flexnbd: Make the killswitch runtime-selectable

We're not actually using it in production right now because it doesn't
shut its sockets down cleanly enough. This is a better option than
reverting the functionality or keeping production downgraded until
we sort out a handler that cleanly closes the sockets.

src/client.c

@@ -500,6 +500,10 @@ void client_arm_killswitch( struct client* client )
 		.it_interval = { .tv_nsec = 0, .tv_sec = 0 }
 	};
 
+	if ( !client->serve->use_killswitch ) {
+		return;
+	}
+
 	debug( "Arming killswitch" );
 
 	FATAL_IF_NEGATIVE(
@@ -517,6 +521,10 @@ void client_disarm_killswitch( struct client* client )
 		.it_interval = { .tv_nsec = 0, .tv_sec = 0 }
 	};
 
+	if ( !client->serve->use_killswitch ) {
+		return;
+	}
+
 	debug( "Disarming killswitch" );
 
 	FATAL_IF_NEGATIVE(

src/client.h

@@ -47,7 +47,9 @@ struct client {
 	/* Have we seen a REQUEST_DISCONNECT message? */
 	int     disconnect;
 
-	/* kill the whole server if a request has been outstanding too long */
+	/* kill the whole server if a request has been outstanding too long,
+	 * assuming use_killswitch is set in serve
+	 */
 	timer_t killswitch;
 
 };

src/flexnbd.c

@@ -86,7 +86,8 @@ struct flexnbd * flexnbd_create_serving(
 	int default_deny,
 	int acl_entries,
 	char** s_acl_entries,
-	int max_nbd_clients)
+	int max_nbd_clients,
+	int use_killswitch)
 {
 	struct flexnbd * flexnbd = xmalloc( sizeof( struct flexnbd ) );
 	flexnbd->serve = server_create(
@@ -98,6 +99,7 @@ struct flexnbd * flexnbd_create_serving(
 			acl_entries,
 			s_acl_entries,
 			max_nbd_clients,
+			use_killswitch,
 			1);
 	flexnbd_create_shared( flexnbd,
 			s_ctrl_sock );
@@ -123,7 +125,7 @@ struct flexnbd * flexnbd_create_listening(
 			default_deny,
 			acl_entries,
 			s_acl_entries,
-			1, 0);
+			1, 0, 0);
 	flexnbd_create_shared( flexnbd, s_ctrl_sock );
 	return flexnbd;
 }

src/flexnbd.h

@@ -36,7 +36,8 @@ struct flexnbd * flexnbd_create_serving(
 	int default_deny,
 	int acl_entries,
 	char** s_acl_entries,
-	int max_nbd_clients);
+	int max_nbd_clients,
+	int use_killswitch);
 
 struct flexnbd * flexnbd_create_listening(
 	char* s_ip_address,

src/mode.c

@@ -15,10 +15,11 @@ static struct option serve_options[] = {
 	GETOPT_SOCK,
 	GETOPT_DENY,
 	GETOPT_QUIET,
+	GETOPT_KILLSWITCH,
 	GETOPT_VERBOSE,
 	{0}
 };
-static char serve_short_options[] = "hl:p:f:s:d" SOPT_QUIET SOPT_VERBOSE;
+static char serve_short_options[] = "hl:p:f:s:dk" SOPT_QUIET SOPT_VERBOSE;
 static char serve_help_text[] =
 	"Usage: flexnbd " CMD_SERVE " <options> [<acl address>*]\n\n"
 	"Serve FILE from ADDR:PORT, with an optional control socket at SOCK.\n\n"
@@ -27,6 +28,7 @@ static char serve_help_text[] =
 	"\t--" OPT_PORT ",-p <PORT>\tThe port to serve on.\n"
 	"\t--" OPT_FILE ",-f <FILE>\tThe file to serve.\n"
 	"\t--" OPT_DENY ",-d\tDeny connections by default unless in ACL.\n"
+	"\t--" OPT_KILLSWITCH",-k  \tKill the server if a request takes 120 seconds.\n"
 	SOCK_LINE
 	VERBOSE_LINE
 	QUIET_LINE;
@@ -193,7 +195,7 @@ void do_write(struct mode_readwrite_params* params);
 void do_remote_command(char* command, char* mode, int argc, char** argv);
 
 
-void read_serve_param( int c, char **ip_addr, char **ip_port, char **file, char **sock, int *default_deny )
+void read_serve_param( int c, char **ip_addr, char **ip_port, char **file, char **sock, int *default_deny, int *use_killswitch )
 {
 	switch(c){
 		case 'h':
@@ -221,6 +223,9 @@ void read_serve_param( int c, char **ip_addr, char **ip_port, char **file, char
 		case 'v':
 			log_level = VERBOSE_LOG_LEVEL;
 			break;
+		case 'k':
+			*use_killswitch = 1;
+			break;
 		default:
 			exit_err( serve_help_text );
 			break;
@@ -404,6 +409,7 @@ int mode_serve( int argc, char *argv[] )
 	char *file    = NULL;
 	char *sock    = NULL;
 	int default_deny = 0; // not on by default
+	int use_killswitch = 0;
 	int err = 0;
 
 	int success;
@@ -414,7 +420,7 @@ int mode_serve( int argc, char *argv[] )
 		c = getopt_long(argc, argv, serve_short_options, serve_options, NULL);
 		if ( c == -1 ) { break; }
 
-		read_serve_param( c, &ip_addr, &ip_port, &file, &sock, &default_deny );
+		read_serve_param( c, &ip_addr, &ip_port, &file, &sock, &default_deny, &use_killswitch );
 	}
 
 	if ( NULL == ip_addr || NULL == ip_port ) {
@@ -427,7 +433,7 @@ int mode_serve( int argc, char *argv[] )
 	}
 	if ( err ) { exit_err( serve_help_text ); }
 
-	flexnbd = flexnbd_create_serving( ip_addr, ip_port, file, sock, default_deny, argc - optind, argv + optind, MAX_NBD_CLIENTS );
+	flexnbd = flexnbd_create_serving( ip_addr, ip_port, file, sock, default_deny, argc - optind, argv + optind, MAX_NBD_CLIENTS, use_killswitch );
 	info( "Serving file %s", file );
 	success = flexnbd_serve( flexnbd );
 	flexnbd_destroy( flexnbd );

src/mode.h

@@ -22,6 +22,7 @@ void mode(char* mode, int argc, char **argv);
 #define OPT_UNLINK "unlink"
 #define OPT_CONNECT_ADDR "conn-addr"
 #define OPT_CONNECT_PORT "conn-port"
+#define OPT_KILLSWITCH "killswitch"
 
 #define CMD_SERVE  "serve"
 #define CMD_LISTEN "listen"
@@ -52,6 +53,7 @@ void mode(char* mode, int argc, char **argv);
 #define GETOPT_UNLINK GETOPT_ARG( OPT_UNLINK, 'u' )
 #define GETOPT_CONNECT_ADDR GETOPT_ARG( OPT_CONNECT_ADDR, 'C' )
 #define GETOPT_CONNECT_PORT GETOPT_ARG( OPT_CONNECT_PORT, 'P' )
+#define GETOPT_KILLSWITCH   GETOPT_ARG( OPT_KILLSWITCH,   'k' )
 
 #define OPT_VERBOSE "verbose"
 #define SOPT_VERBOSE "v"

src/serve.c

@@ -30,6 +30,7 @@ struct server * server_create (
 	int acl_entries,
 	char** s_acl_entries,
 	int max_nbd_clients,
+	int use_killswitch,
 	int success)
 {
 	NULLCHECK( flexnbd );
@@ -38,8 +39,9 @@ struct server * server_create (
 	out->flexnbd = flexnbd;
 	out->success = success;
 	out->max_nbd_clients = max_nbd_clients;
-	out->nbd_client = xmalloc( max_nbd_clients * sizeof( struct client_tbl_entry ) );
+	out->use_killswitch = use_killswitch;
 
+	out->nbd_client = xmalloc( max_nbd_clients * sizeof( struct client_tbl_entry ) );
 	out->tcp_backlog = 10; /* does this need to be settable? */
 
 	FATAL_IF_NULL(s_ip_address, "No IP address supplied");

src/serve.h

@@ -87,6 +87,9 @@ struct server {
 	int                  max_nbd_clients;
 	struct client_tbl_entry *nbd_client;
 
+	/* Should clients use the killswitch? */
+	int use_killswitch;
+
 
 	/* Marker for whether this server has control over the data in
 	 * the file, or if we're waiting to receive it from an inbound
@@ -107,6 +110,7 @@ struct server * server_create(
 		int acl_entries,
 		char** s_acl_entries,
 		int max_nbd_clients,
+		int use_killswitch,
 		int success );
 void server_destroy( struct server * );
 int server_is_closed(struct server* serve);