lightningd: setchannel can set ignorefeelimits.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Changelog-Added: JSON-RPC: `setchannel` adds a new `ignorefeelimits` parameter to allow peer to set arbitrary commitment transaction fees on a per-channel basis.

.msggen.json

@@ -1402,6 +1402,7 @@
             "SetChannel.channels[].channel_id": 2,
             "SetChannel.channels[].fee_base_msat": 4,
             "SetChannel.channels[].fee_proportional_millionths": 5,
+            "SetChannel.channels[].ignore_fee_limits": 10,
             "SetChannel.channels[].maximum_htlc_out_msat": 8,
             "SetChannel.channels[].minimum_htlc_out_msat": 6,
             "SetChannel.channels[].peer_id": 1,
@@ -1415,7 +1416,8 @@
             "SetChannel.feeppm": 3,
             "SetChannel.htlcmax": 5,
             "SetChannel.htlcmin": 4,
-            "SetChannel.id": 1
+            "SetChannel.id": 1,
+            "SetChannel.ignorefeelimits": 7
         },
         "SetchannelResponse": {
             "SetChannel.channels[]": 1
@@ -5018,6 +5020,10 @@
             "added": "pre-v0.10.1",
             "deprecated": false
         },
+        "SetChannel.channels[].ignore_fee_limits": {
+            "added": "v23.08",
+            "deprecated": false
+        },
         "SetChannel.channels[].maximum_htlc_out_msat": {
             "added": "pre-v0.10.1",
             "deprecated": false
@@ -5066,6 +5072,10 @@
             "added": "pre-v0.10.1",
             "deprecated": false
         },
+        "SetChannel.ignorefeelimits": {
+            "added": "v23.08",
+            "deprecated": false
+        },
         "SignInvoice": {
             "added": "v23.02",
             "deprecated": null

cln-grpc/proto/node.proto

@@ -1639,6 +1639,7 @@ message SetchannelRequest {
 	optional Amount htlcmin = 4;
 	optional Amount htlcmax = 5;
 	optional uint32 enforcedelay = 6;
+	optional bool ignorefeelimits = 7;
 }
 
 message SetchannelResponse {
@@ -1651,6 +1652,7 @@ message SetchannelChannels {
 	optional string short_channel_id = 3;
 	Amount fee_base_msat = 4;
 	uint32 fee_proportional_millionths = 5;
+	optional bool ignore_fee_limits = 10;
 	Amount minimum_htlc_out_msat = 6;
 	optional string warning_htlcmin_too_low = 7;
 	Amount maximum_htlc_out_msat = 8;

cln-grpc/src/convert.rs

@@ -1521,6 +1521,7 @@ impl From<responses::SetchannelChannels> for pb::SetchannelChannels {
             short_channel_id: c.short_channel_id.map(|v| v.to_string()), // Rule #2 for type short_channel_id?
             fee_base_msat: Some(c.fee_base_msat.into()), // Rule #2 for type msat
             fee_proportional_millionths: c.fee_proportional_millionths, // Rule #2 for type u32
+            ignore_fee_limits: c.ignore_fee_limits, // Rule #2 for type boolean?
             minimum_htlc_out_msat: Some(c.minimum_htlc_out_msat.into()), // Rule #2 for type msat
             warning_htlcmin_too_low: c.warning_htlcmin_too_low, // Rule #2 for type string?
             maximum_htlc_out_msat: Some(c.maximum_htlc_out_msat.into()), // Rule #2 for type msat
@@ -2214,6 +2215,7 @@ impl From<requests::SetchannelRequest> for pb::SetchannelRequest {
             htlcmin: c.htlcmin.map(|f| f.into()), // Rule #2 for type msat?
             htlcmax: c.htlcmax.map(|f| f.into()), // Rule #2 for type msat?
             enforcedelay: c.enforcedelay, // Rule #2 for type u32?
+            ignorefeelimits: c.ignorefeelimits, // Rule #2 for type boolean?
         }
     }
 }
@@ -2880,6 +2882,7 @@ impl From<pb::SetchannelRequest> for requests::SetchannelRequest {
             htlcmin: c.htlcmin.map(|a| a.into()), // Rule #1 for type msat?
             htlcmax: c.htlcmax.map(|a| a.into()), // Rule #1 for type msat?
             enforcedelay: c.enforcedelay, // Rule #1 for type u32?
+            ignorefeelimits: c.ignorefeelimits, // Rule #1 for type boolean?
         }
     }
 }

cln-rpc/src/model.rs

@@ -1409,6 +1409,8 @@ pub mod requests {
 	    pub htlcmax: Option<Amount>,
 	    #[serde(skip_serializing_if = "Option::is_none")]
 	    pub enforcedelay: Option<u32>,
+	    #[serde(skip_serializing_if = "Option::is_none")]
+	    pub ignorefeelimits: Option<bool>,
 	}
 
 	impl From<SetchannelRequest> for Request {
@@ -4651,6 +4653,8 @@ pub mod responses {
 	    pub short_channel_id: Option<ShortChannelId>,
 	    pub fee_base_msat: Amount,
 	    pub fee_proportional_millionths: u32,
+	    #[serde(skip_serializing_if = "Option::is_none")]
+	    pub ignore_fee_limits: Option<bool>,
 	    pub minimum_htlc_out_msat: Amount,
 	    #[serde(skip_serializing_if = "Option::is_none")]
 	    pub warning_htlcmin_too_low: Option<String>,

contrib/pyln-testing/pyln/testing/grpc2py.py

@@ -1298,6 +1298,7 @@ def setchannel_channels2py(m):
         "short_channel_id": m.short_channel_id,  # PrimitiveField in generate_composite
         "fee_base_msat": amount2msat(m.fee_base_msat),  # PrimitiveField in generate_composite
         "fee_proportional_millionths": m.fee_proportional_millionths,  # PrimitiveField in generate_composite
+        "ignore_fee_limits": m.ignore_fee_limits,  # PrimitiveField in generate_composite
         "minimum_htlc_out_msat": amount2msat(m.minimum_htlc_out_msat),  # PrimitiveField in generate_composite
         "warning_htlcmin_too_low": m.warning_htlcmin_too_low,  # PrimitiveField in generate_composite
         "maximum_htlc_out_msat": amount2msat(m.maximum_htlc_out_msat),  # PrimitiveField in generate_composite

doc/lightning-setchannel.7.md

@@ -4,7 +4,7 @@ lightning-setchannel -- Command for configuring fees / htlc range advertized for
 SYNOPSIS
 --------
 
-**setchannel** *id* [*feebase*] [*feeppm*] [*htlcmin*] [*htlcmax*] [*enforcedelay*]
+**setchannel** *id* [*feebase*] [*feeppm*] [*htlcmin*] [*htlcmax*] [*enforcedelay*] [*ignorefeelimits*]
 
 DESCRIPTION
 -----------
@@ -62,6 +62,13 @@ only applied to a single rate increase per channel (we don't remember
 an arbitrary number of prior feerates) and if the node is restarted
 the updated configuration is enforced immediately.
 
+*ignorefeelimits* set to True means to allow the peer to set the commitment
+transaction fees (or closing transaction fees) to any value they want.  This is dangerous: they could
+set an exorbitant fee (so HTLCs are unenforcable), or a tiny fee (so that
+commitment transactions cannot be relayed), but avoids channel breakage
+in case of feerate disagreements.  (Note: the global `ignore_fee_limits`
+setting overrides this).
+
 RETURN VALUE
 ------------
 
@@ -72,6 +79,7 @@ On success, an object containing **channels** is returned.  It is an array of ob
 - **channel\_id** (hex): The channel\_id of the channel (always 64 characters)
 - **fee\_base\_msat** (msat): The resulting feebase (this is the BOLT #7 name)
 - **fee\_proportional\_millionths** (u32): The resulting feeppm (this is the BOLT #7 name)
+- **ignore\_fee\_limits** (boolean): If we are now allowing peer to set feerate on commitment transaction without restriction *(added v23.08)*
 - **minimum\_htlc\_out\_msat** (msat): The resulting htlcmin we will advertize (the BOLT #7 name is htlc\_minimum\_msat)
 - **maximum\_htlc\_out\_msat** (msat): The resulting htlcmax we will advertize (the BOLT #7 name is htlc\_maximum\_msat)
 - **short\_channel\_id** (short\_channel\_id, optional): the short\_channel\_id (if locked in)
@@ -107,4 +115,4 @@ RESOURCES
 
 Main web site: <https://github.com/ElementsProject/lightning>
 
-[comment]: # ( SHA256STAMP:0175aaf74aa6d75640d0b79f68b552b1b700f93ad7576465c73de93af04d71e6)
+[comment]: # ( SHA256STAMP:5209ba4d4bbe2d897d9824f95a97fa48d968e83ffec2e4cfbd87df6fd90c48f0)

doc/lightningd-config.5.md

@@ -332,7 +332,8 @@ falls below this.
   Allow nodes which establish channels to us to set any fee they want.
 This may result in a channel which cannot be closed, should fees
 increase, but make channels far more reliable since we never close it
-due to unreasonable fees.
+due to unreasonable fees.  Note that this can be set on a per-channel
+basis with lightning-setchannel(7).
 
 * **commit-time**=*MILLISECONDS*
 

doc/schemas/setchannel.request.json

@@ -23,6 +23,10 @@
     },
     "enforcedelay": {
       "type": "u32"
+    },
+    "ignorefeelimits": {
+      "added": "v23.08",
+      "type": "boolean"
     }
   }
 }

doc/schemas/setchannel.schema.json

@@ -18,7 +18,8 @@
           "fee_base_msat",
           "fee_proportional_millionths",
           "minimum_htlc_out_msat",
-          "maximum_htlc_out_msat"
+          "maximum_htlc_out_msat",
+          "ignore_fee_limits"
         ],
         "properties": {
           "peer_id": {
@@ -43,6 +44,11 @@
             "type": "u32",
             "description": "The resulting feeppm (this is the BOLT #7 name)"
           },
+          "ignore_fee_limits": {
+            "type": "boolean",
+            "added": "v23.08",
+            "description": "If we are now allowing peer to set feerate on commitment transaction without restriction"
+          },
           "minimum_htlc_out_msat": {
             "type": "msat",
             "description": "The resulting htlcmin we will advertize (the BOLT #7 name is htlc_minimum_msat)"

lightningd/channel_control.c

@@ -24,7 +24,7 @@
 #include <lightningd/peer_fd.h>
 #include <wally_bip32.h>
 
-static void update_feerates(struct lightningd *ld, const struct channel *channel)
+void channel_update_feerates(struct lightningd *ld, const struct channel *channel)
 {
 	u8 *msg;
 	u32 min_feerate, max_feerate;
@@ -71,7 +71,7 @@ static void try_update_feerates(struct lightningd *ld, struct channel *channel)
 	if (!channel->owner)
 		return;
 
-	update_feerates(ld, channel);
+	channel_update_feerates(ld, channel);
 }
 
 static void try_update_blockheight(struct lightningd *ld,

lightningd/channel_control.h

@@ -43,4 +43,6 @@ void channel_fallen_behind(struct channel *channel, const u8 *msg);
 /* Fresh channel_update for this channel. */
 void channel_replace_update(struct channel *channel, u8 *update TAKES);
 
+/* Tell channel about new feerates (owner must be channeld!) */
+void channel_update_feerates(struct lightningd *ld, const struct channel *channel);
 #endif /* LIGHTNING_LIGHTNINGD_CHANNEL_CONTROL_H */

lightningd/peer_control.c

@@ -2686,6 +2686,7 @@ static void set_channel_config(struct command *cmd, struct channel *channel,
 			       struct amount_msat *htlc_min,
 			       struct amount_msat *htlc_max,
 			       u32 delaysecs,
+			       bool *ignore_fee_limits,
 			       struct json_stream *response)
 {
 	bool warn_cannot_set_min = false, warn_cannot_set_max = false;
@@ -2733,12 +2734,18 @@ static void set_channel_config(struct command *cmd, struct channel *channel,
 		} else
 			channel->htlc_maximum_msat = *htlc_max;
 	}
+	if (ignore_fee_limits)
+		channel->ignore_fee_limits = *ignore_fee_limits;
 
 	/* tell channeld to make a send_channel_update */
-	if (channel->owner && streq(channel->owner->name, "channeld"))
+	if (channel->owner && streq(channel->owner->name, "channeld")) {
 		subd_send_msg(channel->owner,
 			      take(towire_channeld_config_channel(NULL, base, ppm,
 								  htlc_min, htlc_max)));
+		/* Tell it about the new acceptable feerates */
+		if (ignore_fee_limits)
+			channel_update_feerates(cmd->ld, channel);
+	}
 
 	/* save values to database */
 	wallet_channel_save(cmd->ld->wallet, channel);
@@ -2764,6 +2771,7 @@ static void set_channel_config(struct command *cmd, struct channel *channel,
 	json_add_amount_msat(response,
 			     "maximum_htlc_out_msat",
 			     channel->htlc_maximum_msat);
+	json_add_bool(response, "ignore_fee_limits", channel->ignore_fee_limits);
 	if (warn_cannot_set_max)
 		json_add_string(response, "warning_htlcmax_too_high",
 				"Set maximum_htlc_out_msat to maximum possible in channel");
@@ -2780,6 +2788,7 @@ static struct command_result *json_setchannel(struct command *cmd,
 	struct channel **channels;
 	u32 *base, *ppm, *delaysecs;
 	struct amount_msat *htlc_min, *htlc_max;
+	bool *ignore_fee_limits;
 
 	/* Parse the JSON command */
 	if (!param(cmd, buffer, params,
@@ -2789,6 +2798,7 @@ static struct command_result *json_setchannel(struct command *cmd,
 		   p_opt("htlcmin", param_msat, &htlc_min),
 		   p_opt("htlcmax", param_msat, &htlc_max),
 		   p_opt_def("enforcedelay", param_number, &delaysecs, 600),
+		   p_opt("ignorefeelimits", param_bool, &ignore_fee_limits),
 		   NULL))
 		return command_param_failed();
 
@@ -2818,7 +2828,8 @@ static struct command_result *json_setchannel(struct command *cmd,
 					continue;
 				set_channel_config(cmd, channel, base, ppm,
 						   htlc_min, htlc_max,
-						   *delaysecs, response);
+						   *delaysecs, ignore_fee_limits,
+						   response);
 			}
 		}
 	/* single peer should be updated */
@@ -2826,7 +2837,8 @@ static struct command_result *json_setchannel(struct command *cmd,
 		for (size_t i = 0; i < tal_count(channels); i++) {
 			set_channel_config(cmd, channels[i], base, ppm,
 					   htlc_min, htlc_max,
-					   *delaysecs, response);
+					   *delaysecs, ignore_fee_limits,
+					   response);
 		}
 	}
 

lightningd/test/run-invoice-select-inchan.c

@@ -124,6 +124,9 @@ const char **channel_type_name(const tal_t *ctx UNNEEDED, const struct channel_t
 /* Generated stub for channel_unsaved_close_conn */
 void channel_unsaved_close_conn(struct channel *channel UNNEEDED, const char *why UNNEEDED)
 { fprintf(stderr, "channel_unsaved_close_conn called!\n"); abort(); }
+/* Generated stub for channel_update_feerates */
+void channel_update_feerates(struct lightningd *ld UNNEEDED, const struct channel *channel UNNEEDED)
+{ fprintf(stderr, "channel_update_feerates called!\n"); abort(); }
 /* Generated stub for channel_update_reserve */
 void channel_update_reserve(struct channel *channel UNNEEDED,
 			    struct channel_config *their_config UNNEEDED,

wallet/test/run-wallet.c

@@ -81,6 +81,9 @@ bool channel_tell_depth(struct lightningd *ld UNNEEDED,
 /* Generated stub for channel_unsaved_close_conn */
 void channel_unsaved_close_conn(struct channel *channel UNNEEDED, const char *why UNNEEDED)
 { fprintf(stderr, "channel_unsaved_close_conn called!\n"); abort(); }
+/* Generated stub for channel_update_feerates */
+void channel_update_feerates(struct lightningd *ld UNNEEDED, const struct channel *channel UNNEEDED)
+{ fprintf(stderr, "channel_update_feerates called!\n"); abort(); }
 /* Generated stub for channel_update_reserve */
 void channel_update_reserve(struct channel *channel UNNEEDED,
 			    struct channel_config *their_config UNNEEDED,