htlcswitch: Remove constructor functions for htlcPacket.

The constructor functions have no additional logic other than passing
function parameters into struct fields. Given the large function
signatures, it is more clear to directly construct the htlcPacket in
client code than call a function with lots of positional arguments.

htlcswitch/link.go

@@ -698,14 +698,15 @@ func (l *channelLink) handleDownStreamPkt(pkt *htlcPacket, isReProcess bool) {
 					isObfuscated = true
 				}
 
-				upddateFail := &lnwire.UpdateFailHTLC{
-					Reason: reason,
+				failPkt := &htlcPacket{
+					src:          l.ShortChanID(),
+					payHash:      htlc.PaymentHash,
+					amount:       htlc.Amount,
+					isObfuscated: isObfuscated,
+					htlc: &lnwire.UpdateFailHTLC{
+						Reason: reason,
+					},
 				}
-				failPkt := newFailPacket(
-					l.ShortChanID(), upddateFail,
-					htlc.PaymentHash, htlc.Amount,
-					isObfuscated,
-				)
 
 				// TODO(roasbeef): need to identify if sent
 				// from switch so don't need to obfuscate
@@ -1177,11 +1178,14 @@ func (l *channelLink) processLockedInHtlcs(
 		// received. So we'll forward the HTLC to the switch which
 		// will handle propagating the settle to the prior hop.
 		case lnwallet.Settle:
-			settleUpdate := &lnwire.UpdateFufillHTLC{
-				PaymentPreimage: pd.RPreimage,
+			settlePacket := &htlcPacket{
+				src:     l.ShortChanID(),
+				payHash: pd.RHash,
+				amount:  pd.Amount,
+				htlc: &lnwire.UpdateFufillHTLC{
+					PaymentPreimage: pd.RPreimage,
+				},
 			}
-			settlePacket := newSettlePacket(l.ShortChanID(),
-				settleUpdate, pd.RHash, pd.Amount)
 
 			// Add the packet to the batch to be forwarded, and
 			// notify the overflow queue that a spare spot has been
@@ -1196,12 +1200,15 @@ func (l *channelLink) processLockedInHtlcs(
 		case lnwallet.Fail:
 			// Fetch the reason the HTLC was cancelled so we can
 			// continue to propagate it.
-			failUpdate := &lnwire.UpdateFailHTLC{
-				Reason: lnwire.OpaqueReason(pd.FailReason),
-				ChanID: l.ChanID(),
+			failPacket := &htlcPacket{
+				src:          l.ShortChanID(),
+				payHash:      pd.RHash,
+				amount:       pd.Amount,
+				isObfuscated: false,
+				htlc: &lnwire.UpdateFailHTLC{
+					Reason: lnwire.OpaqueReason(pd.FailReason),
+				},
 			}
-			failPacket := newFailPacket(l.ShortChanID(), failUpdate,
-				pd.RHash, pd.Amount, false)
 
 			// Add the packet to the batch to be forwarded, and
 			// notify the overflow queue that a spare spot has been
@@ -1564,8 +1571,12 @@ func (l *channelLink) processLockedInHtlcs(
 					continue
 				}
 
-				updatePacket := newAddPacket(l.ShortChanID(),
-					fwdInfo.NextHop, addMsg, obfuscator)
+				updatePacket := &htlcPacket{
+					src:        l.ShortChanID(),
+					dest:       fwdInfo.NextHop,
+					htlc:       addMsg,
+					obfuscator: obfuscator,
+				}
 				packetsToForward = append(packetsToForward, updatePacket)
 			}
 		}