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core-lightning/lightningd/closing/closing.c
Rusty Russell c389215a35 closingd: send the tx to master as we negotiate. 
We can derive fees from this, and also broadcast at any time without
having to reconstruct it.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
2017-08-20 13:06:41 +09:30

469 lines
14 KiB
C
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#include <bitcoin/script.h>
#include <close_tx.h>
#include <daemon/htlc.h>
#include <errno.h>
#include <inttypes.h>
#include <lightningd/closing/gen_closing_wire.h>
#include <lightningd/crypto_sync.h>
#include <lightningd/debug.h>
#include <lightningd/derive_basepoints.h>
#include <lightningd/status.h>
#include <lightningd/subd.h>
#include <signal.h>
#include <stdio.h>
#include <type_to_string.h>
#include <utils.h>
#include <version.h>
#include <wire/peer_wire.h>
#include <wire/wire_sync.h>
/* stdin == requests, 3 == peer, 4 = gossip */
#define REQ_FD STDIN_FILENO
#define PEER_FD 3
#define GOSSIP_FD 4
static struct bitcoin_tx *close_tx(const tal_t *ctx,
u8 *scriptpubkey[NUM_SIDES],
const struct sha256_double *funding_txid,
unsigned int funding_txout,
u64 funding_satoshi,
const u64 satoshi_out[NUM_SIDES],
enum side funder,
uint64_t fee,
uint64_t dust_limit)
{
struct bitcoin_tx *tx;
if (satoshi_out[funder] < fee)
status_failed(WIRE_CLOSING_NEGOTIATION_ERROR,
"Funder cannot afford fee %"PRIu64
" (%"PRIu64" and %"PRIu64")",
fee, satoshi_out[LOCAL],
satoshi_out[REMOTE]);
status_trace("Making close tx at = %"PRIu64"/%"PRIu64" fee %"PRIu64,
satoshi_out[LOCAL], satoshi_out[REMOTE], fee);
tx = create_close_tx(ctx, scriptpubkey[LOCAL], scriptpubkey[REMOTE],
funding_txid,
funding_txout,
funding_satoshi,
satoshi_out[LOCAL] - (funder == LOCAL ? fee : 0),
satoshi_out[REMOTE] - (funder == REMOTE ? fee : 0),
dust_limit);
if (!tx)
status_failed(WIRE_CLOSING_NEGOTIATION_ERROR,
"Both outputs below dust limit:"
" funding = %"PRIu64
" fee = %"PRIu64
" dust_limit = %"PRIu64
" LOCAL = %"PRIu64
" REMOTE = %"PRIu64,
funding_satoshi,
fee,
dust_limit,
satoshi_out[LOCAL],
satoshi_out[REMOTE]);
return tx;
}
static u64 one_towards(u64 target, u64 value)
{
if (value > target)
return value-1;
else if (value < target)
return value+1;
return value;
}
static void do_reconnect(struct crypto_state *cs,
const struct channel_id *channel_id,
const u64 next_index[NUM_SIDES],
u64 revocations_received)
{
u8 *msg;
struct channel_id their_channel_id;
const tal_t *tmpctx = tal_tmpctx(NULL);
u64 next_local_commitment_number, next_remote_revocation_number;
/* BOLT #2:
*
* On reconnection, a node MUST transmit `channel_reestablish` for
* each channel, and MUST wait for to receive the other node's
* `channel_reestablish` message before sending any other messages for
* that channel. The sending node MUST set
* `next_local_commitment_number` to the commitment number of the next
* `commitment_signed` it expects to receive, and MUST set
* `next_remote_revocation_number` to the commitment number of the
* next `revoke_and_ack` message it expects to receive.
*/
msg = towire_channel_reestablish(tmpctx, channel_id,
next_index[LOCAL],
revocations_received);
if (!sync_crypto_write(cs, PEER_FD, take(msg)))
status_failed(WIRE_CLOSING_PEER_WRITE_FAILED,
"Failed writing reestablish: %s", strerror(errno));
again:
msg = sync_crypto_read(tmpctx, cs, PEER_FD);
if (!msg)
status_failed(WIRE_CLOSING_PEER_READ_FAILED,
"Failed reading reestablish: %s", strerror(errno));
if (is_gossip_msg(msg)) {
if (!wire_sync_write(GOSSIP_FD, take(msg)))
status_failed(WIRE_CLOSING_GOSSIP_FAILED,
"Writing gossip");
goto again;
}
if (!fromwire_channel_reestablish(msg, NULL, &their_channel_id,
&next_local_commitment_number,
&next_remote_revocation_number)) {
status_failed(WIRE_CLOSING_PEER_READ_FAILED,
"bad reestablish msg: %s %s",
wire_type_name(fromwire_peektype(msg)),
tal_hex(tmpctx, msg));
}
status_trace("Got reestablish commit=%"PRIu64" revoke=%"PRIu64,
next_local_commitment_number,
next_remote_revocation_number);
/* FIXME: Spec says to re-xmit funding_locked here if we haven't
* done any updates. */
/* BOLT #2:
*
* On reconnection if the node has sent a previous `closing_signed` it
* MUST then retransmit the last `closing_signed`
*/
/* Since we always transmit closing_signed immediately, if
* we're reconnecting we consider ourselves to have transmitted once,
* and we'll immediately do the retransmit now anyway. */
tal_free(tmpctx);
}
int main(int argc, char *argv[])
{
struct crypto_state cs;
const tal_t *ctx = tal_tmpctx(NULL);
u8 *msg;
struct privkey seed;
struct pubkey funding_pubkey[NUM_SIDES];
struct sha256_double funding_txid;
u16 funding_txout;
u64 funding_satoshi, satoshi_out[NUM_SIDES];
u64 our_dust_limit;
u64 minfee, maxfee, sent_fee;
s64 last_received_fee = -1;
enum side funder;
u8 *scriptpubkey[NUM_SIDES], *funding_wscript;
struct channel_id channel_id;
struct secrets secrets;
secp256k1_ecdsa_signature sig;
bool reconnected;
u64 next_index[NUM_SIDES], revocations_received;
if (argc == 2 && streq(argv[1], "--version")) {
printf("%s\n", version());
exit(0);
}
subdaemon_debug(argc, argv);
/* We handle write returning errors! */
signal(SIGCHLD, SIG_IGN);
secp256k1_ctx = secp256k1_context_create(SECP256K1_CONTEXT_VERIFY
| SECP256K1_CONTEXT_SIGN);
status_setup_sync(REQ_FD);
msg = wire_sync_read(ctx, REQ_FD);
if (!fromwire_closing_init(ctx, msg, NULL,
&cs, &seed,
&funding_txid, &funding_txout,
&funding_satoshi,
&funding_pubkey[REMOTE],
&funder,
&satoshi_out[LOCAL],
&satoshi_out[REMOTE],
&our_dust_limit,
&minfee, &maxfee, &sent_fee,
&scriptpubkey[LOCAL],
&scriptpubkey[REMOTE],
&reconnected,
&next_index[LOCAL],
&next_index[REMOTE],
&revocations_received)) {
status_failed(WIRE_CLOSING_PEER_BAD_MESSAGE,
"Bad init message %s", tal_hex(ctx, msg));
}
status_trace("satoshi_out = %"PRIu64"/%"PRIu64,
satoshi_out[LOCAL], satoshi_out[REMOTE]);
status_trace("dustlimit = %"PRIu64, our_dust_limit);
status_trace("fee = %"PRIu64, sent_fee);
derive_channel_id(&channel_id, &funding_txid, funding_txout);
derive_basepoints(&seed, &funding_pubkey[LOCAL], NULL,
&secrets, NULL);
funding_wscript = bitcoin_redeem_2of2(ctx,
&funding_pubkey[LOCAL],
&funding_pubkey[REMOTE]);
if (reconnected)
do_reconnect(&cs, &channel_id, next_index, revocations_received);
/* BOLT #2:
*
* Nodes SHOULD send a `closing_signed` message after `shutdown` has
* been received and no HTLCs remain in either commitment transaction.
*/
/* BOLT #2:
*
* On reconnection, ... if the node has sent a previous
* `closing_signed` it MUST then retransmit the last `closing_signed`.
*/
for (;;) {
const tal_t *tmpctx = tal_tmpctx(ctx);
struct bitcoin_tx *tx;
u64 received_fee, limit_fee, new_fee;
/* BOLT #2:
*
* The sender MUST set `signature` to the Bitcoin signature of
* the close transaction with the node responsible for paying
* the bitcoin fee paying `fee_satoshis`, then removing any
* output which is below its own `dust_limit_satoshis`. The
* sender MAY then also eliminate its own output from the
* mutual close transaction.
*/
tx = close_tx(tmpctx, scriptpubkey,
&funding_txid,
funding_txout,
funding_satoshi,
satoshi_out, funder, sent_fee, our_dust_limit);
/* BOLT #2:
*
* The sender MAY then also eliminate its own output from the
* mutual close transaction.
*/
/* (We don't do this). */
sign_tx_input(tx, 0, NULL, funding_wscript,
&secrets.funding_privkey,
&funding_pubkey[LOCAL],
&sig);
status_trace("sending fee offer %"PRIu64, sent_fee);
/* Now send closing offer */
msg = towire_closing_signed(tmpctx, &channel_id, sent_fee, &sig);
if (!sync_crypto_write(&cs, PEER_FD, take(msg)))
status_failed(WIRE_CLOSING_PEER_WRITE_FAILED,
"Writing closing_signed");
/* Did we just agree with them? If so, we're done. */
if (sent_fee == last_received_fee)
break;
again:
msg = sync_crypto_read(tmpctx, &cs, PEER_FD);
if (!msg)
status_failed(WIRE_CLOSING_PEER_READ_FAILED,
"Reading input");
/* We don't send gossip at this stage, but we can recv it */
if (is_gossip_msg(msg)) {
if (!wire_sync_write(GOSSIP_FD, take(msg)))
status_failed(WIRE_CLOSING_GOSSIP_FAILED,
"Writing gossip");
goto again;
}
/* BOLT #2:
*
* On reconnection, a node MUST ignore a redundant
* `funding_locked` if it receives one.
*/
/* This should only happen if we've made no commitments, but
* we don't have to check that: it's their problem. */
if (fromwire_peektype(msg) == WIRE_FUNDING_LOCKED) {
tal_free(msg);
goto again;
}
/* BOLT #2:
*
* ...if the node has sent a previous `shutdown` it MUST
* retransmit it.
*/
if (fromwire_peektype(msg) == WIRE_SHUTDOWN) {
tal_free(msg);
goto again;
}
if (!fromwire_closing_signed(msg, NULL, &channel_id,
&received_fee, &sig))
status_failed(WIRE_CLOSING_PEER_BAD_MESSAGE,
"Expected closing_signed: %s",
tal_hex(trc, msg));
/* BOLT #2:
*
* The receiver MUST check `signature` is valid for either the
* close transaction with the given `fee_satoshis` as detailed
* above and its own `dust_limit_satoshis` OR that same
* transaction with the sender's output eliminated, and MUST
* fail the connection if it is not.
*/
tx = close_tx(tmpctx, scriptpubkey,
&funding_txid,
funding_txout,
funding_satoshi,
satoshi_out, funder, received_fee, our_dust_limit);
if (!check_tx_sig(tx, 0, NULL, funding_wscript,
&funding_pubkey[REMOTE], &sig)) {
/* Trim it by reducing their output to minimum */
struct bitcoin_tx *trimmed;
u64 trimming_satoshi_out[NUM_SIDES];
if (funder == REMOTE)
trimming_satoshi_out[REMOTE] = received_fee;
else
trimming_satoshi_out[REMOTE] = 0;
trimming_satoshi_out[LOCAL] = satoshi_out[LOCAL];
trimmed = close_tx(tmpctx, scriptpubkey,
&funding_txid,
funding_txout,
funding_satoshi,
trimming_satoshi_out,
funder, received_fee, our_dust_limit);
if (!trimmed
|| !check_tx_sig(trimmed, 0, NULL, funding_wscript,
&funding_pubkey[REMOTE], &sig)) {
status_failed(WIRE_CLOSING_PEER_BAD_MESSAGE,
"Bad closing_signed signature for"
" %s (and trimmed version %s)",
type_to_string(tmpctx,
struct bitcoin_tx,
tx),
trimmed ?
type_to_string(tmpctx,
struct bitcoin_tx,
trimmed)
: "NONE");
}
tx = trimmed;
}
status_trace("Received fee offer %"PRIu64, received_fee);
/* BOLT #2:
*
* Otherwise, the recipient MUST fail the connection if
* `fee_satoshis` is greater than the base fee of the final
* commitment transaction as calculated in [BOLT #3] */
if (received_fee > maxfee)
status_failed(WIRE_CLOSING_PEER_BAD_MESSAGE,
"Bad closing_signed fee %"PRIu64
" > %"PRIu64,
received_fee, maxfee);
/* Is fee reasonable? Tell master. */
if (received_fee < minfee) {
status_trace("Fee too low, below %"PRIu64, minfee);
limit_fee = minfee;
} else {
status_trace("Fee accepted.");
msg = towire_closing_received_signature(tmpctx,
&sig, tx);
if (!wire_sync_write(REQ_FD, take(msg)))
status_failed(WIRE_CLOSING_INTERNAL_ERROR,
"Writing received to master: %s",
strerror(errno));
msg = wire_sync_read(tmpctx, REQ_FD);
if (!fromwire_closing_received_signature_reply(msg,NULL))
status_failed(WIRE_CLOSING_INTERNAL_ERROR,
"Bad received reply from master");
limit_fee = received_fee;
}
/* BOLT #2:
*
* Once a node has sent or received a `closing_signed` with
* matching `fee_satoshis` it SHOULD close the connection and
* SHOULD sign and broadcast the final closing transaction.
*/
if (received_fee == sent_fee)
break;
/* BOLT #2:
*
* the recipient SHOULD fail the connection if `fee_satoshis`
* is not strictly between its last-sent `fee_satoshis` and
* its previously-received `fee_satoshis`, unless it has
* reconnected since then. */
if (last_received_fee != -1) {
bool previous_dir = sent_fee < last_received_fee;
bool dir = received_fee < last_received_fee;
bool next_dir = sent_fee < received_fee;
/* They went away from our offer? */
if (dir != previous_dir)
status_failed(WIRE_CLOSING_NEGOTIATION_ERROR,
"Their fee went %"
PRIu64" to %"PRIu64
" when ours was %"PRIu64,
last_received_fee,
received_fee,
sent_fee);
/* They jumped over our offer? */
if (next_dir != previous_dir)
status_failed(WIRE_CLOSING_NEGOTIATION_ERROR,
"Their fee jumped %"
PRIu64" to %"PRIu64
" when ours was %"PRIu64,
last_received_fee,
received_fee,
sent_fee);
}
/* BOLT #2:
*
* ...otherwise it SHOULD propose a value strictly between the
* received `fee_satoshis` and its previously-sent
* `fee_satoshis`.
*/
/* We do it by bisection, with twists:
* 1. Don't go outside limits, or reach them immediately:
* treat out-of-limit offers as on-limit offers.
* 2. Round towards the target, otherwise we can't close
* a final 1-satoshi gap.
*
* Note: Overflow impossible here, since fee <= funder amount */
new_fee = one_towards(limit_fee, limit_fee + sent_fee) / 2;
/* If we didn't move, give up (we're ~ at min/max). */
if (new_fee == sent_fee)
status_failed(WIRE_CLOSING_NEGOTIATION_ERROR,
"Final fee %"PRIu64" vs %"PRIu64
" at limits %"PRIu64"-%"PRIu64,
sent_fee, received_fee,
minfee, maxfee);
last_received_fee = received_fee;
sent_fee = new_fee;
tal_free(tmpctx);
}
/* We're done! */
wire_sync_write(REQ_FD, take(towire_closing_complete(ctx)));
tal_free(ctx);
return 0;
}
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