multifundchannel: use `excess_as_change` flag to simplify logic.
This was added to fundpsbt/utxopsbt in v0.10, but the spender plugin didn't take advantage of it, instead calculating its own change amount and output. Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
This commit is contained in:
Rusty Russell
parent
37005b93d3
commit
2f0e13e793
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@ -15,14 +15,14 @@
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extern const struct chainparams *chainparams;
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/* Flag set when any of the destinations has a value of "all". */
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static bool has_all(const struct multifundchannel_command *mfc)
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/* Which destinations has a value of "all", or -1. */
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static struct multifundchannel_destination *all_dest(const struct multifundchannel_command *mfc)
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{
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for (size_t i = 0; i < tal_count(mfc->destinations); i++) {
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if (mfc->destinations[i].all)
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return true;
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return &mfc->destinations[i];
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}
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return false;
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return NULL;
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}
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size_t dest_count(const struct multifundchannel_command *mfc,
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@ -162,19 +162,15 @@ mfc_cleanup_done(struct command *cmd,
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return command_still_pending(cmd);
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}
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/* Cleans up a txid by doing `txdiscard` on it. */
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static void
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mfc_cleanup_psbt(struct command *cmd,
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struct multifundchannel_cleanup *cleanup,
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struct wally_psbt *psbt)
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static struct command_result *unreserve_call(struct command *cmd,
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struct wally_psbt *psbt,
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void *cb, void *cbdata)
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{
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struct wally_psbt *pruned_psbt;
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struct out_req *req = jsonrpc_request_start(cmd->plugin,
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cmd,
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"unreserveinputs",
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&mfc_cleanup_done,
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&mfc_cleanup_done,
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cleanup);
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cb, cb, cbdata);
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/* We might have peer's inputs on this, get rid of them */
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tal_wally_start();
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@ -191,7 +187,16 @@ mfc_cleanup_psbt(struct command *cmd,
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json_add_psbt(req->js, "psbt", take(pruned_psbt));
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json_add_u32(req->js, "reserve", 2016);
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send_outreq(cmd->plugin, req);
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return send_outreq(cmd->plugin, req);
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}
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/* Cleans up a txid by doing `txdiscard` on it. */
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static void
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mfc_cleanup_psbt(struct command *cmd,
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struct multifundchannel_cleanup *cleanup,
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struct wally_psbt *psbt)
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{
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unreserve_call(cmd, psbt, mfc_cleanup_done, cleanup);
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}
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/* Cleans up a `openchannel_init` by doing `openchannel_abort` for the channel*/
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@ -820,7 +825,8 @@ perform_fundchannel_complete(struct multifundchannel_command *mfc)
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return command_still_pending(mfc->cmd);
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}
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/*~ The PSBT we are holding currently has no outputs.
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/*~ The PSBT we are holding currently has no outputs
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(except an optional change output).
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We now proceed to filling in those outputs now that
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we know what the funding scriptpubkeys are.
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@ -856,7 +862,7 @@ perform_funding_tx_finalize(struct multifundchannel_command *mfc)
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/* Construct a deck of destinations. */
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deck = tal_arr(tmpctx, struct multifundchannel_destination *,
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v1_dest_count + mfc->change_needed);
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v1_dest_count);
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deck_i = 0;
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for (i = 0; i < tal_count(mfc->destinations); i++) {
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@ -867,10 +873,6 @@ perform_funding_tx_finalize(struct multifundchannel_command *mfc)
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deck[deck_i++] = &mfc->destinations[i];
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}
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/* Add a NULL into the deck as a proxy for change output, if
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* needed. */
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if (mfc->change_needed)
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deck[v1_dest_count] = NULL;
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/* Fisher-Yates shuffle. */
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for (i = tal_count(deck); i > 1; --i) {
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size_t j = pseudorand(i);
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@ -884,11 +886,12 @@ perform_funding_tx_finalize(struct multifundchannel_command *mfc)
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/* Now that we have our outputs shuffled, add outputs to the PSBT. */
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for (unsigned int outnum = 0; outnum < tal_count(deck); ++outnum) {
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struct multifundchannel_destination *dest;
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if (outnum != 0)
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tal_append_fmt(&content, ", ");
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if (deck[outnum]) {
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/* Funding outpoint. */
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struct multifundchannel_destination *dest;
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dest = deck[outnum];
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(void) psbt_insert_output(mfc->psbt,
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dest->funding_script,
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@ -904,18 +907,6 @@ perform_funding_tx_finalize(struct multifundchannel_command *mfc)
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type_to_string(tmpctx,
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struct amount_sat,
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&dest->amount));
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} else {
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/* Change output. */
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assert(mfc->change_needed);
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(void) psbt_insert_output(mfc->psbt,
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mfc->change_scriptpubkey,
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mfc->change_amount,
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outnum);
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tal_append_fmt(&content, "change: %s",
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type_to_string(tmpctx,
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struct amount_sat,
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&mfc->change_amount));
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}
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}
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if (v2_dest_count > 0) {
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@ -1206,139 +1197,19 @@ mfc_psbt_acquired(struct multifundchannel_command *mfc)
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return perform_channel_start(mfc);
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}
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/* Limited recursion if we discover 'all' is too big for non-wumbo! */
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static struct command_result *
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after_newaddr(struct command *cmd,
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perform_fundpsbt(struct multifundchannel_command *mfc, u32 feerate);
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static struct command_result *
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retry_fundpsbt_capped_all(struct command *cmd,
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const char *buf,
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const jsmntok_t *result,
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struct multifundchannel_command *mfc)
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{
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const jsmntok_t *field;
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field = json_get_member(buf, result, "bech32");
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if (!field)
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plugin_err(cmd->plugin,
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"No bech32 field in newaddr result: %.*s",
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json_tok_full_len(result),
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json_tok_full(buf, result));
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if (json_to_address_scriptpubkey(mfc, chainparams, buf, field,
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&mfc->change_scriptpubkey)
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!= ADDRESS_PARSE_SUCCESS)
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plugin_err(cmd->plugin,
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"Unparseable bech32 field in newaddr result: %.*s",
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json_tok_full_len(result),
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json_tok_full(buf, result));
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return mfc_psbt_acquired(mfc);
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}
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static struct command_result *
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acquire_change_address(struct multifundchannel_command *mfc)
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{
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struct out_req *req;
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req = jsonrpc_request_start(mfc->cmd->plugin, mfc->cmd,
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"newaddr",
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&after_newaddr, &mfc_forward_error,
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mfc);
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json_add_string(req->js, "addresstype", "bech32");
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return send_outreq(mfc->cmd->plugin, req);
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}
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static struct command_result *
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handle_mfc_change(struct multifundchannel_command *mfc)
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{
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size_t change_weight;
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struct amount_sat change_fee, fee_paid, total_fee;
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struct amount_sat change_min_limit;
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/* Determine if adding a change output is worth it.
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* Get the weight of a change output and how much it
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* costs.
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*/
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change_weight = bitcoin_tx_output_weight(
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BITCOIN_SCRIPTPUBKEY_P2WPKH_LEN);
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/* To avoid 'off-by-one' errors due to rounding down
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* (which we do in `amount_tx_fee`), we find the total calculated
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* fees (estimated_weight + change weight @ feerate) and subtract
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* the originally calculated fees (estimated_weight @ feerate) */
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fee_paid = amount_tx_fee(mfc->feerate_per_kw,
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mfc->estimated_final_weight);
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total_fee = amount_tx_fee(mfc->feerate_per_kw,
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mfc->estimated_final_weight + change_weight);
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if (!amount_sat_sub(&change_fee, total_fee, fee_paid))
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abort();
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/* The limit is equal to the change_fee plus the dust limit. */
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if (!amount_sat_add(&change_min_limit,
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change_fee, chainparams->dust_limit))
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plugin_err(mfc->cmd->plugin,
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"Overflow dust limit and change fee.");
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/* Is the excess over the limit? */
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if (amount_sat_greater(mfc->excess_sat, change_min_limit)) {
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bool ok = amount_sat_sub(&mfc->change_amount,
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mfc->excess_sat, change_fee);
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assert(ok);
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mfc->change_needed = true;
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if (!mfc->change_scriptpubkey)
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return acquire_change_address(mfc);
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} else
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mfc->change_needed = false;
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return mfc_psbt_acquired(mfc);
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}
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/* If one of the destinations specified "all", figure out how much that is. */
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static struct command_result *
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compute_mfc_all(struct multifundchannel_command *mfc)
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{
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size_t all_index = SIZE_MAX;
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struct multifundchannel_destination *all_dest;
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assert(has_all(mfc));
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for (size_t i = 0; i < tal_count(mfc->destinations); ++i) {
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struct multifundchannel_destination *dest;
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dest = &mfc->destinations[i];
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if (dest->all) {
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assert(all_index == SIZE_MAX);
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all_index = i;
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continue;
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}
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/* Subtract the amount from the excess. */
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if (!amount_sat_sub(&mfc->excess_sat,
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mfc->excess_sat, dest->amount))
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/* Not enough funds! */
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return mfc_fail(mfc, FUND_CANNOT_AFFORD,
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"Insufficient funds.");
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}
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assert(all_index != SIZE_MAX);
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all_dest = &mfc->destinations[all_index];
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/* Is the excess above the dust amount? */
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if (amount_sat_less(mfc->excess_sat, chainparams->dust_limit))
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return mfc_fail(mfc, FUND_OUTPUT_IS_DUST,
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"Output 'all' %s would be dust",
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type_to_string(tmpctx, struct amount_sat,
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&mfc->excess_sat));
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/* Assign the remainder to the 'all' output. */
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all_dest->amount = mfc->excess_sat;
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if (!feature_negotiated(plugin_feature_set(mfc->cmd->plugin),
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all_dest->their_features,
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OPT_LARGE_CHANNELS)
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&& amount_sat_greater(all_dest->amount,
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chainparams->max_funding))
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all_dest->amount = chainparams->max_funding;
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/* Remove it from the excess. */
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bool ok = amount_sat_sub(&mfc->excess_sat,
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mfc->excess_sat, all_dest->amount);
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assert(ok);
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/* Remove the 'all' flag. */
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all_dest->all = false;
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/* Continue. */
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return handle_mfc_change(mfc);
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/* We've unreserved this, now free it and try again! */
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tal_free(mfc->psbt);
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return perform_fundpsbt(mfc, mfc->feerate_per_kw);
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}
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static struct command_result *
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@ -1348,7 +1219,7 @@ after_fundpsbt(struct command *cmd,
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struct multifundchannel_command *mfc)
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{
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const jsmntok_t *field;
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struct amount_msat msat;
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struct multifundchannel_destination *all;
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plugin_log(mfc->cmd->plugin, LOG_DBG,
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"mfc %"PRIu64": %s done.",
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@ -1379,17 +1250,38 @@ after_fundpsbt(struct command *cmd,
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if (!field || !json_to_u32(buf, field, &mfc->estimated_final_weight))
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goto fail;
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/* msat LOL. */
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all = all_dest(mfc);
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if (all) {
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struct amount_msat msat;
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/* excess_msat is amount to use for "all". */
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field = json_get_member(buf, result, "excess_msat");
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if (!field || !parse_amount_msat(&msat,
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buf + field->start,
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field->end - field->start)
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|| !amount_msat_to_sat(&mfc->excess_sat, msat))
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|| !amount_msat_to_sat(&all->amount, msat))
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goto fail;
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if (has_all(mfc))
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return compute_mfc_all(mfc);
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return handle_mfc_change(mfc);
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/* Remove the 'all' flag. */
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all->all = false;
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/* It's first grade, Spongebob! */
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if (!feature_negotiated(plugin_feature_set(mfc->cmd->plugin),
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all->their_features,
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OPT_LARGE_CHANNELS)
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&& amount_sat_greater(all->amount,
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chainparams->max_funding)) {
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/* Oh, crap! Set this amount and retry! */
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plugin_log(mfc->cmd->plugin, LOG_INFORM,
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"'all' was too large for non-wumbo channel, trimming from %s to %s",
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fmt_amount_sat(tmpctx, all->amount),
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fmt_amount_sat(tmpctx, chainparams->max_funding));
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all->amount = chainparams->max_funding;
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return unreserve_call(mfc->cmd, mfc->psbt,
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retry_fundpsbt_capped_all, mfc);
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}
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}
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return mfc_psbt_acquired(mfc);
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fail:
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plugin_err(mfc->cmd->plugin,
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@ -1446,7 +1338,7 @@ perform_fundpsbt(struct multifundchannel_command *mfc, u32 feerate)
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*/
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json_add_u32(req->js, "reserve", 2016);
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/* How much do we need to reserve? */
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if (has_all(mfc))
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if (all_dest(mfc) != NULL)
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json_add_string(req->js, "satoshi", "all");
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else {
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struct amount_sat sum = AMOUNT_SAT(0);
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@ -1511,6 +1403,8 @@ perform_fundpsbt(struct multifundchannel_command *mfc, u32 feerate)
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tal_fmt(tmpctx, "%u", 110));
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}
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/* Handle adding a change output if required. */
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json_add_bool(req->js, "excess_as_change", true);
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return send_outreq(mfc->cmd->plugin, req);
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}
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@ -2092,7 +1986,6 @@ json_multifundchannel(struct command *cmd,
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mfc->minchannels = minchannels ? *minchannels : tal_count(mfc->destinations);
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mfc->removeds = tal_arr(mfc, struct multifundchannel_removed, 0);
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mfc->psbt = NULL;
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mfc->change_scriptpubkey = NULL;
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mfc->txid = NULL;
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mfc->final_tx = NULL;
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mfc->final_txid = NULL;
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@ -218,21 +218,6 @@ struct multifundchannel_command {
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/* The expected weight of the PSBT after adding in all the outputs.
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* In weight units (sipa). */
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u32 estimated_final_weight;
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/* Excess satoshi from the PSBT.
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* If "all" this is the entire amount; if not "all" this is the
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* proposed change amount, which if dusty should be donated to
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* the miners.
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*/
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struct amount_sat excess_sat;
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/* A convenient change address. NULL at the start, filled in
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* if we detect we need it. */
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const u8 *change_scriptpubkey;
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/* Whether we need a change output. */
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bool change_needed;
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/* The change amount. */
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struct amount_sat change_amount;
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/* The txid of the final funding transaction. */
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struct bitcoin_txid *txid;
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@ -1,5 +1,6 @@
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from fixtures import * # noqa: F401,F403
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from fixtures import TEST_NETWORK
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from decimal import Decimal
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from ephemeral_port_reserve import reserve # type: ignore
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from pyln.client import RpcError, Millisatoshi
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import pyln.proto.wire as wire
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@ -1111,6 +1112,7 @@ def test_funding_all_too_much(node_factory):
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addr, txid = l1.fundwallet(2**24 + 10000)
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l1.rpc.fundchannel(l2.info['id'], "all")
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assert l1.daemon.is_in_log("'all' was too large for non-wumbo channel, trimming")
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# One reserved, confirmed output spent above, and one change.
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outputs = l1.rpc.listfunds()['outputs']
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@ -1842,7 +1844,14 @@ def test_multifunding_v1_v2_mixed(node_factory, bitcoind):
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{"id": '{}@localhost:{}'.format(l4.info['id'], l4.port),
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"amount": 50000}]
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l1.rpc.multifundchannel(destinations)
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# There should be change!
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tx = l1.rpc.multifundchannel(destinations)['tx']
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decoded = bitcoind.rpc.decoderawtransaction(tx)
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assert len(decoded['vout']) == len(destinations) + 1
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# Feerate should be about right, too!
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fee = Decimal(2000000) / 10**8 * len(decoded['vin']) - sum(v['value'] for v in decoded['vout'])
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assert 7450 < fee * 10**8 / decoded['weight'] * 1000 < 7550
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mine_funding_to_announce(bitcoind, [l1, l2, l3, l4], wait_for_mempool=1)
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for node in [l1, l2, l3, l4]:
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