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6bbb9ad3 JGG |
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/kernel.h> | |
8 | #include <linux/init.h> | |
9 | #include <linux/module.h> | |
10 | #include <linux/netlink.h> | |
11 | #include <linux/netfilter.h> | |
12 | #include <linux/netfilter/nf_tables.h> | |
13 | #include <net/netfilter/nf_tables.h> | |
14 | #include <net/netfilter/nft_reject.h> | |
15 | #include <net/netfilter/ipv4/nf_reject.h> | |
16 | #include <net/netfilter/ipv6/nf_reject.h> | |
17 | ||
18 | static void nft_reject_queue_xmit(struct sk_buff *nskb, struct sk_buff *oldskb) | |
19 | { | |
20 | dev_hard_header(nskb, nskb->dev, ntohs(oldskb->protocol), | |
21 | eth_hdr(oldskb)->h_source, eth_hdr(oldskb)->h_dest, | |
22 | nskb->len); | |
23 | dev_queue_xmit(nskb); | |
24 | } | |
25 | ||
26 | static void nft_reject_netdev_send_v4_tcp_reset(struct net *net, | |
27 | struct sk_buff *oldskb, | |
28 | const struct net_device *dev, | |
29 | int hook) | |
30 | { | |
31 | struct sk_buff *nskb; | |
32 | ||
33 | nskb = nf_reject_skb_v4_tcp_reset(net, oldskb, dev, hook); | |
34 | if (!nskb) | |
35 | return; | |
36 | ||
37 | nft_reject_queue_xmit(nskb, oldskb); | |
38 | } | |
39 | ||
40 | static void nft_reject_netdev_send_v4_unreach(struct net *net, | |
41 | struct sk_buff *oldskb, | |
42 | const struct net_device *dev, | |
43 | int hook, u8 code) | |
44 | { | |
45 | struct sk_buff *nskb; | |
46 | ||
47 | nskb = nf_reject_skb_v4_unreach(net, oldskb, dev, hook, code); | |
48 | if (!nskb) | |
49 | return; | |
50 | ||
51 | nft_reject_queue_xmit(nskb, oldskb); | |
52 | } | |
53 | ||
54 | static void nft_reject_netdev_send_v6_tcp_reset(struct net *net, | |
55 | struct sk_buff *oldskb, | |
56 | const struct net_device *dev, | |
57 | int hook) | |
58 | { | |
59 | struct sk_buff *nskb; | |
60 | ||
61 | nskb = nf_reject_skb_v6_tcp_reset(net, oldskb, dev, hook); | |
62 | if (!nskb) | |
63 | return; | |
64 | ||
65 | nft_reject_queue_xmit(nskb, oldskb); | |
66 | } | |
67 | ||
68 | ||
69 | static void nft_reject_netdev_send_v6_unreach(struct net *net, | |
70 | struct sk_buff *oldskb, | |
71 | const struct net_device *dev, | |
72 | int hook, u8 code) | |
73 | { | |
74 | struct sk_buff *nskb; | |
75 | ||
76 | nskb = nf_reject_skb_v6_unreach(net, oldskb, dev, hook, code); | |
77 | if (!nskb) | |
78 | return; | |
79 | ||
80 | nft_reject_queue_xmit(nskb, oldskb); | |
81 | } | |
82 | ||
83 | static void nft_reject_netdev_eval(const struct nft_expr *expr, | |
84 | struct nft_regs *regs, | |
85 | const struct nft_pktinfo *pkt) | |
86 | { | |
87 | struct ethhdr *eth = eth_hdr(pkt->skb); | |
88 | struct nft_reject *priv = nft_expr_priv(expr); | |
89 | const unsigned char *dest = eth->h_dest; | |
90 | ||
91 | if (is_broadcast_ether_addr(dest) || | |
92 | is_multicast_ether_addr(dest)) | |
93 | goto out; | |
94 | ||
95 | switch (eth->h_proto) { | |
96 | case htons(ETH_P_IP): | |
97 | switch (priv->type) { | |
98 | case NFT_REJECT_ICMP_UNREACH: | |
99 | nft_reject_netdev_send_v4_unreach(nft_net(pkt), pkt->skb, | |
100 | nft_in(pkt), | |
101 | nft_hook(pkt), | |
102 | priv->icmp_code); | |
103 | break; | |
104 | case NFT_REJECT_TCP_RST: | |
105 | nft_reject_netdev_send_v4_tcp_reset(nft_net(pkt), pkt->skb, | |
106 | nft_in(pkt), | |
107 | nft_hook(pkt)); | |
108 | break; | |
109 | case NFT_REJECT_ICMPX_UNREACH: | |
110 | nft_reject_netdev_send_v4_unreach(nft_net(pkt), pkt->skb, | |
111 | nft_in(pkt), | |
112 | nft_hook(pkt), | |
113 | nft_reject_icmp_code(priv->icmp_code)); | |
114 | break; | |
115 | } | |
116 | break; | |
117 | case htons(ETH_P_IPV6): | |
118 | switch (priv->type) { | |
119 | case NFT_REJECT_ICMP_UNREACH: | |
120 | nft_reject_netdev_send_v6_unreach(nft_net(pkt), pkt->skb, | |
121 | nft_in(pkt), | |
122 | nft_hook(pkt), | |
123 | priv->icmp_code); | |
124 | break; | |
125 | case NFT_REJECT_TCP_RST: | |
126 | nft_reject_netdev_send_v6_tcp_reset(nft_net(pkt), pkt->skb, | |
127 | nft_in(pkt), | |
128 | nft_hook(pkt)); | |
129 | break; | |
130 | case NFT_REJECT_ICMPX_UNREACH: | |
131 | nft_reject_netdev_send_v6_unreach(nft_net(pkt), pkt->skb, | |
132 | nft_in(pkt), | |
133 | nft_hook(pkt), | |
134 | nft_reject_icmpv6_code(priv->icmp_code)); | |
135 | break; | |
136 | } | |
137 | break; | |
138 | default: | |
139 | /* No explicit way to reject this protocol, drop it. */ | |
140 | break; | |
141 | } | |
142 | out: | |
143 | regs->verdict.code = NF_DROP; | |
144 | } | |
145 | ||
146 | static int nft_reject_netdev_validate(const struct nft_ctx *ctx, | |
147 | const struct nft_expr *expr, | |
148 | const struct nft_data **data) | |
149 | { | |
150 | return nft_chain_validate_hooks(ctx->chain, (1 << NF_NETDEV_INGRESS)); | |
151 | } | |
152 | ||
153 | static struct nft_expr_type nft_reject_netdev_type; | |
154 | static const struct nft_expr_ops nft_reject_netdev_ops = { | |
155 | .type = &nft_reject_netdev_type, | |
156 | .size = NFT_EXPR_SIZE(sizeof(struct nft_reject)), | |
157 | .eval = nft_reject_netdev_eval, | |
158 | .init = nft_reject_init, | |
159 | .dump = nft_reject_dump, | |
160 | .validate = nft_reject_netdev_validate, | |
161 | }; | |
162 | ||
163 | static struct nft_expr_type nft_reject_netdev_type __read_mostly = { | |
164 | .family = NFPROTO_NETDEV, | |
165 | .name = "reject", | |
166 | .ops = &nft_reject_netdev_ops, | |
167 | .policy = nft_reject_policy, | |
168 | .maxattr = NFTA_REJECT_MAX, | |
169 | .owner = THIS_MODULE, | |
170 | }; | |
171 | ||
172 | static int __init nft_reject_netdev_module_init(void) | |
173 | { | |
174 | return nft_register_expr(&nft_reject_netdev_type); | |
175 | } | |
176 | ||
177 | static void __exit nft_reject_netdev_module_exit(void) | |
178 | { | |
179 | nft_unregister_expr(&nft_reject_netdev_type); | |
180 | } | |
181 | ||
182 | module_init(nft_reject_netdev_module_init); | |
183 | module_exit(nft_reject_netdev_module_exit); | |
184 | ||
185 | MODULE_LICENSE("GPL"); | |
186 | MODULE_AUTHOR("Laura Garcia Liebana <nevola@gmail.com>"); | |
187 | MODULE_AUTHOR("Jose M. Guisado <guigom@riseup.net>"); | |
188 | MODULE_DESCRIPTION("Reject packets from netdev via nftables"); | |
189 | MODULE_ALIAS_NFT_AF_EXPR(5, "reject"); |