keysend: Add maxfee to keysend for consistency with pay

.msggen.json

@@ -1521,6 +1521,7 @@
             "KeySend.extratlvs": 9,
             "KeySend.label": 3,
             "KeySend.maxdelay": 6,
+            "KeySend.maxfee": 11,
             "KeySend.maxfeepercent": 4,
             "KeySend.msatoshi": 2,
             "KeySend.retry_for": 5,
@@ -6362,6 +6363,10 @@
             "added": "pre-v0.10.1",
             "deprecated": null
         },
+        "KeySend.maxfee": {
+            "added": "v24.11",
+            "deprecated": null
+        },
         "KeySend.maxfeepercent": {
             "added": "pre-v0.10.1",
             "deprecated": null

CHANGELOG.md

@@ -3,6 +3,11 @@ All notable changes to this project will be documented in this file.
 
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/).
 
+## [Unreleased]
+
+### Added
+
+  - keysend: Add `maxfee` to keysend for consistency with pay. ([#7227])
 
 ## [24.08] - 2024-08-28: "Steel Backed-up Channels"
 

cln-grpc/src/test.rs

@@ -293,6 +293,7 @@ fn test_keysend() {
                 }],
             }),
             extratlvs: None,
+            maxfee: None
         };
 
     let u: cln_rpc::model::requests::KeysendRequest = g.into();

contrib/msggen/msggen/schema.json

@@ -15048,6 +15048,13 @@
             "description": [
               "Dictionary of additional fields to insert into the final tlv. The format is 'fieldnumber': 'hexstring'."
             ]
+          },
+          "maxfee": {
+            "added": "v24.11",
+            "type": "msat",
+            "description": [
+              "*maxfee* overrides both *maxfeepercent* and *exemptfee* defaults (and if you specify *maxfee* you cannot specify either of those), and creates an absolute limit on what fee we will pay. This allows you to implement your own heuristics rather than the primitive ones used here."
+            ]
           }
         }
       },

doc/schemas/lightning-keysend.json

@@ -103,6 +103,13 @@
         "description": [
           "Dictionary of additional fields to insert into the final tlv. The format is 'fieldnumber': 'hexstring'."
         ]
+      },
+      "maxfee": {
+        "added": "v24.11",
+        "type": "msat",
+        "description": [
+          "*maxfee* overrides both *maxfeepercent* and *exemptfee* defaults (and if you specify *maxfee* you cannot specify either of those), and creates an absolute limit on what fee we will pay. This allows you to implement your own heuristics rather than the primitive ones used here."
+        ]
       }
     }
   },

plugins/keysend.c

@@ -23,7 +23,7 @@ static u64 *accepted_extra_tlvs;
  * ================
  *
  * The keysend modifier adds the payment preimage to the TLV payload. This
- * enables the recipient to accept the payment despite it not correspondin to
+ * enables the recipient to accept the payment despite it not corresponding to
  * an invoice that the recipient created. Keysend does not provide any proof
  * or payment, but does not require an out-of-band communication round to get
  * an invoice first.
@@ -215,7 +215,7 @@ static struct command_result *json_keysend(struct command *cmd, const char *buf,
 {
 	struct payment *p;
 	const char *label;
-	struct amount_msat *exemptfee, *msat;
+	struct amount_msat *exemptfee, *msat, *maxfee;
 	struct node_id *destination;
 	u64 *maxfee_pct_millionths;
 	u32 *maxdelay;
@@ -237,6 +237,7 @@ static struct command_result *json_keysend(struct command *cmd, const char *buf,
 		   p_opt_def("exemptfee", param_msat, &exemptfee, AMOUNT_MSAT(5000)),
 		   p_opt("extratlvs", param_extra_tlvs, &extra_fields),
 		   p_opt("routehints", param_routehint_array, &hints),
+		   p_opt("maxfee", param_msat, &maxfee),
 		   p_opt_dev("dev_use_shadow", param_bool, &dev_use_shadow, true),
 		   NULL))
 		return command_param_failed();
@@ -284,7 +285,18 @@ static struct command_result *json_keysend(struct command *cmd, const char *buf,
 	payment_mod_keysend_get_data(p)->extra_tlvs =
 	    tal_steal(p, extra_fields);
 
-	payment_mod_exemptfee_get_data(p)->amount = *exemptfee;
+	if (maxfee) {
+		if (maxfee_pct_millionths || exemptfee) {
+			return command_fail(
+				cmd, JSONRPC2_INVALID_PARAMS,
+				"If you specify maxfee, cannot specify maxfeepercent or exemptfee.");
+		}
+		p->constraints.fee_budget = *maxfee;
+		payment_mod_exemptfee_get_data(p)->amount = AMOUNT_MSAT(0);
+	} else {
+		payment_mod_exemptfee_get_data(p)->amount = *exemptfee;
+	}
+
 	payment_mod_shadowroute_get_data(p)->use_shadow = *dev_use_shadow;
 	p->label = tal_steal(p, label);