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]
7 /* (C) 1999-2001 Paul `Rusty' Russell
8 * (C) 2002-2004 Netfilter Core Team <coreteam@netfilter.org>
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.
15 #include <linux/config.h>
16 #include <linux/module.h>
17 #include <linux/skbuff.h>
19 #include <linux/udp.h>
20 #include <linux/icmp.h>
24 #include <net/route.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>
32 MODULE_LICENSE("GPL");
33 MODULE_AUTHOR("Netfilter Core Team <coreteam@netfilter.org>");
34 MODULE_DESCRIPTION("iptables REJECT target module");
39 #define DEBUGP(format, args...)
42 static inline struct rtable *route_reverse(struct sk_buff *skb,
43 struct tcphdr *tcph, int hook)
45 struct iphdr *iph = skb->nh.iph;
46 struct dst_entry *odst;
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)
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);
62 if (ip_route_output_key(&rt, &fl) != 0)
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)
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);
77 dst_release(&rt->u.dst);
78 rt = (struct rtable *)skb->dst;
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);
86 if (rt->u.dst.error) {
87 dst_release(&rt->u.dst);
91 fl.proto = IPPROTO_TCP;
92 fl.fl_ip_sport = tcph->dest;
93 fl.fl_ip_dport = tcph->source;
95 xfrm_lookup((struct dst_entry **)&rt, &fl, NULL, 0);
101 static void send_reset(struct sk_buff *oldskb, int hook)
103 struct sk_buff *nskb;
104 struct iphdr *iph = oldskb->nh.iph;
105 struct tcphdr _otcph, *oth, *tcph;
112 /* IP header checks: fragment. */
113 if (oldskb->nh.iph->frag_off & htons(IP_OFFSET))
116 oth = skb_header_pointer(oldskb, oldskb->nh.iph->ihl * 4,
117 sizeof(_otcph), &_otcph);
121 /* No RST for RST. */
126 if (nf_ip_checksum(oldskb, hook, iph->ihl * 4, IPPROTO_TCP))
129 if ((rt = route_reverse(oldskb, oth, hook)) == NULL)
132 hh_len = LL_RESERVED_SPACE(rt->u.dst.dev);
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),
140 dst_release(&rt->u.dst);
144 dst_release(nskb->dst);
145 nskb->dst = &rt->u.dst;
147 /* This packet will not be the same as the other: clear nf fields */
150 skb_init_secmark(nskb);
152 tcph = (struct tcphdr *)((u_int32_t*)nskb->nh.iph + nskb->nh.iph->ihl);
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;
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);
169 tcph->seq = oth->ack_seq;
173 tcph->ack_seq = htonl(ntohl(oth->seq) + oth->syn + oth->fin
174 + oldskb->len - oldskb->nh.iph->ihl*4
180 ((u_int8_t *)tcph)[13] = 0;
182 tcph->ack = needs_ack;
187 /* Adjust TCP checksum */
189 tcph->check = tcp_v4_check(tcph, sizeof(struct tcphdr),
192 csum_partial((char *)tcph,
193 sizeof(struct tcphdr), 0));
195 /* Adjust IP TTL, DF */
196 nskb->nh.iph->ttl = dst_metric(nskb->dst, RTAX_HOPLIMIT);
198 nskb->nh.iph->frag_off = htons(IP_DF);
199 nskb->nh.iph->id = 0;
201 /* Adjust IP checksum */
202 nskb->nh.iph->check = 0;
203 nskb->nh.iph->check = ip_fast_csum((unsigned char *)nskb->nh.iph,
206 /* "Never happens" */
207 if (nskb->len > dst_mtu(nskb->dst))
210 nf_ct_attach(nskb, oldskb);
212 NF_HOOK(PF_INET, NF_IP_LOCAL_OUT, nskb, NULL, nskb->dst->dev,
220 static inline void send_unreach(struct sk_buff *skb_in, int code)
222 icmp_send(skb_in, ICMP_DEST_UNREACH, code, 0);
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,
233 const struct ipt_reject_info *reject = targinfo;
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))
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);
247 case IPT_ICMP_HOST_UNREACHABLE:
248 send_unreach(*pskb, ICMP_HOST_UNREACH);
250 case IPT_ICMP_PROT_UNREACHABLE:
251 send_unreach(*pskb, ICMP_PROT_UNREACH);
253 case IPT_ICMP_PORT_UNREACHABLE:
254 send_unreach(*pskb, ICMP_PORT_UNREACH);
256 case IPT_ICMP_NET_PROHIBITED:
257 send_unreach(*pskb, ICMP_NET_ANO);
259 case IPT_ICMP_HOST_PROHIBITED:
260 send_unreach(*pskb, ICMP_HOST_ANO);
262 case IPT_ICMP_ADMIN_PROHIBITED:
263 send_unreach(*pskb, ICMP_PKT_FILTERED);
266 send_reset(*pskb, hooknum);
267 case IPT_ICMP_ECHOREPLY:
268 /* Doesn't happen. */
275 static int check(const char *tablename,
277 const struct xt_target *target,
279 unsigned int targinfosize,
280 unsigned int hook_mask)
282 const struct ipt_reject_info *rejinfo = targinfo;
283 const struct ipt_entry *e = e_void;
285 if (rejinfo->with == IPT_ICMP_ECHOREPLY) {
286 printk("REJECT: ECHOREPLY no longer supported.\n");
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");
299 static struct ipt_target ipt_reject_reg = {
302 .targetsize = sizeof(struct ipt_reject_info),
304 .hooks = (1 << NF_IP_LOCAL_IN) | (1 << NF_IP_FORWARD) |
305 (1 << NF_IP_LOCAL_OUT),
310 static int __init ipt_reject_init(void)
312 return ipt_register_target(&ipt_reject_reg);
315 static void __exit ipt_reject_fini(void)
317 ipt_unregister_target(&ipt_reject_reg);
320 module_init(ipt_reject_init);
321 module_exit(ipt_reject_fini);