Commit | Line | Data |
---|---|---|
1da177e4 LT |
1 | /* |
2 | * This is a module which is used for rejecting packets. | |
1da177e4 LT |
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 | ||
1da177e4 LT |
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> | |
6709dbbb | 23 | #include <linux/netfilter/x_tables.h> |
1da177e4 LT |
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 | ||
1da177e4 LT |
40 | /* Send RST reply */ |
41 | static void send_reset(struct sk_buff *oldskb, int hook) | |
42 | { | |
43 | struct sk_buff *nskb; | |
eddc9ec5 | 44 | struct iphdr *niph; |
1da177e4 | 45 | struct tcphdr _otcph, *oth, *tcph; |
6a19d614 AV |
46 | __be16 tmp_port; |
47 | __be32 tmp_addr; | |
1da177e4 | 48 | int needs_ack; |
9d02002d | 49 | unsigned int addr_type; |
1da177e4 LT |
50 | |
51 | /* IP header checks: fragment. */ | |
eddc9ec5 | 52 | if (ip_hdr(oldskb)->frag_off & htons(IP_OFFSET)) |
1da177e4 LT |
53 | return; |
54 | ||
c9bdd4b5 | 55 | oth = skb_header_pointer(oldskb, ip_hdrlen(oldskb), |
1da177e4 LT |
56 | sizeof(_otcph), &_otcph); |
57 | if (oth == NULL) | |
e905a9ed | 58 | return; |
1da177e4 LT |
59 | |
60 | /* No RST for RST. */ | |
61 | if (oth->rst) | |
62 | return; | |
63 | ||
6150bacf | 64 | /* Check checksum */ |
c9bdd4b5 | 65 | if (nf_ip_checksum(oldskb, hook, ip_hdrlen(oldskb), IPPROTO_TCP)) |
6150bacf PM |
66 | return; |
67 | ||
1da177e4 LT |
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 */ | |
9d02002d | 71 | nskb = skb_copy_expand(oldskb, LL_MAX_HEADER, skb_tailroom(oldskb), |
1da177e4 | 72 | GFP_ATOMIC); |
9d02002d | 73 | if (!nskb) |
1da177e4 | 74 | return; |
1da177e4 LT |
75 | |
76 | /* This packet will not be the same as the other: clear nf fields */ | |
77 | nf_reset(nskb); | |
82e91ffe | 78 | nskb->mark = 0; |
984bc16c | 79 | skb_init_secmark(nskb); |
1da177e4 | 80 | |
bbf4a6bc HX |
81 | skb_shinfo(nskb)->gso_size = 0; |
82 | skb_shinfo(nskb)->gso_segs = 0; | |
83 | skb_shinfo(nskb)->gso_type = 0; | |
84 | ||
c9bdd4b5 | 85 | tcph = (struct tcphdr *)(skb_network_header(nskb) + ip_hdrlen(nskb)); |
1da177e4 LT |
86 | |
87 | /* Swap source and dest */ | |
eddc9ec5 ACM |
88 | niph = ip_hdr(nskb); |
89 | tmp_addr = niph->saddr; | |
90 | niph->saddr = niph->daddr; | |
91 | niph->daddr = tmp_addr; | |
1da177e4 LT |
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; | |
c9bdd4b5 | 98 | skb_trim(nskb, ip_hdrlen(nskb) + sizeof(struct tcphdr)); |
eddc9ec5 | 99 | niph->tot_len = htons(nskb->len); |
1da177e4 LT |
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; | |
c9bdd4b5 ACM |
107 | tcph->ack_seq = htonl(ntohl(oth->seq) + oth->syn + oth->fin + |
108 | oldskb->len - ip_hdrlen(oldskb) - | |
109 | (oth->doff << 2)); | |
1da177e4 LT |
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 | ||
af443b6d PM |
121 | /* Adjust TCP checksum */ |
122 | tcph->check = 0; | |
ba7808ea | 123 | tcph->check = tcp_v4_check(sizeof(struct tcphdr), |
eddc9ec5 | 124 | niph->saddr, niph->daddr, |
a47362a2 | 125 | csum_partial(tcph, |
af443b6d PM |
126 | sizeof(struct tcphdr), 0)); |
127 | ||
9d02002d | 128 | /* Set DF, id = 0 */ |
eddc9ec5 ACM |
129 | niph->frag_off = htons(IP_DF); |
130 | niph->id = 0; | |
9d02002d PM |
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 | ||
4cf411de | 143 | nskb->ip_summed = CHECKSUM_NONE; |
af443b6d | 144 | |
9d02002d | 145 | /* Adjust IP TTL */ |
eddc9ec5 | 146 | niph->ttl = dst_metric(nskb->dst, RTAX_HOPLIMIT); |
1da177e4 LT |
147 | |
148 | /* Adjust IP checksum */ | |
eddc9ec5 ACM |
149 | niph->check = 0; |
150 | niph->check = ip_fast_csum(skb_network_header(nskb), niph->ihl); | |
1da177e4 LT |
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); | |
e905a9ed | 169 | } |
1da177e4 LT |
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, | |
c4986734 | 175 | const struct xt_target *target, |
fe1cb108 | 176 | const void *targinfo) |
1da177e4 LT |
177 | { |
178 | const struct ipt_reject_info *reject = targinfo; | |
179 | ||
180 | /* Our naive response construction doesn't deal with IP | |
e905a9ed | 181 | options, and probably shouldn't try. */ |
c9bdd4b5 | 182 | if (ip_hdrlen(*pskb) != sizeof(struct iphdr)) |
1da177e4 LT |
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 */ | |
e905a9ed YH |
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; | |
1da177e4 | 204 | case IPT_ICMP_HOST_PROHIBITED: |
e905a9ed YH |
205 | send_unreach(*pskb, ICMP_HOST_ANO); |
206 | break; | |
207 | case IPT_ICMP_ADMIN_PROHIBITED: | |
1da177e4 LT |
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 | ||
e1931b78 JE |
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) | |
1da177e4 | 225 | { |
e905a9ed | 226 | const struct ipt_reject_info *rejinfo = targinfo; |
2e4e6a17 | 227 | const struct ipt_entry *e = e_void; |
1da177e4 | 228 | |
1da177e4 LT |
229 | if (rejinfo->with == IPT_ICMP_ECHOREPLY) { |
230 | printk("REJECT: ECHOREPLY no longer supported.\n"); | |
e1931b78 | 231 | return false; |
1da177e4 LT |
232 | } else if (rejinfo->with == IPT_TCP_RESET) { |
233 | /* Must specify that it's a TCP packet */ | |
234 | if (e->ip.proto != IPPROTO_TCP | |
6709dbbb | 235 | || (e->ip.invflags & XT_INV_PROTO)) { |
1da177e4 | 236 | DEBUGP("REJECT: TCP_RESET invalid for non-tcp\n"); |
e1931b78 | 237 | return false; |
1da177e4 LT |
238 | } |
239 | } | |
e1931b78 | 240 | return true; |
1da177e4 LT |
241 | } |
242 | ||
6709dbbb | 243 | static struct xt_target ipt_reject_reg = { |
1da177e4 | 244 | .name = "REJECT", |
6709dbbb | 245 | .family = AF_INET, |
1da177e4 | 246 | .target = reject, |
1d5cd909 PM |
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), | |
1da177e4 LT |
251 | .checkentry = check, |
252 | .me = THIS_MODULE, | |
253 | }; | |
254 | ||
65b4b4e8 | 255 | static int __init ipt_reject_init(void) |
1da177e4 | 256 | { |
6709dbbb | 257 | return xt_register_target(&ipt_reject_reg); |
1da177e4 LT |
258 | } |
259 | ||
65b4b4e8 | 260 | static void __exit ipt_reject_fini(void) |
1da177e4 | 261 | { |
6709dbbb | 262 | xt_unregister_target(&ipt_reject_reg); |
1da177e4 LT |
263 | } |
264 | ||
65b4b4e8 AM |
265 | module_init(ipt_reject_init); |
266 | module_exit(ipt_reject_fini); |