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 nf_ct_info *nfct)
46 void (*attach)(struct sk_buff *, struct nf_ct_info *);
48 /* Avoid module unload race with ip_ct_attach being NULLed out */
49 if (nfct && (attach = ip_ct_attach) != NULL) {
50 mb(); /* Just to be sure: must be read before executing this */
51 attach(new_skb, nfct);
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, *tcph;
113 /* IP header checks: fragment. */
114 if (oldskb->nh.iph->frag_off & htons(IP_OFFSET))
117 if (skb_copy_bits(oldskb, oldskb->nh.iph->ihl*4,
118 &otcph, sizeof(otcph)) < 0)
121 /* No RST for RST. */
125 /* FIXME: Check checksum --RR */
126 if ((rt = route_reverse(oldskb, hook)) == NULL)
129 hh_len = LL_RESERVED_SPACE(rt->u.dst.dev);
131 /* We need a linear, writeable skb. We also need to expand
132 headroom in case hh_len of incoming interface < hh_len of
133 outgoing interface */
134 nskb = skb_copy_expand(oldskb, hh_len, skb_tailroom(oldskb),
137 dst_release(&rt->u.dst);
141 dst_release(nskb->dst);
142 nskb->dst = &rt->u.dst;
144 /* This packet will not be the same as the other: clear nf fields */
145 nf_conntrack_put(nskb->nfct);
148 #ifdef CONFIG_NETFILTER_DEBUG
152 #ifdef CONFIG_BRIDGE_NETFILTER
153 nf_bridge_put(nskb->nf_bridge);
154 nskb->nf_bridge = NULL;
157 tcph = (struct tcphdr *)((u_int32_t*)nskb->nh.iph + nskb->nh.iph->ihl);
159 /* Swap source and dest */
160 tmp_addr = nskb->nh.iph->saddr;
161 nskb->nh.iph->saddr = nskb->nh.iph->daddr;
162 nskb->nh.iph->daddr = tmp_addr;
163 tmp_port = tcph->source;
164 tcph->source = tcph->dest;
165 tcph->dest = tmp_port;
167 /* Truncate to length (no data) */
168 tcph->doff = sizeof(struct tcphdr)/4;
169 skb_trim(nskb, nskb->nh.iph->ihl*4 + sizeof(struct tcphdr));
170 nskb->nh.iph->tot_len = htons(nskb->len);
174 tcph->seq = otcph.ack_seq;
178 tcph->ack_seq = htonl(ntohl(otcph.seq) + otcph.syn + otcph.fin
179 + oldskb->len - oldskb->nh.iph->ihl*4
185 ((u_int8_t *)tcph)[13] = 0;
187 tcph->ack = needs_ack;
192 /* Adjust TCP checksum */
194 tcph->check = tcp_v4_check(tcph, sizeof(struct tcphdr),
197 csum_partial((char *)tcph,
198 sizeof(struct tcphdr), 0));
200 /* Adjust IP TTL, DF */
201 nskb->nh.iph->ttl = MAXTTL;
203 nskb->nh.iph->frag_off = htons(IP_DF);
204 nskb->nh.iph->id = 0;
206 /* Adjust IP checksum */
207 nskb->nh.iph->check = 0;
208 nskb->nh.iph->check = ip_fast_csum((unsigned char *)nskb->nh.iph,
211 /* "Never happens" */
212 if (nskb->len > dst_pmtu(nskb->dst))
215 connection_attach(nskb, oldskb->nfct);
217 NF_HOOK(PF_INET, NF_IP_LOCAL_OUT, nskb, NULL, nskb->dst->dev,
225 static void send_unreach(struct sk_buff *skb_in, int code)
229 struct icmphdr *icmph;
230 struct sk_buff *nskb;
234 struct rtable *rt = (struct rtable*)skb_in->dst;
240 /* FIXME: Use sysctl number. --RR */
241 if (!xrlim_allow(&rt->u.dst, 1*HZ))
244 iph = skb_in->nh.iph;
246 /* No replies to physical multicast/broadcast */
247 if (skb_in->pkt_type!=PACKET_HOST)
250 /* Now check at the protocol level */
251 if (rt->rt_flags&(RTCF_BROADCAST|RTCF_MULTICAST))
254 /* Only reply to fragment 0. */
255 if (iph->frag_off&htons(IP_OFFSET))
258 /* Ensure we have at least 8 bytes of proto header. */
259 if (skb_in->len < skb_in->nh.iph->ihl*4 + 8)
262 /* if UDP checksum is set, verify it's correct */
263 if (iph->protocol == IPPROTO_UDP
264 && skb_in->tail-(u8*)iph >= sizeof(struct udphdr)) {
265 int datalen = skb_in->len - (iph->ihl<<2);
266 udph = (struct udphdr *)((char *)iph + (iph->ihl<<2));
268 && csum_tcpudp_magic(iph->saddr, iph->daddr,
269 datalen, IPPROTO_UDP,
270 csum_partial((char *)udph, datalen,
275 /* If we send an ICMP error to an ICMP error a mess would result.. */
276 if (iph->protocol == IPPROTO_ICMP
277 && skb_in->tail-(u8*)iph >= sizeof(struct icmphdr)) {
278 icmph = (struct icmphdr *)((char *)iph + (iph->ihl<<2));
280 if (skb_copy_bits(skb_in, skb_in->nh.iph->ihl*4,
281 icmph, sizeof(*icmph)) < 0)
284 /* Between echo-reply (0) and timestamp (13),
285 everything except echo-request (8) is an error.
286 Also, anything greater than NR_ICMP_TYPES is
287 unknown, and hence should be treated as an error... */
288 if ((icmph->type < ICMP_TIMESTAMP
289 && icmph->type != ICMP_ECHOREPLY
290 && icmph->type != ICMP_ECHO)
291 || icmph->type > NR_ICMP_TYPES)
296 if (!(rt->rt_flags & RTCF_LOCAL))
299 tos = (iph->tos & IPTOS_TOS_MASK) | IPTOS_PREC_INTERNETCONTROL;
302 struct flowi fl = { .nl_u = { .ip4_u =
303 { .daddr = skb_in->nh.iph->saddr,
305 .tos = RT_TOS(tos) } } };
306 if (ip_route_output_key(&rt, &fl))
309 /* RFC says return as much as we can without exceeding 576 bytes. */
310 length = skb_in->len + sizeof(struct iphdr) + sizeof(struct icmphdr);
312 if (length > dst_pmtu(&rt->u.dst))
313 length = dst_pmtu(&rt->u.dst);
317 hh_len = LL_RESERVED_SPACE(rt->u.dst.dev);
319 nskb = alloc_skb(hh_len + length, GFP_ATOMIC);
326 nskb->dst = &rt->u.dst;
327 skb_reserve(nskb, hh_len);
329 /* Set up IP header */
331 = (struct iphdr *)skb_put(nskb, sizeof(struct iphdr));
335 iph->tot_len = htons(length);
337 /* PMTU discovery never applies to ICMP packets. */
341 ip_select_ident(iph, &rt->u.dst, NULL);
342 iph->protocol=IPPROTO_ICMP;
343 iph->saddr=rt->rt_src;
344 iph->daddr=rt->rt_dst;
346 iph->check = ip_fast_csum((unsigned char *)iph, iph->ihl);
348 /* Set up ICMP header. */
349 icmph = nskb->h.icmph
350 = (struct icmphdr *)skb_put(nskb, sizeof(struct icmphdr));
351 icmph->type = ICMP_DEST_UNREACH;
353 icmph->un.gateway = 0;
356 /* Copy as much of original packet as will fit */
358 length - sizeof(struct iphdr) - sizeof(struct icmphdr));
360 skb_copy_bits(skb_in, 0, data,
361 length - sizeof(struct iphdr) - sizeof(struct icmphdr));
363 icmph->checksum = ip_compute_csum((unsigned char *)icmph,
364 length - sizeof(struct iphdr));
366 connection_attach(nskb, skb_in->nfct);
368 NF_HOOK(PF_INET, NF_IP_LOCAL_OUT, nskb, NULL, nskb->dst->dev,
372 static unsigned int reject(struct sk_buff **pskb,
373 const struct net_device *in,
374 const struct net_device *out,
375 unsigned int hooknum,
376 const void *targinfo,
379 const struct ipt_reject_info *reject = targinfo;
381 /* Our naive response construction doesn't deal with IP
382 options, and probably shouldn't try. */
383 if ((*pskb)->nh.iph->ihl<<2 != sizeof(struct iphdr))
386 /* WARNING: This code causes reentry within iptables.
387 This means that the iptables jump stack is now crap. We
388 must return an absolute verdict. --RR */
389 switch (reject->with) {
390 case IPT_ICMP_NET_UNREACHABLE:
391 send_unreach(*pskb, ICMP_NET_UNREACH);
393 case IPT_ICMP_HOST_UNREACHABLE:
394 send_unreach(*pskb, ICMP_HOST_UNREACH);
396 case IPT_ICMP_PROT_UNREACHABLE:
397 send_unreach(*pskb, ICMP_PROT_UNREACH);
399 case IPT_ICMP_PORT_UNREACHABLE:
400 send_unreach(*pskb, ICMP_PORT_UNREACH);
402 case IPT_ICMP_NET_PROHIBITED:
403 send_unreach(*pskb, ICMP_NET_ANO);
405 case IPT_ICMP_HOST_PROHIBITED:
406 send_unreach(*pskb, ICMP_HOST_ANO);
408 case IPT_ICMP_ADMIN_PROHIBITED:
409 send_unreach(*pskb, ICMP_PKT_FILTERED);
412 send_reset(*pskb, hooknum);
413 case IPT_ICMP_ECHOREPLY:
414 /* Doesn't happen. */
421 static int check(const char *tablename,
422 const struct ipt_entry *e,
424 unsigned int targinfosize,
425 unsigned int hook_mask)
427 const struct ipt_reject_info *rejinfo = targinfo;
429 if (targinfosize != IPT_ALIGN(sizeof(struct ipt_reject_info))) {
430 DEBUGP("REJECT: targinfosize %u != 0\n", targinfosize);
434 /* Only allow these for packet filtering. */
435 if (strcmp(tablename, "filter") != 0) {
436 DEBUGP("REJECT: bad table `%s'.\n", tablename);
439 if ((hook_mask & ~((1 << NF_IP_LOCAL_IN)
440 | (1 << NF_IP_FORWARD)
441 | (1 << NF_IP_LOCAL_OUT))) != 0) {
442 DEBUGP("REJECT: bad hook mask %X\n", hook_mask);
446 if (rejinfo->with == IPT_ICMP_ECHOREPLY) {
447 printk("REJECT: ECHOREPLY no longer supported.\n");
449 } else if (rejinfo->with == IPT_TCP_RESET) {
450 /* Must specify that it's a TCP packet */
451 if (e->ip.proto != IPPROTO_TCP
452 || (e->ip.invflags & IPT_INV_PROTO)) {
453 DEBUGP("REJECT: TCP_RESET invalid for non-tcp\n");
461 static struct ipt_target ipt_reject_reg = {
468 static int __init init(void)
470 return ipt_register_target(&ipt_reject_reg);
473 static void __exit fini(void)
475 ipt_unregister_target(&ipt_reject_reg);