onion: Pass the position and type of the failing TLV type out

We'll need this when returning an error to the sender.

common/onion.c

@@ -205,7 +205,9 @@ size_t onion_payload_length(const u8 *raw_payload, size_t len,
 }
 
 struct onion_payload *onion_decode(const tal_t *ctx,
-				    const struct route_step *rs)
+				   const struct route_step *rs,
+				   u64 *failtlvtype,
+				   size_t *failtlvpos)
 {
 	struct onion_payload *p = tal(ctx, struct onion_payload);
 	const u8 *cursor = rs->raw_payload;
@@ -245,9 +247,10 @@ struct onion_payload *onion_decode(const tal_t *ctx,
 		if (!fromwire_tlv_payload(&cursor, &max, tlv))
 			goto fail;
 
-		if (!tlv_payload_is_valid(tlv, failtlvpos))
+		if (!tlv_payload_is_valid(tlv, failtlvpos)) {
+			*failtlvtype = tlv->fields[*failtlvpos].numtype;
 			goto fail;
-
+		}
 
 		/* BOLT #4:
 		 *

common/onion.h

@@ -59,6 +59,8 @@ size_t onion_payload_length(const u8 *raw_payload, size_t len,
  * If the payload is not valid, returns NULL.
  */
 struct onion_payload *onion_decode(const tal_t *ctx,
-				   const struct route_step *rs);
+				   const struct route_step *rs,
+				   u64 *failtlvtype,
+				   size_t *failtlvpos);
 
 #endif /* LIGHTNING_COMMON_ONION_H */

lightningd/peer_htlcs.c

@@ -780,6 +780,8 @@ struct htlc_accepted_hook_payload {
 	struct channel *channel;
 	struct lightningd *ld;
 	u8 *next_onion;
+	u64 failtlvtype;
+	size_t failtlvpos;
 };
 
 /* The possible return value types that a plugin may return for the
@@ -1116,7 +1118,9 @@ static bool peer_accepted_htlc(const tal_t *ctx,
 	hook_payload = tal(hin, struct htlc_accepted_hook_payload);
 
 	hook_payload->route_step = tal_steal(hook_payload, rs);
-	hook_payload->payload = onion_decode(hook_payload, rs);
+	hook_payload->payload = onion_decode(hook_payload, rs,
+					     &hook_payload->failtlvtype,
+					     &hook_payload->failtlvpos);
 	hook_payload->ld = ld;
 	hook_payload->hin = hin;
 	hook_payload->channel = channel;

wallet/test/run-wallet.c

@@ -411,7 +411,9 @@ enum watch_result onchaind_funding_spent(struct channel *channel UNNEEDED,
 { fprintf(stderr, "onchaind_funding_spent called!\n"); abort(); }
 /* Generated stub for onion_decode */
 struct onion_payload *onion_decode(const tal_t *ctx UNNEEDED,
-				   const struct route_step *rs UNNEEDED)
+				   const struct route_step *rs UNNEEDED,
+				   u64 *failtlvtype UNNEEDED,
+				   size_t *failtlvpos UNNEEDED)
 { fprintf(stderr, "onion_decode called!\n"); abort(); }
 /* Generated stub for onion_type_name */
 const char *onion_type_name(int e UNNEEDED)
@@ -654,6 +656,9 @@ u8 *towire_incorrect_cltv_expiry(const tal_t *ctx UNNEEDED, u32 cltv_expiry UNNE
 /* Generated stub for towire_incorrect_or_unknown_payment_details */
 u8 *towire_incorrect_or_unknown_payment_details(const tal_t *ctx UNNEEDED, struct amount_msat htlc_msat UNNEEDED, u32 height UNNEEDED)
 { fprintf(stderr, "towire_incorrect_or_unknown_payment_details called!\n"); abort(); }
+/* Generated stub for towire_invalid_onion_payload */
+u8 *towire_invalid_onion_payload(const tal_t *ctx UNNEEDED, varint type UNNEEDED, u16 offset UNNEEDED)
+{ fprintf(stderr, "towire_invalid_onion_payload called!\n"); abort(); }
 /* Generated stub for towire_invalid_realm */
 u8 *towire_invalid_realm(const tal_t *ctx UNNEEDED)
 { fprintf(stderr, "towire_invalid_realm called!\n"); abort(); }