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
nft_reject_queue_xmit(struct sk_buff * nskb,struct sk_buff * oldskb)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
nft_reject_netdev_send_v4_tcp_reset(struct net * net,struct sk_buff * oldskb,const struct net_device * dev,int hook)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
nft_reject_netdev_send_v4_unreach(struct net * net,struct sk_buff * oldskb,const struct net_device * dev,int hook,u8 code)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
nft_reject_netdev_send_v6_tcp_reset(struct net * net,struct sk_buff * oldskb,const struct net_device * dev,int hook)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
nft_reject_netdev_send_v6_unreach(struct net * net,struct sk_buff * oldskb,const struct net_device * dev,int hook,u8 code)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
nft_reject_netdev_eval(const struct nft_expr * expr,struct nft_regs * regs,const struct nft_pktinfo * pkt)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
nft_reject_netdev_validate(const struct nft_ctx * ctx,const struct nft_expr * expr,const struct nft_data ** data)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
nft_reject_netdev_module_init(void)172 static int __init nft_reject_netdev_module_init(void)
173 {
174 return nft_register_expr(&nft_reject_netdev_type);
175 }
176
nft_reject_netdev_module_exit(void)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");
190