criu: unify/improve bad argument messages

* Introduce a generic way to report that option argument is invalid
* Switch to using it from existing places
  (options --veth-pair, --port, -n)
* Check for invalid argument of -p and -t and report it.

Notes:

1) In order to correctly print long option name in case it was used
   instead of a short one, I had to move "struct option long_opts"
   to main() context, this is why the patch is so long.

2) pr_msg() (rather than pr_err()) is used to print errors, otherwise
   it is prefixed with that (crtools.c:123) prefix which makes it
   look weird.

3) Usage is not shown in case of error, otherwise an error message
   is lost in output.
Signed-off-by: Kir Kolyshkin <kir@openvz.org>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>

crtools.c

@@ -83,21 +83,6 @@ int main(int argc, char *argv[])
 	int log_level = 0;
 	char *imgs_dir = ".";
 	char *work_dir = NULL;
-
-	BUILD_BUG_ON(PAGE_SIZE != PAGE_IMAGE_SIZE);
-
-	cr_pb_init();
-	restrict_uid(getuid(), getgid());
-
-	if (argc < 2)
-		goto usage;
-
-	init_opts();
-
-	if (init_service_fd())
-		return 1;
-
-	while (1) {
 	static const char short_opts[] = "dsRf:F:t:p:hcD:o:n:v::xVr:jlW:L:";
 	static struct option long_opts[] = {
 		{ "tree", required_argument, 0, 't' },
@@ -138,6 +123,21 @@ int main(int argc, char *argv[])
 		{ },
 	};
 
+	BUILD_BUG_ON(PAGE_SIZE != PAGE_IMAGE_SIZE);
+
+	cr_pb_init();
+	restrict_uid(getuid(), getgid());
+
+	if (argc < 2)
+		goto usage;
+
+	init_opts();
+
+	if (init_service_fd())
+		return 1;
+
+	while (1) {
+		idx = -1;
 		opt = getopt_long(argc, argv, short_opts, long_opts, &idx);
 		if (opt == -1)
 			break;
@@ -154,9 +154,13 @@ int main(int argc, char *argv[])
 			break;
 		case 'p':
 			pid = atoi(optarg);
+			if (pid <= 0)
+				goto bad_arg;
 			break;
 		case 't':
 			tree_id = atoi(optarg);
+			if (tree_id <= 0)
+				goto bad_arg;
 			break;
 		case 'c':
 			opts.show_pages_content	= true;
@@ -184,7 +188,7 @@ int main(int argc, char *argv[])
 			break;
 		case 'n':
 			if (parse_ns_string(optarg))
-				return 1;
+				goto bad_arg;
 			break;
 		case 'v':
 			if (optarg) {
@@ -231,8 +235,7 @@ int main(int argc, char *argv[])
 				n->outside = strchr(optarg, '=');
 				if (n->outside == NULL) {
 					xfree(n);
-					pr_err("Invalid argument for --veth-pair\n");
-					goto usage;
+					goto bad_arg;
 				}
 
 				*n->outside++ = '\0';
@@ -260,10 +263,8 @@ int main(int argc, char *argv[])
 			break;
 		case 52:
 			opts.ps_port = htons(atoi(optarg));
-			if (!opts.ps_port) {
-				pr_err("Bad port\n");
-				return 1;
-			}
+			if (!opts.ps_port)
+				goto bad_arg;
 			break;
 		case 'j':
 			opts.shell_job = true;
@@ -469,4 +470,13 @@ usage:
 opt_pid_missing:
 	pr_msg("No pid specified (-t option missing)\n");
 	return 1;
+
+bad_arg:
+	if (idx < 0) /* short option */
+		pr_msg("Error: invalid argument for -%c: %s\n",
+				opt, optarg);
+	else /* long option */
+		pr_msg("Error: invalid argument for --%s: %s\n",
+				long_opts[idx].name, optarg);
+	return 1;
 }