[net-next-2.6.git] / net / ipv4 / netfilter / ipt_REJECT.c

/*
 * This is a module which is used for rejecting packets.
 * Added support for customized reject packets (Jozsef Kadlecsik).
 * Added support for ICMP type-3-code-13 (Maciej Soltysiak). [RFC 1812]
 */

/* (C) 1999-2001 Paul `Rusty' Russell
 * (C) 2002-2004 Netfilter Core Team <coreteam@netfilter.org>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 */

#include <linux/module.h>
#include <linux/skbuff.h>
#include <linux/ip.h>
#include <linux/udp.h>
#include <linux/icmp.h>
#include <net/icmp.h>
#include <net/ip.h>
#include <net/tcp.h>
#include <net/route.h>
#include <net/dst.h>
#include <linux/netfilter/x_tables.h>
#include <linux/netfilter_ipv4/ip_tables.h>
#include <linux/netfilter_ipv4/ipt_REJECT.h>
#ifdef CONFIG_BRIDGE_NETFILTER
#include <linux/netfilter_bridge.h>
#endif

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Netfilter Core Team <coreteam@netfilter.org>");
MODULE_DESCRIPTION("iptables REJECT target module");

#if 0
#define DEBUGP printk
#else
#define DEBUGP(format, args...)
#endif

/* Send RST reply */
static void send_reset(struct sk_buff *oldskb, int hook)
{
	struct sk_buff *nskb;
	struct iphdr *iph = oldskb->nh.iph;
	struct tcphdr _otcph, *oth, *tcph;
	__be16 tmp_port;
	__be32 tmp_addr;
	int needs_ack;
	unsigned int addr_type;

	/* IP header checks: fragment. */
	if (oldskb->nh.iph->frag_off & htons(IP_OFFSET))
		return;

	oth = skb_header_pointer(oldskb, oldskb->nh.iph->ihl * 4,
				 sizeof(_otcph), &_otcph);
	if (oth == NULL)
		return;

	/* No RST for RST. */
	if (oth->rst)
		return;

	/* Check checksum */
	if (nf_ip_checksum(oldskb, hook, iph->ihl * 4, IPPROTO_TCP))
		return;

	/* We need a linear, writeable skb.  We also need to expand
	   headroom in case hh_len of incoming interface < hh_len of
	   outgoing interface */
	nskb = skb_copy_expand(oldskb, LL_MAX_HEADER, skb_tailroom(oldskb),
			       GFP_ATOMIC);
	if (!nskb)
		return;

	/* This packet will not be the same as the other: clear nf fields */
	nf_reset(nskb);
	nskb->mark = 0;
	skb_init_secmark(nskb);

	tcph = (struct tcphdr *)((u_int32_t*)nskb->nh.iph + nskb->nh.iph->ihl);

	/* Swap source and dest */
	tmp_addr = nskb->nh.iph->saddr;
	nskb->nh.iph->saddr = nskb->nh.iph->daddr;
	nskb->nh.iph->daddr = tmp_addr;
	tmp_port = tcph->source;
	tcph->source = tcph->dest;
	tcph->dest = tmp_port;

	/* Truncate to length (no data) */
	tcph->doff = sizeof(struct tcphdr)/4;
	skb_trim(nskb, nskb->nh.iph->ihl*4 + sizeof(struct tcphdr));
	nskb->nh.iph->tot_len = htons(nskb->len);

	if (tcph->ack) {
		needs_ack = 0;
		tcph->seq = oth->ack_seq;
		tcph->ack_seq = 0;
	} else {
		needs_ack = 1;
		tcph->ack_seq = htonl(ntohl(oth->seq) + oth->syn + oth->fin
				      + oldskb->len - oldskb->nh.iph->ihl*4
				      - (oth->doff<<2));
		tcph->seq = 0;
	}

	/* Reset flags */
	((u_int8_t *)tcph)[13] = 0;
	tcph->rst = 1;
	tcph->ack = needs_ack;

	tcph->window = 0;
	tcph->urg_ptr = 0;

	/* Adjust TCP checksum */
	tcph->check = 0;
	tcph->check = tcp_v4_check(sizeof(struct tcphdr),
				   nskb->nh.iph->saddr,
				   nskb->nh.iph->daddr,
				   csum_partial((char *)tcph,
						sizeof(struct tcphdr), 0));

	/* Set DF, id = 0 */
	nskb->nh.iph->frag_off = htons(IP_DF);
	nskb->nh.iph->id = 0;

	addr_type = RTN_UNSPEC;
	if (hook != NF_IP_FORWARD
#ifdef CONFIG_BRIDGE_NETFILTER
	    || (nskb->nf_bridge && nskb->nf_bridge->mask & BRNF_BRIDGED)
#endif
	   )
		addr_type = RTN_LOCAL;

	if (ip_route_me_harder(&nskb, addr_type))
		goto free_nskb;

	nskb->ip_summed = CHECKSUM_NONE;

	/* Adjust IP TTL */
	nskb->nh.iph->ttl = dst_metric(nskb->dst, RTAX_HOPLIMIT);

	/* Adjust IP checksum */
	nskb->nh.iph->check = 0;
	nskb->nh.iph->check = ip_fast_csum((unsigned char *)nskb->nh.iph,
					   nskb->nh.iph->ihl);

	/* "Never happens" */
	if (nskb->len > dst_mtu(nskb->dst))
		goto free_nskb;

	nf_ct_attach(nskb, oldskb);

	NF_HOOK(PF_INET, NF_IP_LOCAL_OUT, nskb, NULL, nskb->dst->dev,
		dst_output);
	return;

 free_nskb:
	kfree_skb(nskb);
}

static inline void send_unreach(struct sk_buff *skb_in, int code)
{
	icmp_send(skb_in, ICMP_DEST_UNREACH, code, 0);
}

static unsigned int reject(struct sk_buff **pskb,
			   const struct net_device *in,
			   const struct net_device *out,
			   unsigned int hooknum,
			   const struct xt_target *target,
			   const void *targinfo)
{
	const struct ipt_reject_info *reject = targinfo;

	/* Our naive response construction doesn't deal with IP
	   options, and probably shouldn't try. */
	if ((*pskb)->nh.iph->ihl<<2 != sizeof(struct iphdr))
		return NF_DROP;

	/* WARNING: This code causes reentry within iptables.
	   This means that the iptables jump stack is now crap.  We
	   must return an absolute verdict. --RR */
	switch (reject->with) {
	case IPT_ICMP_NET_UNREACHABLE:
		send_unreach(*pskb, ICMP_NET_UNREACH);
		break;
	case IPT_ICMP_HOST_UNREACHABLE:
		send_unreach(*pskb, ICMP_HOST_UNREACH);
		break;
	case IPT_ICMP_PROT_UNREACHABLE:
		send_unreach(*pskb, ICMP_PROT_UNREACH);
		break;
	case IPT_ICMP_PORT_UNREACHABLE:
		send_unreach(*pskb, ICMP_PORT_UNREACH);
		break;
	case IPT_ICMP_NET_PROHIBITED:
		send_unreach(*pskb, ICMP_NET_ANO);
		break;
	case IPT_ICMP_HOST_PROHIBITED:
		send_unreach(*pskb, ICMP_HOST_ANO);
		break;
	case IPT_ICMP_ADMIN_PROHIBITED:
		send_unreach(*pskb, ICMP_PKT_FILTERED);
		break;
	case IPT_TCP_RESET:
		send_reset(*pskb, hooknum);
	case IPT_ICMP_ECHOREPLY:
		/* Doesn't happen. */
		break;
	}

	return NF_DROP;
}

static int check(const char *tablename,
		 const void *e_void,
		 const struct xt_target *target,
		 void *targinfo,
		 unsigned int hook_mask)
{
	const struct ipt_reject_info *rejinfo = targinfo;
	const struct ipt_entry *e = e_void;

	if (rejinfo->with == IPT_ICMP_ECHOREPLY) {
		printk("REJECT: ECHOREPLY no longer supported.\n");
		return 0;
	} else if (rejinfo->with == IPT_TCP_RESET) {
		/* Must specify that it's a TCP packet */
		if (e->ip.proto != IPPROTO_TCP
		    || (e->ip.invflags & XT_INV_PROTO)) {
			DEBUGP("REJECT: TCP_RESET invalid for non-tcp\n");
			return 0;
		}
	}
	return 1;
}

static struct xt_target ipt_reject_reg = {
	.name		= "REJECT",
	.family		= AF_INET,
	.target		= reject,
	.targetsize	= sizeof(struct ipt_reject_info),
	.table		= "filter",
	.hooks		= (1 << NF_IP_LOCAL_IN) | (1 << NF_IP_FORWARD) |
			  (1 << NF_IP_LOCAL_OUT),
	.checkentry	= check,
	.me		= THIS_MODULE,
};

static int __init ipt_reject_init(void)
{
	return xt_register_target(&ipt_reject_reg);
}

static void __exit ipt_reject_fini(void)
{
	xt_unregister_target(&ipt_reject_reg);
}

module_init(ipt_reject_init);
module_exit(ipt_reject_fini);
Commit	Line	Data
1da177e4 LT	1	/*
	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]
	5	*/
	6
	7	/* (C) 1999-2001 Paul `Rusty' Russell
	8	* (C) 2002-2004 Netfilter Core Team <coreteam@netfilter.org>
	9	*
	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.
	13	*/
	14
1da177e4 LT	15	#include <linux/module.h>
	16	#include <linux/skbuff.h>
	17	#include <linux/ip.h>
	18	#include <linux/udp.h>
	19	#include <linux/icmp.h>
	20	#include <net/icmp.h>
	21	#include <net/ip.h>
	22	#include <net/tcp.h>
	23	#include <net/route.h>
	24	#include <net/dst.h>
6709dbbb	25	#include <linux/netfilter/x_tables.h>
1da177e4 LT	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>
	30	#endif
	31
	32	MODULE_LICENSE("GPL");
	33	MODULE_AUTHOR("Netfilter Core Team <coreteam@netfilter.org>");
	34	MODULE_DESCRIPTION("iptables REJECT target module");
	35
	36	#if 0
	37	#define DEBUGP printk
	38	#else
	39	#define DEBUGP(format, args...)
	40	#endif
	41
1da177e4 LT	42	/* Send RST reply */
	43	static void send_reset(struct sk_buff *oldskb, int hook)
	44	{
	45	struct sk_buff *nskb;
6150bacf	46	struct iphdr *iph = oldskb->nh.iph;
1da177e4	47	struct tcphdr _otcph, oth, tcph;
6a19d614 AV	48	__be16 tmp_port;
6a19d614 AV	49	__be32 tmp_addr;
1da177e4	50	int needs_ack;
9d02002d	51	unsigned int addr_type;
1da177e4 LT	52
	53	/* IP header checks: fragment. */
	54	if (oldskb->nh.iph->frag_off & htons(IP_OFFSET))
	55	return;
	56
	57	oth = skb_header_pointer(oldskb, oldskb->nh.iph->ihl * 4,
	58	sizeof(_otcph), &_otcph);
	59	if (oth == NULL)
e905a9ed	60	return;
1da177e4 LT	61
	62	/* No RST for RST. */
	63	if (oth->rst)
	64	return;
	65
6150bacf	66	/* Check checksum */
96f6bf82	67	if (nf_ip_checksum(oldskb, hook, iph->ihl * 4, IPPROTO_TCP))
6150bacf PM	68	return;
6150bacf PM	69
1da177e4 LT	70	/* We need a linear, writeable skb. We also need to expand
	71	headroom in case hh_len of incoming interface < hh_len of
	72	outgoing interface */
9d02002d	73	nskb = skb_copy_expand(oldskb, LL_MAX_HEADER, skb_tailroom(oldskb),
1da177e4	74	GFP_ATOMIC);
9d02002d	75	if (!nskb)
1da177e4	76	return;
1da177e4 LT	77
	78	/* This packet will not be the same as the other: clear nf fields */
	79	nf_reset(nskb);
82e91ffe	80	nskb->mark = 0;
984bc16c	81	skb_init_secmark(nskb);
1da177e4 LT	82
	83	tcph = (struct tcphdr )((u_int32_t)nskb->nh.iph + nskb->nh.iph->ihl);
	84
	85	/* Swap source and dest */
	86	tmp_addr = nskb->nh.iph->saddr;
	87	nskb->nh.iph->saddr = nskb->nh.iph->daddr;
	88	nskb->nh.iph->daddr = tmp_addr;
	89	tmp_port = tcph->source;
	90	tcph->source = tcph->dest;
	91	tcph->dest = tmp_port;
	92
	93	/* Truncate to length (no data) */
	94	tcph->doff = sizeof(struct tcphdr)/4;
	95	skb_trim(nskb, nskb->nh.iph->ihl*4 + sizeof(struct tcphdr));
	96	nskb->nh.iph->tot_len = htons(nskb->len);
	97
	98	if (tcph->ack) {
	99	needs_ack = 0;
	100	tcph->seq = oth->ack_seq;
	101	tcph->ack_seq = 0;
	102	} else {
	103	needs_ack = 1;
	104	tcph->ack_seq = htonl(ntohl(oth->seq) + oth->syn + oth->fin
	105	+ oldskb->len - oldskb->nh.iph->ihl*4
	106	- (oth->doff<<2));
	107	tcph->seq = 0;
	108	}
	109
	110	/* Reset flags */
	111	((u_int8_t *)tcph)[13] = 0;
	112	tcph->rst = 1;
	113	tcph->ack = needs_ack;
	114
	115	tcph->window = 0;
	116	tcph->urg_ptr = 0;
	117
af443b6d PM	118	/* Adjust TCP checksum */
af443b6d PM	119	tcph->check = 0;
ba7808ea	120	tcph->check = tcp_v4_check(sizeof(struct tcphdr),
af443b6d PM	121	nskb->nh.iph->saddr,
	122	nskb->nh.iph->daddr,
	123	csum_partial((char *)tcph,
	124	sizeof(struct tcphdr), 0));
	125
9d02002d PM	126	/* Set DF, id = 0 */
	127	nskb->nh.iph->frag_off = htons(IP_DF);
	128	nskb->nh.iph->id = 0;
	129
	130	addr_type = RTN_UNSPEC;
	131	if (hook != NF_IP_FORWARD
	132	#ifdef CONFIG_BRIDGE_NETFILTER
	133	\|\| (nskb->nf_bridge && nskb->nf_bridge->mask & BRNF_BRIDGED)
	134	#endif
	135	)
	136	addr_type = RTN_LOCAL;
	137
	138	if (ip_route_me_harder(&nskb, addr_type))
	139	goto free_nskb;
	140
4cf411de	141	nskb->ip_summed = CHECKSUM_NONE;
af443b6d	142
9d02002d	143	/* Adjust IP TTL */
e8eaedf2	144	nskb->nh.iph->ttl = dst_metric(nskb->dst, RTAX_HOPLIMIT);
1da177e4 LT	145
	146	/* Adjust IP checksum */
	147	nskb->nh.iph->check = 0;
e905a9ed	148	nskb->nh.iph->check = ip_fast_csum((unsigned char *)nskb->nh.iph,
1da177e4 LT	149	nskb->nh.iph->ihl);
	150
	151	/* "Never happens" */
	152	if (nskb->len > dst_mtu(nskb->dst))
	153	goto free_nskb;
	154
	155	nf_ct_attach(nskb, oldskb);
	156
	157	NF_HOOK(PF_INET, NF_IP_LOCAL_OUT, nskb, NULL, nskb->dst->dev,
	158	dst_output);
	159	return;
	160
	161	free_nskb:
	162	kfree_skb(nskb);
	163	}
	164
	165	static inline void send_unreach(struct sk_buff *skb_in, int code)
	166	{
	167	icmp_send(skb_in, ICMP_DEST_UNREACH, code, 0);
e905a9ed	168	}
1da177e4 LT	169
	170	static unsigned int reject(struct sk_buff **pskb,
	171	const struct net_device *in,
	172	const struct net_device *out,
	173	unsigned int hooknum,
c4986734	174	const struct xt_target *target,
fe1cb108	175	const void *targinfo)
1da177e4 LT	176	{
	177	const struct ipt_reject_info *reject = targinfo;
	178
	179	/* Our naive response construction doesn't deal with IP
e905a9ed	180	options, and probably shouldn't try. */
1da177e4 LT	181	if ((*pskb)->nh.iph->ihl<<2 != sizeof(struct iphdr))
	182	return NF_DROP;
	183
	184	/* WARNING: This code causes reentry within iptables.
	185	This means that the iptables jump stack is now crap. We
	186	must return an absolute verdict. --RR */
e905a9ed YH	187	switch (reject->with) {
	188	case IPT_ICMP_NET_UNREACHABLE:
	189	send_unreach(*pskb, ICMP_NET_UNREACH);
	190	break;
	191	case IPT_ICMP_HOST_UNREACHABLE:
	192	send_unreach(*pskb, ICMP_HOST_UNREACH);
	193	break;
	194	case IPT_ICMP_PROT_UNREACHABLE:
	195	send_unreach(*pskb, ICMP_PROT_UNREACH);
	196	break;
	197	case IPT_ICMP_PORT_UNREACHABLE:
	198	send_unreach(*pskb, ICMP_PORT_UNREACH);
	199	break;
	200	case IPT_ICMP_NET_PROHIBITED:
	201	send_unreach(*pskb, ICMP_NET_ANO);
	202	break;
1da177e4	203	case IPT_ICMP_HOST_PROHIBITED:
e905a9ed YH	204	send_unreach(*pskb, ICMP_HOST_ANO);
	205	break;
	206	case IPT_ICMP_ADMIN_PROHIBITED:
1da177e4 LT	207	send_unreach(*pskb, ICMP_PKT_FILTERED);
	208	break;
	209	case IPT_TCP_RESET:
	210	send_reset(*pskb, hooknum);
	211	case IPT_ICMP_ECHOREPLY:
	212	/* Doesn't happen. */
	213	break;
	214	}
	215
	216	return NF_DROP;
	217	}
	218
	219	static int check(const char *tablename,
2e4e6a17	220	const void *e_void,
c4986734	221	const struct xt_target *target,
1da177e4	222	void *targinfo,
1da177e4 LT	223	unsigned int hook_mask)
1da177e4 LT	224	{
e905a9ed	225	const struct ipt_reject_info *rejinfo = targinfo;
2e4e6a17	226	const struct ipt_entry *e = e_void;
1da177e4	227
1da177e4 LT	228	if (rejinfo->with == IPT_ICMP_ECHOREPLY) {
	229	printk("REJECT: ECHOREPLY no longer supported.\n");
	230	return 0;
	231	} else if (rejinfo->with == IPT_TCP_RESET) {
	232	/* Must specify that it's a TCP packet */
	233	if (e->ip.proto != IPPROTO_TCP
6709dbbb	234	\|\| (e->ip.invflags & XT_INV_PROTO)) {
1da177e4 LT	235	DEBUGP("REJECT: TCP_RESET invalid for non-tcp\n");
	236	return 0;
	237	}
	238	}
1da177e4 LT	239	return 1;
	240	}
	241
6709dbbb	242	static struct xt_target ipt_reject_reg = {
1da177e4	243	.name = "REJECT",
6709dbbb	244	.family = AF_INET,
1da177e4	245	.target = reject,
1d5cd909 PM	246	.targetsize = sizeof(struct ipt_reject_info),
	247	.table = "filter",
	248	.hooks = (1 << NF_IP_LOCAL_IN) \| (1 << NF_IP_FORWARD) \|
	249	(1 << NF_IP_LOCAL_OUT),
1da177e4 LT	250	.checkentry = check,
	251	.me = THIS_MODULE,
	252	};
	253
65b4b4e8	254	static int __init ipt_reject_init(void)
1da177e4	255	{
6709dbbb	256	return xt_register_target(&ipt_reject_reg);
1da177e4 LT	257	}
1da177e4 LT	258
65b4b4e8	259	static void __exit ipt_reject_fini(void)
1da177e4	260	{
6709dbbb	261	xt_unregister_target(&ipt_reject_reg);
1da177e4 LT	262	}
1da177e4 LT	263
65b4b4e8 AM	264	module_init(ipt_reject_init);
65b4b4e8 AM	265	module_exit(ipt_reject_fini);