common: remove legacy onion translation.

This was added in 24.05, but LND since 0.18.3 no longer ever creates
such onions, and even that version (September 2024) is now a long way
behind.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Changelog-Removed: Protocol: we no longer support legacy onions (never sent by LND >= 0.18.3, which was the last)

Author: rustyrussell

common/sphinx.c

@@ -677,54 +677,13 @@ struct route_step *process_onionpacket(
 	/* Any of these could fail, falling thru with cursor == NULL */
 	payload_size = fromwire_bigsize(&cursor, &max);
 
-	/* Legacy!  0 length payload means fixed 32 byte structure */
-	if (payload_size == 0 && max >= 32) {
-		struct tlv_payload *legacy = tlv_payload_new(tmpctx);
-		const u8 *legacy_cursor = cursor;
-		size_t legacy_max = 32;
-		u8 *onwire_tlv;
-
-		legacy->amt_to_forward = tal(legacy, u64);
-		legacy->outgoing_cltv_value = tal(legacy, u32);
-		legacy->short_channel_id = tal(legacy, struct short_channel_id);
-
-		/* BOLT-obsolete #4:
-		 * ## Legacy `hop_data` payload format
-		 *
-		 * The `hop_data` format is identified by a single `0x00`-byte
-		 * length, for backward compatibility.  Its payload is defined
-		 * as:
-		 *
-		 * 1. type: `hop_data` (for `realm` 0)
-		 * 2. data:
-		 *    * [`short_channel_id`:`short_channel_id`]
-		 *    * [`u64`:`amt_to_forward`]
-		 *    * [`u32`:`outgoing_cltv_value`]
-		 *    * [`12*byte`:`padding`]
-		 */
-		*legacy->short_channel_id = fromwire_short_channel_id(&legacy_cursor, &legacy_max);
-		*legacy->amt_to_forward = fromwire_u64(&legacy_cursor, &legacy_max);
-		*legacy->outgoing_cltv_value = fromwire_u32(&legacy_cursor, &legacy_max);
-
-		/* Re-linearize it as a modern TLV! */
-		onwire_tlv = tal_arr(tmpctx, u8, 0);
-		towire_tlv_payload(&onwire_tlv, legacy);
-
-		/* Length, then tlv */
-		step->raw_payload = tal_arr(step, u8, 0);
-		towire_bigsize(&step->raw_payload, tal_bytelen(onwire_tlv));
-		towire_u8_array(&step->raw_payload, onwire_tlv, tal_bytelen(onwire_tlv));
+	/* FIXME: raw_payload *includes* the length, which is redundant and
+	 * means we can't just ust fromwire_tal_arrn. */
+	fromwire_pad(&cursor, &max, payload_size);
+	if (cursor != NULL)
+		step->raw_payload = tal_dup_arr(step, u8, paddedheader,
+						cursor - paddedheader, 0);
 
-		payload_size = 32;
-		fromwire_pad(&cursor, &max, payload_size);
-	} else {
-		/* FIXME: raw_payload *includes* the length, which is redundant and
-		 * means we can't just ust fromwire_tal_arrn. */
-		fromwire_pad(&cursor, &max, payload_size);
-		if (cursor != NULL)
-			step->raw_payload = tal_dup_arr(step, u8, paddedheader,
-							cursor - paddedheader, 0);
-	}
 	fromwire_hmac(&cursor, &max, &step->next->hmac);
 
 	/* BOLT #4:

tests/test_pay.py

@@ -5912,34 +5912,6 @@ def test_offer_paths(node_factory, bitcoind):
         l5.rpc.fetchinvoice(offer=offer['bolt12'])
 
 
-def test_pay_legacy_forward(node_factory, bitcoind, executor):
-    """We removed legacy in 22.11, and LND will still send them for
-    route hints!  See
-    https://github.com/lightningnetwork/lnd/issues/8785
-
-    """
-    l1, l2, l3 = node_factory.line_graph(3, fundamount=10**6, wait_for_announce=True)
-
-    inv = l3.rpc.invoice(1000, "inv", "inv")
-
-    chanid12 = only_one(l1.rpc.listpeerchannels(l2.info['id'])['channels'])['short_channel_id']
-    chanid23 = only_one(l2.rpc.listpeerchannels(l3.info['id'])['channels'])['short_channel_id']
-    route = [{'amount_msat': 1011,
-              'id': l2.info['id'],
-              'delay': 20,
-              'channel': chanid12},
-             {'amount_msat': 1000,
-              'id': l3.info['id'],
-              'delay': 10,
-              'channel': chanid23}]
-
-    l1.rpc.call("sendpay", payload={'route': route,
-                                    'payment_hash': inv['payment_hash'],
-                                    'payment_secret': inv['payment_secret'],
-                                    'dev_legacy_hop': True})
-    l1.rpc.waitsendpay(inv['payment_hash'])
-
-
 # CI is so slow under valgrind that this does not reach the ratelimit!
 @pytest.mark.slow_test
 def test_onionmessage_ratelimit(node_factory, executor):