/*-
 * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
 *
 * Copyright (c) 2021 Ng Peng Nam Sean
 * Copyright (c) 2022 Alexander V. Chernikov <melifaro@FreeBSD.org>
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");
#include <sys/param.h>
#include <sys/kernel.h>
#include <sys/malloc.h>
#include <sys/module.h>

#include <sys/lock.h>
#include <sys/rmlock.h>
#include <sys/ck.h>
#include <sys/syslog.h>

#include <netlink/netlink.h>
#include <netlink/netlink_ctl.h>
#include <netlink/netlink_var.h>

#include <machine/atomic.h>

MALLOC_DEFINE(M_NETLINK, "netlink", "Memory used for netlink packets");
FEATURE(netlink, "Netlink support");

#define	DEBUG_MOD_NAME	nl_mod
#define	DEBUG_MAX_LEVEL	LOG_DEBUG3
#include <netlink/netlink_debug.h>
_DECLARE_DEBUG(LOG_DEBUG);

SYSCTL_NODE(_net, OID_AUTO, netlink, CTLFLAG_RD, 0, "");
SYSCTL_NODE(_net_netlink, OID_AUTO, debug, CTLFLAG_RD | CTLFLAG_MPSAFE, 0, "");

#define NL_MAX_HANDLERS	20
struct nl_proto_handler _nl_handlers[NL_MAX_HANDLERS];
struct nl_proto_handler *nl_handlers = _nl_handlers;

CK_LIST_HEAD(nl_control_head, nl_control);
static struct nl_control_head vnets_head = CK_LIST_HEAD_INITIALIZER();

VNET_DEFINE(struct nl_control *, nl_ctl) = NULL;

struct mtx nl_global_mtx;
MTX_SYSINIT(nl_global_mtx, &nl_global_mtx, "global netlink lock", MTX_DEF);

#define NL_GLOBAL_LOCK()	mtx_lock(&nl_global_mtx)
#define NL_GLOBAL_UNLOCK()	mtx_unlock(&nl_global_mtx)

int netlink_unloading = 0;

static void
free_nl_ctl(struct nl_control *ctl)
{
	rm_destroy(&ctl->ctl_lock);
	free(ctl, M_NETLINK);
}

struct nl_control *
vnet_nl_ctl_init(void)
{
	struct nl_control *ctl;

	ctl = malloc(sizeof(struct nl_control), M_NETLINK, M_WAITOK | M_ZERO);
	rm_init(&ctl->ctl_lock, "netlink lock");
	CK_LIST_INIT(&ctl->ctl_port_head);
	CK_LIST_INIT(&ctl->ctl_pcb_head);

	NL_GLOBAL_LOCK();

	struct nl_control *tmp = atomic_load_ptr(&V_nl_ctl);

	if (tmp == NULL) {
		atomic_store_ptr(&V_nl_ctl, ctl);
		CK_LIST_INSERT_HEAD(&vnets_head, ctl, ctl_next);
		NL_LOG(LOG_DEBUG2, "VNET %p init done, inserted %p into global list",
		    curvnet, ctl);
	} else {
		NL_LOG(LOG_DEBUG, "per-VNET init clash, dropping this instance");
		free_nl_ctl(ctl);
		ctl = tmp;
	}

	NL_GLOBAL_UNLOCK();

	return (ctl);
}

static void
vnet_nl_ctl_destroy(const void *unused __unused)
{
	struct nl_control *ctl;

	/* Assume at the time all of the processes / sockets are dead */

	NL_GLOBAL_LOCK();
	ctl = atomic_load_ptr(&V_nl_ctl);
	atomic_store_ptr(&V_nl_ctl, NULL);
	if (ctl != NULL) {
		NL_LOG(LOG_DEBUG2, "Removing %p from global list", ctl);
		CK_LIST_REMOVE(ctl, ctl_next);
	}
	NL_GLOBAL_UNLOCK();

	if (ctl != NULL)
		free_nl_ctl(ctl);
}
VNET_SYSUNINIT(vnet_nl_ctl_destroy, SI_SUB_PROTO_IF, SI_ORDER_ANY,
    vnet_nl_ctl_destroy, NULL);

int
nl_verify_proto(int proto)
{
	if (proto < 0 || proto >= NL_MAX_HANDLERS) {
		return (EINVAL);
	}
	int handler_defined = nl_handlers[proto].cb != NULL;
	return (handler_defined ? 0 : EPROTONOSUPPORT);
}

const char *
nl_get_proto_name(int proto)
{
	return (nl_handlers[proto].proto_name);
}

bool
netlink_register_proto(int proto, const char *proto_name, nl_handler_f handler)
{
	if ((proto < 0) || (proto >= NL_MAX_HANDLERS))
		return (false);
	NL_GLOBAL_LOCK();
	KASSERT((nl_handlers[proto].cb == NULL), ("netlink handler %d is already set", proto));
	nl_handlers[proto].cb = handler;
	nl_handlers[proto].proto_name = proto_name;
	NL_GLOBAL_UNLOCK();
	NL_LOG(LOG_DEBUG2, "Registered netlink %s(%d) handler", proto_name, proto);
	return (true);
}

bool
netlink_unregister_proto(int proto)
{
	if ((proto < 0) || (proto >= NL_MAX_HANDLERS))
		return (false);
	NL_GLOBAL_LOCK();
	KASSERT((nl_handlers[proto].cb != NULL), ("netlink handler %d is not set", proto));
	nl_handlers[proto].cb = NULL;
	nl_handlers[proto].proto_name = NULL;
	NL_GLOBAL_UNLOCK();
	NL_LOG(LOG_DEBUG2, "Unregistered netlink proto %d handler", proto);
	return (true);
}

static bool
can_unload(void)
{
	struct nl_control *ctl;
	bool result = true;

	NL_GLOBAL_LOCK();

	CK_LIST_FOREACH(ctl, &vnets_head, ctl_next) {
		NL_LOG(LOG_DEBUG2, "Iterating VNET head %p", ctl);
		if (!CK_LIST_EMPTY(&ctl->ctl_pcb_head)) {
			NL_LOG(LOG_NOTICE, "non-empty socket list in ctl %p", ctl);
			result = false;
			break;
		}
	}

	NL_GLOBAL_UNLOCK();

	return (result);
}

static int
netlink_modevent(module_t mod __unused, int what, void *priv __unused)
{
	int ret = 0;

	switch (what) {
	case MOD_LOAD:
		NL_LOG(LOG_DEBUG2, "Loading");
		break;

	case MOD_UNLOAD:
		NL_LOG(LOG_DEBUG2, "Unload called");
		if (can_unload()) {
			NL_LOG(LOG_WARNING, "unloading");
			netlink_unloading = 1;
		} else
			ret = EBUSY;
		break;

	default:
		ret = EOPNOTSUPP;
		break;
	}

	return (ret);
}
static moduledata_t netlink_mod = { "netlink", netlink_modevent, NULL };

DECLARE_MODULE(netlink, netlink_mod, SI_SUB_PSEUDO, SI_ORDER_ANY);
MODULE_VERSION(netlink, 1);