[linux-2.6-block.git] / net / ipv4 / netfilter / nf_reject_ipv4.c

/* (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 <net/ip.h>
#include <net/tcp.h>
#include <net/route.h>
#include <net/dst.h>
#include <net/netfilter/ipv4/nf_reject.h>
#include <linux/netfilter_ipv4.h>
#include <linux/netfilter_bridge.h>

const struct tcphdr *nf_reject_ip_tcphdr_get(struct sk_buff *oldskb,
					     struct tcphdr *_oth, int hook)
{
	const struct tcphdr *oth;

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

	if (ip_hdr(oldskb)->protocol != IPPROTO_TCP)
		return NULL;

	oth = skb_header_pointer(oldskb, ip_hdrlen(oldskb),
				 sizeof(struct tcphdr), _oth);
	if (oth == NULL)
		return NULL;

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

	/* Check checksum */
	if (nf_ip_checksum(oldskb, hook, ip_hdrlen(oldskb), IPPROTO_TCP))
		return NULL;

	return oth;
}
EXPORT_SYMBOL_GPL(nf_reject_ip_tcphdr_get);

struct iphdr *nf_reject_iphdr_put(struct sk_buff *nskb,
				  const struct sk_buff *oldskb,
				  __u8 protocol, int ttl)
{
	struct iphdr *niph, *oiph = ip_hdr(oldskb);

	skb_reset_network_header(nskb);
	niph = skb_put(nskb, sizeof(struct iphdr));
	niph->version	= 4;
	niph->ihl	= sizeof(struct iphdr) / 4;
	niph->tos	= 0;
	niph->id	= 0;
	niph->frag_off	= htons(IP_DF);
	niph->protocol	= protocol;
	niph->check	= 0;
	niph->saddr	= oiph->daddr;
	niph->daddr	= oiph->saddr;
	niph->ttl	= ttl;

	nskb->protocol = htons(ETH_P_IP);

	return niph;
}
EXPORT_SYMBOL_GPL(nf_reject_iphdr_put);

void nf_reject_ip_tcphdr_put(struct sk_buff *nskb, const struct sk_buff *oldskb,
			  const struct tcphdr *oth)
{
	struct iphdr *niph = ip_hdr(nskb);
	struct tcphdr *tcph;

	skb_reset_transport_header(nskb);
	tcph = skb_put_zero(nskb, sizeof(struct tcphdr));
	tcph->source	= oth->dest;
	tcph->dest	= oth->source;
	tcph->doff	= sizeof(struct tcphdr) / 4;

	if (oth->ack) {
		tcph->seq = oth->ack_seq;
	} else {
		tcph->ack_seq = htonl(ntohl(oth->seq) + oth->syn + oth->fin +
				      oldskb->len - ip_hdrlen(oldskb) -
				      (oth->doff << 2));
		tcph->ack = 1;
	}

	tcph->rst	= 1;
	tcph->check = ~tcp_v4_check(sizeof(struct tcphdr), niph->saddr,
				    niph->daddr, 0);
	nskb->ip_summed = CHECKSUM_PARTIAL;
	nskb->csum_start = (unsigned char *)tcph - nskb->head;
	nskb->csum_offset = offsetof(struct tcphdr, check);
}
EXPORT_SYMBOL_GPL(nf_reject_ip_tcphdr_put);

/* Send RST reply */
void nf_send_reset(struct net *net, struct sk_buff *oldskb, int hook)
{
	struct net_device *br_indev __maybe_unused;
	struct sk_buff *nskb;
	struct iphdr *niph;
	const struct tcphdr *oth;
	struct tcphdr _oth;

	oth = nf_reject_ip_tcphdr_get(oldskb, &_oth, hook);
	if (!oth)
		return;

	if (skb_rtable(oldskb)->rt_flags & (RTCF_BROADCAST | RTCF_MULTICAST))
		return;

	nskb = alloc_skb(sizeof(struct iphdr) + sizeof(struct tcphdr) +
			 LL_MAX_HEADER, GFP_ATOMIC);
	if (!nskb)
		return;

	/* ip_route_me_harder expects skb->dst to be set */
	skb_dst_set_noref(nskb, skb_dst(oldskb));

	nskb->mark = IP4_REPLY_MARK(net, oldskb->mark);

	skb_reserve(nskb, LL_MAX_HEADER);
	niph = nf_reject_iphdr_put(nskb, oldskb, IPPROTO_TCP,
				   ip4_dst_hoplimit(skb_dst(nskb)));
	nf_reject_ip_tcphdr_put(nskb, oldskb, oth);

	if (ip_route_me_harder(net, nskb, RTN_UNSPEC))
		goto free_nskb;

	niph = ip_hdr(nskb);

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

	nf_ct_attach(nskb, oldskb);

#if IS_ENABLED(CONFIG_BRIDGE_NETFILTER)
	/* If we use ip_local_out for bridged traffic, the MAC source on
	 * the RST will be ours, instead of the destination's.  This confuses
	 * some routers/firewalls, and they drop the packet.  So we need to
	 * build the eth header using the original destination's MAC as the
	 * source, and send the RST packet directly.
	 */
	br_indev = nf_bridge_get_physindev(oldskb);
	if (br_indev) {
		struct ethhdr *oeth = eth_hdr(oldskb);

		nskb->dev = br_indev;
		niph->tot_len = htons(nskb->len);
		ip_send_check(niph);
		if (dev_hard_header(nskb, nskb->dev, ntohs(nskb->protocol),
				    oeth->h_source, oeth->h_dest, nskb->len) < 0)
			goto free_nskb;
		dev_queue_xmit(nskb);
	} else
#endif
		ip_local_out(net, nskb->sk, nskb);

	return;

 free_nskb:
	kfree_skb(nskb);
}
EXPORT_SYMBOL_GPL(nf_send_reset);

void nf_send_unreach(struct sk_buff *skb_in, int code, int hook)
{
	struct iphdr *iph = ip_hdr(skb_in);
	u8 proto;

	if (iph->frag_off & htons(IP_OFFSET))
		return;

	if (skb_csum_unnecessary(skb_in)) {
		icmp_send(skb_in, ICMP_DEST_UNREACH, code, 0);
		return;
	}

	if (iph->protocol == IPPROTO_TCP || iph->protocol == IPPROTO_UDP)
		proto = iph->protocol;
	else
		proto = 0;

	if (nf_ip_checksum(skb_in, hook, ip_hdrlen(skb_in), proto) == 0)
		icmp_send(skb_in, ICMP_DEST_UNREACH, code, 0);
}
EXPORT_SYMBOL_GPL(nf_send_unreach);

MODULE_LICENSE("GPL");
Commit	Line	Data
c8d7b98b PNA	1	/* (C) 1999-2001 Paul `Rusty' Russell
	2	* (C) 2002-2004 Netfilter Core Team <coreteam@netfilter.org>
	3	*
	4	* This program is free software; you can redistribute it and/or modify
	5	* it under the terms of the GNU General Public License version 2 as
	6	* published by the Free Software Foundation.
	7	*/
	8
ab2d7251	9	#include <linux/module.h>
c8d7b98b PNA	10	#include <net/ip.h>
	11	#include <net/tcp.h>
	12	#include <net/route.h>
	13	#include <net/dst.h>
56768644	14	#include <net/netfilter/ipv4/nf_reject.h>
c8d7b98b	15	#include <linux/netfilter_ipv4.h>
c737b7c4	16	#include <linux/netfilter_bridge.h>
c8d7b98b	17
052b9498 PNA	18	const struct tcphdr nf_reject_ip_tcphdr_get(struct sk_buff oldskb,
052b9498 PNA	19	struct tcphdr *_oth, int hook)
c8d7b98b	20	{
c8d7b98b	21	const struct tcphdr *oth;
c8d7b98b PNA	22
	23	/* IP header checks: fragment. */
	24	if (ip_hdr(oldskb)->frag_off & htons(IP_OFFSET))
052b9498	25	return NULL;
c8d7b98b	26
e1dbbc59 LZ	27	if (ip_hdr(oldskb)->protocol != IPPROTO_TCP)
	28	return NULL;
	29
c8d7b98b	30	oth = skb_header_pointer(oldskb, ip_hdrlen(oldskb),
052b9498	31	sizeof(struct tcphdr), _oth);
c8d7b98b	32	if (oth == NULL)
052b9498	33	return NULL;
c8d7b98b PNA	34
	35	/* No RST for RST. */
	36	if (oth->rst)
052b9498	37	return NULL;
c8d7b98b PNA	38
	39	/* Check checksum */
	40	if (nf_ip_checksum(oldskb, hook, ip_hdrlen(oldskb), IPPROTO_TCP))
052b9498	41	return NULL;
c8d7b98b	42
052b9498 PNA	43	return oth;
	44	}
	45	EXPORT_SYMBOL_GPL(nf_reject_ip_tcphdr_get);
c8d7b98b	46
052b9498 PNA	47	struct iphdr nf_reject_iphdr_put(struct sk_buff nskb,
052b9498 PNA	48	const struct sk_buff *oldskb,
a03a8dbe	49	__u8 protocol, int ttl)
052b9498 PNA	50	{
052b9498 PNA	51	struct iphdr niph, oiph = ip_hdr(oldskb);
c8d7b98b PNA	52
c8d7b98b PNA	53	skb_reset_network_header(nskb);
4df864c1	54	niph = skb_put(nskb, sizeof(struct iphdr));
c8d7b98b PNA	55	niph->version = 4;
	56	niph->ihl = sizeof(struct iphdr) / 4;
	57	niph->tos = 0;
	58	niph->id = 0;
	59	niph->frag_off = htons(IP_DF);
052b9498	60	niph->protocol = protocol;
c8d7b98b PNA	61	niph->check = 0;
	62	niph->saddr = oiph->daddr;
	63	niph->daddr = oiph->saddr;
052b9498 PNA	64	niph->ttl = ttl;
	65
	66	nskb->protocol = htons(ETH_P_IP);
	67
	68	return niph;
	69	}
	70	EXPORT_SYMBOL_GPL(nf_reject_iphdr_put);
	71
	72	void nf_reject_ip_tcphdr_put(struct sk_buff nskb, const struct sk_buff oldskb,
	73	const struct tcphdr *oth)
	74	{
	75	struct iphdr *niph = ip_hdr(nskb);
	76	struct tcphdr *tcph;
c8d7b98b PNA	77
c8d7b98b PNA	78	skb_reset_transport_header(nskb);
b080db58	79	tcph = skb_put_zero(nskb, sizeof(struct tcphdr));
c8d7b98b PNA	80	tcph->source = oth->dest;
	81	tcph->dest = oth->source;
	82	tcph->doff = sizeof(struct tcphdr) / 4;
	83
052b9498	84	if (oth->ack) {
c8d7b98b	85	tcph->seq = oth->ack_seq;
052b9498	86	} else {
c8d7b98b PNA	87	tcph->ack_seq = htonl(ntohl(oth->seq) + oth->syn + oth->fin +
	88	oldskb->len - ip_hdrlen(oldskb) -
	89	(oth->doff << 2));
	90	tcph->ack = 1;
	91	}
	92
	93	tcph->rst = 1;
	94	tcph->check = ~tcp_v4_check(sizeof(struct tcphdr), niph->saddr,
	95	niph->daddr, 0);
	96	nskb->ip_summed = CHECKSUM_PARTIAL;
	97	nskb->csum_start = (unsigned char *)tcph - nskb->head;
	98	nskb->csum_offset = offsetof(struct tcphdr, check);
052b9498 PNA	99	}
	100	EXPORT_SYMBOL_GPL(nf_reject_ip_tcphdr_put);
	101
	102	/* Send RST reply */
372892ec	103	void nf_send_reset(struct net net, struct sk_buff oldskb, int hook)
052b9498	104	{
c4b0e771	105	struct net_device *br_indev __maybe_unused;
052b9498	106	struct sk_buff *nskb;
052b9498 PNA	107	struct iphdr *niph;
	108	const struct tcphdr *oth;
	109	struct tcphdr _oth;
	110
	111	oth = nf_reject_ip_tcphdr_get(oldskb, &_oth, hook);
	112	if (!oth)
	113	return;
	114
	115	if (skb_rtable(oldskb)->rt_flags & (RTCF_BROADCAST \| RTCF_MULTICAST))
	116	return;
	117
052b9498 PNA	118	nskb = alloc_skb(sizeof(struct iphdr) + sizeof(struct tcphdr) +
	119	LL_MAX_HEADER, GFP_ATOMIC);
	120	if (!nskb)
	121	return;
c8d7b98b PNA	122
	123	/* ip_route_me_harder expects skb->dst to be set */
	124	skb_dst_set_noref(nskb, skb_dst(oldskb));
	125
cc31d43b PEP	126	nskb->mark = IP4_REPLY_MARK(net, oldskb->mark);
cc31d43b PEP	127
052b9498 PNA	128	skb_reserve(nskb, LL_MAX_HEADER);
	129	niph = nf_reject_iphdr_put(nskb, oldskb, IPPROTO_TCP,
	130	ip4_dst_hoplimit(skb_dst(nskb)));
	131	nf_reject_ip_tcphdr_put(nskb, oldskb, oth);
	132
e45f5066	133	if (ip_route_me_harder(net, nskb, RTN_UNSPEC))
c8d7b98b PNA	134	goto free_nskb;
c8d7b98b PNA	135
7400bb4b TT	136	niph = ip_hdr(nskb);
7400bb4b TT	137
c8d7b98b PNA	138	/* "Never happens" */
	139	if (nskb->len > dst_mtu(skb_dst(nskb)))
	140	goto free_nskb;
	141
	142	nf_ct_attach(nskb, oldskb);
	143
	144	#if IS_ENABLED(CONFIG_BRIDGE_NETFILTER)
	145	/* If we use ip_local_out for bridged traffic, the MAC source on
	146	* the RST will be ours, instead of the destination's. This confuses
	147	* some routers/firewalls, and they drop the packet. So we need to
	148	* build the eth header using the original destination's MAC as the
	149	* source, and send the RST packet directly.
	150	*/
c4b0e771 FW	151	br_indev = nf_bridge_get_physindev(oldskb);
c4b0e771 FW	152	if (br_indev) {
c8d7b98b	153	struct ethhdr *oeth = eth_hdr(oldskb);
c737b7c4	154
c4b0e771	155	nskb->dev = br_indev;
c8d7b98b PNA	156	niph->tot_len = htons(nskb->len);
	157	ip_send_check(niph);
	158	if (dev_hard_header(nskb, nskb->dev, ntohs(nskb->protocol),
	159	oeth->h_source, oeth->h_dest, nskb->len) < 0)
	160	goto free_nskb;
	161	dev_queue_xmit(nskb);
	162	} else
	163	#endif
33224b16	164	ip_local_out(net, nskb->sk, nskb);
c8d7b98b PNA	165
	166	return;
	167
	168	free_nskb:
	169	kfree_skb(nskb);
	170	}
	171	EXPORT_SYMBOL_GPL(nf_send_reset);
ab2d7251	172
ee586bbc FW	173	void nf_send_unreach(struct sk_buff *skb_in, int code, int hook)
	174	{
	175	struct iphdr *iph = ip_hdr(skb_in);
	176	u8 proto;
	177
219f1d79	178	if (iph->frag_off & htons(IP_OFFSET))
ee586bbc FW	179	return;
	180
	181	if (skb_csum_unnecessary(skb_in)) {
	182	icmp_send(skb_in, ICMP_DEST_UNREACH, code, 0);
	183	return;
	184	}
	185
	186	if (iph->protocol == IPPROTO_TCP \|\| iph->protocol == IPPROTO_UDP)
	187	proto = iph->protocol;
	188	else
	189	proto = 0;
	190
	191	if (nf_ip_checksum(skb_in, hook, ip_hdrlen(skb_in), proto) == 0)
	192	icmp_send(skb_in, ICMP_DEST_UNREACH, code, 0);
	193	}
	194	EXPORT_SYMBOL_GPL(nf_send_unreach);
	195
ab2d7251	196	MODULE_LICENSE("GPL");