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 */
158 tcph
= (struct tcphdr
*)((u_int32_t
*)nskb
->nh
.iph
+ nskb
->nh
.iph
->ihl
);
160 /* Swap source and dest */
161 tmp_addr
= nskb
->nh
.iph
->saddr
;
162 nskb
->nh
.iph
->saddr
= nskb
->nh
.iph
->daddr
;
163 nskb
->nh
.iph
->daddr
= tmp_addr
;
164 tmp_port
= tcph
->source
;
165 tcph
->source
= tcph
->dest
;
166 tcph
->dest
= tmp_port
;
168 /* Truncate to length (no data) */
169 tcph
->doff
= sizeof(struct tcphdr
)/4;
170 skb_trim(nskb
, nskb
->nh
.iph
->ihl
*4 + sizeof(struct tcphdr
));
171 nskb
->nh
.iph
->tot_len
= htons(nskb
->len
);
175 tcph
->seq
= oth
->ack_seq
;
179 tcph
->ack_seq
= htonl(ntohl(oth
->seq
) + oth
->syn
+ oth
->fin
180 + oldskb
->len
- oldskb
->nh
.iph
->ihl
*4
186 ((u_int8_t
*)tcph
)[13] = 0;
188 tcph
->ack
= needs_ack
;
193 /* Adjust TCP checksum */
195 tcph
->check
= tcp_v4_check(tcph
, sizeof(struct tcphdr
),
198 csum_partial((char *)tcph
,
199 sizeof(struct tcphdr
), 0));
201 /* Adjust IP TTL, DF */
202 nskb
->nh
.iph
->ttl
= dst_metric(nskb
->dst
, RTAX_HOPLIMIT
);
204 nskb
->nh
.iph
->frag_off
= htons(IP_DF
);
205 nskb
->nh
.iph
->id
= 0;
207 /* Adjust IP checksum */
208 nskb
->nh
.iph
->check
= 0;
209 nskb
->nh
.iph
->check
= ip_fast_csum((unsigned char *)nskb
->nh
.iph
,
212 /* "Never happens" */
213 if (nskb
->len
> dst_mtu(nskb
->dst
))
216 nf_ct_attach(nskb
, oldskb
);
218 NF_HOOK(PF_INET
, NF_IP_LOCAL_OUT
, nskb
, NULL
, nskb
->dst
->dev
,
226 static inline void send_unreach(struct sk_buff
*skb_in
, int code
)
228 icmp_send(skb_in
, ICMP_DEST_UNREACH
, code
, 0);
231 static unsigned int reject(struct sk_buff
**pskb
,
232 const struct net_device
*in
,
233 const struct net_device
*out
,
234 unsigned int hooknum
,
235 const struct xt_target
*target
,
236 const void *targinfo
,
239 const struct ipt_reject_info
*reject
= targinfo
;
241 /* Our naive response construction doesn't deal with IP
242 options, and probably shouldn't try. */
243 if ((*pskb
)->nh
.iph
->ihl
<<2 != sizeof(struct iphdr
))
246 /* WARNING: This code causes reentry within iptables.
247 This means that the iptables jump stack is now crap. We
248 must return an absolute verdict. --RR */
249 switch (reject
->with
) {
250 case IPT_ICMP_NET_UNREACHABLE
:
251 send_unreach(*pskb
, ICMP_NET_UNREACH
);
253 case IPT_ICMP_HOST_UNREACHABLE
:
254 send_unreach(*pskb
, ICMP_HOST_UNREACH
);
256 case IPT_ICMP_PROT_UNREACHABLE
:
257 send_unreach(*pskb
, ICMP_PROT_UNREACH
);
259 case IPT_ICMP_PORT_UNREACHABLE
:
260 send_unreach(*pskb
, ICMP_PORT_UNREACH
);
262 case IPT_ICMP_NET_PROHIBITED
:
263 send_unreach(*pskb
, ICMP_NET_ANO
);
265 case IPT_ICMP_HOST_PROHIBITED
:
266 send_unreach(*pskb
, ICMP_HOST_ANO
);
268 case IPT_ICMP_ADMIN_PROHIBITED
:
269 send_unreach(*pskb
, ICMP_PKT_FILTERED
);
272 send_reset(*pskb
, hooknum
);
273 case IPT_ICMP_ECHOREPLY
:
274 /* Doesn't happen. */
281 static int check(const char *tablename
,
283 const struct xt_target
*target
,
285 unsigned int targinfosize
,
286 unsigned int hook_mask
)
288 const struct ipt_reject_info
*rejinfo
= targinfo
;
289 const struct ipt_entry
*e
= e_void
;
291 if (rejinfo
->with
== IPT_ICMP_ECHOREPLY
) {
292 printk("REJECT: ECHOREPLY no longer supported.\n");
294 } else if (rejinfo
->with
== IPT_TCP_RESET
) {
295 /* Must specify that it's a TCP packet */
296 if (e
->ip
.proto
!= IPPROTO_TCP
297 || (e
->ip
.invflags
& IPT_INV_PROTO
)) {
298 DEBUGP("REJECT: TCP_RESET invalid for non-tcp\n");
305 static struct ipt_target ipt_reject_reg
= {
308 .targetsize
= sizeof(struct ipt_reject_info
),
310 .hooks
= (1 << NF_IP_LOCAL_IN
) | (1 << NF_IP_FORWARD
) |
311 (1 << NF_IP_LOCAL_OUT
),
316 static int __init
ipt_reject_init(void)
318 return ipt_register_target(&ipt_reject_reg
);
321 static void __exit
ipt_reject_fini(void)
323 ipt_unregister_target(&ipt_reject_reg
);
326 module_init(ipt_reject_init
);
327 module_exit(ipt_reject_fini
);