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...)
42 static void send_reset(struct sk_buff *oldskb, int hook)
45 struct iphdr *iph = oldskb->nh.iph;
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, oldskb->nh.iph->ihl * 4,
57 sizeof(_otcph), &_otcph);
66 if (nf_ip_checksum(oldskb, hook, iph->ihl * 4, 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 tcph = (struct tcphdr *)((u_int32_t*)nskb->nh.iph + nskb->nh.iph->ihl);
84 /* Swap source and dest */
85 tmp_addr = nskb->nh.iph->saddr;
86 nskb->nh.iph->saddr = nskb->nh.iph->daddr;
87 nskb->nh.iph->daddr = tmp_addr;
88 tmp_port = tcph->source;
89 tcph->source = tcph->dest;
90 tcph->dest = tmp_port;
92 /* Truncate to length (no data) */
93 tcph->doff = sizeof(struct tcphdr)/4;
94 skb_trim(nskb, nskb->nh.iph->ihl*4 + sizeof(struct tcphdr));
95 nskb->nh.iph->tot_len = htons(nskb->len);
99 tcph->seq = oth->ack_seq;
103 tcph->ack_seq = htonl(ntohl(oth->seq) + oth->syn + oth->fin
104 + oldskb->len - oldskb->nh.iph->ihl*4
110 ((u_int8_t *)tcph)[13] = 0;
112 tcph->ack = needs_ack;
118 nskb->nh.iph->frag_off = htons(IP_DF);
119 nskb->nh.iph->id = 0;
121 addr_type = RTN_UNSPEC;
122 if (hook != NF_IP_FORWARD
123 #ifdef CONFIG_BRIDGE_NETFILTER
124 || (nskb->nf_bridge && nskb->nf_bridge->mask & BRNF_BRIDGED)
127 addr_type = RTN_LOCAL;
129 if (ip_route_me_harder(&nskb, addr_type))
132 /* Adjust TCP checksum */
133 nskb->ip_summed = CHECKSUM_NONE;
135 tcph->check = tcp_v4_check(tcph, sizeof(struct tcphdr),
138 csum_partial((char *)tcph,
139 sizeof(struct tcphdr), 0));
141 nskb->nh.iph->ttl = dst_metric(nskb->dst, RTAX_HOPLIMIT);
143 /* Adjust IP checksum */
144 nskb->nh.iph->check = 0;
145 nskb->nh.iph->check = ip_fast_csum((unsigned char *)nskb->nh.iph,
148 /* "Never happens" */
149 if (nskb->len > dst_mtu(nskb->dst))
152 nf_ct_attach(nskb, oldskb);
154 NF_HOOK(PF_INET, NF_IP_LOCAL_OUT, nskb, NULL, nskb->dst->dev,
162 static inline void send_unreach(struct sk_buff *skb_in, int code)
164 icmp_send(skb_in, ICMP_DEST_UNREACH, code, 0);
167 static unsigned int reject(struct sk_buff **pskb,
168 const struct net_device *in,
169 const struct net_device *out,
170 unsigned int hooknum,
171 const struct xt_target *target,
172 const void *targinfo)
174 const struct ipt_reject_info *reject = targinfo;
176 /* Our naive response construction doesn't deal with IP
177 options, and probably shouldn't try. */
178 if ((*pskb)->nh.iph->ihl<<2 != sizeof(struct iphdr))
181 /* WARNING: This code causes reentry within iptables.
182 This means that the iptables jump stack is now crap. We
183 must return an absolute verdict. --RR */
184 switch (reject->with) {
185 case IPT_ICMP_NET_UNREACHABLE:
186 send_unreach(*pskb, ICMP_NET_UNREACH);
188 case IPT_ICMP_HOST_UNREACHABLE:
189 send_unreach(*pskb, ICMP_HOST_UNREACH);
191 case IPT_ICMP_PROT_UNREACHABLE:
192 send_unreach(*pskb, ICMP_PROT_UNREACH);
194 case IPT_ICMP_PORT_UNREACHABLE:
195 send_unreach(*pskb, ICMP_PORT_UNREACH);
197 case IPT_ICMP_NET_PROHIBITED:
198 send_unreach(*pskb, ICMP_NET_ANO);
200 case IPT_ICMP_HOST_PROHIBITED:
201 send_unreach(*pskb, ICMP_HOST_ANO);
203 case IPT_ICMP_ADMIN_PROHIBITED:
204 send_unreach(*pskb, ICMP_PKT_FILTERED);
207 send_reset(*pskb, hooknum);
208 case IPT_ICMP_ECHOREPLY:
209 /* Doesn't happen. */
216 static int check(const char *tablename,
218 const struct xt_target *target,
220 unsigned int hook_mask)
222 const struct ipt_reject_info *rejinfo = targinfo;
223 const struct ipt_entry *e = e_void;
225 if (rejinfo->with == IPT_ICMP_ECHOREPLY) {
226 printk("REJECT: ECHOREPLY no longer supported.\n");
228 } else if (rejinfo->with == IPT_TCP_RESET) {
229 /* Must specify that it's a TCP packet */
230 if (e->ip.proto != IPPROTO_TCP
231 || (e->ip.invflags & IPT_INV_PROTO)) {
232 DEBUGP("REJECT: TCP_RESET invalid for non-tcp\n");
239 static struct ipt_target ipt_reject_reg = {
242 .targetsize = sizeof(struct ipt_reject_info),
244 .hooks = (1 << NF_IP_LOCAL_IN) | (1 << NF_IP_FORWARD) |
245 (1 << NF_IP_LOCAL_OUT),
250 static int __init ipt_reject_init(void)
252 return ipt_register_target(&ipt_reject_reg);
255 static void __exit ipt_reject_fini(void)
257 ipt_unregister_target(&ipt_reject_reg);
260 module_init(ipt_reject_init);
261 module_exit(ipt_reject_fini);