lightning-multifundchannel – Command for establishing many lightning channels

SYNOPSIS

multifundchannel destinations [feerate] [minconf] [utxos] [minchannels]

DESCRIPTION

The multifundchannel RPC command opens multiple payment channels with nodes by committing a single funding transaction to the blockchain that is shared by all channels.

If not already connected, multifundchannel will automatically attempt to connect; you may provide a @host:port hint appended to the node ID so that c-lightning can learn how to connect to the node; see lightning-connect(7).

Once the transaction is confirmed, normal channel operations may begin. Readiness is indicated by listpeers reporting a state of CHANNELD_NORMAL for the channel.

destinations is an array of objects, with the fields:

  • id is the node ID, with an optional @host:port appended to it in a manner understood by connect; see lightning-connect(7). Each entry in the destinations array must have a unique node id.
  • amount is the amount in satoshis taken from the internal wallet to fund the channel. The string all can be used to specify all available funds (or 16,777,215 satoshi if more is available and large channels were not negotiated with the peer). Otherwise it is in satoshi precision; it can be a whole number, a whole number ending in sat, a whole number ending in 000msat, or a number with 1 to 8 decimal places ending in btc. The value cannot be less than the dust limit, currently 546 satoshi as of this writing, nor more than 16,777,215 satoshi (unless large channels were negotiated with the peer).
  • announce is an optional flag that indicates whether to announce the channel with this, default true. If set to false, the channel is unpublished.
  • push_msat is the amount of millisatoshis to outright give to the node. This is a gift to the peer, and you do not get a proof-of-payment out of this.

There must be at least one entry in destinations; it cannot be an empty array.

feerate is an optional feerate used for the opening transaction and as initial feerate for commitment and HTLC transactions. It can be one of the strings urgent (aim for next block), normal (next 4 blocks or so) or slow (next 100 blocks or so) to use lightningd’s internal estimates: normal is the default.

Otherwise, feerate is a number, with an optional suffix: perkw means the number is interpreted as satoshi-per-kilosipa (weight), and perkb means it is interpreted bitcoind-style as satoshi-per-kilobyte. Omitting the suffix is equivalent to perkb.

minconf specifies the minimum number of confirmations that used outputs should have. Default is 1.

utxos specifies the utxos to be used to fund the channel, as an array of “txid:vout”.

minchannels, if specified, will re-attempt funding as long as at least this many peers remain (must not be zero). The multifundchannel command will only fail if too many peers fail the funding process.

RETURN VALUE

On success, the tx and txid of the signed and broadcsted funding transaction is returned. This command opens multiple channels with a single large transaction, thus only one transaction is returned.

If minchannels was specified and is less than the number of destinations, then it is possible that one or more of the destinations do not have a channel even if multifundchannel succeeded.

An array of channel_ids is returned; each entry of the array is an object, with an id field being the node ID of the peer, an outnum field being the output number of the transaction that anchors this channel, and channel_id field being the channel ID with that peer.

An array of failed is returned, which contains the destinations that were removed due to failures (this can only happen on success if minchannels was specified). Each entry of the array is an object, with an id field being the node ID of the removed peer, method field describing what phase of funding the peer failed, and error field of the exact error returned by the method.

On failure, none of the channels are created.

The following error codes may occur:

  • -1: Catchall nonspecific error.
  • 300: The maximum allowed funding amount is exceeded.
  • 301: There are not enough funds in the internal wallet (including fees) to create the transaction.
  • 302: The output amount is too small, and would be considered dust.
  • 303: Broadcasting of the funding transaction failed, the internal call to bitcoin-cli returned with an error.

Failure may also occur if lightningd and the peer cannot agree on channel parameters (funding limits, channel reserves, fees, etc.). See lightning-fundchannel_start(7) and lightning-fundchannel_complete(7).

There may be rare edge cases where a communications failure later in the channel funding process will cancel the funding locally, but the peer thinks the channel is already waiting for funding lockin. In that case, the next time we connect to the peer, our node will tell the peer to forget the channel, but some nodes (in particular, c-lightning nodes) will disconnect when our node tells them to forget the channel. If you immediately multifundchannel with that peer, it could trigger this connect-forget-disconnect behavior, causing the second multifundchannel to fail as well due to disconnection. Doing a connect with the peers separately, and waiting for a few seconds, should help clear this hurdle; running multifundchannel a third time would also clear this.

AUTHOR

ZmnSCPxj <ZmnSCPxj@protonmail.com> is mainly responsible.

SEE ALSO

lightning-connect(7), lightning-listfunds(), lightning-listpeers(7), lightning-fundchannel(7)