Struct lightning::util::config::ChannelConfig

pub struct ChannelConfig {
    pub forwarding_fee_proportional_millionths: u32,
    pub forwarding_fee_base_msat: u32,
    pub cltv_expiry_delta: u16,
    pub announced_channel: bool,
    pub commit_upfront_shutdown_pubkey: bool,
    pub max_dust_htlc_exposure_msat: u64,
    pub force_close_avoidance_max_fee_satoshis: u64,
}

Options which apply on a per-channel basis and may change at runtime or based on negotiation with our counterparty.

Fields

forwarding_fee_proportional_millionths: u32

Amount (in millionths of a satoshi) charged per satoshi for payments forwarded outbound over the channel. This may be allowed to change at runtime in a later update, however doing so must result in update messages sent to notify all nodes of our updated relay fee.

Default value: 0.

forwarding_fee_base_msat: u32

Amount (in milli-satoshi) charged for payments forwarded outbound over the channel, in excess of forwarding_fee_proportional_millionths. This may be allowed to change at runtime in a later update, however doing so must result in update messages sent to notify all nodes of our updated relay fee.

The default value of a single satoshi roughly matches the market rate on many routing nodes as of July 2021. Adjusting it upwards or downwards may change whether nodes route through this node.

Default value: 1000.

cltv_expiry_delta: u16

The difference in the CLTV value between incoming HTLCs and an outbound HTLC forwarded over the channel this config applies to.

This is analogous to ChannelHandshakeConfig::our_to_self_delay but applies to in-flight HTLC balance when a channel appears on-chain whereas ChannelHandshakeConfig::our_to_self_delay applies to the remaining (non-HTLC-encumbered) balance.

Thus, for HTLC-encumbered balances to be enforced on-chain when a channel is force-closed, we (or one of our watchtowers) MUST be online to check for broadcast of the current commitment transaction at least once per this many blocks (minus some margin to allow us enough time to broadcast and confirm a transaction, possibly with time in between to RBF the spending transaction).

Default value: 72 (12 hours at an average of 6 blocks/hour). Minimum value: MIN_CLTV_EXPIRY_DELTA, any values less than this will be treated as MIN_CLTV_EXPIRY_DELTA instead.

announced_channel: bool

Set to announce the channel publicly and notify all nodes that they can route via this channel.

This should only be set to true for nodes which expect to be online reliably.

As the node which funds a channel picks this value this will only apply for new outbound channels unless ChannelHandshakeLimits::force_announced_channel_preference is set.

This cannot be changed after the initial channel handshake.

Default value: false.

commit_upfront_shutdown_pubkey: bool

When set, we commit to an upfront shutdown_pubkey at channel open. If our counterparty supports it, they will then enforce the mutual-close output to us matches what we provided at intialization, preventing us from closing to an alternate pubkey.

This is set to true by default to provide a slight increase in security, though ultimately any attacker who is able to take control of a channel can just as easily send the funds via lightning payments, so we never require that our counterparties support this option.

This cannot be changed after a channel has been initialized.

Default value: true.

max_dust_htlc_exposure_msat: u64

Limit our total exposure to in-flight HTLCs which are burned to fees as they are too small to claim on-chain.

When an HTLC present in one of our channels is below a “dust” threshold, the HTLC will not be claimable on-chain, instead being turned into additional miner fees if either party force-closes the channel. Because the threshold is per-HTLC, our total exposure to such payments may be sustantial if there are many dust HTLCs present when the channel is force-closed.

This limit is applied for sent, forwarded, and received HTLCs and limits the total exposure across all three types per-channel. Setting this too low may prevent the sending or receipt of low-value HTLCs on high-traffic nodes, and this limit is very important to prevent stealing of dust HTLCs by miners.

Default value: 5_000_000 msat.

force_close_avoidance_max_fee_satoshis: u64

The additional fee we’re willing to pay to avoid waiting for the counterparty’s to_self_delay to reclaim funds.

When we close a channel cooperatively with our counterparty, we negotiate a fee for the closing transaction which both sides find acceptable, ultimately paid by the channel funder/initiator.

When we are the funder, because we have to pay the channel closing fee, we bound the acceptable fee by our Background and Normal fees, with the upper bound increased by this value. Because the on-chain fee we’d pay to force-close the channel is kept near our Normal feerate during normal operation, this value represents the additional fee we’re willing to pay in order to avoid waiting for our counterparty’s to_self_delay to reclaim our funds.

When we are not the funder, we require the closing transaction fee pay at least our Background fee estimate, but allow our counterparty to pay as much fee as they like. Thus, this value is ignored when we are not the funder.

Default value: 1000 satoshis.

Trait Implementations

impl Clone for ChannelConfig

fn clone(&self) -> ChannelConfig

Returns a copy of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for ChannelConfig

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Default for ChannelConfig

fn default() -> Self

Provides sane defaults for most configurations (but with zero relay fees!).

impl Readable for ChannelConfig

fn read<R: Read>(reader: &mut R) -> Result<Self, DecodeError>

Reads a Self in from the given Read

impl Writeable for ChannelConfig

fn write<W: Writer>(&self, writer: &mut W) -> Result<(), Error>

Writes self out to the given Writer

fn serialized_length(&self) -> usize

Gets the length of this object after it has been serialized. This can be overridden to optimize cases where we prepend an object with its length.

fn encode(&self) -> Vec<u8>

Writes self out to a Vec

fn encode_with_len(&self) -> Vec<u8>

Writes self out to a Vec

impl Copy for ChannelConfig