sendpay: add payment_metadata argument.

And document the missing arguments.

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

common/onion.c

@@ -71,7 +71,8 @@ u8 *onion_final_hop(const tal_t *ctx,
 		    struct amount_msat total_msat,
 		    const struct pubkey *blinding,
 		    const u8 *enctlv,
-		    const struct secret *payment_secret)
+		    const struct secret *payment_secret,
+		    const u8 *payment_metadata)
 {
 	struct tlv_tlv_payload *tlv = tlv_tlv_payload_new(tmpctx);
 	struct tlv_tlv_payload_payment_data tlv_pdata;
@@ -102,6 +103,7 @@ u8 *onion_final_hop(const tal_t *ctx,
 		tlv_pdata.total_msat = total_msat.millisatoshis; /* Raw: TLV convert */
 		tlv->payment_data = &tlv_pdata;
 	}
+	tlv->payment_metadata = cast_const(u8 *, payment_metadata);
 #if EXPERIMENTAL_FEATURES
 	tlv->blinding_point = cast_const(struct pubkey *, blinding);
 	tlv->encrypted_recipient_data = cast_const(u8 *, enctlv);

common/onion.h

@@ -36,14 +36,15 @@ u8 *onion_nonfinal_hop(const tal_t *ctx,
 		       const struct pubkey *blinding,
 		       const u8 *enctlv);
 
-/* Note that this can fail if we supply payment_secret and !use_tlv! */
+/* Note that this can fail if we supply payment_secret or payment_metadata and !use_tlv! */
 u8 *onion_final_hop(const tal_t *ctx,
 		    struct amount_msat forward,
 		    u32 outgoing_cltv,
 		    struct amount_msat total_msat,
 		    const struct pubkey *blinding,
 		    const u8 *enctlv,
-		    const struct secret *payment_secret);
+		    const struct secret *payment_secret,
+		    const u8 *payment_metadata);
 
 /**
  * onion_payload_length: measure payload length in decrypted onion.

contrib/pyln-client/pyln/client/lightning.py

@@ -1128,7 +1128,7 @@ class LightningRpc(UnixDomainSocketRpc):
         }
         return self.call("plugin", payload)
 
-    def sendpay(self, route, payment_hash, label=None, msatoshi=None, bolt11=None, payment_secret=None, partid=None, groupid=None):
+    def sendpay(self, route, payment_hash, label=None, msatoshi=None, bolt11=None, payment_secret=None, partid=None, groupid=None, payment_metadata=None):
         """
         Send along {route} in return for preimage of {payment_hash}.
         """
@@ -1141,6 +1141,7 @@ class LightningRpc(UnixDomainSocketRpc):
             "payment_secret": payment_secret,
             "partid": partid,
             "groupid": groupid,
+            "payment_metadata": payment_metadata,
         }
         return self.call("sendpay", payload)
 

devtools/onion.c

@@ -80,7 +80,7 @@ static void do_generate(int argc, char **argv,
 					       take(onion_final_hop(NULL,
 								    amt, i, amt,
 								    NULL, NULL,
-								    NULL)));
+								    NULL, NULL)));
 			else
 				sphinx_add_hop(sp, &path[i],
 					       take(onion_nonfinal_hop(NULL,

doc/lightning-sendpay.7.md

@@ -5,7 +5,7 @@ SYNOPSIS
 --------
 
 **sendpay** *route* *payment\_hash* [*label*] [*msatoshi*]
-[*bolt11*] [*payment_secret*] [*partid*]
+[*bolt11*] [*payment_secret*] [*partid*] [*localofferid*] [*groupid*] [*payment_metadata*]
 
 DESCRIPTION
 -----------
@@ -44,6 +44,16 @@ partial payments with the same *payment_hash*.  The *msatoshi* amount
 *payment_hash* must be equal, and **sendpay** will fail if there are
 already *msatoshi* worth of payments pending.
 
+The *localofferid* value indicates that this payment is being made for a local
+send_invoice offer: this ensures that we only send a payment for a single-use
+offer once.
+
+*groupid* allows you to attach a number which appears in **listsendpays** so
+payments can be identified as part of a logical group.  The *pay* plugin uses
+this to identify one attempt at a MPP payment, for example.
+
+*payment_metadata* is placed in the final onion hop TLV.
+
 Once a payment has succeeded, calls to **sendpay** with the same
 *payment\_hash* but a different *msatoshi* or destination will fail;
 this prevents accidental multiple payments. Calls to **sendpay** with
@@ -94,6 +104,7 @@ The following error codes may occur:
     will be routing failure object.
 -   204: Failure along route; retry a different route. The *data* field
     of the error will be routing failure object.
+-   212: *localofferid* refers to an invalid, or used, local offer.
 
 A routing failure object has the fields below:
 -   *erring\_index*. The index of the node along the route that reported

lightningd/pay.c

@@ -1122,7 +1122,8 @@ send_payment(struct lightningd *ld,
 	     const char *label TAKES,
 	     const char *invstring TAKES,
 	     const struct sha256 *local_offer_id,
-	     const struct secret *payment_secret)
+	     const struct secret *payment_secret,
+	     const u8 *payment_metadata)
 {
 	unsigned int base_expiry;
 	struct onionpacket *packet;
@@ -1174,7 +1175,7 @@ send_payment(struct lightningd *ld,
 				route[i].amount,
 				base_expiry + route[i].delay,
 				total_msat, route[i].blinding, route[i].enctlv,
-				payment_secret);
+				payment_secret, payment_metadata);
 	if (!onion) {
 		return command_fail(cmd, PAY_DESTINATION_PERM_FAIL,
 				    "Destination does not support"
@@ -1422,7 +1423,8 @@ static struct command_result *json_sendpay(struct command *cmd,
 	const char *invstring, *label;
 	u64 *partid, *group;
 	struct secret *payment_secret;
-	struct sha256 *local_offer_id = NULL;
+	struct sha256 *local_offer_id;
+	u8 *payment_metadata;
 
 	/* For generating help, give new-style. */
 	if (!param(cmd, buffer, params,
@@ -1436,6 +1438,7 @@ static struct command_result *json_sendpay(struct command *cmd,
 		   p_opt_def("partid", param_u64, &partid, 0),
 		   p_opt("localofferid", param_sha256, &local_offer_id),
 		   p_opt("groupid", param_u64, &group),
+		   p_opt("payment_metadata", param_bin_from_hex, &payment_metadata),
 		   NULL))
 		return command_param_failed();
 
@@ -1485,7 +1488,8 @@ static struct command_result *json_sendpay(struct command *cmd,
 			    route,
 			    final_amount,
 			    msat ? *msat : final_amount,
-			    label, invstring, local_offer_id, payment_secret);
+			    label, invstring, local_offer_id,
+			    payment_secret, payment_metadata);
 }
 
 static const struct json_command sendpay_command = {