[mirror_ubuntu-bionic-kernel.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 <linux/slab.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(dev_net(skb_dst(skb)->dev), IPSTATS_MIB_OUTFORWDATAGRAMS);
	IP_ADD_STATS_BH(dev_net(skb_dst(skb)->dev), IPSTATS_MIB_OUTOCTETS, skb->len);

	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 (skb_warn_if_lro(skb))
		goto drop;

	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(skb);

	if (opt->is_strictroute && rt->rt_uses_gateway)
		goto sr_failed;

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

	/* We are about to mangle packet. Copy it! */
	if (skb_cow(skb, LL_RESERVED_SPACE(rt->dst.dev)+rt->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_sec_path(skb))
		ip_rt_send_redirect(skb);

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

	return NF_HOOK(NFPROTO_IPV4, NF_INET_FORWARD, skb, skb->dev,
		       rt->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(dev_net(skb_dst(skb)->dev), 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>
5a0e3ad6	28	#include <linux/slab.h>
1da177e4 LT	29	#include <net/sock.h>
	30	#include <net/ip.h>
	31	#include <net/tcp.h>
	32	#include <net/udp.h>
	33	#include <net/icmp.h>
	34	#include <linux/tcp.h>
	35	#include <linux/udp.h>
	36	#include <linux/netfilter_ipv4.h>
	37	#include <net/checksum.h>
	38	#include <linux/route.h>
	39	#include <net/route.h>
	40	#include <net/xfrm.h>
	41
861d0486	42	static int ip_forward_finish(struct sk_buff *skb)
1da177e4	43	{
5e73ea1a	44	struct ip_options *opt = &(IPCB(skb)->opt);
1da177e4	45
adf30907	46	IP_INC_STATS_BH(dev_net(skb_dst(skb)->dev), IPSTATS_MIB_OUTFORWDATAGRAMS);
2d8dbb04	47	IP_ADD_STATS_BH(dev_net(skb_dst(skb)->dev), IPSTATS_MIB_OUTOCTETS, skb->len);
1da177e4 LT	48
	49	if (unlikely(opt->optlen))
	50	ip_forward_options(skb);
	51
	52	return dst_output(skb);
	53	}
	54
	55	int ip_forward(struct sk_buff *skb)
	56	{
	57	struct iphdr iph; / Our header */
	58	struct rtable rt; / Route we use */
5e73ea1a	59	struct ip_options *opt = &(IPCB(skb)->opt);
1da177e4	60
4497b076 BH	61	if (skb_warn_if_lro(skb))
	62	goto drop;
	63
1da177e4 LT	64	if (!xfrm4_policy_check(NULL, XFRM_POLICY_FWD, skb))
	65	goto drop;
	66
	67	if (IPCB(skb)->opt.router_alert && ip_call_ra_chain(skb))
	68	return NET_RX_SUCCESS;
	69
	70	if (skb->pkt_type != PACKET_HOST)
	71	goto drop;
	72
35fc92a9	73	skb_forward_csum(skb);
e905a9ed	74
1da177e4 LT	75	/*
	76	* According to the RFC, we must first decrease the TTL field. If
	77	* that reaches zero, we must reply an ICMP control message telling
	78	* that the packet's lifetime expired.
	79	*/
eddc9ec5	80	if (ip_hdr(skb)->ttl <= 1)
e905a9ed	81	goto too_many_hops;
1da177e4 LT	82
	83	if (!xfrm4_route_forward(skb))
	84	goto drop;
	85
511c3f92	86	rt = skb_rtable(skb);
1da177e4	87
155e8336	88	if (opt->is_strictroute && rt->rt_uses_gateway)
1da177e4 LT	89	goto sr_failed;
1da177e4 LT	90
d8d1f30b	91	if (unlikely(skb->len > dst_mtu(&rt->dst) && !skb_is_gso(skb) &&
9c681b43	92	(ip_hdr(skb)->frag_off & htons(IP_DF))) && !skb->local_df) {
d8d1f30b	93	IP_INC_STATS(dev_net(rt->dst.dev), IPSTATS_MIB_FRAGFAILS);
9af3912e	94	icmp_send(skb, ICMP_DEST_UNREACH, ICMP_FRAG_NEEDED,
d8d1f30b	95	htonl(dst_mtu(&rt->dst)));
9af3912e JH	96	goto drop;
	97	}
	98
1da177e4	99	/* We are about to mangle packet. Copy it! */
d8d1f30b	100	if (skb_cow(skb, LL_RESERVED_SPACE(rt->dst.dev)+rt->dst.header_len))
1da177e4	101	goto drop;
eddc9ec5	102	iph = ip_hdr(skb);
1da177e4 LT	103
	104	/* Decrease ttl after skb cow done */
	105	ip_decrease_ttl(iph);
	106
	107	/*
	108	* We now generate an ICMP HOST REDIRECT giving the route
	109	* we calculated.
	110	*/
def8b4fa	111	if (rt->rt_flags&RTCF_DOREDIRECT && !opt->srr && !skb_sec_path(skb))
1da177e4 LT	112	ip_rt_send_redirect(skb);
	113
	114	skb->priority = rt_tos2priority(iph->tos);
	115
9bbc768a	116	return NF_HOOK(NFPROTO_IPV4, NF_INET_FORWARD, skb, skb->dev,
d8d1f30b	117	rt->dst.dev, ip_forward_finish);
1da177e4 LT	118
1da177e4 LT	119	sr_failed:
e905a9ed	120	/*
1da177e4 LT	121	* Strict routing permits no gatewaying
1da177e4 LT	122	*/
e905a9ed YH	123	icmp_send(skb, ICMP_DEST_UNREACH, ICMP_SR_FAILED, 0);
e905a9ed YH	124	goto drop;
1da177e4 LT	125
1da177e4 LT	126	too_many_hops:
e905a9ed	127	/* Tell the sender its packet died... */
adf30907	128	IP_INC_STATS_BH(dev_net(skb_dst(skb)->dev), IPSTATS_MIB_INHDRERRORS);
e905a9ed	129	icmp_send(skb, ICMP_TIME_EXCEEDED, ICMP_EXC_TTL, 0);
1da177e4 LT	130	drop:
	131	kfree_skb(skb);
	132	return NET_RX_DROP;
	133	}