common/tlvstream: allow fromwire_tlv to accept *any* unknown type.

This is used for keysend if EXPERIMENTAL_FEATURES is set.

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

plugins/keysend.c

@@ -1,6 +1,7 @@
 #include "config.h"
 #include <ccan/array_size/array_size.h>
 #include <ccan/asort/asort.h>
+#include <ccan/cast/cast.h>
 #include <ccan/tal/str/str.h>
 #include <common/json_tok.h>
 #include <common/memleak.h>
@@ -342,7 +343,7 @@ static struct command_result *htlc_accepted_call(struct command *cmd,
 	struct out_req *req;
 	struct timeabs now = time_now();
 	const char *err;
-	u64 *allowed = tal_arr(cmd, u64, 1);
+	u64 *allowed;
 	size_t err_off;
 	u64 err_type;
 
@@ -360,8 +361,15 @@ static struct command_result *htlc_accepted_call(struct command *cmd,
 		return htlc_accepted_continue(cmd, NULL);
 	}
 
+#if EXPERIMENTAL_FEATURES
+	/* Note: This is a magic pointer value, not an actual array */
+	allowed = cast_const(u64 *, FROMWIRE_TLV_ANY_TYPE);
+#else
 	/* We explicitly allow our type. */
-	allowed[0] = 5482373484;
+	allowed = tal_arr(cmd, u64, 1);
+	allowed[0] = PREIMAGE_TLV_TYPE;
+#endif
+
 	payload = tlv_tlv_payload_new(cmd);
 	if (!fromwire_tlv(&rawpayload, &max, tlvs_tlv_tlv_payload, TLVS_ARRAY_SIZE_tlv_tlv_payload,
 			  payload, &payload->fields, allowed, &err_off, &err_type)) {
@@ -380,6 +388,7 @@ static struct command_result *htlc_accepted_call(struct command *cmd,
 			preimage_field = field;
 			break;
 		} else if (field->numtype % 2 == 0 && field->meta == NULL) {
+			/* This can only happen with FROMWIRE_TLV_ANY_TYPE! */
 			unknown_field = field;
 		}
 	}
@@ -390,19 +399,10 @@ static struct command_result *htlc_accepted_call(struct command *cmd,
 		return htlc_accepted_continue(cmd, NULL);
 
 	if (unknown_field != NULL) {
-#if !EXPERIMENTAL_FEATURES
-		plugin_log(cmd->plugin, LOG_UNUSUAL,
-			   "Payload contains unknown even TLV-type %" PRIu64
-			   ", can't safely accept the keysend. Deferring to "
-			   "other plugins.",
-			   unknown_field->numtype);
-		return htlc_accepted_continue(cmd, NULL);
-#else
 		plugin_log(cmd->plugin, LOG_INFORM,
 			   "Experimental: Accepting the keysend payment "
 			   "despite having unknown even TLV type %" PRIu64 ".",
 			   unknown_field->numtype);
-#endif
 	}
 
 	/* If malformed (amt is compulsory), let lightningd handle it. */

wire/tlvstream.c

@@ -8,6 +8,11 @@
 #define SUPERVERBOSE(...)
 #endif
 
+/* This simply needs to be an address which is neither NULL nor a
+ * tal_arr return */
+static const u64 dummy;
+const u64 *FROMWIRE_TLV_ANY_TYPE = &dummy;
+
 static int tlv_field_cmp(const struct tlv_field *a, const struct tlv_field *b,
 			 void *x)
 {
@@ -117,6 +122,9 @@ static bool tlv_type_is_allowed(const struct tlv_field *f,
 	if (f->numtype % 2 != 0)
 		return true;
 
+	if (extra_types == FROMWIRE_TLV_ANY_TYPE)
+		return true;
+
 	/* Now iterate through the extras and see if we should make an
 	 * exception. */
 	for (size_t i = 0; i < tal_count(extra_types); i++)

wire/tlvstream.h

@@ -45,7 +45,7 @@ struct tlv_field *tlv_make_fields_(const struct tlv_record_type *types,
  * @types / @num_types: table of known tlv types
  * @record: the tlv to hand to @type-specific decode
  * @fields: the fields array to populate
- * @extra_types: tal_arr or NULL of unknown types to allow
+ * @extra_types: tal_arr of unknown types to allow, or NULL, or FROMWIRE_TLV_ANY_TYPE.
  * @err_off: NULL, or set to offset in tlv stream which failed.
  * @err_type: NULL, or set to tlv type which failed (or 0 if malformed)
  */
@@ -61,6 +61,9 @@ void towire_tlv(u8 **pptr,
  * tlv malformed) */
 size_t tlv_field_offset(const u8 *tlvstream, size_t tlvlen, u64 fieldtype);
 
+/* Constant for fromwire_tlv to allow absolutely any unknown type. */
+extern const u64 *FROMWIRE_TLV_ANY_TYPE;
+
 /* Generic primitive setters for tlvstreams. */
 void tlvstream_set_raw(struct tlv_field **stream, u64 type, void *value TAKES, size_t valuelen);
 void tlvstream_set_short_channel_id(struct tlv_field **stream, u64 type,