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...)
41 static inline struct rtable
*route_reverse(struct sk_buff
*skb
,
42 struct tcphdr
*tcph
, int hook
)
44 struct iphdr
*iph
= skb
->nh
.iph
;
45 struct dst_entry
*odst
;
49 /* We don't require ip forwarding to be enabled to be able to
50 * send a RST reply for bridged traffic. */
51 if (hook
!= NF_IP_FORWARD
52 #ifdef CONFIG_BRIDGE_NETFILTER
53 || (skb
->nf_bridge
&& skb
->nf_bridge
->mask
& BRNF_BRIDGED
)
56 fl
.nl_u
.ip4_u
.daddr
= iph
->saddr
;
57 if (hook
== NF_IP_LOCAL_IN
)
58 fl
.nl_u
.ip4_u
.saddr
= iph
->daddr
;
59 fl
.nl_u
.ip4_u
.tos
= RT_TOS(iph
->tos
);
61 if (ip_route_output_key(&rt
, &fl
) != 0)
64 /* non-local src, find valid iif to satisfy
65 * rp-filter when calling ip_route_input. */
66 fl
.nl_u
.ip4_u
.daddr
= iph
->daddr
;
67 if (ip_route_output_key(&rt
, &fl
) != 0)
71 if (ip_route_input(skb
, iph
->saddr
, iph
->daddr
,
72 RT_TOS(iph
->tos
), rt
->u
.dst
.dev
) != 0) {
73 dst_release(&rt
->u
.dst
);
76 dst_release(&rt
->u
.dst
);
77 rt
= (struct rtable
*)skb
->dst
;
80 fl
.nl_u
.ip4_u
.daddr
= iph
->saddr
;
81 fl
.nl_u
.ip4_u
.saddr
= iph
->daddr
;
82 fl
.nl_u
.ip4_u
.tos
= RT_TOS(iph
->tos
);
85 if (rt
->u
.dst
.error
) {
86 dst_release(&rt
->u
.dst
);
90 fl
.proto
= IPPROTO_TCP
;
91 fl
.fl_ip_sport
= tcph
->dest
;
92 fl
.fl_ip_dport
= tcph
->source
;
93 security_skb_classify_flow(skb
, &fl
);
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
;
112 /* IP header checks: fragment. */
113 if (oldskb
->nh
.iph
->frag_off
& htons(IP_OFFSET
))
116 oth
= skb_header_pointer(oldskb
, oldskb
->nh
.iph
->ihl
* 4,
117 sizeof(_otcph
), &_otcph
);
121 /* No RST for RST. */
126 if (nf_ip_checksum(oldskb
, hook
, iph
->ihl
* 4, IPPROTO_TCP
))
129 if ((rt
= route_reverse(oldskb
, oth
, hook
)) == NULL
)
132 hh_len
= LL_RESERVED_SPACE(rt
->u
.dst
.dev
);
134 /* We need a linear, writeable skb. We also need to expand
135 headroom in case hh_len of incoming interface < hh_len of
136 outgoing interface */
137 nskb
= skb_copy_expand(oldskb
, hh_len
, skb_tailroom(oldskb
),
140 dst_release(&rt
->u
.dst
);
144 dst_release(nskb
->dst
);
145 nskb
->dst
= &rt
->u
.dst
;
147 /* This packet will not be the same as the other: clear nf fields */
150 skb_init_secmark(nskb
);
152 tcph
= (struct tcphdr
*)((u_int32_t
*)nskb
->nh
.iph
+ nskb
->nh
.iph
->ihl
);
154 /* Swap source and dest */
155 tmp_addr
= nskb
->nh
.iph
->saddr
;
156 nskb
->nh
.iph
->saddr
= nskb
->nh
.iph
->daddr
;
157 nskb
->nh
.iph
->daddr
= tmp_addr
;
158 tmp_port
= tcph
->source
;
159 tcph
->source
= tcph
->dest
;
160 tcph
->dest
= tmp_port
;
162 /* Truncate to length (no data) */
163 tcph
->doff
= sizeof(struct tcphdr
)/4;
164 skb_trim(nskb
, nskb
->nh
.iph
->ihl
*4 + sizeof(struct tcphdr
));
165 nskb
->nh
.iph
->tot_len
= htons(nskb
->len
);
169 tcph
->seq
= oth
->ack_seq
;
173 tcph
->ack_seq
= htonl(ntohl(oth
->seq
) + oth
->syn
+ oth
->fin
174 + oldskb
->len
- oldskb
->nh
.iph
->ihl
*4
180 ((u_int8_t
*)tcph
)[13] = 0;
182 tcph
->ack
= needs_ack
;
187 /* Adjust TCP checksum */
188 nskb
->ip_summed
= CHECKSUM_NONE
;
190 tcph
->check
= tcp_v4_check(tcph
, sizeof(struct tcphdr
),
193 csum_partial((char *)tcph
,
194 sizeof(struct tcphdr
), 0));
196 /* Adjust IP TTL, DF */
197 nskb
->nh
.iph
->ttl
= dst_metric(nskb
->dst
, RTAX_HOPLIMIT
);
199 nskb
->nh
.iph
->frag_off
= htons(IP_DF
);
200 nskb
->nh
.iph
->id
= 0;
202 /* Adjust IP checksum */
203 nskb
->nh
.iph
->check
= 0;
204 nskb
->nh
.iph
->check
= ip_fast_csum((unsigned char *)nskb
->nh
.iph
,
207 /* "Never happens" */
208 if (nskb
->len
> dst_mtu(nskb
->dst
))
211 nf_ct_attach(nskb
, oldskb
);
213 NF_HOOK(PF_INET
, NF_IP_LOCAL_OUT
, nskb
, NULL
, nskb
->dst
->dev
,
221 static inline void send_unreach(struct sk_buff
*skb_in
, int code
)
223 icmp_send(skb_in
, ICMP_DEST_UNREACH
, code
, 0);
226 static unsigned int reject(struct sk_buff
**pskb
,
227 const struct net_device
*in
,
228 const struct net_device
*out
,
229 unsigned int hooknum
,
230 const struct xt_target
*target
,
231 const void *targinfo
)
233 const struct ipt_reject_info
*reject
= targinfo
;
235 /* Our naive response construction doesn't deal with IP
236 options, and probably shouldn't try. */
237 if ((*pskb
)->nh
.iph
->ihl
<<2 != sizeof(struct iphdr
))
240 /* WARNING: This code causes reentry within iptables.
241 This means that the iptables jump stack is now crap. We
242 must return an absolute verdict. --RR */
243 switch (reject
->with
) {
244 case IPT_ICMP_NET_UNREACHABLE
:
245 send_unreach(*pskb
, ICMP_NET_UNREACH
);
247 case IPT_ICMP_HOST_UNREACHABLE
:
248 send_unreach(*pskb
, ICMP_HOST_UNREACH
);
250 case IPT_ICMP_PROT_UNREACHABLE
:
251 send_unreach(*pskb
, ICMP_PROT_UNREACH
);
253 case IPT_ICMP_PORT_UNREACHABLE
:
254 send_unreach(*pskb
, ICMP_PORT_UNREACH
);
256 case IPT_ICMP_NET_PROHIBITED
:
257 send_unreach(*pskb
, ICMP_NET_ANO
);
259 case IPT_ICMP_HOST_PROHIBITED
:
260 send_unreach(*pskb
, ICMP_HOST_ANO
);
262 case IPT_ICMP_ADMIN_PROHIBITED
:
263 send_unreach(*pskb
, ICMP_PKT_FILTERED
);
266 send_reset(*pskb
, hooknum
);
267 case IPT_ICMP_ECHOREPLY
:
268 /* Doesn't happen. */
275 static int check(const char *tablename
,
277 const struct xt_target
*target
,
279 unsigned int hook_mask
)
281 const struct ipt_reject_info
*rejinfo
= targinfo
;
282 const struct ipt_entry
*e
= e_void
;
284 if (rejinfo
->with
== IPT_ICMP_ECHOREPLY
) {
285 printk("REJECT: ECHOREPLY no longer supported.\n");
287 } else if (rejinfo
->with
== IPT_TCP_RESET
) {
288 /* Must specify that it's a TCP packet */
289 if (e
->ip
.proto
!= IPPROTO_TCP
290 || (e
->ip
.invflags
& IPT_INV_PROTO
)) {
291 DEBUGP("REJECT: TCP_RESET invalid for non-tcp\n");
298 static struct ipt_target ipt_reject_reg
= {
301 .targetsize
= sizeof(struct ipt_reject_info
),
303 .hooks
= (1 << NF_IP_LOCAL_IN
) | (1 << NF_IP_FORWARD
) |
304 (1 << NF_IP_LOCAL_OUT
),
309 static int __init
ipt_reject_init(void)
311 return ipt_register_target(&ipt_reject_reg
);
314 static void __exit
ipt_reject_fini(void)
316 ipt_unregister_target(&ipt_reject_reg
);
319 module_init(ipt_reject_init
);
320 module_exit(ipt_reject_fini
);