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764d8a9f PM |
1 | /* |
2 | * IP6 tables REJECT target module | |
3 | * Linux INET6 implementation | |
4 | * | |
5 | * Copyright (C)2003 USAGI/WIDE Project | |
6 | * | |
7 | * Authors: | |
8 | * Yasuyuki Kozakai <yasuyuki.kozakai@toshiba.co.jp> | |
9 | * | |
10 | * Based on net/ipv4/netfilter/ipt_REJECT.c | |
11 | * | |
12 | * This program is free software; you can redistribute it and/or | |
13 | * modify it under the terms of the GNU General Public License | |
14 | * as published by the Free Software Foundation; either version | |
15 | * 2 of the License, or (at your option) any later version. | |
16 | */ | |
17 | ||
764d8a9f PM |
18 | #include <linux/module.h> |
19 | #include <linux/skbuff.h> | |
20 | #include <linux/icmpv6.h> | |
21 | #include <linux/netdevice.h> | |
22 | #include <net/ipv6.h> | |
23 | #include <net/tcp.h> | |
24 | #include <net/icmp.h> | |
25 | #include <net/ip6_checksum.h> | |
26 | #include <net/ip6_fib.h> | |
27 | #include <net/ip6_route.h> | |
28 | #include <net/flow.h> | |
6709dbbb | 29 | #include <linux/netfilter/x_tables.h> |
764d8a9f PM |
30 | #include <linux/netfilter_ipv6/ip6_tables.h> |
31 | #include <linux/netfilter_ipv6/ip6t_REJECT.h> | |
32 | ||
33 | MODULE_AUTHOR("Yasuyuki KOZAKAI <yasuyuki.kozakai@toshiba.co.jp>"); | |
34 | MODULE_DESCRIPTION("IP6 tables REJECT target module"); | |
35 | MODULE_LICENSE("GPL"); | |
36 | ||
764d8a9f PM |
37 | /* Send RST reply */ |
38 | static void send_reset(struct sk_buff *oldskb) | |
39 | { | |
40 | struct sk_buff *nskb; | |
41 | struct tcphdr otcph, *tcph; | |
42 | unsigned int otcplen, hh_len; | |
43 | int tcphoff, needs_ack; | |
0660e03f | 44 | struct ipv6hdr *oip6h = ipv6_hdr(oldskb), *ip6h; |
764d8a9f PM |
45 | struct dst_entry *dst = NULL; |
46 | u8 proto; | |
47 | struct flowi fl; | |
48 | ||
49 | if ((!(ipv6_addr_type(&oip6h->saddr) & IPV6_ADDR_UNICAST)) || | |
50 | (!(ipv6_addr_type(&oip6h->daddr) & IPV6_ADDR_UNICAST))) { | |
0d53778e | 51 | pr_debug("ip6t_REJECT: addr is not unicast.\n"); |
764d8a9f PM |
52 | return; |
53 | } | |
54 | ||
55 | proto = oip6h->nexthdr; | |
56 | tcphoff = ipv6_skip_exthdr(oldskb, ((u8*)(oip6h+1) - oldskb->data), &proto); | |
57 | ||
58 | if ((tcphoff < 0) || (tcphoff > oldskb->len)) { | |
0d53778e | 59 | pr_debug("ip6t_REJECT: Can't get TCP header.\n"); |
764d8a9f PM |
60 | return; |
61 | } | |
62 | ||
63 | otcplen = oldskb->len - tcphoff; | |
64 | ||
65 | /* IP header checks: fragment, too short. */ | |
7c4e36bc | 66 | if (proto != IPPROTO_TCP || otcplen < sizeof(struct tcphdr)) { |
0d53778e PM |
67 | pr_debug("ip6t_REJECT: proto(%d) != IPPROTO_TCP, " |
68 | "or too short. otcplen = %d\n", | |
69 | proto, otcplen); | |
764d8a9f PM |
70 | return; |
71 | } | |
72 | ||
73 | if (skb_copy_bits(oldskb, tcphoff, &otcph, sizeof(struct tcphdr))) | |
74 | BUG(); | |
75 | ||
76 | /* No RST for RST. */ | |
77 | if (otcph.rst) { | |
0d53778e | 78 | pr_debug("ip6t_REJECT: RST is set\n"); |
764d8a9f PM |
79 | return; |
80 | } | |
81 | ||
82 | /* Check checksum. */ | |
83 | if (csum_ipv6_magic(&oip6h->saddr, &oip6h->daddr, otcplen, IPPROTO_TCP, | |
84 | skb_checksum(oldskb, tcphoff, otcplen, 0))) { | |
0d53778e | 85 | pr_debug("ip6t_REJECT: TCP checksum is invalid\n"); |
764d8a9f PM |
86 | return; |
87 | } | |
88 | ||
89 | memset(&fl, 0, sizeof(fl)); | |
90 | fl.proto = IPPROTO_TCP; | |
91 | ipv6_addr_copy(&fl.fl6_src, &oip6h->daddr); | |
92 | ipv6_addr_copy(&fl.fl6_dst, &oip6h->saddr); | |
93 | fl.fl_ip_sport = otcph.dest; | |
94 | fl.fl_ip_dport = otcph.source; | |
beb8d13b | 95 | security_skb_classify_flow(oldskb, &fl); |
764d8a9f PM |
96 | dst = ip6_route_output(NULL, &fl); |
97 | if (dst == NULL) | |
98 | return; | |
e104411b | 99 | if (dst->error || xfrm_lookup(&dst, &fl, NULL, 0)) |
764d8a9f | 100 | return; |
764d8a9f PM |
101 | |
102 | hh_len = (dst->dev->hard_header_len + 15)&~15; | |
103 | nskb = alloc_skb(hh_len + 15 + dst->header_len + sizeof(struct ipv6hdr) | |
104 | + sizeof(struct tcphdr) + dst->trailer_len, | |
105 | GFP_ATOMIC); | |
106 | ||
107 | if (!nskb) { | |
108 | if (net_ratelimit()) | |
109 | printk("ip6t_REJECT: Can't alloc skb\n"); | |
110 | dst_release(dst); | |
111 | return; | |
112 | } | |
113 | ||
114 | nskb->dst = dst; | |
115 | ||
116 | skb_reserve(nskb, hh_len + dst->header_len); | |
117 | ||
1ced98e8 ACM |
118 | skb_put(nskb, sizeof(struct ipv6hdr)); |
119 | skb_reset_network_header(nskb); | |
0660e03f | 120 | ip6h = ipv6_hdr(nskb); |
764d8a9f PM |
121 | ip6h->version = 6; |
122 | ip6h->hop_limit = dst_metric(dst, RTAX_HOPLIMIT); | |
123 | ip6h->nexthdr = IPPROTO_TCP; | |
764d8a9f PM |
124 | ipv6_addr_copy(&ip6h->saddr, &oip6h->daddr); |
125 | ipv6_addr_copy(&ip6h->daddr, &oip6h->saddr); | |
126 | ||
127 | tcph = (struct tcphdr *)skb_put(nskb, sizeof(struct tcphdr)); | |
128 | /* Truncate to length (no data) */ | |
129 | tcph->doff = sizeof(struct tcphdr)/4; | |
130 | tcph->source = otcph.dest; | |
131 | tcph->dest = otcph.source; | |
132 | ||
133 | if (otcph.ack) { | |
134 | needs_ack = 0; | |
135 | tcph->seq = otcph.ack_seq; | |
136 | tcph->ack_seq = 0; | |
137 | } else { | |
138 | needs_ack = 1; | |
139 | tcph->ack_seq = htonl(ntohl(otcph.seq) + otcph.syn + otcph.fin | |
140 | + otcplen - (otcph.doff<<2)); | |
141 | tcph->seq = 0; | |
142 | } | |
143 | ||
144 | /* Reset flags */ | |
145 | ((u_int8_t *)tcph)[13] = 0; | |
146 | tcph->rst = 1; | |
147 | tcph->ack = needs_ack; | |
148 | tcph->window = 0; | |
149 | tcph->urg_ptr = 0; | |
150 | tcph->check = 0; | |
151 | ||
152 | /* Adjust TCP checksum */ | |
0660e03f ACM |
153 | tcph->check = csum_ipv6_magic(&ipv6_hdr(nskb)->saddr, |
154 | &ipv6_hdr(nskb)->daddr, | |
764d8a9f | 155 | sizeof(struct tcphdr), IPPROTO_TCP, |
a47362a2 | 156 | csum_partial(tcph, |
764d8a9f PM |
157 | sizeof(struct tcphdr), 0)); |
158 | ||
08857fa7 YK |
159 | nf_ct_attach(nskb, oldskb); |
160 | ||
ef76bc23 | 161 | ip6_local_out(nskb); |
764d8a9f PM |
162 | } |
163 | ||
164 | static inline void | |
165 | send_unreach(struct sk_buff *skb_in, unsigned char code, unsigned int hooknum) | |
166 | { | |
6e23ae2a | 167 | if (hooknum == NF_INET_LOCAL_OUT && skb_in->dev == NULL) |
2774c7ab | 168 | skb_in->dev = init_net.loopback_dev; |
764d8a9f PM |
169 | |
170 | icmpv6_send(skb_in, ICMPV6_DEST_UNREACH, code, 0, NULL); | |
171 | } | |
172 | ||
3db05fea | 173 | static unsigned int reject6_target(struct sk_buff *skb, |
764d8a9f PM |
174 | const struct net_device *in, |
175 | const struct net_device *out, | |
176 | unsigned int hooknum, | |
c4986734 | 177 | const struct xt_target *target, |
fe1cb108 | 178 | const void *targinfo) |
764d8a9f PM |
179 | { |
180 | const struct ip6t_reject_info *reject = targinfo; | |
181 | ||
0d53778e | 182 | pr_debug("%s: medium point\n", __FUNCTION__); |
764d8a9f PM |
183 | /* WARNING: This code causes reentry within ip6tables. |
184 | This means that the ip6tables jump stack is now crap. We | |
185 | must return an absolute verdict. --RR */ | |
1ab1457c YH |
186 | switch (reject->with) { |
187 | case IP6T_ICMP6_NO_ROUTE: | |
3db05fea | 188 | send_unreach(skb, ICMPV6_NOROUTE, hooknum); |
1ab1457c YH |
189 | break; |
190 | case IP6T_ICMP6_ADM_PROHIBITED: | |
3db05fea | 191 | send_unreach(skb, ICMPV6_ADM_PROHIBITED, hooknum); |
1ab1457c YH |
192 | break; |
193 | case IP6T_ICMP6_NOT_NEIGHBOUR: | |
3db05fea | 194 | send_unreach(skb, ICMPV6_NOT_NEIGHBOUR, hooknum); |
1ab1457c YH |
195 | break; |
196 | case IP6T_ICMP6_ADDR_UNREACH: | |
3db05fea | 197 | send_unreach(skb, ICMPV6_ADDR_UNREACH, hooknum); |
1ab1457c YH |
198 | break; |
199 | case IP6T_ICMP6_PORT_UNREACH: | |
3db05fea | 200 | send_unreach(skb, ICMPV6_PORT_UNREACH, hooknum); |
1ab1457c YH |
201 | break; |
202 | case IP6T_ICMP6_ECHOREPLY: | |
764d8a9f PM |
203 | /* Do nothing */ |
204 | break; | |
205 | case IP6T_TCP_RESET: | |
3db05fea | 206 | send_reset(skb); |
764d8a9f PM |
207 | break; |
208 | default: | |
209 | if (net_ratelimit()) | |
210 | printk(KERN_WARNING "ip6t_REJECT: case %u not handled yet\n", reject->with); | |
211 | break; | |
212 | } | |
213 | ||
214 | return NF_DROP; | |
215 | } | |
216 | ||
e1931b78 JE |
217 | static bool check(const char *tablename, |
218 | const void *entry, | |
219 | const struct xt_target *target, | |
220 | void *targinfo, | |
221 | unsigned int hook_mask) | |
764d8a9f | 222 | { |
1ab1457c | 223 | const struct ip6t_reject_info *rejinfo = targinfo; |
2e4e6a17 | 224 | const struct ip6t_entry *e = entry; |
764d8a9f | 225 | |
764d8a9f PM |
226 | if (rejinfo->with == IP6T_ICMP6_ECHOREPLY) { |
227 | printk("ip6t_REJECT: ECHOREPLY is not supported.\n"); | |
e1931b78 | 228 | return false; |
764d8a9f PM |
229 | } else if (rejinfo->with == IP6T_TCP_RESET) { |
230 | /* Must specify that it's a TCP packet */ | |
231 | if (e->ipv6.proto != IPPROTO_TCP | |
6709dbbb | 232 | || (e->ipv6.invflags & XT_INV_PROTO)) { |
0d53778e | 233 | printk("ip6t_REJECT: TCP_RESET illegal for non-tcp\n"); |
e1931b78 | 234 | return false; |
764d8a9f PM |
235 | } |
236 | } | |
e1931b78 | 237 | return true; |
764d8a9f PM |
238 | } |
239 | ||
9f15c530 | 240 | static struct xt_target ip6t_reject_reg __read_mostly = { |
764d8a9f | 241 | .name = "REJECT", |
6709dbbb | 242 | .family = AF_INET6, |
764d8a9f | 243 | .target = reject6_target, |
7f939713 PM |
244 | .targetsize = sizeof(struct ip6t_reject_info), |
245 | .table = "filter", | |
6e23ae2a PM |
246 | .hooks = (1 << NF_INET_LOCAL_IN) | (1 << NF_INET_FORWARD) | |
247 | (1 << NF_INET_LOCAL_OUT), | |
764d8a9f PM |
248 | .checkentry = check, |
249 | .me = THIS_MODULE | |
250 | }; | |
251 | ||
65b4b4e8 | 252 | static int __init ip6t_reject_init(void) |
764d8a9f | 253 | { |
6709dbbb | 254 | return xt_register_target(&ip6t_reject_reg); |
764d8a9f PM |
255 | } |
256 | ||
65b4b4e8 | 257 | static void __exit ip6t_reject_fini(void) |
764d8a9f | 258 | { |
6709dbbb | 259 | xt_unregister_target(&ip6t_reject_reg); |
764d8a9f PM |
260 | } |
261 | ||
65b4b4e8 AM |
262 | module_init(ip6t_reject_init); |
263 | module_exit(ip6t_reject_fini); |