features: add EXPERIMENTAL option_onion_messages from draft.

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

common/features.c

@@ -56,6 +56,13 @@ static const struct feature_style feature_styles[] = {
 	  .copy_style = { [INIT_FEATURE] = FEATURE_REPRESENT,
 			  [NODE_ANNOUNCE_FEATURE] = FEATURE_REPRESENT,
 			  [CHANNEL_FEATURE] = FEATURE_REPRESENT_AS_OPTIONAL } },
+#if EXPERIMENTAL_FEATURES
+	{ OPT_ONION_MESSAGES,
+	  .copy_style = { [INIT_FEATURE] = FEATURE_REPRESENT,
+			  [NODE_ANNOUNCE_FEATURE] = FEATURE_REPRESENT,
+			  [BOLT11_FEATURE] = FEATURE_REPRESENT,
+			  [CHANNEL_FEATURE] = FEATURE_REPRESENT_AS_OPTIONAL} },
+#endif
 };
 
 static enum feature_copy_style feature_copy_style(u32 f, enum feature_place p)

common/features.h

@@ -99,4 +99,11 @@ u8 *featurebits_or(const tal_t *ctx, const u8 *f1 TAKES, const u8 *f2 TAKES);
 #define OPT_BASIC_MPP				16
 #define OPT_LARGE_CHANNELS			18
 
+/* BOLT-9fc25cfd2895578c0b1ab701ebe6c1eb67a19623 #9:
+ *
+ * | 102/103 | `option_onion_messages` |... INC+ ...
+ */
+#if EXPERIMENTAL_FEATURES
+#define OPT_ONION_MESSAGES			102
+#endif
 #endif /* LIGHTNING_COMMON_FEATURES_H */

lightningd/lightningd.c

@@ -723,6 +723,9 @@ static struct feature_set *default_features(const tal_t *ctx)
 		OPTIONAL_FEATURE(OPT_BASIC_MPP),
 		OPTIONAL_FEATURE(OPT_GOSSIP_QUERIES_EX),
 		OPTIONAL_FEATURE(OPT_STATIC_REMOTEKEY),
+#if EXPERIMENTAL_FEATURES
+		OPTIONAL_FEATURE(OPT_ONION_MESSAGES),
+#endif
 	};
 
 	for (size_t i = 0; i < ARRAY_SIZE(features); i++) {