1 /*
2  * Copyright (c) 2015 Pablo Neira Ayuso <pablo@netfilter.org>
3  *
4  * This program is free software; you can redistribute it and/or modify it
5  * under the terms of the GNU General Public License version 2 as published by
6  * the Free Software Foundation.
7  */
8 
9 #include <linux/kernel.h>
10 #include <linux/init.h>
11 #include <linux/module.h>
12 #include <linux/netlink.h>
13 #include <linux/netfilter.h>
14 #include <linux/netfilter/nf_tables.h>
15 #include <linux/ip.h>
16 #include <linux/ipv6.h>
17 #include <net/netfilter/nf_tables.h>
18 #include <net/netfilter/nf_dup_netdev.h>
19 #include <net/neighbour.h>
20 #include <net/ip.h>
21 
22 struct nft_fwd_netdev {
23 	enum nft_registers	sreg_dev:8;
24 };
25 
nft_fwd_netdev_eval(const struct nft_expr * expr,struct nft_regs * regs,const struct nft_pktinfo * pkt)26 static void nft_fwd_netdev_eval(const struct nft_expr *expr,
27 				struct nft_regs *regs,
28 				const struct nft_pktinfo *pkt)
29 {
30 	struct nft_fwd_netdev *priv = nft_expr_priv(expr);
31 	int oif = regs->data[priv->sreg_dev];
32 
33 	nf_fwd_netdev_egress(pkt, oif);
34 	regs->verdict.code = NF_STOLEN;
35 }
36 
37 static const struct nla_policy nft_fwd_netdev_policy[NFTA_FWD_MAX + 1] = {
38 	[NFTA_FWD_SREG_DEV]	= { .type = NLA_U32 },
39 	[NFTA_FWD_SREG_ADDR]	= { .type = NLA_U32 },
40 	[NFTA_FWD_NFPROTO]	= { .type = NLA_U32 },
41 };
42 
nft_fwd_netdev_init(const struct nft_ctx * ctx,const struct nft_expr * expr,const struct nlattr * const tb[])43 static int nft_fwd_netdev_init(const struct nft_ctx *ctx,
44 			       const struct nft_expr *expr,
45 			       const struct nlattr * const tb[])
46 {
47 	struct nft_fwd_netdev *priv = nft_expr_priv(expr);
48 
49 	if (tb[NFTA_FWD_SREG_DEV] == NULL)
50 		return -EINVAL;
51 
52 	priv->sreg_dev = nft_parse_register(tb[NFTA_FWD_SREG_DEV]);
53 	return nft_validate_register_load(priv->sreg_dev, sizeof(int));
54 }
55 
56 static const struct nft_expr_ops nft_fwd_netdev_ingress_ops;
57 
nft_fwd_netdev_dump(struct sk_buff * skb,const struct nft_expr * expr)58 static int nft_fwd_netdev_dump(struct sk_buff *skb, const struct nft_expr *expr)
59 {
60 	struct nft_fwd_netdev *priv = nft_expr_priv(expr);
61 
62 	if (nft_dump_register(skb, NFTA_FWD_SREG_DEV, priv->sreg_dev))
63 		goto nla_put_failure;
64 
65 	return 0;
66 
67 nla_put_failure:
68 	return -1;
69 }
70 
71 struct nft_fwd_neigh {
72 	enum nft_registers	sreg_dev:8;
73 	enum nft_registers	sreg_addr:8;
74 	u8			nfproto;
75 };
76 
nft_fwd_neigh_eval(const struct nft_expr * expr,struct nft_regs * regs,const struct nft_pktinfo * pkt)77 static void nft_fwd_neigh_eval(const struct nft_expr *expr,
78 			      struct nft_regs *regs,
79 			      const struct nft_pktinfo *pkt)
80 {
81 	struct nft_fwd_neigh *priv = nft_expr_priv(expr);
82 	void *addr = &regs->data[priv->sreg_addr];
83 	int oif = regs->data[priv->sreg_dev];
84 	unsigned int verdict = NF_STOLEN;
85 	struct sk_buff *skb = pkt->skb;
86 	struct net_device *dev;
87 	int neigh_table;
88 
89 	switch (priv->nfproto) {
90 	case NFPROTO_IPV4: {
91 		struct iphdr *iph;
92 
93 		if (skb->protocol != htons(ETH_P_IP)) {
94 			verdict = NFT_BREAK;
95 			goto out;
96 		}
97 		if (skb_try_make_writable(skb, sizeof(*iph))) {
98 			verdict = NF_DROP;
99 			goto out;
100 		}
101 		iph = ip_hdr(skb);
102 		ip_decrease_ttl(iph);
103 		neigh_table = NEIGH_ARP_TABLE;
104 		break;
105 		}
106 	case NFPROTO_IPV6: {
107 		struct ipv6hdr *ip6h;
108 
109 		if (skb->protocol != htons(ETH_P_IPV6)) {
110 			verdict = NFT_BREAK;
111 			goto out;
112 		}
113 		if (skb_try_make_writable(skb, sizeof(*ip6h))) {
114 			verdict = NF_DROP;
115 			goto out;
116 		}
117 		ip6h = ipv6_hdr(skb);
118 		ip6h->hop_limit--;
119 		neigh_table = NEIGH_ND_TABLE;
120 		break;
121 		}
122 	default:
123 		verdict = NFT_BREAK;
124 		goto out;
125 	}
126 
127 	dev = dev_get_by_index_rcu(nft_net(pkt), oif);
128 	if (dev == NULL)
129 		return;
130 
131 	skb->dev = dev;
132 	neigh_xmit(neigh_table, dev, addr, skb);
133 out:
134 	regs->verdict.code = verdict;
135 }
136 
nft_fwd_neigh_init(const struct nft_ctx * ctx,const struct nft_expr * expr,const struct nlattr * const tb[])137 static int nft_fwd_neigh_init(const struct nft_ctx *ctx,
138 			      const struct nft_expr *expr,
139 			      const struct nlattr * const tb[])
140 {
141 	struct nft_fwd_neigh *priv = nft_expr_priv(expr);
142 	unsigned int addr_len;
143 	int err;
144 
145 	if (!tb[NFTA_FWD_SREG_DEV] ||
146 	    !tb[NFTA_FWD_SREG_ADDR] ||
147 	    !tb[NFTA_FWD_NFPROTO])
148 		return -EINVAL;
149 
150 	priv->sreg_dev = nft_parse_register(tb[NFTA_FWD_SREG_DEV]);
151 	priv->sreg_addr = nft_parse_register(tb[NFTA_FWD_SREG_ADDR]);
152 	priv->nfproto = ntohl(nla_get_be32(tb[NFTA_FWD_NFPROTO]));
153 
154 	switch (priv->nfproto) {
155 	case NFPROTO_IPV4:
156 		addr_len = sizeof(struct in_addr);
157 		break;
158 	case NFPROTO_IPV6:
159 		addr_len = sizeof(struct in6_addr);
160 		break;
161 	default:
162 		return -EOPNOTSUPP;
163 	}
164 
165 	err = nft_validate_register_load(priv->sreg_dev, sizeof(int));
166 	if (err < 0)
167 		return err;
168 
169 	return nft_validate_register_load(priv->sreg_addr, addr_len);
170 }
171 
172 static const struct nft_expr_ops nft_fwd_netdev_ingress_ops;
173 
nft_fwd_neigh_dump(struct sk_buff * skb,const struct nft_expr * expr)174 static int nft_fwd_neigh_dump(struct sk_buff *skb, const struct nft_expr *expr)
175 {
176 	struct nft_fwd_neigh *priv = nft_expr_priv(expr);
177 
178 	if (nft_dump_register(skb, NFTA_FWD_SREG_DEV, priv->sreg_dev) ||
179 	    nft_dump_register(skb, NFTA_FWD_SREG_ADDR, priv->sreg_addr) ||
180 	    nla_put_be32(skb, NFTA_FWD_NFPROTO, htonl(priv->nfproto)))
181 		goto nla_put_failure;
182 
183 	return 0;
184 
185 nla_put_failure:
186 	return -1;
187 }
188 
189 static struct nft_expr_type nft_fwd_netdev_type;
190 static const struct nft_expr_ops nft_fwd_neigh_netdev_ops = {
191 	.type		= &nft_fwd_netdev_type,
192 	.size		= NFT_EXPR_SIZE(sizeof(struct nft_fwd_neigh)),
193 	.eval		= nft_fwd_neigh_eval,
194 	.init		= nft_fwd_neigh_init,
195 	.dump		= nft_fwd_neigh_dump,
196 };
197 
198 static const struct nft_expr_ops nft_fwd_netdev_ops = {
199 	.type		= &nft_fwd_netdev_type,
200 	.size		= NFT_EXPR_SIZE(sizeof(struct nft_fwd_netdev)),
201 	.eval		= nft_fwd_netdev_eval,
202 	.init		= nft_fwd_netdev_init,
203 	.dump		= nft_fwd_netdev_dump,
204 };
205 
206 static const struct nft_expr_ops *
nft_fwd_select_ops(const struct nft_ctx * ctx,const struct nlattr * const tb[])207 nft_fwd_select_ops(const struct nft_ctx *ctx,
208 		   const struct nlattr * const tb[])
209 {
210 	if (tb[NFTA_FWD_SREG_ADDR])
211 		return &nft_fwd_neigh_netdev_ops;
212 	if (tb[NFTA_FWD_SREG_DEV])
213 		return &nft_fwd_netdev_ops;
214 
215         return ERR_PTR(-EOPNOTSUPP);
216 }
217 
218 static struct nft_expr_type nft_fwd_netdev_type __read_mostly = {
219 	.family		= NFPROTO_NETDEV,
220 	.name		= "fwd",
221 	.select_ops	= nft_fwd_select_ops,
222 	.policy		= nft_fwd_netdev_policy,
223 	.maxattr	= NFTA_FWD_MAX,
224 	.owner		= THIS_MODULE,
225 };
226 
nft_fwd_netdev_module_init(void)227 static int __init nft_fwd_netdev_module_init(void)
228 {
229 	return nft_register_expr(&nft_fwd_netdev_type);
230 }
231 
nft_fwd_netdev_module_exit(void)232 static void __exit nft_fwd_netdev_module_exit(void)
233 {
234 	nft_unregister_expr(&nft_fwd_netdev_type);
235 }
236 
237 module_init(nft_fwd_netdev_module_init);
238 module_exit(nft_fwd_netdev_module_exit);
239 
240 MODULE_LICENSE("GPL");
241 MODULE_AUTHOR("Pablo Neira Ayuso <pablo@netfilter.org>");
242 MODULE_ALIAS_NFT_AF_EXPR(5, "fwd");
243