Merge git://git.infradead.org/hdrcleanup-2.6
[linux-2.6] / net / ipv4 / netfilter / ipt_REJECT.c
1 /*
2  * This is a module which is used for rejecting packets.
3  * Added support for customized reject packets (Jozsef Kadlecsik).
4  * Added support for ICMP type-3-code-13 (Maciej Soltysiak). [RFC 1812]
5  */
6
7 /* (C) 1999-2001 Paul `Rusty' Russell
8  * (C) 2002-2004 Netfilter Core Team <coreteam@netfilter.org>
9  *
10  * This program is free software; you can redistribute it and/or modify
11  * it under the terms of the GNU General Public License version 2 as
12  * published by the Free Software Foundation.
13  */
14
15 #include <linux/config.h>
16 #include <linux/module.h>
17 #include <linux/skbuff.h>
18 #include <linux/ip.h>
19 #include <linux/udp.h>
20 #include <linux/icmp.h>
21 #include <net/icmp.h>
22 #include <net/ip.h>
23 #include <net/tcp.h>
24 #include <net/route.h>
25 #include <net/dst.h>
26 #include <linux/netfilter_ipv4/ip_tables.h>
27 #include <linux/netfilter_ipv4/ipt_REJECT.h>
28 #ifdef CONFIG_BRIDGE_NETFILTER
29 #include <linux/netfilter_bridge.h>
30 #endif
31
32 MODULE_LICENSE("GPL");
33 MODULE_AUTHOR("Netfilter Core Team <coreteam@netfilter.org>");
34 MODULE_DESCRIPTION("iptables REJECT target module");
35
36 #if 0
37 #define DEBUGP printk
38 #else
39 #define DEBUGP(format, args...)
40 #endif
41
42 static inline struct rtable *route_reverse(struct sk_buff *skb, 
43                                            struct tcphdr *tcph, int hook)
44 {
45         struct iphdr *iph = skb->nh.iph;
46         struct dst_entry *odst;
47         struct flowi fl = {};
48         struct rtable *rt;
49
50         /* We don't require ip forwarding to be enabled to be able to
51          * send a RST reply for bridged traffic. */
52         if (hook != NF_IP_FORWARD
53 #ifdef CONFIG_BRIDGE_NETFILTER
54             || (skb->nf_bridge && skb->nf_bridge->mask & BRNF_BRIDGED)
55 #endif
56            ) {
57                 fl.nl_u.ip4_u.daddr = iph->saddr;
58                 if (hook == NF_IP_LOCAL_IN)
59                         fl.nl_u.ip4_u.saddr = iph->daddr;
60                 fl.nl_u.ip4_u.tos = RT_TOS(iph->tos);
61
62                 if (ip_route_output_key(&rt, &fl) != 0)
63                         return NULL;
64         } else {
65                 /* non-local src, find valid iif to satisfy
66                  * rp-filter when calling ip_route_input. */
67                 fl.nl_u.ip4_u.daddr = iph->daddr;
68                 if (ip_route_output_key(&rt, &fl) != 0)
69                         return NULL;
70
71                 odst = skb->dst;
72                 if (ip_route_input(skb, iph->saddr, iph->daddr,
73                                    RT_TOS(iph->tos), rt->u.dst.dev) != 0) {
74                         dst_release(&rt->u.dst);
75                         return NULL;
76                 }
77                 dst_release(&rt->u.dst);
78                 rt = (struct rtable *)skb->dst;
79                 skb->dst = odst;
80
81                 fl.nl_u.ip4_u.daddr = iph->saddr;
82                 fl.nl_u.ip4_u.saddr = iph->daddr;
83                 fl.nl_u.ip4_u.tos = RT_TOS(iph->tos);
84         }
85
86         if (rt->u.dst.error) {
87                 dst_release(&rt->u.dst);
88                 return NULL;
89         }
90
91         fl.proto = IPPROTO_TCP;
92         fl.fl_ip_sport = tcph->dest;
93         fl.fl_ip_dport = tcph->source;
94
95         xfrm_lookup((struct dst_entry **)&rt, &fl, NULL, 0);
96
97         return rt;
98 }
99
100 /* Send RST reply */
101 static void send_reset(struct sk_buff *oldskb, int hook)
102 {
103         struct sk_buff *nskb;
104         struct iphdr *iph = oldskb->nh.iph;
105         struct tcphdr _otcph, *oth, *tcph;
106         struct rtable *rt;
107         u_int16_t tmp_port;
108         u_int32_t tmp_addr;
109         int needs_ack;
110         int hh_len;
111
112         /* IP header checks: fragment. */
113         if (oldskb->nh.iph->frag_off & htons(IP_OFFSET))
114                 return;
115
116         oth = skb_header_pointer(oldskb, oldskb->nh.iph->ihl * 4,
117                                  sizeof(_otcph), &_otcph);
118         if (oth == NULL)
119                 return;
120
121         /* No RST for RST. */
122         if (oth->rst)
123                 return;
124
125         /* Check checksum */
126         if (nf_ip_checksum(oldskb, hook, iph->ihl * 4, IPPROTO_TCP))
127                 return;
128
129         if ((rt = route_reverse(oldskb, oth, hook)) == NULL)
130                 return;
131
132         hh_len = LL_RESERVED_SPACE(rt->u.dst.dev);
133
134         /* We need a linear, writeable skb.  We also need to expand
135            headroom in case hh_len of incoming interface < hh_len of
136            outgoing interface */
137         nskb = skb_copy_expand(oldskb, hh_len, skb_tailroom(oldskb),
138                                GFP_ATOMIC);
139         if (!nskb) {
140                 dst_release(&rt->u.dst);
141                 return;
142         }
143
144         dst_release(nskb->dst);
145         nskb->dst = &rt->u.dst;
146
147         /* This packet will not be the same as the other: clear nf fields */
148         nf_reset(nskb);
149         nskb->nfmark = 0;
150         skb_init_secmark(nskb);
151
152         tcph = (struct tcphdr *)((u_int32_t*)nskb->nh.iph + nskb->nh.iph->ihl);
153
154         /* Swap source and dest */
155         tmp_addr = nskb->nh.iph->saddr;
156         nskb->nh.iph->saddr = nskb->nh.iph->daddr;
157         nskb->nh.iph->daddr = tmp_addr;
158         tmp_port = tcph->source;
159         tcph->source = tcph->dest;
160         tcph->dest = tmp_port;
161
162         /* Truncate to length (no data) */
163         tcph->doff = sizeof(struct tcphdr)/4;
164         skb_trim(nskb, nskb->nh.iph->ihl*4 + sizeof(struct tcphdr));
165         nskb->nh.iph->tot_len = htons(nskb->len);
166
167         if (tcph->ack) {
168                 needs_ack = 0;
169                 tcph->seq = oth->ack_seq;
170                 tcph->ack_seq = 0;
171         } else {
172                 needs_ack = 1;
173                 tcph->ack_seq = htonl(ntohl(oth->seq) + oth->syn + oth->fin
174                                       + oldskb->len - oldskb->nh.iph->ihl*4
175                                       - (oth->doff<<2));
176                 tcph->seq = 0;
177         }
178
179         /* Reset flags */
180         ((u_int8_t *)tcph)[13] = 0;
181         tcph->rst = 1;
182         tcph->ack = needs_ack;
183
184         tcph->window = 0;
185         tcph->urg_ptr = 0;
186
187         /* Adjust TCP checksum */
188         tcph->check = 0;
189         tcph->check = tcp_v4_check(tcph, sizeof(struct tcphdr),
190                                    nskb->nh.iph->saddr,
191                                    nskb->nh.iph->daddr,
192                                    csum_partial((char *)tcph,
193                                                 sizeof(struct tcphdr), 0));
194
195         /* Adjust IP TTL, DF */
196         nskb->nh.iph->ttl = dst_metric(nskb->dst, RTAX_HOPLIMIT);
197         /* Set DF, id = 0 */
198         nskb->nh.iph->frag_off = htons(IP_DF);
199         nskb->nh.iph->id = 0;
200
201         /* Adjust IP checksum */
202         nskb->nh.iph->check = 0;
203         nskb->nh.iph->check = ip_fast_csum((unsigned char *)nskb->nh.iph, 
204                                            nskb->nh.iph->ihl);
205
206         /* "Never happens" */
207         if (nskb->len > dst_mtu(nskb->dst))
208                 goto free_nskb;
209
210         nf_ct_attach(nskb, oldskb);
211
212         NF_HOOK(PF_INET, NF_IP_LOCAL_OUT, nskb, NULL, nskb->dst->dev,
213                 dst_output);
214         return;
215
216  free_nskb:
217         kfree_skb(nskb);
218 }
219
220 static inline void send_unreach(struct sk_buff *skb_in, int code)
221 {
222         icmp_send(skb_in, ICMP_DEST_UNREACH, code, 0);
223 }       
224
225 static unsigned int reject(struct sk_buff **pskb,
226                            const struct net_device *in,
227                            const struct net_device *out,
228                            unsigned int hooknum,
229                            const struct xt_target *target,
230                            const void *targinfo,
231                            void *userinfo)
232 {
233         const struct ipt_reject_info *reject = targinfo;
234
235         /* Our naive response construction doesn't deal with IP
236            options, and probably shouldn't try. */
237         if ((*pskb)->nh.iph->ihl<<2 != sizeof(struct iphdr))
238                 return NF_DROP;
239
240         /* WARNING: This code causes reentry within iptables.
241            This means that the iptables jump stack is now crap.  We
242            must return an absolute verdict. --RR */
243         switch (reject->with) {
244         case IPT_ICMP_NET_UNREACHABLE:
245                 send_unreach(*pskb, ICMP_NET_UNREACH);
246                 break;
247         case IPT_ICMP_HOST_UNREACHABLE:
248                 send_unreach(*pskb, ICMP_HOST_UNREACH);
249                 break;
250         case IPT_ICMP_PROT_UNREACHABLE:
251                 send_unreach(*pskb, ICMP_PROT_UNREACH);
252                 break;
253         case IPT_ICMP_PORT_UNREACHABLE:
254                 send_unreach(*pskb, ICMP_PORT_UNREACH);
255                 break;
256         case IPT_ICMP_NET_PROHIBITED:
257                 send_unreach(*pskb, ICMP_NET_ANO);
258                 break;
259         case IPT_ICMP_HOST_PROHIBITED:
260                 send_unreach(*pskb, ICMP_HOST_ANO);
261                 break;
262         case IPT_ICMP_ADMIN_PROHIBITED:
263                 send_unreach(*pskb, ICMP_PKT_FILTERED);
264                 break;
265         case IPT_TCP_RESET:
266                 send_reset(*pskb, hooknum);
267         case IPT_ICMP_ECHOREPLY:
268                 /* Doesn't happen. */
269                 break;
270         }
271
272         return NF_DROP;
273 }
274
275 static int check(const char *tablename,
276                  const void *e_void,
277                  const struct xt_target *target,
278                  void *targinfo,
279                  unsigned int targinfosize,
280                  unsigned int hook_mask)
281 {
282         const struct ipt_reject_info *rejinfo = targinfo;
283         const struct ipt_entry *e = e_void;
284
285         if (rejinfo->with == IPT_ICMP_ECHOREPLY) {
286                 printk("REJECT: ECHOREPLY no longer supported.\n");
287                 return 0;
288         } else if (rejinfo->with == IPT_TCP_RESET) {
289                 /* Must specify that it's a TCP packet */
290                 if (e->ip.proto != IPPROTO_TCP
291                     || (e->ip.invflags & IPT_INV_PROTO)) {
292                         DEBUGP("REJECT: TCP_RESET invalid for non-tcp\n");
293                         return 0;
294                 }
295         }
296         return 1;
297 }
298
299 static struct ipt_target ipt_reject_reg = {
300         .name           = "REJECT",
301         .target         = reject,
302         .targetsize     = sizeof(struct ipt_reject_info),
303         .table          = "filter",
304         .hooks          = (1 << NF_IP_LOCAL_IN) | (1 << NF_IP_FORWARD) |
305                           (1 << NF_IP_LOCAL_OUT),
306         .checkentry     = check,
307         .me             = THIS_MODULE,
308 };
309
310 static int __init ipt_reject_init(void)
311 {
312         return ipt_register_target(&ipt_reject_reg);
313 }
314
315 static void __exit ipt_reject_fini(void)
316 {
317         ipt_unregister_target(&ipt_reject_reg);
318 }
319
320 module_init(ipt_reject_init);
321 module_exit(ipt_reject_fini);