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/module.h>
16 #include <linux/skbuff.h>
18 #include <linux/udp.h>
19 #include <linux/icmp.h>
23 #include <net/route.h>
25 #include <linux/netfilter_ipv4/ip_tables.h>
26 #include <linux/netfilter_ipv4/ipt_REJECT.h>
27 #ifdef CONFIG_BRIDGE_NETFILTER
28 #include <linux/netfilter_bridge.h>
31 MODULE_LICENSE("GPL");
32 MODULE_AUTHOR("Netfilter Core Team <coreteam@netfilter.org>");
33 MODULE_DESCRIPTION("iptables REJECT target module");
38 #define DEBUGP(format, args...)
41 static inline struct rtable *route_reverse(struct sk_buff *skb,
42 struct tcphdr *tcph, int hook)
44 struct iphdr *iph = skb->nh.iph;
45 struct dst_entry *odst;
49 /* We don't require ip forwarding to be enabled to be able to
50 * send a RST reply for bridged traffic. */
51 if (hook != NF_IP_FORWARD
52 #ifdef CONFIG_BRIDGE_NETFILTER
53 || (skb->nf_bridge && skb->nf_bridge->mask & BRNF_BRIDGED)
56 fl.nl_u.ip4_u.daddr = iph->saddr;
57 if (hook == NF_IP_LOCAL_IN)
58 fl.nl_u.ip4_u.saddr = iph->daddr;
59 fl.nl_u.ip4_u.tos = RT_TOS(iph->tos);
61 if (ip_route_output_key(&rt, &fl) != 0)
64 /* non-local src, find valid iif to satisfy
65 * rp-filter when calling ip_route_input. */
66 fl.nl_u.ip4_u.daddr = iph->daddr;
67 if (ip_route_output_key(&rt, &fl) != 0)
71 if (ip_route_input(skb, iph->saddr, iph->daddr,
72 RT_TOS(iph->tos), rt->u.dst.dev) != 0) {
73 dst_release(&rt->u.dst);
76 dst_release(&rt->u.dst);
77 rt = (struct rtable *)skb->dst;
80 fl.nl_u.ip4_u.daddr = iph->saddr;
81 fl.nl_u.ip4_u.saddr = iph->daddr;
82 fl.nl_u.ip4_u.tos = RT_TOS(iph->tos);
85 if (rt->u.dst.error) {
86 dst_release(&rt->u.dst);
90 fl.proto = IPPROTO_TCP;
91 fl.fl_ip_sport = tcph->dest;
92 fl.fl_ip_dport = tcph->source;
94 xfrm_lookup((struct dst_entry **)&rt, &fl, NULL, 0);
100 static void send_reset(struct sk_buff *oldskb, int hook)
102 struct sk_buff *nskb;
103 struct iphdr *iph = oldskb->nh.iph;
104 struct tcphdr _otcph, *oth, *tcph;
111 /* IP header checks: fragment. */
112 if (oldskb->nh.iph->frag_off & htons(IP_OFFSET))
115 oth = skb_header_pointer(oldskb, oldskb->nh.iph->ihl * 4,
116 sizeof(_otcph), &_otcph);
120 /* No RST for RST. */
125 if (nf_ip_checksum(oldskb, hook, iph->ihl * 4, IPPROTO_TCP))
128 if ((rt = route_reverse(oldskb, oth, hook)) == NULL)
131 hh_len = LL_RESERVED_SPACE(rt->u.dst.dev);
133 /* We need a linear, writeable skb. We also need to expand
134 headroom in case hh_len of incoming interface < hh_len of
135 outgoing interface */
136 nskb = skb_copy_expand(oldskb, hh_len, skb_tailroom(oldskb),
139 dst_release(&rt->u.dst);
143 dst_release(nskb->dst);
144 nskb->dst = &rt->u.dst;
146 /* This packet will not be the same as the other: clear nf fields */
149 skb_init_secmark(nskb);
151 tcph = (struct tcphdr *)((u_int32_t*)nskb->nh.iph + nskb->nh.iph->ihl);
153 /* Swap source and dest */
154 tmp_addr = nskb->nh.iph->saddr;
155 nskb->nh.iph->saddr = nskb->nh.iph->daddr;
156 nskb->nh.iph->daddr = tmp_addr;
157 tmp_port = tcph->source;
158 tcph->source = tcph->dest;
159 tcph->dest = tmp_port;
161 /* Truncate to length (no data) */
162 tcph->doff = sizeof(struct tcphdr)/4;
163 skb_trim(nskb, nskb->nh.iph->ihl*4 + sizeof(struct tcphdr));
164 nskb->nh.iph->tot_len = htons(nskb->len);
168 tcph->seq = oth->ack_seq;
172 tcph->ack_seq = htonl(ntohl(oth->seq) + oth->syn + oth->fin
173 + oldskb->len - oldskb->nh.iph->ihl*4
179 ((u_int8_t *)tcph)[13] = 0;
181 tcph->ack = needs_ack;
186 /* Adjust TCP checksum */
188 tcph->check = tcp_v4_check(tcph, sizeof(struct tcphdr),
191 csum_partial((char *)tcph,
192 sizeof(struct tcphdr), 0));
194 /* Adjust IP TTL, DF */
195 nskb->nh.iph->ttl = dst_metric(nskb->dst, RTAX_HOPLIMIT);
197 nskb->nh.iph->frag_off = htons(IP_DF);
198 nskb->nh.iph->id = 0;
200 /* Adjust IP checksum */
201 nskb->nh.iph->check = 0;
202 nskb->nh.iph->check = ip_fast_csum((unsigned char *)nskb->nh.iph,
205 /* "Never happens" */
206 if (nskb->len > dst_mtu(nskb->dst))
209 nf_ct_attach(nskb, oldskb);
211 NF_HOOK(PF_INET, NF_IP_LOCAL_OUT, nskb, NULL, nskb->dst->dev,
219 static inline void send_unreach(struct sk_buff *skb_in, int code)
221 icmp_send(skb_in, ICMP_DEST_UNREACH, code, 0);
224 static unsigned int reject(struct sk_buff **pskb,
225 const struct net_device *in,
226 const struct net_device *out,
227 unsigned int hooknum,
228 const struct xt_target *target,
229 const void *targinfo,
232 const struct ipt_reject_info *reject = targinfo;
234 /* Our naive response construction doesn't deal with IP
235 options, and probably shouldn't try. */
236 if ((*pskb)->nh.iph->ihl<<2 != sizeof(struct iphdr))
239 /* WARNING: This code causes reentry within iptables.
240 This means that the iptables jump stack is now crap. We
241 must return an absolute verdict. --RR */
242 switch (reject->with) {
243 case IPT_ICMP_NET_UNREACHABLE:
244 send_unreach(*pskb, ICMP_NET_UNREACH);
246 case IPT_ICMP_HOST_UNREACHABLE:
247 send_unreach(*pskb, ICMP_HOST_UNREACH);
249 case IPT_ICMP_PROT_UNREACHABLE:
250 send_unreach(*pskb, ICMP_PROT_UNREACH);
252 case IPT_ICMP_PORT_UNREACHABLE:
253 send_unreach(*pskb, ICMP_PORT_UNREACH);
255 case IPT_ICMP_NET_PROHIBITED:
256 send_unreach(*pskb, ICMP_NET_ANO);
258 case IPT_ICMP_HOST_PROHIBITED:
259 send_unreach(*pskb, ICMP_HOST_ANO);
261 case IPT_ICMP_ADMIN_PROHIBITED:
262 send_unreach(*pskb, ICMP_PKT_FILTERED);
265 send_reset(*pskb, hooknum);
266 case IPT_ICMP_ECHOREPLY:
267 /* Doesn't happen. */
274 static int check(const char *tablename,
276 const struct xt_target *target,
278 unsigned int targinfosize,
279 unsigned int hook_mask)
281 const struct ipt_reject_info *rejinfo = targinfo;
282 const struct ipt_entry *e = e_void;
284 if (rejinfo->with == IPT_ICMP_ECHOREPLY) {
285 printk("REJECT: ECHOREPLY no longer supported.\n");
287 } else if (rejinfo->with == IPT_TCP_RESET) {
288 /* Must specify that it's a TCP packet */
289 if (e->ip.proto != IPPROTO_TCP
290 || (e->ip.invflags & IPT_INV_PROTO)) {
291 DEBUGP("REJECT: TCP_RESET invalid for non-tcp\n");
298 static struct ipt_target ipt_reject_reg = {
301 .targetsize = sizeof(struct ipt_reject_info),
303 .hooks = (1 << NF_IP_LOCAL_IN) | (1 << NF_IP_FORWARD) |
304 (1 << NF_IP_LOCAL_OUT),
309 static int __init ipt_reject_init(void)
311 return ipt_register_target(&ipt_reject_reg);
314 static void __exit ipt_reject_fini(void)
316 ipt_unregister_target(&ipt_reject_reg);
319 module_init(ipt_reject_init);
320 module_exit(ipt_reject_fini);