[deliverable/linux.git] / net / ipv4 / ip_forward.c

/*
 * INET		An implementation of the TCP/IP protocol suite for the LINUX
 *		operating system.  INET is implemented using the  BSD Socket
 *		interface as the means of communication with the user level.
 *
 *		The IP forwarding functionality.
 *
 * Authors:	see ip.c
 *
 * Fixes:
 *		Many		:	Split from ip.c , see ip_input.c for
 *					history.
 *		Dave Gregorich	:	NULL ip_rt_put fix for multicast
 *					routing.
 *		Jos Vos		:	Add call_out_firewall before sending,
 *					use output device for accounting.
 *		Jos Vos		:	Call forward firewall after routing
 *					(always use output device).
 *		Mike McLagan	:	Routing by source
 */

#include <linux/types.h>
#include <linux/mm.h>
#include <linux/skbuff.h>
#include <linux/ip.h>
#include <linux/icmp.h>
#include <linux/netdevice.h>
#include <net/sock.h>
#include <net/ip.h>
#include <net/tcp.h>
#include <net/udp.h>
#include <net/icmp.h>
#include <linux/tcp.h>
#include <linux/udp.h>
#include <linux/netfilter_ipv4.h>
#include <net/checksum.h>
#include <linux/route.h>
#include <net/route.h>
#include <net/xfrm.h>

static int ip_forward_finish(struct sk_buff *skb)
{
	struct ip_options * opt	= &(IPCB(skb)->opt);

	IP_INC_STATS_BH(IPSTATS_MIB_OUTFORWDATAGRAMS);

	if (unlikely(opt->optlen))
		ip_forward_options(skb);

	return dst_output(skb);
}

int ip_forward(struct sk_buff *skb)
{
	struct iphdr *iph;	/* Our header */
	struct rtable *rt;	/* Route we use */
	struct ip_options * opt	= &(IPCB(skb)->opt);

	if (!xfrm4_policy_check(NULL, XFRM_POLICY_FWD, skb))
		goto drop;

	if (IPCB(skb)->opt.router_alert && ip_call_ra_chain(skb))
		return NET_RX_SUCCESS;

	if (skb->pkt_type != PACKET_HOST)
		goto drop;

	skb_forward_csum(skb);

	/*
	 *	According to the RFC, we must first decrease the TTL field. If
	 *	that reaches zero, we must reply an ICMP control message telling
	 *	that the packet's lifetime expired.
	 */
	if (ip_hdr(skb)->ttl <= 1)
		goto too_many_hops;

	if (!xfrm4_route_forward(skb))
		goto drop;

	rt = skb->rtable;

	if (opt->is_strictroute && rt->rt_dst != rt->rt_gateway)
		goto sr_failed;

	if (unlikely(skb->len > dst_mtu(&rt->u.dst) && !skb_is_gso(skb) &&
		     (ip_hdr(skb)->frag_off & htons(IP_DF))) && !skb->local_df) {
		IP_INC_STATS(IPSTATS_MIB_FRAGFAILS);
		icmp_send(skb, ICMP_DEST_UNREACH, ICMP_FRAG_NEEDED,
			  htonl(dst_mtu(&rt->u.dst)));
		goto drop;
	}

	/* We are about to mangle packet. Copy it! */
	if (skb_cow(skb, LL_RESERVED_SPACE(rt->u.dst.dev)+rt->u.dst.header_len))
		goto drop;
	iph = ip_hdr(skb);

	/* Decrease ttl after skb cow done */
	ip_decrease_ttl(iph);

	/*
	 *	We now generate an ICMP HOST REDIRECT giving the route
	 *	we calculated.
	 */
	if (rt->rt_flags&RTCF_DOREDIRECT && !opt->srr && !skb->sp)
		ip_rt_send_redirect(skb);

	skb->priority = rt_tos2priority(iph->tos);

	return NF_HOOK(PF_INET, NF_INET_FORWARD, skb, skb->dev, rt->u.dst.dev,
		       ip_forward_finish);

sr_failed:
	/*
	 *	Strict routing permits no gatewaying
	 */
	 icmp_send(skb, ICMP_DEST_UNREACH, ICMP_SR_FAILED, 0);
	 goto drop;

too_many_hops:
	/* Tell the sender its packet died... */
	IP_INC_STATS_BH(IPSTATS_MIB_INHDRERRORS);
	icmp_send(skb, ICMP_TIME_EXCEEDED, ICMP_EXC_TTL, 0);
drop:
	kfree_skb(skb);
	return NET_RX_DROP;
}
Commit	Line	Data
1da177e4 LT	1	/*
	2	* INET An implementation of the TCP/IP protocol suite for the LINUX
	3	* operating system. INET is implemented using the BSD Socket
	4	* interface as the means of communication with the user level.
	5	*
	6	* The IP forwarding functionality.
e905a9ed	7	*
1da177e4 LT	8	* Authors: see ip.c
	9	*
	10	* Fixes:
e905a9ed	11	* Many : Split from ip.c , see ip_input.c for
1da177e4	12	* history.
e905a9ed	13	* Dave Gregorich : NULL ip_rt_put fix for multicast
1da177e4 LT	14	* routing.
	15	* Jos Vos : Add call_out_firewall before sending,
	16	* use output device for accounting.
	17	* Jos Vos : Call forward firewall after routing
	18	* (always use output device).
	19	* Mike McLagan : Routing by source
	20	*/
	21
1da177e4 LT	22	#include <linux/types.h>
1da177e4 LT	23	#include <linux/mm.h>
1da177e4 LT	24	#include <linux/skbuff.h>
	25	#include <linux/ip.h>
	26	#include <linux/icmp.h>
	27	#include <linux/netdevice.h>
	28	#include <net/sock.h>
	29	#include <net/ip.h>
	30	#include <net/tcp.h>
	31	#include <net/udp.h>
	32	#include <net/icmp.h>
	33	#include <linux/tcp.h>
	34	#include <linux/udp.h>
	35	#include <linux/netfilter_ipv4.h>
	36	#include <net/checksum.h>
	37	#include <linux/route.h>
	38	#include <net/route.h>
	39	#include <net/xfrm.h>
	40
861d0486	41	static int ip_forward_finish(struct sk_buff *skb)
1da177e4 LT	42	{
	43	struct ip_options * opt = &(IPCB(skb)->opt);
	44
	45	IP_INC_STATS_BH(IPSTATS_MIB_OUTFORWDATAGRAMS);
	46
	47	if (unlikely(opt->optlen))
	48	ip_forward_options(skb);
	49
	50	return dst_output(skb);
	51	}
	52
	53	int ip_forward(struct sk_buff *skb)
	54	{
	55	struct iphdr iph; / Our header */
	56	struct rtable rt; / Route we use */
	57	struct ip_options * opt = &(IPCB(skb)->opt);
	58
	59	if (!xfrm4_policy_check(NULL, XFRM_POLICY_FWD, skb))
	60	goto drop;
	61
	62	if (IPCB(skb)->opt.router_alert && ip_call_ra_chain(skb))
	63	return NET_RX_SUCCESS;
	64
	65	if (skb->pkt_type != PACKET_HOST)
	66	goto drop;
	67
35fc92a9	68	skb_forward_csum(skb);
e905a9ed	69
1da177e4 LT	70	/*
	71	* According to the RFC, we must first decrease the TTL field. If
	72	* that reaches zero, we must reply an ICMP control message telling
	73	* that the packet's lifetime expired.
	74	*/
eddc9ec5	75	if (ip_hdr(skb)->ttl <= 1)
e905a9ed	76	goto too_many_hops;
1da177e4 LT	77
	78	if (!xfrm4_route_forward(skb))
	79	goto drop;
	80
ee6b9673	81	rt = skb->rtable;
1da177e4 LT	82
	83	if (opt->is_strictroute && rt->rt_dst != rt->rt_gateway)
	84	goto sr_failed;
	85
32aced75	86	if (unlikely(skb->len > dst_mtu(&rt->u.dst) && !skb_is_gso(skb) &&
9c681b43	87	(ip_hdr(skb)->frag_off & htons(IP_DF))) && !skb->local_df) {
9af3912e JH	88	IP_INC_STATS(IPSTATS_MIB_FRAGFAILS);
	89	icmp_send(skb, ICMP_DEST_UNREACH, ICMP_FRAG_NEEDED,
	90	htonl(dst_mtu(&rt->u.dst)));
	91	goto drop;
	92	}
	93
1da177e4 LT	94	/* We are about to mangle packet. Copy it! */
	95	if (skb_cow(skb, LL_RESERVED_SPACE(rt->u.dst.dev)+rt->u.dst.header_len))
	96	goto drop;
eddc9ec5	97	iph = ip_hdr(skb);
1da177e4 LT	98
	99	/* Decrease ttl after skb cow done */
	100	ip_decrease_ttl(iph);
	101
	102	/*
	103	* We now generate an ICMP HOST REDIRECT giving the route
	104	* we calculated.
	105	*/
3b26a9a6	106	if (rt->rt_flags&RTCF_DOREDIRECT && !opt->srr && !skb->sp)
1da177e4 LT	107	ip_rt_send_redirect(skb);
	108
	109	skb->priority = rt_tos2priority(iph->tos);
	110
6e23ae2a	111	return NF_HOOK(PF_INET, NF_INET_FORWARD, skb, skb->dev, rt->u.dst.dev,
1da177e4 LT	112	ip_forward_finish);
	113
	114	sr_failed:
e905a9ed	115	/*
1da177e4 LT	116	* Strict routing permits no gatewaying
1da177e4 LT	117	*/
e905a9ed YH	118	icmp_send(skb, ICMP_DEST_UNREACH, ICMP_SR_FAILED, 0);
e905a9ed YH	119	goto drop;
1da177e4 LT	120
1da177e4 LT	121	too_many_hops:
e905a9ed YH	122	/* Tell the sender its packet died... */
	123	IP_INC_STATS_BH(IPSTATS_MIB_INHDRERRORS);
	124	icmp_send(skb, ICMP_TIME_EXCEEDED, ICMP_EXC_TTL, 0);
1da177e4 LT	125	drop:
	126	kfree_skb(skb);
	127	return NET_RX_DROP;
	128	}