dual-funding: update fee_step to be a feerate

Using a 'feestep' is more restrictive than you'd want, instead we
enforce that the next feerate must be at least 1/64th more than the
last, but put no upper limit on it

Includes update to lnprototest changes

Contributed-By: Vincenzo Palazzo <vincenzopalazzodev@gmail.com>
Changelog-EXPERIMENTAL: Protocol: Replaces init_rbf's `fee_step` for RBF of v2 opens with `funding_feerate_perkw`, breaking change

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

@@ -1039,12 +1039,13 @@ def openchannel_update(self, channel_id, psbt, *args, **kwargs):
         }
         return self.call("openchannel_update", payload)
 
-    def openchannel_bump(self, channel_id, amount, initialpsbt):
+    def openchannel_bump(self, channel_id, amount, initialpsbt, funding_feerate=None):
         """ Initiate an RBF for an in-progress open """
         payload = {
             "channel_id": channel_id,
             "amount": amount,
             "initialpsbt": initialpsbt,
+            "funding_feerate": funding_feerate,
         }
         return self.call("openchannel_bump", payload)
 

doc/lightning-listpeers.7.md

@@ -132,7 +132,6 @@ On success, an object containing **peers** is returned.  It is an array of objec
     - **initial_feerate** (string): The feerate for the initial funding transaction in per-1000-weight, with "kpw" appended
     - **last_feerate** (string): The feerate for the latest funding transaction in per-1000-weight, with "kpw" appended
     - **next_feerate** (string): The minimum feerate for the next funding transaction in per-1000-weight, with "kpw" appended
-    - **next_fee_step** (u32): The number of fee steps so far, plus one
 - **log** (array of objects, optional): if *level* is specified, logs for this peer:
   - **type** (string) (one of "SKIPPED", "BROKEN", "UNUSUAL", "INFO", "DEBUG", "IO_IN", "IO_OUT")
 
@@ -376,4 +375,4 @@ Main web site: <https://github.com/ElementsProject/lightning> Lightning
 RFC site (BOLT \#9):
 <https://github.com/lightningnetwork/lightning-rfc/blob/master/09-features.md>
 
-[comment]: # ( SHA256STAMP:6db6eb853f6c1953f05160cd9026ad6a8ccb97a016b15bc76242adc8026fa4ca)
+[comment]: # ( SHA256STAMP:91d30768a795456c75c72cf499df529ae8dbcc8088d06d1ed27150272425ab37)

doc/lightning-openchannel_bump.7.md

@@ -4,7 +4,7 @@ lightning-openchannel\_bump -- Command to initiate a channel RBF
 SYNOPSIS
 --------
 
-**openchannel_bump** *channel_id* *amount* *initalpsbt*
+**openchannel_bump** *channel_id* *amount* *initalpsbt* \[*funding_feerate*\]
 
 DESCRIPTION
 -----------
@@ -26,6 +26,10 @@ Must have the Non-Witness UTXO (PSBT\_IN\_NON\_WITNESS\_UTXO) set for
 every input. An error (code 309) will be returned if this requirement
 is not met.
 
+*funding_feerate* is an optional field. Sets the feerate for the
+funding transaction. Defaults to 1/64th greater than the last
+feerate used for this channel.
+
 RETURN VALUE
 ------------
 

doc/schemas/listpeers.schema.json

@@ -579,7 +579,6 @@
 					    "short_channel_id": { },
 					    "channel_id": { },
 					    "funding_txid": { },
-					    "inflight": { },
 					    "close_to": { },
 					    "private": { },
 					    "opener": { },
@@ -635,7 +634,6 @@
 					    "initial_feerate": { },
 					    "last_feerate": { },
 					    "next_feerate": { },
-					    "next_fee_step": { },
 					    "inflight": { },
 					    "last_tx_fee": { },
 					    "last_tx_fee_msat": { },
@@ -715,12 +713,13 @@
 					    "out_fulfilled_msat": { },
 					    "out_msatoshi_fulfilled": { },
 					    "htlcs": { },
-					    "inflight": { },
+					    "initial_feerate": { },
+					    "last_feerate": { },
+					    "next_feerate": { },
 					    "close_to_addr": { },
 					    "initial_feerate": { },
 					    "last_feerate": { },
 					    "next_feerate": { },
-					    "next_fee_step": { },
 					    "direction": { },
 					    "last_tx_fee": {
 						"deprecated": true
@@ -800,13 +799,14 @@
 					    "out_fulfilled_msat": { },
 					    "out_msatoshi_fulfilled": { },
 					    "htlcs": { },
-					    "inflight": { },
+					    "initial_feerate": { },
+					    "last_feerate": { },
+					    "next_feerate": { },
 					    "last_tx_fee": { },
 					    "close_to_addr": { },
 					    "initial_feerate": { },
 					    "last_feerate": { },
 					    "next_feerate": { },
-					    "next_fee_step": { },
 					    "last_tx_fee": { },
 					    "last_tx_fee_msat": { },
 					    "direction": {
@@ -822,7 +822,7 @@
 				    },
 				    "then": {
 					"additionalProperties": false,
-					"required": [ "initial_feerate", "last_feerate", "next_feerate", "next_fee_step" ],
+					"required": [ "initial_feerate", "last_feerate", "next_feerate" ],
 					"properties": {
 					    "state": { },
 					    "scratch_txid": { },
@@ -831,7 +831,6 @@
 					    "short_channel_id": { },
 					    "channel_id": { },
 					    "funding_txid": { },
-					    "inflight": { },
 					    "close_to": { },
 					    "private": { },
 					    "opener": { },
@@ -901,10 +900,6 @@
 					    "next_feerate": {
 						"type": "string",
 						"description": "The minimum feerate for the next funding transaction in per-1000-weight, with \"kpw\" appended"
-					    },
-					    "next_fee_step": {
-						"type": "u32",
-						"description": "The number of fee steps so far, plus one"
 					    }
 					}
 				    }

lightningd/dual_open_control.c

@@ -1986,12 +1986,15 @@ json_openchannel_bump(struct command *cmd,
 	struct channel *channel;
 	struct amount_sat *amount, psbt_val;
 	struct wally_psbt *psbt;
+	u32 last_feerate_perkw, next_feerate_min, *feerate_per_kw_funding;
 	struct open_attempt *oa;
 
 	if (!param(cmd, buffer, params,
 		   p_req("channel_id", param_channel_id, &cid),
 		   p_req("amount", param_sat, &amount),
 		   p_req("initialpsbt", param_psbt, &psbt),
+		   p_opt("funding_feerate", param_feerate,
+			 &feerate_per_kw_funding),
 		   NULL))
 		return command_param_failed();
 
@@ -2033,6 +2036,20 @@ json_openchannel_bump(struct command *cmd,
 				    type_to_string(tmpctx, struct channel_id,
 						   cid));
 
+	last_feerate_perkw = channel_last_funding_feerate(channel);
+	next_feerate_min = last_feerate_perkw * 65 / 64;
+	assert(next_feerate_min > last_feerate_perkw);
+	if (!feerate_per_kw_funding) {
+		feerate_per_kw_funding = tal(cmd, u32);
+		*feerate_per_kw_funding = next_feerate_min;
+	} else if (*feerate_per_kw_funding < next_feerate_min)
+		return command_fail(cmd, JSONRPC2_INVALID_PARAMS,
+				    "Next feerate must be at least 1/64th"
+				    " greater than the last. Min req %u,"
+				    " you proposed %u",
+				    next_feerate_min,
+				    *feerate_per_kw_funding);
+
 	/* BOLT #2:
 	 *  - if both nodes advertised `option_support_large_channel`:
 	 *    - MAY set `funding_satoshis` greater than or equal to 2^24 satoshi.
@@ -2092,7 +2109,9 @@ json_openchannel_bump(struct command *cmd,
 						   psbt));
 
 	subd_send_msg(channel->owner,
-		      take(towire_dualopend_rbf_init(NULL, *amount, psbt)));
+		      take(towire_dualopend_rbf_init(NULL, *amount,
+						     *feerate_per_kw_funding,
+						     psbt)));
 	return command_still_pending(cmd);
 }
 
@@ -2876,7 +2895,7 @@ void peer_restart_dualopend(struct peer *peer,
 	u32 max_to_self_delay;
 	struct amount_msat min_effective_htlc_capacity;
 	struct channel_config unused_config;
-	struct channel_inflight *inflight, *first_inflight;
+	struct channel_inflight *inflight;
         int hsmfd;
 	u8 *msg;
 
@@ -2917,12 +2936,6 @@ void peer_restart_dualopend(struct peer *peer,
 	inflight = channel_current_inflight(channel);
 	assert(inflight);
 
-	/* Get the first inflight to figure out the original feerate
-	 * for this channel. It's fine if it's the same as the current */
-	first_inflight = list_top(&channel->inflights,
-				  struct channel_inflight,
-				  list);
-	assert(first_inflight);
 	msg = towire_dualopend_reinit(NULL,
 				      chainparams,
 				      peer->ld->our_features,
@@ -2939,7 +2952,6 @@ void peer_restart_dualopend(struct peer *peer,
 				      channel->minimum_depth,
 				      &inflight->funding->txid,
 				      inflight->funding->outnum,
-				      first_inflight->funding->feerate,
 				      inflight->funding->feerate,
 				      channel->funding,
 				      channel->our_msat,

lightningd/peer_control.c

@@ -774,32 +774,32 @@ static void json_add_channel(struct lightningd *ld,
 
 	if (!list_empty(&channel->inflights)) {
 		struct channel_inflight *initial, *inflight;
-		u32 last_feerate, next_feerate, feerate;
-		u8 feestep;
-
-		last_feerate = channel_last_funding_feerate(channel);
-		assert(last_feerate > 0);
-		next_feerate = last_feerate + last_feerate / 4;
+		u32 last_feerate, next_feerate;
 
 		initial = list_top(&channel->inflights,
 				   struct channel_inflight, list);
-		feerate = initial->funding->feerate;
-
 		json_add_string(response, "initial_feerate",
-			        tal_fmt(tmpctx, "%d%s", feerate,
+			        tal_fmt(tmpctx, "%d%s",
+					initial->funding->feerate,
 					feerate_style_name(FEERATE_PER_KSIPA)));
+
+		last_feerate = channel_last_funding_feerate(channel);
+		assert(last_feerate > 0);
 		json_add_string(response, "last_feerate",
 				tal_fmt(tmpctx, "%d%s", last_feerate,
 					feerate_style_name(FEERATE_PER_KSIPA)));
+
+		/* BOLT-9e7723387c8859b511e178485605a0b9133b9869 #2:
+		 * - MUST set `funding_feerate_perkw` greater than or equal to
+		 *   65/64 times the last sent `funding_feerate_perkw`
+		 *   rounded down.
+		 */
+		next_feerate = last_feerate * 65 / 64;
+		assert(next_feerate > last_feerate);
 		json_add_string(response, "next_feerate",
 				tal_fmt(tmpctx, "%d%s", next_feerate,
 					feerate_style_name(FEERATE_PER_KSIPA)));
 
-		/* Now we derive the feestep */
-		for (feestep = 0; feerate < next_feerate; feestep++)
-			feerate += feerate / 4;
-		json_add_num(response, "next_fee_step", feestep);
-
 		/* List the inflights */
 		json_array_start(response, "inflight");
 		list_for_each(&channel->inflights, inflight, list) {