wire: Let the TLV _is_valid function actually return validity

I got this one wrong myself, since the function name implied a boolean
result. So I changed it to take the optional err_index as argument.

lightningd/peer_htlcs.c

@@ -793,7 +793,8 @@ static void htlc_accepted_hook_serialize(struct htlc_accepted_hook_payload *p,
  * correctly. */
 static bool htlc_accepted_can_continue(struct route_step *rs)
 {
-	if (rs->type == SPHINX_TLV_PAYLOAD && !tlv_payload_is_valid(rs->payload.tlv)) {
+	if (rs->type == SPHINX_TLV_PAYLOAD &&
+	    !tlv_payload_is_valid(rs->payload.tlv, NULL)) {
 		SUPERVERBOSE("Encoding of TLV payload is invalid");
 		return false;
 	}

tools/gen/header_template

@@ -75,10 +75,12 @@ bool fromwire_${tlv.name}(const u8 **cursor, size_t *max, struct ${tlv.struct_na
  * - Types must be in monotonic non-repeating order
  * - We must understand all even types
  *
- * Returns the index of the field that was invalid, or -1 if the stream is
- * valid.
+ * Returns false if an error was detected, otherwise returns true. If err_index
+ * is non-null and we detect an error it is set to the index of the first error
+ * detected.
  */
-int ${tlv.name}_is_valid(const struct ${tlv.struct_name()} *record);
+bool ${tlv.name}_is_valid(const struct ${tlv.struct_name()} *record,
+			  size_t *err_index);
 
 % if tlv.name in options.expose_tlv_type:
 #define TLVS_${tlv.name.upper()}_ARRAY_SIZE ${len(tlv.messages)}

tools/gen/impl_template

@@ -306,7 +306,7 @@ fail:
 	return false;
 }
 
-int ${tlv.name}_is_valid(const struct ${tlv.struct_name()} *record)
+bool ${tlv.name}_is_valid(const struct ${tlv.struct_name()} *record, size_t *err_index)
 {
 	size_t numfields = tal_count(record->fields);
 	bool first = true;
@@ -321,8 +321,10 @@ int ${tlv.name}_is_valid(const struct ${tlv.struct_name()} *record)
 			 *   - otherwise, if `type` is odd:
 			 *     - MUST discard the next `length` bytes.
 			 */
-			SUPERVERBOSE("Unknown even type in TLV");
-			return i;
+			SUPERVERBOSE("unknown even");
+			if (err_index != NULL)
+				*err_index = i;
+			return false;
 		} else if (!first && f->numtype <= prev_type) {
 			/* BOLT #1:
 			 *  - if decoded `type`s are not monotonically-increasing:
@@ -332,12 +334,14 @@ int ${tlv.name}_is_valid(const struct ${tlv.struct_name()} *record)
 				SUPERVERBOSE("duplicate tlv type");
 			else
 				SUPERVERBOSE("invalid ordering");
-			return i;
+			if (err_index != NULL)
+				*err_index = i;
+			return false;
 		}
 		first = false;
 		prev_type = f->numtype;
 	}
-	return -1;
+	return true;
 }
 
 % endfor ##  END TLV's

wallet/test/run-wallet.c

@@ -546,7 +546,8 @@ void subd_req_(const tal_t *ctx UNNEEDED,
 void subd_send_msg(struct subd *sd UNNEEDED, const u8 *msg_out UNNEEDED)
 { fprintf(stderr, "subd_send_msg called!\n"); abort(); }
 /* Generated stub for tlv_payload_is_valid */
-int tlv_payload_is_valid(const struct tlv_tlv_payload *record UNNEEDED)
+bool tlv_payload_is_valid(const struct tlv_tlv_payload *record UNNEEDED,
+			  size_t *err_index UNNEEDED)
 { fprintf(stderr, "tlv_payload_is_valid called!\n"); abort(); }
 /* Generated stub for topology_add_sync_waiter_ */
 void topology_add_sync_waiter_(const tal_t *ctx UNNEEDED,