sphinx: separate nonfinal from final interface, add tlv option.

For legacy, they were the same, but for TLV we care whether it's the
final hop or not.

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

common/sphinx.c

@@ -149,6 +149,80 @@ void sphinx_add_v0_hop(struct sphinx_path *path, const struct pubkey *pubkey,
 	sphinx_add_raw_hop(path, pubkey, 0, buf);
 }
 
+static void sphinx_add_tlv_hop(struct sphinx_path *path,
+			       const struct pubkey *pubkey,
+			       const struct tlv_tlv_payload *tlv)
+{
+	u8 *tlvs = tal_arr(path, u8, 0);
+	towire_tlvs(&tlvs, tlvs_tlv_payload, TLVS_TLV_PAYLOAD_ARRAY_SIZE, tlv);
+	sphinx_add_raw_hop(path, pubkey, tal_bytelen(tlvs), tlvs);
+}
+
+void sphinx_add_nonfinal_hop(struct sphinx_path *path,
+			     const struct pubkey *pubkey,
+			     bool use_tlv,
+			     const struct short_channel_id *scid,
+			     struct amount_msat forward,
+			     u32 outgoing_cltv)
+{
+	if (use_tlv) {
+		struct tlv_tlv_payload *tlv = tlv_tlv_payload_new(tmpctx);
+		struct tlv_tlv_payload_amt_to_forward tlv_amt;
+		struct tlv_tlv_payload_outgoing_cltv_value tlv_cltv;
+		struct tlv_tlv_payload_short_channel_id tlv_scid;
+
+		/* BOLT #4:
+		 *
+		 * The writer:
+		 *  - MUST include `amt_to_forward` and `outgoing_cltv_value`
+		 *    for every node.
+		 *  - MUST include `short_channel_id` for every non-final node.
+		 */
+		tlv_amt.amt_to_forward = forward.millisatoshis; /* Raw: TLV convert */
+		tlv_cltv.outgoing_cltv_value = outgoing_cltv;
+		tlv_scid.short_channel_id = *scid;
+		tlv->amt_to_forward = &tlv_amt;
+		tlv->outgoing_cltv_value = &tlv_cltv;
+		tlv->short_channel_id = &tlv_scid;
+
+		sphinx_add_tlv_hop(path, pubkey, tlv);
+	} else {
+		sphinx_add_v0_hop(path, pubkey, scid, forward, outgoing_cltv);
+	}
+}
+
+void sphinx_add_final_hop(struct sphinx_path *path,
+			  const struct pubkey *pubkey,
+			  bool use_tlv,
+			  struct amount_msat forward,
+			  u32 outgoing_cltv)
+{
+	if (use_tlv) {
+		struct tlv_tlv_payload *tlv = tlv_tlv_payload_new(tmpctx);
+		struct tlv_tlv_payload_amt_to_forward tlv_amt;
+		struct tlv_tlv_payload_outgoing_cltv_value tlv_cltv;
+
+		/* BOLT #4:
+		 *
+		 * The writer:
+		 *  - MUST include `amt_to_forward` and `outgoing_cltv_value`
+		 *    for every node.
+		 *...
+		 *  - MUST NOT include `short_channel_id` for the final node.
+		 */
+		tlv_amt.amt_to_forward = forward.millisatoshis; /* Raw: TLV convert */
+		tlv_cltv.outgoing_cltv_value = outgoing_cltv;
+		tlv->amt_to_forward = &tlv_amt;
+		tlv->outgoing_cltv_value = &tlv_cltv;
+
+		sphinx_add_tlv_hop(path, pubkey, tlv);
+	} else {
+		static struct short_channel_id all_zero_scid;
+		sphinx_add_v0_hop(path, pubkey, &all_zero_scid,
+				  forward, outgoing_cltv);
+	}
+}
+
 /* Small helper to append data to a buffer and update the position
  * into the buffer
  */

common/sphinx.h

@@ -231,6 +231,25 @@ void sphinx_add_v0_hop(struct sphinx_path *path, const struct pubkey *pubkey,
 void sphinx_add_raw_hop(struct sphinx_path *path, const struct pubkey *pubkey,
 			enum sphinx_payload_type type, const u8 *payload);
 
+/**
+ * Add a non-final hop to the path.
+ */
+void sphinx_add_nonfinal_hop(struct sphinx_path *path,
+			     const struct pubkey *pubkey,
+			     bool use_tlv,
+			     const struct short_channel_id *scid,
+			     struct amount_msat forward,
+			     u32 outgoing_cltv);
+
+/**
+ * Add a final hop to the path.
+ */
+void sphinx_add_final_hop(struct sphinx_path *path,
+			  const struct pubkey *pubkey,
+			  bool use_tlv,
+			  struct amount_msat forward,
+			  u32 outgoing_cltv);
+
 /**
  * Helper to extract fields from ONION_END.
  */

common/test/run-sphinx.c

@@ -99,6 +99,12 @@ void towire_sha256(u8 **pptr UNNEEDED, const struct sha256 *sha256 UNNEEDED)
 void towire_short_channel_id(u8 **pptr UNNEEDED,
 			     const struct short_channel_id *short_channel_id UNNEEDED)
 { fprintf(stderr, "towire_short_channel_id called!\n"); abort(); }
+/* Generated stub for towire_tlvs */
+void towire_tlvs(u8 **pptr UNNEEDED,
+		 const struct tlv_record_type types[] UNNEEDED,
+		 size_t num_types UNNEEDED,
+		 const void *record UNNEEDED)
+{ fprintf(stderr, "towire_tlvs called!\n"); abort(); }
 /* Generated stub for towire_tu32 */
 void towire_tu32(u8 **pptr UNNEEDED, u32 v UNNEEDED)
 { fprintf(stderr, "towire_tu32 called!\n"); abort(); }

lightningd/pay.c

@@ -615,6 +615,20 @@ static struct command_result *wait_payment(struct lightningd *ld,
 	abort();
 }
 
+static bool should_use_tlv(enum route_hop_style style)
+{
+	switch (style) {
+	case ROUTE_HOP_TLV:
+#if EXPERIMENTAL_FEATURES
+		return true;
+#endif
+		/* Otherwise fall thru */
+	case ROUTE_HOP_LEGACY:
+		return false;
+	}
+	abort();
+}
+
 /* Returns command_result if cmd was resolved, NULL if not yet called. */
 static struct command_result *
 send_payment(struct lightningd *ld,
@@ -639,13 +653,11 @@ send_payment(struct lightningd *ld,
 	struct routing_failure *fail;
 	struct channel *channel;
 	struct sphinx_path *path;
-	struct short_channel_id finalscid;
 	struct pubkey pubkey;
 	bool ret;
 
 	/* Expiry for HTLCs is absolute.  And add one to give some margin. */
 	base_expiry = get_block_height(ld->topology) + 1;
-	memset(&finalscid, 0, sizeof(struct short_channel_id));
 
 	path = sphinx_path_new(tmpctx, rhash->u.u8);
 	/* Extract IDs for each hop: create_onionpacket wants array. */
@@ -656,19 +668,23 @@ send_payment(struct lightningd *ld,
 	for (i = 0; i < n_hops - 1; i++) {
 		ret = pubkey_from_node_id(&pubkey, &ids[i]);
 		assert(ret);
-		sphinx_add_v0_hop(path, &pubkey, &route[i + 1].channel_id,
-				  route[i + 1].amount,
-				  base_expiry + route[i + 1].delay);
+
+		sphinx_add_nonfinal_hop(path, &pubkey,
+					should_use_tlv(route[i].style),
+					&route[i + 1].channel_id,
+					route[i + 1].amount,
+					base_expiry + route[i + 1].delay);
 	}
 
 	/* And finally set the final hop to the special values in
 	 * BOLT04 */
-	memset(&finalscid, 0, sizeof(struct short_channel_id));
 	ret = pubkey_from_node_id(&pubkey, &ids[i]);
 	assert(ret);
-	sphinx_add_v0_hop(path, &pubkey, &finalscid,
-			  route[i].amount,
-			  base_expiry + route[i].delay);
+
+	sphinx_add_final_hop(path, &pubkey,
+			     should_use_tlv(route[i].style),
+			     route[i].amount,
+			     base_expiry + route[i].delay);
 
 	/* Now, do we already have a payment? */
 	payment = wallet_payment_by_hash(tmpctx, ld->wallet, rhash);