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
)
47 struct tcphdr _otcph
, *oth
, *tcph
;
51 unsigned int addr_type
;
53 /* IP header checks: fragment. */
54 if (ip_hdr(oldskb
)->frag_off
& htons(IP_OFFSET
))
57 oth
= skb_header_pointer(oldskb
, ip_hdrlen(oldskb
),
58 sizeof(_otcph
), &_otcph
);
67 if (nf_ip_checksum(oldskb
, hook
, ip_hdrlen(oldskb
), 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 skb_shinfo(nskb
)->gso_size
= 0;
84 skb_shinfo(nskb
)->gso_segs
= 0;
85 skb_shinfo(nskb
)->gso_type
= 0;
87 tcph
= (struct tcphdr
*)(skb_network_header(nskb
) + ip_hdrlen(nskb
));
89 /* Swap source and dest */
91 tmp_addr
= niph
->saddr
;
92 niph
->saddr
= niph
->daddr
;
93 niph
->daddr
= tmp_addr
;
94 tmp_port
= tcph
->source
;
95 tcph
->source
= tcph
->dest
;
96 tcph
->dest
= tmp_port
;
98 /* Truncate to length (no data) */
99 tcph
->doff
= sizeof(struct tcphdr
)/4;
100 skb_trim(nskb
, ip_hdrlen(nskb
) + sizeof(struct tcphdr
));
101 niph
->tot_len
= htons(nskb
->len
);
105 tcph
->seq
= oth
->ack_seq
;
109 tcph
->ack_seq
= htonl(ntohl(oth
->seq
) + oth
->syn
+ oth
->fin
+
110 oldskb
->len
- ip_hdrlen(oldskb
) -
116 ((u_int8_t
*)tcph
)[13] = 0;
118 tcph
->ack
= needs_ack
;
123 /* Adjust TCP checksum */
125 tcph
->check
= tcp_v4_check(sizeof(struct tcphdr
),
126 niph
->saddr
, niph
->daddr
,
127 csum_partial((char *)tcph
,
128 sizeof(struct tcphdr
), 0));
131 niph
->frag_off
= htons(IP_DF
);
134 addr_type
= RTN_UNSPEC
;
135 if (hook
!= NF_IP_FORWARD
136 #ifdef CONFIG_BRIDGE_NETFILTER
137 || (nskb
->nf_bridge
&& nskb
->nf_bridge
->mask
& BRNF_BRIDGED
)
140 addr_type
= RTN_LOCAL
;
142 if (ip_route_me_harder(&nskb
, addr_type
))
145 nskb
->ip_summed
= CHECKSUM_NONE
;
148 niph
->ttl
= dst_metric(nskb
->dst
, RTAX_HOPLIMIT
);
150 /* Adjust IP checksum */
152 niph
->check
= ip_fast_csum(skb_network_header(nskb
), niph
->ihl
);
154 /* "Never happens" */
155 if (nskb
->len
> dst_mtu(nskb
->dst
))
158 nf_ct_attach(nskb
, oldskb
);
160 NF_HOOK(PF_INET
, NF_IP_LOCAL_OUT
, nskb
, NULL
, nskb
->dst
->dev
,
168 static inline void send_unreach(struct sk_buff
*skb_in
, int code
)
170 icmp_send(skb_in
, ICMP_DEST_UNREACH
, code
, 0);
173 static unsigned int reject(struct sk_buff
**pskb
,
174 const struct net_device
*in
,
175 const struct net_device
*out
,
176 unsigned int hooknum
,
177 const struct xt_target
*target
,
178 const void *targinfo
)
180 const struct ipt_reject_info
*reject
= targinfo
;
182 /* Our naive response construction doesn't deal with IP
183 options, and probably shouldn't try. */
184 if (ip_hdrlen(*pskb
) != sizeof(struct iphdr
))
187 /* WARNING: This code causes reentry within iptables.
188 This means that the iptables jump stack is now crap. We
189 must return an absolute verdict. --RR */
190 switch (reject
->with
) {
191 case IPT_ICMP_NET_UNREACHABLE
:
192 send_unreach(*pskb
, ICMP_NET_UNREACH
);
194 case IPT_ICMP_HOST_UNREACHABLE
:
195 send_unreach(*pskb
, ICMP_HOST_UNREACH
);
197 case IPT_ICMP_PROT_UNREACHABLE
:
198 send_unreach(*pskb
, ICMP_PROT_UNREACH
);
200 case IPT_ICMP_PORT_UNREACHABLE
:
201 send_unreach(*pskb
, ICMP_PORT_UNREACH
);
203 case IPT_ICMP_NET_PROHIBITED
:
204 send_unreach(*pskb
, ICMP_NET_ANO
);
206 case IPT_ICMP_HOST_PROHIBITED
:
207 send_unreach(*pskb
, ICMP_HOST_ANO
);
209 case IPT_ICMP_ADMIN_PROHIBITED
:
210 send_unreach(*pskb
, ICMP_PKT_FILTERED
);
213 send_reset(*pskb
, hooknum
);
214 case IPT_ICMP_ECHOREPLY
:
215 /* Doesn't happen. */
222 static int check(const char *tablename
,
224 const struct xt_target
*target
,
226 unsigned int hook_mask
)
228 const struct ipt_reject_info
*rejinfo
= targinfo
;
229 const struct ipt_entry
*e
= e_void
;
231 if (rejinfo
->with
== IPT_ICMP_ECHOREPLY
) {
232 printk("REJECT: ECHOREPLY no longer supported.\n");
234 } else if (rejinfo
->with
== IPT_TCP_RESET
) {
235 /* Must specify that it's a TCP packet */
236 if (e
->ip
.proto
!= IPPROTO_TCP
237 || (e
->ip
.invflags
& XT_INV_PROTO
)) {
238 DEBUGP("REJECT: TCP_RESET invalid for non-tcp\n");
245 static struct xt_target ipt_reject_reg
= {
249 .targetsize
= sizeof(struct ipt_reject_info
),
251 .hooks
= (1 << NF_IP_LOCAL_IN
) | (1 << NF_IP_FORWARD
) |
252 (1 << NF_IP_LOCAL_OUT
),
257 static int __init
ipt_reject_init(void)
259 return xt_register_target(&ipt_reject_reg
);
262 static void __exit
ipt_reject_fini(void)
264 xt_unregister_target(&ipt_reject_reg
);
267 module_init(ipt_reject_init
);
268 module_exit(ipt_reject_fini
);