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closingd: rewrite negotiation. 

This follows the proposal to make the funder send the first offer.
The dual loops are because there's initially very little restriction
on the amounts, then once they're first established they tighten as
necessary.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
ppa-0.6.1
Rusty Russell 7 years ago
committed by Christian Decker
parent
5deebb85c3
commit
03e961897a
1 changed files with 336 additions and 252 deletions
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  1. 588
      closingd/closing.c

588
closingd/closing.c
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@ -74,15 +74,6 @@ static struct bitcoin_tx *close_tx(const tal_t *ctx,
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;
}
/* Handle random messages we might get, returning the first non-handled one. */
static u8 *closing_read_peer_msg(const tal_t *ctx,
struct crypto_state *cs,
@ -157,6 +148,281 @@ static void do_reconnect(struct crypto_state *cs,
tal_free(tmpctx);
}
static void send_offer(struct crypto_state *cs,
const struct channel_id *channel_id,
const struct pubkey funding_pubkey[NUM_SIDES],
const u8 *funding_wscript,
u8 *scriptpubkey[NUM_SIDES],
const struct bitcoin_txid *funding_txid,
unsigned int funding_txout,
u64 funding_satoshi,
const u64 satoshi_out[NUM_SIDES],
enum side funder,
uint64_t our_dust_limit,
const struct secrets *secrets,
uint64_t fee_to_offer)
{
const tal_t *tmpctx = tal_tmpctx(NULL);
struct bitcoin_tx *tx;
secp256k1_ecdsa_signature our_sig;
u8 *msg;
/* BOLT #2:
*
* The sender MUST set `signature` to the Bitcoin signature of
* the close transaction as specified in [BOLT
* #3](03-transactions.md#closing-transaction).
*/
tx = close_tx(tmpctx, cs, channel_id,
scriptpubkey,
funding_txid,
funding_txout,
funding_satoshi,
satoshi_out,
funder, fee_to_offer, our_dust_limit);
/* BOLT #3:
*
* ## Closing Transaction
*...
* Each node offering a signature... MAY also eliminate its
* own output.
*/
/* (We don't do this). */
sign_tx_input(tx, 0, NULL, funding_wscript,
&secrets->funding_privkey,
&funding_pubkey[LOCAL],
&our_sig);
status_trace("sending fee offer %"PRIu64, fee_to_offer);
msg = towire_closing_signed(tmpctx, channel_id, fee_to_offer, &our_sig);
if (!sync_crypto_write(cs, PEER_FD, take(msg)))
status_failed(STATUS_FAIL_PEER_IO,
"Writing closing_signed");
tal_free(tmpctx);
}
static void tell_master_their_offer(u64 their_offer,
const secp256k1_ecdsa_signature *their_sig,
const struct bitcoin_tx *tx)
{
u8 *msg = towire_closing_received_signature(NULL, their_sig, tx);
if (!wire_sync_write(REQ_FD, take(msg)))
status_failed(STATUS_FAIL_MASTER_IO,
"Writing received to master: %s",
strerror(errno));
/* Wait for master to ack, to make sure it's in db. */
msg = wire_sync_read(NULL, REQ_FD);
if (!fromwire_closing_received_signature_reply(msg,NULL))
master_badmsg(WIRE_CLOSING_RECEIVED_SIGNATURE_REPLY, msg);
tal_free(msg);
}
/* Returns fee they offered. */
static uint64_t receive_offer(struct crypto_state *cs,
const struct channel_id *channel_id,
const struct pubkey funding_pubkey[NUM_SIDES],
const u8 *funding_wscript,
u8 *scriptpubkey[NUM_SIDES],
const struct bitcoin_txid *funding_txid,
unsigned int funding_txout,
u64 funding_satoshi,
const u64 satoshi_out[NUM_SIDES],
enum side funder,
uint64_t our_dust_limit,
u64 min_fee_to_accept)
{
const tal_t *tmpctx = tal_tmpctx(NULL);
u8 *msg;
struct channel_id their_channel_id;
u64 received_fee;
secp256k1_ecdsa_signature their_sig;
struct bitcoin_tx *tx;
/* Wait for them to say something interesting */
do {
msg = closing_read_peer_msg(tmpctx, cs, channel_id);
/* 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)
msg = tal_free(msg);
/* BOLT #2:
*
* ...if the node has sent a previous `shutdown` it MUST
* retransmit it.
*/
else if (fromwire_peektype(msg) == WIRE_SHUTDOWN)
msg = tal_free(msg);
} while (!msg);
if (!fromwire_closing_signed(msg, NULL, &their_channel_id,
&received_fee, &their_sig))
peer_failed(PEER_FD, cs, channel_id,
"Expected closing_signed: %s",
tal_hex(trc, msg));
/* BOLT #2:
*
* The receiver MUST check `signature` is valid for either
* variant of close transaction specified in [BOLT
* #3](03-transactions.md#closing-transaction), and MUST fail
* the connection if it is not.
*/
tx = close_tx(tmpctx, cs, channel_id,
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], &their_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];
/* BOLT #3:
*
* Each node offering a signature MUST subtract the fee given
* by `fee_satoshis` from the output to the funder; it MUST
* then remove any output below its own `dust_limit_satoshis`,
* and MAY also eliminate its own output.
*/
trimmed = close_tx(tmpctx, cs, channel_id,
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], &their_sig)) {
peer_failed(PEER_FD, cs, channel_id,
"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);
/* Master sorts out what is best offer, we just tell it any above min */
if (received_fee >= min_fee_to_accept) {
status_trace("...offer is reasonable");
tell_master_their_offer(received_fee, &their_sig, tx);
}
tal_free(tmpctx);
return received_fee;
}
struct feerange {
enum side higher_side;
u64 min, max;
};
static void init_feerange(struct feerange *feerange,
u64 commitment_fee,
const u64 offer[NUM_SIDES])
{
feerange->min = 0;
/* BOLT #2:
*
* - MUST set `fee_satoshis` less than or equal to the base
* fee of the final commitment transaction, as calculated
* in [BOLT #3](03-transactions.md#fee-calculation).
*/
feerange->max = commitment_fee;
if (offer[LOCAL] > offer[REMOTE])
feerange->higher_side = LOCAL;
else
feerange->higher_side = REMOTE;
status_trace("Feerange init %"PRIu64"-%"PRIu64", %s higher",
feerange->min, feerange->max,
feerange->higher_side == LOCAL ? "local" : "remote");
}
static void adjust_feerange(struct crypto_state *cs,
const struct channel_id *channel_id,
struct feerange *feerange,
u64 offer, enum side side)
{
if (offer < feerange->min || offer > feerange->max)
peer_failed(PEER_FD, cs, channel_id,
"%s offer %"PRIu64
" not between %"PRIu64" and %"PRIu64,
side == LOCAL ? "local" : "remote",
offer, feerange->min, feerange->max);
/* BOLT #2:
*
* ...otherwise it MUST propose a value strictly between the received
* `fee_satoshis` and its previously-sent `fee_satoshis`.
*/
if (side == feerange->higher_side)
feerange->max = offer - 1;
else
feerange->min = offer + 1;
status_trace("Feerange %s update %"PRIu64": now %"PRIu64"-%"PRIu64,
side == LOCAL ? "local" : "remote",
offer, feerange->min, feerange->max);
}
/* Figure out what we should offer now. */
static u64 adjust_offer(struct crypto_state *cs,
const struct channel_id *channel_id,
const struct feerange *feerange,
u64 remote_offer,
u64 min_fee_to_accept)
{
/* Within 1 satoshi? Agree. */
if (feerange->min + 1 >= feerange->max)
return remote_offer;
/* Max is below our minimum acceptable? */
if (feerange->max < min_fee_to_accept)
peer_failed(PEER_FD, cs, channel_id,
"Feerange %"PRIu64"-%"PRIu64
" below minimum acceptable %"PRIu64,
feerange->min, feerange->max,
min_fee_to_accept);
/* Bisect between our minimum and max. */
if (feerange->min > min_fee_to_accept)
min_fee_to_accept = feerange->min;
return (feerange->max + min_fee_to_accept)/2;
}
int main(int argc, char *argv[])
{
struct crypto_state cs;
@ -168,16 +434,16 @@ int main(int argc, char *argv[])
u16 funding_txout;
u64 funding_satoshi, satoshi_out[NUM_SIDES];
u64 our_dust_limit;
u64 minfee, feelimit, maxfee, sent_fee;
s64 last_received_fee = -1;
u64 min_fee_to_accept, commitment_fee, offer[NUM_SIDES];
struct feerange feerange;
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;
u64 gossip_index;
enum side whose_turn;
subdaemon_setup(argc, argv);
@ -193,7 +459,8 @@ int main(int argc, char *argv[])
&satoshi_out[LOCAL],
&satoshi_out[REMOTE],
&our_dust_limit,
&minfee, &maxfee, &sent_fee,
&min_fee_to_accept, &commitment_fee,
&offer[LOCAL],
&scriptpubkey[LOCAL],
&scriptpubkey[REMOTE],
&reconnected,
@ -205,7 +472,7 @@ int main(int argc, char *argv[])
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);
status_trace("fee = %"PRIu64, offer[LOCAL]);
derive_channel_id(&channel_id, &funding_txid, funding_txout);
derive_basepoints(&seed, &funding_pubkey[LOCAL], NULL,
&secrets, NULL);
@ -219,249 +486,66 @@ int main(int argc, char *argv[])
/* 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 send another `closing_signed`, otherwise
* if the node has sent a previous `shutdown` it MUST retransmit it.
* The funding node:
* - after `shutdown` has been received, AND no HTLCs remain in either
* commitment transaction:
* - SHOULD send a `closing_signed` message.
*/
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 as specified in [BOLT
* #3](03-transactions.md#closing-transaction).
*/
tx = close_tx(tmpctx, &cs, &channel_id,
scriptpubkey,
&funding_txid,
funding_txout,
funding_satoshi,
satoshi_out, funder, sent_fee, our_dust_limit);
/* BOLT #3:
*
* ## Closing Transaction
*...
* Each node offering a signature... MAY also eliminate its
* own output.
*/
/* (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(STATUS_FAIL_PEER_IO,
"Writing closing_signed");
/* Did we just agree with them? If so, we're done. */
if (sent_fee == last_received_fee)
break;
again:
/* Wait for them to say something interesting */
msg = closing_read_peer_msg(tmpctx, &cs, &channel_id);
/* 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))
peer_failed(PEER_FD, &cs, &channel_id,
"Expected closing_signed: %s",
tal_hex(trc, msg));
/* BOLT #2:
*
* The receiver MUST check `signature` is valid for either
* variant of close transaction specified in [BOLT
* #3](03-transactions.md#closing-transaction), and MUST fail
* the connection if it is not.
*/
tx = close_tx(tmpctx, &cs, &channel_id,
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];
/* BOLT #3:
*
* Each node offering a signature MUST subtract the
* fee given by `fee_satoshis` from the output to the
* funder; it MUST then remove any output below its
* own `dust_limit_satoshis`, and MAY also eliminate
* its own output.
*/
trimmed = close_tx(tmpctx, &cs, &channel_id,
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)) {
peer_failed(PEER_FD, &cs, &channel_id,
"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)
peer_failed(PEER_FD, &cs, &channel_id,
"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;
whose_turn = funder;
for (size_t i = 0; i < 2; i++, whose_turn = !whose_turn) {
if (whose_turn == LOCAL) {
send_offer(&cs, &channel_id, funding_pubkey,
funding_wscript,
scriptpubkey, &funding_txid, funding_txout,
funding_satoshi, satoshi_out, funder,
our_dust_limit, &secrets, offer[LOCAL]);
} else {
status_trace("Fee accepted.");
msg = towire_closing_received_signature(tmpctx,
&sig, tx);
if (!wire_sync_write(REQ_FD, take(msg)))
status_failed(STATUS_FAIL_MASTER_IO,
"Writing received to master: %s",
strerror(errno));
msg = wire_sync_read(tmpctx, REQ_FD);
if (!fromwire_closing_received_signature_reply(msg,NULL))
master_badmsg(WIRE_CLOSING_RECEIVED_SIGNATURE_REPLY,
msg);
limit_fee = received_fee;
offer[REMOTE]
= receive_offer(&cs, &channel_id, funding_pubkey,
funding_wscript,
scriptpubkey, &funding_txid,
funding_txout, funding_satoshi,
satoshi_out, funder,
our_dust_limit,
min_fee_to_accept);
}
}
/* BOLT #2:
*
* If `fee_satoshis` is equal to its previously sent
* `fee_satoshis`, the receiver SHOULD sign and broadcast the
* final closing transaction and MAY close the connection.
*/
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)
peer_failed(PEER_FD, &cs, &channel_id,
"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)
peer_failed(PEER_FD, &cs, &channel_id,
"Their fee jumped %"
PRIu64" to %"PRIu64
" when ours was %"PRIu64,
last_received_fee,
received_fee,
sent_fee);
/* Now we have first two points, we can init fee range. */
init_feerange(&feerange, commitment_fee, offer);
/* Now apply the one constraint from above (other is inside loop). */
adjust_feerange(&cs, &channel_id, &feerange,
offer[!whose_turn], !whose_turn);
/* Now any extra rounds required. */
while (offer[LOCAL] != offer[REMOTE]) {
/* If they differ, adjust feerate. */
adjust_feerange(&cs, &channel_id, &feerange,
offer[whose_turn], whose_turn);
/* Now its the other side's turn. */
whose_turn = !whose_turn;
if (whose_turn == LOCAL) {
offer[LOCAL] = adjust_offer(&cs, &channel_id,
&feerange, offer[REMOTE],
min_fee_to_accept);
send_offer(&cs, &channel_id, funding_pubkey,
funding_wscript,
scriptpubkey, &funding_txid, funding_txout,
funding_satoshi, satoshi_out, funder,
our_dust_limit, &secrets, offer[LOCAL]);
} else {
offer[REMOTE]
= receive_offer(&cs, &channel_id, funding_pubkey,
funding_wscript,
scriptpubkey, &funding_txid,
funding_txout, funding_satoshi,
satoshi_out, funder,
our_dust_limit,
min_fee_to_accept);
}
/* BOLT #2:
*
* ...otherwise it MUST 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)
peer_failed(PEER_FD, &cs, &channel_id,
"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! */

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