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
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>
29 #include <linux/netfilter/x_tables.h>
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("Xtables: packet \"rejection\" target for IPv6");
35 MODULE_LICENSE("GPL");
36
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;
44 struct ipv6hdr *oip6h = ipv6_hdr(oldskb), *ip6h;
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))) {
51 pr_debug("ip6t_REJECT: addr is not unicast.\n");
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)) {
59 pr_debug("ip6t_REJECT: Can't get TCP header.\n");
60 return;
61 }
62
63 otcplen = oldskb->len - tcphoff;
64
65 /* IP header checks: fragment, too short. */
66 if (proto != IPPROTO_TCP || otcplen < sizeof(struct tcphdr)) {
67 pr_debug("ip6t_REJECT: proto(%d) != IPPROTO_TCP, "
68 "or too short. otcplen = %d\n",
69 proto, otcplen);
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) {
78 pr_debug("ip6t_REJECT: RST is set\n");
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))) {
85 pr_debug("ip6t_REJECT: TCP checksum is invalid\n");
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;
95 security_skb_classify_flow(oldskb, &fl);
96 dst = ip6_route_output(NULL, &fl);
97 if (dst == NULL)
98 return;
99 if (dst->error || xfrm_lookup(&dst, &fl, NULL, 0))
100 return;
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
118 skb_put(nskb, sizeof(struct ipv6hdr));
119 skb_reset_network_header(nskb);
120 ip6h = ipv6_hdr(nskb);
121 ip6h->version = 6;
122 ip6h->hop_limit = dst_metric(dst, RTAX_HOPLIMIT);
123 ip6h->nexthdr = IPPROTO_TCP;
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 */
153 tcph->check = csum_ipv6_magic(&ipv6_hdr(nskb)->saddr,
154 &ipv6_hdr(nskb)->daddr,
155 sizeof(struct tcphdr), IPPROTO_TCP,
156 csum_partial(tcph,
157 sizeof(struct tcphdr), 0));
158
159 nf_ct_attach(nskb, oldskb);
160
161 ip6_local_out(nskb);
162 }
163
164 static inline void
165 send_unreach(struct sk_buff *skb_in, unsigned char code, unsigned int hooknum)
166 {
167 if (hooknum == NF_INET_LOCAL_OUT && skb_in->dev == NULL)
168 skb_in->dev = init_net.loopback_dev;
169
170 icmpv6_send(skb_in, ICMPV6_DEST_UNREACH, code, 0, NULL);
171 }
172
173 static unsigned int
174 reject_tg6(struct sk_buff *skb, const struct net_device *in,
175 const struct net_device *out, unsigned int hooknum,
176 const struct xt_target *target, const void *targinfo)
177 {
178 const struct ip6t_reject_info *reject = targinfo;
179
180 pr_debug("%s: medium point\n", __FUNCTION__);
181 /* WARNING: This code causes reentry within ip6tables.
182 This means that the ip6tables jump stack is now crap. We
183 must return an absolute verdict. --RR */
184 switch (reject->with) {
185 case IP6T_ICMP6_NO_ROUTE:
186 send_unreach(skb, ICMPV6_NOROUTE, hooknum);
187 break;
188 case IP6T_ICMP6_ADM_PROHIBITED:
189 send_unreach(skb, ICMPV6_ADM_PROHIBITED, hooknum);
190 break;
191 case IP6T_ICMP6_NOT_NEIGHBOUR:
192 send_unreach(skb, ICMPV6_NOT_NEIGHBOUR, hooknum);
193 break;
194 case IP6T_ICMP6_ADDR_UNREACH:
195 send_unreach(skb, ICMPV6_ADDR_UNREACH, hooknum);
196 break;
197 case IP6T_ICMP6_PORT_UNREACH:
198 send_unreach(skb, ICMPV6_PORT_UNREACH, hooknum);
199 break;
200 case IP6T_ICMP6_ECHOREPLY:
201 /* Do nothing */
202 break;
203 case IP6T_TCP_RESET:
204 send_reset(skb);
205 break;
206 default:
207 if (net_ratelimit())
208 printk(KERN_WARNING "ip6t_REJECT: case %u not handled yet\n", reject->with);
209 break;
210 }
211
212 return NF_DROP;
213 }
214
215 static bool
216 reject_tg6_check(const char *tablename, const void *entry,
217 const struct xt_target *target, void *targinfo,
218 unsigned int hook_mask)
219 {
220 const struct ip6t_reject_info *rejinfo = targinfo;
221 const struct ip6t_entry *e = entry;
222
223 if (rejinfo->with == IP6T_ICMP6_ECHOREPLY) {
224 printk("ip6t_REJECT: ECHOREPLY is not supported.\n");
225 return false;
226 } else if (rejinfo->with == IP6T_TCP_RESET) {
227 /* Must specify that it's a TCP packet */
228 if (e->ipv6.proto != IPPROTO_TCP
229 || (e->ipv6.invflags & XT_INV_PROTO)) {
230 printk("ip6t_REJECT: TCP_RESET illegal for non-tcp\n");
231 return false;
232 }
233 }
234 return true;
235 }
236
237 static struct xt_target reject_tg6_reg __read_mostly = {
238 .name = "REJECT",
239 .family = AF_INET6,
240 .target = reject_tg6,
241 .targetsize = sizeof(struct ip6t_reject_info),
242 .table = "filter",
243 .hooks = (1 << NF_INET_LOCAL_IN) | (1 << NF_INET_FORWARD) |
244 (1 << NF_INET_LOCAL_OUT),
245 .checkentry = reject_tg6_check,
246 .me = THIS_MODULE
247 };
248
249 static int __init reject_tg6_init(void)
250 {
251 return xt_register_target(&reject_tg6_reg);
252 }
253
254 static void __exit reject_tg6_exit(void)
255 {
256 xt_unregister_target(&reject_tg6_reg);
257 }
258
259 module_init(reject_tg6_init);
260 module_exit(reject_tg6_exit);
261
|
This page was automatically generated by the
LXR engine.
|