summaryrefslogtreecommitdiff
path: root/net/ipv6/netfilter/ip6t_REJECT.c
blob: dd8afbaf00a8fe84ee317087e1c4e7dc3703ee34 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
/*
 * IP6 tables REJECT target module
 * Linux INET6 implementation
 *
 * Copyright (C)2003 USAGI/WIDE Project
 *
 * Authors:
 *	Yasuyuki Kozakai	<yasuyuki.kozakai@toshiba.co.jp>
 *
 * Based on net/ipv4/netfilter/ipt_REJECT.c
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version
 * 2 of the License, or (at your option) any later version.
 */

#include <linux/module.h>
#include <linux/skbuff.h>
#include <linux/icmpv6.h>
#include <linux/netdevice.h>
#include <net/ipv6.h>
#include <net/tcp.h>
#include <net/icmp.h>
#include <net/ip6_checksum.h>
#include <net/ip6_fib.h>
#include <net/ip6_route.h>
#include <net/flow.h>
#include <linux/netfilter/x_tables.h>
#include <linux/netfilter_ipv6/ip6_tables.h>
#include <linux/netfilter_ipv6/ip6t_REJECT.h>

MODULE_AUTHOR("Yasuyuki KOZAKAI <yasuyuki.kozakai@toshiba.co.jp>");
MODULE_DESCRIPTION("Xtables: packet \"rejection\" target for IPv6");
MODULE_LICENSE("GPL");

/* Send RST reply */
static void send_reset(struct net *net, struct sk_buff *oldskb)
{
	struct sk_buff *nskb;
	struct tcphdr otcph, *tcph;
	unsigned int otcplen, hh_len;
	int tcphoff, needs_ack;
	const struct ipv6hdr *oip6h = ipv6_hdr(oldskb);
	struct ipv6hdr *ip6h;
	struct dst_entry *dst = NULL;
	u8 proto;
	struct flowi fl;

	if ((!(ipv6_addr_type(&oip6h->saddr) & IPV6_ADDR_UNICAST)) ||
	    (!(ipv6_addr_type(&oip6h->daddr) & IPV6_ADDR_UNICAST))) {
		pr_debug("ip6t_REJECT: addr is not unicast.\n");
		return;
	}

	proto = oip6h->nexthdr;
	tcphoff = ipv6_skip_exthdr(oldskb, ((u8*)(oip6h+1) - oldskb->data), &proto);

	if ((tcphoff < 0) || (tcphoff > oldskb->len)) {
		pr_debug("ip6t_REJECT: Can't get TCP header.\n");
		return;
	}

	otcplen = oldskb->len - tcphoff;

	/* IP header checks: fragment, too short. */
	if (proto != IPPROTO_TCP || otcplen < sizeof(struct tcphdr)) {
		pr_debug("ip6t_REJECT: proto(%d) != IPPROTO_TCP, "
			 "or too short. otcplen = %d\n",
			 proto, otcplen);
		return;
	}

	if (skb_copy_bits(oldskb, tcphoff, &otcph, sizeof(struct tcphdr)))
		BUG();

	/* No RST for RST. */
	if (otcph.rst) {
		pr_debug("ip6t_REJECT: RST is set\n");
		return;
	}

	/* Check checksum. */
	if (csum_ipv6_magic(&oip6h->saddr, &oip6h->daddr, otcplen, IPPROTO_TCP,
			    skb_checksum(oldskb, tcphoff, otcplen, 0))) {
		pr_debug("ip6t_REJECT: TCP checksum is invalid\n");
		return;
	}

	memset(&fl, 0, sizeof(fl));
	fl.proto = IPPROTO_TCP;
	ipv6_addr_copy(&fl.fl6_src, &oip6h->daddr);
	ipv6_addr_copy(&fl.fl6_dst, &oip6h->saddr);
	fl.fl_ip_sport = otcph.dest;
	fl.fl_ip_dport = otcph.source;
	security_skb_classify_flow(oldskb, &fl);
	dst = ip6_route_output(net, NULL, &fl);
	if (dst == NULL)
		return;
	if (dst->error || xfrm_lookup(net, &dst, &fl, NULL, 0))
		return;

	hh_len = (dst->dev->hard_header_len + 15)&~15;
	nskb = alloc_skb(hh_len + 15 + dst->header_len + sizeof(struct ipv6hdr)
			 + sizeof(struct tcphdr) + dst->trailer_len,
			 GFP_ATOMIC);

	if (!nskb) {
		if (net_ratelimit())
			printk("ip6t_REJECT: Can't alloc skb\n");
		dst_release(dst);
		return;
	}

	skb_dst_set(nskb, dst);

	skb_reserve(nskb, hh_len + dst->header_len);

	skb_put(nskb, sizeof(struct ipv6hdr));
	skb_reset_network_header(nskb);
	ip6h = ipv6_hdr(nskb);
	ip6h->version = 6;
	ip6h->hop_limit = dst_metric(dst, RTAX_HOPLIMIT);
	ip6h->nexthdr = IPPROTO_TCP;
	ipv6_addr_copy(&ip6h->saddr, &oip6h->daddr);
	ipv6_addr_copy(&ip6h->daddr, &oip6h->saddr);

	tcph = (struct tcphdr *)skb_put(nskb, sizeof(struct tcphdr));
	/* Truncate to length (no data) */
	tcph->doff = sizeof(struct tcphdr)/4;
	tcph->source = otcph.dest;
	tcph->dest = otcph.source;

	if (otcph.ack) {
		needs_ack = 0;
		tcph->seq = otcph.ack_seq;
		tcph->ack_seq = 0;
	} else {
		needs_ack = 1;
		tcph->ack_seq = htonl(ntohl(otcph.seq) + otcph.syn + otcph.fin
				      + otcplen - (otcph.doff<<2));
		tcph->seq = 0;
	}

	/* Reset flags */
	((u_int8_t *)tcph)[13] = 0;
	tcph->rst = 1;
	tcph->ack = needs_ack;
	tcph->window = 0;
	tcph->urg_ptr = 0;
	tcph->check = 0;

	/* Adjust TCP checksum */
	tcph->check = csum_ipv6_magic(&ipv6_hdr(nskb)->saddr,
				      &ipv6_hdr(nskb)->daddr,
				      sizeof(struct tcphdr), IPPROTO_TCP,
				      csum_partial(tcph,
						   sizeof(struct tcphdr), 0));

	nf_ct_attach(nskb, oldskb);

	ip6_local_out(nskb);
}

static inline void
send_unreach(struct net *net, struct sk_buff *skb_in, unsigned char code,
	     unsigned int hooknum)
{
	if (hooknum == NF_INET_LOCAL_OUT && skb_in->dev == NULL)
		skb_in->dev = net->loopback_dev;

	icmpv6_send(skb_in, ICMPV6_DEST_UNREACH, code, 0);
}

static unsigned int
reject_tg6(struct sk_buff *skb, const struct xt_target_param *par)
{
	const struct ip6t_reject_info *reject = par->targinfo;
	struct net *net = dev_net((par->in != NULL) ? par->in : par->out);

	pr_debug("%s: medium point\n", __func__);
	/* WARNING: This code causes reentry within ip6tables.
	   This means that the ip6tables jump stack is now crap.  We
	   must return an absolute verdict. --RR */
	switch (reject->with) {
	case IP6T_ICMP6_NO_ROUTE:
		send_unreach(net, skb, ICMPV6_NOROUTE, par->hooknum);
		break;
	case IP6T_ICMP6_ADM_PROHIBITED:
		send_unreach(net, skb, ICMPV6_ADM_PROHIBITED, par->hooknum);
		break;
	case IP6T_ICMP6_NOT_NEIGHBOUR:
		send_unreach(net, skb, ICMPV6_NOT_NEIGHBOUR, par->hooknum);
		break;
	case IP6T_ICMP6_ADDR_UNREACH:
		send_unreach(net, skb, ICMPV6_ADDR_UNREACH, par->hooknum);
		break;
	case IP6T_ICMP6_PORT_UNREACH:
		send_unreach(net, skb, ICMPV6_PORT_UNREACH, par->hooknum);
		break;
	case IP6T_ICMP6_ECHOREPLY:
		/* Do nothing */
		break;
	case IP6T_TCP_RESET:
		send_reset(net, skb);
		break;
	default:
		if (net_ratelimit())
			printk(KERN_WARNING "ip6t_REJECT: case %u not handled yet\n", reject->with);
		break;
	}

	return NF_DROP;
}

static bool reject_tg6_check(const struct xt_tgchk_param *par)
{
	const struct ip6t_reject_info *rejinfo = par->targinfo;
	const struct ip6t_entry *e = par->entryinfo;

	if (rejinfo->with == IP6T_ICMP6_ECHOREPLY) {
		printk("ip6t_REJECT: ECHOREPLY is not supported.\n");
		return false;
	} else if (rejinfo->with == IP6T_TCP_RESET) {
		/* Must specify that it's a TCP packet */
		if (e->ipv6.proto != IPPROTO_TCP ||
		    (e->ipv6.invflags & XT_INV_PROTO)) {
			printk("ip6t_REJECT: TCP_RESET illegal for non-tcp\n");
			return false;
		}
	}
	return true;
}

static struct xt_target reject_tg6_reg __read_mostly = {
	.name		= "REJECT",
	.family		= NFPROTO_IPV6,
	.target		= reject_tg6,
	.targetsize	= sizeof(struct ip6t_reject_info),
	.table		= "filter",
	.hooks		= (1 << NF_INET_LOCAL_IN) | (1 << NF_INET_FORWARD) |
			  (1 << NF_INET_LOCAL_OUT),
	.checkentry	= reject_tg6_check,
	.me		= THIS_MODULE
};

static int __init reject_tg6_init(void)
{
	return xt_register_target(&reject_tg6_reg);
}

static void __exit reject_tg6_exit(void)
{
	xt_unregister_target(&reject_tg6_reg);
}

module_init(reject_tg6_init);
module_exit(reject_tg6_exit);