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/x_tables.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...)
43 static void send_reset(struct sk_buff *oldskb, int hook)
46 struct tcphdr _otcph, *oth, *tcph;
50 unsigned int addr_type;
52 /* IP header checks: fragment. */
53 if (oldskb->nh.iph->frag_off & htons(IP_OFFSET))
56 oth = skb_header_pointer(oldskb, ip_hdrlen(oldskb),
57 sizeof(_otcph), &_otcph);
66 if (nf_ip_checksum(oldskb, hook, ip_hdrlen(oldskb), IPPROTO_TCP))
69 /* We need a linear, writeable skb. We also need to expand
70 headroom in case hh_len of incoming interface < hh_len of
72 nskb = skb_copy_expand(oldskb, LL_MAX_HEADER, skb_tailroom(oldskb),
77 /* This packet will not be the same as the other: clear nf fields */
80 skb_init_secmark(nskb);
82 skb_shinfo(nskb)->gso_size = 0;
83 skb_shinfo(nskb)->gso_segs = 0;
84 skb_shinfo(nskb)->gso_type = 0;
86 tcph = (struct tcphdr *)(skb_network_header(nskb) + ip_hdrlen(nskb));
88 /* Swap source and dest */
89 tmp_addr = nskb->nh.iph->saddr;
90 nskb->nh.iph->saddr = nskb->nh.iph->daddr;
91 nskb->nh.iph->daddr = tmp_addr;
92 tmp_port = tcph->source;
93 tcph->source = tcph->dest;
94 tcph->dest = tmp_port;
96 /* Truncate to length (no data) */
97 tcph->doff = sizeof(struct tcphdr)/4;
98 skb_trim(nskb, ip_hdrlen(nskb) + sizeof(struct tcphdr));
99 nskb->nh.iph->tot_len = htons(nskb->len);
103 tcph->seq = oth->ack_seq;
107 tcph->ack_seq = htonl(ntohl(oth->seq) + oth->syn + oth->fin +
108 oldskb->len - ip_hdrlen(oldskb) -
114 ((u_int8_t *)tcph)[13] = 0;
116 tcph->ack = needs_ack;
121 /* Adjust TCP checksum */
123 tcph->check = tcp_v4_check(sizeof(struct tcphdr),
126 csum_partial((char *)tcph,
127 sizeof(struct tcphdr), 0));
130 nskb->nh.iph->frag_off = htons(IP_DF);
131 nskb->nh.iph->id = 0;
133 addr_type = RTN_UNSPEC;
134 if (hook != NF_IP_FORWARD
135 #ifdef CONFIG_BRIDGE_NETFILTER
136 || (nskb->nf_bridge && nskb->nf_bridge->mask & BRNF_BRIDGED)
139 addr_type = RTN_LOCAL;
141 if (ip_route_me_harder(&nskb, addr_type))
144 nskb->ip_summed = CHECKSUM_NONE;
147 nskb->nh.iph->ttl = dst_metric(nskb->dst, RTAX_HOPLIMIT);
149 /* Adjust IP checksum */
150 nskb->nh.iph->check = 0;
151 nskb->nh.iph->check = ip_fast_csum(skb_network_header(nskb),
154 /* "Never happens" */
155 if (nskb->len > dst_mtu(nskb->dst))
158 nf_ct_attach(nskb, oldskb);
160 NF_HOOK(PF_INET, NF_IP_LOCAL_OUT, nskb, NULL, nskb->dst->dev,
168 static inline void send_unreach(struct sk_buff *skb_in, int code)
170 icmp_send(skb_in, ICMP_DEST_UNREACH, code, 0);
173 static unsigned int reject(struct sk_buff **pskb,
174 const struct net_device *in,
175 const struct net_device *out,
176 unsigned int hooknum,
177 const struct xt_target *target,
178 const void *targinfo)
180 const struct ipt_reject_info *reject = targinfo;
182 /* Our naive response construction doesn't deal with IP
183 options, and probably shouldn't try. */
184 if (ip_hdrlen(*pskb) != sizeof(struct iphdr))
187 /* WARNING: This code causes reentry within iptables.
188 This means that the iptables jump stack is now crap. We
189 must return an absolute verdict. --RR */
190 switch (reject->with) {
191 case IPT_ICMP_NET_UNREACHABLE:
192 send_unreach(*pskb, ICMP_NET_UNREACH);
194 case IPT_ICMP_HOST_UNREACHABLE:
195 send_unreach(*pskb, ICMP_HOST_UNREACH);
197 case IPT_ICMP_PROT_UNREACHABLE:
198 send_unreach(*pskb, ICMP_PROT_UNREACH);
200 case IPT_ICMP_PORT_UNREACHABLE:
201 send_unreach(*pskb, ICMP_PORT_UNREACH);
203 case IPT_ICMP_NET_PROHIBITED:
204 send_unreach(*pskb, ICMP_NET_ANO);
206 case IPT_ICMP_HOST_PROHIBITED:
207 send_unreach(*pskb, ICMP_HOST_ANO);
209 case IPT_ICMP_ADMIN_PROHIBITED:
210 send_unreach(*pskb, ICMP_PKT_FILTERED);
213 send_reset(*pskb, hooknum);
214 case IPT_ICMP_ECHOREPLY:
215 /* Doesn't happen. */
222 static int check(const char *tablename,
224 const struct xt_target *target,
226 unsigned int hook_mask)
228 const struct ipt_reject_info *rejinfo = targinfo;
229 const struct ipt_entry *e = e_void;
231 if (rejinfo->with == IPT_ICMP_ECHOREPLY) {
232 printk("REJECT: ECHOREPLY no longer supported.\n");
234 } else if (rejinfo->with == IPT_TCP_RESET) {
235 /* Must specify that it's a TCP packet */
236 if (e->ip.proto != IPPROTO_TCP
237 || (e->ip.invflags & XT_INV_PROTO)) {
238 DEBUGP("REJECT: TCP_RESET invalid for non-tcp\n");
245 static struct xt_target ipt_reject_reg = {
249 .targetsize = sizeof(struct ipt_reject_info),
251 .hooks = (1 << NF_IP_LOCAL_IN) | (1 << NF_IP_FORWARD) |
252 (1 << NF_IP_LOCAL_OUT),
257 static int __init ipt_reject_init(void)
259 return xt_register_target(&ipt_reject_reg);
262 static void __exit ipt_reject_fini(void)
264 xt_unregister_target(&ipt_reject_reg);
267 module_init(ipt_reject_init);
268 module_exit(ipt_reject_fini);