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full_channel.c
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full_channel.c
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#include "config.h"
#include <bitcoin/psbt.h>
#include <bitcoin/script.h>
#include <ccan/array_size/array_size.h>
#include <channeld/commit_tx.h>
#include <channeld/full_channel.h>
#include <common/blockheight_states.h>
#include <common/features.h>
#include <common/fee_states.h>
#include <common/htlc_trim.h>
#include <common/htlc_tx.h>
#include <common/htlc_wire.h>
#include <common/keyset.h>
#include <common/memleak.h>
#include <common/status.h>
#include <common/type_to_string.h>
#include <stdio.h>
/* Needs to be at end, since it doesn't include its own hdrs */
#include "full_channel_error_names_gen.h"
#if DEVELOPER
static void memleak_help_htlcmap(struct htable *memtable,
struct htlc_map *htlcs)
{
memleak_remove_htable(memtable, &htlcs->raw);
}
#endif /* DEVELOPER */
/* This is a dangerous thing! Because we apply HTLCs in many places
* in bulk, we can temporarily go negative. You must check balance_ok()
* at the end! */
struct balance {
s64 msat;
};
static void to_balance(struct balance *balance,
const struct amount_msat msat)
{
balance->msat = msat.millisatoshis; /* Raw: balance */
assert(balance->msat >= 0);
}
/* What does adding the HTLC do to the balance for this side (subtracts) */
static void balance_add_htlc(struct balance *balance,
const struct htlc *htlc,
enum side side)
{
if (htlc_owner(htlc) == side)
balance->msat -= htlc->amount.millisatoshis; /* Raw: balance */
}
/* What does removing the HTLC do to the balance for this side (adds) */
static void balance_remove_htlc(struct balance *balance,
const struct htlc *htlc,
enum side side)
{
enum side paid_to;
/* Fulfilled HTLCs are paid to recipient, otherwise returns to owner */
if (htlc->r)
paid_to = !htlc_owner(htlc);
else
paid_to = htlc_owner(htlc);
if (side == paid_to)
balance->msat += htlc->amount.millisatoshis; /* Raw: balance */
}
static bool balance_ok(const struct balance *balance,
struct amount_msat *msat)
WARN_UNUSED_RESULT;
static bool balance_ok(const struct balance *balance,
struct amount_msat *msat)
{
if (balance->msat < 0)
return false;
*msat = amount_msat(balance->msat);
return true;
}
struct channel *new_full_channel(const tal_t *ctx,
const struct channel_id *cid,
const struct bitcoin_outpoint *funding,
u32 minimum_depth,
const struct height_states *blockheight_states,
u32 lease_expiry,
struct amount_sat funding_sats,
struct amount_msat local_msat,
const struct fee_states *fee_states TAKES,
const struct channel_config *local,
const struct channel_config *remote,
const struct basepoints *local_basepoints,
const struct basepoints *remote_basepoints,
const struct pubkey *local_funding_pubkey,
const struct pubkey *remote_funding_pubkey,
const struct channel_type *type TAKES,
bool option_wumbo,
enum side opener)
{
struct channel *channel = new_initial_channel(ctx,
cid,
funding,
minimum_depth,
blockheight_states,
lease_expiry,
funding_sats,
local_msat,
fee_states,
local, remote,
local_basepoints,
remote_basepoints,
local_funding_pubkey,
remote_funding_pubkey,
type,
option_wumbo,
opener);
if (channel) {
channel->htlcs = tal(channel, struct htlc_map);
htlc_map_init(channel->htlcs);
memleak_add_helper(channel->htlcs, memleak_help_htlcmap);
tal_add_destructor(channel->htlcs, htlc_map_clear);
}
return channel;
}
static void htlc_arr_append(const struct htlc ***arr, const struct htlc *htlc)
{
if (!arr)
return;
tal_arr_expand(arr, htlc);
}
static void dump_htlc(const struct htlc *htlc, const char *prefix)
{
enum htlc_state remote_state;
if (htlc->state <= RCVD_REMOVE_ACK_REVOCATION)
remote_state = htlc->state + 10;
else
remote_state = htlc->state - 10;
status_debug("%s: HTLC %s %"PRIu64" = %s/%s %s",
prefix,
htlc_owner(htlc) == LOCAL ? "LOCAL" : "REMOTE",
htlc->id,
htlc_state_name(htlc->state),
htlc_state_name(remote_state),
htlc->r ? "FULFILLED" : htlc->failed ? "FAILED"
: "");
}
void dump_htlcs(const struct channel *channel, const char *prefix)
{
#ifdef SUPERVERBOSE
struct htlc_map_iter it;
const struct htlc *htlc;
for (htlc = htlc_map_first(channel->htlcs, &it);
htlc;
htlc = htlc_map_next(channel->htlcs, &it)) {
dump_htlc(htlc, prefix);
}
#endif
}
/* Returns up to three arrays:
* committed: HTLCs currently committed.
* pending_removal: HTLCs pending removal (subset of committed)
* pending_addition: HTLCs pending addition (no overlap with committed)
*
* Also returns number of HTLCs for other side.
*/
static size_t gather_htlcs(const tal_t *ctx,
const struct channel *channel,
enum side side,
const struct htlc ***committed,
const struct htlc ***pending_removal,
const struct htlc ***pending_addition)
{
struct htlc_map_iter it;
const struct htlc *htlc;
const int committed_flag = HTLC_FLAG(side, HTLC_F_COMMITTED);
const int pending_flag = HTLC_FLAG(side, HTLC_F_PENDING);
size_t num_other_side = 0;
*committed = tal_arr(ctx, const struct htlc *, 0);
if (pending_removal)
*pending_removal = tal_arr(ctx, const struct htlc *, 0);
if (pending_addition)
*pending_addition = tal_arr(ctx, const struct htlc *, 0);
if (!channel->htlcs)
return num_other_side;
for (htlc = htlc_map_first(channel->htlcs, &it);
htlc;
htlc = htlc_map_next(channel->htlcs, &it)) {
if (htlc_has(htlc, committed_flag)) {
#ifdef SUPERVERBOSE
dump_htlc(htlc, "COMMITTED");
#endif
htlc_arr_append(committed, htlc);
if (htlc_has(htlc, pending_flag)) {
#ifdef SUPERVERBOSE
dump_htlc(htlc, "REMOVING");
#endif
htlc_arr_append(pending_removal, htlc);
} else if (htlc_owner(htlc) != side)
num_other_side++;
} else if (htlc_has(htlc, pending_flag)) {
htlc_arr_append(pending_addition, htlc);
#ifdef SUPERVERBOSE
dump_htlc(htlc, "ADDING");
#endif
if (htlc_owner(htlc) != side)
num_other_side++;
}
}
return num_other_side;
}
static bool sum_offered_msatoshis(struct amount_msat *total,
const struct htlc **htlcs,
enum side side)
{
size_t i;
*total = AMOUNT_MSAT(0);
for (i = 0; i < tal_count(htlcs); i++) {
if (htlc_owner(htlcs[i]) == side) {
if (!amount_msat_add(total, *total, htlcs[i]->amount))
return false;
}
}
return true;
}
static void add_htlcs(struct bitcoin_tx ***txs,
const struct htlc **htlcmap,
const struct channel *channel,
const struct keyset *keyset,
enum side side)
{
struct bitcoin_outpoint outpoint;
u32 feerate_per_kw = channel_feerate(channel, side);
bool option_anchor_outputs = channel_has(channel, OPT_ANCHOR_OUTPUTS);
/* Get txid of commitment transaction */
bitcoin_txid((*txs)[0], &outpoint.txid);
for (outpoint.n = 0; outpoint.n < tal_count(htlcmap); outpoint.n++) {
const struct htlc *htlc = htlcmap[outpoint.n];
struct bitcoin_tx *tx;
struct ripemd160 ripemd;
const u8 *wscript;
if (!htlc)
continue;
if (htlc_owner(htlc) == side) {
ripemd160(&ripemd, htlc->rhash.u.u8, sizeof(htlc->rhash.u.u8));
wscript = htlc_offered_wscript(tmpctx, &ripemd, keyset,
option_anchor_outputs);
tx = htlc_timeout_tx(*txs, chainparams, &outpoint,
wscript,
htlc->amount,
htlc->expiry.locktime,
channel->config[!side].to_self_delay,
feerate_per_kw,
keyset,
option_anchor_outputs);
} else {
ripemd160(&ripemd, htlc->rhash.u.u8, sizeof(htlc->rhash.u.u8));
wscript = htlc_received_wscript(tmpctx, &ripemd,
&htlc->expiry, keyset,
option_anchor_outputs);
tx = htlc_success_tx(*txs, chainparams, &outpoint,
wscript,
htlc->amount,
channel->config[!side].to_self_delay,
feerate_per_kw,
keyset,
option_anchor_outputs);
}
/* Append to array. */
tal_arr_expand(txs, tx);
}
}
/* FIXME: We could cache these. */
struct bitcoin_tx **channel_txs(const tal_t *ctx,
const struct htlc ***htlcmap,
struct wally_tx_output *direct_outputs[NUM_SIDES],
const u8 **funding_wscript,
const struct channel *channel,
const struct pubkey *per_commitment_point,
u64 commitment_number,
enum side side)
{
struct bitcoin_tx **txs;
const struct htlc **committed;
struct keyset keyset;
if (!derive_keyset(per_commitment_point,
&channel->basepoints[side],
&channel->basepoints[!side],
channel_has(channel, OPT_STATIC_REMOTEKEY),
&keyset))
return NULL;
/* Figure out what @side will already be committed to. */
gather_htlcs(ctx, channel, side, &committed, NULL, NULL);
/* Generating and saving witness script required to spend
* the funding output */
*funding_wscript = bitcoin_redeem_2of2(ctx,
&channel->funding_pubkey[side],
&channel->funding_pubkey[!side]);
txs = tal_arr(ctx, struct bitcoin_tx *, 1);
txs[0] = commit_tx(
ctx, &channel->funding,
channel->funding_sats,
&channel->funding_pubkey[side],
&channel->funding_pubkey[!side],
channel->opener,
channel->config[!side].to_self_delay,
channel->lease_expiry,
channel_blockheight(channel, side),
&keyset, channel_feerate(channel, side),
channel->config[side].dust_limit, channel->view[side].owed[side],
channel->view[side].owed[!side], committed, htlcmap, direct_outputs,
commitment_number ^ channel->commitment_number_obscurer,
channel_has(channel, OPT_ANCHOR_OUTPUTS),
side);
/* Set the remote/local pubkeys on the commitment tx psbt */
psbt_input_add_pubkey(txs[0]->psbt, 0,
&channel->funding_pubkey[side]);
psbt_input_add_pubkey(txs[0]->psbt, 0,
&channel->funding_pubkey[!side]);
add_htlcs(&txs, *htlcmap, channel, &keyset, side);
tal_free(committed);
return txs;
}
/* If @side is faced with these HTLCs, how much will it have left
* above reserve (eg. to pay fees). Returns false if would be < 0. */
static bool get_room_above_reserve(const struct channel *channel,
const struct channel_view *view,
const struct htlc **adding,
const struct htlc **removing,
enum side side,
struct amount_msat *remainder)
{
/* Reserve is set by the *other* side */
struct amount_sat reserve = channel->config[!side].channel_reserve;
struct balance balance;
to_balance(&balance, view->owed[side]);
for (size_t i = 0; i < tal_count(removing); i++)
balance_remove_htlc(&balance, removing[i], side);
for (size_t i = 0; i < tal_count(adding); i++)
balance_add_htlc(&balance, adding[i], side);
/* Can happen if amount completely exceeds capacity */
if (!balance_ok(&balance, remainder)) {
status_debug("Failed to add %zu remove %zu htlcs",
tal_count(adding), tal_count(removing));
return false;
}
if (!amount_msat_sub_sat(remainder, *remainder, reserve)) {
status_debug("%s cannot afford htlc: would make balance %s"
" below reserve %s",
side_to_str(side),
type_to_string(tmpctx, struct amount_msat,
remainder),
type_to_string(tmpctx, struct amount_sat,
&reserve));
return false;
}
return true;
}
static size_t num_untrimmed_htlcs(enum side side,
struct amount_sat dust_limit,
u32 feerate,
bool option_static_remotekey,
const struct htlc **committed,
const struct htlc **adding,
const struct htlc **removing)
{
return commit_tx_num_untrimmed(committed, feerate, dust_limit,
option_static_remotekey, side)
+ commit_tx_num_untrimmed(adding, feerate, dust_limit,
option_static_remotekey, side)
- commit_tx_num_untrimmed(removing, feerate, dust_limit,
option_static_remotekey, side);
}
static struct amount_sat fee_for_htlcs(const struct channel *channel,
const struct htlc **committed,
const struct htlc **adding,
const struct htlc **removing,
enum side side)
{
u32 feerate = channel_feerate(channel, side);
struct amount_sat dust_limit = channel->config[side].dust_limit;
size_t untrimmed;
bool option_anchor_outputs = channel_has(channel, OPT_ANCHOR_OUTPUTS);
untrimmed = num_untrimmed_htlcs(side, dust_limit, feerate,
option_anchor_outputs,
committed, adding, removing);
return commit_tx_base_fee(feerate, untrimmed, option_anchor_outputs);
}
static bool htlc_dust(const struct channel *channel,
const struct htlc **committed,
const struct htlc **adding,
const struct htlc **removing,
enum side side,
u32 feerate,
struct amount_msat *trim_total)
{
struct amount_sat dust_limit = channel->config[side].dust_limit;
bool option_anchor_outputs = channel_has(channel, OPT_ANCHOR_OUTPUTS);
struct amount_msat trim_rmvd = AMOUNT_MSAT(0);
if (!commit_tx_amount_trimmed(committed, feerate,
dust_limit,
option_anchor_outputs,
side, trim_total))
return false;
if (!commit_tx_amount_trimmed(adding, feerate,
dust_limit,
option_anchor_outputs,
side, trim_total))
return false;
if (!commit_tx_amount_trimmed(removing, feerate,
dust_limit,
option_anchor_outputs,
side, &trim_rmvd))
return false;
return amount_msat_sub(trim_total, *trim_total, trim_rmvd);
}
/*
* There is a corner case where the opener can spend so much that the
* non-opener can't add any non-dust HTLCs (since the opener would
* have to pay the additional fee, but it can't afford to). This
* leads to the channel starving at the feast! This was reported by
* ACINQ's @t-bast
* (https://github.com/lightningnetwork/lightning-rfc/issues/728) and
* demonstrated with c-lightning by @m-schmoock
* (https://github.com/ElementsProject/lightning/pull/3498).
*
* To mostly avoid this situation, at least from our side, we apply an
* additional constraint when we're opener trying to add an HTLC: make
* sure we can afford one more HTLC, even if fees increase by 100%.
*
* We could do this for the peer, as well, by rejecting their HTLC
* immediately in this case. But rejecting a remote HTLC here causes
* us to get upset with them and close the channel: we're not well
* architected to reject HTLCs in channeld (it's usually lightningd's
* job, but it doesn't have all the channel balance change calculation
* logic. So we look after ourselves for now, and hope other nodes start
* self-regulating too.
*
* This mitigation will become BOLT #2 standard by:
* https://github.com/lightningnetwork/lightning-rfc/issues/740
*/
static bool local_opener_has_fee_headroom(const struct channel *channel,
struct amount_msat remainder,
const struct htlc **committed,
const struct htlc **adding,
const struct htlc **removing)
{
u32 feerate = channel_feerate(channel, LOCAL);
size_t untrimmed;
struct amount_sat fee;
bool option_anchor_outputs = channel_has(channel, OPT_ANCHOR_OUTPUTS);
assert(channel->opener == LOCAL);
/* How many untrimmed at current feerate? Increasing feerate can
* only *reduce* this number, so use current feerate here! */
untrimmed = num_untrimmed_htlcs(LOCAL, channel->config[LOCAL].dust_limit,
feerate,
option_anchor_outputs,
committed, adding, removing);
/* Now, how much would it cost us if feerate increases 100% and we added
* another HTLC? */
fee = commit_tx_base_fee(2 * feerate, untrimmed + 1,
option_anchor_outputs);
if (amount_msat_greater_eq_sat(remainder, fee))
return true;
status_debug("Adding HTLC would leave us only %s: we need %s for"
" another HTLC if fees increase by 100%% to %uperkw",
type_to_string(tmpctx, struct amount_msat, &remainder),
type_to_string(tmpctx, struct amount_sat, &fee),
feerate + feerate);
return false;
}
static enum channel_add_err add_htlc(struct channel *channel,
enum htlc_state state,
u64 id,
struct amount_msat amount,
u32 cltv_expiry,
const struct sha256 *payment_hash,
const u8 routing[TOTAL_PACKET_SIZE(ROUTING_INFO_SIZE)],
const struct pubkey *blinding TAKES,
struct htlc **htlcp,
bool enforce_aggregate_limits,
struct amount_sat *htlc_fee,
bool err_immediate_failures)
{
struct htlc *htlc, *old;
struct amount_msat msat_in_htlcs, committed_msat,
adding_msat, removing_msat, htlc_dust_amt;
enum side sender = htlc_state_owner(state), recipient = !sender;
const struct htlc **committed, **adding, **removing;
const struct channel_view *view;
size_t htlc_count;
bool option_anchor_outputs = channel_has(channel, OPT_ANCHOR_OUTPUTS);
u32 feerate, feerate_ceil;
htlc = tal(tmpctx, struct htlc);
htlc->id = id;
htlc->amount = amount;
htlc->state = state;
htlc->fail_immediate = false;
htlc->rhash = *payment_hash;
htlc->blinding = tal_dup_or_null(htlc, struct pubkey, blinding);
htlc->failed = NULL;
htlc->r = NULL;
htlc->routing = tal_dup_arr(htlc, u8, routing, TOTAL_PACKET_SIZE(ROUTING_INFO_SIZE), 0);
/* FIXME: Change expiry to simple u32 */
/* BOLT #2:
*
* A receiving node:
*...
* - if sending node sets `cltv_expiry` to greater or equal to
* 500000000:
* - SHOULD fail the channel.
*/
if (!blocks_to_abs_locktime(cltv_expiry, &htlc->expiry)) {
return CHANNEL_ERR_INVALID_EXPIRY;
}
old = htlc_get(channel->htlcs, htlc->id, htlc_owner(htlc));
if (old) {
if (old->state != htlc->state
|| !amount_msat_eq(old->amount, htlc->amount)
|| old->expiry.locktime != htlc->expiry.locktime
|| !sha256_eq(&old->rhash, &htlc->rhash))
return CHANNEL_ERR_DUPLICATE_ID_DIFFERENT;
else
return CHANNEL_ERR_DUPLICATE;
}
/* We're always considering the recipient's view of the channel here */
view = &channel->view[recipient];
/* BOLT #2:
*
* A receiving node:
* - receiving an `amount_msat` equal to 0, OR less than its own
* `htlc_minimum_msat`:
* - SHOULD fail the channel.
*/
if (amount_msat_eq(htlc->amount, AMOUNT_MSAT(0))) {
return CHANNEL_ERR_HTLC_BELOW_MINIMUM;
}
if (amount_msat_less(htlc->amount, channel->config[recipient].htlc_minimum)) {
return CHANNEL_ERR_HTLC_BELOW_MINIMUM;
}
/* FIXME: There used to be a requirement that we not send more than
* 2^32 msat, *but* only electrum enforced it. Remove in next version:
*
* A sending node:
*...
* - for channels with `chain_hash` identifying the Bitcoin blockchain:
* - MUST set the four most significant bytes of `amount_msat` to 0.
*/
if (sender == LOCAL
&& amount_msat_greater(htlc->amount, chainparams->max_payment)
&& !channel->option_wumbo) {
return CHANNEL_ERR_MAX_HTLC_VALUE_EXCEEDED;
}
/* Figure out what receiver will already be committed to. */
htlc_count = gather_htlcs(tmpctx, channel, recipient, &committed, &removing, &adding);
htlc_arr_append(&adding, htlc);
/* BOLT #2:
*
* - if a sending node adds more than receiver `max_accepted_htlcs`
* HTLCs to its local commitment transaction...
* - SHOULD fail the channel.
*/
if (htlc_count + 1 > channel->config[recipient].max_accepted_htlcs) {
return CHANNEL_ERR_TOO_MANY_HTLCS;
}
/* Also *we* should not add more htlc's we configured. This
* mitigates attacks in which a peer can force the opener of
* the channel to pay unnecessary onchain fees during a fee
* spike with large commitment transactions.
*/
if (sender == LOCAL
&& htlc_count + 1 > channel->config[LOCAL].max_accepted_htlcs) {
return CHANNEL_ERR_TOO_MANY_HTLCS;
}
/* These cannot overflow with HTLC amount limitations, but
* maybe adding could later if they try to add a maximal HTLC. */
if (!sum_offered_msatoshis(&committed_msat,
committed, htlc_owner(htlc))
|| !sum_offered_msatoshis(&removing_msat,
removing, htlc_owner(htlc))
|| !sum_offered_msatoshis(&adding_msat,
adding, htlc_owner(htlc))) {
return CHANNEL_ERR_MAX_HTLC_VALUE_EXCEEDED;
}
if (!amount_msat_add(&msat_in_htlcs, committed_msat, adding_msat)
|| !amount_msat_sub(&msat_in_htlcs, msat_in_htlcs, removing_msat)) {
return CHANNEL_ERR_MAX_HTLC_VALUE_EXCEEDED;
}
/* BOLT #2:
*
* - if a sending node... adds more than receiver
* `max_htlc_value_in_flight_msat` worth of offered HTLCs to its
* local commitment transaction:
* - SHOULD fail the channel.
*/
/* We don't enforce this for channel_force_htlcs: some might already
* be fulfilled/failed */
if (enforce_aggregate_limits
&& amount_msat_greater(msat_in_htlcs,
channel->config[recipient].max_htlc_value_in_flight)) {
return CHANNEL_ERR_MAX_HTLC_VALUE_EXCEEDED;
}
/* BOLT #2:
*
* A receiving node:
*...
* - receiving an `amount_msat` that the sending node cannot afford at
* the current `feerate_per_kw` (while maintaining its channel
* reserve and any `to_local_anchor` and `to_remote_anchor` costs):
* - SHOULD fail the channel.
*/
if (enforce_aggregate_limits) {
struct amount_msat remainder;
struct amount_sat fee = fee_for_htlcs(channel,
committed,
adding,
removing,
recipient);
/* set fee output pointer if given */
if (htlc_fee)
*htlc_fee = fee;
/* This is a little subtle:
*
* The change is being applied to the receiver but it will
* come back to the sender after revoke_and_ack. So the check
* here is that the remainder to the sender doesn't go below the
* sender's reserve. */
if (!get_room_above_reserve(channel, view,
adding, removing, sender,
&remainder))
return CHANNEL_ERR_CHANNEL_CAPACITY_EXCEEDED;
/* BOLT #3:
* If `option_anchors` applies to the commitment
* transaction, also subtract two times the fixed anchor size
* of 330 sats from the funder (either `to_local` or
* `to_remote`).
*/
if (option_anchor_outputs
&& channel->opener == sender
&& !amount_msat_sub_sat(&remainder, remainder, AMOUNT_SAT(660)))
return CHANNEL_ERR_CHANNEL_CAPACITY_EXCEEDED;
if (channel->opener== sender) {
if (amount_msat_less_sat(remainder, fee)) {
status_debug("Cannot afford fee %s with %s above reserve",
type_to_string(tmpctx, struct amount_sat,
&fee),
type_to_string(tmpctx, struct amount_msat,
&remainder));
return CHANNEL_ERR_CHANNEL_CAPACITY_EXCEEDED;
}
if (sender == LOCAL
&& !local_opener_has_fee_headroom(channel,
remainder,
committed,
adding,
removing)) {
return CHANNEL_ERR_CHANNEL_CAPACITY_EXCEEDED;
}
}
/* Try not to add a payment which will take opener into fees
* on either our side or theirs. */
if (sender == LOCAL) {
if (!get_room_above_reserve(channel, view,
adding, removing,
channel->opener,
&remainder))
return CHANNEL_ERR_CHANNEL_CAPACITY_EXCEEDED;
if (option_anchor_outputs
&& channel->opener != sender
&& !amount_msat_sub_sat(&remainder, remainder, AMOUNT_SAT(660)))
return CHANNEL_ERR_CHANNEL_CAPACITY_EXCEEDED;
/* Should be able to afford both their own commit tx
* fee, and other's commit tx fee, which are subtly
* different! */
fee = fee_for_htlcs(channel,
committed,
adding,
removing,
channel->opener);
/* set fee output pointer if given */
if (htlc_fee && amount_sat_greater(fee, *htlc_fee))
*htlc_fee = fee;
if (amount_msat_less_sat(remainder, fee)) {
status_debug("Funder could not afford own fee %s with %s above reserve",
type_to_string(tmpctx,
struct amount_sat,
&fee),
type_to_string(tmpctx,
struct amount_msat,
&remainder));
return CHANNEL_ERR_CHANNEL_CAPACITY_EXCEEDED;
}
fee = fee_for_htlcs(channel,
committed,
adding,
removing,
!channel->opener);
/* set fee output pointer if given */
if (htlc_fee && amount_sat_greater(fee, *htlc_fee))
*htlc_fee = fee;
if (amount_msat_less_sat(remainder, fee)) {
status_debug("Funder could not afford peer's fee %s with %s above reserve",
type_to_string(tmpctx,
struct amount_sat,
&fee),
type_to_string(tmpctx,
struct amount_msat,
&remainder));
return CHANNEL_ERR_CHANNEL_CAPACITY_EXCEEDED;
}
}
}
htlc_dust_amt = AMOUNT_MSAT(0);
feerate = channel_feerate(channel, recipient);
/* Note that we check for trimmed htlcs at an
* *accelerated* rate, so that future feerate changes
* don't suddenly surprise us */
feerate_ceil = htlc_trim_feerate_ceiling(feerate);
if (!htlc_dust(channel, committed,
adding, removing, recipient,
feerate_ceil, &htlc_dust_amt))
return CHANNEL_ERR_CHANNEL_CAPACITY_EXCEEDED;
if (amount_msat_greater(htlc_dust_amt,
channel->config[LOCAL].max_dust_htlc_exposure_msat)) {
/* BOLT-919 #2:
* A node:
* - upon an incoming HTLC:
* - if a HTLC's `amount_msat` is inferior to the
* counterparty's `dust_limit_satoshis` plus the HTLC-timeout fee
* at the `dust_buffer_feerate`: ...
* - SHOULD fail this HTLC once it's committed
* - SHOULD NOT reveal a preimage for this HTLC
*/
/* Note: Marking this as 'fail_immediate' and
* NOT returning an ERR will fail this HTLC
* once it's committed */
htlc->fail_immediate = true;
if (err_immediate_failures)
return CHANNEL_ERR_DUST_FAILURE;
}
/* Also check the sender, as they'll eventually have the same
* constraint */
htlc_dust_amt = AMOUNT_MSAT(0);
feerate = channel_feerate(channel, sender);
feerate_ceil = htlc_trim_feerate_ceiling(feerate);
if (!htlc_dust(channel, committed, adding,
removing, sender, feerate_ceil,
&htlc_dust_amt))
return CHANNEL_ERR_CHANNEL_CAPACITY_EXCEEDED;
if (amount_msat_greater(htlc_dust_amt,
channel->config[LOCAL].max_dust_htlc_exposure_msat)) {
htlc->fail_immediate = true;
if (err_immediate_failures)
return CHANNEL_ERR_DUST_FAILURE;
}
dump_htlc(htlc, "NEW:");
htlc_map_add(channel->htlcs, tal_steal(channel, htlc));
if (htlcp)
*htlcp = htlc;
return CHANNEL_ERR_ADD_OK;
}
enum channel_add_err channel_add_htlc(struct channel *channel,
enum side sender,
u64 id,
struct amount_msat amount,
u32 cltv_expiry,
const struct sha256 *payment_hash,
const u8 routing[TOTAL_PACKET_SIZE(ROUTING_INFO_SIZE)],
const struct pubkey *blinding TAKES,
struct htlc **htlcp,
struct amount_sat *htlc_fee,
bool err_immediate_failures)
{
enum htlc_state state;
if (sender == LOCAL)
state = SENT_ADD_HTLC;
else
state = RCVD_ADD_HTLC;
/* BOLT #2:
* - MUST increase the value of `id` by 1 for each successive offer.
*/
/* This is a weak (bit cheap) check: */
if (htlc_get(channel->htlcs, id+1, sender))
status_broken("Peer sent out-of-order HTLC ids (is that you, old c-lightning node?)");
return add_htlc(channel, state, id, amount, cltv_expiry,
payment_hash, routing, blinding,
htlcp, true, htlc_fee, err_immediate_failures);
}
struct htlc *channel_get_htlc(struct channel *channel, enum side sender, u64 id)
{
return htlc_get(channel->htlcs, id, sender);
}
enum channel_remove_err channel_fulfill_htlc(struct channel *channel,
enum side owner,
u64 id,
const struct preimage *preimage,
struct htlc **htlcp)
{
struct sha256 hash;
struct htlc *htlc;
htlc = channel_get_htlc(channel, owner, id);
if (!htlc)
return CHANNEL_ERR_NO_SUCH_ID;
if (htlc->r)
return CHANNEL_ERR_ALREADY_FULFILLED;
sha256(&hash, preimage, sizeof(*preimage));
/* BOLT #2:
*
* - if the `payment_preimage` value in `update_fulfill_htlc`
* doesn't SHA256 hash to the corresponding HTLC `payment_hash`:
* - MUST fail the channel.
*/
if (!sha256_eq(&hash, &htlc->rhash))
return CHANNEL_ERR_BAD_PREIMAGE;
htlc->r = tal_dup(htlc, struct preimage, preimage);
/* BOLT #2:
*
* - if the `id` does not correspond to an HTLC in its current
* commitment transaction:
* - MUST fail the channel.
*/
if (!htlc_has(htlc, HTLC_FLAG(!htlc_owner(htlc), HTLC_F_COMMITTED))) {
status_unusual("channel_fulfill_htlc: %"PRIu64" in state %s",
htlc->id, htlc_state_name(htlc->state));
return CHANNEL_ERR_HTLC_UNCOMMITTED;
}
/* We enforce a stricter check, forcing state machine to be linear,
* based on: */
/* BOLT #2:
*
* A node:
*...
* - until the corresponding HTLC is irrevocably committed in both
* sides' commitment transactions:
* - MUST NOT send an `update_fulfill_htlc`, `update_fail_htlc`, or
* `update_fail_malformed_htlc`.
*/
if (htlc->state == SENT_ADD_ACK_REVOCATION)
htlc->state = RCVD_REMOVE_HTLC;
else if (htlc->state == RCVD_ADD_ACK_REVOCATION)
htlc->state = SENT_REMOVE_HTLC;
else {
status_unusual("channel_fulfill_htlc: %"PRIu64" in state %s",
htlc->id, htlc_state_name(htlc->state));
return CHANNEL_ERR_HTLC_NOT_IRREVOCABLE;
}
dump_htlc(htlc, "FULFILL:");
if (htlcp)
*htlcp = htlc;
return CHANNEL_ERR_REMOVE_OK;
}
enum channel_remove_err channel_fail_htlc(struct channel *channel,
enum side owner, u64 id,
struct htlc **htlcp)
{
struct htlc *htlc;
htlc = channel_get_htlc(channel, owner, id);
if (!htlc)
return CHANNEL_ERR_NO_SUCH_ID;
/* BOLT #2:
*
* A receiving node:
* - if the `id` does not correspond to an HTLC in its current
* commitment transaction:
* - MUST fail the channel.
*/
if (!htlc_has(htlc, HTLC_FLAG(!htlc_owner(htlc), HTLC_F_COMMITTED))) {
status_unusual("channel_fail_htlc: %"PRIu64" in state %s",
htlc->id, htlc_state_name(htlc->state));
return CHANNEL_ERR_HTLC_UNCOMMITTED;
}
/* FIXME: Technically, they can fail this before we're committed to
* it. This implies a non-linear state machine. */
if (htlc->state == SENT_ADD_ACK_REVOCATION)
htlc->state = RCVD_REMOVE_HTLC;
else if (htlc->state == RCVD_ADD_ACK_REVOCATION)
htlc->state = SENT_REMOVE_HTLC;
else {
status_unusual("channel_fail_htlc: %"PRIu64" in state %s",
htlc->id, htlc_state_name(htlc->state));
return CHANNEL_ERR_HTLC_NOT_IRREVOCABLE;
}
dump_htlc(htlc, "FAIL:");
if (htlcp)
*htlcp = htlc;
return CHANNEL_ERR_REMOVE_OK;
}
static void htlc_incstate(struct channel *channel,
struct htlc *htlc,
enum side sidechanged,
struct balance owed[NUM_SIDES])
{
int preflags, postflags;
const int committed_f = HTLC_FLAG(sidechanged, HTLC_F_COMMITTED);
status_debug("htlc %"PRIu64": %s->%s", htlc->id,
htlc_state_name(htlc->state),
htlc_state_name(htlc->state+1));
preflags = htlc_state_flags(htlc->state);
postflags = htlc_state_flags(htlc->state + 1);
/* You can't change sides. */