linux/include/linux/netfilter_netdev.h

/* SPDX-License-Identifier: GPL-2.0 */
#ifndef _NETFILTER_NETDEV_H_
#define _NETFILTER_NETDEV_H_

#include <linux/netfilter.h>
#include <linux/netdevice.h>

#ifdef CONFIG_NETFILTER_INGRESS
static inline bool nf_hook_ingress_active(const struct sk_buff *skb)
{ … }

/* caller must hold rcu_read_lock */
static inline int nf_hook_ingress(struct sk_buff *skb)
{ … }

#else /* CONFIG_NETFILTER_INGRESS */
static inline int nf_hook_ingress_active(struct sk_buff *skb)
{
	return 0;
}

static inline int nf_hook_ingress(struct sk_buff *skb)
{
	return 0;
}
#endif /* CONFIG_NETFILTER_INGRESS */

#ifdef CONFIG_NETFILTER_EGRESS
static inline bool nf_hook_egress_active(void)
{ … }

/**
 * nf_hook_egress - classify packets before transmission
 * @skb: packet to be classified
 * @rc: result code which shall be returned by __dev_queue_xmit() on failure
 * @dev: netdev whose egress hooks shall be applied to @skb
 *
 * Returns @skb on success or %NULL if the packet was consumed or filtered.
 * Caller must hold rcu_read_lock.
 *
 * On ingress, packets are classified first by tc, then by netfilter.
 * On egress, the order is reversed for symmetry.  Conceptually, tc and
 * netfilter can be thought of as layers, with netfilter layered above tc:
 * When tc redirects a packet to another interface, netfilter is not applied
 * because the packet is on the tc layer.
 *
 * The nf_skip_egress flag controls whether netfilter is applied on egress.
 * It is updated by __netif_receive_skb_core() and __dev_queue_xmit() when the
 * packet passes through tc and netfilter.  Because __dev_queue_xmit() may be
 * called recursively by tunnel drivers such as vxlan, the flag is reverted to
 * false after sch_handle_egress().  This ensures that netfilter is applied
 * both on the overlay and underlying network.
 */
static inline struct sk_buff *nf_hook_egress(struct sk_buff *skb, int *rc,
					     struct net_device *dev)
{ … }
#else /* CONFIG_NETFILTER_EGRESS */
static inline bool nf_hook_egress_active(void)
{
	return false;
}

static inline struct sk_buff *nf_hook_egress(struct sk_buff *skb, int *rc,
					     struct net_device *dev)
{
	return skb;
}
#endif /* CONFIG_NETFILTER_EGRESS */

static inline void nf_skip_egress(struct sk_buff *skb, bool skip)
{ … }

static inline void nf_hook_netdev_init(struct net_device *dev)
{ … }

#endif /* _NETFILTER_NETDEV_H_ */