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
;
117 /* Adjust TCP checksum */
119 tcph
->check
= tcp_v4_check(tcph
, sizeof(struct tcphdr
),
122 csum_partial((char *)tcph
,
123 sizeof(struct tcphdr
), 0));
126 nskb
->nh
.iph
->frag_off
= htons(IP_DF
);
127 nskb
->nh
.iph
->id
= 0;
129 addr_type
= RTN_UNSPEC
;
130 if (hook
!= NF_IP_FORWARD
131 #ifdef CONFIG_BRIDGE_NETFILTER
132 || (nskb
->nf_bridge
&& nskb
->nf_bridge
->mask
& BRNF_BRIDGED
)
135 addr_type
= RTN_LOCAL
;
137 if (ip_route_me_harder(&nskb
, addr_type
))
140 nskb
->ip_summed
= CHECKSUM_NONE
;
143 nskb
->nh
.iph
->ttl
= dst_metric(nskb
->dst
, RTAX_HOPLIMIT
);
145 /* Adjust IP checksum */
146 nskb
->nh
.iph
->check
= 0;
147 nskb
->nh
.iph
->check
= ip_fast_csum((unsigned char *)nskb
->nh
.iph
,
150 /* "Never happens" */
151 if (nskb
->len
> dst_mtu(nskb
->dst
))
154 nf_ct_attach(nskb
, oldskb
);
156 NF_HOOK(PF_INET
, NF_IP_LOCAL_OUT
, nskb
, NULL
, nskb
->dst
->dev
,
164 static inline void send_unreach(struct sk_buff
*skb_in
, int code
)
166 icmp_send(skb_in
, ICMP_DEST_UNREACH
, code
, 0);
169 static unsigned int reject(struct sk_buff
**pskb
,
170 const struct net_device
*in
,
171 const struct net_device
*out
,
172 unsigned int hooknum
,
173 const struct xt_target
*target
,
174 const void *targinfo
)
176 const struct ipt_reject_info
*reject
= targinfo
;
178 /* Our naive response construction doesn't deal with IP
179 options, and probably shouldn't try. */
180 if ((*pskb
)->nh
.iph
->ihl
<<2 != sizeof(struct iphdr
))
183 /* WARNING: This code causes reentry within iptables.
184 This means that the iptables jump stack is now crap. We
185 must return an absolute verdict. --RR */
186 switch (reject
->with
) {
187 case IPT_ICMP_NET_UNREACHABLE
:
188 send_unreach(*pskb
, ICMP_NET_UNREACH
);
190 case IPT_ICMP_HOST_UNREACHABLE
:
191 send_unreach(*pskb
, ICMP_HOST_UNREACH
);
193 case IPT_ICMP_PROT_UNREACHABLE
:
194 send_unreach(*pskb
, ICMP_PROT_UNREACH
);
196 case IPT_ICMP_PORT_UNREACHABLE
:
197 send_unreach(*pskb
, ICMP_PORT_UNREACH
);
199 case IPT_ICMP_NET_PROHIBITED
:
200 send_unreach(*pskb
, ICMP_NET_ANO
);
202 case IPT_ICMP_HOST_PROHIBITED
:
203 send_unreach(*pskb
, ICMP_HOST_ANO
);
205 case IPT_ICMP_ADMIN_PROHIBITED
:
206 send_unreach(*pskb
, ICMP_PKT_FILTERED
);
209 send_reset(*pskb
, hooknum
);
210 case IPT_ICMP_ECHOREPLY
:
211 /* Doesn't happen. */
218 static int check(const char *tablename
,
220 const struct xt_target
*target
,
222 unsigned int hook_mask
)
224 const struct ipt_reject_info
*rejinfo
= targinfo
;
225 const struct ipt_entry
*e
= e_void
;
227 if (rejinfo
->with
== IPT_ICMP_ECHOREPLY
) {
228 printk("REJECT: ECHOREPLY no longer supported.\n");
230 } else if (rejinfo
->with
== IPT_TCP_RESET
) {
231 /* Must specify that it's a TCP packet */
232 if (e
->ip
.proto
!= IPPROTO_TCP
233 || (e
->ip
.invflags
& IPT_INV_PROTO
)) {
234 DEBUGP("REJECT: TCP_RESET invalid for non-tcp\n");
241 static struct ipt_target ipt_reject_reg
= {
244 .targetsize
= sizeof(struct ipt_reject_info
),
246 .hooks
= (1 << NF_IP_LOCAL_IN
) | (1 << NF_IP_FORWARD
) |
247 (1 << NF_IP_LOCAL_OUT
),
252 static int __init
ipt_reject_init(void)
254 return ipt_register_target(&ipt_reject_reg
);
257 static void __exit
ipt_reject_fini(void)
259 ipt_unregister_target(&ipt_reject_reg
);
262 module_init(ipt_reject_init
);
263 module_exit(ipt_reject_fini
);