lightning/lightningd/peer_htlcs.c

#include <ccan/build_assert/build_assert.h>
#include <ccan/mem/mem.h>
#include <daemon/chaintopology.h>
#include <daemon/invoice.h>
#include <daemon/log.h>
#include <lightningd/channel/gen_channel_wire.h>
#include <lightningd/gossip/gen_gossip_wire.h>
#include <lightningd/htlc_end.h>
#include <lightningd/htlc_wire.h>
#include <lightningd/lightningd.h>
#include <lightningd/pay.h>
#include <lightningd/peer_control.h>
#include <lightningd/peer_htlcs.h>
#include <lightningd/sphinx.h>
#include <lightningd/subd.h>
#include <overflows.h>
#include <wire/gen_onion_wire.h>

/* This is where we write to the database the minimal HTLC info
 * required to do penalty transaction */
static void save_htlc_stub(struct lightningd *ld,
			   struct peer *peer,
			   enum htlc_end_type htlc_end_type,
			   u32 cltv_value,
			   const struct sha256 *payment_hash)
{
	/* FIXME: remember peer, direction, cltv and RIPEMD160(hash) */
}

/* This obfuscates the message, whether local or forwarded. */
static void relay_htlc_failmsg(struct htlc_end *hend)
{
	u8 *reply;

	if (!hend->peer->owner)
		return;

	reply = wrap_onionreply(hend, hend->shared_secret, hend->fail_msg);
	subd_send_msg(hend->peer->owner,
		      take(towire_channel_fail_htlc(hend, hend->htlc_id, reply)));
	tal_free(reply);
}

static u8 *make_failmsg(const tal_t *ctx, const struct htlc_end *hend,
			enum onion_type failcode,
			const struct sha256 *onion_sha, const u8 *channel_update)
{
	switch (failcode) {
	case WIRE_INVALID_REALM:
		return towire_invalid_realm(ctx);
	case WIRE_TEMPORARY_NODE_FAILURE:
		return towire_temporary_node_failure(ctx);
	case WIRE_PERMANENT_NODE_FAILURE:
		return towire_permanent_node_failure(ctx);
	case WIRE_REQUIRED_NODE_FEATURE_MISSING:
		return towire_required_node_feature_missing(ctx);
	case WIRE_INVALID_ONION_VERSION:
		return towire_invalid_onion_version(ctx, onion_sha);
	case WIRE_INVALID_ONION_HMAC:
		return towire_invalid_onion_hmac(ctx, onion_sha);
	case WIRE_INVALID_ONION_KEY:
		return towire_invalid_onion_key(ctx, onion_sha);
	case WIRE_TEMPORARY_CHANNEL_FAILURE:
		return towire_temporary_channel_failure(ctx, channel_update);
	case WIRE_CHANNEL_DISABLED:
		return towire_channel_disabled(ctx);
	case WIRE_PERMANENT_CHANNEL_FAILURE:
		return towire_permanent_channel_failure(ctx);
	case WIRE_REQUIRED_CHANNEL_FEATURE_MISSING:
		return towire_required_channel_feature_missing(ctx);
	case WIRE_UNKNOWN_NEXT_PEER:
		return towire_unknown_next_peer(ctx);
	case WIRE_AMOUNT_BELOW_MINIMUM:
		return towire_amount_below_minimum(ctx, hend->msatoshis, channel_update);
	case WIRE_FEE_INSUFFICIENT:
		return towire_fee_insufficient(ctx, hend->msatoshis, channel_update);
	case WIRE_INCORRECT_CLTV_EXPIRY:
		/* FIXME: ctlv! */
		return towire_incorrect_cltv_expiry(ctx, 0, channel_update);
	case WIRE_EXPIRY_TOO_SOON:
		return towire_expiry_too_soon(ctx, channel_update);
	case WIRE_UNKNOWN_PAYMENT_HASH:
		return towire_unknown_payment_hash(ctx);
	case WIRE_INCORRECT_PAYMENT_AMOUNT:
		return towire_incorrect_payment_amount(ctx);
	case WIRE_FINAL_EXPIRY_TOO_SOON:
		return towire_final_expiry_too_soon(ctx);
	case WIRE_FINAL_INCORRECT_CLTV_EXPIRY:
		/* FIXME: ctlv! */
		return towire_final_incorrect_cltv_expiry(ctx, 0);
	case WIRE_FINAL_INCORRECT_HTLC_AMOUNT:
		return towire_final_incorrect_htlc_amount(ctx, hend->msatoshis);
	}
	abort();
}

static void fail_htlc(struct htlc_end *hend, enum onion_type failcode,
		      const struct sha256 *onion_sha)
{
	u8 *msg;

	log_broken(hend->peer->log, "failed htlc %"PRIu64" code 0x%04x (%s)",
		   hend->htlc_id, failcode, onion_type_name(failcode));

	if (failcode & UPDATE) {
		/* FIXME: Ask gossip daemon for channel_update. */
	}

	msg = make_failmsg(hend, hend, failcode, onion_sha, NULL);
	hend->fail_msg = create_onionreply(hend, hend->shared_secret, msg);
	tal_free(msg);

	relay_htlc_failmsg(hend);
}

/* BOLT #4:
 *
 * * `amt_to_forward` - The amount in milli-satoshi to forward to the next
 *    (outgoing) hop specified within the routing information.
 *
 *    This value MUST factor in the computed fee for this particular hop. When
 *    processing an incoming Sphinx packet along with the HTLC message it's
 *    encapsulated within, if the following inequality doesn't hold, then the
 *    HTLC should be rejected as it indicates a prior node in the path has
 *    deviated from the specified parameters:
 *
 *       incoming_htlc_amt - fee >= amt_to_forward
 *
 *    Where `fee` is calculated according to the receiving node's advertised fee
 *    schema as described in [BOLT 7](https://github.com/lightningnetwork/lightning-rfc/blob/master/07-routing-gossip.md#htlc-fees), or 0 if this node is the
 *    final hop.
 */
static bool check_amount(struct htlc_end *hend,
			 u64 amt_to_forward, u64 amt_in_htlc, u64 fee)
{
	if (amt_in_htlc - fee >= amt_to_forward)
		return true;
	log_debug(hend->peer->ld->log, "HTLC %"PRIu64" incorrect amount:"
		  " %"PRIu64" in, %"PRIu64" out, fee reqd %"PRIu64,
		  hend->htlc_id, amt_in_htlc, amt_to_forward, 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 node to both authenticate the information
 *     specified by the original sender and the parameters of the HTLC forwarded,
 *	 and ensure the original sender is using the current `cltv_expiry_delta`  value.
 *     If there is no next hop, `cltv_expiry_delta` is zero.
 *     If the values don't correspond, then the HTLC should be failed+rejected as
 *     this indicates the incoming node has tampered with the intended HTLC
 *     values, or the origin has an obsolete `cltv_expiry_delta` value.
 *     The node MUST be consistent in responding to an unexpected
 *     `outgoing_cltv_value` whether it is the final hop or not, to avoid
 *     leaking that information.
 */
static bool check_ctlv(struct htlc_end *hend,
		       u32 ctlv_expiry, u32 outgoing_cltv_value, u32 delta)
{
	if (ctlv_expiry - delta == outgoing_cltv_value)
		return true;
	log_debug(hend->peer->ld->log, "HTLC %"PRIu64" incorrect CLTV:"
		  " %u in, %u out, delta reqd %u",
		  hend->htlc_id, ctlv_expiry, outgoing_cltv_value, delta);
	return false;
}

static void fulfill_htlc(struct htlc_end *hend, const struct preimage *preimage)
{
	u8 *msg;

	hend->peer->balance[LOCAL] += hend->msatoshis;
	hend->peer->balance[REMOTE] -= hend->msatoshis;

	/* FIXME: fail the peer if it doesn't tell us that htlc fulfill is
	 * committed before deadline.
	 */
	msg = towire_channel_fulfill_htlc(hend->peer, hend->htlc_id, preimage);
	subd_send_msg(hend->peer->owner, take(msg));
}

static void handle_localpay(struct htlc_end *hend,
			    u32 cltv_expiry,
			    const struct sha256 *payment_hash,
			    u64 amt_to_forward,
			    u32 outgoing_cltv_value)
{
	enum onion_type failcode;
	struct invoice *invoice;

	/* BOLT #4:
	 *
	 * If the `amt_to_forward` is higher than `incoming_htlc_amt` of
	 * the HTLC at the final hop:
	 *
	 * 1. type: 19 (`final_incorrect_htlc_amount`)
	 * 2. data:
	 *    * [`4`:`incoming_htlc_amt`]
	 */
	if (!check_amount(hend, amt_to_forward, hend->msatoshis, 0)) {
		failcode = WIRE_FINAL_INCORRECT_HTLC_AMOUNT;
		goto fail;
	}

	/* BOLT #4:
	 *
	 * If the `outgoing_cltv_value` does not match the `ctlv_expiry` of
	 * the HTLC at the final hop:
	 *
	 * 1. type: 18 (`final_incorrect_cltv_expiry`)
	 * 2. data:
	 *   * [`4`:`cltv_expiry`]
	 */
	if (!check_ctlv(hend, cltv_expiry, outgoing_cltv_value, 0)) {
		failcode = WIRE_FINAL_INCORRECT_CLTV_EXPIRY;
		goto fail;
	}

	invoice = find_unpaid(hend->peer->ld->dstate.invoices, payment_hash);
	if (!invoice) {
		failcode = WIRE_UNKNOWN_PAYMENT_HASH;
		goto fail;
	}

	/* BOLT #4:
	 *
	 * If the amount paid is less than the amount expected, the final node
	 * MUST fail the HTLC.  If the amount paid is more than twice the
	 * amount expected, the final node SHOULD fail the HTLC.  This allows
	 * the sender to reduce information leakage by altering the amount,
	 * without allowing accidental gross overpayment:
	 *
	 * 1. type: PERM|16 (`incorrect_payment_amount`)
	 */
	if (hend->msatoshis < invoice->msatoshi) {
		failcode = WIRE_INCORRECT_PAYMENT_AMOUNT;
		goto fail;
	} else if (hend->msatoshis > invoice->msatoshi * 2) {
		failcode = WIRE_INCORRECT_PAYMENT_AMOUNT;
		goto fail;
	}

	/* BOLT #4:
	 *
	 * If the `cltv_expiry` is too low, the final node MUST fail the HTLC:
	 */
	if (get_block_height(hend->peer->ld->topology)
	    + hend->peer->ld->dstate.config.deadline_blocks >= cltv_expiry) {
		log_debug(hend->peer->log,
			  "Expiry cltv %u too close to current %u + deadline %u",
			  cltv_expiry,
			  get_block_height(hend->peer->ld->topology),
			  hend->peer->ld->dstate.config.deadline_blocks);
		failcode = WIRE_FINAL_EXPIRY_TOO_SOON;
		goto fail;
	}

	log_info(hend->peer->ld->log, "Resolving invoice '%s' with HTLC %"PRIu64,
		 invoice->label, hend->htlc_id);
	fulfill_htlc(hend, &invoice->r);
	resolve_invoice(&hend->peer->ld->dstate, invoice);
	return;

fail:
	fail_htlc(hend, failcode, NULL);
}

/*
 * 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 hend_subd_died(struct htlc_end *hend)
{
	log_debug(hend->other_end->peer->owner->log,
		  "Failing HTLC %"PRIu64" due to peer death",
		  hend->other_end->htlc_id);

	fail_htlc(hend->other_end, WIRE_TEMPORARY_CHANNEL_FAILURE, NULL);
}

/* This is where channeld gives us the HTLC id, and also reports if it
 * failed immediately. */
static bool rcvd_htlc_reply(struct subd *subd, const u8 *msg, const int *fds,
			    struct htlc_end *hend)
{
	u16 failure_code;
	u8 *failurestr;

	if (!fromwire_channel_offer_htlc_reply(msg, msg, NULL,
					       &hend->htlc_id,
					       &failure_code,
					       &failurestr)) {
		log_broken(subd->log, "Bad channel_offer_htlc_reply");
		tal_free(hend);
		return false;
	}

	if (failure_code) {
		log_debug(hend->other_end->peer->owner->log,
			  "HTLC failed from other daemon: %s (%.*s)",
			  onion_type_name(failure_code),
			  (int)tal_len(failurestr), (char *)failurestr);

		fail_htlc(hend->other_end, failure_code, NULL);
		return true;
	}

	/* Add it to lookup table now we know id. */
	connect_htlc_end(&subd->ld->htlc_ends, hend);

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

static void forward_htlc(struct htlc_end *hend,
			 u32 cltv_expiry,
			 const struct sha256 *payment_hash,
			 u64 amt_to_forward,
			 u32 outgoing_cltv_value,
			 const struct pubkey *next_hop,
			 const u8 next_onion[TOTAL_PACKET_SIZE])
{
	u8 *msg;
	enum onion_type failcode;
	u64 fee;
	struct lightningd *ld = hend->peer->ld;
	struct peer *next = peer_by_id(ld, next_hop);

	if (!next) {
		failcode = WIRE_UNKNOWN_NEXT_PEER;
		goto fail;
	}

	if (!peer_can_add_htlc(next)) {
		log_info(next->log, "Attempt to forward HTLC but not ready (%s)",
			 peer_state_name(next->state));
		failcode = WIRE_UNKNOWN_NEXT_PEER;
		goto fail;
	}

	if (!next->owner) {
		log_info(next->log, "Attempt to forward HTLC but unowned (%s)",
			peer_state_name(next->state));
		failcode = WIRE_TEMPORARY_CHANNEL_FAILURE;
		goto fail;
	}

	/* BOLT #7:
	 *
	 * The node creating `channel_update` SHOULD accept HTLCs which pay a
	 * fee equal or greater than:
	 *
	 *    fee_base_msat + amount_msat * fee_proportional_millionths / 1000000
	 */
	if (mul_overflows_u64(amt_to_forward,
			      ld->dstate.config.fee_per_satoshi)) {
		failcode = WIRE_FEE_INSUFFICIENT;
		goto fail;
	}
	fee = ld->dstate.config.fee_base
		+ amt_to_forward * ld->dstate.config.fee_per_satoshi / 1000000;
	if (!check_amount(hend, amt_to_forward, hend->msatoshis, fee)) {
		failcode = WIRE_FEE_INSUFFICIENT;
		goto fail;
	}

	if (!check_ctlv(hend, cltv_expiry, outgoing_cltv_value,
			ld->dstate.config.deadline_blocks)) {
		failcode = WIRE_INCORRECT_CLTV_EXPIRY;
		goto fail;
	}

	/* BOLT #4:
	 *
	 * If the ctlv-expiry is too near, we tell them the the current channel
	 * setting for the outgoing channel:
	 * 1. type: UPDATE|14 (`expiry_too_soon`)
	 * 2. data:
	 *    * [`2`:`len`]
	 *    * [`len`:`channel_update`]
	 */
	if (get_block_height(next->ld->topology)
	    + next->ld->dstate.config.deadline_blocks >= outgoing_cltv_value) {
		log_debug(hend->peer->log,
			  "Expiry cltv %u too close to current %u + deadline %u",
			  outgoing_cltv_value,
			  get_block_height(next->ld->topology),
			  next->ld->dstate.config.deadline_blocks);
		failcode = WIRE_EXPIRY_TOO_SOON;
		goto fail;
	}

	/* Make sure daemon owns it, in case it fails. */
	hend->other_end = tal(next->owner, struct htlc_end);
	hend->other_end->hstate = SENT_ADD_HTLC;
	hend->other_end->which_end = HTLC_DST;
	hend->other_end->peer = next;
	hend->other_end->other_end = hend;
	hend->other_end->pay_command = NULL;
	hend->other_end->msatoshis = amt_to_forward;
	hend->other_end->outgoing_cltv_value = outgoing_cltv_value;
	hend->other_end->payment_hash = hend->payment_hash;
	tal_add_destructor(hend->other_end, hend_subd_died);

	msg = towire_channel_offer_htlc(next, amt_to_forward,
					outgoing_cltv_value,
					payment_hash, next_onion);
	subd_req(next->owner, next->owner, take(msg), -1, 0,
		 rcvd_htlc_reply, hend->other_end);
	return;

fail:
	fail_htlc(hend, failcode, NULL);
}

/* We received a resolver reply, which gives us the node_ids of the
 * channel we want to forward over */
static bool channel_resolve_reply(struct subd *gossip, const u8 *msg,
				  const int *fds, struct htlc_end *hend)
{
	struct pubkey *nodes, *peer_id;

	if (!fromwire_gossip_resolve_channel_reply(msg, msg, NULL, &nodes)) {
		log_broken(gossip->log,
			   "bad fromwire_gossip_resolve_channel_reply %s",
			   tal_hex(msg, msg));
		return false;
	}

	if (tal_count(nodes) == 0) {
		fail_htlc(hend, WIRE_UNKNOWN_NEXT_PEER, NULL);
		return true;
	} else if (tal_count(nodes) != 2) {
		log_broken(gossip->log,
			   "fromwire_gossip_resolve_channel_reply has %zu nodes",
			   tal_count(nodes));
		return false;
	}

	/* Get the other peer matching the id that is not us */
	if (pubkey_cmp(&nodes[0], &gossip->ld->dstate.id) == 0) {
		peer_id = &nodes[1];
	} else {
		peer_id = &nodes[0];
	}

	forward_htlc(hend, hend->cltv_expiry, &hend->payment_hash,
		     hend->amt_to_forward, hend->outgoing_cltv_value, peer_id,
		     hend->next_onion);
	/* FIXME(cdecker) Cleanup things we stuffed into hend before (maybe?) */
	return true;
}

static bool hend_update_state(struct peer *peer,
			      struct htlc_end *hend,
			      enum htlc_state newstate)
{
	enum htlc_state expected = hend->hstate + 1;

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

	if (newstate != expected) {
		log_broken(peer->log, "HTLC %"PRIu64" invalid update %s->%s",
			   hend->htlc_id,
			   htlc_state_name(hend->hstate),
			   htlc_state_name(newstate));
		return false;
	}

	log_debug(peer->log, "%s HTLC %"PRIu64" %s->%s",
		  hend->which_end == HTLC_SRC ? "Their" : "Our",
		  hend->htlc_id,
		  htlc_state_name(hend->hstate),
		  htlc_state_name(newstate));

	/* FIXME: db commit */
	hend->hstate = newstate;
	return true;
}

/* Everyone is committed to this htlc of theirs */
static bool peer_accepted_htlc(struct peer *peer,
			       u64 id,
			       const struct secret *shared_secret,
			       enum onion_type *failcode)
{
	struct htlc_end *hend;
	u8 *req;
	struct route_step *rs;
	struct onionpacket *op;
	const tal_t *tmpctx = tal_tmpctx(peer);

	hend = find_htlc_end(&peer->ld->htlc_ends, peer, id, HTLC_SRC);
	if (!hend) {
		log_broken(peer->log,
			   "peer_got_revoke unknown htlc %"PRIu64, id);
		return false;
	}

	if (!hend_update_state(peer, hend, RCVD_ADD_ACK_REVOCATION))
		return false;

	/* channeld tests this, so it should have set ss to zeroes. */
	op = parse_onionpacket(tmpctx, hend->next_onion,
			       tal_len(hend->next_onion));
	if (!op) {
		if (!memeqzero(shared_secret, sizeof(*shared_secret))) {
			log_broken(peer->log,
				   "bad onion in got_revoke: %s",
				   tal_hex(peer, hend->next_onion));
			tal_free(tmpctx);
			return false;
		}
		/* FIXME: could be bad version, bad key. */
		*failcode = WIRE_INVALID_ONION_VERSION;
		goto out;
	}

	/* Channeld sets this to zero if HSM won't ecdh it */
	if (memeqzero(shared_secret, sizeof(*shared_secret))) {
		*failcode = WIRE_INVALID_ONION_KEY;
		goto out;
	}

	hend->shared_secret = tal_dup(hend, struct secret, shared_secret);

	/* If it's crap, not channeld's fault, just fail it */
	rs = process_onionpacket(tmpctx, op, hend->shared_secret->data,
				 hend->payment_hash.u.u8,
				 sizeof(hend->payment_hash));
	if (!rs) {
		*failcode = WIRE_INVALID_ONION_HMAC;
		goto out;
	}

	/* Unknown realm isn't a bad onion, it's a normal failure. */
	if (rs->hop_data.realm != 0) {
		*failcode = WIRE_INVALID_REALM;
		goto out;
	}

	hend->amt_to_forward = rs->hop_data.amt_forward;
	hend->outgoing_cltv_value = rs->hop_data.outgoing_cltv;
	hend->next_channel = rs->hop_data.channel_id;

	if (rs->nextcase == ONION_FORWARD) {
		hend->next_onion = serialize_onionpacket(hend, rs->next);
		req = towire_gossip_resolve_channel_request(tmpctx,
							    &hend->next_channel);
		log_debug(peer->log, "Asking gossip to resolve channel %s",
			  type_to_string(tmpctx, struct short_channel_id,
					 &hend->next_channel));
		subd_req(hend, peer->ld->gossip, req, -1, 0,
			 channel_resolve_reply, hend);
		/* FIXME(cdecker) Stuff all this info into hend */
	} else
		handle_localpay(hend, hend->cltv_expiry, &hend->payment_hash,
				hend->amt_to_forward, hend->outgoing_cltv_value);

	*failcode = 0;
out:
	log_debug(peer->log, "their htlc %"PRIu64" %s",
		  id, *failcode ? onion_type_name(*failcode) : "locked");

	tal_free(tmpctx);
	return true;
}

static bool peer_fulfilled_our_htlc(struct peer *peer,
				    const struct fulfilled_htlc *fulfilled)
{
	struct htlc_end *hend;

	hend = find_htlc_end(&peer->ld->htlc_ends, peer, fulfilled->id,
			     HTLC_DST);
	if (!hend) {
		log_broken(peer->log,
			   "fulfilled_our_htlc unknown htlc %"PRIu64,
			   fulfilled->id);
		return false;
	}

	if (!hend_update_state(peer, hend, RCVD_REMOVE_COMMIT)) 
		return false;

	/* FIXME: Type mismatch. */
	hend->preimage = tal(hend, struct sha256);
	memcpy(hend->preimage, &fulfilled->payment_preimage,
	       sizeof(fulfilled->payment_preimage));
	BUILD_ASSERT(sizeof(*hend->preimage)
		     == sizeof(fulfilled->payment_preimage));

	/* FIXME: Save to db */

	/* They fulfilled our HTLC.  Credit them, forward immediately. */
	peer->balance[REMOTE] += hend->msatoshis;
	peer->balance[LOCAL] -= hend->msatoshis;

	if (hend->other_end)
		fulfill_htlc(hend->other_end, &fulfilled->payment_preimage);
	else
		payment_succeeded(peer->ld, hend, &fulfilled->payment_preimage);
	return true;
}

static bool peer_failed_our_htlc(struct peer *peer,
				 const struct failed_htlc *failed)
{
	struct htlc_end *hend;

	hend = find_htlc_end(&peer->ld->htlc_ends, peer, failed->id, HTLC_DST);
	if (!hend) {
		log_broken(peer->log,
			   "failed_our_htlc unknown htlc %"PRIu64,
			   failed->id);
		return false;
	}

	if (!hend_update_state(peer, hend, RCVD_REMOVE_COMMIT)) 
		return false;

	log_debug(peer->log, "Our HTLC %"PRIu64" failed", failed->id);
	hend->fail_msg = tal_dup_arr(hend, u8, failed->failreason,
				     tal_len(failed->failreason), 0);
	return true;
}


static void remove_hend(struct peer *peer, struct htlc_end *hend)
{
	log_debug(peer->log, "Removing %s hend %"PRIu64" state %s",
		  hend->which_end == HTLC_DST ? "outgoing" : "incoming",
		  hend->htlc_id,
		  htlc_state_name(hend->hstate));

	/* If it's failed, now we can forward since it's completely locked-in */
	if (hend->fail_msg && hend->which_end == HTLC_DST) {
		if (hend->other_end) {
			hend->other_end->fail_msg
				= tal_dup_arr(hend->other_end, u8,
					      hend->fail_msg,
					      tal_len(hend->fail_msg), 0);
			relay_htlc_failmsg(hend->other_end);
		} else {
			/* FIXME: Avoid copy here! */
			enum onion_type failcode;
			struct onionreply *reply;
			size_t numhops = tal_count(hend->path_secrets);
			struct secret *shared_secrets = tal_arr(hend, struct secret, numhops);
			for (size_t i=0; i<numhops; i++) {
				shared_secrets[i] = hend->path_secrets[i];
			}
			reply = unwrap_onionreply(hend, shared_secrets, numhops,
						  hend->fail_msg);
			if (!reply) {
				log_info(peer->log, "htlc %"PRIu64
					 " failed with bad reply (%s)",
					 hend->htlc_id,
					 tal_hex(hend, hend->fail_msg));
				failcode = WIRE_PERMANENT_NODE_FAILURE;
			} else {
				failcode = fromwire_peektype(reply->msg);
				log_info(peer->log, "htlc %"PRIu64
					 " failed from %ith node with code 0x%04x (%s)",
					 hend->htlc_id,
					 reply->origin_index, failcode,
					 onion_type_name(failcode));
			}
			/* FIXME: Apply update if it contains it, etc */
			payment_failed(peer->ld, hend, NULL, failcode);
		}
	}

	tal_free(hend);
}

static bool changed_htlc(struct peer *peer,
			 const struct changed_htlc *changed_htlc)
{
	struct htlc_end *hend;
	enum htlc_end_type end;

	if (htlc_state_owner(changed_htlc->newstate) == LOCAL)
		end = HTLC_DST;
	else
		end = HTLC_SRC;

	hend = find_htlc_end(&peer->ld->htlc_ends, peer, changed_htlc->id, end);
	if (!hend) {
		log_broken(peer->log,
			   "Can't find %s HTLC %"PRIu64,
			   side_to_str(htlc_state_owner(changed_htlc->newstate)),
			   changed_htlc->id);
		return false;
	}

	if (!hend_update_state(peer, hend, changed_htlc->newstate))
		return false;

	/* First transition into commitment; now it outlives peer. */
	if (changed_htlc->newstate == SENT_ADD_COMMIT) {
		tal_del_destructor(hend, hend_subd_died);
		tal_steal(peer->ld, hend);

		/* From now onwards, penalty tx might need this */
		save_htlc_stub(peer->ld, peer, end, hend->outgoing_cltv_value,
			       &hend->payment_hash);
	} else if (changed_htlc->newstate == RCVD_REMOVE_ACK_REVOCATION
		   || changed_htlc->newstate == SENT_REMOVE_ACK_REVOCATION) {
		remove_hend(peer, hend);
	}

	return true;
}

int peer_sending_commitsig(struct peer *peer, const u8 *msg)
{
	u64 commitnum;
	struct changed_htlc *changed_htlcs;
	size_t i;

	if (!fromwire_channel_sending_commitsig(msg, msg, NULL,
						&commitnum,
						&changed_htlcs)) {
		log_broken(peer->log, "bad channel_sending_commitsig %s",
			   tal_hex(peer, msg));
		return -1;
	}

	for (i = 0; i < tal_count(changed_htlcs); i++) {
		if (!changed_htlc(peer, changed_htlcs + i)) {
			log_broken(peer->log,
				   "channel_sending_commitsig: update failed");
			return -1;
		}
	}

	/* Tell it we've got it, and to go ahead with commitment_signed. */
	subd_send_msg(peer->owner,
		      take(towire_channel_sending_commitsig_reply(msg)));
	return 0;
}

static void added_their_htlc(struct peer *peer, const struct added_htlc *added)
{
	struct htlc_end *hend;

	/* This stays around even if we fail it immediately: it *is*
	 * part of the current commitment. */
	hend = tal(peer, struct htlc_end);
	hend->which_end = HTLC_SRC;
	hend->hstate = RCVD_ADD_COMMIT;
	hend->peer = peer;
	hend->other_end = NULL;
	hend->pay_command = NULL;
	hend->fail_msg = NULL;
	hend->htlc_id = added->id;
	hend->msatoshis = added->amount_msat;
	hend->payment_hash = added->payment_hash;
	hend->cltv_expiry = added->cltv_expiry;
	hend->next_onion = tal_dup_arr(hend, u8, added->onion_routing_packet,
				       sizeof(added->onion_routing_packet),
				       0);
	/* FIXME: Save to db */

	log_debug(peer->log, "Adding their HTLC %"PRIu64, added->id);
	connect_htlc_end(&peer->ld->htlc_ends, hend);

	/* Technically this can't be needed for a penalty transaction until
	 * after we send revoke_and_ack, then commit, then receive their
	 * revoke_and_ack.  But might as well record it while we have it:
	 * a few extra entries won't hurt */
	save_htlc_stub(peer->ld, peer, HTLC_SRC, hend->cltv_expiry,
		       &hend->payment_hash);

}

static bool update_by_id(struct peer *peer, u64 id, enum htlc_end_type end,
			 enum htlc_state newstate)
{
	struct htlc_end *hend;

	hend = find_htlc_end(&peer->ld->htlc_ends, peer, id, end);
	if (!hend) {
		log_broken(peer->log, "Could not find id %"PRIu64
			   " to update to %s", id, htlc_state_name(newstate));
		return false;
	}

	return hend_update_state(peer, hend, newstate);
}

/* The peer doesn't tell us this separately, but logically it's a separate
 * step to receiving commitsig */
static bool peer_sending_revocation(struct peer *peer,
				    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_by_id(peer, added[i].id, HTLC_SRC,
				  SENT_ADD_REVOCATION))
			return false;
	}
	for (i = 0; i < tal_count(fulfilled); i++) {
		if (!update_by_id(peer, fulfilled[i].id, HTLC_DST,
				  SENT_REMOVE_REVOCATION))
			return false;
	}
	for (i = 0; i < tal_count(failed); i++) {
		if (!update_by_id(peer, failed[i].id, HTLC_DST,
				  SENT_REMOVE_REVOCATION))
			return false;
	}
	for (i = 0; i < tal_count(changed); i++) {
		if (changed[i].newstate == RCVD_ADD_ACK_COMMIT) {
			if (!update_by_id(peer, changed[i].id, HTLC_DST,
					  SENT_ADD_ACK_REVOCATION))
				return false;
		} else {
			if (!update_by_id(peer, changed[i].id, HTLC_SRC,
					  SENT_REMOVE_ACK_REVOCATION))
				return false;
		}
	}

	return true;
}

/* This also implies we're sending revocation */
int peer_got_commitsig(struct peer *peer, const u8 *msg)
{
	u64 commitnum;
	secp256k1_ecdsa_signature commit_sig;
	secp256k1_ecdsa_signature *htlc_sigs;
	struct added_htlc *added;
	struct fulfilled_htlc *fulfilled;
	struct failed_htlc *failed;
	struct changed_htlc *changed;
	size_t i;

	if (!fromwire_channel_got_commitsig(msg, msg, NULL,
					    &commitnum,
					    &commit_sig,
					    &htlc_sigs,
					    &added,
					    &fulfilled,
					    &failed,
					    &changed)) {
		log_broken(peer->log, "bad fromwire_channel_got_commitsig %s",
			   tal_hex(peer, msg));
		return -1;
	}

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

	/* FIXME: store commit & htlc signature information. */

	/* New HTLCs */
	for (i = 0; i < tal_count(added); i++)
		added_their_htlc(peer, &added[i]);

	/* Save information now for fulfilled & failed HTLCs */
	for (i = 0; i < tal_count(fulfilled); i++) {
		if (!peer_fulfilled_our_htlc(peer, &fulfilled[i]))
			return -1;
	}

	for (i = 0; i < tal_count(failed); i++) {
		if (!peer_failed_our_htlc(peer, &failed[i]))
			return -1;
	}
	
	for (i = 0; i < tal_count(changed); i++) {
		if (!changed_htlc(peer, &changed[i])) {
			log_broken(peer->log,
				   "got_commitsig: update failed");
			return -1;
		}
	}

	/* Since we're about to send revoke, bump state again. */
	if (!peer_sending_revocation(peer, added, fulfilled, failed, changed))
		return -1;

	/* Tell it we've committed, and to go ahead with revoke. */
	msg = towire_channel_got_commitsig_reply(msg);
	subd_send_msg(peer->owner, take(msg));
	return 0;
}

int peer_got_revoke(struct peer *peer, const u8 *msg)
{
	u64 revokenum;
	struct sha256 per_commitment_secret;
	u64 *added_ids;
	struct secret *shared_secret;
	struct changed_htlc *changed;
	enum onion_type *failcodes;
	size_t i;

	if (!fromwire_channel_got_revoke(msg, msg, NULL,
					 &revokenum, &per_commitment_secret,
					 &added_ids, &shared_secret,
					 &changed)) {
		log_broken(peer->log, "bad fromwire_channel_got_revoke %s",
			   tal_hex(peer, msg));
		return -1;
	}

	log_debug(peer->log,
		  "got revoke %"PRIu64": %zu changed, %zu incoming locked in",
		  revokenum,
		  tal_count(changed), tal_count(added_ids));

	/* Save any immediate failures for after we reply. */
	failcodes = tal_arr(msg, enum onion_type, tal_count(added_ids));
	for (i = 0; i < tal_count(added_ids); i++) {
		if (!peer_accepted_htlc(peer, added_ids[i], &shared_secret[i],
					&failcodes[i]))
			return -1;
	}

	for (i = 0; i < tal_count(changed); i++) {
		if (!changed_htlc(peer, &changed[i])) {
			log_broken(peer->log, "got_revoke: update failed");
			return -1;
		}
	}

	/* FIXME: Save per-commit-secret! */

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

	/* Now, any HTLCs we need to immediately fail? */
	for (i = 0; i < tal_count(added_ids); i++) {
		struct sha256 bad_onion_sha;
		struct htlc_end *hend;

		if (!failcodes[i])
			continue;

		hend = find_htlc_end(&peer->ld->htlc_ends, peer, added_ids[i],
				     HTLC_SRC);

		sha256(&bad_onion_sha, hend->next_onion,
		       tal_len(hend->next_onion));
		fail_htlc(hend, failcodes[i], &bad_onion_sha);
	}
	return 0;
}