Raspiblitz: Keysend -- spontanous payments

[openoms]

See: https://twitter.com/joostjgr/status/1220294554307497986

Tested successfully on a node with lnd v0.9.0-beta by editing the lnd.service file:

sudo nano /etc/systemd/system/lnd.service

add --accept-keysend:

ExecStart=/usr/local/bin/lnd --accept-keysend --tor.active --tor.streamisolation --tor.v3 --listen=127.0.0.1:9735

restart:
sudo systemctl restart lnd
lncli unlock

Send payments to it with the syntax:
lncli sendpayment --keysend -d 028a2cb8d51e44d7d7e108c2e80a98cc069145e05a6d2025cf554bd8866fe32993 -a 1 --data 7629168=$(echo -n "sent from a RaspiBlitz" | xxd -pu -c 10000)

Output with a direct channel:

$ lncli sendpayment --keysend -d 028a2cb8d51e44d7d7e108c2e80a98cc069145e05a6d2025cf554bd8866fe32993 -a 1 --data 7629168=$(echo -n "test" | xxd -pu -c 10000)
{
    "payment_error": "",
    "payment_preimage": "8228248114408ad4ad05147ce66b337efa38e54d0eea543e048c06d24f017841",
    "payment_route": {
        "total_time_lock": 614511,
        "total_fees": "0",
        "total_amt": "1",
        "hops": [
            {
                "chan_id": "675528949131837440",
                "chan_capacity": "1999846",
                "amt_to_forward": "1",
                "fee": "0",
                "expiry": 614511,
                "amt_to_forward_msat": "1000",
                "fee_msat": "0",
                "pub_key": "028a2cb8d51e44d7d7e108c2e80a98cc069145e05a6d2025cf554bd8866fe32993",
                "tlv_payload": true,
                "mpp_record": null,
                "custom_records": {
                    "7629168": "74657374",
                    "5482373484": "8228248114408ad4ad05147ce66b337efa38e54d0eea543e048c06d24f017841"
                }
            }
        ],
        "total_fees_msat": "0",
        "total_amt_msat": "1000"
    },
    "payment_hash": "9ec90832d05af2d1488ff06067297509316bf22e6714cf8eff92e35b2bb0865b"
}

Shall we enable this by default? Not sure of any drawbacks.

[ascisco]

I can receive direct keysend payments but im getting the following error when trying to send them:

lncli sendpayment --keysend -d 034d2dfd138b4dff2e8f29fef8b70b91ae87b384eb8b8294a54ed2e58f11f2109d -a 1 --data 7629168=$(echo -n "sent from a RaspiBlitz" | xxd -pu -c 10000)
{
    "payment_error": "IncorrectOrUnknownPaymentDetails(amt=1000 mSAT, height=614574)@1",
    "payment_preimage": null,
    "payment_route": null,
    "payment_hash": "620edc7dc6d4ffaf50ce650f0318c1c77766941b82a1e7beca9b323b2a0a0e23"
}
[lncli] IncorrectOrUnknownPaymentDetails(amt=1000 mSAT, height=614574)@1

[openoms]

I can receive direct keysend payments but im getting the following error when trying to send them:

Everything needs to be fulfilled what is needed for a successful LN payment + the receiver needs to be paid through a public channel as keysend has no routehints available (which are provided by nodes behind private channels in the invoice, for example mobile wallets)

• Try paying an invoice to that node. Does that succeed?
• Try keysend through a direct channel.

[ascisco]

I can receive direct keysend payments but im getting the following error when trying to send them:

Everything needs to be fulfilled what is needed for a successful LN payment + the receiver needs to be paid through a public channel as keysend has no routehints available (which are provided by nodes behind private channels in the invoice, for example mobile wallets)

• Try paying an invoice to that node. Does that succeed?
• Try keysend through a direct channel.

I have a direct channel opened already with the person im trying to send to. I was able to do a keysend with others who I do not have a channel open with though.

[fusion44]

I think this error occurs usually when the receiving peer doesn't run LND with --accept-keysend.

[rootzoll]

We should add on option to activate keysend in the next 1.5 release.

[rootzoll]

OK added for v1.5 RC1 release. Needs still testing.

[rootzoll]

I actived keysend on both my testing RaspiBlitzes (both lnd 0.9.2) but when I try to send with

lncli sendpayment -d 0244f87803308d569992458ce9d755a10f0609a6febbd81c01490722f4409ee6fa -a 10 --keysend

I just get an error "destination hop doesn't understand new TLV payloads" - @openoms how can I check that keysend is really activated on the other node?

[openoms]

@rootzoll the only way I know to query about the supported features is:
lncli getnodeinfo 0244f87803308d569992458ce9d755a10f0609a6febbd81c01490722f4409ee6fa

Unfortunately that does not return much for that node, neither can I see it's IP address.

I don't see the keysend specific feature for my nodes, but they advertise the same to the network what is given on lncli getinfo.

[openoms]

Joost here suggest just to try and see if it works for now: https://github.com/lightningnetwork/lnd/pull/3795#discussion_r356420971

[rootzoll]

Marked for Hackathon sprint:

• Test sendkey with RaspiBlitz
• Write a sendkey script, that tests all other nodes if supporting sendkey and donates all of them 10 sats
• Connect RaspiBlitz with "SenMany" App - see
  https://github.com/fusion44/sendmany

@fusion44 can you mentor this sprint issue over the Lightning Hackday (first April Weekend)

[fusion44]

@rootzoll Sure, I'd gladly help out on that. Is there a Slack channel or similar for it?

One more reason to fix my RaspiBlitz now :)

[rootzoll]

We have a MatterMost (OpenSource Slack) we will use. Will post more details the next days.

[rootzoll]

Outcome of Hacksprint:

• Made a keysend chat over a RaspiBlitz with keysend activated (3 hops on LN)
• Add SendMany App to the RaspiBlitz for install

Looks good - closing issue for v1.5 release :)