ERROR: this is wrong

plugins/libplugin.c

@@ -10,6 +10,7 @@
 #include <common/daemon.h>
 #include <common/utils.h>
 #include <errno.h>
+#include <lightningd/lightningd.h>
 #include <poll.h>
 #include <plugins/libplugin.h>
 #include <stdarg.h>
@@ -53,6 +54,8 @@ static struct plugin_conn rpc_conn;
 struct command {
 	u64 id;
 	const char *methodname;
+	/* The global state */
+	struct lightningd *ld;
 	bool usage_only;
 };
 
@@ -87,6 +90,13 @@ struct command_result *command_param_failed(void)
 	return &complete;
 }
 
+/*~ Chainparams are the parameters for eg. testnet vs mainnet.  This wrapper
+ * saves lots of struggles with our 80-column guideline! */
+const struct chainparams *get_chainparams2(const struct command *cmd)
+{
+	return cmd->ld->topology->bitcoind->chainparams;
+}
+
 struct json_out *json_out_obj(const tal_t *ctx,
 			      const char *fieldname,
 			      const char *str)

plugins/libplugin.h

@@ -33,6 +33,8 @@ struct plugin_command {
 					 const jsmntok_t *params);
 };
 
+const struct chainparams *get_chainparams2(const struct command *cmd);
+
 /* Create an array of these, one for each --option you support. */
 struct plugin_option {
 	const char *name;

plugins/pay.c

@@ -1,3 +1,4 @@
+#include <bitcoin/chainparams.h>
 #include <ccan/array_size/array_size.h>
 #include <ccan/cast/cast.h>
 #include <ccan/intmap/intmap.h>
@@ -1043,6 +1044,10 @@ static struct command_result *json_pay(struct command *cmd,
 				    "Invalid bolt11: %s", fail);
 	}
 
+	if (b11->chain != get_chainparams2(cmd)) {
+		return command_fail(cmd, PAY_ROUTE_NOT_FOUND, "Invoice is for another network %s", b11->chain->network_name);
+	}
+
 	if (time_now().ts.tv_sec > b11->timestamp + b11->expiry) {
 		return command_fail(cmd, PAY_INVOICE_EXPIRED, "Invoice expired");
 	}