_in_htlc(hin, failcode, NULL, NULL);
		}
	}

	/* Don't leak memory! */
	htlc_in_map_clear(unprocessed);
	tal_free(unprocessed);
}

#if DEVELOPER
static struct command_result *json_dev_ignore_htlcs(struct command *cmd,
						    const char *buffer,
						    const jsmntok_t *obj UNNEEDED,
						    const jsmntok_t *params)
{
	struct node_id *peerid;
	struct peer *peer;
	bool *ignore;

	if (!param(cmd, buffer, params,
		   p_req("id", param_node_id, &peerid),
		   p_req("ignore", param_bool, &ignore),
		   NULL))
		return command_param_failed();

	peer = peer_by_id(cmd->ld, peerid);
	if (!peer) {
		return command_fail(cmd, LIGHTNINGD,
				    "Could not find channel with that peer");
	}
	peer->ignore_htlcs = *ignore;

	return command_success(cmd, json_stream_success(cmd));
}

static const struct json_command dev_ignore_htlcs = {
	"dev-ignore-htlcs",
	"developer",
	json_dev_ignore_htlcs,
	"Set ignoring incoming HTLCs for peer {id} to {ignore}", false,
	"Set/unset ignoring of all incoming HTLCs.  For testing only."
};
AUTODATA(json_command, &dev_ignore_htlcs);
#endif /* DEVELOPER */

/* Warp this process to ensure the consistent json object structure
 * between 'listforwards' API and 'forward_event' notification. */
void json_format_forwarding_object(struct json_stream *response,
				   const char *fieldname,
				   const struct forwarding *cur)
{
	json_object_start(response, fieldname);

	/* See 6d333f16cc0f3aac7097269bf0985b5fa06d59b4: we may have deleted HTLC. */
	if (cur->payment_hash)
		json_add_sha256(response, "payment_hash", cur->payment_hash);
	json_add_short_channel_id(response, "in_channel", &cur->channel_in);

	/* This can be unknown if we failed before channel lookup */
	if (cur->channel_out.u64 != 0 || deprecated_apis)
		json_add_short_channel_id(response, "out_channel",
					  &cur->channel_out);
	json_add_amount_msat_compat(response,
				    cur->msat_in,
				    "in_msatoshi", "in_msat");

	/* These can be unset (aka zero) if we failed before channel lookup */
	if (cur->channel_out.u64 != 0 || deprecated_apis) {
		json_add_amount_msat_compat(response,
					    cur->msat_out,
					    "out_msatoshi",  "out_msat");
		json_add_amount_msat_compat(response,
					    cur->fee,
					    "fee", "fee_msat");
	}
	json_add_string(response, "status", forward_status_name(cur->status));

	if(cur->failcode != 0) {
		json_add_num(response, "failcode", cur->failcode);
		json_add_string(response, "failreason",
				onion_type_name(cur->failcode));
	}

#ifdef COMPAT_V070
		/* If a forwarding doesn't have received_time it was created
		 * before we added the tracking, do not include it here. */
	if (cur->received_time.ts.tv_sec) {
		json_add_timeabs(response, "received_time", cur->received_time);
		if (cur->resolved_time)
			json_add_timeabs(response, "resolved_time", *cur->resolved_time);
	}
#else
	json_add_timeabs(response, "received_time", cur->received_time);
	if (cur->resolved_time)
		json_add_timeabs(response, "resolved_time", *cur->resolved_time);
#endif
	json_object_end(response);
}


static void listforwardings_add_forwardings(struct json_stream *response, struct wallet *wallet)
{
	const struct forwarding *forwardings;
	forwardings = wallet_forwarded_payments_get(wallet, tmpctx);

	json_array_start(response, "forwards");
	for (size_t i=0; i<tal_count(forwardings); i++) {
		const struct forwarding *cur = &forwardings[i];
		json_format_forwarding_object(response, NULL, cur);
	}
	json_array_end(response);

	tal_free(forwardings);
}

static struct command_result *json_listforwards(struct command *cmd,
						const char *buffer,
						const jsmntok_t *obj UNNEEDED,
						const jsmntok_t *params)
{
	struct json_stream *response;

	if (!param(cmd, buffer, params, NULL))
		return command_param_failed();

	response = json_stream_success(cmd);
	listforwardings_add_forwardings(response, cmd->ld->wallet);

	return command_success(cmd, response);
}

static const struct json_command listforwards_command = {
	"listforwards",
	"channels",
	json_listforwards,
	"List all forwarded payments and their information", false,
	"List all forwarded payments and their information"
};
AUTODATA(json_command, &listforwards_command);