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>
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 /* If the original packet is part of a connection, but the connection
42 is not confirmed, our manufactured reply will not be associated
43 with it, so we need to do this manually. */
44 static void connection_attach(struct sk_buff
*new_skb
, struct sk_buff
*skb
)
46 void (*attach
)(struct sk_buff
*, struct sk_buff
*);
48 /* Avoid module unload race with ip_ct_attach being NULLed out */
49 if (skb
->nfct
&& (attach
= ip_ct_attach
) != NULL
) {
50 mb(); /* Just to be sure: must be read before executing this */
55 static inline struct rtable
*route_reverse(struct sk_buff
*skb
, int hook
)
57 struct iphdr
*iph
= skb
->nh
.iph
;
58 struct dst_entry
*odst
;
62 /* We don't require ip forwarding to be enabled to be able to
63 * send a RST reply for bridged traffic. */
64 if (hook
!= NF_IP_FORWARD
65 #ifdef CONFIG_BRIDGE_NETFILTER
66 || (skb
->nf_bridge
&& skb
->nf_bridge
->mask
& BRNF_BRIDGED
)
69 fl
.nl_u
.ip4_u
.daddr
= iph
->saddr
;
70 if (hook
== NF_IP_LOCAL_IN
)
71 fl
.nl_u
.ip4_u
.saddr
= iph
->daddr
;
72 fl
.nl_u
.ip4_u
.tos
= RT_TOS(iph
->tos
);
74 if (ip_route_output_key(&rt
, &fl
) != 0)
77 /* non-local src, find valid iif to satisfy
78 * rp-filter when calling ip_route_input. */
79 fl
.nl_u
.ip4_u
.daddr
= iph
->daddr
;
80 if (ip_route_output_key(&rt
, &fl
) != 0)
84 if (ip_route_input(skb
, iph
->saddr
, iph
->daddr
,
85 RT_TOS(iph
->tos
), rt
->u
.dst
.dev
) != 0) {
86 dst_release(&rt
->u
.dst
);
89 dst_release(&rt
->u
.dst
);
90 rt
= (struct rtable
*)skb
->dst
;
94 if (rt
->u
.dst
.error
) {
95 dst_release(&rt
->u
.dst
);
103 static void send_reset(struct sk_buff
*oldskb
, int hook
)
105 struct sk_buff
*nskb
;
106 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. */
126 /* FIXME: Check checksum --RR */
127 if ((rt
= route_reverse(oldskb
, hook
)) == NULL
)
130 hh_len
= LL_RESERVED_SPACE(rt
->u
.dst
.dev
);
132 /* We need a linear, writeable skb. We also need to expand
133 headroom in case hh_len of incoming interface < hh_len of
134 outgoing interface */
135 nskb
= skb_copy_expand(oldskb
, hh_len
, skb_tailroom(oldskb
),
138 dst_release(&rt
->u
.dst
);
142 dst_release(nskb
->dst
);
143 nskb
->dst
= &rt
->u
.dst
;
145 /* This packet will not be the same as the other: clear nf fields */
149 #ifdef CONFIG_BRIDGE_NETFILTER
150 nf_bridge_put(nskb
->nf_bridge
);
151 nskb
->nf_bridge
= NULL
;
154 tcph
= (struct tcphdr
*)((u_int32_t
*)nskb
->nh
.iph
+ nskb
->nh
.iph
->ihl
);
156 /* Swap source and dest */
157 tmp_addr
= nskb
->nh
.iph
->saddr
;
158 nskb
->nh
.iph
->saddr
= nskb
->nh
.iph
->daddr
;
159 nskb
->nh
.iph
->daddr
= tmp_addr
;
160 tmp_port
= tcph
->source
;
161 tcph
->source
= tcph
->dest
;
162 tcph
->dest
= tmp_port
;
164 /* Truncate to length (no data) */
165 tcph
->doff
= sizeof(struct tcphdr
)/4;
166 skb_trim(nskb
, nskb
->nh
.iph
->ihl
*4 + sizeof(struct tcphdr
));
167 nskb
->nh
.iph
->tot_len
= htons(nskb
->len
);
171 tcph
->seq
= oth
->ack_seq
;
175 tcph
->ack_seq
= htonl(ntohl(oth
->seq
) + oth
->syn
+ oth
->fin
176 + oldskb
->len
- oldskb
->nh
.iph
->ihl
*4
182 ((u_int8_t
*)tcph
)[13] = 0;
184 tcph
->ack
= needs_ack
;
189 /* Adjust TCP checksum */
191 tcph
->check
= tcp_v4_check(tcph
, sizeof(struct tcphdr
),
194 csum_partial((char *)tcph
,
195 sizeof(struct tcphdr
), 0));
197 /* Adjust IP TTL, DF */
198 nskb
->nh
.iph
->ttl
= MAXTTL
;
200 nskb
->nh
.iph
->frag_off
= htons(IP_DF
);
201 nskb
->nh
.iph
->id
= 0;
203 /* Adjust IP checksum */
204 nskb
->nh
.iph
->check
= 0;
205 nskb
->nh
.iph
->check
= ip_fast_csum((unsigned char *)nskb
->nh
.iph
,
208 /* "Never happens" */
209 if (nskb
->len
> dst_pmtu(nskb
->dst
))
212 connection_attach(nskb
, oldskb
);
214 NF_HOOK(PF_INET
, NF_IP_LOCAL_OUT
, nskb
, NULL
, nskb
->dst
->dev
,
222 static void send_unreach(struct sk_buff
*skb_in
, int code
)
226 struct icmphdr
*icmph
;
227 struct sk_buff
*nskb
;
231 struct rtable
*rt
= (struct rtable
*)skb_in
->dst
;
237 /* FIXME: Use sysctl number. --RR */
238 if (!xrlim_allow(&rt
->u
.dst
, 1*HZ
))
241 iph
= skb_in
->nh
.iph
;
243 /* No replies to physical multicast/broadcast */
244 if (skb_in
->pkt_type
!=PACKET_HOST
)
247 /* Now check at the protocol level */
248 if (rt
->rt_flags
&(RTCF_BROADCAST
|RTCF_MULTICAST
))
251 /* Only reply to fragment 0. */
252 if (iph
->frag_off
&htons(IP_OFFSET
))
255 /* Ensure we have at least 8 bytes of proto header. */
256 if (skb_in
->len
< skb_in
->nh
.iph
->ihl
*4 + 8)
259 /* if UDP checksum is set, verify it's correct */
260 if (iph
->protocol
== IPPROTO_UDP
261 && skb_in
->tail
-(u8
*)iph
>= sizeof(struct udphdr
)) {
262 int datalen
= skb_in
->len
- (iph
->ihl
<<2);
263 udph
= (struct udphdr
*)((char *)iph
+ (iph
->ihl
<<2));
265 && csum_tcpudp_magic(iph
->saddr
, iph
->daddr
,
266 datalen
, IPPROTO_UDP
,
267 csum_partial((char *)udph
, datalen
,
272 /* If we send an ICMP error to an ICMP error a mess would result.. */
273 if (iph
->protocol
== IPPROTO_ICMP
274 && skb_in
->tail
-(u8
*)iph
>= sizeof(struct icmphdr
)) {
275 icmph
= (struct icmphdr
*)((char *)iph
+ (iph
->ihl
<<2));
277 if (skb_copy_bits(skb_in
, skb_in
->nh
.iph
->ihl
*4,
278 icmph
, sizeof(*icmph
)) < 0)
281 /* Between echo-reply (0) and timestamp (13),
282 everything except echo-request (8) is an error.
283 Also, anything greater than NR_ICMP_TYPES is
284 unknown, and hence should be treated as an error... */
285 if ((icmph
->type
< ICMP_TIMESTAMP
286 && icmph
->type
!= ICMP_ECHOREPLY
287 && icmph
->type
!= ICMP_ECHO
)
288 || icmph
->type
> NR_ICMP_TYPES
)
293 if (!(rt
->rt_flags
& RTCF_LOCAL
))
296 tos
= (iph
->tos
& IPTOS_TOS_MASK
) | IPTOS_PREC_INTERNETCONTROL
;
299 struct flowi fl
= { .nl_u
= { .ip4_u
=
300 { .daddr
= skb_in
->nh
.iph
->saddr
,
302 .tos
= RT_TOS(tos
) } } };
303 if (ip_route_output_key(&rt
, &fl
))
306 /* RFC says return as much as we can without exceeding 576 bytes. */
307 length
= skb_in
->len
+ sizeof(struct iphdr
) + sizeof(struct icmphdr
);
309 if (length
> dst_pmtu(&rt
->u
.dst
))
310 length
= dst_pmtu(&rt
->u
.dst
);
314 hh_len
= LL_RESERVED_SPACE(rt
->u
.dst
.dev
);
316 nskb
= alloc_skb(hh_len
+ length
, GFP_ATOMIC
);
323 nskb
->dst
= &rt
->u
.dst
;
324 skb_reserve(nskb
, hh_len
);
326 /* Set up IP header */
328 = (struct iphdr
*)skb_put(nskb
, sizeof(struct iphdr
));
332 iph
->tot_len
= htons(length
);
334 /* PMTU discovery never applies to ICMP packets. */
338 ip_select_ident(iph
, &rt
->u
.dst
, NULL
);
339 iph
->protocol
=IPPROTO_ICMP
;
340 iph
->saddr
=rt
->rt_src
;
341 iph
->daddr
=rt
->rt_dst
;
343 iph
->check
= ip_fast_csum((unsigned char *)iph
, iph
->ihl
);
345 /* Set up ICMP header. */
346 icmph
= nskb
->h
.icmph
347 = (struct icmphdr
*)skb_put(nskb
, sizeof(struct icmphdr
));
348 icmph
->type
= ICMP_DEST_UNREACH
;
350 icmph
->un
.gateway
= 0;
353 /* Copy as much of original packet as will fit */
355 length
- sizeof(struct iphdr
) - sizeof(struct icmphdr
));
357 skb_copy_bits(skb_in
, 0, data
,
358 length
- sizeof(struct iphdr
) - sizeof(struct icmphdr
));
360 icmph
->checksum
= ip_compute_csum((unsigned char *)icmph
,
361 length
- sizeof(struct iphdr
));
363 connection_attach(nskb
, skb_in
);
365 NF_HOOK(PF_INET
, NF_IP_LOCAL_OUT
, nskb
, NULL
, nskb
->dst
->dev
,
369 static unsigned int reject(struct sk_buff
**pskb
,
370 const struct net_device
*in
,
371 const struct net_device
*out
,
372 unsigned int hooknum
,
373 const void *targinfo
,
376 const struct ipt_reject_info
*reject
= targinfo
;
378 /* Our naive response construction doesn't deal with IP
379 options, and probably shouldn't try. */
380 if ((*pskb
)->nh
.iph
->ihl
<<2 != sizeof(struct iphdr
))
383 /* WARNING: This code causes reentry within iptables.
384 This means that the iptables jump stack is now crap. We
385 must return an absolute verdict. --RR */
386 switch (reject
->with
) {
387 case IPT_ICMP_NET_UNREACHABLE
:
388 send_unreach(*pskb
, ICMP_NET_UNREACH
);
390 case IPT_ICMP_HOST_UNREACHABLE
:
391 send_unreach(*pskb
, ICMP_HOST_UNREACH
);
393 case IPT_ICMP_PROT_UNREACHABLE
:
394 send_unreach(*pskb
, ICMP_PROT_UNREACH
);
396 case IPT_ICMP_PORT_UNREACHABLE
:
397 send_unreach(*pskb
, ICMP_PORT_UNREACH
);
399 case IPT_ICMP_NET_PROHIBITED
:
400 send_unreach(*pskb
, ICMP_NET_ANO
);
402 case IPT_ICMP_HOST_PROHIBITED
:
403 send_unreach(*pskb
, ICMP_HOST_ANO
);
405 case IPT_ICMP_ADMIN_PROHIBITED
:
406 send_unreach(*pskb
, ICMP_PKT_FILTERED
);
409 send_reset(*pskb
, hooknum
);
410 case IPT_ICMP_ECHOREPLY
:
411 /* Doesn't happen. */
418 static int check(const char *tablename
,
419 const struct ipt_entry
*e
,
421 unsigned int targinfosize
,
422 unsigned int hook_mask
)
424 const struct ipt_reject_info
*rejinfo
= targinfo
;
426 if (targinfosize
!= IPT_ALIGN(sizeof(struct ipt_reject_info
))) {
427 DEBUGP("REJECT: targinfosize %u != 0\n", targinfosize
);
431 /* Only allow these for packet filtering. */
432 if (strcmp(tablename
, "filter") != 0) {
433 DEBUGP("REJECT: bad table `%s'.\n", tablename
);
436 if ((hook_mask
& ~((1 << NF_IP_LOCAL_IN
)
437 | (1 << NF_IP_FORWARD
)
438 | (1 << NF_IP_LOCAL_OUT
))) != 0) {
439 DEBUGP("REJECT: bad hook mask %X\n", hook_mask
);
443 if (rejinfo
->with
== IPT_ICMP_ECHOREPLY
) {
444 printk("REJECT: ECHOREPLY no longer supported.\n");
446 } else if (rejinfo
->with
== IPT_TCP_RESET
) {
447 /* Must specify that it's a TCP packet */
448 if (e
->ip
.proto
!= IPPROTO_TCP
449 || (e
->ip
.invflags
& IPT_INV_PROTO
)) {
450 DEBUGP("REJECT: TCP_RESET invalid for non-tcp\n");
458 static struct ipt_target ipt_reject_reg
= {
465 static int __init
init(void)
467 return ipt_register_target(&ipt_reject_reg
);
470 static void __exit
fini(void)
472 ipt_unregister_target(&ipt_reject_reg
);