1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * Copyright (c) 2020 Laura Garcia Liebana <nevola@gmail.com>
4 * Copyright (c) 2020 Jose M. Guisado <guigom@riseup.net>
5 */
6
7#include <linux/etherdevice.h>
8#include <linux/kernel.h>
9#include <linux/init.h>
10#include <linux/module.h>
11#include <linux/netlink.h>
12#include <linux/netfilter.h>
13#include <linux/netfilter/nf_tables.h>
14#include <net/netfilter/nf_tables.h>
15#include <net/netfilter/nft_reject.h>
16#include <net/netfilter/ipv4/nf_reject.h>
17#include <net/netfilter/ipv6/nf_reject.h>
18
19static void nft_reject_queue_xmit(struct sk_buff *nskb, struct sk_buff *oldskb)
20{
21 dev_hard_header(skb: nskb, dev: nskb->dev, ntohs(oldskb->protocol),
22 daddr: eth_hdr(skb: oldskb)->h_source, saddr: eth_hdr(skb: oldskb)->h_dest,
23 len: nskb->len);
24 dev_queue_xmit(skb: nskb);
25}
26
27static void nft_reject_netdev_send_v4_tcp_reset(struct net *net,
28 struct sk_buff *oldskb,
29 const struct net_device *dev,
30 int hook)
31{
32 struct sk_buff *nskb;
33
34 nskb = nf_reject_skb_v4_tcp_reset(net, oldskb, dev, hook);
35 if (!nskb)
36 return;
37
38 nft_reject_queue_xmit(nskb, oldskb);
39}
40
41static void nft_reject_netdev_send_v4_unreach(struct net *net,
42 struct sk_buff *oldskb,
43 const struct net_device *dev,
44 int hook, u8 code)
45{
46 struct sk_buff *nskb;
47
48 nskb = nf_reject_skb_v4_unreach(net, oldskb, dev, hook, code);
49 if (!nskb)
50 return;
51
52 nft_reject_queue_xmit(nskb, oldskb);
53}
54
55static void nft_reject_netdev_send_v6_tcp_reset(struct net *net,
56 struct sk_buff *oldskb,
57 const struct net_device *dev,
58 int hook)
59{
60 struct sk_buff *nskb;
61
62 nskb = nf_reject_skb_v6_tcp_reset(net, oldskb, dev, hook);
63 if (!nskb)
64 return;
65
66 nft_reject_queue_xmit(nskb, oldskb);
67}
68
69
70static void nft_reject_netdev_send_v6_unreach(struct net *net,
71 struct sk_buff *oldskb,
72 const struct net_device *dev,
73 int hook, u8 code)
74{
75 struct sk_buff *nskb;
76
77 nskb = nf_reject_skb_v6_unreach(net, oldskb, dev, hook, code);
78 if (!nskb)
79 return;
80
81 nft_reject_queue_xmit(nskb, oldskb);
82}
83
84static void nft_reject_netdev_eval(const struct nft_expr *expr,
85 struct nft_regs *regs,
86 const struct nft_pktinfo *pkt)
87{
88 struct ethhdr *eth = eth_hdr(skb: pkt->skb);
89 struct nft_reject *priv = nft_expr_priv(expr);
90 const unsigned char *dest = eth->h_dest;
91
92 if (is_broadcast_ether_addr(addr: dest) ||
93 is_multicast_ether_addr(addr: dest))
94 goto out;
95
96 switch (eth->h_proto) {
97 case htons(ETH_P_IP):
98 switch (priv->type) {
99 case NFT_REJECT_ICMP_UNREACH:
100 nft_reject_netdev_send_v4_unreach(net: nft_net(pkt), oldskb: pkt->skb,
101 dev: nft_in(pkt),
102 hook: nft_hook(pkt),
103 code: priv->icmp_code);
104 break;
105 case NFT_REJECT_TCP_RST:
106 nft_reject_netdev_send_v4_tcp_reset(net: nft_net(pkt), oldskb: pkt->skb,
107 dev: nft_in(pkt),
108 hook: nft_hook(pkt));
109 break;
110 case NFT_REJECT_ICMPX_UNREACH:
111 nft_reject_netdev_send_v4_unreach(net: nft_net(pkt), oldskb: pkt->skb,
112 dev: nft_in(pkt),
113 hook: nft_hook(pkt),
114 code: nft_reject_icmp_code(code: priv->icmp_code));
115 break;
116 }
117 break;
118 case htons(ETH_P_IPV6):
119 switch (priv->type) {
120 case NFT_REJECT_ICMP_UNREACH:
121 nft_reject_netdev_send_v6_unreach(net: nft_net(pkt), oldskb: pkt->skb,
122 dev: nft_in(pkt),
123 hook: nft_hook(pkt),
124 code: priv->icmp_code);
125 break;
126 case NFT_REJECT_TCP_RST:
127 nft_reject_netdev_send_v6_tcp_reset(net: nft_net(pkt), oldskb: pkt->skb,
128 dev: nft_in(pkt),
129 hook: nft_hook(pkt));
130 break;
131 case NFT_REJECT_ICMPX_UNREACH:
132 nft_reject_netdev_send_v6_unreach(net: nft_net(pkt), oldskb: pkt->skb,
133 dev: nft_in(pkt),
134 hook: nft_hook(pkt),
135 code: nft_reject_icmpv6_code(code: priv->icmp_code));
136 break;
137 }
138 break;
139 default:
140 /* No explicit way to reject this protocol, drop it. */
141 break;
142 }
143out:
144 regs->verdict.code = NF_DROP;
145}
146
147static int nft_reject_netdev_validate(const struct nft_ctx *ctx,
148 const struct nft_expr *expr,
149 const struct nft_data **data)
150{
151 return nft_chain_validate_hooks(chain: ctx->chain, hook_flags: (1 << NF_NETDEV_INGRESS));
152}
153
154static struct nft_expr_type nft_reject_netdev_type;
155static const struct nft_expr_ops nft_reject_netdev_ops = {
156 .type = &nft_reject_netdev_type,
157 .size = NFT_EXPR_SIZE(sizeof(struct nft_reject)),
158 .eval = nft_reject_netdev_eval,
159 .init = nft_reject_init,
160 .dump = nft_reject_dump,
161 .validate = nft_reject_netdev_validate,
162 .reduce = NFT_REDUCE_READONLY,
163};
164
165static struct nft_expr_type nft_reject_netdev_type __read_mostly = {
166 .family = NFPROTO_NETDEV,
167 .name = "reject",
168 .ops = &nft_reject_netdev_ops,
169 .policy = nft_reject_policy,
170 .maxattr = NFTA_REJECT_MAX,
171 .owner = THIS_MODULE,
172};
173
174static int __init nft_reject_netdev_module_init(void)
175{
176 return nft_register_expr(&nft_reject_netdev_type);
177}
178
179static void __exit nft_reject_netdev_module_exit(void)
180{
181 nft_unregister_expr(&nft_reject_netdev_type);
182}
183
184module_init(nft_reject_netdev_module_init);
185module_exit(nft_reject_netdev_module_exit);
186
187MODULE_LICENSE("GPL");
188MODULE_AUTHOR("Laura Garcia Liebana <nevola@gmail.com>");
189MODULE_AUTHOR("Jose M. Guisado <guigom@riseup.net>");
190MODULE_DESCRIPTION("Reject packets from netdev via nftables");
191MODULE_ALIAS_NFT_AF_EXPR(5, "reject");
192

source code of linux/net/netfilter/nft_reject_netdev.c