`getroutes`: amounts and delays are wrong

[daywalker90]

I'm trying the new getroutes @rustyrussell and i encountered this:

regtest l1->l2->l3

[GetroutesRoutes { amount_msat: Amount { msat: 100000000 }, path: [GetroutesRoutesPath { amount_msat: Amount { msat: 100001001 }, delay: 11, direction: 1, next_node_id: PublicKey(*snip*), short_channel_id: ShortChannelId(114349209354240) }, GetroutesRoutesPath { amount_msat: Amount { msat: 100001001 }, delay: 11, direction: 0, next_node_id: PublicKey(*snip*), short_channel_id: ShortChannelId(114349209419776) }], probability_ppm: 900044 }]

with auto layers applied. Notice how the second Amount in the path is not Amount { msat: 100000000 } but Amount { msat: 100001001 } instead. So the l2 node does not get paid and errors rightfully with WIRE_FEE_INSUFFICIENT.

[daywalker90]

using cln-rpc from master + #7549

[daywalker90]

looking at the getroutes tests this seems to be expected behaviour?! If that's actually the case then it would be very different from getroute and what sendpay expects as a path structure!

[daywalker90]

Another test with 4 nodes in a line graph:

[GetroutesRoutes { amount_msat: Amount { msat: 100000000 }, 
path: [
GetroutesRoutesPath { amount_msat: Amount { msat: 100002002 }, delay: 17, direction: 1, next_node_id: PublicKey(591da33c1e1cc154001a228933a53d926cc4857c44acf7f77fa459a32036222ddc43a957fdb57d8b5eaf8923daa676fba27e758020a8ecd46ab778cbb695da12), short_channel_id: ShortChannelId(115448721113088) }, 
GetroutesRoutesPath { amount_msat: Amount { msat: 100002002 }, delay: 17, direction: 0, next_node_id: PublicKey(5d885d3a9cb390c0806b76aad553c38bbc6e365d8740e5104e13badf92112b5d6bb8de8f265f6aea7859832ab48862da43eb4c2d8b6ff041a9a688ac25c62fa4), short_channel_id: ShortChannelId(115448721047552) }, 
GetroutesRoutesPath { amount_msat: Amount { msat: 100001001 }, delay: 11, direction: 0, next_node_id: PublicKey(99e19d2dcbc6568acf1f4995cace92994b29235fe3c27746d8e78bf1eb59ce82a7e4f407779fb5c98c36a2f25799f03fedd2479a4e94cf4af97d88dfb7691c54), short_channel_id: ShortChannelId(115448720982016) }],
probability_ppm: 810079 }]

[GetrouteRoute { style: TLV, amount_msat: Amount { msat: 100002002 }, channel: ShortChannelId(115448721113088), delay: 21, direction: 1, id: PublicKey(591da33c1e1cc154001a228933a53d926cc4857c44acf7f77fa459a32036222ddc43a957fdb57d8b5eaf8923daa676fba27e758020a8ecd46ab778cbb695da12) }, 
GetrouteRoute { style: TLV, amount_msat: Amount { msat: 100001001 }, channel: ShortChannelId(115448721047552), delay: 15, direction: 0, id: PublicKey(5d885d3a9cb390c0806b76aad553c38bbc6e365d8740e5104e13badf92112b5d6bb8de8f265f6aea7859832ab48862da43eb4c2d8b6ff041a9a688ac25c62fa4) }, 
GetrouteRoute { style: TLV, amount_msat: Amount { msat: 100000000 }, channel: ShortChannelId(115448720982016), delay: 9, direction: 0, id: PublicKey(99e19d2dcbc6568acf1f4995cace92994b29235fe3c27746d8e78bf1eb59ce82a7e4f407779fb5c98c36a2f25799f03fedd2479a4e94cf4af97d88dfb7691c54) }]

I believe the tests and code are wrong for getroutes. Since the nodes and channel id's match getroute output i believe that the intent was not to change the structure of these paths and therefore the amounts and delays in getroutes are wrong.

• the amounts need to be moved back by 1 element in the path and the last element must be filled with the correct amount_msat
• the delays are wrong and lead to error

[rustyrussell]

OK, so getroutes() is different than getroute(). I should document this properly.

It's optimized towards onion creation, i.e. these are what you would put in the intermediary onions. So, it's the path to the destination, not including the destination. This will work better with injectpayonion (which I have yet to write(. But to be fair, it should also include the final_ctlv value, too.