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Needed for v2 of channel opens, where the minimum weight is 110; a 'simple utxo' (sig + key) weighs in at 107, so we a need a way to establish a floor for this case. Changelog-Added: JSON-RPC: fundpsbt/utxopsbt have new param, `min_witness_utxo`, which sets a floor for the weight calculation of an added input
113 lines
4.0 KiB
Groff
Generated
113 lines
4.0 KiB
Groff
Generated
.TH "LIGHTNING-FUNDPSBT" "7" "" "" "lightning-fundpsbt"
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.SH NAME
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lightning-fundpsbt - Command to populate PSBT inputs from the wallet
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.SH SYNOPSIS
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\fBfundpsbt\fR \fIsatoshi\fR \fIfeerate\fR \fIstartweight\fR [\fIminconf\fR] [\fIreserve\fR] [\fIlocktime\fR] [\fImin_witness_weight\fR]
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.SH DESCRIPTION
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\fBfundpsbt\fR is a low-level RPC command which creates a PSBT using unreserved
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inputs in the wallet, optionally reserving them as well\.
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\fIsatoshi\fR is the minimum satoshi value of the output(s) needed (or the
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string "all" meaning use all unreserved inputs)\. If a value, it can
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be a whole number, a whole number ending in \fIsat\fR, a whole number
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ending in \fI000msat\fR, or a number with 1 to 8 decimal places ending in
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\fIbtc\fR\.
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\fIfeerate\fR can be one of the feerates listed in \fBlightning-feerates\fR(7),
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or one of the strings \fIurgent\fR (aim for next block), \fInormal\fR (next 4
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blocks or so) or \fIslow\fR (next 100 blocks or so) to use lightningd’s
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internal estimates\. It can also be a \fIfeerate\fR is a number, with an
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optional suffix: \fIperkw\fR means the number is interpreted as
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satoshi-per-kilosipa (weight), and \fIperkb\fR means it is interpreted
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bitcoind-style as satoshi-per-kilobyte\. Omitting the suffix is
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equivalent to \fIperkb\fR\.
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\fIstartweight\fR is the weight of the transaction before \fIfundpsbt\fR has
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added any inputs\.
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\fIminconf\fR specifies the minimum number of confirmations that used
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outputs should have\. Default is 1\.
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\fIreserve\fR is a boolean: if true (the default), then \fIreserveinputs\fR is
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called (successfully, with \fIexclusive\fR true) on the returned PSBT\.
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\fIlocktime\fR is an optional locktime: if not set, it is set to a recent
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block height\.
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\fImin_witness_weight\fR is an optional minimum weight to use for a UTXO's
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witness\. If the actual witness weight is greater than the provided minimum,
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the actual witness weight will be used\.
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.SH EXAMPLE USAGE
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Let's assume the caller is trying to produce a 100,000 satoshi output\.
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First, the caller estimates the weight of the core (typically 42) and
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known outputs of the transaction (typically (9 + scriptlen) * 4)\. For
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a simple P2WPKH it's a 22 byte scriptpubkey, so that's 124 weight\.
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It calls "\fIfundpsbt\fR 100000sat slow 166", which succeeds, and returns
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the \fIpsbt\fR and \fIfeerate_per_kw\fR it used, the \fIestimated_final_weight\fR
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and any \fIexcess_msat\fR\.
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If \fIexcess_msat\fR is greater than the cost of adding a change output,
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the caller adds a change output randomly to position 0 or 1 in the
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PSBT\. Say \fIfeerate_per_kw\fR is 253, and the change output is a P2WPKH
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(weight 124), the cost is around 31 sats\. With the dust limit disallowing
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payments below 546 satoshis, we would only create a change output
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if \fIexcess_msat\fR was greater or equal to 31 + 546\.
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.SH RETURN VALUE
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On success, returns the \fIpsbt\fR containing the inputs, \fIfeerate_per_kw\fR
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showing the exact numeric feerate it used, \fIestimated_final_weight\fR for
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the estimated weight of the transaction once fully signed, and
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\fIexcess_msat\fR containing the amount above \fIsatoshi\fR which is
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available\. This could be zero, or dust\. If \fIsatoshi\fR was "all",
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then \fIexcess_msat\fR is the entire amount once fees are subtracted
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for the weights of the inputs and startweight\.
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If \fIreserve\fR was true, then a \fIreservations\fR array is returned,
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exactly like \fIreserveinputs\fR\.
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On error the returned object will contain \fBcode\fR and \fBmessage\fR properties,
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with \fBcode\fR being one of the following:
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.RS
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.IP \[bu]
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-32602: If the given parameters are wrong\.
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.IP \[bu]
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-1: Catchall nonspecific error\.
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.IP \[bu]
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301: Insufficient UTXOs to meet \fIsatoshi\fR value\.
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.RE
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.SH AUTHOR
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Rusty Russell \fI<rusty@rustcorp.com.au\fR> is mainly responsible\.
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.SH SEE ALSO
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\fBlightning-utxopsbt\fR(7), \fBlightning-reserveinputs\fR(7), \fBlightning-unreserveinputs\fR(7)\.
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.SH RESOURCES
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Main web site: \fIhttps://github.com/ElementsProject/lightning\fR
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\" SHA256STAMP:a8b9705274638127c2f5ec4e97ed94e6d7f6b6b10a76c2248e8bc8b36dd804ff
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