routing+discovery: extract local channel manager

The policy update logic that resided part in the gossiper and
part in the rpc server is extracted into its own object.

This prepares for additional validation logic to be added for policy
updates that would otherwise make the gossiper heavier.

It is also a small first step towards separation of our own channel data
from the rest of the graph.

htlcswitch/switch.go

@@ -431,7 +431,7 @@ func (s *Switch) SendHTLC(firstHop lnwire.ShortChannelID, paymentID uint64,
 // forwarding policies for all links have been updated, or the switch shuts
 // down.
 func (s *Switch) UpdateForwardingPolicies(
-	chanPolicies map[wire.OutPoint]*channeldb.ChannelEdgePolicy) {
+	chanPolicies map[wire.OutPoint]ForwardingPolicy) {
 
 	log.Tracef("Updating link policies: %v", newLogClosure(func() string {
 		return spew.Sdump(chanPolicies)
@@ -440,7 +440,7 @@ func (s *Switch) UpdateForwardingPolicies(
 	s.indexMtx.RLock()
 
 	// Update each link in chanPolicies.
-	for targetLink := range chanPolicies {
+	for targetLink, policy := range chanPolicies {
 		cid := lnwire.NewChanIDFromOutPoint(&targetLink)
 
 		link, ok := s.linkIndex[cid]
@@ -450,28 +450,12 @@ func (s *Switch) UpdateForwardingPolicies(
 			continue
 		}
 
-		newPolicy := dbPolicyToFwdingPolicy(
-			chanPolicies[*link.ChannelPoint()],
-		)
-		link.UpdateForwardingPolicy(newPolicy)
+		link.UpdateForwardingPolicy(policy)
 	}
 
 	s.indexMtx.RUnlock()
 }
 
-// dbPolicyToFwdingPolicy is a helper function that converts a channeldb
-// ChannelEdgePolicy into a ForwardingPolicy struct for the purpose of updating
-// the forwarding policy of a link.
-func dbPolicyToFwdingPolicy(policy *channeldb.ChannelEdgePolicy) ForwardingPolicy {
-	return ForwardingPolicy{
-		BaseFee:       policy.FeeBaseMSat,
-		FeeRate:       policy.FeeProportionalMillionths,
-		TimeLockDelta: uint32(policy.TimeLockDelta),
-		MinHTLC:       policy.MinHTLC,
-		MaxHTLC:       policy.MaxHTLC,
-	}
-}
-
 // forward is used in order to find next channel link and apply htlc update.
 // Also this function is used by channel links itself in order to forward the
 // update after it has been included in the channel.