[NETFILTER]: nf_conntrack: remove 'ignore_conntrack' argument from nf_conntrack_find_get
[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 #if 0
35 #define DEBUGP printk
36 #else
37 #define DEBUGP(format, args...)
38 #endif
39
40 /* Send RST reply */
41 static void send_reset(struct sk_buff *oldskb, int hook)
42 {
43         struct sk_buff *nskb;
44         struct iphdr *niph;
45         struct tcphdr _otcph, *oth, *tcph;
46         __be16 tmp_port;
47         __be32 tmp_addr;
48         int needs_ack;
49         unsigned int addr_type;
50
51         /* IP header checks: fragment. */
52         if (ip_hdr(oldskb)->frag_off & htons(IP_OFFSET))
53                 return;
54
55         oth = skb_header_pointer(oldskb, ip_hdrlen(oldskb),
56                                  sizeof(_otcph), &_otcph);
57         if (oth == NULL)
58                 return;
59
60         /* No RST for RST. */
61         if (oth->rst)
62                 return;
63
64         /* Check checksum */
65         if (nf_ip_checksum(oldskb, hook, ip_hdrlen(oldskb), IPPROTO_TCP))
66                 return;
67
68         /* We need a linear, writeable skb.  We also need to expand
69            headroom in case hh_len of incoming interface < hh_len of
70            outgoing interface */
71         nskb = skb_copy_expand(oldskb, LL_MAX_HEADER, skb_tailroom(oldskb),
72                                GFP_ATOMIC);
73         if (!nskb)
74                 return;
75
76         /* This packet will not be the same as the other: clear nf fields */
77         nf_reset(nskb);
78         nskb->mark = 0;
79         skb_init_secmark(nskb);
80
81         skb_shinfo(nskb)->gso_size = 0;
82         skb_shinfo(nskb)->gso_segs = 0;
83         skb_shinfo(nskb)->gso_type = 0;
84
85         tcph = (struct tcphdr *)(skb_network_header(nskb) + ip_hdrlen(nskb));
86
87         /* Swap source and dest */
88         niph = ip_hdr(nskb);
89         tmp_addr = niph->saddr;
90         niph->saddr = niph->daddr;
91         niph->daddr = tmp_addr;
92         tmp_port = tcph->source;
93         tcph->source = tcph->dest;
94         tcph->dest = tmp_port;
95
96         /* Truncate to length (no data) */
97         tcph->doff = sizeof(struct tcphdr)/4;
98         skb_trim(nskb, ip_hdrlen(nskb) + sizeof(struct tcphdr));
99         niph->tot_len = htons(nskb->len);
100
101         if (tcph->ack) {
102                 needs_ack = 0;
103                 tcph->seq = oth->ack_seq;
104                 tcph->ack_seq = 0;
105         } else {
106                 needs_ack = 1;
107                 tcph->ack_seq = htonl(ntohl(oth->seq) + oth->syn + oth->fin +
108                                       oldskb->len - ip_hdrlen(oldskb) -
109                                       (oth->doff << 2));
110                 tcph->seq = 0;
111         }
112
113         /* Reset flags */
114         ((u_int8_t *)tcph)[13] = 0;
115         tcph->rst = 1;
116         tcph->ack = needs_ack;
117
118         tcph->window = 0;
119         tcph->urg_ptr = 0;
120
121         /* Adjust TCP checksum */
122         tcph->check = 0;
123         tcph->check = tcp_v4_check(sizeof(struct tcphdr),
124                                    niph->saddr, niph->daddr,
125                                    csum_partial(tcph,
126                                                 sizeof(struct tcphdr), 0));
127
128         /* Set DF, id = 0 */
129         niph->frag_off = htons(IP_DF);
130         niph->id = 0;
131
132         addr_type = RTN_UNSPEC;
133         if (hook != NF_IP_FORWARD
134 #ifdef CONFIG_BRIDGE_NETFILTER
135             || (nskb->nf_bridge && nskb->nf_bridge->mask & BRNF_BRIDGED)
136 #endif
137            )
138                 addr_type = RTN_LOCAL;
139
140         if (ip_route_me_harder(&nskb, addr_type))
141                 goto free_nskb;
142
143         nskb->ip_summed = CHECKSUM_NONE;
144
145         /* Adjust IP TTL */
146         niph->ttl = dst_metric(nskb->dst, RTAX_HOPLIMIT);
147
148         /* Adjust IP checksum */
149         niph->check = 0;
150         niph->check = ip_fast_csum(skb_network_header(nskb), niph->ihl);
151
152         /* "Never happens" */
153         if (nskb->len > dst_mtu(nskb->dst))
154                 goto free_nskb;
155
156         nf_ct_attach(nskb, oldskb);
157
158         NF_HOOK(PF_INET, NF_IP_LOCAL_OUT, nskb, NULL, nskb->dst->dev,
159                 dst_output);
160         return;
161
162  free_nskb:
163         kfree_skb(nskb);
164 }
165
166 static inline void send_unreach(struct sk_buff *skb_in, int code)
167 {
168         icmp_send(skb_in, ICMP_DEST_UNREACH, code, 0);
169 }
170
171 static unsigned int reject(struct sk_buff **pskb,
172                            const struct net_device *in,
173                            const struct net_device *out,
174                            unsigned int hooknum,
175                            const struct xt_target *target,
176                            const void *targinfo)
177 {
178         const struct ipt_reject_info *reject = targinfo;
179
180         /* Our naive response construction doesn't deal with IP
181            options, and probably shouldn't try. */
182         if (ip_hdrlen(*pskb) != sizeof(struct iphdr))
183                 return NF_DROP;
184
185         /* WARNING: This code causes reentry within iptables.
186            This means that the iptables jump stack is now crap.  We
187            must return an absolute verdict. --RR */
188         switch (reject->with) {
189         case IPT_ICMP_NET_UNREACHABLE:
190                 send_unreach(*pskb, ICMP_NET_UNREACH);
191                 break;
192         case IPT_ICMP_HOST_UNREACHABLE:
193                 send_unreach(*pskb, ICMP_HOST_UNREACH);
194                 break;
195         case IPT_ICMP_PROT_UNREACHABLE:
196                 send_unreach(*pskb, ICMP_PROT_UNREACH);
197                 break;
198         case IPT_ICMP_PORT_UNREACHABLE:
199                 send_unreach(*pskb, ICMP_PORT_UNREACH);
200                 break;
201         case IPT_ICMP_NET_PROHIBITED:
202                 send_unreach(*pskb, ICMP_NET_ANO);
203                 break;
204         case IPT_ICMP_HOST_PROHIBITED:
205                 send_unreach(*pskb, ICMP_HOST_ANO);
206                 break;
207         case IPT_ICMP_ADMIN_PROHIBITED:
208                 send_unreach(*pskb, ICMP_PKT_FILTERED);
209                 break;
210         case IPT_TCP_RESET:
211                 send_reset(*pskb, hooknum);
212         case IPT_ICMP_ECHOREPLY:
213                 /* Doesn't happen. */
214                 break;
215         }
216
217         return NF_DROP;
218 }
219
220 static bool check(const char *tablename,
221                   const void *e_void,
222                   const struct xt_target *target,
223                   void *targinfo,
224                   unsigned int hook_mask)
225 {
226         const struct ipt_reject_info *rejinfo = targinfo;
227         const struct ipt_entry *e = e_void;
228
229         if (rejinfo->with == IPT_ICMP_ECHOREPLY) {
230                 printk("REJECT: ECHOREPLY no longer supported.\n");
231                 return false;
232         } else if (rejinfo->with == IPT_TCP_RESET) {
233                 /* Must specify that it's a TCP packet */
234                 if (e->ip.proto != IPPROTO_TCP
235                     || (e->ip.invflags & XT_INV_PROTO)) {
236                         DEBUGP("REJECT: TCP_RESET invalid for non-tcp\n");
237                         return false;
238                 }
239         }
240         return true;
241 }
242
243 static struct xt_target ipt_reject_reg __read_mostly = {
244         .name           = "REJECT",
245         .family         = AF_INET,
246         .target         = reject,
247         .targetsize     = sizeof(struct ipt_reject_info),
248         .table          = "filter",
249         .hooks          = (1 << NF_IP_LOCAL_IN) | (1 << NF_IP_FORWARD) |
250                           (1 << NF_IP_LOCAL_OUT),
251         .checkentry     = check,
252         .me             = THIS_MODULE,
253 };
254
255 static int __init ipt_reject_init(void)
256 {
257         return xt_register_target(&ipt_reject_reg);
258 }
259
260 static void __exit ipt_reject_fini(void)
261 {
262         xt_unregister_target(&ipt_reject_reg);
263 }
264
265 module_init(ipt_reject_init);
266 module_exit(ipt_reject_fini);