pytest: Add a test for keysend

It currently uses a borrowed sending implementation from the noise plugin, but
we'll implement that functionality in the native keysend plugin next.

tests/plugins/keysend.py

@@ -0,0 +1,118 @@
+#!/usr/bin/env python3
+"""Temporary keysend plugin until we implement it in C
+
+This plugin is just used to test the ability to receive keysend payments until
+we implement it in `plugins/keysend.c`. Most of this code is borrowed from the
+noise plugin.
+
+"""
+
+from pyln.client import Plugin, RpcError
+from pyln.proto.onion import TlvPayload, Tu32Field, Tu64Field
+from binascii import hexlify
+import os
+import hashlib
+import struct
+
+
+plugin = Plugin()
+TLV_KEYSEND_PREIMAGE = 5482373484
+
+
+def serialize_payload(n, blockheight):
+    """Serialize a legacy payload.
+    """
+    block, tx, out = n['channel'].split('x')
+    payload = hexlify(struct.pack(
+        "!cQQL", b'\x00',
+        int(block) << 40 | int(tx) << 16 | int(out),
+        int(n['amount_msat']),
+        blockheight + n['delay'])).decode('ASCII')
+    payload += "00" * 12
+    return payload
+
+
+def buildpath(plugin, node_id, payload, amt, exclusions):
+    blockheight = plugin.rpc.getinfo()['blockheight']
+    route = plugin.rpc.getroute(node_id, amt, 10, exclude=exclusions)['route']
+    first_hop = route[0]
+    # Need to shift the parameters by one hop
+    hops = []
+    for h, n in zip(route[:-1], route[1:]):
+        # We tell the node h about the parameters to use for n (a.k.a. h + 1)
+        hops.append({
+            "type": "legacy",
+            "pubkey": h['id'],
+            "payload": serialize_payload(n, blockheight)
+        })
+
+    pl = TlvPayload()
+    pl.fields.append(Tu64Field(2, amt))
+    pl.fields.append(Tu32Field(4, route[-1]['delay']))
+
+    for f in payload.fields:
+        pl.add_field(f.typenum, f.value)
+
+    # The last hop has a special payload:
+    hops.append({
+        "type": "tlv",
+        "pubkey": route[-1]['id'],
+        "payload": hexlify(pl.to_bytes()).decode('ASCII'),
+    })
+    print(f"Keysend payload {hexlify(pl.to_bytes())}")
+    return first_hop, hops, route
+
+
+def deliver(node_id, payload, amt, payment_hash, max_attempts=5):
+    """Do your best to deliver `payload` to `node_id`.
+    """
+    exclusions = []
+    payment_hash = hexlify(payment_hash).decode('ASCII')
+
+    for attempt in range(max_attempts):
+        plugin.log("Starting attempt {} to deliver message to {}".format(attempt, node_id))
+
+        first_hop, hops, route = buildpath(plugin, node_id, payload, amt, exclusions)
+        onion = plugin.rpc.createonion(hops=hops, assocdata=payment_hash)
+
+        plugin.rpc.sendonion(
+            onion=onion['onion'],
+            first_hop=first_hop,
+            payment_hash=payment_hash,
+            shared_secrets=onion['shared_secrets'],
+        )
+        try:
+            plugin.rpc.waitsendpay(payment_hash=payment_hash)
+            return {'route': route, 'payment_hash': payment_hash, 'attempt': attempt}
+        except RpcError as e:
+            failcode = e.error['data']['failcode']
+            failingidx = e.error['data']['erring_index']
+            if failcode == 16399 or failingidx == len(hops):
+                return {
+                    'route': route,
+                    'payment_hash': payment_hash,
+                    'attempt': attempt + 1
+                }
+
+            plugin.log("Retrying delivery.")
+
+            # TODO Store the failing channel in the exclusions
+    raise ValueError('Could not reach destination {node_id}'.format(node_id=node_id))
+
+
+@plugin.method('keysend')
+def keysend(node_id, amount, plugin):
+    payload = TlvPayload()
+    payment_key = os.urandom(32)
+    payment_hash = hashlib.sha256(payment_key).digest()
+    payload.add_field(TLV_KEYSEND_PREIMAGE, payment_key)
+    res = deliver(
+        node_id,
+        payload,
+        amt=amount,
+        payment_hash=payment_hash
+    )
+    return res
+
+
+plugin.run()

tests/test_pay.py

@@ -2959,3 +2959,28 @@ def test_excluded_adjacent_routehint(node_factory, bitcoind):
     # This will make it reject the routehint.
     with pytest.raises(RpcError, match=r'Route wanted fee of 1msat'):
         l1.rpc.pay(bolt11=inv['bolt11'], maxfeepercent=0, exemptfee=0)
+
+
+def test_keysend(node_factory):
+    # Use a temporary python plugin until we implement a native one
+    plugin_path = os.path.join(os.getcwd(), 'tests/plugins/keysend.py')
+    opts = {'plugin': plugin_path}
+    amt = 10000
+    l1, l2, l3 = node_factory.line_graph(3, opts=opts, wait_for_announce=True)
+
+    # Send an indirect one from l1 to l3
+    l1.rpc.keysend(l3.info['id'], amt)
+    invs = l3.rpc.listinvoices()['invoices']
+    assert(len(invs) == 1)
+
+    inv = invs[0]
+    print(inv)
+    assert(inv['msatoshi_received'] >= amt)
+
+    # Now send a direct one instead from l1 to l2
+    l1.rpc.keysend(l2.info['id'], amt)
+    invs = l2.rpc.listinvoices()['invoices']
+    assert(len(invs) == 1)
+
+    inv = invs[0]
+    assert(inv['msatoshi_received'] >= amt)