lnwire: channels are now identified by outpoint

This commit modifies most of the wire messages to uniquely identify any
*active* channels by their funding output. This allows the wire
protocol to support funding transactions which open several channels in
parallel.

Any pending channels created by partial completion of the funding
workflow are to be identified by a uint64 initialized by both sides as
follows: the initiator of the connection starts from 0, while the
listening node starts from (1 << 63). These pending channel identifiers
are expected to be monotonically increasing with each new funding
workflow between two nodes. This identifier is volatile w.r.t to each
connection initiation.

lnwire/commit_revocation.go

@@ -3,12 +3,14 @@ package lnwire
 import (
 	"fmt"
 	"io"
+
+	"github.com/roasbeef/btcd/wire"
 )
 
 // CommitRevocation is sent by either side once a CommitSignature message has
 // been received, and validated. This message serves to revoke the prior
 // commitment transaction, which was the most up to date version until a
-// CommitSignature message referencing the specified ChannelID was received.
+// CommitSignature message referencing the specified ChannelPoint was received.
 // Additionally, this message also piggyback's the next revocation hash that
 // Alice should use when constructing the Bob's version of the next commitment
 // transaction (which would be done before sending a CommitSignature message).
@@ -16,9 +18,9 @@ import (
 // modifying Bob's commitment transaction without first asking for a revocation
 // hash initially.
 type CommitRevocation struct {
-	// ChannelID uniquely identifies to which currently active channel this
+	// ChannelPoint uniquely identifies to which currently active channel this
 	// CommitRevocation applies to.
-	ChannelID uint64
+	ChannelPoint *wire.OutPoint
 
 	// Revocation is the pre-image to the revocation hash of the now prior
 	// commitment transaction.
@@ -44,11 +46,11 @@ var _ Message = (*CommitRevocation)(nil)
 //
 // This is part of the lnwire.Message interface.
 func (c *CommitRevocation) Decode(r io.Reader, pver uint32) error {
-	// ChannelID (8)
+	// ChannelPoint (8)
 	// NextRevocationHash (20)
 	// Revocation (20)
 	err := readElements(r,
-		&c.ChannelID,
+		&c.ChannelPoint,
 		&c.NextRevocationHash,
 		&c.Revocation,
 	)
@@ -65,7 +67,7 @@ func (c *CommitRevocation) Decode(r io.Reader, pver uint32) error {
 // This is part of the lnwire.Message interface.
 func (c *CommitRevocation) Encode(w io.Writer, pver uint32) error {
 	err := writeElements(w,
-		c.ChannelID,
+		c.ChannelPoint,
 		c.NextRevocationHash,
 		c.Revocation,
 	)
@@ -89,8 +91,8 @@ func (c *CommitRevocation) Command() uint32 {
 //
 // This is part of the lnwire.Message interface.
 func (c *CommitRevocation) MaxPayloadLength(uint32) uint32 {
-	// 8 + 20 + 20
-	return 48
+	// 36 + 20 + 20
+	return 76
 }
 
 // Validate performs any necessary sanity checks to ensure all fields present
@@ -107,7 +109,7 @@ func (c *CommitRevocation) Validate() error {
 // This is part of the lnwire.Message interface.
 func (c *CommitRevocation) String() string {
 	return fmt.Sprintf("\n--- Begin CommitRevocation ---\n") +
-		fmt.Sprintf("ChannelID:\t%d\n", c.ChannelID) +
+		fmt.Sprintf("ChannelPoint:\t%d\n", c.ChannelPoint) +
 		fmt.Sprintf("NextRevocationHash:\t%x\n", c.NextRevocationHash) +
 		fmt.Sprintf("Revocation:\t%x\n", c.Revocation) +
 		fmt.Sprintf("--- End CommitRevocation ---\n")