Merge branch 'core-iommu-for-linus' of git://git.kernel.org/pub/scm/linux/kernel...
[linux-2.6.git] / net / ipv6 / netfilter / ip6t_REJECT.c
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 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
18
19 #include <linux/gfp.h>
20 #include <linux/module.h>
21 #include <linux/skbuff.h>
22 #include <linux/icmpv6.h>
23 #include <linux/netdevice.h>
24 #include <net/ipv6.h>
25 #include <net/tcp.h>
26 #include <net/icmp.h>
27 #include <net/ip6_checksum.h>
28 #include <net/ip6_fib.h>
29 #include <net/ip6_route.h>
30 #include <net/flow.h>
31 #include <linux/netfilter/x_tables.h>
32 #include <linux/netfilter_ipv6/ip6_tables.h>
33 #include <linux/netfilter_ipv6/ip6t_REJECT.h>
34
35 MODULE_AUTHOR("Yasuyuki KOZAKAI <yasuyuki.kozakai@toshiba.co.jp>");
36 MODULE_DESCRIPTION("Xtables: packet \"rejection\" target for IPv6");
37 MODULE_LICENSE("GPL");
38
39 /* Send RST reply */
40 static void send_reset(struct net *net, struct sk_buff *oldskb)
41 {
42         struct sk_buff *nskb;
43         struct tcphdr otcph, *tcph;
44         unsigned int otcplen, hh_len;
45         int tcphoff, needs_ack;
46         const struct ipv6hdr *oip6h = ipv6_hdr(oldskb);
47         struct ipv6hdr *ip6h;
48 #define DEFAULT_TOS_VALUE       0x0U
49         const __u8 tclass = DEFAULT_TOS_VALUE;
50         struct dst_entry *dst = NULL;
51         u8 proto;
52         struct flowi6 fl6;
53
54         if ((!(ipv6_addr_type(&oip6h->saddr) & IPV6_ADDR_UNICAST)) ||
55             (!(ipv6_addr_type(&oip6h->daddr) & IPV6_ADDR_UNICAST))) {
56                 pr_debug("addr is not unicast.\n");
57                 return;
58         }
59
60         proto = oip6h->nexthdr;
61         tcphoff = ipv6_skip_exthdr(oldskb, ((u8*)(oip6h+1) - oldskb->data), &proto);
62
63         if ((tcphoff < 0) || (tcphoff > oldskb->len)) {
64                 pr_debug("Cannot get TCP header.\n");
65                 return;
66         }
67
68         otcplen = oldskb->len - tcphoff;
69
70         /* IP header checks: fragment, too short. */
71         if (proto != IPPROTO_TCP || otcplen < sizeof(struct tcphdr)) {
72                 pr_debug("proto(%d) != IPPROTO_TCP, "
73                          "or too short. otcplen = %d\n",
74                          proto, otcplen);
75                 return;
76         }
77
78         if (skb_copy_bits(oldskb, tcphoff, &otcph, sizeof(struct tcphdr)))
79                 BUG();
80
81         /* No RST for RST. */
82         if (otcph.rst) {
83                 pr_debug("RST is set\n");
84                 return;
85         }
86
87         /* Check checksum. */
88         if (csum_ipv6_magic(&oip6h->saddr, &oip6h->daddr, otcplen, IPPROTO_TCP,
89                             skb_checksum(oldskb, tcphoff, otcplen, 0))) {
90                 pr_debug("TCP checksum is invalid\n");
91                 return;
92         }
93
94         memset(&fl6, 0, sizeof(fl6));
95         fl6.flowi6_proto = IPPROTO_TCP;
96         ipv6_addr_copy(&fl6.saddr, &oip6h->daddr);
97         ipv6_addr_copy(&fl6.daddr, &oip6h->saddr);
98         fl6.fl6_sport = otcph.dest;
99         fl6.fl6_dport = otcph.source;
100         security_skb_classify_flow(oldskb, flowi6_to_flowi(&fl6));
101         dst = ip6_route_output(net, NULL, &fl6);
102         if (dst == NULL || dst->error) {
103                 dst_release(dst);
104                 return;
105         }
106         dst = xfrm_lookup(net, dst, flowi6_to_flowi(&fl6), NULL, 0);
107         if (IS_ERR(dst))
108                 return;
109
110         hh_len = (dst->dev->hard_header_len + 15)&~15;
111         nskb = alloc_skb(hh_len + 15 + dst->header_len + sizeof(struct ipv6hdr)
112                          + sizeof(struct tcphdr) + dst->trailer_len,
113                          GFP_ATOMIC);
114
115         if (!nskb) {
116                 if (net_ratelimit())
117                         pr_debug("cannot alloc skb\n");
118                 dst_release(dst);
119                 return;
120         }
121
122         skb_dst_set(nskb, dst);
123
124         skb_reserve(nskb, hh_len + dst->header_len);
125
126         skb_put(nskb, sizeof(struct ipv6hdr));
127         skb_reset_network_header(nskb);
128         ip6h = ipv6_hdr(nskb);
129         *(__be32 *)ip6h =  htonl(0x60000000 | (tclass << 20));
130         ip6h->hop_limit = ip6_dst_hoplimit(dst);
131         ip6h->nexthdr = IPPROTO_TCP;
132         ipv6_addr_copy(&ip6h->saddr, &oip6h->daddr);
133         ipv6_addr_copy(&ip6h->daddr, &oip6h->saddr);
134
135         tcph = (struct tcphdr *)skb_put(nskb, sizeof(struct tcphdr));
136         /* Truncate to length (no data) */
137         tcph->doff = sizeof(struct tcphdr)/4;
138         tcph->source = otcph.dest;
139         tcph->dest = otcph.source;
140
141         if (otcph.ack) {
142                 needs_ack = 0;
143                 tcph->seq = otcph.ack_seq;
144                 tcph->ack_seq = 0;
145         } else {
146                 needs_ack = 1;
147                 tcph->ack_seq = htonl(ntohl(otcph.seq) + otcph.syn + otcph.fin
148                                       + otcplen - (otcph.doff<<2));
149                 tcph->seq = 0;
150         }
151
152         /* Reset flags */
153         ((u_int8_t *)tcph)[13] = 0;
154         tcph->rst = 1;
155         tcph->ack = needs_ack;
156         tcph->window = 0;
157         tcph->urg_ptr = 0;
158         tcph->check = 0;
159
160         /* Adjust TCP checksum */
161         tcph->check = csum_ipv6_magic(&ipv6_hdr(nskb)->saddr,
162                                       &ipv6_hdr(nskb)->daddr,
163                                       sizeof(struct tcphdr), IPPROTO_TCP,
164                                       csum_partial(tcph,
165                                                    sizeof(struct tcphdr), 0));
166
167         nf_ct_attach(nskb, oldskb);
168
169         ip6_local_out(nskb);
170 }
171
172 static inline void
173 send_unreach(struct net *net, struct sk_buff *skb_in, unsigned char code,
174              unsigned int hooknum)
175 {
176         if (hooknum == NF_INET_LOCAL_OUT && skb_in->dev == NULL)
177                 skb_in->dev = net->loopback_dev;
178
179         icmpv6_send(skb_in, ICMPV6_DEST_UNREACH, code, 0);
180 }
181
182 static unsigned int
183 reject_tg6(struct sk_buff *skb, const struct xt_action_param *par)
184 {
185         const struct ip6t_reject_info *reject = par->targinfo;
186         struct net *net = dev_net((par->in != NULL) ? par->in : par->out);
187
188         pr_debug("%s: medium point\n", __func__);
189         switch (reject->with) {
190         case IP6T_ICMP6_NO_ROUTE:
191                 send_unreach(net, skb, ICMPV6_NOROUTE, par->hooknum);
192                 break;
193         case IP6T_ICMP6_ADM_PROHIBITED:
194                 send_unreach(net, skb, ICMPV6_ADM_PROHIBITED, par->hooknum);
195                 break;
196         case IP6T_ICMP6_NOT_NEIGHBOUR:
197                 send_unreach(net, skb, ICMPV6_NOT_NEIGHBOUR, par->hooknum);
198                 break;
199         case IP6T_ICMP6_ADDR_UNREACH:
200                 send_unreach(net, skb, ICMPV6_ADDR_UNREACH, par->hooknum);
201                 break;
202         case IP6T_ICMP6_PORT_UNREACH:
203                 send_unreach(net, skb, ICMPV6_PORT_UNREACH, par->hooknum);
204                 break;
205         case IP6T_ICMP6_ECHOREPLY:
206                 /* Do nothing */
207                 break;
208         case IP6T_TCP_RESET:
209                 send_reset(net, skb);
210                 break;
211         default:
212                 if (net_ratelimit())
213                         pr_info("case %u not handled yet\n", reject->with);
214                 break;
215         }
216
217         return NF_DROP;
218 }
219
220 static int reject_tg6_check(const struct xt_tgchk_param *par)
221 {
222         const struct ip6t_reject_info *rejinfo = par->targinfo;
223         const struct ip6t_entry *e = par->entryinfo;
224
225         if (rejinfo->with == IP6T_ICMP6_ECHOREPLY) {
226                 pr_info("ECHOREPLY is not supported.\n");
227                 return -EINVAL;
228         } else if (rejinfo->with == IP6T_TCP_RESET) {
229                 /* Must specify that it's a TCP packet */
230                 if (e->ipv6.proto != IPPROTO_TCP ||
231                     (e->ipv6.invflags & XT_INV_PROTO)) {
232                         pr_info("TCP_RESET illegal for non-tcp\n");
233                         return -EINVAL;
234                 }
235         }
236         return 0;
237 }
238
239 static struct xt_target reject_tg6_reg __read_mostly = {
240         .name           = "REJECT",
241         .family         = NFPROTO_IPV6,
242         .target         = reject_tg6,
243         .targetsize     = sizeof(struct ip6t_reject_info),
244         .table          = "filter",
245         .hooks          = (1 << NF_INET_LOCAL_IN) | (1 << NF_INET_FORWARD) |
246                           (1 << NF_INET_LOCAL_OUT),
247         .checkentry     = reject_tg6_check,
248         .me             = THIS_MODULE
249 };
250
251 static int __init reject_tg6_init(void)
252 {
253         return xt_register_target(&reject_tg6_reg);
254 }
255
256 static void __exit reject_tg6_exit(void)
257 {
258         xt_unregister_target(&reject_tg6_reg);
259 }
260
261 module_init(reject_tg6_init);
262 module_exit(reject_tg6_exit);