hooks: Add the raw payload to the htlc_accepted call

Since we might soon be changing the payload it is a good idea to not just
expose the v0 payload, but also the raw payload for the plugin to
interpret. This might also include payloads that `lightningd` itself cannot
understand, but the plugin might.

Signed-off-by: Christian Decker <decker.christian@gmail.com>
Suggested-by: Corné Plooy <@bitonic-cjp>

common/sphinx.c

@@ -434,6 +434,8 @@ struct route_step *process_onionpacket(
 	deserialize_hop_data(&step->hop_data, paddedheader);
 
         memcpy(&step->next->mac, step->hop_data.hmac, SECURITY_PARAMETER);
+	step->raw_payload = tal_dup_arr(step, u8, paddedheader + 1,
+					HOP_DATA_SIZE - 1 - HMAC_SIZE, 0);
 
 	memcpy(&step->next->routinginfo, paddedheader + HOP_DATA_SIZE, ROUTING_INFO_SIZE);
 

common/sphinx.h

@@ -77,6 +77,7 @@ struct route_step {
 	enum route_next_case nextcase;
 	struct onionpacket *next;
 	struct hop_data hop_data;
+	u8 *raw_payload;
 };
 
 /**

lightningd/peer_htlcs.c

@@ -718,6 +718,7 @@ static void htlc_accepted_hook_serialize(struct htlc_accepted_hook_payload *p,
 	s32 expiry = hin->cltv_expiry, blockheight = p->ld->topology->tip->height;
 	json_object_start(s, "onion");
 
+	json_add_hex_talarr (s, "payload", rs->raw_payload);
 	if (rs->hop_data.realm == 0x00) {
 		json_object_start(s, "per_hop_v0");
 		json_add_hex(s, "realm", &rs->hop_data.realm, 1);