nft_fwd_netdev.c

  1// SPDX-License-Identifier: GPL-2.0-only
  2/*
  3 * Copyright (c) 2015 Pablo Neira Ayuso <pablo@netfilter.org>
  4 */
  5
  6#include <linux/kernel.h>
  7#include <linux/init.h>
  8#include <linux/module.h>
  9#include <linux/netlink.h>
 10#include <linux/netfilter.h>
 11#include <linux/netfilter/nf_tables.h>
 12#include <linux/ip.h>
 13#include <linux/ipv6.h>
 14#include <net/netfilter/nf_tables.h>
 15#include <net/netfilter/nf_tables_offload.h>
 16#include <net/netfilter/nf_dup_netdev.h>
 17#include <net/neighbour.h>
 18#include <net/ip.h>
 19
 20struct nft_fwd_netdev {
 21	u8	sreg_dev;
 22};
 23
 24static void nft_fwd_netdev_eval(const struct nft_expr *expr,
 25				struct nft_regs *regs,
 26				const struct nft_pktinfo *pkt)
 27{
 28	struct nft_fwd_netdev *priv = nft_expr_priv(expr);
 29	int oif = regs->data[priv->sreg_dev];
 30	struct sk_buff *skb = pkt->skb;
 31
 32	/* This is used by ifb only. */
 33	skb->skb_iif = skb->dev->ifindex;
 34	skb_set_redirected(skb, nft_hook(pkt) == NF_NETDEV_INGRESS);
 35
 36	nf_fwd_netdev_egress(pkt, oif);
 37	regs->verdict.code = NF_STOLEN;
 38}
 39
 40static const struct nla_policy nft_fwd_netdev_policy[NFTA_FWD_MAX + 1] = {
 41	[NFTA_FWD_SREG_DEV]	= { .type = NLA_U32 },
 42	[NFTA_FWD_SREG_ADDR]	= { .type = NLA_U32 },
 43	[NFTA_FWD_NFPROTO]	= NLA_POLICY_MAX(NLA_BE32, 255),
 44};
 45
 46static int nft_fwd_netdev_init(const struct nft_ctx *ctx,
 47			       const struct nft_expr *expr,
 48			       const struct nlattr * const tb[])
 49{
 50	struct nft_fwd_netdev *priv = nft_expr_priv(expr);
 51
 52	if (tb[NFTA_FWD_SREG_DEV] == NULL)
 53		return -EINVAL;
 54
 55	return nft_parse_register_load(ctx, tb[NFTA_FWD_SREG_DEV], &priv->sreg_dev,
 56				       sizeof(int));
 57}
 58
 59static int nft_fwd_netdev_dump(struct sk_buff *skb,
 60			       const struct nft_expr *expr, bool reset)
 61{
 62	struct nft_fwd_netdev *priv = nft_expr_priv(expr);
 63
 64	if (nft_dump_register(skb, NFTA_FWD_SREG_DEV, priv->sreg_dev))
 65		goto nla_put_failure;
 66
 67	return 0;
 68
 69nla_put_failure:
 70	return -1;
 71}
 72
 73static int nft_fwd_netdev_offload(struct nft_offload_ctx *ctx,
 74				  struct nft_flow_rule *flow,
 75				  const struct nft_expr *expr)
 76{
 77	const struct nft_fwd_netdev *priv = nft_expr_priv(expr);
 78	int oif = ctx->regs[priv->sreg_dev].data.data[0];
 79
 80	return nft_fwd_dup_netdev_offload(ctx, flow, FLOW_ACTION_REDIRECT, oif);
 81}
 82
 83static bool nft_fwd_netdev_offload_action(const struct nft_expr *expr)
 84{
 85	return true;
 86}
 87
 88struct nft_fwd_neigh {
 89	u8			sreg_dev;
 90	u8			sreg_addr;
 91	u8			nfproto;
 92};
 93
 94static void nft_fwd_neigh_eval(const struct nft_expr *expr,
 95			      struct nft_regs *regs,
 96			      const struct nft_pktinfo *pkt)
 97{
 98	struct nft_fwd_neigh *priv = nft_expr_priv(expr);
 99	void *addr = &regs->data[priv->sreg_addr];
100	int oif = regs->data[priv->sreg_dev];
101	unsigned int verdict = NF_STOLEN;
102	struct sk_buff *skb = pkt->skb;
103	struct net_device *dev;
104	int neigh_table;
105
106	switch (priv->nfproto) {
107	case NFPROTO_IPV4: {
108		struct iphdr *iph;
109
110		if (skb->protocol != htons(ETH_P_IP)) {
111			verdict = NFT_BREAK;
112			goto out;
113		}
114		if (skb_try_make_writable(skb, sizeof(*iph))) {
115			verdict = NF_DROP;
116			goto out;
117		}
118		iph = ip_hdr(skb);
119		ip_decrease_ttl(iph);
120		neigh_table = NEIGH_ARP_TABLE;
121		break;
122		}
123	case NFPROTO_IPV6: {
124		struct ipv6hdr *ip6h;
125
126		if (skb->protocol != htons(ETH_P_IPV6)) {
127			verdict = NFT_BREAK;
128			goto out;
129		}
130		if (skb_try_make_writable(skb, sizeof(*ip6h))) {
131			verdict = NF_DROP;
132			goto out;
133		}
134		ip6h = ipv6_hdr(skb);
135		ip6h->hop_limit--;
136		neigh_table = NEIGH_ND_TABLE;
137		break;
138		}
139	default:
140		verdict = NFT_BREAK;
141		goto out;
142	}
143
144	dev = dev_get_by_index_rcu(nft_net(pkt), oif);
145	if (dev == NULL)
146		return;
147
148	skb->dev = dev;
149	skb_clear_tstamp(skb);
150	neigh_xmit(neigh_table, dev, addr, skb);
151out:
152	regs->verdict.code = verdict;
153}
154
155static int nft_fwd_neigh_init(const struct nft_ctx *ctx,
156			      const struct nft_expr *expr,
157			      const struct nlattr * const tb[])
158{
159	struct nft_fwd_neigh *priv = nft_expr_priv(expr);
160	unsigned int addr_len;
161	int err;
162
163	if (!tb[NFTA_FWD_SREG_DEV] ||
164	    !tb[NFTA_FWD_SREG_ADDR] ||
165	    !tb[NFTA_FWD_NFPROTO])
166		return -EINVAL;
167
168	priv->nfproto = ntohl(nla_get_be32(tb[NFTA_FWD_NFPROTO]));
169
170	switch (priv->nfproto) {
171	case NFPROTO_IPV4:
172		addr_len = sizeof(struct in_addr);
173		break;
174	case NFPROTO_IPV6:
175		addr_len = sizeof(struct in6_addr);
176		break;
177	default:
178		return -EOPNOTSUPP;
179	}
180
181	err = nft_parse_register_load(ctx, tb[NFTA_FWD_SREG_DEV], &priv->sreg_dev,
182				      sizeof(int));
183	if (err < 0)
184		return err;
185
186	return nft_parse_register_load(ctx, tb[NFTA_FWD_SREG_ADDR], &priv->sreg_addr,
187				       addr_len);
188}
189
190static int nft_fwd_neigh_dump(struct sk_buff *skb,
191			      const struct nft_expr *expr, bool reset)
192{
193	struct nft_fwd_neigh *priv = nft_expr_priv(expr);
194
195	if (nft_dump_register(skb, NFTA_FWD_SREG_DEV, priv->sreg_dev) ||
196	    nft_dump_register(skb, NFTA_FWD_SREG_ADDR, priv->sreg_addr) ||
197	    nla_put_be32(skb, NFTA_FWD_NFPROTO, htonl(priv->nfproto)))
198		goto nla_put_failure;
199
200	return 0;
201
202nla_put_failure:
203	return -1;
204}
205
206static int nft_fwd_validate(const struct nft_ctx *ctx,
207			    const struct nft_expr *expr)
208{
209	return nft_chain_validate_hooks(ctx->chain, (1 << NF_NETDEV_INGRESS) |
210						    (1 << NF_NETDEV_EGRESS));
211}
212
213static struct nft_expr_type nft_fwd_netdev_type;
214static const struct nft_expr_ops nft_fwd_neigh_netdev_ops = {
215	.type		= &nft_fwd_netdev_type,
216	.size		= NFT_EXPR_SIZE(sizeof(struct nft_fwd_neigh)),
217	.eval		= nft_fwd_neigh_eval,
218	.init		= nft_fwd_neigh_init,
219	.dump		= nft_fwd_neigh_dump,
220	.validate	= nft_fwd_validate,
221	.reduce		= NFT_REDUCE_READONLY,
222};
223
224static const struct nft_expr_ops nft_fwd_netdev_ops = {
225	.type		= &nft_fwd_netdev_type,
226	.size		= NFT_EXPR_SIZE(sizeof(struct nft_fwd_netdev)),
227	.eval		= nft_fwd_netdev_eval,
228	.init		= nft_fwd_netdev_init,
229	.dump		= nft_fwd_netdev_dump,
230	.validate	= nft_fwd_validate,
231	.reduce		= NFT_REDUCE_READONLY,
232	.offload	= nft_fwd_netdev_offload,
233	.offload_action	= nft_fwd_netdev_offload_action,
234};
235
236static const struct nft_expr_ops *
237nft_fwd_select_ops(const struct nft_ctx *ctx,
238		   const struct nlattr * const tb[])
239{
240	if (tb[NFTA_FWD_SREG_ADDR])
241		return &nft_fwd_neigh_netdev_ops;
242	if (tb[NFTA_FWD_SREG_DEV])
243		return &nft_fwd_netdev_ops;
244
245        return ERR_PTR(-EOPNOTSUPP);
246}
247
248static struct nft_expr_type nft_fwd_netdev_type __read_mostly = {
249	.family		= NFPROTO_NETDEV,
250	.name		= "fwd",
251	.select_ops	= nft_fwd_select_ops,
252	.policy		= nft_fwd_netdev_policy,
253	.maxattr	= NFTA_FWD_MAX,
254	.owner		= THIS_MODULE,
255};
256
257static int __init nft_fwd_netdev_module_init(void)
258{
259	return nft_register_expr(&nft_fwd_netdev_type);
260}
261
262static void __exit nft_fwd_netdev_module_exit(void)
263{
264	nft_unregister_expr(&nft_fwd_netdev_type);
265}
266
267module_init(nft_fwd_netdev_module_init);
268module_exit(nft_fwd_netdev_module_exit);
269
270MODULE_LICENSE("GPL");
271MODULE_AUTHOR("Pablo Neira Ayuso <pablo@netfilter.org>");
272MODULE_DESCRIPTION("nftables netdev packet forwarding support");
273MODULE_ALIAS_NFT_AF_EXPR(5, "fwd");