/* -*- Mode: C; tab-width: 4; indent-tabs-mode: t; c-basic-offset: 4 -*- */
/* nm-platform.c - Handle runtime kernel networking configuration
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2, or (at your option)
 * any later version.
 *
 * This program 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 General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License along
 * with this program; if not, write to the Free Software Foundation, Inc.,
 * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Copyright (C) 2016 Red Hat, Inc.
 */

#include "nm-default.h"
#include "nmp-netns.h"

#include <fcntl.h>
#include <errno.h>
#include <sys/mount.h>
#include <sys/stat.h>
#include <sys/types.h>

#include "NetworkManagerUtils.h"

#define PROC_SELF_NS_MNT "/proc/self/ns/mnt"
#define PROC_SELF_NS_NET "/proc/self/ns/net"

#define _CLONE_NS_ALL    ((int) (CLONE_NEWNS | CLONE_NEWNET))
#define _CLONE_NS_ALL_V          CLONE_NEWNS , CLONE_NEWNET

NM_UTILS_FLAGS2STR_DEFINE_STATIC (_clone_ns_to_str, int,
	NM_UTILS_FLAGS2STR (CLONE_NEWNS,  "mnt"),
	NM_UTILS_FLAGS2STR (CLONE_NEWNET, "net"),
);

static const char *
__ns_types_to_str (int ns_types, int ns_types_already_set, char *buf, gsize len)
{
	const char *b = buf;
	char bb[200];

	nm_utils_strbuf_append_c (&buf, &len, '[');
	if (ns_types & ~ns_types_already_set) {
		nm_utils_strbuf_append_str (&buf, &len,
		                            _clone_ns_to_str (ns_types & ~ns_types_already_set, bb, sizeof (bb)));
	}
	if (ns_types & ns_types_already_set) {
		if (ns_types & ~ns_types_already_set)
			nm_utils_strbuf_append_c (&buf, &len, '/');
		nm_utils_strbuf_append_str (&buf, &len,
		                            _clone_ns_to_str (ns_types & ns_types_already_set, bb, sizeof (bb)));
	}
	nm_utils_strbuf_append_c (&buf, &len, ']');
	return b;
}
#define _ns_types_to_str(ns_types, ns_types_already_set, buf) \
	__ns_types_to_str (ns_types, ns_types_already_set, buf, sizeof (buf))

/*****************************************************************************/

#define _NMLOG_DOMAIN        LOGD_PLATFORM
#define _NMLOG_PREFIX_NAME   "netns"
#define _NMLOG(level, netns, ...) \
    G_STMT_START { \
        NMLogLevel _level = (level); \
        \
        if (nm_logging_enabled (_level, _NMLOG_DOMAIN)) { \
            NMPNetns *_netns = (netns); \
            char _sbuf[20]; \
            \
            _nm_log (_level, _NMLOG_DOMAIN, 0, NULL, NULL, \
                     "%s%s: " _NM_UTILS_MACRO_FIRST(__VA_ARGS__), \
                     _NMLOG_PREFIX_NAME, \
                     (_netns ? nm_sprintf_buf (_sbuf, "[%p]", _netns) : "") \
                     _NM_UTILS_MACRO_REST(__VA_ARGS__)); \
        } \
    } G_STMT_END

/*****************************************************************************/

NM_GOBJECT_PROPERTIES_DEFINE_BASE (
	PROP_FD_NET,
	PROP_FD_MNT,
);

typedef struct {
	int fd_net;
	int fd_mnt;
} NMPNetnsPrivate;

struct _NMPNetns {
	GObject parent;
	NMPNetnsPrivate _priv;
};

struct _NMPNetnsClass {
	GObjectClass parent;
};

G_DEFINE_TYPE (NMPNetns, nmp_netns, G_TYPE_OBJECT);

#define NMP_NETNS_GET_PRIVATE(self) _NM_GET_PRIVATE (self, NMPNetns, NMP_IS_NETNS)

/*****************************************************************************/

typedef struct {
	NMPNetns *netns;
	int count;
	int ns_types;
} NetnsInfo;

static void _stack_push (NMPNetns *netns, int ns_types);
static NMPNetns *_netns_new (GError **error);

/*****************************************************************************/

static GArray *netns_stack = NULL;

static void
_stack_ensure_init_impl (void)
{
	NMPNetns *netns;
	GError *error = NULL;

	nm_assert (!netns_stack);

	netns_stack = g_array_new (FALSE, FALSE, sizeof (NetnsInfo));

	/* at the bottom of the stack we must try to create a netns instance
	 * that we never pop. It's the base to which we need to return. */

	netns = _netns_new (&error);

	if (!netns) {
		/* don't know how to recover from this error. Netns are not supported. */
		_LOGE (NULL, "failed to create initial netns: %s", error->message);
		g_clear_error (&error);
		return;
	}

	_stack_push (netns, _CLONE_NS_ALL);

	/* we leak this instance inside netns_stack. It cannot be popped. */
	g_object_unref (netns);
}
#define _stack_ensure_init() \
	G_STMT_START { \
		if (G_UNLIKELY (!netns_stack)) { \
			_stack_ensure_init_impl (); \
		} \
	} G_STMT_END

static NMPNetns *
_stack_current_netns (int ns_types)
{
	guint j;

	nm_assert (netns_stack && netns_stack->len > 0);

	/* we search the stack top-down to find the netns that has
	 * all @ns_types set. */
	for (j = netns_stack->len; ns_types && j >= 1; ) {
		NetnsInfo *info;

		info = &g_array_index (netns_stack, NetnsInfo, --j);

		if (NM_FLAGS_ALL (info->ns_types, ns_types))
			return info->netns;
	}

	g_return_val_if_reached (NULL);
}

static int
_stack_current_ns_types (NMPNetns *netns, int ns_types)
{
	const int ns_types_check[] = { _CLONE_NS_ALL_V };
	guint i, j;
	int res = 0;

	nm_assert (netns);
	nm_assert (netns_stack && netns_stack->len > 0);

	/* we search the stack top-down to check which of @ns_types
	 * are already set to @netns. */
	for (j = netns_stack->len; ns_types && j >= 1; ) {
		NetnsInfo *info;

		info = &g_array_index (netns_stack, NetnsInfo, --j);
		if (info->netns != netns) {
			ns_types = NM_FLAGS_UNSET (ns_types, info->ns_types);
			continue;
		}

		for (i = 0; i < G_N_ELEMENTS (ns_types_check); i++) {
			if (   NM_FLAGS_ANY (ns_types, ns_types_check[i])
			    && NM_FLAGS_ANY (info->ns_types, ns_types_check[i])) {
				res = NM_FLAGS_SET (res, ns_types_check[i]);
				ns_types = NM_FLAGS_UNSET (ns_types, ns_types_check[i]);
			}
		}
	}

	return res;
}

static NetnsInfo *
_stack_peek (void)
{
	nm_assert (netns_stack);

	if (netns_stack->len > 0)
		return &g_array_index (netns_stack, NetnsInfo, (netns_stack->len - 1));
	return NULL;
}

static NetnsInfo *
_stack_bottom (void)
{
	nm_assert (netns_stack);

	if (netns_stack->len > 0)
		return &g_array_index (netns_stack, NetnsInfo, 0);
	return NULL;
}

static void
_stack_push (NMPNetns *netns, int ns_types)
{
	NetnsInfo *info;

	nm_assert (netns_stack);
	nm_assert (NMP_IS_NETNS (netns));
	nm_assert (NM_FLAGS_ANY (ns_types, _CLONE_NS_ALL));
	nm_assert (!NM_FLAGS_ANY (ns_types, ~_CLONE_NS_ALL));

	g_array_set_size (netns_stack, netns_stack->len + 1);

	info = &g_array_index (netns_stack, NetnsInfo, (netns_stack->len - 1));
	info->netns = g_object_ref (netns);
	info->ns_types = ns_types;
	info->count = 1;
}

static void
_stack_pop (void)
{
	NetnsInfo *info;

	nm_assert (netns_stack);
	nm_assert (netns_stack->len > 1);

	info = &g_array_index (netns_stack, NetnsInfo, (netns_stack->len - 1));

	nm_assert (NMP_IS_NETNS (info->netns));
	nm_assert (info->count == 1);

	g_object_unref (info->netns);

	g_array_set_size (netns_stack, netns_stack->len - 1);
}

static guint
_stack_size (void)
{
	nm_assert (netns_stack);

	return netns_stack->len;
}

/*****************************************************************************/

static NMPNetns *
_netns_new (GError **error)
{
	NMPNetns *self;
	int fd_net, fd_mnt;
	int errsv;

	fd_net = open (PROC_SELF_NS_NET, O_RDONLY | O_CLOEXEC);
	if (fd_net == -1) {
		errsv = errno;
		g_set_error (error, NM_UTILS_ERROR, NM_UTILS_ERROR_UNKNOWN,
		             "Failed opening netns: %s",
		             g_strerror (errsv));
		errno = errsv;
		return NULL;
	}

	fd_mnt = open (PROC_SELF_NS_MNT, O_RDONLY | O_CLOEXEC);
	if (fd_mnt == -1) {
		errsv = errno;
		g_set_error (error, NM_UTILS_ERROR, NM_UTILS_ERROR_UNKNOWN,
		             "Failed opening mntns: %s",
		             g_strerror (errsv));
		nm_close (fd_net);
		errno = errsv;
		return NULL;
	}

	self = g_object_new (NMP_TYPE_NETNS,
	                     NMP_NETNS_FD_NET, fd_net,
	                     NMP_NETNS_FD_MNT, fd_mnt,
	                     NULL);

	_LOGD (self, "new netns (net:%d, mnt:%d)", fd_net, fd_mnt);

	return self;
}

static int
_setns (NMPNetns *self, int type)
{
	char buf[100];
	int fd;
	NMPNetnsPrivate *priv = NMP_NETNS_GET_PRIVATE (self);

	nm_assert (NM_IN_SET (type, _CLONE_NS_ALL_V));

	fd = (type == CLONE_NEWNET) ? priv->fd_net : priv->fd_mnt;

	_LOGt (self, "set netns(%s, %d)", _ns_types_to_str (type, 0, buf), fd);

	return setns (fd, type);
}

static gboolean
_netns_switch_push (NMPNetns *self, int ns_types)
{
	int errsv;

	if (   NM_FLAGS_HAS (ns_types, CLONE_NEWNET)
	    && !_stack_current_ns_types (self, CLONE_NEWNET)
	    && _setns (self, CLONE_NEWNET) != 0) {
		errsv = errno;
		_LOGE (self, "failed to switch netns: %s", g_strerror (errsv));
		return FALSE;
	}
	if (   NM_FLAGS_HAS (ns_types, CLONE_NEWNS)
	    && !_stack_current_ns_types (self, CLONE_NEWNS)
	    && _setns (self, CLONE_NEWNS) != 0) {
		errsv = errno;
		_LOGE (self, "failed to switch mntns: %s", g_strerror (errsv));

		/* try to fix the mess by returning to the previous netns. */
		if (   NM_FLAGS_HAS (ns_types, CLONE_NEWNET)
	        && !_stack_current_ns_types (self, CLONE_NEWNET)) {
			self = _stack_current_netns (CLONE_NEWNET);
			if (   self
			    && _setns (self, CLONE_NEWNET) != 0) {
				errsv = errno;
				_LOGE (self, "failed to restore netns: %s", g_strerror (errsv));
			}
		}
		return FALSE;
	}

	return TRUE;
}

static gboolean
_netns_switch_pop (NMPNetns *self, int ns_types)
{
	int errsv;
	NMPNetns *current;
	int success = TRUE;

	if (   NM_FLAGS_HAS (ns_types, CLONE_NEWNET)
	    && (!self || !_stack_current_ns_types (self, CLONE_NEWNET))) {
		current = _stack_current_netns (CLONE_NEWNET);
		if (!current) {
			g_warn_if_reached ();
			success = FALSE;
		} else if (_setns (current, CLONE_NEWNET) != 0) {
			errsv = errno;
			_LOGE (self, "failed to switch netns: %s", g_strerror (errsv));
			success = FALSE;
		}
	}
	if (   NM_FLAGS_HAS (ns_types, CLONE_NEWNS)
	    && (!self || !_stack_current_ns_types (self, CLONE_NEWNS))) {
		current = _stack_current_netns (CLONE_NEWNS);
		if (!current) {
			g_warn_if_reached ();
			success = FALSE;
		} else if (_setns (current, CLONE_NEWNS) != 0) {
			errsv = errno;
			_LOGE (self, "failed to switch mntns: %s", g_strerror (errsv));
			success = FALSE;
		}
	}

	return success;
}

/*****************************************************************************/

int
nmp_netns_get_fd_net (NMPNetns *self)
{
	g_return_val_if_fail (NMP_IS_NETNS (self), 0);

	return NMP_NETNS_GET_PRIVATE (self)->fd_net;
}

int
nmp_netns_get_fd_mnt (NMPNetns *self)
{
	g_return_val_if_fail (NMP_IS_NETNS (self), 0);

	return NMP_NETNS_GET_PRIVATE (self)->fd_mnt;
}

/*****************************************************************************/

static gboolean
_nmp_netns_push_type (NMPNetns *self, int ns_types)
{
	NetnsInfo *info;
	char sbuf[100];

	_stack_ensure_init ();

	info = _stack_peek ();
	g_return_val_if_fail (info, FALSE);

	if (info->netns == self && info->ns_types == ns_types) {
		info->count++;
		_LOGt (self, "push#%u* %s (increase count to %d)",
		       _stack_size () - 1,
		       _ns_types_to_str (ns_types, ns_types, sbuf), info->count);
		return TRUE;
	}

	_LOGD (self, "push#%u %s",
	       _stack_size (),
	       _ns_types_to_str (ns_types,
	                         _stack_current_ns_types (self, ns_types),
	                         sbuf));

	if (!_netns_switch_push (self, ns_types))
		return FALSE;

	_stack_push (self, ns_types);
	return TRUE;
}

gboolean
nmp_netns_push (NMPNetns *self)
{
	g_return_val_if_fail (NMP_IS_NETNS (self), FALSE);

	return _nmp_netns_push_type (self, _CLONE_NS_ALL);
}

gboolean
nmp_netns_push_type (NMPNetns *self, int ns_types)
{
	g_return_val_if_fail (NMP_IS_NETNS (self), FALSE);
	g_return_val_if_fail (!NM_FLAGS_ANY (ns_types, ~_CLONE_NS_ALL), FALSE);

	return _nmp_netns_push_type (self, ns_types == 0 ? _CLONE_NS_ALL : ns_types);
}

NMPNetns *
nmp_netns_new (void)
{
	NMPNetns *self;
	int errsv;
	GError *error = NULL;
	unsigned long mountflags = 0;

	_stack_ensure_init ();

	if (!_stack_peek ()) {
		/* there are no netns instances. We cannot create a new one
		 * (because after unshare we couldn't return to the original one). */
		errno = ENOTSUP;
		return NULL;
	}

	if (unshare (_CLONE_NS_ALL) != 0) {
		errsv = errno;
		_LOGE (NULL, "failed to create new net and mnt namespace: %s", g_strerror (errsv));
		return NULL;
	}

	if (mount ("", "/", "none", MS_SLAVE | MS_REC, NULL) != 0) {
		errsv = errno;
		_LOGE (NULL, "failed mount --make-rslave: %s", g_strerror (errsv));
		goto err_out;
	}

	if (umount2 ("/sys", MNT_DETACH) != 0) {
		errsv = errno;
		_LOGE (NULL, "failed umount /sys: %s", g_strerror (errsv));
		goto err_out;
	}

	if (access ("/sys", W_OK) == -1)
		mountflags = MS_RDONLY;

	if (mount ("sysfs", "/sys", "sysfs", mountflags, NULL) != 0) {
		errsv = errno;
		_LOGE (NULL, "failed mount /sys: %s", g_strerror (errsv));
		goto err_out;
	}

	self = _netns_new (&error);
	if (!self) {
		errsv = errno;
		_LOGE (NULL, "failed to create netns after unshare: %s", error->message);
		g_clear_error (&error);
		goto err_out;
	}

	_stack_push (self, _CLONE_NS_ALL);

	return self;
err_out:
	_netns_switch_pop (NULL, _CLONE_NS_ALL);
	errno = errsv;
	return NULL;
}

gboolean
nmp_netns_pop (NMPNetns *self)
{
	NetnsInfo *info;
	int ns_types;

	g_return_val_if_fail (NMP_IS_NETNS (self), FALSE);

	_stack_ensure_init ();

	info = _stack_peek ();

	g_return_val_if_fail (info, FALSE);
	g_return_val_if_fail (info->netns == self, FALSE);

	if (info->count > 1) {
		info->count--;
		_LOGt (self, "pop#%u* (decrease count to %d)",
		       _stack_size () - 1, info->count);
		return TRUE;
	}
	g_return_val_if_fail (info->count == 1, FALSE);

	/* cannot pop the original netns. */
	g_return_val_if_fail (_stack_size () > 1, FALSE);

	_LOGD (self, "pop#%u", _stack_size () - 1);

	ns_types = info->ns_types;

	_stack_pop ();

	return _netns_switch_pop (self, ns_types);
}

NMPNetns *
nmp_netns_get_current (void)
{
	NetnsInfo *info;

	_stack_ensure_init ();

	info = _stack_peek ();
	return info ? info->netns : NULL;
}

NMPNetns *
nmp_netns_get_initial (void)
{
	NetnsInfo *info;

	_stack_ensure_init ();

	info = _stack_bottom ();
	return info ? info->netns : NULL;
}

gboolean
nmp_netns_is_initial (void)
{
	if (G_UNLIKELY (!netns_stack))
		return TRUE;

	return nmp_netns_get_current () == nmp_netns_get_initial ();
}

/*****************************************************************************/

gboolean
nmp_netns_bind_to_path (NMPNetns *self, const char *filename, int *out_fd)
{
	gs_free char *dirname = NULL;
	int errsv;
	int fd;
	nm_auto_pop_netns NMPNetns *netns_pop = NULL;

	g_return_val_if_fail (NMP_IS_NETNS (self), FALSE);
	g_return_val_if_fail (filename && filename[0] == '/', FALSE);

	if (!nmp_netns_push_type (self, CLONE_NEWNET))
		return FALSE;
	netns_pop = self;

	dirname = g_path_get_dirname (filename);
	if (mkdir (dirname, 0) != 0) {
		errsv = errno;
		if (errsv != EEXIST) {
			_LOGE (self, "bind: failed to create directory %s: %s",
			       dirname, g_strerror (errsv));
			return FALSE;
		}
	}

	if ((fd = creat (filename, S_IRUSR | S_IRGRP | S_IROTH)) == -1) {
		errsv = errno;
		_LOGE (self, "bind: failed to create %s: %s",
		       filename, g_strerror (errsv));
		return FALSE;
	}
	nm_close (fd);

	if (mount (PROC_SELF_NS_NET, filename, "none", MS_BIND, NULL) != 0) {
		errsv = errno;
		_LOGE (self, "bind: failed to mount %s to %s: %s",
		       PROC_SELF_NS_NET, filename, g_strerror (errsv));
		unlink (filename);
		return FALSE;
	}

	if (out_fd) {
		if ((fd = open (filename, O_RDONLY | O_CLOEXEC)) == -1) {
			errsv = errno;
			_LOGE (self, "bind: failed to open %s: %s", filename, g_strerror (errsv));
			umount2 (filename, MNT_DETACH);
			unlink (filename);
			return FALSE;
		}
		*out_fd = fd;
	}

	return TRUE;
}

gboolean
nmp_netns_bind_to_path_destroy (NMPNetns *self, const char *filename)
{
	int errsv;

	g_return_val_if_fail (NMP_IS_NETNS (self), FALSE);
	g_return_val_if_fail (filename && filename[0] == '/', FALSE);

	if (umount2 (filename, MNT_DETACH) != 0) {
		errsv = errno;
		_LOGE (self, "bind: failed to unmount2 %s: %s", filename, g_strerror (errsv));
		return FALSE;
	}
	if (unlink (filename) != 0) {
		errsv = errno;
		_LOGE (self, "bind: failed to unlink %s: %s", filename, g_strerror (errsv));
		return FALSE;
	}
	return TRUE;
}

/*****************************************************************************/

static void
set_property (GObject *object, guint prop_id,
              const GValue *value, GParamSpec *pspec)
{
	NMPNetns *self = NMP_NETNS (object);
	NMPNetnsPrivate *priv = NMP_NETNS_GET_PRIVATE (self);

	switch (prop_id) {
	case PROP_FD_NET:
		/* construct-only */
		priv->fd_net = g_value_get_int (value);
		g_return_if_fail (priv->fd_net > 0);
		break;
	case PROP_FD_MNT:
		/* construct-only */
		priv->fd_mnt = g_value_get_int (value);
		g_return_if_fail (priv->fd_mnt > 0);
		break;
	default:
		G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec);
		break;
	}
}

static void
nmp_netns_init (NMPNetns *self)
{
}

static void
dispose (GObject *object)
{
	NMPNetns *self = NMP_NETNS (object);
	NMPNetnsPrivate *priv = NMP_NETNS_GET_PRIVATE (self);

	nm_close (priv->fd_net);
	priv->fd_net = -1;

	nm_close (priv->fd_mnt);
	priv->fd_mnt = -1;

	G_OBJECT_CLASS (nmp_netns_parent_class)->dispose (object);
}

static void
nmp_netns_class_init (NMPNetnsClass *klass)
{
	GObjectClass *object_class = G_OBJECT_CLASS (klass);

	object_class->set_property = set_property;
	object_class->dispose = dispose;

	obj_properties[PROP_FD_NET]
	    = g_param_spec_int (NMP_NETNS_FD_NET, "", "",
	                        0, G_MAXINT, 0,
	                        G_PARAM_WRITABLE |
	                        G_PARAM_CONSTRUCT_ONLY |
	                        G_PARAM_STATIC_STRINGS);
	obj_properties[PROP_FD_MNT]
	    = g_param_spec_int (NMP_NETNS_FD_MNT, "", "",
	                        0, G_MAXINT, 0,
	                        G_PARAM_WRITABLE |
	                        G_PARAM_CONSTRUCT_ONLY |
	                        G_PARAM_STATIC_STRINGS);
	g_object_class_install_properties (object_class, _PROPERTY_ENUMS_LAST, obj_properties);
}