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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
33MODULE_AUTHOR("Yasuyuki KOZAKAI <yasuyuki.kozakai@toshiba.co.jp>");
34MODULE_DESCRIPTION("Xtables: packet \"rejection\" target for IPv6");
35MODULE_LICENSE("GPL");
36
37
38static void send_reset(struct net *net, 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 const struct ipv6hdr *oip6h = ipv6_hdr(oldskb);
45 struct ipv6hdr *ip6h;
46 struct dst_entry *dst = NULL;
47 u8 proto;
48 struct flowi fl;
49
50 if ((!(ipv6_addr_type(&oip6h->saddr) & IPV6_ADDR_UNICAST)) ||
51 (!(ipv6_addr_type(&oip6h->daddr) & IPV6_ADDR_UNICAST))) {
52 pr_debug("ip6t_REJECT: addr is not unicast.\n");
53 return;
54 }
55
56 proto = oip6h->nexthdr;
57 tcphoff = ipv6_skip_exthdr(oldskb, ((u8*)(oip6h+1) - oldskb->data), &proto);
58
59 if ((tcphoff < 0) || (tcphoff > oldskb->len)) {
60 pr_debug("ip6t_REJECT: Can't get TCP header.\n");
61 return;
62 }
63
64 otcplen = oldskb->len - tcphoff;
65
66
67 if (proto != IPPROTO_TCP || otcplen < sizeof(struct tcphdr)) {
68 pr_debug("ip6t_REJECT: proto(%d) != IPPROTO_TCP, "
69 "or too short. otcplen = %d\n",
70 proto, otcplen);
71 return;
72 }
73
74 if (skb_copy_bits(oldskb, tcphoff, &otcph, sizeof(struct tcphdr)))
75 BUG();
76
77
78 if (otcph.rst) {
79 pr_debug("ip6t_REJECT: RST is set\n");
80 return;
81 }
82
83
84 if (csum_ipv6_magic(&oip6h->saddr, &oip6h->daddr, otcplen, IPPROTO_TCP,
85 skb_checksum(oldskb, tcphoff, otcplen, 0))) {
86 pr_debug("ip6t_REJECT: TCP checksum is invalid\n");
87 return;
88 }
89
90 memset(&fl, 0, sizeof(fl));
91 fl.proto = IPPROTO_TCP;
92 ipv6_addr_copy(&fl.fl6_src, &oip6h->daddr);
93 ipv6_addr_copy(&fl.fl6_dst, &oip6h->saddr);
94 fl.fl_ip_sport = otcph.dest;
95 fl.fl_ip_dport = otcph.source;
96 security_skb_classify_flow(oldskb, &fl);
97 dst = ip6_route_output(net, NULL, &fl);
98 if (dst == NULL)
99 return;
100 if (dst->error || xfrm_lookup(net, &dst, &fl, NULL, 0))
101 return;
102
103 hh_len = (dst->dev->hard_header_len + 15)&~15;
104 nskb = alloc_skb(hh_len + 15 + dst->header_len + sizeof(struct ipv6hdr)
105 + sizeof(struct tcphdr) + dst->trailer_len,
106 GFP_ATOMIC);
107
108 if (!nskb) {
109 if (net_ratelimit())
110 printk("ip6t_REJECT: Can't alloc skb\n");
111 dst_release(dst);
112 return;
113 }
114
115 skb_dst_set(nskb, dst);
116
117 skb_reserve(nskb, hh_len + dst->header_len);
118
119 skb_put(nskb, sizeof(struct ipv6hdr));
120 skb_reset_network_header(nskb);
121 ip6h = ipv6_hdr(nskb);
122 ip6h->version = 6;
123 ip6h->hop_limit = dst_metric(dst, RTAX_HOPLIMIT);
124 ip6h->nexthdr = IPPROTO_TCP;
125 ipv6_addr_copy(&ip6h->saddr, &oip6h->daddr);
126 ipv6_addr_copy(&ip6h->daddr, &oip6h->saddr);
127
128 tcph = (struct tcphdr *)skb_put(nskb, sizeof(struct tcphdr));
129
130 tcph->doff = sizeof(struct tcphdr)/4;
131 tcph->source = otcph.dest;
132 tcph->dest = otcph.source;
133
134 if (otcph.ack) {
135 needs_ack = 0;
136 tcph->seq = otcph.ack_seq;
137 tcph->ack_seq = 0;
138 } else {
139 needs_ack = 1;
140 tcph->ack_seq = htonl(ntohl(otcph.seq) + otcph.syn + otcph.fin
141 + otcplen - (otcph.doff<<2));
142 tcph->seq = 0;
143 }
144
145
146 ((u_int8_t *)tcph)[13] = 0;
147 tcph->rst = 1;
148 tcph->ack = needs_ack;
149 tcph->window = 0;
150 tcph->urg_ptr = 0;
151 tcph->check = 0;
152
153
154 tcph->check = csum_ipv6_magic(&ipv6_hdr(nskb)->saddr,
155 &ipv6_hdr(nskb)->daddr,
156 sizeof(struct tcphdr), IPPROTO_TCP,
157 csum_partial(tcph,
158 sizeof(struct tcphdr), 0));
159
160 nf_ct_attach(nskb, oldskb);
161
162 ip6_local_out(nskb);
163}
164
165static inline void
166send_unreach(struct net *net, struct sk_buff *skb_in, unsigned char code,
167 unsigned int hooknum)
168{
169 if (hooknum == NF_INET_LOCAL_OUT && skb_in->dev == NULL)
170 skb_in->dev = net->loopback_dev;
171
172 icmpv6_send(skb_in, ICMPV6_DEST_UNREACH, code, 0, NULL);
173}
174
175static unsigned int
176reject_tg6(struct sk_buff *skb, const struct xt_target_param *par)
177{
178 const struct ip6t_reject_info *reject = par->targinfo;
179 struct net *net = dev_net((par->in != NULL) ? par->in : par->out);
180
181 pr_debug("%s: medium point\n", __func__);
182
183
184
185 switch (reject->with) {
186 case IP6T_ICMP6_NO_ROUTE:
187 send_unreach(net, skb, ICMPV6_NOROUTE, par->hooknum);
188 break;
189 case IP6T_ICMP6_ADM_PROHIBITED:
190 send_unreach(net, skb, ICMPV6_ADM_PROHIBITED, par->hooknum);
191 break;
192 case IP6T_ICMP6_NOT_NEIGHBOUR:
193 send_unreach(net, skb, ICMPV6_NOT_NEIGHBOUR, par->hooknum);
194 break;
195 case IP6T_ICMP6_ADDR_UNREACH:
196 send_unreach(net, skb, ICMPV6_ADDR_UNREACH, par->hooknum);
197 break;
198 case IP6T_ICMP6_PORT_UNREACH:
199 send_unreach(net, skb, ICMPV6_PORT_UNREACH, par->hooknum);
200 break;
201 case IP6T_ICMP6_ECHOREPLY:
202
203 break;
204 case IP6T_TCP_RESET:
205 send_reset(net, skb);
206 break;
207 default:
208 if (net_ratelimit())
209 printk(KERN_WARNING "ip6t_REJECT: case %u not handled yet\n", reject->with);
210 break;
211 }
212
213 return NF_DROP;
214}
215
216static bool reject_tg6_check(const struct xt_tgchk_param *par)
217{
218 const struct ip6t_reject_info *rejinfo = par->targinfo;
219 const struct ip6t_entry *e = par->entryinfo;
220
221 if (rejinfo->with == IP6T_ICMP6_ECHOREPLY) {
222 printk("ip6t_REJECT: ECHOREPLY is not supported.\n");
223 return false;
224 } else if (rejinfo->with == IP6T_TCP_RESET) {
225
226 if (e->ipv6.proto != IPPROTO_TCP
227 || (e->ipv6.invflags & XT_INV_PROTO)) {
228 printk("ip6t_REJECT: TCP_RESET illegal for non-tcp\n");
229 return false;
230 }
231 }
232 return true;
233}
234
235static struct xt_target reject_tg6_reg __read_mostly = {
236 .name = "REJECT",
237 .family = NFPROTO_IPV6,
238 .target = reject_tg6,
239 .targetsize = sizeof(struct ip6t_reject_info),
240 .table = "filter",
241 .hooks = (1 << NF_INET_LOCAL_IN) | (1 << NF_INET_FORWARD) |
242 (1 << NF_INET_LOCAL_OUT),
243 .checkentry = reject_tg6_check,
244 .me = THIS_MODULE
245};
246
247static int __init reject_tg6_init(void)
248{
249 return xt_register_target(&reject_tg6_reg);
250}
251
252static void __exit reject_tg6_exit(void)
253{
254 xt_unregister_target(&reject_tg6_reg);
255}
256
257module_init(reject_tg6_init);
258module_exit(reject_tg6_exit);
259
