crtools: add ability to set list of external resources

This option is used to mark external resources on dump.

Currently it's going to be used to handle external tty-s,
but in a future it can be used to any type of resources.

We can have a few ways to restore external resources and
we will have a separate options to say how to restore each type.

For example, we can use --inherit-fd to restore external
file descriptors.
Signed-off-by: Andrew Vagin <avagin@virtuozzo.com>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>

crtools.c

@@ -58,6 +58,7 @@ void init_opts(void)
 	INIT_LIST_HEAD(&opts.scripts);
 	INIT_LIST_HEAD(&opts.ext_mounts);
 	INIT_LIST_HEAD(&opts.inherit_fds);
+	INIT_LIST_HEAD(&opts.external);
 	INIT_LIST_HEAD(&opts.new_cgroup_roots);
 	INIT_LIST_HEAD(&opts.irmap_scan_paths);
 
@@ -257,6 +258,7 @@ int main(int argc, char *argv[], char *envp[])
 		{ "irmap-scan-path",		required_argument,	0, 1070 },
 		{ "lsm-profile",		required_argument,	0, 1071 },
 		{ "timeout",			required_argument,	0, 1072 },
+		{ "external",			required_argument,	0, 1073	},
 		{ },
 	};
 
@@ -523,6 +525,17 @@ int main(int argc, char *argv[], char *envp[])
 					return 1;
 			}
 			break;
+		case 1073:
+			{
+				struct external *ext;
+
+				ext = xmalloc(sizeof(*ext));
+				if (!ext)
+					return 1;
+				ext->id = optarg;
+				list_add(&ext->node, &opts.external);
+			}
+			break;
 		case 'V':
 			pr_msg("Version: %s\n", CRIU_VERSION);
 			if (strcmp(CRIU_GITID, "0"))
@@ -594,6 +607,11 @@ int main(int argc, char *argv[], char *envp[])
 	if (log_init(opts.output))
 		return 1;
 
+	if (!list_empty(&opts.external) && strcmp(argv[optind], "dump")) {
+		pr_err("--external is dump-only option\n");
+		return 1;
+	}
+
 	if (!list_empty(&opts.inherit_fds)) {
 		if (strcmp(argv[optind], "restore")) {
 			pr_err("--inherit-fd is restore-only option\n");
@@ -754,6 +772,7 @@ usage:
 "  --enable-fs FSNAMES   a comma separated list of filesystem names or \"all\".\n"
 "                        force criu to (try to) dump/restore these filesystem's\n"
 "                        mountpoints even if fs is not supported.\n"
+"  --external RES        dump objects from this list as external resources\n"
 "\n"
 "* Logging:\n"
 "  -o|--log-file FILE    log file name\n"

files.c

@@ -1575,3 +1575,13 @@ int inherit_fd_fini()
 	}
 	return 0;
 }
+
+bool external_lookup_id(char *id)
+{
+	struct external *ext;
+
+	list_for_each_entry(ext, &opts.external, node)
+		if (!strcmp(ext->id, id))
+			return true;
+	return false;
+}

include/cr_options.h

@@ -47,6 +47,11 @@ struct irmap_path_opt {
 	struct irmap *ir;
 };
 
+struct external {
+	struct list_head node;
+	char *id;
+};
+
 struct cr_options {
 	int			final_state;
 	char			*show_dump_file;
@@ -76,6 +81,7 @@ struct cr_options {
 	struct list_head	scripts;
 	struct list_head	ext_mounts;
 	struct list_head	inherit_fds;
+	struct list_head	external;
 	char			*libdir;
 	bool			use_page_server;
 	unsigned short		port;

include/files.h

@@ -175,6 +175,8 @@ extern void inherit_fd_log(void);
 extern int inherit_fd_resolve_clash(int fd);
 extern int inherit_fd_fini(void);
 
+extern bool external_lookup_id(char *id);
+
 extern bool inherited_fd(struct file_desc *, int *fdp);
 
 #endif /* __CR_FILES_H__ */