plugin: Tell the plugin which network we run on

The fundchannel plugin needs to know how to build a transaction, so we need to
tell it which chainparams to use. Also adds `chainparams` as a global, since
that seems to be the way to do things in plugins.

lightningd/plugin.c

@@ -1049,6 +1049,9 @@ plugin_populate_init_request(struct plugin *plugin, struct jsonrpc_request *req)
 	json_add_string(req->stream, "lightning-dir", ld->config_dir);
 	json_add_string(req->stream, "rpc-file", ld->rpc_filename);
 	json_add_bool(req->stream, "startup", plugin->plugins->startup);
+	json_add_string(
+	    req->stream, "network",
+	    plugin->plugins->ld->topology->bitcoind->chainparams->network_name);
 	json_object_end(req->stream);
 }
 

plugins/fundchannel.c

@@ -12,7 +12,9 @@
 
 const char *placeholder_script = "0020b95810f824f843934fa042acd0becba52087813e260edaeebc42b5cb9abe1464";
 const char *placeholder_funding_addr;
-const struct amount_sat *max_funding;
+
+/* Populated by libplugin */
+extern const struct chainparams *chainparams;
 
 struct funding_req {
 	struct node_id *id;
@@ -333,7 +335,7 @@ static struct command_result *tx_prepare_dryrun(struct command *cmd,
 						const jsmntok_t *result,
 						struct funding_req *fr)
 {
-	const struct bitcoin_tx *tx;
+	struct bitcoin_tx *tx;
 	const char *hex;
 	struct amount_sat funding;
 	bool funding_found;
@@ -347,6 +349,7 @@ static struct command_result *tx_prepare_dryrun(struct command *cmd,
 
 	hex = json_strdup(tmpctx, buf, json_get_member(buf, result, "unsigned_tx"));
 	tx = bitcoin_tx_from_hex(fr, hex, strlen(hex));
+	tx->chainparams = chainparams;
 
 	/* Find the funding amount */
 	funding_found = false;
@@ -363,8 +366,8 @@ static struct command_result *tx_prepare_dryrun(struct command *cmd,
 		plugin_err("Error creating placebo funding tx, funding_out not found. %s", hex);
 
 	/* Update funding to actual amount */
-	if (fr->funding_all && amount_sat_greater(funding, *max_funding))
-		funding = *max_funding;
+	if (fr->funding_all && amount_sat_greater(funding, chainparams->max_funding))
+		funding = chainparams->max_funding;
 
 	fr->funding_str = type_to_string(fr, struct amount_sat, &funding);
 	return fundchannel_start(cmd, fr);
@@ -404,7 +407,6 @@ static void init(struct plugin_conn *rpc,
 {
 	/* Figure out what the 'placeholder' addr is */
 	const char *network_name;
-	const struct chainparams *chainparams;
 	u8 *placeholder = tal_hexdata(tmpctx, placeholder_script, strlen(placeholder_script));
 
 	network_name = rpc_delve(tmpctx, "listconfigs",
@@ -415,7 +417,6 @@ static void init(struct plugin_conn *rpc,
 	placeholder_funding_addr = encode_scriptpubkey_to_addr(NULL,
 							       chainparams->bip173_name,
 							       placeholder);
-	max_funding = &chainparams->max_funding;
 }
 
 

plugins/libplugin.c

@@ -1,3 +1,4 @@
+#include <bitcoin/chainparams.h>
 #include <ccan/err/err.h>
 #include <ccan/intmap/intmap.h>
 #include <ccan/json_out/json_out.h>
@@ -34,6 +35,8 @@ static size_t in_timer;
 
 bool deprecated_apis;
 
+const struct chainparams *chainparams;
+
 struct plugin_timer {
 	struct timer timer;
 	struct command_result *(*cb)(void);
@@ -523,10 +526,10 @@ static struct command_result *handle_init(struct command *init_cmd,
 					  void (*init)(struct plugin_conn *,
 						       const char *buf, const jsmntok_t *))
 {
-	const jsmntok_t *configtok, *rpctok, *dirtok, *opttok, *t;
+	const jsmntok_t *configtok, *rpctok, *dirtok, *opttok, *nettok, *t;
 	struct sockaddr_un addr;
 	size_t i;
-	char *dir;
+	char *dir, *network;
 	struct json_out *param_obj;
 
 	configtok = json_delve(buf, params, ".configuration");
@@ -537,6 +540,11 @@ static struct command_result *handle_init(struct command *init_cmd,
 	if (chdir(dir) != 0)
 		plugin_err("chdir to %s: %s", dir, strerror(errno));
 
+	nettok = json_delve(buf, configtok, ".network");
+	network = json_strdup(tmpctx, buf, nettok);
+	chainparams = chainparams_for_network(network);
+	is_elements = chainparams->is_elements;
+
 	rpctok = json_delve(buf, configtok, ".rpc-file");
 	rpc_conn.fd = socket(AF_UNIX, SOCK_STREAM, 0);
 	if (rpctok->end - rpctok->start + 1 > sizeof(addr.sun_path))