start: pass namespaces as environment variables

[mirror_lxc.git] / src / lxc / namespace.c

/*
 * lxc: linux Container library
 *
 * (C) Copyright IBM Corp. 2007, 2009
 *
 * Authors:
 * Daniel Lezcano <daniel.lezcano at free.fr>
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
 */

#include <alloca.h>
#include <errno.h>
#include <fcntl.h>
#include <signal.h>
#include <unistd.h>
#include <sys/param.h>
#include <sys/stat.h>
#include <sys/types.h>

#include "log.h"
#include "namespace.h"
#include "utils.h"

lxc_log_define(lxc_namespace, lxc);

struct clone_arg {
	int (*fn)(void *);
	void *arg;
};

static int do_clone(void *arg)
{
	struct clone_arg *clone_arg = arg;
	return clone_arg->fn(clone_arg->arg);
}

pid_t lxc_clone(int (*fn)(void *), void *arg, int flags)
{
	struct clone_arg clone_arg = {
		.fn = fn,
		.arg = arg,
	};

	size_t stack_size = lxc_getpagesize();
	void *stack = alloca(stack_size);
	pid_t ret;

#ifdef __ia64__
	ret = __clone2(do_clone, stack,
		       stack_size, flags | SIGCHLD, &clone_arg);
#else
	ret = clone(do_clone, stack  + stack_size, flags | SIGCHLD, &clone_arg);
#endif
	if (ret < 0)
		ERROR("Failed to clone (%#x): %s.", flags, strerror(errno));

	return ret;
}

/* Leave the user namespace at the first position in the array of structs so
 * that we always attach to it first when iterating over the struct and using
 * setns() to switch namespaces. This especially affects lxc_attach(): Suppose
 * you cloned a new user namespace and mount namespace as an unprivileged user
 * on the host and want to setns() to the mount namespace. This requires you to
 * attach to the user namespace first otherwise the kernel will fail this check:
 *
 *        if (!ns_capable(mnt_ns->user_ns, CAP_SYS_ADMIN) ||
 *            !ns_capable(current_user_ns(), CAP_SYS_CHROOT) ||
 *            !ns_capable(current_user_ns(), CAP_SYS_ADMIN))
 *            return -EPERM;
 *
 *    in
 *
 *        linux/fs/namespace.c:mntns_install().
 */
const struct ns_info ns_info[LXC_NS_MAX] = {
	[LXC_NS_USER]    = { "user",   CLONE_NEWUSER,   "CLONE_NEWUSER",   "LXC_USER_NS"    },
	[LXC_NS_MNT]    =  { "mnt",    CLONE_NEWNS,     "CLONE_NEWNS",     "LXC_MNT_NS"     },
	[LXC_NS_PID]    =  { "pid",    CLONE_NEWPID,    "CLONE_NEWPID",    "LXC_PID_NS"     },
	[LXC_NS_UTS]    =  { "uts",    CLONE_NEWUTS,    "CLONE_NEWUTS",    "LXC_UTS_NS"     },
	[LXC_NS_IPC]    =  { "ipc",    CLONE_NEWIPC,    "CLONE_NEWIPC",    "LXC_IPC_NS"     },
	[LXC_NS_NET]    =  { "net",    CLONE_NEWNET,    "CLONE_NEWNET",    "LXC_NET_NS"     },
	[LXC_NS_CGROUP] =  { "cgroup", CLONE_NEWCGROUP, "CLONE_NEWCGROUP", "LXC_CGROUP_NS"  }
};

int lxc_namespace_2_cloneflag(const char *namespace)
{
	int i;
	for (i = 0; i < LXC_NS_MAX; i++)
		if (!strcasecmp(ns_info[i].proc_name, namespace))
			return ns_info[i].clone_flag;

	ERROR("Invalid namespace name \"%s\"", namespace);
	return -EINVAL;
}

int lxc_namespace_2_ns_idx(const char *namespace)
{
	int i;
	for (i = 0; i < LXC_NS_MAX; i++)
		if (!strcmp(ns_info[i].proc_name, namespace))
			return i;

	ERROR("Invalid namespace name \"%s\"", namespace);
	return -EINVAL;
}

int lxc_fill_namespace_flags(char *flaglist, int *flags)
{
	char *token, *saveptr = NULL;
	int aflag;

	if (!flaglist) {
		ERROR("At least one namespace is needed.");
		return -1;
	}

	token = strtok_r(flaglist, "|", &saveptr);
	while (token) {

		aflag = lxc_namespace_2_cloneflag(token);
		if (aflag < 0)
			return -1;

		*flags |= aflag;

		token = strtok_r(NULL, "|", &saveptr);
	}
	return 0;
}