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
nft_reject_queue_xmit(struct sk_buff * nskb,struct sk_buff * oldskb)19 static void nft_reject_queue_xmit(struct sk_buff *nskb, struct sk_buff *oldskb)
20 {
21 dev_hard_header(nskb, nskb->dev, ntohs(oldskb->protocol),
22 eth_hdr(oldskb)->h_source, eth_hdr(oldskb)->h_dest,
23 nskb->len);
24 dev_queue_xmit(nskb);
25 }
26
nft_reject_netdev_send_v4_tcp_reset(struct net * net,struct sk_buff * oldskb,const struct net_device * dev,int hook)27 static 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
nft_reject_netdev_send_v4_unreach(struct net * net,struct sk_buff * oldskb,const struct net_device * dev,int hook,u8 code)41 static 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
nft_reject_netdev_send_v6_tcp_reset(struct net * net,struct sk_buff * oldskb,const struct net_device * dev,int hook)55 static 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
nft_reject_netdev_send_v6_unreach(struct net * net,struct sk_buff * oldskb,const struct net_device * dev,int hook,u8 code)70 static 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
nft_reject_netdev_eval(const struct nft_expr * expr,struct nft_regs * regs,const struct nft_pktinfo * pkt)84 static 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(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(dest) ||
93 is_multicast_ether_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(nft_net(pkt), pkt->skb,
101 nft_in(pkt),
102 nft_hook(pkt),
103 priv->icmp_code);
104 break;
105 case NFT_REJECT_TCP_RST:
106 nft_reject_netdev_send_v4_tcp_reset(nft_net(pkt), pkt->skb,
107 nft_in(pkt),
108 nft_hook(pkt));
109 break;
110 case NFT_REJECT_ICMPX_UNREACH:
111 nft_reject_netdev_send_v4_unreach(nft_net(pkt), pkt->skb,
112 nft_in(pkt),
113 nft_hook(pkt),
114 nft_reject_icmp_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(nft_net(pkt), pkt->skb,
122 nft_in(pkt),
123 nft_hook(pkt),
124 priv->icmp_code);
125 break;
126 case NFT_REJECT_TCP_RST:
127 nft_reject_netdev_send_v6_tcp_reset(nft_net(pkt), pkt->skb,
128 nft_in(pkt),
129 nft_hook(pkt));
130 break;
131 case NFT_REJECT_ICMPX_UNREACH:
132 nft_reject_netdev_send_v6_unreach(nft_net(pkt), pkt->skb,
133 nft_in(pkt),
134 nft_hook(pkt),
135 nft_reject_icmpv6_code(priv->icmp_code));
136 break;
137 }
138 break;
139 default:
140 /* No explicit way to reject this protocol, drop it. */
141 break;
142 }
143 out:
144 regs->verdict.code = NF_DROP;
145 }
146
nft_reject_netdev_validate(const struct nft_ctx * ctx,const struct nft_expr * expr)147 static int nft_reject_netdev_validate(const struct nft_ctx *ctx,
148 const struct nft_expr *expr)
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 .reduce = NFT_REDUCE_READONLY,
162 };
163
164 static struct nft_expr_type nft_reject_netdev_type __read_mostly = {
165 .family = NFPROTO_NETDEV,
166 .name = "reject",
167 .ops = &nft_reject_netdev_ops,
168 .policy = nft_reject_policy,
169 .maxattr = NFTA_REJECT_MAX,
170 .owner = THIS_MODULE,
171 };
172
nft_reject_netdev_module_init(void)173 static int __init nft_reject_netdev_module_init(void)
174 {
175 return nft_register_expr(&nft_reject_netdev_type);
176 }
177
nft_reject_netdev_module_exit(void)178 static void __exit nft_reject_netdev_module_exit(void)
179 {
180 nft_unregister_expr(&nft_reject_netdev_type);
181 }
182
183 module_init(nft_reject_netdev_module_init);
184 module_exit(nft_reject_netdev_module_exit);
185
186 MODULE_LICENSE("GPL");
187 MODULE_AUTHOR("Laura Garcia Liebana <nevola@gmail.com>");
188 MODULE_AUTHOR("Jose M. Guisado <guigom@riseup.net>");
189 MODULE_DESCRIPTION("Reject packets from netdev via nftables");
190 MODULE_ALIAS_NFT_AF_EXPR(5, "reject");
191