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 iphdr *iph = oldskb->nh.iph;
47 struct tcphdr _otcph, *oth, *tcph;
51 unsigned int addr_type;
53 /* IP header checks: fragment. */
54 if (oldskb->nh.iph->frag_off & htons(IP_OFFSET))
57 oth = skb_header_pointer(oldskb, oldskb->nh.iph->ihl * 4,
58 sizeof(_otcph), &_otcph);
67 if (nf_ip_checksum(oldskb, hook, iph->ihl * 4, IPPROTO_TCP))
70 /* We need a linear, writeable skb. We also need to expand
71 headroom in case hh_len of incoming interface < hh_len of
73 nskb = skb_copy_expand(oldskb, LL_MAX_HEADER, skb_tailroom(oldskb),
78 /* This packet will not be the same as the other: clear nf fields */
81 skb_init_secmark(nskb);
83 skb_shinfo(nskb)->gso_size = 0;
84 skb_shinfo(nskb)->gso_segs = 0;
85 skb_shinfo(nskb)->gso_type = 0;
87 tcph = (struct tcphdr *)((u_int32_t*)nskb->nh.iph + nskb->nh.iph->ihl);
89 /* Swap source and dest */
90 tmp_addr = nskb->nh.iph->saddr;
91 nskb->nh.iph->saddr = nskb->nh.iph->daddr;
92 nskb->nh.iph->daddr = tmp_addr;
93 tmp_port = tcph->source;
94 tcph->source = tcph->dest;
95 tcph->dest = tmp_port;
97 /* Truncate to length (no data) */
98 tcph->doff = sizeof(struct tcphdr)/4;
99 skb_trim(nskb, nskb->nh.iph->ihl*4 + sizeof(struct tcphdr));
100 nskb->nh.iph->tot_len = htons(nskb->len);
104 tcph->seq = oth->ack_seq;
108 tcph->ack_seq = htonl(ntohl(oth->seq) + oth->syn + oth->fin
109 + oldskb->len - oldskb->nh.iph->ihl*4
115 ((u_int8_t *)tcph)[13] = 0;
117 tcph->ack = needs_ack;
122 /* Adjust TCP checksum */
124 tcph->check = tcp_v4_check(sizeof(struct tcphdr),
127 csum_partial((char *)tcph,
128 sizeof(struct tcphdr), 0));
131 nskb->nh.iph->frag_off = htons(IP_DF);
132 nskb->nh.iph->id = 0;
134 addr_type = RTN_UNSPEC;
135 if (hook != NF_IP_FORWARD
136 #ifdef CONFIG_BRIDGE_NETFILTER
137 || (nskb->nf_bridge && nskb->nf_bridge->mask & BRNF_BRIDGED)
140 addr_type = RTN_LOCAL;
142 if (ip_route_me_harder(&nskb, addr_type))
145 nskb->ip_summed = CHECKSUM_NONE;
148 nskb->nh.iph->ttl = dst_metric(nskb->dst, RTAX_HOPLIMIT);
150 /* Adjust IP checksum */
151 nskb->nh.iph->check = 0;
152 nskb->nh.iph->check = ip_fast_csum((unsigned char *)nskb->nh.iph,
155 /* "Never happens" */
156 if (nskb->len > dst_mtu(nskb->dst))
159 nf_ct_attach(nskb, oldskb);
161 NF_HOOK(PF_INET, NF_IP_LOCAL_OUT, nskb, NULL, nskb->dst->dev,
169 static inline void send_unreach(struct sk_buff *skb_in, int code)
171 icmp_send(skb_in, ICMP_DEST_UNREACH, code, 0);
174 static unsigned int reject(struct sk_buff **pskb,
175 const struct net_device *in,
176 const struct net_device *out,
177 unsigned int hooknum,
178 const struct xt_target *target,
179 const void *targinfo)
181 const struct ipt_reject_info *reject = targinfo;
183 /* Our naive response construction doesn't deal with IP
184 options, and probably shouldn't try. */
185 if ((*pskb)->nh.iph->ihl<<2 != sizeof(struct iphdr))
188 /* WARNING: This code causes reentry within iptables.
189 This means that the iptables jump stack is now crap. We
190 must return an absolute verdict. --RR */
191 switch (reject->with) {
192 case IPT_ICMP_NET_UNREACHABLE:
193 send_unreach(*pskb, ICMP_NET_UNREACH);
195 case IPT_ICMP_HOST_UNREACHABLE:
196 send_unreach(*pskb, ICMP_HOST_UNREACH);
198 case IPT_ICMP_PROT_UNREACHABLE:
199 send_unreach(*pskb, ICMP_PROT_UNREACH);
201 case IPT_ICMP_PORT_UNREACHABLE:
202 send_unreach(*pskb, ICMP_PORT_UNREACH);
204 case IPT_ICMP_NET_PROHIBITED:
205 send_unreach(*pskb, ICMP_NET_ANO);
207 case IPT_ICMP_HOST_PROHIBITED:
208 send_unreach(*pskb, ICMP_HOST_ANO);
210 case IPT_ICMP_ADMIN_PROHIBITED:
211 send_unreach(*pskb, ICMP_PKT_FILTERED);
214 send_reset(*pskb, hooknum);
215 case IPT_ICMP_ECHOREPLY:
216 /* Doesn't happen. */
223 static int check(const char *tablename,
225 const struct xt_target *target,
227 unsigned int hook_mask)
229 const struct ipt_reject_info *rejinfo = targinfo;
230 const struct ipt_entry *e = e_void;
232 if (rejinfo->with == IPT_ICMP_ECHOREPLY) {
233 printk("REJECT: ECHOREPLY no longer supported.\n");
235 } else if (rejinfo->with == IPT_TCP_RESET) {
236 /* Must specify that it's a TCP packet */
237 if (e->ip.proto != IPPROTO_TCP
238 || (e->ip.invflags & XT_INV_PROTO)) {
239 DEBUGP("REJECT: TCP_RESET invalid for non-tcp\n");
246 static struct xt_target ipt_reject_reg = {
250 .targetsize = sizeof(struct ipt_reject_info),
252 .hooks = (1 << NF_IP_LOCAL_IN) | (1 << NF_IP_FORWARD) |
253 (1 << NF_IP_LOCAL_OUT),
258 static int __init ipt_reject_init(void)
260 return xt_register_target(&ipt_reject_reg);
263 static void __exit ipt_reject_fini(void)
265 xt_unregister_target(&ipt_reject_reg);
268 module_init(ipt_reject_init);
269 module_exit(ipt_reject_fini);