[linux-block.git] / net / netfilter / nft_reject_netdev.c

// SPDX-License-Identifier: GPL-2.0-only
/*
 * Copyright (c) 2020 Laura Garcia Liebana <nevola@gmail.com>
 * Copyright (c) 2020 Jose M. Guisado <guigom@riseup.net>
 */

#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/module.h>
#include <linux/netlink.h>
#include <linux/netfilter.h>
#include <linux/netfilter/nf_tables.h>
#include <net/netfilter/nf_tables.h>
#include <net/netfilter/nft_reject.h>
#include <net/netfilter/ipv4/nf_reject.h>
#include <net/netfilter/ipv6/nf_reject.h>

static void nft_reject_queue_xmit(struct sk_buff *nskb, struct sk_buff *oldskb)
{
	dev_hard_header(nskb, nskb->dev, ntohs(oldskb->protocol),
			eth_hdr(oldskb)->h_source, eth_hdr(oldskb)->h_dest,
			nskb->len);
	dev_queue_xmit(nskb);
}

static void nft_reject_netdev_send_v4_tcp_reset(struct net *net,
						struct sk_buff *oldskb,
						const struct net_device *dev,
						int hook)
{
	struct sk_buff *nskb;

	nskb = nf_reject_skb_v4_tcp_reset(net, oldskb, dev, hook);
	if (!nskb)
		return;

	nft_reject_queue_xmit(nskb, oldskb);
}

static void nft_reject_netdev_send_v4_unreach(struct net *net,
					      struct sk_buff *oldskb,
					      const struct net_device *dev,
					      int hook, u8 code)
{
	struct sk_buff *nskb;

	nskb = nf_reject_skb_v4_unreach(net, oldskb, dev, hook, code);
	if (!nskb)
		return;

	nft_reject_queue_xmit(nskb, oldskb);
}

static void nft_reject_netdev_send_v6_tcp_reset(struct net *net,
						struct sk_buff *oldskb,
						const struct net_device *dev,
						int hook)
{
	struct sk_buff *nskb;

	nskb = nf_reject_skb_v6_tcp_reset(net, oldskb, dev, hook);
	if (!nskb)
		return;

	nft_reject_queue_xmit(nskb, oldskb);
}


static void nft_reject_netdev_send_v6_unreach(struct net *net,
					      struct sk_buff *oldskb,
					      const struct net_device *dev,
					      int hook, u8 code)
{
	struct sk_buff *nskb;

	nskb = nf_reject_skb_v6_unreach(net, oldskb, dev, hook, code);
	if (!nskb)
		return;

	nft_reject_queue_xmit(nskb, oldskb);
}

static void nft_reject_netdev_eval(const struct nft_expr *expr,
				   struct nft_regs *regs,
				   const struct nft_pktinfo *pkt)
{
	struct ethhdr *eth = eth_hdr(pkt->skb);
	struct nft_reject *priv = nft_expr_priv(expr);
	const unsigned char *dest = eth->h_dest;

	if (is_broadcast_ether_addr(dest) ||
	    is_multicast_ether_addr(dest))
		goto out;

	switch (eth->h_proto) {
	case htons(ETH_P_IP):
		switch (priv->type) {
		case NFT_REJECT_ICMP_UNREACH:
			nft_reject_netdev_send_v4_unreach(nft_net(pkt), pkt->skb,
							  nft_in(pkt),
							  nft_hook(pkt),
							  priv->icmp_code);
			break;
		case NFT_REJECT_TCP_RST:
			nft_reject_netdev_send_v4_tcp_reset(nft_net(pkt), pkt->skb,
							    nft_in(pkt),
							    nft_hook(pkt));
			break;
		case NFT_REJECT_ICMPX_UNREACH:
			nft_reject_netdev_send_v4_unreach(nft_net(pkt), pkt->skb,
							  nft_in(pkt),
							  nft_hook(pkt),
							  nft_reject_icmp_code(priv->icmp_code));
			break;
		}
		break;
	case htons(ETH_P_IPV6):
		switch (priv->type) {
		case NFT_REJECT_ICMP_UNREACH:
			nft_reject_netdev_send_v6_unreach(nft_net(pkt), pkt->skb,
							  nft_in(pkt),
							  nft_hook(pkt),
							  priv->icmp_code);
			break;
		case NFT_REJECT_TCP_RST:
			nft_reject_netdev_send_v6_tcp_reset(nft_net(pkt), pkt->skb,
							    nft_in(pkt),
							    nft_hook(pkt));
			break;
		case NFT_REJECT_ICMPX_UNREACH:
			nft_reject_netdev_send_v6_unreach(nft_net(pkt), pkt->skb,
							  nft_in(pkt),
							  nft_hook(pkt),
							  nft_reject_icmpv6_code(priv->icmp_code));
			break;
		}
		break;
	default:
		/* No explicit way to reject this protocol, drop it. */
		break;
	}
out:
	regs->verdict.code = NF_DROP;
}

static int nft_reject_netdev_validate(const struct nft_ctx *ctx,
				      const struct nft_expr *expr,
				      const struct nft_data **data)
{
	return nft_chain_validate_hooks(ctx->chain, (1 << NF_NETDEV_INGRESS));
}

static struct nft_expr_type nft_reject_netdev_type;
static const struct nft_expr_ops nft_reject_netdev_ops = {
	.type		= &nft_reject_netdev_type,
	.size		= NFT_EXPR_SIZE(sizeof(struct nft_reject)),
	.eval		= nft_reject_netdev_eval,
	.init		= nft_reject_init,
	.dump		= nft_reject_dump,
	.validate	= nft_reject_netdev_validate,
};

static struct nft_expr_type nft_reject_netdev_type __read_mostly = {
	.family		= NFPROTO_NETDEV,
	.name		= "reject",
	.ops		= &nft_reject_netdev_ops,
	.policy		= nft_reject_policy,
	.maxattr	= NFTA_REJECT_MAX,
	.owner		= THIS_MODULE,
};

static int __init nft_reject_netdev_module_init(void)
{
	return nft_register_expr(&nft_reject_netdev_type);
}

static void __exit nft_reject_netdev_module_exit(void)
{
	nft_unregister_expr(&nft_reject_netdev_type);
}

module_init(nft_reject_netdev_module_init);
module_exit(nft_reject_netdev_module_exit);

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Laura Garcia Liebana <nevola@gmail.com>");
MODULE_AUTHOR("Jose M. Guisado <guigom@riseup.net>");
MODULE_DESCRIPTION("Reject packets from netdev via nftables");
MODULE_ALIAS_NFT_AF_EXPR(5, "reject");
Commit	Line	Data
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");