gossip: send the *other* node's cltv_expiry_delta in channel_announce.

Include tests from example doc.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

channeld/channel.c

@@ -118,7 +118,7 @@ struct peer {
 	u16 channel_direction;
 
 	/* CLTV delta to announce to peers */
-	u16 cltv_delta;
+	u16 their_cltv_delta;
 	u32 fee_base;
 	u32 fee_per_satoshi;
 
@@ -247,7 +247,7 @@ static void send_channel_update(struct peer *peer, bool disabled)
 	cupdate = towire_channel_update(
 	    tmpctx, sig, &peer->chain_hash,
 	    &peer->short_channel_ids[LOCAL], timestamp, flags,
-	    peer->cltv_delta, 1, peer->fee_base, peer->fee_per_satoshi);
+	    peer->their_cltv_delta, 1, peer->fee_base, peer->fee_per_satoshi);
 
 	msg = towire_hsm_cupdate_sig_req(tmpctx, cupdate);
 
@@ -1733,7 +1733,8 @@ static void handle_offer_htlc(struct peer *peer, const u8 *inmsg)
 	e = channel_add_htlc(peer->channel, LOCAL, peer->htlc_id,
 			     amount_msat, cltv_expiry, &payment_hash,
 			     onion_routing_packet);
-	status_trace("Adding HTLC %"PRIu64" gave %i", peer->htlc_id, e);
+	status_trace("Adding HTLC %"PRIu64" msat=%"PRIu64" cltv=%u gave %i",
+		     peer->htlc_id, amount_msat, cltv_expiry, e);
 
 	switch (e) {
 	case CHANNEL_ERR_ADD_OK:
@@ -2022,7 +2023,7 @@ static void init_channel(struct peer *peer)
 				   &peer->node_ids[LOCAL],
 				   &peer->node_ids[REMOTE],
 				   &peer->commit_msec,
-				   &peer->cltv_delta,
+				   &peer->their_cltv_delta,
 				   &peer->last_was_revoke,
 				   &peer->last_sent_commit,
 				   &peer->next_index[LOCAL],

channeld/channel_wire.csv

@@ -29,7 +29,7 @@ channel_init,,seed,struct privkey
 channel_init,,local_node_id,struct pubkey
 channel_init,,remote_node_id,struct pubkey
 channel_init,,commit_msec,u32
-channel_init,,cltv_delta,u16
+channel_init,,their_cltv_delta,u16
 channel_init,,last_was_revoke,bool
 channel_init,,num_last_sent_commit,u16
 channel_init,,last_sent_commit,num_last_sent_commit*struct changed_htlc

lightningd/peer_control.c

@@ -2198,7 +2198,7 @@ static bool peer_start_channeld(struct peer *peer,
 				      &peer->ld->id,
 				      &peer->id,
 				      time_to_msec(cfg->commit_time),
-				      cfg->min_htlc_expiry,
+				      peer->channel_info->their_cltv_expiry_delta,
 				      peer->last_was_revoke,
 				      peer->last_sent_commit,
 				      peer->next_index[LOCAL],

lightningd/peer_htlcs.c

@@ -386,6 +386,8 @@ static void handle_localpay(struct htlc_in *hin,
 
 	log_info(ld->log, "Resolving invoice '%s' with HTLC %"PRIu64,
 		 invoice->label, hin->key.id);
+	log_debug(ld->log, "%s: Actual amount %"PRIu64"msat, HTLC expiry %u",
+		  invoice->label, hin->msatoshi, cltv_expiry);
 	fulfill_htlc(hin, &invoice->r);
 	resolve_invoice(ld, invoice);
 	return;

tests/test_lightningd.py

@@ -1137,6 +1137,131 @@ class LightningDTests(BaseLightningDTests):
         route = copy.deepcopy(baseroute)
         l1.rpc.sendpay(to_json(route), rhash)
 
+    def test_forward_different_fees_and_cltv(self):
+        # FIXME: Check BOLT quotes here too
+        # BOLT #7:
+        # ```
+        #    B
+        #   / \
+        #  /   \
+        # A     C 
+        #  \   /
+        #   \ /
+        #    D
+        # ```
+        # 
+        # Each node asks for the following `cltv_expiry_delta` on every channel open:
+        # 
+        # 1. A: 10 blocks
+        # 2. B: 20 blocks
+        # 3. C: 30 blocks
+        # 4. D: 40 blocks
+        # 
+        # Also, each node has the same fee scheme which it uses for each of its
+        # channels:
+        # 
+        # 1. A: 100 base + 1000 millionths
+        # 1. B: 200 base + 2000 millionths
+        # 1. C: 300 base + 3000 millionths
+        # 1. D: 400 base + 4000 millionths
+
+        # We don't do D yet.
+        l1 = self.node_factory.get_node(options=['--min-htlc-expiry=10', '--fee-base=100', '--fee-per-satoshi=1000'])
+        l2 = self.node_factory.get_node(options=['--min-htlc-expiry=20', '--fee-base=200', '--fee-per-satoshi=2000'])
+        l3 = self.node_factory.get_node(options=['--min-htlc-expiry=30', '--fee-base=300', '--fee-per-satoshi=3000'])
+
+        ret = l1.rpc.connect('localhost', l2.info['port'], l2.info['id'])
+        assert ret['id'] == l2.info['id']
+
+        l1.daemon.wait_for_log('WIRE_GOSSIPCTL_NEW_PEER')
+        l2.daemon.wait_for_log('WIRE_GOSSIPCTL_NEW_PEER')
+
+        ret = l2.rpc.connect('localhost', l3.info['port'], l3.info['id'])
+        assert ret['id'] == l3.info['id']
+
+        l2.daemon.wait_for_log('WIRE_GOSSIPCTL_NEW_PEER')
+        l3.daemon.wait_for_log('WIRE_GOSSIPCTL_NEW_PEER')
+        
+        self.fund_channel(l1, l2, 10**6)
+        c1='{}:2:1'.format(bitcoind.rpc.getblockcount())
+        self.fund_channel(l2, l3, 10**6)
+        c2='{}:2:1'.format(bitcoind.rpc.getblockcount())
+
+        # Allow announce messages.
+        l1.bitcoin.rpc.generate(5)
+
+        # Make sure l1 has seen announce for all channels.
+        l1.daemon.wait_for_logs([
+            'Received channel_update for channel {}\\(0\\)'.format(c1),
+            'Received channel_update for channel {}\\(1\\)'.format(c1),
+            'Received channel_update for channel {}\\(0\\)'.format(c2),
+            'Received channel_update for channel {}\\(1\\)'.format(c2)])
+
+        # BOLT #7:
+        # 
+        # If B were to send 4,999,999 millisatoshi to C, it wouldn't charge
+        # itself a fee, but it would need to consider the `cltv_expiry_delta` in
+        # the B->C `channel_update` (ie. the `cltv_expiry_delta` C told B in
+        # `open_channel` or `accept_channel`).  We also assume it adds a "shadow
+        # route" to give an extra CLTV of 42.
+
+        # FIXME: Add shadow route
+        shadow_route=0
+        route = l2.rpc.getroute(l3.info['id'], 4999999, 1)["route"]
+        assert len(route) == 1
+
+        # BOLT #7:
+        #
+        #    * `amount_msat`: 4999999
+        #    * `cltv_expiry`: current-block-height + 30 + 42
+        #    * `onion_routing_packet`:
+        # 	 * `amt_to_forward` = 4999999
+        #      * `outgoing_cltv_value` = current-block-height + 30 + 42
+        assert route[0]['msatoshi'] == 4999999
+        assert route[0]['delay'] == 30 + shadow_route
+
+        # BOLT #7:
+        # If A were to send an 4,999,999 millisatoshi to C via B, it needs to
+        # pay B the fee it specified in the B->C `channel_update`, calculated as
+        # per [HTLC Fees](#htlc_fees):
+        # 
+	# 200 + 4999999 * 2000 / 1000000 = 10199
+        # 
+        # Assume a "shadow route" CLTV of 42 again, it would set `cltv_expiry`
+        # to the current-block-height plus the `channel_update` amounts A->B
+        # (20) and B->C (30), plus 42:
+        # 
+        # Thus the `update_add_htlc` message from A to B would be:
+	# 
+        # * `amount_msat`: 5010198
+        # * `cltv_expiry`: current-block-height + 50 + 42
+        # * `onion_routing_packet`:
+	# * `amt_to_forward` = 4999999
+        # * `outgoing_cltv_value` = current-block-height + 30 + 42
+        route = l1.rpc.getroute(l3.info['id'], 4999999, 1)["route"]
+        assert len(route) == 2
+
+        assert route[0]['msatoshi'] == 5010198
+        assert route[0]['delay'] == 50 + shadow_route
+        assert route[1]['msatoshi'] == 4999999
+        assert route[1]['delay'] == 30 + shadow_route
+
+        rhash = l3.rpc.invoice(4999999, 'test_forward_different_fees_and_cltv')['rhash']
+        assert l3.rpc.listinvoice('test_forward_different_fees_and_cltv')[0]['complete'] == False
+
+        # This should work.
+        l1.rpc.sendpay(to_json(route), rhash)
+
+        # We add one to the blockcount for a bit of fuzz (FIXME: Shadowroute would fix this!)
+        shadow_route = 1
+        l1.daemon.wait_for_log("Adding HTLC 0 msat=5010198 cltv={} gave 0"
+                               .format(bitcoind.rpc.getblockcount() + 50 + shadow_route))
+        l2.daemon.wait_for_log("Adding HTLC 0 msat=4999999 cltv={} gave 0"
+                               .format(bitcoind.rpc.getblockcount() + 30 + shadow_route))
+        l3.daemon.wait_for_log("test_forward_different_fees_and_cltv: Actual amount 4999999msat, HTLC expiry {}"
+                               .format(bitcoind.rpc.getblockcount() + 30 + shadow_route))
+        assert l3.rpc.listinvoice('test_forward_different_fees_and_cltv')[0]['complete'] == True
+
     def test_disconnect(self):
         # These should all make us fail.
         disconnects = ['-WIRE_INIT',

wallet/db.c

@@ -64,6 +64,7 @@ char *dbmigrations[] = {
     "  per_commit_remote BLOB,"
     "  old_per_commit_remote BLOB,"
     "  feerate_per_kw INTEGER,"
+    "  their_cltv_expiry_delta INTEGER,"
     /* END channel_info */
     "  shachain_remote_id INTEGER,"
     "  shutdown_scriptpubkey_remote BLOB,"

wallet/wallet.c

@@ -506,10 +506,11 @@ static bool wallet_stmt2channel(struct wallet *w, sqlite3_stmt *stmt,
 		ok &= sqlite3_column_pubkey(stmt, col++, &channel_info->remote_per_commit);
 		ok &= sqlite3_column_pubkey(stmt, col++, &channel_info->old_remote_per_commit);
 		channel_info->feerate_per_kw = sqlite3_column_int64(stmt, col++);
+		channel_info->their_cltv_expiry_delta = sqlite3_column_int64(stmt, col++);
 		wallet_channel_config_load(w, remote_config_id, &chan->peer->channel_info->their_config);
 	} else {
 		/* No channel_info, skip positions in the result */
-		col += 7;
+		col += 8;
 	}
 
 	/* Load shachain */
@@ -549,7 +550,7 @@ static bool wallet_stmt2channel(struct wallet *w, sqlite3_stmt *stmt,
 		col += 2;
 	}
 
-	assert(col == 33);
+	assert(col == 34);
 
 	chan->peer->channel = chan;
 
@@ -568,7 +569,7 @@ const char *channel_fields =
     "fundingkey_remote, revocation_basepoint_remote, "
     "payment_basepoint_remote, "
     "delayed_payment_basepoint_remote, per_commit_remote, "
-    "old_per_commit_remote, feerate_per_kw, shachain_remote_id, "
+    "old_per_commit_remote, feerate_per_kw, their_cltv_expiry_delta, shachain_remote_id, "
     "shutdown_scriptpubkey_remote, shutdown_keyidx_local, "
     "last_sent_commit_state, last_sent_commit_id, "
     "last_tx, last_sig";
@@ -778,6 +779,7 @@ bool wallet_channel_save(struct wallet *w, struct wallet_channel *chan){
 			      "  per_commit_remote='%s',"
 			      "  old_per_commit_remote='%s',"
 			      "  feerate_per_kw=%d,"
+			      "  their_cltv_expiry_delta=%d,"
 			      "  channel_config_remote=%"PRIu64
 			      " WHERE id=%"PRIu64,
 			      db_serialize_pubkey(tmpctx, &p->channel_info->remote_fundingkey),
@@ -787,6 +789,7 @@ bool wallet_channel_save(struct wallet *w, struct wallet_channel *chan){
 			      db_serialize_pubkey(tmpctx, &p->channel_info->remote_per_commit),
 			      db_serialize_pubkey(tmpctx, &p->channel_info->old_remote_per_commit),
 			      p->channel_info->feerate_per_kw,
+			      p->channel_info->their_cltv_expiry_delta,
 			      p->channel_info->their_config.id,
 			      chan->id);
 	}