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/config.h>
16 #include <linux/module.h>
17 #include <linux/skbuff.h>
19 #include <linux/udp.h>
20 #include <linux/icmp.h>
24 #include <net/route.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...)
42 static inline struct rtable
*route_reverse(struct sk_buff
*skb
,
43 struct tcphdr
*tcph
, int hook
)
45 struct iphdr
*iph
= skb
->nh
.iph
;
46 struct dst_entry
*odst
;
50 /* We don't require ip forwarding to be enabled to be able to
51 * send a RST reply for bridged traffic. */
52 if (hook
!= NF_IP_FORWARD
53 #ifdef CONFIG_BRIDGE_NETFILTER
54 || (skb
->nf_bridge
&& skb
->nf_bridge
->mask
& BRNF_BRIDGED
)
57 fl
.nl_u
.ip4_u
.daddr
= iph
->saddr
;
58 if (hook
== NF_IP_LOCAL_IN
)
59 fl
.nl_u
.ip4_u
.saddr
= iph
->daddr
;
60 fl
.nl_u
.ip4_u
.tos
= RT_TOS(iph
->tos
);
62 if (ip_route_output_key(&rt
, &fl
) != 0)
65 /* non-local src, find valid iif to satisfy
66 * rp-filter when calling ip_route_input. */
67 fl
.nl_u
.ip4_u
.daddr
= iph
->daddr
;
68 if (ip_route_output_key(&rt
, &fl
) != 0)
72 if (ip_route_input(skb
, iph
->saddr
, iph
->daddr
,
73 RT_TOS(iph
->tos
), rt
->u
.dst
.dev
) != 0) {
74 dst_release(&rt
->u
.dst
);
77 dst_release(&rt
->u
.dst
);
78 rt
= (struct rtable
*)skb
->dst
;
81 fl
.nl_u
.ip4_u
.daddr
= iph
->saddr
;
82 fl
.nl_u
.ip4_u
.saddr
= iph
->daddr
;
83 fl
.nl_u
.ip4_u
.tos
= RT_TOS(iph
->tos
);
86 if (rt
->u
.dst
.error
) {
87 dst_release(&rt
->u
.dst
);
91 fl
.proto
= IPPROTO_TCP
;
92 fl
.fl_ip_sport
= tcph
->dest
;
93 fl
.fl_ip_dport
= tcph
->source
;
95 xfrm_lookup((struct dst_entry
**)&rt
, &fl
, NULL
, 0);
101 static void send_reset(struct sk_buff
*oldskb
, int hook
)
103 struct sk_buff
*nskb
;
104 struct iphdr
*iph
= oldskb
->nh
.iph
;
105 struct tcphdr _otcph
, *oth
, *tcph
;
113 /* IP header checks: fragment. */
114 if (oldskb
->nh
.iph
->frag_off
& htons(IP_OFFSET
))
117 oth
= skb_header_pointer(oldskb
, oldskb
->nh
.iph
->ihl
* 4,
118 sizeof(_otcph
), &_otcph
);
122 /* No RST for RST. */
127 tcplen
= oldskb
->len
- iph
->ihl
* 4;
128 if (((hook
!= NF_IP_LOCAL_IN
&& oldskb
->ip_summed
!= CHECKSUM_HW
) ||
129 (hook
== NF_IP_LOCAL_IN
&&
130 oldskb
->ip_summed
!= CHECKSUM_UNNECESSARY
)) &&
131 csum_tcpudp_magic(iph
->saddr
, iph
->daddr
, tcplen
, IPPROTO_TCP
,
132 oldskb
->ip_summed
== CHECKSUM_HW
? oldskb
->csum
:
133 skb_checksum(oldskb
, iph
->ihl
* 4, tcplen
, 0)))
136 if ((rt
= route_reverse(oldskb
, oth
, hook
)) == NULL
)
139 hh_len
= LL_RESERVED_SPACE(rt
->u
.dst
.dev
);
141 /* We need a linear, writeable skb. We also need to expand
142 headroom in case hh_len of incoming interface < hh_len of
143 outgoing interface */
144 nskb
= skb_copy_expand(oldskb
, hh_len
, skb_tailroom(oldskb
),
147 dst_release(&rt
->u
.dst
);
151 dst_release(nskb
->dst
);
152 nskb
->dst
= &rt
->u
.dst
;
154 /* This packet will not be the same as the other: clear nf fields */
157 #ifdef CONFIG_BRIDGE_NETFILTER
158 nf_bridge_put(nskb
->nf_bridge
);
159 nskb
->nf_bridge
= NULL
;
162 tcph
= (struct tcphdr
*)((u_int32_t
*)nskb
->nh
.iph
+ nskb
->nh
.iph
->ihl
);
164 /* Swap source and dest */
165 tmp_addr
= nskb
->nh
.iph
->saddr
;
166 nskb
->nh
.iph
->saddr
= nskb
->nh
.iph
->daddr
;
167 nskb
->nh
.iph
->daddr
= tmp_addr
;
168 tmp_port
= tcph
->source
;
169 tcph
->source
= tcph
->dest
;
170 tcph
->dest
= tmp_port
;
172 /* Truncate to length (no data) */
173 tcph
->doff
= sizeof(struct tcphdr
)/4;
174 skb_trim(nskb
, nskb
->nh
.iph
->ihl
*4 + sizeof(struct tcphdr
));
175 nskb
->nh
.iph
->tot_len
= htons(nskb
->len
);
179 tcph
->seq
= oth
->ack_seq
;
183 tcph
->ack_seq
= htonl(ntohl(oth
->seq
) + oth
->syn
+ oth
->fin
184 + oldskb
->len
- oldskb
->nh
.iph
->ihl
*4
190 ((u_int8_t
*)tcph
)[13] = 0;
192 tcph
->ack
= needs_ack
;
197 /* Adjust TCP checksum */
199 tcph
->check
= tcp_v4_check(tcph
, sizeof(struct tcphdr
),
202 csum_partial((char *)tcph
,
203 sizeof(struct tcphdr
), 0));
205 /* Adjust IP TTL, DF */
206 nskb
->nh
.iph
->ttl
= dst_metric(nskb
->dst
, RTAX_HOPLIMIT
);
208 nskb
->nh
.iph
->frag_off
= htons(IP_DF
);
209 nskb
->nh
.iph
->id
= 0;
211 /* Adjust IP checksum */
212 nskb
->nh
.iph
->check
= 0;
213 nskb
->nh
.iph
->check
= ip_fast_csum((unsigned char *)nskb
->nh
.iph
,
216 /* "Never happens" */
217 if (nskb
->len
> dst_mtu(nskb
->dst
))
220 nf_ct_attach(nskb
, oldskb
);
222 NF_HOOK(PF_INET
, NF_IP_LOCAL_OUT
, nskb
, NULL
, nskb
->dst
->dev
,
230 static inline void send_unreach(struct sk_buff
*skb_in
, int code
)
232 icmp_send(skb_in
, ICMP_DEST_UNREACH
, code
, 0);
235 static unsigned int reject(struct sk_buff
**pskb
,
236 const struct net_device
*in
,
237 const struct net_device
*out
,
238 unsigned int hooknum
,
239 const struct xt_target
*target
,
240 const void *targinfo
,
243 const struct ipt_reject_info
*reject
= targinfo
;
245 /* Our naive response construction doesn't deal with IP
246 options, and probably shouldn't try. */
247 if ((*pskb
)->nh
.iph
->ihl
<<2 != sizeof(struct iphdr
))
250 /* WARNING: This code causes reentry within iptables.
251 This means that the iptables jump stack is now crap. We
252 must return an absolute verdict. --RR */
253 switch (reject
->with
) {
254 case IPT_ICMP_NET_UNREACHABLE
:
255 send_unreach(*pskb
, ICMP_NET_UNREACH
);
257 case IPT_ICMP_HOST_UNREACHABLE
:
258 send_unreach(*pskb
, ICMP_HOST_UNREACH
);
260 case IPT_ICMP_PROT_UNREACHABLE
:
261 send_unreach(*pskb
, ICMP_PROT_UNREACH
);
263 case IPT_ICMP_PORT_UNREACHABLE
:
264 send_unreach(*pskb
, ICMP_PORT_UNREACH
);
266 case IPT_ICMP_NET_PROHIBITED
:
267 send_unreach(*pskb
, ICMP_NET_ANO
);
269 case IPT_ICMP_HOST_PROHIBITED
:
270 send_unreach(*pskb
, ICMP_HOST_ANO
);
272 case IPT_ICMP_ADMIN_PROHIBITED
:
273 send_unreach(*pskb
, ICMP_PKT_FILTERED
);
276 send_reset(*pskb
, hooknum
);
277 case IPT_ICMP_ECHOREPLY
:
278 /* Doesn't happen. */
285 static int check(const char *tablename
,
287 const struct xt_target
*target
,
289 unsigned int targinfosize
,
290 unsigned int hook_mask
)
292 const struct ipt_reject_info
*rejinfo
= targinfo
;
293 const struct ipt_entry
*e
= e_void
;
295 if (rejinfo
->with
== IPT_ICMP_ECHOREPLY
) {
296 printk("REJECT: ECHOREPLY no longer supported.\n");
298 } else if (rejinfo
->with
== IPT_TCP_RESET
) {
299 /* Must specify that it's a TCP packet */
300 if (e
->ip
.proto
!= IPPROTO_TCP
301 || (e
->ip
.invflags
& IPT_INV_PROTO
)) {
302 DEBUGP("REJECT: TCP_RESET invalid for non-tcp\n");
309 static struct ipt_target ipt_reject_reg
= {
312 .targetsize
= sizeof(struct ipt_reject_info
),
314 .hooks
= (1 << NF_IP_LOCAL_IN
) | (1 << NF_IP_FORWARD
) |
315 (1 << NF_IP_LOCAL_OUT
),
320 static int __init
init(void)
322 return ipt_register_target(&ipt_reject_reg
);
325 static void __exit
fini(void)
327 ipt_unregister_target(&ipt_reject_reg
);