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 tcph
= (struct tcphdr
*)((u_int32_t
*)nskb
->nh
.iph
+ nskb
->nh
.iph
->ihl
);
85 /* Swap source and dest */
86 tmp_addr
= nskb
->nh
.iph
->saddr
;
87 nskb
->nh
.iph
->saddr
= nskb
->nh
.iph
->daddr
;
88 nskb
->nh
.iph
->daddr
= tmp_addr
;
89 tmp_port
= tcph
->source
;
90 tcph
->source
= tcph
->dest
;
91 tcph
->dest
= tmp_port
;
93 /* Truncate to length (no data) */
94 tcph
->doff
= sizeof(struct tcphdr
)/4;
95 skb_trim(nskb
, nskb
->nh
.iph
->ihl
*4 + sizeof(struct tcphdr
));
96 nskb
->nh
.iph
->tot_len
= htons(nskb
->len
);
100 tcph
->seq
= oth
->ack_seq
;
104 tcph
->ack_seq
= htonl(ntohl(oth
->seq
) + oth
->syn
+ oth
->fin
105 + oldskb
->len
- oldskb
->nh
.iph
->ihl
*4
111 ((u_int8_t
*)tcph
)[13] = 0;
113 tcph
->ack
= needs_ack
;
118 /* Adjust TCP checksum */
120 tcph
->check
= tcp_v4_check(sizeof(struct tcphdr
),
123 csum_partial((char *)tcph
,
124 sizeof(struct tcphdr
), 0));
127 nskb
->nh
.iph
->frag_off
= htons(IP_DF
);
128 nskb
->nh
.iph
->id
= 0;
130 addr_type
= RTN_UNSPEC
;
131 if (hook
!= NF_IP_FORWARD
132 #ifdef CONFIG_BRIDGE_NETFILTER
133 || (nskb
->nf_bridge
&& nskb
->nf_bridge
->mask
& BRNF_BRIDGED
)
136 addr_type
= RTN_LOCAL
;
138 if (ip_route_me_harder(&nskb
, addr_type
))
141 nskb
->ip_summed
= CHECKSUM_NONE
;
144 nskb
->nh
.iph
->ttl
= dst_metric(nskb
->dst
, RTAX_HOPLIMIT
);
146 /* Adjust IP checksum */
147 nskb
->nh
.iph
->check
= 0;
148 nskb
->nh
.iph
->check
= ip_fast_csum((unsigned char *)nskb
->nh
.iph
,
151 /* "Never happens" */
152 if (nskb
->len
> dst_mtu(nskb
->dst
))
155 nf_ct_attach(nskb
, oldskb
);
157 NF_HOOK(PF_INET
, NF_IP_LOCAL_OUT
, nskb
, NULL
, nskb
->dst
->dev
,
165 static inline void send_unreach(struct sk_buff
*skb_in
, int code
)
167 icmp_send(skb_in
, ICMP_DEST_UNREACH
, code
, 0);
170 static unsigned int reject(struct sk_buff
**pskb
,
171 const struct net_device
*in
,
172 const struct net_device
*out
,
173 unsigned int hooknum
,
174 const struct xt_target
*target
,
175 const void *targinfo
)
177 const struct ipt_reject_info
*reject
= targinfo
;
179 /* Our naive response construction doesn't deal with IP
180 options, and probably shouldn't try. */
181 if ((*pskb
)->nh
.iph
->ihl
<<2 != sizeof(struct iphdr
))
184 /* WARNING: This code causes reentry within iptables.
185 This means that the iptables jump stack is now crap. We
186 must return an absolute verdict. --RR */
187 switch (reject
->with
) {
188 case IPT_ICMP_NET_UNREACHABLE
:
189 send_unreach(*pskb
, ICMP_NET_UNREACH
);
191 case IPT_ICMP_HOST_UNREACHABLE
:
192 send_unreach(*pskb
, ICMP_HOST_UNREACH
);
194 case IPT_ICMP_PROT_UNREACHABLE
:
195 send_unreach(*pskb
, ICMP_PROT_UNREACH
);
197 case IPT_ICMP_PORT_UNREACHABLE
:
198 send_unreach(*pskb
, ICMP_PORT_UNREACH
);
200 case IPT_ICMP_NET_PROHIBITED
:
201 send_unreach(*pskb
, ICMP_NET_ANO
);
203 case IPT_ICMP_HOST_PROHIBITED
:
204 send_unreach(*pskb
, ICMP_HOST_ANO
);
206 case IPT_ICMP_ADMIN_PROHIBITED
:
207 send_unreach(*pskb
, ICMP_PKT_FILTERED
);
210 send_reset(*pskb
, hooknum
);
211 case IPT_ICMP_ECHOREPLY
:
212 /* Doesn't happen. */
219 static int check(const char *tablename
,
221 const struct xt_target
*target
,
223 unsigned int hook_mask
)
225 const struct ipt_reject_info
*rejinfo
= targinfo
;
226 const struct ipt_entry
*e
= e_void
;
228 if (rejinfo
->with
== IPT_ICMP_ECHOREPLY
) {
229 printk("REJECT: ECHOREPLY no longer supported.\n");
231 } else if (rejinfo
->with
== IPT_TCP_RESET
) {
232 /* Must specify that it's a TCP packet */
233 if (e
->ip
.proto
!= IPPROTO_TCP
234 || (e
->ip
.invflags
& XT_INV_PROTO
)) {
235 DEBUGP("REJECT: TCP_RESET invalid for non-tcp\n");
242 static struct xt_target ipt_reject_reg
= {
246 .targetsize
= sizeof(struct ipt_reject_info
),
248 .hooks
= (1 << NF_IP_LOCAL_IN
) | (1 << NF_IP_FORWARD
) |
249 (1 << NF_IP_LOCAL_OUT
),
254 static int __init
ipt_reject_init(void)
256 return xt_register_target(&ipt_reject_reg
);
259 static void __exit
ipt_reject_fini(void)
261 xt_unregister_target(&ipt_reject_reg
);
264 module_init(ipt_reject_init
);
265 module_exit(ipt_reject_fini
);