tools: replace non-standard namespace identifiers

The identifiers for namespaces used with lxc-unshare and lxc-attach as given on
the manpage do not align with the standard identifiers. This affects network,
mount, and uts namespaces. The standard identifiers are: "mnt", "uts", and
"net" whereas lxc-unshare and lxc-attach use "MOUNT", "UTSNAME", and "NETWORK".
I'm weary to hack this into namespace.{c.h} by e.g. adding additional members
to the ns_info struct or to special case this in lxc_fill_namespace_flags().
Internally, we should only accept standard identifiers to ensure that we are
always correctly aligned with the kernel. So let's use some cheap memmove()s to
replace them by their standard identifiers in lxc-unshare and lxc-attach.

Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>

src/lxc/tools/lxc_attach.c

@@ -107,6 +107,8 @@ static int add_to_simple_array(char ***array, ssize_t *capacity, char *value)
 
 static int my_parser(struct lxc_arguments* args, int c, char* arg)
 {
+	char **it;
+	char *del;
 	int ret;
 
 	switch (c) {
@@ -125,6 +127,30 @@ static int my_parser(struct lxc_arguments* args, int c, char* arg)
 		break;
 	case 's':
 		namespace_flags = 0;
+
+		/* The identifiers for namespaces used with lxc-attach as given
+		 * on the manpage do not align with the standard identifiers.
+		 * This affects network, mount, and uts namespaces. The standard
+		 * identifiers are: "mnt", "uts", and "net" whereas lxc-attach
+		 * uses "MOUNT", "UTSNAME", and "NETWORK". So let's use some
+		 * cheap memmove()s to replace them by their standard
+		 * identifiers. Let's illustrate this with an example:
+		 * Assume the string:
+		 *
+		 *	"IPC|MOUNT|PID"
+		 *
+		 * then we memmove()
+		 *
+		 *	dest: del + 1 == ONT|PID
+		 *	src:  del + 3 == NT|PID
+		 */
+		while ((del = strstr(arg, "MOUNT")))
+			memmove(del + 1, del + 3, strlen(del) - 2);
+
+		for (it = (char *[]){"NETWORK", "UTSNAME", NULL}; it && *it; it++)
+			while ((del = strstr(arg, *it)))
+				memmove(del + 3, del + 7, strlen(del) - 6);
+
 		ret = lxc_fill_namespace_flags(arg, &namespace_flags);
 		if (ret)
 			return -1;

src/lxc/tools/lxc_unshare.c

@@ -76,7 +76,7 @@ static void usage(char *cmd)
 	fprintf(stderr, "\t -i <iface>   : Interface name to be moved into container (presumably with NETWORK unsharing set)\n");
 	fprintf(stderr, "\t -H <hostname>: Set the hostname in the container\n");
 	fprintf(stderr, "\t -d           : Daemonize (do not wait for container to exit)\n");
-	fprintf(stderr, "\t -M           : reMount default fs inside container (/proc /dev/shm /dev/mqueue)\n");
+	fprintf(stderr, "\t -M           : Remount default fs inside container (/proc /dev/shm /dev/mqueue)\n");
 	_exit(EXIT_SUCCESS);
 }
 
@@ -151,12 +151,12 @@ static int do_start(void *arg)
 
 int main(int argc, char *argv[])
 {
+	char *del;
+	char **it, **args;
 	int opt, status;
 	int ret;
 	char *namespaces = NULL;
-	char **args;
-	int flags = 0;
-	int daemonize = 0;
+	int flags = 0, daemonize = 0;
 	uid_t uid = 0; /* valid only if (flags & CLONE_NEWUSER) */
 	pid_t pid;
 	struct my_iflist *tmpif, *my_iflist = NULL;
@@ -213,6 +213,28 @@ int main(int argc, char *argv[])
 	if (ret)
 		exit(EXIT_FAILURE);
 
+	/* The identifiers for namespaces used with lxc-unshare as given on the
+	 * manpage do not align with the standard identifiers. This affects
+	 * network, mount, and uts namespaces. The standard identifiers are:
+	 * "mnt", "uts", and "net" whereas lxc-unshare uses "MOUNT", "UTSNAME",
+	 * and "NETWORK". So let's use some cheap memmove()s to replace them by
+	 * their standard identifiers. Let's illustrate this with an example:
+	 * Assume the string:
+	 *
+	 *	"IPC|MOUNT|PID"
+	 *
+	 * then we memmove()
+	 *
+	 *	dest: del + 1 == ONT|PID
+	 *	src:  del + 3 == NT|PID
+	 */
+	while ((del = strstr(namespaces, "MOUNT")))
+		memmove(del + 1, del + 3, strlen(del) - 2);
+
+	for (it = (char *[]){"NETWORK", "UTSNAME", NULL}; it && *it; it++)
+		while ((del = strstr(namespaces, *it)))
+			memmove(del + 3, del + 7, strlen(del) - 6);
+
 	ret = lxc_fill_namespace_flags(namespaces, &flags);
 	if (ret)
 		usage(argv[0]);