options: create enable/disable option for peer storage.

Since it's not spec-final yet (hell, it's not even properly specified
yet!) we need to put it behind an experimental flag.

Unfortunately, we don't have support for doing this in a plugin; a
plugin must present features before parsing options.  So we need to do
it in core.

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

doc/lightning-listconfigs.7.md

@@ -62,6 +62,7 @@ On success, an object is returned, containing:
 - **experimental-offers** (boolean, optional): `experimental-offers` field from config or cmdline, or default
 - **experimental-shutdown-wrong-funding** (boolean, optional): `experimental-shutdown-wrong-funding` field from config or cmdline, or default
 - **experimental-websocket-port** (u16, optional): `experimental-websocket-port` field from config or cmdline, or default
+- **experimental-peer-storage** (boolean, optional): `experimental-peer-storage` field from config or cmdline, or default *(added v23.02)*
 - **database-upgrade** (boolean, optional): `database-upgrade` field from config or cmdline
 - **rgb** (hex, optional): `rgb` field from config or cmdline, or default (always 6 characters)
 - **alias** (string, optional): `alias` field from config or cmdline, or default
@@ -223,4 +224,4 @@ RESOURCES
 
 Main web site: <https://github.com/ElementsProject/lightning>
 
-[comment]: # ( SHA256STAMP:581225b26efd84bfa99dc98e7a91e6fae11ef0b11939031d3da07f751f6d8f87)
+[comment]: # ( SHA256STAMP:1088401b9aeae1e079dab550d3b035ef82195f0466ad471bc7373386182f37dc)

doc/lightningd-config.5.md

@@ -714,6 +714,12 @@ connections on that port, on any IPv4 and IPv6 addresses you listen
 to ([bolt][bolt] #891).  The normal protocol is expected to be sent over WebSocket binary
 frames once the connection is upgraded.
 
+* **experimental-peer-storage**
+
+  Specifying this option means we will store up to 64k of encrypted
+data for our peers, and give them our (encrypted!) backup data to
+store as well, based on a protocol similar to [bolt][bolt] #881.
+
 BUGS
 ----
 

doc/schemas/listconfigs.schema.json

@@ -137,6 +137,11 @@
       "type": "u16",
       "description": "`experimental-websocket-port` field from config or cmdline, or default"
     },
+    "experimental-peer-storage": {
+      "type": "boolean",
+      "added": "v23.02",
+      "description": "`experimental-peer-storage` field from config or cmdline, or default"
+    },
     "database-upgrade": {
       "type": "boolean",
       "description": "`database-upgrade` field from config or cmdline"

lightningd/options.c

@@ -1078,6 +1078,15 @@ static char *opt_set_shutdown_wrong_funding(struct lightningd *ld)
 	return NULL;
 }
 
+static char *opt_set_peer_storage(struct lightningd *ld)
+{
+	feature_set_or(ld->our_features,
+		       take(feature_set_for_feature(NULL, OPT_PROVIDE_PEER_BACKUP_STORAGE)));
+	feature_set_or(ld->our_features,
+		       take(feature_set_for_feature(NULL, OPT_WANT_PEER_BACKUP_STORAGE)));
+	return NULL;
+}
+
 static char *opt_set_offers(struct lightningd *ld)
 {
 	ld->config.exp_offers = true;
@@ -1156,6 +1165,9 @@ static void register_opts(struct lightningd *ld)
 	opt_register_early_noarg("--experimental-shutdown-wrong-funding",
 				 opt_set_shutdown_wrong_funding, ld,
 				 "EXPERIMENTAL: allow shutdown with alternate txids");
+	opt_register_early_noarg("--experimental-peer-storage",
+				 opt_set_peer_storage, ld,
+				 "EXPERIMENTAL: enable peer backup storage and restore");
 	opt_register_early_arg("--announce-addr-dns",
 			       opt_set_bool_arg, opt_show_bool,
 			       &ld->announce_dns,
@@ -1641,6 +1653,11 @@ static void add_config(struct lightningd *ld,
 				      feature_offered(ld->our_features
 						      ->bits[INIT_FEATURE],
 						      OPT_SHUTDOWN_WRONG_FUNDING));
+		} else if (opt->cb == (void *)opt_set_peer_storage) {
+			json_add_bool(response, name0,
+				      feature_offered(ld->our_features
+						      ->bits[INIT_FEATURE],
+						      OPT_PROVIDE_PEER_BACKUP_STORAGE));
 		} else if (opt->cb == (void *)plugin_opt_flag_set) {
 			/* Noop, they will get added below along with the
 			 * OPT_HASARG options. */

plugins/chanbackup.c

@@ -30,6 +30,7 @@
 
 /* Global secret object to keep the derived encryption key for the SCB */
 static struct secret secret;
+static bool peer_backup;
 
 /* Helper to fetch out SCB from the RPC call */
 static bool json_to_scb_chan(const char *buffer,
@@ -530,6 +531,9 @@ static struct command_result *peer_connected(struct command *cmd,
         u8 *serialise_scb;
 	const char *err;
 
+	if (!peer_backup)
+		return command_hook_success(cmd);
+
 	serialise_scb = towire_peer_storage(cmd,
 					    get_file_data(tmpctx, cmd->plugin));
 	node_id = tal(cmd, struct node_id);
@@ -592,13 +596,15 @@ static struct command_result *handle_your_peer_storage(struct command *cmd,
 {
         struct node_id node_id;
         u8 *payload, *payload_deserialise;
-	const char *err = json_scan(cmd, buf, params,
+	const char *err;
-				    "{payload:%,peer_id:%}",
+
-				    JSON_SCAN_TAL(cmd,
+	if (!peer_backup)
-				    		  json_tok_bin_from_hex,
+		return command_hook_success(cmd);
-				    		  &payload),
+
-				    JSON_SCAN(json_to_node_id,
+	err = json_scan(cmd, buf, params,
-				    	      &node_id));
+			"{payload:%,peer_id:%}",
+			JSON_SCAN_TAL(cmd, json_tok_bin_from_hex, &payload),
+			JSON_SCAN(json_to_node_id, &node_id));
 	if (err) {
 		plugin_err(cmd->plugin,
 			   "`your_peer_storage` response did not scan %s: %.*s",
@@ -737,6 +743,14 @@ static const char *init(struct plugin *p,
 	struct scb_chan **scb_chan;
 	const char *info = "scb secret";
 	u8 *info_hex = tal_dup_arr(tmpctx, u8, (u8*)info, strlen(info), 0);
+	u8 *features;
+
+	/* Figure out if they specified --experimental-peer-storage */
+	rpc_scan(p, "getinfo",
+		 take(json_out_obj(NULL, NULL, NULL)),
+		 "{our_features:{init:%}}",
+		 JSON_SCAN_TAL(tmpctx, json_tok_bin_from_hex, &features));
+	peer_backup = feature_offered(features, OPT_WANT_PEER_BACKUP_STORAGE);
 
 	rpc_scan(p, "staticbackup",
 		 take(json_out_obj(NULL, NULL, NULL)),
@@ -799,12 +813,8 @@ static const struct plugin_command commands[] = {
 int main(int argc, char *argv[])
 {
         setup_locale();
-	struct feature_set *features = feature_set_for_feature(NULL, OPT_WANT_PEER_BACKUP_STORAGE);
-	feature_set_or(features,
-		       take(feature_set_for_feature(NULL,
-						    OPT_PROVIDE_PEER_BACKUP_STORAGE)));
 
-	plugin_main(argv, init, PLUGIN_STATIC, true, features,
+	plugin_main(argv, init, PLUGIN_STATIC, true, NULL,
 		    commands, ARRAY_SIZE(commands),
 		    notifs, ARRAY_SIZE(notifs), hooks, ARRAY_SIZE(hooks),
 		    NULL, 0,  /* Notification topics we publish */

tests/test_misc.py

@@ -2510,8 +2510,11 @@ def test_restorefrompeer(node_factory, bitcoind):
     """
     Test restorefrompeer
     """
-    l1, l2 = node_factory.get_nodes(2, opts=[{'allow_broken_log': True, 'may_reconnect': True},
+    l1, l2 = node_factory.get_nodes(2, [{'allow_broken_log': True,
-                                             {'may_reconnect': True}])
+                                         'experimental-peer-storage': None,
+                                         'may_reconnect': True},
+                                        {'experimental-peer-storage': None,
+                                         'may_reconnect': True}])
 
     l1.rpc.connect(l2.info['id'], 'localhost', l2.port)