multi: allow setting target confs for co-op close

This commit adds a new config option: "--coop-close-target-confs"
which allows a user to override the default target confirmations of 6
that is used to estimate a fee rate to use during a co-op closure
initiated by a remote peer.

config.go

@@ -89,6 +89,13 @@ const (
 	defaultAlias = ""
 	defaultColor = "#3399FF"
 
+	// defaultCoopCloseTargetConfs is the default confirmation target
+	// that will be used to estimate a fee rate to use during a
+	// cooperative channel closure initiated by a remote peer. By default
+	// we'll set this to a lax value since we weren't the ones that
+	// initiated the channel closure.
+	defaultCoopCloseTargetConfs = 6
+
 	// defaultHostSampleInterval is the default amount of time that the
 	// HostAnnouncer will wait between DNS resolutions to check if the
 	// backing IP of a host has changed.
@@ -273,6 +280,7 @@ type Config struct {
 	Color                         string        `long:"color" description:"The color of the node in hex format (i.e. '#3399FF'). Used to customize node appearance in intelligence services"`
 	MinChanSize                   int64         `long:"minchansize" description:"The smallest channel size (in satoshis) that we should accept. Incoming channels smaller than this will be rejected"`
 	MaxChanSize                   int64         `long:"maxchansize" description:"The largest channel size (in satoshis) that we should accept. Incoming channels larger than this will be rejected"`
+	CoopCloseTargetConfs          uint32        `long:"coop-close-target-confs" description:"The target number of blocks that a cooperative channel close transaction should confirm in. This is used to estimate the fee to use as the lower bound during fee negotiation for the channel closure."`
 
 	DefaultRemoteMaxHtlcs uint16 `long:"default-remote-max-htlcs" description:"The default max_htlc applied when opening or accepting channels. This value limits the number of concurrent HTLCs that the remote party can add to the commitment. The maximum possible value is 483."`
 
@@ -434,6 +442,7 @@ func DefaultConfig() Config {
 		Color:                         defaultColor,
 		MinChanSize:                   int64(funding.MinChanFundingSize),
 		MaxChanSize:                   int64(0),
+		CoopCloseTargetConfs:          defaultCoopCloseTargetConfs,
 		DefaultRemoteMaxHtlcs:         defaultRemoteMaxHtlcs,
 		NumGraphSyncPeers:             defaultMinPeers,
 		HistoricalSyncInterval:        discovery.DefaultHistoricalSyncInterval,