lightningd: setconfig command.

Currently only implemented for min-capacity-sat.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Changelog-Added: JSON-RPC: new command `setconfig` allows a limited number of configuration settings to be changed without restart.

doc/Makefile

@@ -89,6 +89,7 @@ MANPAGES := doc/lightning-cli.1 \
 	doc/lightning-sendonionmessage.7 \
 	doc/lightning-sendpay.7 \
 	doc/lightning-setchannel.7 \
+	doc/lightning-setconfig.7 \
 	doc/lightning-setpsbtversion.7 \
 	doc/lightning-sendcustommsg.7 \
 	doc/lightning-signinvoice.7 \

doc/index.rst

@@ -122,6 +122,7 @@ Core Lightning Documentation
    lightning-sendpay <lightning-sendpay.7.md>
    lightning-sendpsbt <lightning-sendpsbt.7.md>
    lightning-setchannel <lightning-setchannel.7.md>
+   lightning-setconfig <lightning-setconfig.7.md>
    lightning-setpsbtversion <lightning-setpsbtversion.7.md>
    lightning-signinvoice <lightning-signinvoice.7.md>
    lightning-signmessage <lightning-signmessage.7.md>

doc/lightning-setconfig.7.md

@@ -0,0 +1,59 @@
+lightning-setconfig -- Dynamically change some config options
+=============================================================
+
+SYNOPSIS
+--------
+
+**setconfig** *config* [*val*]
+
+DESCRIPTION
+-----------
+
+The **setconfig** RPC command allows you set the (dynamic) configuration option named by `config`: options which take a value (as separate from simple flag options) also need a `val` parameter.
+
+This new value will *also* be written at the end of the config file, for persistence across restarts.
+
+You can see what options are dynamically adjustable using lightning-listconfigs(7).  Note that you can also adjust existing options for stopped plugins; they will have an effect when the plugin is restarted.
+
+
+RETURN VALUE
+------------
+
+[comment]: # (GENERATE-FROM-SCHEMA-START)
+On success, an object containing **config** is returned.  It is an object containing:
+
+- **config** (string): name of the config variable which was set
+- **source** (string): source of configuration setting (`file`:`linenum`)
+- **dynamic** (boolean): whether this option is settable via setconfig (always *true*)
+- **plugin** (string, optional): the plugin this configuration setting is for
+- **set** (boolean, optional): for simple flag options
+- **value\_str** (string, optional): for string options
+- **value\_msat** (msat, optional): for msat options
+- **value\_int** (integer, optional): for integer options
+- **value\_bool** (boolean, optional): for boolean options
+
+[comment]: # (GENERATE-FROM-SCHEMA-END)
+
+ERRORS
+------
+
+The following error codes may occur:
+- -32602: JSONRPC2\_INVALID\_PARAMS, i.e. the parameter is not dynamic, or the val was invalid.
+
+AUTHOR
+------
+
+Rusty Russell <<rusty@rustcorp.com.au>> is mainly responsible for this
+feature.
+
+SEE ALSO
+--------
+
+lightningd-config(5), lightning-listconfigs(7)
+
+RESOURCES
+---------
+
+Main web site: <https://github.com/ElementsProject/lightning>
+
+[comment]: # ( SHA256STAMP:d61e4e6eea7b8c214644334ee194b273aef2a8a26465adfcd685be0d70653966)

doc/lightningd-config.5.md

@@ -14,6 +14,8 @@ file (default: **$HOME/.lightning/config**) then a network-specific
 configuration file (default: **$HOME/.lightning/testnet/config**).  This can
 be changed: see *--conf* and *--lightning-dir*.
 
+Note that some configuration options, marked *dynamic*m can be changed at runtime: see lightning-setconfig(7).
+
 General configuration files are processed first, then network-specific
 ones, then command line options: later options override earlier ones
 except *addr* options and *log-level* with subsystems, which
@@ -316,7 +318,7 @@ millionths, so 10000 is 1%, 1000 is 0.1%. Changing this value will only
 affect new channels and not existing ones. If you want to change fees
 for existing channels, use the RPC call lightning-setchannel(7).
 
-* **min-capacity-sat**=*SATOSHI*
+* **min-capacity-sat**=*SATOSHI* [*dynamic*]
 
   Default: 10000. This value defines the minimal effective channel
 capacity in satoshi to accept for channel opening requests. This will

doc/schemas/setconfig.request.json

@@ -0,0 +1,15 @@
+{
+  "$schema": "http://json-schema.org/draft-07/schema#",
+  "type": "object",
+  "additionalProperties": false,
+  "required": [
+    "config"
+  ],
+  "added": "v23.08",
+  "properties": {
+    "config": {
+      "type": "string"
+    },
+    "val": {}
+  }
+}

doc/schemas/setconfig.schema.json

@@ -0,0 +1,62 @@
+{
+  "$schema": "http://json-schema.org/draft-07/schema#",
+  "type": "object",
+  "additionalProperties": false,
+  "added": "v23.08",
+  "required": [
+    "config"
+  ],
+  "properties": {
+    "config": {
+      "type": "object",
+      "description": "config settings after completion",
+      "additionalProperties": false,
+      "required": [
+        "config",
+        "source",
+        "dynamic"
+      ],
+      "properties": {
+        "config": {
+          "type": "string",
+          "description": "name of the config variable which was set"
+        },
+        "source": {
+          "type": "string",
+          "description": "source of configuration setting (`file`:`linenum`)"
+        },
+        "plugin": {
+          "type": "string",
+          "description": "the plugin this configuration setting is for"
+        },
+        "dynamic": {
+          "type": "boolean",
+          "enum": [
+            true
+          ],
+          "description": "whether this option is settable via setconfig"
+        },
+        "set": {
+          "type": "boolean",
+          "description": "for simple flag options"
+        },
+        "value_str": {
+          "type": "string",
+          "description": "for string options"
+        },
+        "value_msat": {
+          "type": "msat",
+          "description": "for msat options"
+        },
+        "value_int": {
+          "type": "integer",
+          "description": "for integer options"
+        },
+        "value_bool": {
+          "type": "boolean",
+          "description": "for boolean options"
+        }
+      }
+    }
+  }
+}

lightningd/configs.c

@@ -2,15 +2,20 @@
 #include <ccan/err/err.h>
 #include <ccan/opt/opt.h>
 #include <ccan/opt/private.h>
+#include <ccan/tal/grab_file/grab_file.h>
+#include <ccan/tal/path/path.h>
 #include <ccan/tal/str/str.h>
 #include <common/configdir.h>
 #include <common/configvar.h>
 #include <common/json_command.h>
 #include <common/json_param.h>
 #include <common/version.h>
+#include <errno.h>
+#include <fcntl.h>
 #include <lightningd/jsonrpc.h>
 #include <lightningd/options.h>
 #include <lightningd/plugin.h>
+#include <unistd.h>
 
 static void json_add_source(struct json_stream *result,
 			    const char *fieldname,
@@ -113,10 +118,14 @@ static void json_add_configval(struct json_stream *result,
 }
 
 /* Config vars can have multiple names ("--large-channels|--wumbo"), but first
- * is preferred */
+ * is preferred.
+ * wrap_object means we wrap json in an object of that name, otherwise outputs
+ * raw fields.
+ */
 static void json_add_config(struct lightningd *ld,
 			    struct json_stream *response,
 			    bool always_include,
+			    bool wrap_object,
 			    const struct opt_table *ot,
 			    const char **names)
 {
@@ -139,19 +148,22 @@ static void json_add_config(struct lightningd *ld,
 		return;
 
 	if (ot->type & OPT_NOARG) {
-		json_object_start(response, names[0]);
+		if (wrap_object)
+			json_object_start(response, names[0]);
 		json_add_bool(response, "set", cv != NULL);
 		json_add_source(response, "source", cv);
 		json_add_config_plugin(response, ld->plugins, "plugin", ot);
 		if (ot->type & OPT_DYNAMIC)
 			json_add_bool(response, "dynamic", true);
-		json_object_end(response);
+		if (wrap_object)
+			json_object_end(response);
 		return;
 	}
 
 	assert(ot->type & OPT_HASARG);
 	if (ot->type & OPT_MULTI) {
-		json_object_start(response, names[0]);
+		if (wrap_object)
+			json_object_start(response, names[0]);
 		json_array_start(response, configval_fieldname(ot));
 		while (cv) {
 			val = get_opt_val(ot, buf, cv);
@@ -171,7 +183,8 @@ static void json_add_config(struct lightningd *ld,
 		json_add_config_plugin(response, ld->plugins, "plugin", ot);
 		if (ot->type & OPT_DYNAMIC)
 			json_add_bool(response, "dynamic", true);
-		json_object_end(response);
+		if (wrap_object)
+			json_object_end(response);
 		return;
 	}
 
@@ -180,13 +193,15 @@ static void json_add_config(struct lightningd *ld,
 	if (!val)
 		return;
 
-	json_object_start(response, names[0]);
+	if (wrap_object)
+		json_object_start(response, names[0]);
 	json_add_configval(response, configval_fieldname(ot), ot, val);
 	json_add_source(response, "source", cv);
 	json_add_config_plugin(response, ld->plugins, "plugin", ot);
 	if (ot->type & OPT_DYNAMIC)
 		json_add_bool(response, "dynamic", true);
-	json_object_end(response);
+	if (wrap_object)
+		json_object_end(response);
 }
 
 static struct command_result *param_opt_config(struct command *cmd,
@@ -292,7 +307,7 @@ modern:
 		}
 		/* We don't usually print dev or deprecated options, unless
 		 * they explicitly ask, or they're set. */
-		json_add_config(cmd->ld, response, config != NULL,
+		json_add_config(cmd->ld, response, config != NULL, true,
 				&opt_table[i], names);
 	}
 	json_object_end(response);
@@ -311,3 +326,172 @@ static const struct json_command listconfigs_command = {
 	"With [config], object only has that field"
 };
 AUTODATA(json_command, &listconfigs_command);
+
+static struct command_result *param_opt_dynamic_config(struct command *cmd,
+						       const char *name,
+						       const char *buffer,
+						       const jsmntok_t *tok,
+						       const struct opt_table **config)
+{
+	struct command_result *ret;
+
+	ret = param_opt_config(cmd, name, buffer, tok, config);
+	if (ret)
+		return ret;
+
+	if (!((*config)->type & OPT_DYNAMIC))
+		return command_fail_badparam(cmd, name, buffer, tok,
+					     "Not a dynamic config option");
+	return NULL;
+}
+
+/* FIXME: put in ccan/mem! */
+static size_t memcount(const void *mem, size_t len, char c)
+{
+	size_t count = 0;
+	for (size_t i = 0; i < len; i++) {
+		if (((char *)mem)[i] == c)
+			count++;
+	}
+	return count;
+}
+
+static void configvar_append_file(struct lightningd *ld,
+				  const char *fname,
+				  enum configvar_src src,
+				  const char *confline,
+				  bool must_exist)
+{
+	int fd;
+	size_t num_lines;
+	const char *buffer, *insert;
+	bool needs_term;
+	struct configvar *cv;
+	time_t now = time(NULL);
+
+	fd = open(fname, O_RDWR|O_APPEND);
+	if (fd < 0) {
+		if (errno != ENOENT || must_exist)
+			fatal("Could not write to config %s: %s",
+			      fname, strerror(errno));
+		fd = open(fname, O_RDWR|O_APPEND|O_CREAT, 0644);
+		if (fd < 0)
+			fatal("Could not create config file %s: %s",
+			      fname, strerror(errno));
+	}
+
+	/* Note: always nul terminates */
+	buffer = grab_fd(tmpctx, fd);
+	if (!buffer)
+		fatal("Error reading %s: %s", fname, strerror(errno));
+
+	num_lines = memcount(buffer, tal_bytelen(buffer)-1, '\n');
+
+	/* If there's a last character and it's not \n, add one */
+	if (tal_bytelen(buffer) == 1)
+		needs_term = false;
+	else
+		needs_term = (buffer[tal_bytelen(buffer)-2] != '\n');
+
+	/* Note: ctime() contains a \n! */
+	insert = tal_fmt(tmpctx, "%s# Inserted by setconfig %s%s\n",
+			 needs_term ? "\n": "",
+			 ctime(&now), confline);
+	if (write(fd, insert, strlen(insert)) != strlen(insert))
+		fatal("Could not write to config file %s: %s",
+		      fname, strerror(errno));
+
+	cv = configvar_new(ld->configvars, src, fname, num_lines+2, confline);
+	configvar_unparsed(cv);
+
+	log_info(ld->log, "setconfig: %s %s (updated %s:%u)",
+		 cv->optvar, cv->optarg ? cv->optarg : "SET",
+		 cv->file, cv->linenum);
+
+	tal_arr_expand(&ld->configvars, cv);
+	configvar_finalize_overrides(ld->configvars);
+}
+
+static void configvar_save(struct lightningd *ld, const char *confline)
+{
+	/* If they used --conf then append to that */
+	if (ld->config_filename)
+		configvar_append_file(ld,
+				      ld->config_filename,
+				      CONFIGVAR_EXPLICIT_CONF,
+				      confline, true);
+	else {
+		const char *fname;
+
+		fname = path_join(tmpctx, ld->config_netdir, "config");
+		configvar_append_file(ld,
+				      fname,
+				      CONFIGVAR_NETWORK_CONF,
+				      confline,
+				      false);
+	}
+}
+
+static struct command_result *json_setconfig(struct command *cmd,
+					     const char *buffer,
+					     const jsmntok_t *obj UNNEEDED,
+					     const jsmntok_t *params)
+{
+	struct json_stream *response;
+	const struct opt_table *ot;
+	const char *val, **names, *confline;
+	unsigned int len;
+	char *err;
+
+	if (!param(cmd, buffer, params,
+		   p_req("config", param_opt_dynamic_config, &ot),
+		   p_opt("val", param_string, &val),
+		   NULL))
+		return command_param_failed();
+
+	/* We don't handle DYNAMIC MULTI, at least yet! */
+	assert(!(ot->type & OPT_MULTI));
+
+	names = tal_arr(tmpctx, const char *, 1);
+	/* This includes leading -! */
+	names[0] = first_name(ot->names, &len) + 1;
+
+	if (ot->type & OPT_NOARG) {
+		if (val)
+			return command_fail(cmd, JSONRPC2_INVALID_PARAMS,
+					    "%s does not take a value",
+					    ot->names + 2);
+		confline = tal_strdup(tmpctx, names[0]);
+		err = ot->cb(ot->u.arg);
+	} else {
+		assert(ot->type & OPT_HASARG);
+		if (!val)
+			return command_fail(cmd, JSONRPC2_INVALID_PARAMS,
+					    "%s requires a value",
+					    ot->names + 2);
+		confline = tal_fmt(tmpctx, "%s=%s", names[0], val);
+		err = ot->cb_arg(val, ot->u.arg);
+	}
+
+	if (err) {
+		return command_fail(cmd, JSONRPC2_INVALID_PARAMS,
+				    "Error setting %s: %s", ot->names + 2, err);
+	}
+
+	configvar_save(cmd->ld, confline);
+
+	response = json_stream_success(cmd);
+	json_object_start(response, "config");
+	json_add_string(response, "config", names[0]);
+	json_add_config(cmd->ld, response, true, false, ot, names);
+	json_object_end(response);
+	return command_success(cmd, response);
+}
+
+static const struct json_command setconfig_command = {
+	"setconfig",
+	"utility",
+	json_setconfig,
+	"Set a dynamically-adjustable config."
+};
+AUTODATA(json_command, &setconfig_command);

tests/test_misc.py

@@ -3396,3 +3396,57 @@ def test_fast_shutdown(node_factory):
         except ConnectionRefusedError:
             continue
         break
+
+
+def test_setconfig(node_factory):
+    l1, l2 = node_factory.line_graph(2, fundchannel=False)
+    configfile = os.path.join(l2.daemon.opts.get("lightning-dir"), TEST_NETWORK, 'config')
+
+    assert (l2.rpc.listconfigs('min-capacity-sat')['configs']
+            == {'min-capacity-sat':
+                {'source': 'default',
+                 'value_int': 10000,
+                 'dynamic': True}})
+
+    with pytest.raises(RpcError, match='requires a value'):
+        l2.rpc.setconfig('min-capacity-sat')
+
+    with pytest.raises(RpcError, match='requires a value'):
+        l2.rpc.setconfig(config='min-capacity-sat')
+
+    with pytest.raises(RpcError, match='is not a number'):
+        l2.rpc.setconfig(config='min-capacity-sat', val="abcd")
+
+    ret = l2.rpc.setconfig(config='min-capacity-sat', val=500000)
+    assert ret == {'config':
+                   {'config': 'min-capacity-sat',
+                    'source': '{}:2'.format(configfile),
+                    'value_int': 500000,
+                    'dynamic': True}}
+
+    with open(configfile, 'r') as f:
+        lines = f.read().splitlines()
+        assert lines[0].startswith('# Inserted by setconfig ')
+        assert lines[1] == 'min-capacity-sat=500000'
+        assert len(lines) == 2
+
+    # Now we need to meet minumum
+    with pytest.raises(RpcError, match='which is below 500000sat'):
+        l1.fundchannel(l2, 400000)
+
+    l1.fundchannel(l2, 10**6)
+    l1.rpc.close(l2.info['id'])
+
+    # It's persistent!
+    l2.restart()
+
+    assert (l2.rpc.listconfigs('min-capacity-sat')['configs']
+            == {'min-capacity-sat':
+                {'source': '{}:2'.format(configfile),
+                 'value_int': 500000,
+                 'dynamic': True}})
+
+    # Still need to meet minumum
+    l1.connect(l2)
+    with pytest.raises(RpcError, match='which is below 500000sat'):
+        l1.fundchannel(l2, 400000)