tlv: Add raw fields so we can store unknown fields as well

tools/gen/header_template

@@ -53,6 +53,11 @@ struct ${struct.struct_name()} {
 ## Structs for TLVs
 % for tlv in tlvs.values():
 struct ${tlv.struct_name()} {
+        /* Raw fields including unknown ones. */
+        struct tlv_field *fields;
+
+	/* TODO The following explicit fields could just point into the
+	 * tlv_field entries above to save on memory. */
     % for msg in tlv.messages.values():
         struct ${msg.struct_name()} *${msg.name};
     % endfor

tools/gen/impl_template

@@ -157,7 +157,11 @@ fromwire_${type_}(${'ctx, ' if f.needs_context() else ''}&cursor, &plen, ${'*' i
 ${tlv.type_name()} *${tlv.struct_name()}_new(const tal_t *ctx)
 {
 	/* Initialize everything to NULL. (Quiet, C pedants!) */
-	return talz(ctx, struct ${tlv.struct_name()});
+	${tlv.type_name()} *inst = talz(ctx, struct ${tlv.struct_name()});
+
+	/* Initialized the fields to an empty array. */
+	inst->fields = tal_arr(inst, struct tlv_field, 0);
+	return inst;
 }
 
     % for msg in tlv.messages.values():

wire/tlvstream.h

@@ -15,6 +15,19 @@ struct tlv_record_type {
 	void (*fromwire)(const u8 **cursor, size_t *max, void *record);
 };
 
+/* A single TLV field, consisting of the data and its associated metadata. */
+struct tlv_field {
+	/* If this is a type that is known to c-lightning we have a pointer to
+	 * the metadata. */
+	const struct tlv_record_type *meta;
+
+	/* In any case we'll have the numeric type, even if we don't have a
+	 * name that we can call it. */
+	u64 numtype;
+	size_t length;
+	u8 *value;
+};
+
 /* Pull all tlvs from a stream.  Return false and calls fromwire_fail() on
  * error. */
 bool fromwire_tlvs(const u8 **cursor, size_t *max,