chaintopology: check bitcoin plugin commands at startup

Exit early if we won't be able to fully communicate with our Bitcoin
backend.

lightningd/bitcoind.c

@@ -7,10 +7,12 @@
 #include "bitcoind.h"
 #include "lightningd.h"
 #include "log.h"
+#include <ccan/array_size/array_size.h>
 #include <ccan/cast/cast.h>
 #include <ccan/io/io.h>
 #include <ccan/pipecmd/pipecmd.h>
 #include <ccan/str/hex/hex.h>
+#include <ccan/str/str.h>
 #include <ccan/take/take.h>
 #include <ccan/tal/grab_file/grab_file.h>
 #include <ccan/tal/path/path.h>
@@ -22,6 +24,7 @@
 #include <errno.h>
 #include <inttypes.h>
 #include <lightningd/chaintopology.h>
+#include <lightningd/plugin.h>
 
 /* Bitcoind's web server has a default of 4 threads, with queue depth 16.
  * It will *fail* rather than queue beyond that, so we must not stress it!
@@ -30,6 +33,26 @@
  */
 #define BITCOIND_MAX_PARALLEL 4
 
+/* The names of the request we can make to our Bitcoin backend. */
+static const char *methods[] = {"getchaininfo", "getrawblockbyheight",
+                                "sendrawtransaction", "getutxout",
+                                "getfeerate"};
+
+void bitcoind_check_commands(struct bitcoind *bitcoind)
+{
+	size_t i;
+	struct plugin *p;
+
+	for (i = 0; i < ARRAY_SIZE(methods); i++) {
+		p = find_plugin_for_command(bitcoind->ld, methods[i]);
+		if (p == NULL) {
+			fatal("Could not access the plugin for %s, is a "
+			      "Bitcoin plugin (by default plugins/bcli) "
+			      "registered ?", methods[i]);
+		}
+	}
+}
+
 /* Add the n'th arg to *args, incrementing n and keeping args of size n+1 */
 static void add_arg(const char ***args, const char *arg)
 {

lightningd/bitcoind.h

@@ -182,4 +182,6 @@ void bitcoind_gettxout(struct bitcoind *bitcoind,
 
 void bitcoind_getclientversion(struct bitcoind *bitcoind);
 
+void bitcoind_check_commands(struct bitcoind *bitcoind);
+
 #endif /* LIGHTNING_LIGHTNINGD_BITCOIND_H */

lightningd/chaintopology.c

@@ -955,6 +955,9 @@ void setup_topology(struct chain_topology *topo,
 	topo->min_blockheight = min_blockheight;
 	topo->max_blockheight = max_blockheight;
 
+	/* This waits for bitcoind. */
+	bitcoind_check_commands(topo->bitcoind);
+
 	/* Make sure bitcoind is started, and ready */
 	wait_for_bitcoind(topo->bitcoind);
 

lightningd/plugin.c

@@ -611,21 +611,21 @@ static void plugin_rpcmethod_cb(const char *buffer,
 	command_raw_complete(cmd, response);
 }
 
-static struct plugin *find_plugin_for_command(struct command *cmd)
+struct plugin *find_plugin_for_command(struct lightningd *ld,
+				       const char *cmd_name)
 {
-	struct plugins *plugins = cmd->ld->plugins;
+	struct plugins *plugins = ld->plugins;
 	struct plugin *plugin;
 
 	/* Find the plugin that registered this RPC call */
 	list_for_each(&plugins->plugins, plugin, list) {
 		for (size_t i=0; i<tal_count(plugin->methods); i++) {
-			if (streq(cmd->json_cmd->name, plugin->methods[i]))
+			if (streq(cmd_name, plugin->methods[i]))
 				return plugin;
 		}
 	}
-	/* This should never happen, it'd mean that a plugin didn't
-	 * cleanup after dying */
-	abort();
+
+	return NULL;
 }
 
 static struct command_result *plugin_rpcmethod_dispatch(struct command *cmd,
@@ -641,7 +641,9 @@ static struct command_result *plugin_rpcmethod_dispatch(struct command *cmd,
 	if (cmd->mode == CMD_CHECK)
 		return command_param_failed();
 
-	plugin = find_plugin_for_command(cmd);
+	plugin = find_plugin_for_command(cmd->ld, cmd->json_cmd->name);
+	if (!plugin)
+		fatal("No plugin for %s ?", cmd->json_cmd->name);
 
 	/* Find ID again (We've parsed them before, this should not fail!) */
 	idtok = json_get_member(buffer, toks, "id");

lightningd/plugin.h

@@ -180,6 +180,13 @@ bool plugin_remove(struct plugins *plugins, const char *name);
  */
 void plugin_kill(struct plugin *plugin, char *fmt, ...) PRINTF_FMT(2,3);
 
+/**
+ * Returns the plugin which registers the command with name {cmd_name}
+ */
+struct plugin *find_plugin_for_command(struct lightningd *ld,
+				       const char *cmd_name);
+
+
 /**
  * Send the configure message to all plugins.
  *