lnrpc: allow pubkey in SendToRoute #1944
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rpcserver.go
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| // If no pub key is given of the hop, the local channel | ||
| // graph needs to be queried to complete the information | ||
| // necessary for routing. | ||
| routeHop, err = unmarshallHopByChannelLookup(graph, |
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Regarding commit structure: it looks like this change (extracting logic into unmarshallHopByChannelLookup) could be done in an individual commit.
rpcserver.go
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| "channel ID for hop (%d): %v", i, err) | ||
| var routeHop *routing.Hop | ||
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| if hop.PubKey == "" { |
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I think I would prefer this check be done inside the unmarshal method. Shouldn't be a problem passing in the graph even though it might not be needed.
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My goal was to have a version of unmarshall that does not have that dependency. I refactored it into a form that satisfies both our requirements.
rpcserver.go
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| @@ -3509,57 +3509,109 @@ func (r *rpcServer) marshallRoute(route *routing.Route) *lnrpc.Route { | |||
| Fee: int64(fee.ToSatoshis()), | |||
| FeeMsat: int64(fee), | |||
| Expiry: uint32(hop.OutgoingTimeLock), | |||
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| // Include public key of hop in response, so that | |||
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I think this comment belongs by the definition of the PubKey field.
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| @@ -3509,6 +3509,8 @@ func (r *rpcServer) marshallRoute(route *routing.Route) *lnrpc.Route { | |||
| Fee: int64(fee.ToSatoshis()), | |||
| FeeMsat: int64(fee), | |||
| Expiry: uint32(hop.OutgoingTimeLock), | |||
| PubKey: hex.EncodeToString( | |||
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I thought so too, but this is what gofmt does.
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Maybe this works?
PubKey: hex.EncodeToString(
hop.PubKeyBytes[:],
),
}
rpcserver.go
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| // unmarshallHop unmarshalls an rpc hop that may or may not contain a node | ||
| // pubkey. | ||
| func unmarshallHop(graph *channeldb.ChannelGraph, hop *lnrpc.Hop, | ||
| prevNodePubKey []byte) (*routing.Hop, error) { |
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prevNodePubKey should be made [33]byte
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Why? This way there is less byte copying.
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It makes the length clear, and makes sure it is non-nil. I don't think any extra byte copying makes a difference in this case.
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Changed. Not sure it was worth it. It is a minor thing which to me is also a matter of preference.
By passing a pubkey into SendToRoute, it becomes unnecessary for lnd to query the channel graph to retrieve the hop pubkey. This allows routes over private channels that are not present in the graph.
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The information in the
RouteRPC message is not enough to directly send out the payment. First the local channel graph needs to be queried to complete the data. A lookup is executed to retrieve the public key of a node based on channel id. This does not work with private channels.In this PR, we allow the hop pubkeys to be passed in so that execution of the payment becomes independent of the channel graph.
It is also a step towards the unbundling of lnd. (maybe, in the future, we get a node that doesn't track the channel graph at all anymore and is just a payment executor. mobile maybe?)
Fixes #2139.