1/* SPDX-License-Identifier: GPL-2.0 */
2#ifndef _NETFILTER_NETDEV_H_
3#define _NETFILTER_NETDEV_H_
4
5#include <linux/netfilter.h>
6#include <linux/netdevice.h>
7
8#ifdef CONFIG_NETFILTER_INGRESS
9static inline bool nf_hook_ingress_active(const struct sk_buff *skb)
10{
11#ifdef CONFIG_JUMP_LABEL
12 if (!static_key_false(&nf_hooks_needed[NFPROTO_NETDEV][NF_NETDEV_INGRESS]))
13 return false;
14#endif
15 return rcu_access_pointer(skb->dev->nf_hooks_ingress);
16}
17
18/* caller must hold rcu_read_lock */
19static inline int nf_hook_ingress(struct sk_buff *skb)
20{
21 struct nf_hook_entries *e = rcu_dereference(skb->dev->nf_hooks_ingress);
22 struct nf_hook_state state;
23 int ret;
24
25 /* Must recheck the ingress hook head, in the event it became NULL
26 * after the check in nf_hook_ingress_active evaluated to true.
27 */
28 if (unlikely(!e))
29 return 0;
30
31 nf_hook_state_init(&state, NF_NETDEV_INGRESS,
32 NFPROTO_NETDEV, skb->dev, NULL, NULL,
33 dev_net(skb->dev), NULL);
34 ret = nf_hook_slow(skb, &state, e, 0);
35 if (ret == 0)
36 return -1;
37
38 return ret;
39}
40
41#else /* CONFIG_NETFILTER_INGRESS */
42static inline int nf_hook_ingress_active(struct sk_buff *skb)
43{
44 return 0;
45}
46
47static inline int nf_hook_ingress(struct sk_buff *skb)
48{
49 return 0;
50}
51#endif /* CONFIG_NETFILTER_INGRESS */
52
53#ifdef CONFIG_NETFILTER_EGRESS
54static inline bool nf_hook_egress_active(void)
55{
56#ifdef CONFIG_JUMP_LABEL
57 if (!static_key_false(&nf_hooks_needed[NFPROTO_NETDEV][NF_NETDEV_EGRESS]))
58 return false;
59#endif
60 return true;
61}
62
63/**
64 * nf_hook_egress - classify packets before transmission
65 * @skb: packet to be classified
66 * @rc: result code which shall be returned by __dev_queue_xmit() on failure
67 * @dev: netdev whose egress hooks shall be applied to @skb
68 *
69 * Returns @skb on success or %NULL if the packet was consumed or filtered.
70 * Caller must hold rcu_read_lock.
71 *
72 * On ingress, packets are classified first by tc, then by netfilter.
73 * On egress, the order is reversed for symmetry. Conceptually, tc and
74 * netfilter can be thought of as layers, with netfilter layered above tc:
75 * When tc redirects a packet to another interface, netfilter is not applied
76 * because the packet is on the tc layer.
77 *
78 * The nf_skip_egress flag controls whether netfilter is applied on egress.
79 * It is updated by __netif_receive_skb_core() and __dev_queue_xmit() when the
80 * packet passes through tc and netfilter. Because __dev_queue_xmit() may be
81 * called recursively by tunnel drivers such as vxlan, the flag is reverted to
82 * false after sch_handle_egress(). This ensures that netfilter is applied
83 * both on the overlay and underlying network.
84 */
85static inline struct sk_buff *nf_hook_egress(struct sk_buff *skb, int *rc,
86 struct net_device *dev)
87{
88 struct nf_hook_entries *e;
89 struct nf_hook_state state;
90 int ret;
91
92#ifdef CONFIG_NETFILTER_SKIP_EGRESS
93 if (skb->nf_skip_egress)
94 return skb;
95#endif
96
97 e = rcu_dereference_check(dev->nf_hooks_egress, rcu_read_lock_bh_held());
98 if (!e)
99 return skb;
100
101 nf_hook_state_init(&state, NF_NETDEV_EGRESS,
102 NFPROTO_NETDEV, NULL, dev, NULL,
103 dev_net(dev), NULL);
104
105 /* nf assumes rcu_read_lock, not just read_lock_bh */
106 rcu_read_lock();
107 ret = nf_hook_slow(skb, &state, e, 0);
108 rcu_read_unlock();
109
110 if (ret == 1) {
111 return skb;
112 } else if (ret < 0) {
113 *rc = NET_XMIT_DROP;
114 return NULL;
115 } else { /* ret == 0 */
116 *rc = NET_XMIT_SUCCESS;
117 return NULL;
118 }
119}
120#else /* CONFIG_NETFILTER_EGRESS */
121static inline bool nf_hook_egress_active(void)
122{
123 return false;
124}
125
126static inline struct sk_buff *nf_hook_egress(struct sk_buff *skb, int *rc,
127 struct net_device *dev)
128{
129 return skb;
130}
131#endif /* CONFIG_NETFILTER_EGRESS */
132
133static inline void nf_skip_egress(struct sk_buff *skb, bool skip)
134{
135#ifdef CONFIG_NETFILTER_SKIP_EGRESS
136 skb->nf_skip_egress = skip;
137#endif
138}
139
140static inline void nf_hook_netdev_init(struct net_device *dev)
141{
142#ifdef CONFIG_NETFILTER_INGRESS
143 RCU_INIT_POINTER(dev->nf_hooks_ingress, NULL);
144#endif
145#ifdef CONFIG_NETFILTER_EGRESS
146 RCU_INIT_POINTER(dev->nf_hooks_egress, NULL);
147#endif
148}
149
150#endif /* _NETFILTER_NETDEV_H_ */
151

source code of linux/include/linux/netfilter_netdev.h