Merge branch 'i2c-for-linus' of git://jdelvare.pck.nerim.net/jdelvare-2.6
[linux-2.6] / net / ipv4 / netfilter / ipt_REJECT.c
1 /*
2  * This is a module which is used for rejecting packets.
3  */
4
5 /* (C) 1999-2001 Paul `Rusty' Russell
6  * (C) 2002-2004 Netfilter Core Team <coreteam@netfilter.org>
7  *
8  * This program is free software; you can redistribute it and/or modify
9  * it under the terms of the GNU General Public License version 2 as
10  * published by the Free Software Foundation.
11  */
12
13 #include <linux/module.h>
14 #include <linux/skbuff.h>
15 #include <linux/ip.h>
16 #include <linux/udp.h>
17 #include <linux/icmp.h>
18 #include <net/icmp.h>
19 #include <net/ip.h>
20 #include <net/tcp.h>
21 #include <net/route.h>
22 #include <net/dst.h>
23 #include <linux/netfilter/x_tables.h>
24 #include <linux/netfilter_ipv4/ip_tables.h>
25 #include <linux/netfilter_ipv4/ipt_REJECT.h>
26 #ifdef CONFIG_BRIDGE_NETFILTER
27 #include <linux/netfilter_bridge.h>
28 #endif
29
30 MODULE_LICENSE("GPL");
31 MODULE_AUTHOR("Netfilter Core Team <coreteam@netfilter.org>");
32 MODULE_DESCRIPTION("iptables REJECT target module");
33
34 /* Send RST reply */
35 static void send_reset(struct sk_buff *oldskb, int hook)
36 {
37         struct sk_buff *nskb;
38         struct iphdr *niph;
39         struct tcphdr _otcph, *oth, *tcph;
40         __be16 tmp_port;
41         __be32 tmp_addr;
42         int needs_ack;
43         unsigned int addr_type;
44
45         /* IP header checks: fragment. */
46         if (ip_hdr(oldskb)->frag_off & htons(IP_OFFSET))
47                 return;
48
49         oth = skb_header_pointer(oldskb, ip_hdrlen(oldskb),
50                                  sizeof(_otcph), &_otcph);
51         if (oth == NULL)
52                 return;
53
54         /* No RST for RST. */
55         if (oth->rst)
56                 return;
57
58         /* Check checksum */
59         if (nf_ip_checksum(oldskb, hook, ip_hdrlen(oldskb), IPPROTO_TCP))
60                 return;
61
62         /* We need a linear, writeable skb.  We also need to expand
63            headroom in case hh_len of incoming interface < hh_len of
64            outgoing interface */
65         nskb = skb_copy_expand(oldskb, LL_MAX_HEADER, skb_tailroom(oldskb),
66                                GFP_ATOMIC);
67         if (!nskb)
68                 return;
69
70         /* This packet will not be the same as the other: clear nf fields */
71         nf_reset(nskb);
72         nskb->mark = 0;
73         skb_init_secmark(nskb);
74
75         skb_shinfo(nskb)->gso_size = 0;
76         skb_shinfo(nskb)->gso_segs = 0;
77         skb_shinfo(nskb)->gso_type = 0;
78
79         tcph = (struct tcphdr *)(skb_network_header(nskb) + ip_hdrlen(nskb));
80
81         /* Swap source and dest */
82         niph = ip_hdr(nskb);
83         tmp_addr = niph->saddr;
84         niph->saddr = niph->daddr;
85         niph->daddr = tmp_addr;
86         tmp_port = tcph->source;
87         tcph->source = tcph->dest;
88         tcph->dest = tmp_port;
89
90         /* Truncate to length (no data) */
91         tcph->doff = sizeof(struct tcphdr)/4;
92         skb_trim(nskb, ip_hdrlen(nskb) + sizeof(struct tcphdr));
93         niph->tot_len = htons(nskb->len);
94
95         if (tcph->ack) {
96                 needs_ack = 0;
97                 tcph->seq = oth->ack_seq;
98                 tcph->ack_seq = 0;
99         } else {
100                 needs_ack = 1;
101                 tcph->ack_seq = htonl(ntohl(oth->seq) + oth->syn + oth->fin +
102                                       oldskb->len - ip_hdrlen(oldskb) -
103                                       (oth->doff << 2));
104                 tcph->seq = 0;
105         }
106
107         /* Reset flags */
108         ((u_int8_t *)tcph)[13] = 0;
109         tcph->rst = 1;
110         tcph->ack = needs_ack;
111
112         tcph->window = 0;
113         tcph->urg_ptr = 0;
114
115         /* Adjust TCP checksum */
116         tcph->check = 0;
117         tcph->check = tcp_v4_check(sizeof(struct tcphdr),
118                                    niph->saddr, niph->daddr,
119                                    csum_partial(tcph,
120                                                 sizeof(struct tcphdr), 0));
121
122         /* Set DF, id = 0 */
123         niph->frag_off = htons(IP_DF);
124         niph->id = 0;
125
126         addr_type = RTN_UNSPEC;
127         if (hook != NF_IP_FORWARD
128 #ifdef CONFIG_BRIDGE_NETFILTER
129             || (nskb->nf_bridge && nskb->nf_bridge->mask & BRNF_BRIDGED)
130 #endif
131            )
132                 addr_type = RTN_LOCAL;
133
134         if (ip_route_me_harder(&nskb, addr_type))
135                 goto free_nskb;
136
137         nskb->ip_summed = CHECKSUM_NONE;
138
139         /* Adjust IP TTL */
140         niph->ttl = dst_metric(nskb->dst, RTAX_HOPLIMIT);
141
142         /* Adjust IP checksum */
143         niph->check = 0;
144         niph->check = ip_fast_csum(skb_network_header(nskb), niph->ihl);
145
146         /* "Never happens" */
147         if (nskb->len > dst_mtu(nskb->dst))
148                 goto free_nskb;
149
150         nf_ct_attach(nskb, oldskb);
151
152         NF_HOOK(PF_INET, NF_IP_LOCAL_OUT, nskb, NULL, nskb->dst->dev,
153                 dst_output);
154         return;
155
156  free_nskb:
157         kfree_skb(nskb);
158 }
159
160 static inline void send_unreach(struct sk_buff *skb_in, int code)
161 {
162         icmp_send(skb_in, ICMP_DEST_UNREACH, code, 0);
163 }
164
165 static unsigned int reject(struct sk_buff **pskb,
166                            const struct net_device *in,
167                            const struct net_device *out,
168                            unsigned int hooknum,
169                            const struct xt_target *target,
170                            const void *targinfo)
171 {
172         const struct ipt_reject_info *reject = targinfo;
173
174         /* Our naive response construction doesn't deal with IP
175            options, and probably shouldn't try. */
176         if (ip_hdrlen(*pskb) != sizeof(struct iphdr))
177                 return NF_DROP;
178
179         /* WARNING: This code causes reentry within iptables.
180            This means that the iptables jump stack is now crap.  We
181            must return an absolute verdict. --RR */
182         switch (reject->with) {
183         case IPT_ICMP_NET_UNREACHABLE:
184                 send_unreach(*pskb, ICMP_NET_UNREACH);
185                 break;
186         case IPT_ICMP_HOST_UNREACHABLE:
187                 send_unreach(*pskb, ICMP_HOST_UNREACH);
188                 break;
189         case IPT_ICMP_PROT_UNREACHABLE:
190                 send_unreach(*pskb, ICMP_PROT_UNREACH);
191                 break;
192         case IPT_ICMP_PORT_UNREACHABLE:
193                 send_unreach(*pskb, ICMP_PORT_UNREACH);
194                 break;
195         case IPT_ICMP_NET_PROHIBITED:
196                 send_unreach(*pskb, ICMP_NET_ANO);
197                 break;
198         case IPT_ICMP_HOST_PROHIBITED:
199                 send_unreach(*pskb, ICMP_HOST_ANO);
200                 break;
201         case IPT_ICMP_ADMIN_PROHIBITED:
202                 send_unreach(*pskb, ICMP_PKT_FILTERED);
203                 break;
204         case IPT_TCP_RESET:
205                 send_reset(*pskb, hooknum);
206         case IPT_ICMP_ECHOREPLY:
207                 /* Doesn't happen. */
208                 break;
209         }
210
211         return NF_DROP;
212 }
213
214 static bool check(const char *tablename,
215                   const void *e_void,
216                   const struct xt_target *target,
217                   void *targinfo,
218                   unsigned int hook_mask)
219 {
220         const struct ipt_reject_info *rejinfo = targinfo;
221         const struct ipt_entry *e = e_void;
222
223         if (rejinfo->with == IPT_ICMP_ECHOREPLY) {
224                 printk("ipt_REJECT: ECHOREPLY no longer supported.\n");
225                 return false;
226         } else if (rejinfo->with == IPT_TCP_RESET) {
227                 /* Must specify that it's a TCP packet */
228                 if (e->ip.proto != IPPROTO_TCP
229                     || (e->ip.invflags & XT_INV_PROTO)) {
230                         printk("ipt_REJECT: TCP_RESET invalid for non-tcp\n");
231                         return false;
232                 }
233         }
234         return true;
235 }
236
237 static struct xt_target ipt_reject_reg __read_mostly = {
238         .name           = "REJECT",
239         .family         = AF_INET,
240         .target         = reject,
241         .targetsize     = sizeof(struct ipt_reject_info),
242         .table          = "filter",
243         .hooks          = (1 << NF_IP_LOCAL_IN) | (1 << NF_IP_FORWARD) |
244                           (1 << NF_IP_LOCAL_OUT),
245         .checkentry     = check,
246         .me             = THIS_MODULE,
247 };
248
249 static int __init ipt_reject_init(void)
250 {
251         return xt_register_target(&ipt_reject_reg);
252 }
253
254 static void __exit ipt_reject_fini(void)
255 {
256         xt_unregister_target(&ipt_reject_reg);
257 }
258
259 module_init(ipt_reject_init);
260 module_exit(ipt_reject_fini);