kernel / net / ipv4 / route.c

// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * 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.
 *
 *		ROUTE - implementation of the IP router.
 *
 * Authors:	Ross Biro
 *		Fred N. van Kempen, <[e-mail]>
 *		Alan Cox, <[e-mail]>
 *		Linus Torvalds, <[e-mail]>
 *		Alexey Kuznetsov, <[e-mail]>
 *
 * Fixes:
 *		Alan Cox	:	Verify area fixes.
 *		Alan Cox	:	cli() protects routing changes
 *		Rui Oliveira	:	ICMP routing table updates
 *		([e-mail])	Routing table insertion and update
 *		Linus Torvalds	:	Rewrote bits to be sensible
 *		Alan Cox	:	Added BSD route gw semantics
 *		Alan Cox	:	Super /proc >4K
 *		Alan Cox	:	MTU in route table
 *		Alan Cox	:	MSS actually. Also added the window
 *					clamper.
 *		Sam Lantinga	:	Fixed route matching in rt_del()
 *		Alan Cox	:	Routing cache support.
 *		Alan Cox	:	Removed compatibility cruft.
 *		Alan Cox	:	RTF_REJECT support.
 *		Alan Cox	:	TCP irtt support.
 *		Jonathan Naylor	:	Added Metric support.
 *	Miquel van Smoorenburg	:	BSD API fixes.
 *	Miquel van Smoorenburg	:	Metrics.
 *		Alan Cox	:	Use __u32 properly
 *		Alan Cox	:	Aligned routing errors more closely with BSD
 *					our system is still very different.
 *		Alan Cox	:	Faster /proc handling
 *	Alexey Kuznetsov	:	Massive rework to support tree based routing,
 *					routing caches and better behaviour.
 *
 *		Olaf Erb	:	irtt wasn't being copied right.
 *		Bjorn Ekwall	:	Kerneld route support.
 *		Alan Cox	:	Multicast fixed (I hope)
 *		Pavel Krauz	:	Limited broadcast fixed
 *		Mike McLagan	:	Routing by source
 *	Alexey Kuznetsov	:	End of old history. Split to fib.c and
 *					route.c and rewritten from scratch.
 *		Andi Kleen	:	Load-limit warning messages.
 *	Vitaly E. Lavrov	:	Transparent proxy revived after year coma.
 *	Vitaly E. Lavrov	:	Race condition in ip_route_input_slow.
 *	Tobias Ringstrom	:	Uninitialized res.type in ip_route_output_slow.
 *	Vladimir V. Ivanov	:	IP rule info (flowid) is really useful.
 *		Marc Boucher	:	routing by fwmark
 *	Robert Olsson		:	Added rt_cache statistics
 *	Arnaldo C. Melo		:	Convert proc stuff to seq_file
 *	Eric Dumazet		:	hashed spinlocks and rt_check_expire() fixes.
 *	Ilia Sotnikov		:	Ignore TOS on PMTUD and Redirect
 *	Ilia Sotnikov		:	Removed TOS from hash calculations
 */

#define pr_fmt(fmt) "IPv4: " fmt

#include <linux/module.h>
#include <linux/bitops.h>
#include <linux/kernel.h>
#include <linux/mm.h>
#include <linux/memblock.h>
#include <linux/socket.h>
#include <linux/errno.h>
#include <linux/in.h>
#include <linux/inet.h>
#include <linux/netdevice.h>
#include <linux/proc_fs.h>
#include <linux/init.h>
#include <linux/skbuff.h>
#include <linux/inetdevice.h>
#include <linux/igmp.h>
#include <linux/pkt_sched.h>
#include <linux/mroute.h>
#include <linux/netfilter_ipv4.h>
#include <linux/random.h>
#include <linux/rcupdate.h>
#include <linux/slab.h>
#include <linux/jhash.h>
#include <net/dst.h>
#include <net/dst_metadata.h>
#include <net/inet_dscp.h>
#include <net/net_namespace.h>
#include <net/ip.h>
#include <net/route.h>
#include <net/inetpeer.h>
#include <net/sock.h>
#include <net/ip_fib.h>
#include <net/nexthop.h>
#include <net/tcp.h>
#include <net/icmp.h>
#include <net/xfrm.h>
#include <net/lwtunnel.h>
#include <net/netevent.h>
#include <net/rtnetlink.h>
#ifdef CONFIG_SYSCTL
#include <linux/sysctl.h>
#endif
#include <net/secure_seq.h>
#include <net/ip_tunnels.h>

#include "fib_lookup.h"

#define RT_GC_TIMEOUT (300*HZ)

#define DEFAULT_MIN_PMTU (512 + 20 + 20)
#define DEFAULT_MTU_EXPIRES (10 * 60 * HZ)
#define DEFAULT_MIN_ADVMSS 256
static int ip_rt_max_size;
static int ip_rt_redirect_number __read_mostly	= 9;
static int ip_rt_redirect_load __read_mostly	= HZ / 50;
static int ip_rt_redirect_silence __read_mostly	= ((HZ / 50) << (9 + 1));
static int ip_rt_error_cost __read_mostly	= HZ;
static int ip_rt_error_burst __read_mostly	= 5 * HZ;

static int ip_rt_gc_timeout __read_mostly	= RT_GC_TIMEOUT;

/*
 *	Interface to generic destination cache.
 */

INDIRECT_CALLABLE_SCOPE
struct dst_entry	*ipv4_dst_check(struct dst_entry *dst, u32 cookie);
static unsigned int	 ipv4_default_advmss(const struct dst_entry *dst);
INDIRECT_CALLABLE_SCOPE
unsigned int		ipv4_mtu(const struct dst_entry *dst);
static void		ipv4_negative_advice(struct sock *sk,
					     struct dst_entry *dst);
static void		 ipv4_link_failure(struct sk_buff *skb);
static void		 ip_rt_update_pmtu(struct dst_entry *dst, struct sock *sk,
					   struct sk_buff *skb, u32 mtu,
					   bool confirm_neigh);
static void		 ip_do_redirect(struct dst_entry *dst, struct sock *sk,
					struct sk_buff *skb);
static void		ipv4_dst_destroy(struct dst_entry *dst);

static u32 *ipv4_cow_metrics(struct dst_entry *dst, unsigned long old)
{
	WARN_ON(1);
	return NULL;
}

static struct neighbour *ipv4_neigh_lookup(const struct dst_entry *dst,
					   struct sk_buff *skb,
					   const void *daddr);
static void ipv4_confirm_neigh(const struct dst_entry *dst, const void *daddr);

static struct dst_ops ipv4_dst_ops = {
	.family =		AF_INET,
	.check =		ipv4_dst_check,
	.default_advmss =	ipv4_default_advmss,
	.mtu =			ipv4_mtu,
	.cow_metrics =		ipv4_cow_metrics,
	.destroy =		ipv4_dst_destroy,
	.negative_advice =	ipv4_negative_advice,
	.link_failure =		ipv4_link_failure,
	.update_pmtu =		ip_rt_update_pmtu,
	.redirect =		ip_do_redirect,
	.local_out =		__ip_local_out,
	.neigh_lookup =		ipv4_neigh_lookup,
	.confirm_neigh =	ipv4_confirm_neigh,
};

#define ECN_OR_COST(class)	TC_PRIO_##class

const __u8 ip_tos2prio[16] = {
	TC_PRIO_BESTEFFORT,
	ECN_OR_COST(BESTEFFORT),
	TC_PRIO_BESTEFFORT,
	ECN_OR_COST(BESTEFFORT),
	TC_PRIO_BULK,
	ECN_OR_COST(BULK),
	TC_PRIO_BULK,
	ECN_OR_COST(BULK),
	TC_PRIO_INTERACTIVE,
	ECN_OR_COST(INTERACTIVE),
	TC_PRIO_INTERACTIVE,
	ECN_OR_COST(INTERACTIVE),
	TC_PRIO_INTERACTIVE_BULK,
	ECN_OR_COST(INTERACTIVE_BULK),
	TC_PRIO_INTERACTIVE_BULK,
	ECN_OR_COST(INTERACTIVE_BULK)
};
EXPORT_SYMBOL(ip_tos2prio);

static DEFINE_PER_CPU(struct rt_cache_stat, rt_cache_stat);
#define RT_CACHE_STAT_INC(field) raw_cpu_inc(rt_cache_stat.field)

#ifdef CONFIG_PROC_FS
static void *rt_cache_seq_start(struct seq_file *seq, loff_t *pos)
{
	if (*pos)
		return NULL;
	return SEQ_START_TOKEN;
}

static void *rt_cache_seq_next(struct seq_file *seq, void *v, loff_t *pos)
{
	++*pos;
	return NULL;
}

static void rt_cache_seq_stop(struct seq_file *seq, void *v)
{
}

static int rt_cache_seq_show(struct seq_file *seq, void *v)
{
	if (v == SEQ_START_TOKEN)
		seq_printf(seq, "%-127s\n",
			   "Iface\tDestination\tGateway \tFlags\t\tRefCnt\tUse\t"
			   "Metric\tSource\t\tMTU\tWindow\tIRTT\tTOS\tHHRef\t"
			   "HHUptod\tSpecDst");
	return 0;
}

static const struct seq_operations rt_cache_seq_ops = {
	.start  = rt_cache_seq_start,
	.next   = rt_cache_seq_next,
	.stop   = rt_cache_seq_stop,
	.show   = rt_cache_seq_show,
};

static void *rt_cpu_seq_start(struct seq_file *seq, loff_t *pos)
{
	int cpu;

	if (*pos == 0)
		return SEQ_START_TOKEN;

	for (cpu = *pos-1; cpu < nr_cpu_ids; ++cpu) {
		if (!cpu_possible(cpu))
			continue;
		*pos = cpu+1;
		return &per_cpu(rt_cache_stat, cpu);
	}
	return NULL;
}

static void *rt_cpu_seq_next(struct seq_file *seq, void *v, loff_t *pos)
{
	int cpu;

	for (cpu = *pos; cpu < nr_cpu_ids; ++cpu) {
		if (!cpu_possible(cpu))
			continue;
		*pos = cpu+1;
		return &per_cpu(rt_cache_stat, cpu);
	}
	(*pos)++;
	return NULL;

}

static void rt_cpu_seq_stop(struct seq_file *seq, void *v)
{

}

static int rt_cpu_seq_show(struct seq_file *seq, void *v)
{
	struct rt_cache_stat *st = v;

	if (v == SEQ_START_TOKEN) {
		seq_puts(seq, "entries  in_hit   in_slow_tot in_slow_mc in_no_route in_brd   in_martian_dst in_martian_src out_hit  out_slow_tot out_slow_mc gc_total gc_ignored gc_goal_miss gc_dst_overflow in_hlist_search out_hlist_search\n");
		return 0;
	}

	seq_printf(seq, "%08x %08x %08x    %08x   %08x    %08x %08x       "
			"%08x       %08x %08x     %08x    %08x %08x   "
			"%08x     %08x        %08x        %08x\n",
		   dst_entries_get_slow(&ipv4_dst_ops),
		   0, /* st->in_hit */
		   st->in_slow_tot,
		   st->in_slow_mc,
		   st->in_no_route,
		   st->in_brd,
		   st->in_martian_dst,
		   st->in_martian_src,

		   0, /* st->out_hit */
		   st->out_slow_tot,
		   st->out_slow_mc,

		   0, /* st->gc_total */
		   0, /* st->gc_ignored */
		   0, /* st->gc_goal_miss */
		   0, /* st->gc_dst_overflow */
		   0, /* st->in_hlist_search */
		   0  /* st->out_hlist_search */
		);
	return 0;
}

static const struct seq_operations rt_cpu_seq_ops = {
	.start  = rt_cpu_seq_start,
	.next   = rt_cpu_seq_next,
	.stop   = rt_cpu_seq_stop,
	.show   = rt_cpu_seq_show,
};

#ifdef CONFIG_IP_ROUTE_CLASSID
static int rt_acct_proc_show(struct seq_file *m, void *v)
{
	struct ip_rt_acct *dst, *src;
	unsigned int i, j;

	dst = kcalloc(256, sizeof(struct ip_rt_acct), GFP_KERNEL);
	if (!dst)
		return -ENOMEM;

	for_each_possible_cpu(i) {
		src = (struct ip_rt_acct *)per_cpu_ptr(ip_rt_acct, i);
		for (j = 0; j < 256; j++) {
			dst[j].o_bytes   += src[j].o_bytes;
			dst[j].o_packets += src[j].o_packets;
			dst[j].i_bytes   += src[j].i_bytes;
			dst[j].i_packets += src[j].i_packets;
		}
	}

	seq_write(m, dst, 256 * sizeof(struct ip_rt_acct));
	kfree(dst);
	return 0;
}
#endif

static int __net_init ip_rt_do_proc_init(struct net *net)
{
	struct proc_dir_entry *pde;

	pde = proc_create_seq("rt_cache", 0444, net->proc_net,
			      &rt_cache_seq_ops);
	if (!pde)
		goto err1;

	pde = proc_create_seq("rt_cache", 0444, net->proc_net_stat,
			      &rt_cpu_seq_ops);
	if (!pde)
		goto err2;

#ifdef CONFIG_IP_ROUTE_CLASSID
	pde = proc_create_single("rt_acct", 0, net->proc_net,
			rt_acct_proc_show);
	if (!pde)
		goto err3;
#endif
	return 0;

#ifdef CONFIG_IP_ROUTE_CLASSID
err3:
	remove_proc_entry("rt_cache", net->proc_net_stat);
#endif
err2:
	remove_proc_entry("rt_cache", net->proc_net);
err1:
	return -ENOMEM;
}

static void __net_exit ip_rt_do_proc_exit(struct net *net)
{
	remove_proc_entry("rt_cache", net->proc_net_stat);
	remove_proc_entry("rt_cache", net->proc_net);
#ifdef CONFIG_IP_ROUTE_CLASSID
	remove_proc_entry("rt_acct", net->proc_net);
#endif
}

static struct pernet_operations ip_rt_proc_ops __net_initdata =  {
	.init = ip_rt_do_proc_init,
	.exit = ip_rt_do_proc_exit,
};

static int __init ip_rt_proc_init(void)
{
	return register_pernet_subsys(&ip_rt_proc_ops);
}

#else
static inline int ip_rt_proc_init(void)
{
	return 0;
}
#endif /* CONFIG_PROC_FS */

static inline bool rt_is_expired(const struct rtable *rth)
{
	return rth->rt_genid != rt_genid_ipv4(dev_net(rth->dst.dev));
}

void rt_cache_flush(struct net *net)
{
	rt_genid_bump_ipv4(net);
}

static struct neighbour *ipv4_neigh_lookup(const struct dst_entry *dst,
					   struct sk_buff *skb,
					   const void *daddr)
{
	const struct rtable *rt = container_of(dst, struct rtable, dst);
	struct net_device *dev = dst->dev;
	struct neighbour *n;

	rcu_read_lock();

	if (likely(rt->rt_gw_family == AF_INET)) {
		n = ip_neigh_gw4(dev, rt->rt_gw4);
	} else if (rt->rt_gw_family == AF_INET6) {
		n = ip_neigh_gw6(dev, &rt->rt_gw6);
        } else {
		__be32 pkey;

		pkey = skb ? ip_hdr(skb)->daddr : *((__be32 *) daddr);
		n = ip_neigh_gw4(dev, pkey);
	}

	if (!IS_ERR(n) && !refcount_inc_not_zero(&n->refcnt))
		n = NULL;

	rcu_read_unlock();

	return n;
}

static void ipv4_confirm_neigh(const struct dst_entry *dst, const void *daddr)
{
	const struct rtable *rt = container_of(dst, struct rtable, dst);
	struct net_device *dev = dst->dev;
	const __be32 *pkey = daddr;

	if (rt->rt_gw_family == AF_INET) {
		pkey = (const __be32 *)&rt->rt_gw4;
	} else if (rt->rt_gw_family == AF_INET6) {
		return __ipv6_confirm_neigh_stub(dev, &rt->rt_gw6);
	} else if (!daddr ||
		 (rt->rt_flags &
		  (RTCF_MULTICAST | RTCF_BROADCAST | RTCF_LOCAL))) {
		return;
	}
	__ipv4_confirm_neigh(dev, *(__force u32 *)pkey);
}

/* Hash tables of size 2048..262144 depending on RAM size.
 * Each bucket uses 8 bytes.
 */
static u32 ip_idents_mask __read_mostly;
static atomic_t *ip_idents __read_mostly;
static u32 *ip_tstamps __read_mostly;

/* In order to protect privacy, we add a perturbation to identifiers
 * if one generator is seldom used. This makes hard for an attacker
 * to infer how many packets were sent between two points in time.
 */
static u32 ip_idents_reserve(u32 hash, int segs)
{
	u32 bucket, old, now = (u32)jiffies;
	atomic_t *p_id;
	u32 *p_tstamp;
	u32 delta = 0;

	bucket = hash & ip_idents_mask;
	p_tstamp = ip_tstamps + bucket;
	p_id = ip_idents + bucket;
	old = READ_ONCE(*p_tstamp);

	if (old != now && cmpxchg(p_tstamp, old, now) == old)
		delta = get_random_u32_below(now - old);

	/* If UBSAN reports an error there, please make sure your compiler
	 * supports -fno-strict-overflow before reporting it that was a bug
	 * in UBSAN, and it has been fixed in GCC-8.
	 */
	return atomic_add_return(segs + delta, p_id) - segs;
}

void __ip_select_ident(struct net *net, struct iphdr *iph, int segs)
{
	u32 hash, id;

	/* Note the following code is not safe, but this is okay. */
	if (unlikely(siphash_key_is_zero(&net->ipv4.ip_id_key)))
		get_random_bytes(&net->ipv4.ip_id_key,
				 sizeof(net->ipv4.ip_id_key));

	hash = siphash_3u32((__force u32)iph->daddr,
			    (__force u32)iph->saddr,
			    iph->protocol,
			    &net->ipv4.ip_id_key);
	id = ip_idents_reserve(hash, segs);
	iph->id = htons(id);
}
EXPORT_SYMBOL(__ip_select_ident);

static void __build_flow_key(const struct net *net, struct flowi4 *fl4,
			     const struct sock *sk, const struct iphdr *iph,
			     int oif, __u8 tos, u8 prot, u32 mark,
			     int flow_flags)
{
	__u8 scope = RT_SCOPE_UNIVERSE;

	if (sk) {
		oif = sk->sk_bound_dev_if;
		mark = READ_ONCE(sk->sk_mark);
		tos = ip_sock_rt_tos(sk);
		scope = ip_sock_rt_scope(sk);
		prot = inet_test_bit(HDRINCL, sk) ? IPPROTO_RAW :
						    sk->sk_protocol;
	}

	flowi4_init_output(fl4, oif, mark, tos & INET_DSCP_MASK, scope,
			   prot, flow_flags, iph->daddr, iph->saddr, 0, 0,
			   sock_net_uid(net, sk));
}

static void build_skb_flow_key(struct flowi4 *fl4, const struct sk_buff *skb,
			       const struct sock *sk)
{
	const struct net *net = dev_net(skb->dev);
	const struct iphdr *iph = ip_hdr(skb);
	int oif = skb->dev->ifindex;
	u8 prot = iph->protocol;
	u32 mark = skb->mark;
	__u8 tos = iph->tos;

	__build_flow_key(net, fl4, sk, iph, oif, tos, prot, mark, 0);
}

static void build_sk_flow_key(struct flowi4 *fl4, const struct sock *sk)
{
	const struct inet_sock *inet = inet_sk(sk);
	const struct ip_options_rcu *inet_opt;
	__be32 daddr = inet->inet_daddr;

	rcu_read_lock();
	inet_opt = rcu_dereference(inet->inet_opt);
	if (inet_opt && inet_opt->opt.srr)
		daddr = inet_opt->opt.faddr;
	flowi4_init_output(fl4, sk->sk_bound_dev_if, READ_ONCE(sk->sk_mark),
			   ip_sock_rt_tos(sk),
			   ip_sock_rt_scope(sk),
			   inet_test_bit(HDRINCL, sk) ?
				IPPROTO_RAW : sk->sk_protocol,
			   inet_sk_flowi_flags(sk),
			   daddr, inet->inet_saddr, 0, 0, sk->sk_uid);
	rcu_read_unlock();
}

static void ip_rt_build_flow_key(struct flowi4 *fl4, const struct sock *sk,
				 const struct sk_buff *skb)
{
	if (skb)
		build_skb_flow_key(fl4, skb, sk);
	else
		build_sk_flow_key(fl4, sk);
}

static DEFINE_SPINLOCK(fnhe_lock);

static void fnhe_flush_routes(struct fib_nh_exception *fnhe)
{
	struct rtable *rt;

	rt = rcu_dereference(fnhe->fnhe_rth_input);
	if (rt) {
		RCU_INIT_POINTER(fnhe->fnhe_rth_input, NULL);
		dst_dev_put(&rt->dst);
		dst_release(&rt->dst);
	}
	rt = rcu_dereference(fnhe->fnhe_rth_output);
	if (rt) {
		RCU_INIT_POINTER(fnhe->fnhe_rth_output, NULL);
		dst_dev_put(&rt->dst);
		dst_release(&rt->dst);
	}
}

static void fnhe_remove_oldest(struct fnhe_hash_bucket *hash)
{
	struct fib_nh_exception __rcu **fnhe_p, **oldest_p;
	struct fib_nh_exception *fnhe, *oldest = NULL;

	for (fnhe_p = &hash->chain; ; fnhe_p = &fnhe->fnhe_next) {
		fnhe = rcu_dereference_protected(*fnhe_p,
						 lockdep_is_held(&fnhe_lock));
		if (!fnhe)
			break;
		if (!oldest ||
		    time_before(fnhe->fnhe_stamp, oldest->fnhe_stamp)) {
			oldest = fnhe;
			oldest_p = fnhe_p;
		}
	}
	fnhe_flush_routes(oldest);
	*oldest_p = oldest->fnhe_next;
	kfree_rcu(oldest, rcu);
}

static u32 fnhe_hashfun(__be32 daddr)
{
	static siphash_aligned_key_t fnhe_hash_key;
	u64 hval;

	net_get_random_once(&fnhe_hash_key, sizeof(fnhe_hash_key));
	hval = siphash_1u32((__force u32)daddr, &fnhe_hash_key);
	return hash_64(hval, FNHE_HASH_SHIFT);
}

static void fill_route_from_fnhe(struct rtable *rt, struct fib_nh_exception *fnhe)
{
	rt->rt_pmtu = fnhe->fnhe_pmtu;
	rt->rt_mtu_locked = fnhe->fnhe_mtu_locked;
	rt->dst.expires = fnhe->fnhe_expires;

	if (fnhe->fnhe_gw) {
		rt->rt_flags |= RTCF_REDIRECTED;
		rt->rt_uses_gateway = 1;
		rt->rt_gw_family = AF_INET;
		rt->rt_gw4 = fnhe->fnhe_gw;
	}
}

static void update_or_create_fnhe(struct fib_nh_common *nhc, __be32 daddr,
				  __be32 gw, u32 pmtu, bool lock,
				  unsigned long expires)
{
	struct fnhe_hash_bucket *hash;
	struct fib_nh_exception *fnhe;
	struct rtable *rt;
	u32 genid, hval;
	unsigned int i;
	int depth;

	genid = fnhe_genid(dev_net(nhc->nhc_dev));
	hval = fnhe_hashfun(daddr);

	spin_lock_bh(&fnhe_lock);

	hash = rcu_dereference(nhc->nhc_exceptions);
	if (!hash) {
		hash = kcalloc(FNHE_HASH_SIZE, sizeof(*hash), GFP_ATOMIC);
		if (!hash)
			goto out_unlock;
		rcu_assign_pointer(nhc->nhc_exceptions, hash);
	}

	hash += hval;

	depth = 0;
	for (fnhe = rcu_dereference(hash->chain); fnhe;
	     fnhe = rcu_dereference(fnhe->fnhe_next)) {
		if (fnhe->fnhe_daddr == daddr)
			break;
		depth++;
	}

	if (fnhe) {
		if (fnhe->fnhe_genid != genid)
			fnhe->fnhe_genid = genid;
		if (gw)
			fnhe->fnhe_gw = gw;
		if (pmtu) {
			fnhe->fnhe_pmtu = pmtu;
			fnhe->fnhe_mtu_locked = lock;
		}
		fnhe->fnhe_expires = max(1UL, expires);
		/* Update all cached dsts too */
		rt = rcu_dereference(fnhe->fnhe_rth_input);
		if (rt)
			fill_route_from_fnhe(rt, fnhe);
		rt = rcu_dereference(fnhe->fnhe_rth_output);
		if (rt)
			fill_route_from_fnhe(rt, fnhe);
	} else {
		/* Randomize max depth to avoid some side channels attacks. */
		int max_depth = FNHE_RECLAIM_DEPTH +
				get_random_u32_below(FNHE_RECLAIM_DEPTH);

		while (depth > max_depth) {
			fnhe_remove_oldest(hash);
			depth--;
		}

		fnhe = kzalloc(sizeof(*fnhe), GFP_ATOMIC);
		if (!fnhe)
			goto out_unlock;

		fnhe->fnhe_next = hash->chain;

		fnhe->fnhe_genid = genid;
		fnhe->fnhe_daddr = daddr;
		fnhe->fnhe_gw = gw;
		fnhe->fnhe_pmtu = pmtu;
		fnhe->fnhe_mtu_locked = lock;
		fnhe->fnhe_expires = max(1UL, expires);

		rcu_assign_pointer(hash->chain, fnhe);

		/* Exception created; mark the cached routes for the nexthop
		 * stale, so anyone caching it rechecks if this exception
		 * applies to them.
		 */
		rt = rcu_dereference(nhc->nhc_rth_input);
		if (rt)
			rt->dst.obsolete = DST_OBSOLETE_KILL;

		for_each_possible_cpu(i) {
			struct rtable __rcu **prt;

			prt = per_cpu_ptr(nhc->nhc_pcpu_rth_output, i);
			rt = rcu_dereference(*prt);
			if (rt)
				rt->dst.obsolete = DST_OBSOLETE_KILL;
		}
	}

	fnhe->fnhe_stamp = jiffies;

out_unlock:
	spin_unlock_bh(&fnhe_lock);
}

static void __ip_do_redirect(struct rtable *rt, struct sk_buff *skb, struct flowi4 *fl4,
			     bool kill_route)
{
	__be32 new_gw = icmp_hdr(skb)->un.gateway;
	__be32 old_gw = ip_hdr(skb)->saddr;
	struct net_device *dev = skb->dev;
	struct in_device *in_dev;
	struct fib_result res;
	struct neighbour *n;
	struct net *net;

	switch (icmp_hdr(skb)->code & 7) {
	case ICMP_REDIR_NET:
	case ICMP_REDIR_NETTOS:
	case ICMP_REDIR_HOST:
	case ICMP_REDIR_HOSTTOS:
		break;

	default:
		return;
	}

	if (rt->rt_gw_family != AF_INET || rt->rt_gw4 != old_gw)
		return;

	in_dev = __in_dev_get_rcu(dev);
	if (!in_dev)
		return;

	net = dev_net(dev);
	if (new_gw == old_gw || !IN_DEV_RX_REDIRECTS(in_dev) ||
	    ipv4_is_multicast(new_gw) || ipv4_is_lbcast(new_gw) ||
	    ipv4_is_zeronet(new_gw))
		goto reject_redirect;

	if (!IN_DEV_SHARED_MEDIA(in_dev)) {
		if (!inet_addr_onlink(in_dev, new_gw, old_gw))
			goto reject_redirect;
		if (IN_DEV_SEC_REDIRECTS(in_dev) && ip_fib_check_default(new_gw, dev))
			goto reject_redirect;
	} else {
		if (inet_addr_type(net, new_gw) != RTN_UNICAST)
			goto reject_redirect;
	}

	n = __ipv4_neigh_lookup(rt->dst.dev, (__force u32)new_gw);
	if (!n)
		n = neigh_create(&arp_tbl, &new_gw, rt->dst.dev);
	if (!IS_ERR(n)) {
		if (!(READ_ONCE(n->nud_state) & NUD_VALID)) {
			neigh_event_send(n, NULL);
		} else {
			if (fib_lookup(net, fl4, &res, 0) == 0) {
				struct fib_nh_common *nhc;

				fib_select_path(net, &res, fl4, skb);
				nhc = FIB_RES_NHC(res);
				update_or_create_fnhe(nhc, fl4->daddr, new_gw,
						0, false,
						jiffies + ip_rt_gc_timeout);
			}
			if (kill_route)
				rt->dst.obsolete = DST_OBSOLETE_KILL;
			call_netevent_notifiers(NETEVENT_NEIGH_UPDATE, n);
		}
		neigh_release(n);
	}
	return;

reject_redirect:
#ifdef CONFIG_IP_ROUTE_VERBOSE
	if (IN_DEV_LOG_MARTIANS(in_dev)) {
		const struct iphdr *iph = (const struct iphdr *) skb->data;
		__be32 daddr = iph->daddr;
		__be32 saddr = iph->saddr;

		net_info_ratelimited("Redirect from %pI4 on %s about %pI4 ignored\n"
				     "  Advised path = %pI4 -> %pI4\n",
				     &old_gw, dev->name, &new_gw,
				     &saddr, &daddr);
	}
#endif
	;
}

static void ip_do_redirect(struct dst_entry *dst, struct sock *sk, struct sk_buff *skb)
{
	struct rtable *rt;
	struct flowi4 fl4;
	const struct iphdr *iph = (const struct iphdr *) skb->data;
	struct net *net = dev_net(skb->dev);
	int oif = skb->dev->ifindex;
	u8 prot = iph->protocol;
	u32 mark = skb->mark;
	__u8 tos = iph->tos;

	rt = dst_rtable(dst);

	__build_flow_key(net, &fl4, sk, iph, oif, tos, prot, mark, 0);
	__ip_do_redirect(rt, skb, &fl4, true);
}

static void ipv4_negative_advice(struct sock *sk,
				 struct dst_entry *dst)
{
	struct rtable *rt = dst_rtable(dst);

	if ((dst->obsolete > 0) ||
	    (rt->rt_flags & RTCF_REDIRECTED) ||
	    rt->dst.expires)
		sk_dst_reset(sk);
}

/*
 * Algorithm:
 *	1. The first ip_rt_redirect_number redirects are sent
 *	   with exponential backoff, then we stop sending them at all,
 *	   assuming that the host ignores our redirects.
 *	2. If we did not see packets requiring redirects
 *	   during ip_rt_redirect_silence, we assume that the host
 *	   forgot redirected route and start to send redirects again.
 *
 * This algorithm is much cheaper and more intelligent than dumb load limiting
 * in icmp.c.
 *
 * NOTE. Do not forget to inhibit load limiting for redirects (redundant)
 * and "frag. need" (breaks PMTU discovery) in icmp.c.
 */

void ip_rt_send_redirect(struct sk_buff *skb)
{
	struct rtable *rt = skb_rtable(skb);
	struct in_device *in_dev;
	struct inet_peer *peer;
	struct net *net;
	int log_martians;
	int vif;

	rcu_read_lock();
	in_dev = __in_dev_get_rcu(rt->dst.dev);
	if (!in_dev || !IN_DEV_TX_REDIRECTS(in_dev)) {
		rcu_read_unlock();
		return;
	}
	log_martians = IN_DEV_LOG_MARTIANS(in_dev);
	vif = l3mdev_master_ifindex_rcu(rt->dst.dev);
	rcu_read_unlock();

	net = dev_net(rt->dst.dev);
	peer = inet_getpeer_v4(net->ipv4.peers, ip_hdr(skb)->saddr, vif, 1);
	if (!peer) {
		icmp_send(skb, ICMP_REDIRECT, ICMP_REDIR_HOST,
			  rt_nexthop(rt, ip_hdr(skb)->daddr));
		return;
	}

	/* No redirected packets during ip_rt_redirect_silence;
	 * reset the algorithm.
	 */
	if (time_after(jiffies, peer->rate_last + ip_rt_redirect_silence)) {
		peer->rate_tokens = 0;
		peer->n_redirects = 0;
	}

	/* Too many ignored redirects; do not send anything
	 * set dst.rate_last to the last seen redirected packet.
	 */
	if (peer->n_redirects >= ip_rt_redirect_number) {
		peer->rate_last = jiffies;
		goto out_put_peer;
	}

	/* Check for load limit; set rate_last to the latest sent
	 * redirect.
	 */
	if (peer->n_redirects == 0 ||
	    time_after(jiffies,
		       (peer->rate_last +
			(ip_rt_redirect_load << peer->n_redirects)))) {
		__be32 gw = rt_nexthop(rt, ip_hdr(skb)->daddr);

		icmp_send(skb, ICMP_REDIRECT, ICMP_REDIR_HOST, gw);
		peer->rate_last = jiffies;
		++peer->n_redirects;
		if (IS_ENABLED(CONFIG_IP_ROUTE_VERBOSE) && log_martians &&
		    peer->n_redirects == ip_rt_redirect_number)
			net_warn_ratelimited("host %pI4/if%d ignores redirects for %pI4 to %pI4\n",
					     &ip_hdr(skb)->saddr, inet_iif(skb),
					     &ip_hdr(skb)->daddr, &gw);
	}
out_put_peer:
	inet_putpeer(peer);
}

static int ip_error(struct sk_buff *skb)
{
	struct rtable *rt = skb_rtable(skb);
	struct net_device *dev = skb->dev;
	struct in_device *in_dev;
	struct inet_peer *peer;
	unsigned long now;
	struct net *net;
	SKB_DR(reason);
	bool send;
	int code;

	if (netif_is_l3_master(skb->dev)) {
		dev = __dev_get_by_index(dev_net(skb->dev), IPCB(skb)->iif);
		if (!dev)
			goto out;
	}

	in_dev = __in_dev_get_rcu(dev);

	/* IP on this device is disabled. */
	if (!in_dev)
		goto out;

	net = dev_net(rt->dst.dev);
	if (!IN_DEV_FORWARD(in_dev)) {
		switch (rt->dst.error) {
		case EHOSTUNREACH:
			SKB_DR_SET(reason, IP_INADDRERRORS);
			__IP_INC_STATS(net, IPSTATS_MIB_INADDRERRORS);
			break;

		case ENETUNREACH:
			SKB_DR_SET(reason, IP_INNOROUTES);
			__IP_INC_STATS(net, IPSTATS_MIB_INNOROUTES);
			break;
		}
		goto out;
	}

	switch (rt->dst.error) {
	case EINVAL:
	default:
		goto out;
	case EHOSTUNREACH:
		code = ICMP_HOST_UNREACH;
		break;
	case ENETUNREACH:
		code = ICMP_NET_UNREACH;
		SKB_DR_SET(reason, IP_INNOROUTES);
		__IP_INC_STATS(net, IPSTATS_MIB_INNOROUTES);
		break;
	case EACCES:
		code = ICMP_PKT_FILTERED;
		break;
	}

	peer = inet_getpeer_v4(net->ipv4.peers, ip_hdr(skb)->saddr,
			       l3mdev_master_ifindex(skb->dev), 1);

	send = true;
	if (peer) {
		now = jiffies;
		peer->rate_tokens += now - peer->rate_last;
		if (peer->rate_tokens > ip_rt_error_burst)
			peer->rate_tokens = ip_rt_error_burst;
		peer->rate_last = now;
		if (peer->rate_tokens >= ip_rt_error_cost)
			peer->rate_tokens -= ip_rt_error_cost;
		else
			send = false;
		inet_putpeer(peer);
	}
	if (send)
		icmp_send(skb, ICMP_DEST_UNREACH, code, 0);

out:	kfree_skb_reason(skb, reason);
	return 0;
}

static void __ip_rt_update_pmtu(struct rtable *rt, struct flowi4 *fl4, u32 mtu)
{
	struct dst_entry *dst = &rt->dst;
	struct net *net = dev_net(dst->dev);
	struct fib_result res;
	bool lock = false;
	u32 old_mtu;

	if (ip_mtu_locked(dst))
		return;

	old_mtu = ipv4_mtu(dst);
	if (old_mtu < mtu)
		return;

	if (mtu < net->ipv4.ip_rt_min_pmtu) {
		lock = true;
		mtu = min(old_mtu, net->ipv4.ip_rt_min_pmtu);
	}

	if (rt->rt_pmtu == mtu && !lock &&
	    time_before(jiffies, dst->expires - net->ipv4.ip_rt_mtu_expires / 2))
		return;

	rcu_read_lock();
	if (fib_lookup(net, fl4, &res, 0) == 0) {
		struct fib_nh_common *nhc;

		fib_select_path(net, &res, fl4, NULL);
#ifdef CONFIG_IP_ROUTE_MULTIPATH
		if (fib_info_num_path(res.fi) > 1) {
			int nhsel;

			for (nhsel = 0; nhsel < fib_info_num_path(res.fi); nhsel++) {
				nhc = fib_info_nhc(res.fi, nhsel);
				update_or_create_fnhe(nhc, fl4->daddr, 0, mtu, lock,
						      jiffies + net->ipv4.ip_rt_mtu_expires);
			}
			rcu_read_unlock();
			return;
		}
#endif /* CONFIG_IP_ROUTE_MULTIPATH */
		nhc = FIB_RES_NHC(res);
		update_or_create_fnhe(nhc, fl4->daddr, 0, mtu, lock,
				      jiffies + net->ipv4.ip_rt_mtu_expires);
	}
	rcu_read_unlock();
}

static void ip_rt_update_pmtu(struct dst_entry *dst, struct sock *sk,
			      struct sk_buff *skb, u32 mtu,
			      bool confirm_neigh)
{
	struct rtable *rt = dst_rtable(dst);
	struct flowi4 fl4;

	ip_rt_build_flow_key(&fl4, sk, skb);

	/* Don't make lookup fail for bridged encapsulations */
	if (skb && netif_is_any_bridge_port(skb->dev))
		fl4.flowi4_oif = 0;

	__ip_rt_update_pmtu(rt, &fl4, mtu);
}

void ipv4_update_pmtu(struct sk_buff *skb, struct net *net, u32 mtu,
		      int oif, u8 protocol)
{
	const struct iphdr *iph = (const struct iphdr *)skb->data;
	struct flowi4 fl4;
	struct rtable *rt;
	u32 mark = IP4_REPLY_MARK(net, skb->mark);

	__build_flow_key(net, &fl4, NULL, iph, oif, iph->tos, protocol, mark,
			 0);
	rt = __ip_route_output_key(net, &fl4);
	if (!IS_ERR(rt)) {
		__ip_rt_update_pmtu(rt, &fl4, mtu);
		ip_rt_put(rt);
	}
}
EXPORT_SYMBOL_GPL(ipv4_update_pmtu);

static void __ipv4_sk_update_pmtu(struct sk_buff *skb, struct sock *sk, u32 mtu)
{
	const struct iphdr *iph = (const struct iphdr *)skb->data;
	struct flowi4 fl4;
	struct rtable *rt;

	__build_flow_key(sock_net(sk), &fl4, sk, iph, 0, 0, 0, 0, 0);

	if (!fl4.flowi4_mark)
		fl4.flowi4_mark = IP4_REPLY_MARK(sock_net(sk), skb->mark);

	rt = __ip_route_output_key(sock_net(sk), &fl4);
	if (!IS_ERR(rt)) {
		__ip_rt_update_pmtu(rt, &fl4, mtu);
		ip_rt_put(rt);
	}
}

void ipv4_sk_update_pmtu(struct sk_buff *skb, struct sock *sk, u32 mtu)
{
	const struct iphdr *iph = (const struct iphdr *)skb->data;
	struct flowi4 fl4;
	struct rtable *rt;
	struct dst_entry *odst = NULL;
	bool new = false;
	struct net *net = sock_net(sk);

	bh_lock_sock(sk);

	if (!ip_sk_accept_pmtu(sk))
		goto out;

	odst = sk_dst_get(sk);

	if (sock_owned_by_user(sk) || !odst) {
		__ipv4_sk_update_pmtu(skb, sk, mtu);
		goto out;
	}

	__build_flow_key(net, &fl4, sk, iph, 0, 0, 0, 0, 0);

	rt = dst_rtable(odst);
	if (odst->obsolete && !odst->ops->check(odst, 0)) {
		rt = ip_route_output_flow(sock_net(sk), &fl4, sk);
		if (IS_ERR(rt))
			goto out;

		new = true;
	}

	__ip_rt_update_pmtu(dst_rtable(xfrm_dst_path(&rt->dst)), &fl4, mtu);

	if (!dst_check(&rt->dst, 0)) {
		if (new)
			dst_release(&rt->dst);

		rt = ip_route_output_flow(sock_net(sk), &fl4, sk);
		if (IS_ERR(rt))
			goto out;

		new = true;
	}

	if (new)
		sk_dst_set(sk, &rt->dst);

out:
	bh_unlock_sock(sk);
	dst_release(odst);
}
EXPORT_SYMBOL_GPL(ipv4_sk_update_pmtu);

void ipv4_redirect(struct sk_buff *skb, struct net *net,
		   int oif, u8 protocol)
{
	const struct iphdr *iph = (const struct iphdr *)skb->data;
	struct flowi4 fl4;
	struct rtable *rt;

	__build_flow_key(net, &fl4, NULL, iph, oif, iph->tos, protocol, 0, 0);
	rt = __ip_route_output_key(net, &fl4);
	if (!IS_ERR(rt)) {
		__ip_do_redirect(rt, skb, &fl4, false);
		ip_rt_put(rt);
	}
}
EXPORT_SYMBOL_GPL(ipv4_redirect);

void ipv4_sk_redirect(struct sk_buff *skb, struct sock *sk)
{
	const struct iphdr *iph = (const struct iphdr *)skb->data;
	struct flowi4 fl4;
	struct rtable *rt;
	struct net *net = sock_net(sk);

	__build_flow_key(net, &fl4, sk, iph, 0, 0, 0, 0, 0);
	rt = __ip_route_output_key(net, &fl4);
	if (!IS_ERR(rt)) {
		__ip_do_redirect(rt, skb, &fl4, false);
		ip_rt_put(rt);
	}
}
EXPORT_SYMBOL_GPL(ipv4_sk_redirect);

INDIRECT_CALLABLE_SCOPE struct dst_entry *ipv4_dst_check(struct dst_entry *dst,
							 u32 cookie)
{
	struct rtable *rt = dst_rtable(dst);

	/* All IPV4 dsts are created with ->obsolete set to the value
	 * DST_OBSOLETE_FORCE_CHK which forces validation calls down
	 * into this function always.
	 *
	 * When a PMTU/redirect information update invalidates a route,
	 * this is indicated by setting obsolete to DST_OBSOLETE_KILL or
	 * DST_OBSOLETE_DEAD.
	 */
	if (dst->obsolete != DST_OBSOLETE_FORCE_CHK || rt_is_expired(rt))
		return NULL;
	return dst;
}
EXPORT_INDIRECT_CALLABLE(ipv4_dst_check);

static void ipv4_send_dest_unreach(struct sk_buff *skb)
{
	struct net_device *dev;
	struct ip_options opt;
	int res;

	/* Recompile ip options since IPCB may not be valid anymore.
	 * Also check we have a reasonable ipv4 header.
	 */
	if (!pskb_network_may_pull(skb, sizeof(struct iphdr)) ||
	    ip_hdr(skb)->version != 4 || ip_hdr(skb)->ihl < 5)
		return;

	memset(&opt, 0, sizeof(opt));
	if (ip_hdr(skb)->ihl > 5) {
		if (!pskb_network_may_pull(skb, ip_hdr(skb)->ihl * 4))
			return;
		opt.optlen = ip_hdr(skb)->ihl * 4 - sizeof(struct iphdr);

		rcu_read_lock();
		dev = skb->dev ? skb->dev : skb_rtable(skb)->dst.dev;
		res = __ip_options_compile(dev_net(dev), &opt, skb, NULL);
		rcu_read_unlock();

		if (res)
			return;
	}
	__icmp_send(skb, ICMP_DEST_UNREACH, ICMP_HOST_UNREACH, 0, &opt);
}

static void ipv4_link_failure(struct sk_buff *skb)
{
	struct rtable *rt;

	ipv4_send_dest_unreach(skb);

	rt = skb_rtable(skb);
	if (rt)
		dst_set_expires(&rt->dst, 0);
}

static int ip_rt_bug(struct net *net, struct sock *sk, struct sk_buff *skb)
{
	pr_debug("%s: %pI4 -> %pI4, %s\n",
		 __func__, &ip_hdr(skb)->saddr, &ip_hdr(skb)->daddr,
		 skb->dev ? skb->dev->name : "?");
	kfree_skb(skb);
	WARN_ON(1);
	return 0;
}

/*
 * We do not cache source address of outgoing interface,
 * because it is used only by IP RR, TS and SRR options,
 * so that it out of fast path.
 *
 * BTW remember: "addr" is allowed to be not aligned
 * in IP options!
 */

void ip_rt_get_source(u8 *addr, struct sk_buff *skb, struct rtable *rt)
{
	__be32 src;

	if (rt_is_output_route(rt))
		src = ip_hdr(skb)->saddr;
	else {
		struct fib_result res;
		struct iphdr *iph = ip_hdr(skb);
		struct flowi4 fl4 = {
			.daddr = iph->daddr,
			.saddr = iph->saddr,
			.flowi4_tos = inet_dscp_to_dsfield(ip4h_dscp(iph)),
			.flowi4_oif = rt->dst.dev->ifindex,
			.flowi4_iif = skb->dev->ifindex,
			.flowi4_mark = skb->mark,
		};

		rcu_read_lock();
		if (fib_lookup(dev_net(rt->dst.dev), &fl4, &res, 0) == 0)
			src = fib_result_prefsrc(dev_net(rt->dst.dev), &res);
		else
			src = inet_select_addr(rt->dst.dev,
					       rt_nexthop(rt, iph->daddr),
					       RT_SCOPE_UNIVERSE);
		rcu_read_unlock();
	}
	memcpy(addr, &src, 4);
}

#ifdef CONFIG_IP_ROUTE_CLASSID
static void set_class_tag(struct rtable *rt, u32 tag)
{
	if (!(rt->dst.tclassid & 0xFFFF))
		rt->dst.tclassid |= tag & 0xFFFF;
	if (!(rt->dst.tclassid & 0xFFFF0000))
		rt->dst.tclassid |= tag & 0xFFFF0000;
}
#endif

static unsigned int ipv4_default_advmss(const struct dst_entry *dst)
{
	struct net *net = dev_net(dst->dev);
	unsigned int header_size = sizeof(struct tcphdr) + sizeof(struct iphdr);
	unsigned int advmss = max_t(unsigned int, ipv4_mtu(dst) - header_size,
				    net->ipv4.ip_rt_min_advmss);

	return min(advmss, IPV4_MAX_PMTU - header_size);
}

INDIRECT_CALLABLE_SCOPE unsigned int ipv4_mtu(const struct dst_entry *dst)
{
	return ip_dst_mtu_maybe_forward(dst, false);
}
EXPORT_INDIRECT_CALLABLE(ipv4_mtu);

static void ip_del_fnhe(struct fib_nh_common *nhc, __be32 daddr)
{
	struct fnhe_hash_bucket *hash;
	struct fib_nh_exception *fnhe, __rcu **fnhe_p;
	u32 hval = fnhe_hashfun(daddr);

	spin_lock_bh(&fnhe_lock);

	hash = rcu_dereference_protected(nhc->nhc_exceptions,
					 lockdep_is_held(&fnhe_lock));
	hash += hval;

	fnhe_p = &hash->chain;
	fnhe = rcu_dereference_protected(*fnhe_p, lockdep_is_held(&fnhe_lock));
	while (fnhe) {
		if (fnhe->fnhe_daddr == daddr) {
			rcu_assign_pointer(*fnhe_p, rcu_dereference_protected(
				fnhe->fnhe_next, lockdep_is_held(&fnhe_lock)));
			/* set fnhe_daddr to 0 to ensure it won't bind with
			 * new dsts in rt_bind_exception().
			 */
			fnhe->fnhe_daddr = 0;
			fnhe_flush_routes(fnhe);
			kfree_rcu(fnhe, rcu);
			break;
		}
		fnhe_p = &fnhe->fnhe_next;
		fnhe = rcu_dereference_protected(fnhe->fnhe_next,
						 lockdep_is_held(&fnhe_lock));
	}

	spin_unlock_bh(&fnhe_lock);
}

static struct fib_nh_exception *find_exception(struct fib_nh_common *nhc,
					       __be32 daddr)
{
	struct fnhe_hash_bucket *hash = rcu_dereference(nhc->nhc_exceptions);
	struct fib_nh_exception *fnhe;
	u32 hval;

	if (!hash)
		return NULL;

	hval = fnhe_hashfun(daddr);

	for (fnhe = rcu_dereference(hash[hval].chain); fnhe;
	     fnhe = rcu_dereference(fnhe->fnhe_next)) {
		if (fnhe->fnhe_daddr == daddr) {
			if (fnhe->fnhe_expires &&
			    time_after(jiffies, fnhe->fnhe_expires)) {
				ip_del_fnhe(nhc, daddr);
				break;
			}
			return fnhe;
		}
	}
	return NULL;
}

/* MTU selection:
 * 1. mtu on route is locked - use it
 * 2. mtu from nexthop exception
 * 3. mtu from egress device
 */

u32 ip_mtu_from_fib_result(struct fib_result *res, __be32 daddr)
{
	struct fib_nh_common *nhc = res->nhc;
	struct net_device *dev = nhc->nhc_dev;
	struct fib_info *fi = res->fi;
	u32 mtu = 0;

	if (READ_ONCE(dev_net(dev)->ipv4.sysctl_ip_fwd_use_pmtu) ||
	    fi->fib_metrics->metrics[RTAX_LOCK - 1] & (1 << RTAX_MTU))
		mtu = fi->fib_mtu;

	if (likely(!mtu)) {
		struct fib_nh_exception *fnhe;

		fnhe = find_exception(nhc, daddr);
		if (fnhe && !time_after_eq(jiffies, fnhe->fnhe_expires))
			mtu = fnhe->fnhe_pmtu;
	}

	if (likely(!mtu))
		mtu = min(READ_ONCE(dev->mtu), IP_MAX_MTU);

	return mtu - lwtunnel_headroom(nhc->nhc_lwtstate, mtu);
}

static bool rt_bind_exception(struct rtable *rt, struct fib_nh_exception *fnhe,
			      __be32 daddr, const bool do_cache)
{
	bool ret = false;

	spin_lock_bh(&fnhe_lock);

	if (daddr == fnhe->fnhe_daddr) {
		struct rtable __rcu **porig;
		struct rtable *orig;
		int genid = fnhe_genid(dev_net(rt->dst.dev));

		if (rt_is_input_route(rt))
			porig = &fnhe->fnhe_rth_input;
		else
			porig = &fnhe->fnhe_rth_output;
		orig = rcu_dereference(*porig);

		if (fnhe->fnhe_genid != genid) {
			fnhe->fnhe_genid = genid;
			fnhe->fnhe_gw = 0;
			fnhe->fnhe_pmtu = 0;
			fnhe->fnhe_expires = 0;
			fnhe->fnhe_mtu_locked = false;
			fnhe_flush_routes(fnhe);
			orig = NULL;
		}
		fill_route_from_fnhe(rt, fnhe);
		if (!rt->rt_gw4) {
			rt->rt_gw4 = daddr;
			rt->rt_gw_family = AF_INET;
		}

		if (do_cache) {
			dst_hold(&rt->dst);
			rcu_assign_pointer(*porig, rt);
			if (orig) {
				dst_dev_put(&orig->dst);
				dst_release(&orig->dst);
			}
			ret = true;
		}

		fnhe->fnhe_stamp = jiffies;
	}
	spin_unlock_bh(&fnhe_lock);

	return ret;
}

static bool rt_cache_route(struct fib_nh_common *nhc, struct rtable *rt)
{
	struct rtable *orig, *prev, **p;
	bool ret = true;

	if (rt_is_input_route(rt)) {
		p = (struct rtable **)&nhc->nhc_rth_input;
	} else {
		p = (struct rtable **)raw_cpu_ptr(nhc->nhc_pcpu_rth_output);
	}
	orig = *p;

	/* hold dst before doing cmpxchg() to avoid race condition
	 * on this dst
	 */
	dst_hold(&rt->dst);
	prev = cmpxchg(p, orig, rt);
	if (prev == orig) {
		if (orig) {
			rt_add_uncached_list(orig);
			dst_release(&orig->dst);
		}
	} else {
		dst_release(&rt->dst);
		ret = false;
	}

	return ret;
}

struct uncached_list {
	spinlock_t		lock;
	struct list_head	head;
};

static DEFINE_PER_CPU_ALIGNED(struct uncached_list, rt_uncached_list);

void rt_add_uncached_list(struct rtable *rt)
{
	struct uncached_list *ul = raw_cpu_ptr(&rt_uncached_list);

	rt->dst.rt_uncached_list = ul;

	spin_lock_bh(&ul->lock);
	list_add_tail(&rt->dst.rt_uncached, &ul->head);
	spin_unlock_bh(&ul->lock);
}

void rt_del_uncached_list(struct rtable *rt)
{
	if (!list_empty(&rt->dst.rt_uncached)) {
		struct uncached_list *ul = rt->dst.rt_uncached_list;

		spin_lock_bh(&ul->lock);
		list_del_init(&rt->dst.rt_uncached);
		spin_unlock_bh(&ul->lock);
	}
}

static void ipv4_dst_destroy(struct dst_entry *dst)
{
	ip_dst_metrics_put(dst);
	rt_del_uncached_list(dst_rtable(dst));
}

void rt_flush_dev(struct net_device *dev)
{
	struct rtable *rt, *safe;
	int cpu;

	for_each_possible_cpu(cpu) {
		struct uncached_list *ul = &per_cpu(rt_uncached_list, cpu);

		if (list_empty(&ul->head))
			continue;

		spin_lock_bh(&ul->lock);
		list_for_each_entry_safe(rt, safe, &ul->head, dst.rt_uncached) {
			if (rt->dst.dev != dev)
				continue;
			rt->dst.dev = blackhole_netdev;
			netdev_ref_replace(dev, blackhole_netdev,
					   &rt->dst.dev_tracker, GFP_ATOMIC);
			list_del_init(&rt->dst.rt_uncached);
		}
		spin_unlock_bh(&ul->lock);
	}
}

static bool rt_cache_valid(const struct rtable *rt)
{
	return	rt &&
		rt->dst.obsolete == DST_OBSOLETE_FORCE_CHK &&
		!rt_is_expired(rt);
}

static void rt_set_nexthop(struct rtable *rt, __be32 daddr,
			   const struct fib_result *res,
			   struct fib_nh_exception *fnhe,
			   struct fib_info *fi, u16 type, u32 itag,
			   const bool do_cache)
{
	bool cached = false;

	if (fi) {
		struct fib_nh_common *nhc = FIB_RES_NHC(*res);

		if (nhc->nhc_gw_family && nhc->nhc_scope == RT_SCOPE_LINK) {
			rt->rt_uses_gateway = 1;
			rt->rt_gw_family = nhc->nhc_gw_family;
			/* only INET and INET6 are supported */
			if (likely(nhc->nhc_gw_family == AF_INET))
				rt->rt_gw4 = nhc->nhc_gw.ipv4;
			else
				rt->rt_gw6 = nhc->nhc_gw.ipv6;
		}

		ip_dst_init_metrics(&rt->dst, fi->fib_metrics);

#ifdef CONFIG_IP_ROUTE_CLASSID
		if (nhc->nhc_family == AF_INET) {
			struct fib_nh *nh;

			nh = container_of(nhc, struct fib_nh, nh_common);
			rt->dst.tclassid = nh->nh_tclassid;
		}
#endif
		rt->dst.lwtstate = lwtstate_get(nhc->nhc_lwtstate);
		if (unlikely(fnhe))
			cached = rt_bind_exception(rt, fnhe, daddr, do_cache);
		else if (do_cache)
			cached = rt_cache_route(nhc, rt);
		if (unlikely(!cached)) {
			/* Routes we intend to cache in nexthop exception or
			 * FIB nexthop have the DST_NOCACHE bit clear.
			 * However, if we are unsuccessful at storing this
			 * route into the cache we really need to set it.
			 */
			if (!rt->rt_gw4) {
				rt->rt_gw_family = AF_INET;
				rt->rt_gw4 = daddr;
			}
			rt_add_uncached_list(rt);
		}
	} else
		rt_add_uncached_list(rt);

#ifdef CONFIG_IP_ROUTE_CLASSID
#ifdef CONFIG_IP_MULTIPLE_TABLES
	set_class_tag(rt, res->tclassid);
#endif
	set_class_tag(rt, itag);
#endif
}

struct rtable *rt_dst_alloc(struct net_device *dev,
			    unsigned int flags, u16 type,
			    bool noxfrm)
{
	struct rtable *rt;

	rt = dst_alloc(&ipv4_dst_ops, dev, DST_OBSOLETE_FORCE_CHK,
		       (noxfrm ? DST_NOXFRM : 0));

	if (rt) {
		rt->rt_genid = rt_genid_ipv4(dev_net(dev));
		rt->rt_flags = flags;
		rt->rt_type = type;
		rt->rt_is_input = 0;
		rt->rt_iif = 0;
		rt->rt_pmtu = 0;
		rt->rt_mtu_locked = 0;
		rt->rt_uses_gateway = 0;
		rt->rt_gw_family = 0;
		rt->rt_gw4 = 0;

		rt->dst.output = ip_output;
		if (flags & RTCF_LOCAL)
			rt->dst.input = ip_local_deliver;
	}

	return rt;
}
EXPORT_SYMBOL(rt_dst_alloc);

struct rtable *rt_dst_clone(struct net_device *dev, struct rtable *rt)
{
	struct rtable *new_rt;

	new_rt = dst_alloc(&ipv4_dst_ops, dev, DST_OBSOLETE_FORCE_CHK,
			   rt->dst.flags);

	if (new_rt) {
		new_rt->rt_genid = rt_genid_ipv4(dev_net(dev));
		new_rt->rt_flags = rt->rt_flags;
		new_rt->rt_type = rt->rt_type;
		new_rt->rt_is_input = rt->rt_is_input;
		new_rt->rt_iif = rt->rt_iif;
		new_rt->rt_pmtu = rt->rt_pmtu;
		new_rt->rt_mtu_locked = rt->rt_mtu_locked;
		new_rt->rt_gw_family = rt->rt_gw_family;
		if (rt->rt_gw_family == AF_INET)
			new_rt->rt_gw4 = rt->rt_gw4;
		else if (rt->rt_gw_family == AF_INET6)
			new_rt->rt_gw6 = rt->rt_gw6;

		new_rt->dst.input = rt->dst.input;
		new_rt->dst.output = rt->dst.output;
		new_rt->dst.error = rt->dst.error;
		new_rt->dst.lastuse = jiffies;
		new_rt->dst.lwtstate = lwtstate_get(rt->dst.lwtstate);
	}
	return new_rt;
}
EXPORT_SYMBOL(rt_dst_clone);

/* called in rcu_read_lock() section */
enum skb_drop_reason
ip_mc_validate_source(struct sk_buff *skb, __be32 daddr, __be32 saddr,
		      dscp_t dscp, struct net_device *dev,
		      struct in_device *in_dev, u32 *itag)
{
	enum skb_drop_reason reason;

	/* Primary sanity checks. */
	if (!in_dev)
		return SKB_DROP_REASON_NOT_SPECIFIED;

	if (ipv4_is_multicast(saddr) || ipv4_is_lbcast(saddr))
		return SKB_DROP_REASON_IP_INVALID_SOURCE;

	if (skb->protocol != htons(ETH_P_IP))
		return SKB_DROP_REASON_INVALID_PROTO;

	if (ipv4_is_loopback(saddr) && !IN_DEV_ROUTE_LOCALNET(in_dev))
		return SKB_DROP_REASON_IP_LOCALNET;

	if (ipv4_is_zeronet(saddr)) {
		if (!ipv4_is_local_multicast(daddr) &&
		    ip_hdr(skb)->protocol != IPPROTO_IGMP)
			return SKB_DROP_REASON_IP_INVALID_SOURCE;
	} else {
		reason = fib_validate_source_reason(skb, saddr, 0, dscp, 0,
						    dev, in_dev, itag);
		if (reason)
			return reason;
	}
	return SKB_NOT_DROPPED_YET;
}

/* called in rcu_read_lock() section */
static enum skb_drop_reason
ip_route_input_mc(struct sk_buff *skb, __be32 daddr, __be32 saddr,
		  dscp_t dscp, struct net_device *dev, int our)
{
	struct in_device *in_dev = __in_dev_get_rcu(dev);
	unsigned int flags = RTCF_MULTICAST;
	enum skb_drop_reason reason;
	struct rtable *rth;
	u32 itag = 0;

	reason = ip_mc_validate_source(skb, daddr, saddr, dscp, dev, in_dev,
				       &itag);
	if (reason)
		return reason;

	if (our)
		flags |= RTCF_LOCAL;

	if (IN_DEV_ORCONF(in_dev, NOPOLICY))
		IPCB(skb)->flags |= IPSKB_NOPOLICY;

	rth = rt_dst_alloc(dev_net(dev)->loopback_dev, flags, RTN_MULTICAST,
			   false);
	if (!rth)
		return SKB_DROP_REASON_NOMEM;

#ifdef CONFIG_IP_ROUTE_CLASSID
	rth->dst.tclassid = itag;
#endif
	rth->dst.output = ip_rt_bug;
	rth->rt_is_input= 1;

#ifdef CONFIG_IP_MROUTE
	if (!ipv4_is_local_multicast(daddr) && IN_DEV_MFORWARD(in_dev))
		rth->dst.input = ip_mr_input;
#endif
	RT_CACHE_STAT_INC(in_slow_mc);

	skb_dst_drop(skb);
	skb_dst_set(skb, &rth->dst);
	return SKB_NOT_DROPPED_YET;
}


static void ip_handle_martian_source(struct net_device *dev,
				     struct in_device *in_dev,
				     struct sk_buff *skb,
				     __be32 daddr,
				     __be32 saddr)
{
	RT_CACHE_STAT_INC(in_martian_src);
#ifdef CONFIG_IP_ROUTE_VERBOSE
	if (IN_DEV_LOG_MARTIANS(in_dev) && net_ratelimit()) {
		/*
		 *	RFC1812 recommendation, if source is martian,
		 *	the only hint is MAC header.
		 */
		pr_warn("martian source %pI4 from %pI4, on dev %s\n",
			&daddr, &saddr, dev->name);
		if (dev->hard_header_len && skb_mac_header_was_set(skb)) {
			print_hex_dump(KERN_WARNING, "ll header: ",
				       DUMP_PREFIX_OFFSET, 16, 1,
				       skb_mac_header(skb),
				       dev->hard_header_len, false);
		}
	}
#endif
}

/* called in rcu_read_lock() section */
static enum skb_drop_reason
__mkroute_input(struct sk_buff *skb, const struct fib_result *res,
		struct in_device *in_dev, __be32 daddr,
		__be32 saddr, dscp_t dscp)
{
	enum skb_drop_reason reason = SKB_DROP_REASON_NOT_SPECIFIED;
	struct fib_nh_common *nhc = FIB_RES_NHC(*res);
	struct net_device *dev = nhc->nhc_dev;
	struct fib_nh_exception *fnhe;
	struct rtable *rth;
	int err;
	struct in_device *out_dev;
	bool do_cache;
	u32 itag = 0;

	/* get a working reference to the output device */
	out_dev = __in_dev_get_rcu(dev);
	if (!out_dev) {
		net_crit_ratelimited("Bug in ip_route_input_slow(). Please report.\n");
		return reason;
	}

	err = fib_validate_source(skb, saddr, daddr, dscp, FIB_RES_OIF(*res),
				  in_dev->dev, in_dev, &itag);
	if (err < 0) {
		reason = -err;
		ip_handle_martian_source(in_dev->dev, in_dev, skb, daddr,
					 saddr);

		goto cleanup;
	}

	do_cache = res->fi && !itag;
	if (out_dev == in_dev && err && IN_DEV_TX_REDIRECTS(out_dev) &&
	    skb->protocol == htons(ETH_P_IP)) {
		__be32 gw;

		gw = nhc->nhc_gw_family == AF_INET ? nhc->nhc_gw.ipv4 : 0;
		if (IN_DEV_SHARED_MEDIA(out_dev) ||
		    inet_addr_onlink(out_dev, saddr, gw))
			IPCB(skb)->flags |= IPSKB_DOREDIRECT;
	}

	if (skb->protocol != htons(ETH_P_IP)) {
		/* Not IP (i.e. ARP). Do not create route, if it is
		 * invalid for proxy arp. DNAT routes are always valid.
		 *
		 * Proxy arp feature have been extended to allow, ARP
		 * replies back to the same interface, to support
		 * Private VLAN switch technologies. See arp.c.
		 */
		if (out_dev == in_dev &&
		    IN_DEV_PROXY_ARP_PVLAN(in_dev) == 0) {
			reason = SKB_DROP_REASON_ARP_PVLAN_DISABLE;
			goto cleanup;
		}
	}

	if (IN_DEV_ORCONF(in_dev, NOPOLICY))
		IPCB(skb)->flags |= IPSKB_NOPOLICY;

	fnhe = find_exception(nhc, daddr);
	if (do_cache) {
		if (fnhe)
			rth = rcu_dereference(fnhe->fnhe_rth_input);
		else
			rth = rcu_dereference(nhc->nhc_rth_input);
		if (rt_cache_valid(rth)) {
			skb_dst_set_noref(skb, &rth->dst);
			goto out;
		}
	}

	rth = rt_dst_alloc(out_dev->dev, 0, res->type,
			   IN_DEV_ORCONF(out_dev, NOXFRM));
	if (!rth) {
		reason = SKB_DROP_REASON_NOMEM;
		goto cleanup;
	}

	rth->rt_is_input = 1;
	RT_CACHE_STAT_INC(in_slow_tot);

	rth->dst.input = ip_forward;

	rt_set_nexthop(rth, daddr, res, fnhe, res->fi, res->type, itag,
		       do_cache);
	lwtunnel_set_redirect(&rth->dst);
	skb_dst_set(skb, &rth->dst);
out:
	reason = SKB_NOT_DROPPED_YET;
cleanup:
	return reason;
}

#ifdef CONFIG_IP_ROUTE_MULTIPATH
/* To make ICMP packets follow the right flow, the multipath hash is
 * calculated from the inner IP addresses.
 */
static void ip_multipath_l3_keys(const struct sk_buff *skb,
				 struct flow_keys *hash_keys)
{
	const struct iphdr *outer_iph = ip_hdr(skb);
	const struct iphdr *key_iph = outer_iph;
	const struct iphdr *inner_iph;
	const struct icmphdr *icmph;
	struct iphdr _inner_iph;
	struct icmphdr _icmph;

	if (likely(outer_iph->protocol != IPPROTO_ICMP))
		goto out;

	if (unlikely((outer_iph->frag_off & htons(IP_OFFSET)) != 0))
		goto out;

	icmph = skb_header_pointer(skb, outer_iph->ihl * 4, sizeof(_icmph),
				   &_icmph);
	if (!icmph)
		goto out;

	if (!icmp_is_err(icmph->type))
		goto out;

	inner_iph = skb_header_pointer(skb,
				       outer_iph->ihl * 4 + sizeof(_icmph),
				       sizeof(_inner_iph), &_inner_iph);
	if (!inner_iph)
		goto out;

	key_iph = inner_iph;
out:
	hash_keys->addrs.v4addrs.src = key_iph->saddr;
	hash_keys->addrs.v4addrs.dst = key_iph->daddr;
}

static u32 fib_multipath_custom_hash_outer(const struct net *net,
					   const struct sk_buff *skb,
					   bool *p_has_inner)
{
	u32 hash_fields = READ_ONCE(net->ipv4.sysctl_fib_multipath_hash_fields);
	struct flow_keys keys, hash_keys;

	if (!(hash_fields & FIB_MULTIPATH_HASH_FIELD_OUTER_MASK))
		return 0;

	memset(&hash_keys, 0, sizeof(hash_keys));
	skb_flow_dissect_flow_keys(skb, &keys, FLOW_DISSECTOR_F_STOP_AT_ENCAP);

	hash_keys.control.addr_type = FLOW_DISSECTOR_KEY_IPV4_ADDRS;
	if (hash_fields & FIB_MULTIPATH_HASH_FIELD_SRC_IP)
		hash_keys.addrs.v4addrs.src = keys.addrs.v4addrs.src;
	if (hash_fields & FIB_MULTIPATH_HASH_FIELD_DST_IP)
		hash_keys.addrs.v4addrs.dst = keys.addrs.v4addrs.dst;
	if (hash_fields & FIB_MULTIPATH_HASH_FIELD_IP_PROTO)
		hash_keys.basic.ip_proto = keys.basic.ip_proto;
	if (hash_fields & FIB_MULTIPATH_HASH_FIELD_SRC_PORT)
		hash_keys.ports.src = keys.ports.src;
	if (hash_fields & FIB_MULTIPATH_HASH_FIELD_DST_PORT)
		hash_keys.ports.dst = keys.ports.dst;

	*p_has_inner = !!(keys.control.flags & FLOW_DIS_ENCAPSULATION);
	return fib_multipath_hash_from_keys(net, &hash_keys);
}

static u32 fib_multipath_custom_hash_inner(const struct net *net,
					   const struct sk_buff *skb,
					   bool has_inner)
{
	u32 hash_fields = READ_ONCE(net->ipv4.sysctl_fib_multipath_hash_fields);
	struct flow_keys keys, hash_keys;

	/* We assume the packet carries an encapsulation, but if none was
	 * encountered during dissection of the outer flow, then there is no
	 * point in calling the flow dissector again.
	 */
	if (!has_inner)
		return 0;

	if (!(hash_fields & FIB_MULTIPATH_HASH_FIELD_INNER_MASK))
		return 0;

	memset(&hash_keys, 0, sizeof(hash_keys));
	skb_flow_dissect_flow_keys(skb, &keys, 0);

	if (!(keys.control.flags & FLOW_DIS_ENCAPSULATION))
		return 0;

	if (keys.control.addr_type == FLOW_DISSECTOR_KEY_IPV4_ADDRS) {
		hash_keys.control.addr_type = FLOW_DISSECTOR_KEY_IPV4_ADDRS;
		if (hash_fields & FIB_MULTIPATH_HASH_FIELD_INNER_SRC_IP)
			hash_keys.addrs.v4addrs.src = keys.addrs.v4addrs.src;
		if (hash_fields & FIB_MULTIPATH_HASH_FIELD_INNER_DST_IP)
			hash_keys.addrs.v4addrs.dst = keys.addrs.v4addrs.dst;
	} else if (keys.control.addr_type == FLOW_DISSECTOR_KEY_IPV6_ADDRS) {
		hash_keys.control.addr_type = FLOW_DISSECTOR_KEY_IPV6_ADDRS;
		if (hash_fields & FIB_MULTIPATH_HASH_FIELD_INNER_SRC_IP)
			hash_keys.addrs.v6addrs.src = keys.addrs.v6addrs.src;
		if (hash_fields & FIB_MULTIPATH_HASH_FIELD_INNER_DST_IP)
			hash_keys.addrs.v6addrs.dst = keys.addrs.v6addrs.dst;
		if (hash_fields & FIB_MULTIPATH_HASH_FIELD_INNER_FLOWLABEL)
			hash_keys.tags.flow_label = keys.tags.flow_label;
	}

	if (hash_fields & FIB_MULTIPATH_HASH_FIELD_INNER_IP_PROTO)
		hash_keys.basic.ip_proto = keys.basic.ip_proto;
	if (hash_fields & FIB_MULTIPATH_HASH_FIELD_INNER_SRC_PORT)
		hash_keys.ports.src = keys.ports.src;
	if (hash_fields & FIB_MULTIPATH_HASH_FIELD_INNER_DST_PORT)
		hash_keys.ports.dst = keys.ports.dst;

	return fib_multipath_hash_from_keys(net, &hash_keys);
}

static u32 fib_multipath_custom_hash_skb(const struct net *net,
					 const struct sk_buff *skb)
{
	u32 mhash, mhash_inner;
	bool has_inner = true;

	mhash = fib_multipath_custom_hash_outer(net, skb, &has_inner);
	mhash_inner = fib_multipath_custom_hash_inner(net, skb, has_inner);

	return jhash_2words(mhash, mhash_inner, 0);
}

static u32 fib_multipath_custom_hash_fl4(const struct net *net,
					 const struct flowi4 *fl4)
{
	u32 hash_fields = READ_ONCE(net->ipv4.sysctl_fib_multipath_hash_fields);
	struct flow_keys hash_keys;

	if (!(hash_fields & FIB_MULTIPATH_HASH_FIELD_OUTER_MASK))
		return 0;

	memset(&hash_keys, 0, sizeof(hash_keys));
	hash_keys.control.addr_type = FLOW_DISSECTOR_KEY_IPV4_ADDRS;
	if (hash_fields & FIB_MULTIPATH_HASH_FIELD_SRC_IP)
		hash_keys.addrs.v4addrs.src = fl4->saddr;
	if (hash_fields & FIB_MULTIPATH_HASH_FIELD_DST_IP)
		hash_keys.addrs.v4addrs.dst = fl4->daddr;
	if (hash_fields & FIB_MULTIPATH_HASH_FIELD_IP_PROTO)
		hash_keys.basic.ip_proto = fl4->flowi4_proto;
	if (hash_fields & FIB_MULTIPATH_HASH_FIELD_SRC_PORT)
		hash_keys.ports.src = fl4->fl4_sport;
	if (hash_fields & FIB_MULTIPATH_HASH_FIELD_DST_PORT)
		hash_keys.ports.dst = fl4->fl4_dport;

	return fib_multipath_hash_from_keys(net, &hash_keys);
}

/* if skb is set it will be used and fl4 can be NULL */
int fib_multipath_hash(const struct net *net, const struct flowi4 *fl4,
		       const struct sk_buff *skb, struct flow_keys *flkeys)
{
	u32 multipath_hash = fl4 ? fl4->flowi4_multipath_hash : 0;
	struct flow_keys hash_keys;
	u32 mhash = 0;

	switch (READ_ONCE(net->ipv4.sysctl_fib_multipath_hash_policy)) {
	case 0:
		memset(&hash_keys, 0, sizeof(hash_keys));
		hash_keys.control.addr_type = FLOW_DISSECTOR_KEY_IPV4_ADDRS;
		if (skb) {
			ip_multipath_l3_keys(skb, &hash_keys);
		} else {
			hash_keys.addrs.v4addrs.src = fl4->saddr;
			hash_keys.addrs.v4addrs.dst = fl4->daddr;
		}
		mhash = fib_multipath_hash_from_keys(net, &hash_keys);
		break;
	case 1:
		/* skb is currently provided only when forwarding */
		if (skb) {
			unsigned int flag = FLOW_DISSECTOR_F_STOP_AT_ENCAP;
			struct flow_keys keys;

			/* short-circuit if we already have L4 hash present */
			if (skb->l4_hash)
				return skb_get_hash_raw(skb) >> 1;

			memset(&hash_keys, 0, sizeof(hash_keys));

			if (!flkeys) {
				skb_flow_dissect_flow_keys(skb, &keys, flag);
				flkeys = &keys;
			}

			hash_keys.control.addr_type = FLOW_DISSECTOR_KEY_IPV4_ADDRS;
			hash_keys.addrs.v4addrs.src = flkeys->addrs.v4addrs.src;
			hash_keys.addrs.v4addrs.dst = flkeys->addrs.v4addrs.dst;
			hash_keys.ports.src = flkeys->ports.src;
			hash_keys.ports.dst = flkeys->ports.dst;
			hash_keys.basic.ip_proto = flkeys->basic.ip_proto;
		} else {
			memset(&hash_keys, 0, sizeof(hash_keys));
			hash_keys.control.addr_type = FLOW_DISSECTOR_KEY_IPV4_ADDRS;
			hash_keys.addrs.v4addrs.src = fl4->saddr;
			hash_keys.addrs.v4addrs.dst = fl4->daddr;
			hash_keys.ports.src = fl4->fl4_sport;
			hash_keys.ports.dst = fl4->fl4_dport;
			hash_keys.basic.ip_proto = fl4->flowi4_proto;
		}
		mhash = fib_multipath_hash_from_keys(net, &hash_keys);
		break;
	case 2:
		memset(&hash_keys, 0, sizeof(hash_keys));
		/* skb is currently provided only when forwarding */
		if (skb) {
			struct flow_keys keys;

			skb_flow_dissect_flow_keys(skb, &keys, 0);
			/* Inner can be v4 or v6 */
			if (keys.control.addr_type == FLOW_DISSECTOR_KEY_IPV4_ADDRS) {
				hash_keys.control.addr_type = FLOW_DISSECTOR_KEY_IPV4_ADDRS;
				hash_keys.addrs.v4addrs.src = keys.addrs.v4addrs.src;
				hash_keys.addrs.v4addrs.dst = keys.addrs.v4addrs.dst;
			} else if (keys.control.addr_type == FLOW_DISSECTOR_KEY_IPV6_ADDRS) {
				hash_keys.control.addr_type = FLOW_DISSECTOR_KEY_IPV6_ADDRS;
				hash_keys.addrs.v6addrs.src = keys.addrs.v6addrs.src;
				hash_keys.addrs.v6addrs.dst = keys.addrs.v6addrs.dst;
				hash_keys.tags.flow_label = keys.tags.flow_label;
				hash_keys.basic.ip_proto = keys.basic.ip_proto;
			} else {
				/* Same as case 0 */
				hash_keys.control.addr_type = FLOW_DISSECTOR_KEY_IPV4_ADDRS;
				ip_multipath_l3_keys(skb, &hash_keys);
			}
		} else {
			/* Same as case 0 */
			hash_keys.control.addr_type = FLOW_DISSECTOR_KEY_IPV4_ADDRS;
			hash_keys.addrs.v4addrs.src = fl4->saddr;
			hash_keys.addrs.v4addrs.dst = fl4->daddr;
		}
		mhash = fib_multipath_hash_from_keys(net, &hash_keys);
		break;
	case 3:
		if (skb)
			mhash = fib_multipath_custom_hash_skb(net, skb);
		else
			mhash = fib_multipath_custom_hash_fl4(net, fl4);
		break;
	}

	if (multipath_hash)
		mhash = jhash_2words(mhash, multipath_hash, 0);

	return mhash >> 1;
}
#endif /* CONFIG_IP_ROUTE_MULTIPATH */

static enum skb_drop_reason
ip_mkroute_input(struct sk_buff *skb, struct fib_result *res,
		 struct in_device *in_dev, __be32 daddr,
		 __be32 saddr, dscp_t dscp, struct flow_keys *hkeys)
{
#ifdef CONFIG_IP_ROUTE_MULTIPATH
	if (res->fi && fib_info_num_path(res->fi) > 1) {
		int h = fib_multipath_hash(res->fi->fib_net, NULL, skb, hkeys);

		fib_select_multipath(res, h);
		IPCB(skb)->flags |= IPSKB_MULTIPATH;
	}
#endif

	/* create a routing cache entry */
	return __mkroute_input(skb, res, in_dev, daddr, saddr, dscp);
}

/* Implements all the saddr-related checks as ip_route_input_slow(),
 * assuming daddr is valid and the destination is not a local broadcast one.
 * Uses the provided hint instead of performing a route lookup.
 */
enum skb_drop_reason
ip_route_use_hint(struct sk_buff *skb, __be32 daddr, __be32 saddr,
		  dscp_t dscp, struct net_device *dev,
		  const struct sk_buff *hint)
{
	enum skb_drop_reason reason = SKB_DROP_REASON_NOT_SPECIFIED;
	struct in_device *in_dev = __in_dev_get_rcu(dev);
	struct rtable *rt = skb_rtable(hint);
	struct net *net = dev_net(dev);
	u32 tag = 0;

	if (!in_dev)
		return reason;

	if (ipv4_is_multicast(saddr) || ipv4_is_lbcast(saddr)) {
		reason = SKB_DROP_REASON_IP_INVALID_SOURCE;
		goto martian_source;
	}

	if (ipv4_is_zeronet(saddr)) {
		reason = SKB_DROP_REASON_IP_INVALID_SOURCE;
		goto martian_source;
	}

	if (ipv4_is_loopback(saddr) && !IN_DEV_NET_ROUTE_LOCALNET(in_dev, net)) {
		reason = SKB_DROP_REASON_IP_LOCALNET;
		goto martian_source;
	}

	if (rt->rt_type != RTN_LOCAL)
		goto skip_validate_source;

	reason = fib_validate_source_reason(skb, saddr, daddr, dscp, 0, dev,
					    in_dev, &tag);
	if (reason)
		goto martian_source;

skip_validate_source:
	skb_dst_copy(skb, hint);
	return SKB_NOT_DROPPED_YET;

martian_source:
	ip_handle_martian_source(dev, in_dev, skb, daddr, saddr);
	return reason;
}

/* get device for dst_alloc with local routes */
static struct net_device *ip_rt_get_dev(struct net *net,
					const struct fib_result *res)
{
	struct fib_nh_common *nhc = res->fi ? res->nhc : NULL;
	struct net_device *dev = NULL;

	if (nhc)
		dev = l3mdev_master_dev_rcu(nhc->nhc_dev);

	return dev ? : net->loopback_dev;
}

/*
 *	NOTE. We drop all the packets that has local source
 *	addresses, because every properly looped back packet
 *	must have correct destination already attached by output routine.
 *	Changes in the enforced policies must be applied also to
 *	ip_route_use_hint().
 *
 *	Such approach solves two big problems:
 *	1. Not simplex devices are handled properly.
 *	2. IP spoofing attempts are filtered with 100% of guarantee.
 *	called with rcu_read_lock()
 */

static enum skb_drop_reason
ip_route_input_slow(struct sk_buff *skb, __be32 daddr, __be32 saddr,
		    dscp_t dscp, struct net_device *dev,
		    struct fib_result *res)
{
	enum skb_drop_reason reason = SKB_DROP_REASON_NOT_SPECIFIED;
	struct in_device *in_dev = __in_dev_get_rcu(dev);
	struct flow_keys *flkeys = NULL, _flkeys;
	struct net    *net = dev_net(dev);
	struct ip_tunnel_info *tun_info;
	int		err = -EINVAL;
	unsigned int	flags = 0;
	u32		itag = 0;
	struct rtable	*rth;
	struct flowi4	fl4;
	bool do_cache = true;

	/* IP on this device is disabled. */

	if (!in_dev)
		goto out;

	/* Check for the most weird martians, which can be not detected
	 * by fib_lookup.
	 */

	tun_info = skb_tunnel_info(skb);
	if (tun_info && !(tun_info->mode & IP_TUNNEL_INFO_TX))
		fl4.flowi4_tun_key.tun_id = tun_info->key.tun_id;
	else
		fl4.flowi4_tun_key.tun_id = 0;
	skb_dst_drop(skb);

	if (ipv4_is_multicast(saddr) || ipv4_is_lbcast(saddr)) {
		reason = SKB_DROP_REASON_IP_INVALID_SOURCE;
		goto martian_source;
	}

	res->fi = NULL;
	res->table = NULL;
	if (ipv4_is_lbcast(daddr) || (saddr == 0 && daddr == 0))
		goto brd_input;

	/* Accept zero addresses only to limited broadcast;
	 * I even do not know to fix it or not. Waiting for complains :-)
	 */
	if (ipv4_is_zeronet(saddr)) {
		reason = SKB_DROP_REASON_IP_INVALID_SOURCE;
		goto martian_source;
	}

	if (ipv4_is_zeronet(daddr)) {
		reason = SKB_DROP_REASON_IP_INVALID_DEST;
		goto martian_destination;
	}

	/* Following code try to avoid calling IN_DEV_NET_ROUTE_LOCALNET(),
	 * and call it once if daddr or/and saddr are loopback addresses
	 */
	if (ipv4_is_loopback(daddr)) {
		if (!IN_DEV_NET_ROUTE_LOCALNET(in_dev, net)) {
			reason = SKB_DROP_REASON_IP_LOCALNET;
			goto martian_destination;
		}
	} else if (ipv4_is_loopback(saddr)) {
		if (!IN_DEV_NET_ROUTE_LOCALNET(in_dev, net)) {
			reason = SKB_DROP_REASON_IP_LOCALNET;
			goto martian_source;
		}
	}

	/*
	 *	Now we are ready to route packet.
	 */
	fl4.flowi4_l3mdev = 0;
	fl4.flowi4_oif = 0;
	fl4.flowi4_iif = dev->ifindex;
	fl4.flowi4_mark = skb->mark;
	fl4.flowi4_tos = inet_dscp_to_dsfield(dscp);
	fl4.flowi4_scope = RT_SCOPE_UNIVERSE;
	fl4.flowi4_flags = 0;
	fl4.daddr = daddr;
	fl4.saddr = saddr;
	fl4.flowi4_uid = sock_net_uid(net, NULL);
	fl4.flowi4_multipath_hash = 0;

	if (fib4_rules_early_flow_dissect(net, skb, &fl4, &_flkeys)) {
		flkeys = &_flkeys;
	} else {
		fl4.flowi4_proto = 0;
		fl4.fl4_sport = 0;
		fl4.fl4_dport = 0;
	}

	err = fib_lookup(net, &fl4, res, 0);
	if (err != 0) {
		if (!IN_DEV_FORWARD(in_dev))
			err = -EHOSTUNREACH;
		goto no_route;
	}

	if (res->type == RTN_BROADCAST) {
		if (IN_DEV_BFORWARD(in_dev))
			goto make_route;
		/* not do cache if bc_forwarding is enabled */
		if (IPV4_DEVCONF_ALL_RO(net, BC_FORWARDING))
			do_cache = false;
		goto brd_input;
	}

	err = -EINVAL;
	if (res->type == RTN_LOCAL) {
		reason = fib_validate_source_reason(skb, saddr, daddr, dscp,
						    0, dev, in_dev, &itag);
		if (reason)
			goto martian_source;
		goto local_input;
	}

	if (!IN_DEV_FORWARD(in_dev)) {
		err = -EHOSTUNREACH;
		goto no_route;
	}
	if (res->type != RTN_UNICAST) {
		reason = SKB_DROP_REASON_IP_INVALID_DEST;
		goto martian_destination;
	}

make_route:
	reason = ip_mkroute_input(skb, res, in_dev, daddr, saddr, dscp,
				  flkeys);

out:
	return reason;

brd_input:
	if (skb->protocol != htons(ETH_P_IP)) {
		reason = SKB_DROP_REASON_INVALID_PROTO;
		goto out;
	}

	if (!ipv4_is_zeronet(saddr)) {
		reason = fib_validate_source_reason(skb, saddr, 0, dscp, 0,
						    dev, in_dev, &itag);
		if (reason)
			goto martian_source;
	}
	flags |= RTCF_BROADCAST;
	res->type = RTN_BROADCAST;
	RT_CACHE_STAT_INC(in_brd);

local_input:
	if (IN_DEV_ORCONF(in_dev, NOPOLICY))
		IPCB(skb)->flags |= IPSKB_NOPOLICY;

	do_cache &= res->fi && !itag;
	if (do_cache) {
		struct fib_nh_common *nhc = FIB_RES_NHC(*res);

		rth = rcu_dereference(nhc->nhc_rth_input);
		if (rt_cache_valid(rth)) {
			skb_dst_set_noref(skb, &rth->dst);
			reason = SKB_NOT_DROPPED_YET;
			goto out;
		}
	}

	rth = rt_dst_alloc(ip_rt_get_dev(net, res),
			   flags | RTCF_LOCAL, res->type, false);
	if (!rth)
		goto e_nobufs;

	rth->dst.output= ip_rt_bug;
#ifdef CONFIG_IP_ROUTE_CLASSID
	rth->dst.tclassid = itag;
#endif
	rth->rt_is_input = 1;

	RT_CACHE_STAT_INC(in_slow_tot);
	if (res->type == RTN_UNREACHABLE) {
		rth->dst.input= ip_error;
		rth->dst.error= -err;
		rth->rt_flags	&= ~RTCF_LOCAL;
	}

	if (do_cache) {
		struct fib_nh_common *nhc = FIB_RES_NHC(*res);

		rth->dst.lwtstate = lwtstate_get(nhc->nhc_lwtstate);
		if (lwtunnel_input_redirect(rth->dst.lwtstate)) {
			WARN_ON(rth->dst.input == lwtunnel_input);
			rth->dst.lwtstate->orig_input = rth->dst.input;
			rth->dst.input = lwtunnel_input;
		}

		if (unlikely(!rt_cache_route(nhc, rth)))
			rt_add_uncached_list(rth);
	}
	skb_dst_set(skb, &rth->dst);
	reason = SKB_NOT_DROPPED_YET;
	goto out;

no_route:
	RT_CACHE_STAT_INC(in_no_route);
	res->type = RTN_UNREACHABLE;
	res->fi = NULL;
	res->table = NULL;
	goto local_input;

	/*
	 *	Do not cache martian addresses: they should be logged (RFC1812)
	 */
martian_destination:
	RT_CACHE_STAT_INC(in_martian_dst);
#ifdef CONFIG_IP_ROUTE_VERBOSE
	if (IN_DEV_LOG_MARTIANS(in_dev))
		net_warn_ratelimited("martian destination %pI4 from %pI4, dev %s\n",
				     &daddr, &saddr, dev->name);
#endif
	goto out;

e_nobufs:
	reason = SKB_DROP_REASON_NOMEM;
	goto out;

martian_source:
	ip_handle_martian_source(dev, in_dev, skb, daddr, saddr);
	goto out;
}

/* called with rcu_read_lock held */
static enum skb_drop_reason
ip_route_input_rcu(struct sk_buff *skb, __be32 daddr, __be32 saddr,
		   dscp_t dscp, struct net_device *dev,
		   struct fib_result *res)
{
	/* Multicast recognition logic is moved from route cache to here.
	 * The problem was that too many Ethernet cards have broken/missing
	 * hardware multicast filters :-( As result the host on multicasting
	 * network acquires a lot of useless route cache entries, sort of
	 * SDR messages from all the world. Now we try to get rid of them.
	 * Really, provided software IP multicast filter is organized
	 * reasonably (at least, hashed), it does not result in a slowdown
	 * comparing with route cache reject entries.
	 * Note, that multicast routers are not affected, because
	 * route cache entry is created eventually.
	 */
	if (ipv4_is_multicast(daddr)) {
		enum skb_drop_reason reason = SKB_DROP_REASON_NOT_SPECIFIED;
		struct in_device *in_dev = __in_dev_get_rcu(dev);
		int our = 0;

		if (!in_dev)
			return reason;

		our = ip_check_mc_rcu(in_dev, daddr, saddr,
				      ip_hdr(skb)->protocol);

		/* check l3 master if no match yet */
		if (!our && netif_is_l3_slave(dev)) {
			struct in_device *l3_in_dev;

			l3_in_dev = __in_dev_get_rcu(skb->dev);
			if (l3_in_dev)
				our = ip_check_mc_rcu(l3_in_dev, daddr, saddr,
						      ip_hdr(skb)->protocol);
		}

		if (our
#ifdef CONFIG_IP_MROUTE
			||
		    (!ipv4_is_local_multicast(daddr) &&
		     IN_DEV_MFORWARD(in_dev))
#endif
		   ) {
			reason = ip_route_input_mc(skb, daddr, saddr, dscp,
						   dev, our);
		}
		return reason;
	}

	return ip_route_input_slow(skb, daddr, saddr, dscp, dev, res);
}

enum skb_drop_reason ip_route_input_noref(struct sk_buff *skb, __be32 daddr,
					  __be32 saddr, dscp_t dscp,
					  struct net_device *dev)
{
	enum skb_drop_reason reason;
	struct fib_result res;

	rcu_read_lock();
	reason = ip_route_input_rcu(skb, daddr, saddr, dscp, dev, &res);
	rcu_read_unlock();

	return reason;
}
EXPORT_SYMBOL(ip_route_input_noref);

/* called with rcu_read_lock() */
static struct rtable *__mkroute_output(const struct fib_result *res,
				       const struct flowi4 *fl4, int orig_oif,
				       struct net_device *dev_out,
				       unsigned int flags)
{
	struct fib_info *fi = res->fi;
	struct fib_nh_exception *fnhe;
	struct in_device *in_dev;
	u16 type = res->type;
	struct rtable *rth;
	bool do_cache;

	in_dev = __in_dev_get_rcu(dev_out);
	if (!in_dev)
		return ERR_PTR(-EINVAL);

	if (likely(!IN_DEV_ROUTE_LOCALNET(in_dev)))
		if (ipv4_is_loopback(fl4->saddr) &&
		    !(dev_out->flags & IFF_LOOPBACK) &&
		    !netif_is_l3_master(dev_out))
			return ERR_PTR(-EINVAL);

	if (ipv4_is_lbcast(fl4->daddr))
		type = RTN_BROADCAST;
	else if (ipv4_is_multicast(fl4->daddr))
		type = RTN_MULTICAST;
	else if (ipv4_is_zeronet(fl4->daddr))
		return ERR_PTR(-EINVAL);

	if (dev_out->flags & IFF_LOOPBACK)
		flags |= RTCF_LOCAL;

	do_cache = true;
	if (type == RTN_BROADCAST) {
		flags |= RTCF_BROADCAST | RTCF_LOCAL;
		fi = NULL;
	} else if (type == RTN_MULTICAST) {
		flags |= RTCF_MULTICAST | RTCF_LOCAL;
		if (!ip_check_mc_rcu(in_dev, fl4->daddr, fl4->saddr,
				     fl4->flowi4_proto))
			flags &= ~RTCF_LOCAL;
		else
			do_cache = false;
		/* If multicast route do not exist use
		 * default one, but do not gateway in this case.
		 * Yes, it is hack.
		 */
		if (fi && res->prefixlen < 4)
			fi = NULL;
	} else if ((type == RTN_LOCAL) && (orig_oif != 0) &&
		   (orig_oif != dev_out->ifindex)) {
		/* For local routes that require a particular output interface
		 * we do not want to cache the result.  Caching the result
		 * causes incorrect behaviour when there are multiple source
		 * addresses on the interface, the end result being that if the
		 * intended recipient is waiting on that interface for the
		 * packet he won't receive it because it will be delivered on
		 * the loopback interface and the IP_PKTINFO ipi_ifindex will
		 * be set to the loopback interface as well.
		 */
		do_cache = false;
	}

	fnhe = NULL;
	do_cache &= fi != NULL;
	if (fi) {
		struct fib_nh_common *nhc = FIB_RES_NHC(*res);
		struct rtable __rcu **prth;

		fnhe = find_exception(nhc, fl4->daddr);
		if (!do_cache)
			goto add;
		if (fnhe) {
			prth = &fnhe->fnhe_rth_output;
		} else {
			if (unlikely(fl4->flowi4_flags &
				     FLOWI_FLAG_KNOWN_NH &&
				     !(nhc->nhc_gw_family &&
				       nhc->nhc_scope == RT_SCOPE_LINK))) {
				do_cache = false;
				goto add;
			}
			prth = raw_cpu_ptr(nhc->nhc_pcpu_rth_output);
		}
		rth = rcu_dereference(*prth);
		if (rt_cache_valid(rth) && dst_hold_safe(&rth->dst))
			return rth;
	}

add:
	rth = rt_dst_alloc(dev_out, flags, type,
			   IN_DEV_ORCONF(in_dev, NOXFRM));
	if (!rth)
		return ERR_PTR(-ENOBUFS);

	rth->rt_iif = orig_oif;

	RT_CACHE_STAT_INC(out_slow_tot);

	if (flags & (RTCF_BROADCAST | RTCF_MULTICAST)) {
		if (flags & RTCF_LOCAL &&
		    !(dev_out->flags & IFF_LOOPBACK)) {
			rth->dst.output = ip_mc_output;
			RT_CACHE_STAT_INC(out_slow_mc);
		}
#ifdef CONFIG_IP_MROUTE
		if (type == RTN_MULTICAST) {
			if (IN_DEV_MFORWARD(in_dev) &&
			    !ipv4_is_local_multicast(fl4->daddr)) {
				rth->dst.input = ip_mr_input;
				rth->dst.output = ip_mc_output;
			}
		}
#endif
	}

	rt_set_nexthop(rth, fl4->daddr, res, fnhe, fi, type, 0, do_cache);
	lwtunnel_set_redirect(&rth->dst);

	return rth;
}

/*
 * Major route resolver routine.
 */

struct rtable *ip_route_output_key_hash(struct net *net, struct flowi4 *fl4,
					const struct sk_buff *skb)
{
	struct fib_result res = {
		.type		= RTN_UNSPEC,
		.fi		= NULL,
		.table		= NULL,
		.tclassid	= 0,
	};
	struct rtable *rth;

	fl4->flowi4_iif = LOOPBACK_IFINDEX;
	fl4->flowi4_tos &= INET_DSCP_MASK;

	rcu_read_lock();
	rth = ip_route_output_key_hash_rcu(net, fl4, &res, skb);
	rcu_read_unlock();

	return rth;
}
EXPORT_SYMBOL_GPL(ip_route_output_key_hash);

struct rtable *ip_route_output_key_hash_rcu(struct net *net, struct flowi4 *fl4,
					    struct fib_result *res,
					    const struct sk_buff *skb)
{
	struct net_device *dev_out = NULL;
	int orig_oif = fl4->flowi4_oif;
	unsigned int flags = 0;
	struct rtable *rth;
	int err;

	if (fl4->saddr) {
		if (ipv4_is_multicast(fl4->saddr) ||
		    ipv4_is_lbcast(fl4->saddr) ||
		    ipv4_is_zeronet(fl4->saddr)) {
			rth = ERR_PTR(-EINVAL);
			goto out;
		}

		rth = ERR_PTR(-ENETUNREACH);

		/* I removed check for oif == dev_out->oif here.
		 * It was wrong for two reasons:
		 * 1. ip_dev_find(net, saddr) can return wrong iface, if saddr
		 *    is assigned to multiple interfaces.
		 * 2. Moreover, we are allowed to send packets with saddr
		 *    of another iface. --ANK
		 */

		if (fl4->flowi4_oif == 0 &&
		    (ipv4_is_multicast(fl4->daddr) ||
		     ipv4_is_lbcast(fl4->daddr))) {
			/* It is equivalent to inet_addr_type(saddr) == RTN_LOCAL */
			dev_out = __ip_dev_find(net, fl4->saddr, false);
			if (!dev_out)
				goto out;

			/* Special hack: user can direct multicasts
			 * and limited broadcast via necessary interface
			 * without fiddling with IP_MULTICAST_IF or IP_PKTINFO.
			 * This hack is not just for fun, it allows
			 * vic,vat and friends to work.
			 * They bind socket to loopback, set ttl to zero
			 * and expect that it will work.
			 * From the viewpoint of routing cache they are broken,
			 * because we are not allowed to build multicast path
			 * with loopback source addr (look, routing cache
			 * cannot know, that ttl is zero, so that packet
			 * will not leave this host and route is valid).
			 * Luckily, this hack is good workaround.
			 */

			fl4->flowi4_oif = dev_out->ifindex;
			goto make_route;
		}

		if (!(fl4->flowi4_flags & FLOWI_FLAG_ANYSRC)) {
			/* It is equivalent to inet_addr_type(saddr) == RTN_LOCAL */
			if (!__ip_dev_find(net, fl4->saddr, false))
				goto out;
		}
	}


	if (fl4->flowi4_oif) {
		dev_out = dev_get_by_index_rcu(net, fl4->flowi4_oif);
		rth = ERR_PTR(-ENODEV);
		if (!dev_out)
			goto out;

		/* RACE: Check return value of inet_select_addr instead. */
		if (!(dev_out->flags & IFF_UP) || !__in_dev_get_rcu(dev_out)) {
			rth = ERR_PTR(-ENETUNREACH);
			goto out;
		}
		if (ipv4_is_local_multicast(fl4->daddr) ||
		    ipv4_is_lbcast(fl4->daddr) ||
		    fl4->flowi4_proto == IPPROTO_IGMP) {
			if (!fl4->saddr)
				fl4->saddr = inet_select_addr(dev_out, 0,
							      RT_SCOPE_LINK);
			goto make_route;
		}
		if (!fl4->saddr) {
			if (ipv4_is_multicast(fl4->daddr))
				fl4->saddr = inet_select_addr(dev_out, 0,
							      fl4->flowi4_scope);
			else if (!fl4->daddr)
				fl4->saddr = inet_select_addr(dev_out, 0,
							      RT_SCOPE_HOST);
		}
	}

	if (!fl4->daddr) {
		fl4->daddr = fl4->saddr;
		if (!fl4->daddr)
			fl4->daddr = fl4->saddr = htonl(INADDR_LOOPBACK);
		dev_out = net->loopback_dev;
		fl4->flowi4_oif = LOOPBACK_IFINDEX;
		res->type = RTN_LOCAL;
		flags |= RTCF_LOCAL;
		goto make_route;
	}

	err = fib_lookup(net, fl4, res, 0);
	if (err) {
		res->fi = NULL;
		res->table = NULL;
		if (fl4->flowi4_oif &&
		    (ipv4_is_multicast(fl4->daddr) || !fl4->flowi4_l3mdev)) {
			/* Apparently, routing tables are wrong. Assume,
			 * that the destination is on link.
			 *
			 * WHY? DW.
			 * Because we are allowed to send to iface
			 * even if it has NO routes and NO assigned
			 * addresses. When oif is specified, routing
			 * tables are looked up with only one purpose:
			 * to catch if destination is gatewayed, rather than
			 * direct. Moreover, if MSG_DONTROUTE is set,
			 * we send packet, ignoring both routing tables
			 * and ifaddr state. --ANK
			 *
			 *
			 * We could make it even if oif is unknown,
			 * likely IPv6, but we do not.
			 */

			if (fl4->saddr == 0)
				fl4->saddr = inet_select_addr(dev_out, 0,
							      RT_SCOPE_LINK);
			res->type = RTN_UNICAST;
			goto make_route;
		}
		rth = ERR_PTR(err);
		goto out;
	}

	if (res->type == RTN_LOCAL) {
		if (!fl4->saddr) {
			if (res->fi->fib_prefsrc)
				fl4->saddr = res->fi->fib_prefsrc;
			else
				fl4->saddr = fl4->daddr;
		}

		/* L3 master device is the loopback for that domain */
		dev_out = l3mdev_master_dev_rcu(FIB_RES_DEV(*res)) ? :
			net->loopback_dev;

		/* make sure orig_oif points to fib result device even
		 * though packet rx/tx happens over loopback or l3mdev
		 */
		orig_oif = FIB_RES_OIF(*res);

		fl4->flowi4_oif = dev_out->ifindex;
		flags |= RTCF_LOCAL;
		goto make_route;
	}

	fib_select_path(net, res, fl4, skb);

	dev_out = FIB_RES_DEV(*res);

make_route:
	rth = __mkroute_output(res, fl4, orig_oif, dev_out, flags);

out:
	return rth;
}

static struct dst_ops ipv4_dst_blackhole_ops = {
	.family			= AF_INET,
	.default_advmss		= ipv4_default_advmss,
	.neigh_lookup		= ipv4_neigh_lookup,
	.check			= dst_blackhole_check,
	.cow_metrics		= dst_blackhole_cow_metrics,
	.update_pmtu		= dst_blackhole_update_pmtu,
	.redirect		= dst_blackhole_redirect,
	.mtu			= dst_blackhole_mtu,
};

struct dst_entry *ipv4_blackhole_route(struct net *net, struct dst_entry *dst_orig)
{
	struct rtable *ort = dst_rtable(dst_orig);
	struct rtable *rt;

	rt = dst_alloc(&ipv4_dst_blackhole_ops, NULL, DST_OBSOLETE_DEAD, 0);
	if (rt) {
		struct dst_entry *new = &rt->dst;

		new->__use = 1;
		new->input = dst_discard;
		new->output = dst_discard_out;

		new->dev = net->loopback_dev;
		netdev_hold(new->dev, &new->dev_tracker, GFP_ATOMIC);

		rt->rt_is_input = ort->rt_is_input;
		rt->rt_iif = ort->rt_iif;
		rt->rt_pmtu = ort->rt_pmtu;
		rt->rt_mtu_locked = ort->rt_mtu_locked;

		rt->rt_genid = rt_genid_ipv4(net);
		rt->rt_flags = ort->rt_flags;
		rt->rt_type = ort->rt_type;
		rt->rt_uses_gateway = ort->rt_uses_gateway;
		rt->rt_gw_family = ort->rt_gw_family;
		if (rt->rt_gw_family == AF_INET)
			rt->rt_gw4 = ort->rt_gw4;
		else if (rt->rt_gw_family == AF_INET6)
			rt->rt_gw6 = ort->rt_gw6;
	}

	dst_release(dst_orig);

	return rt ? &rt->dst : ERR_PTR(-ENOMEM);
}

struct rtable *ip_route_output_flow(struct net *net, struct flowi4 *flp4,
				    const struct sock *sk)
{
	struct rtable *rt = __ip_route_output_key(net, flp4);

	if (IS_ERR(rt))
		return rt;

	if (flp4->flowi4_proto) {
		flp4->flowi4_oif = rt->dst.dev->ifindex;
		rt = dst_rtable(xfrm_lookup_route(net, &rt->dst,
						  flowi4_to_flowi(flp4),
						  sk, 0));
	}

	return rt;
}
EXPORT_SYMBOL_GPL(ip_route_output_flow);

/* called with rcu_read_lock held */
static int rt_fill_info(struct net *net, __be32 dst, __be32 src,
			struct rtable *rt, u32 table_id, dscp_t dscp,
			struct flowi4 *fl4, struct sk_buff *skb, u32 portid,
			u32 seq, unsigned int flags)
{
	struct rtmsg *r;
	struct nlmsghdr *nlh;
	unsigned long expires = 0;
	u32 error;
	u32 metrics[RTAX_MAX];

	nlh = nlmsg_put(skb, portid, seq, RTM_NEWROUTE, sizeof(*r), flags);
	if (!nlh)
		return -EMSGSIZE;

	r = nlmsg_data(nlh);
	r->rtm_family	 = AF_INET;
	r->rtm_dst_len	= 32;
	r->rtm_src_len	= 0;
	r->rtm_tos	= inet_dscp_to_dsfield(dscp);
	r->rtm_table	= table_id < 256 ? table_id : RT_TABLE_COMPAT;
	if (nla_put_u32(skb, RTA_TABLE, table_id))
		goto nla_put_failure;
	r->rtm_type	= rt->rt_type;
	r->rtm_scope	= RT_SCOPE_UNIVERSE;
	r->rtm_protocol = RTPROT_UNSPEC;
	r->rtm_flags	= (rt->rt_flags & ~0xFFFF) | RTM_F_CLONED;
	if (rt->rt_flags & RTCF_NOTIFY)
		r->rtm_flags |= RTM_F_NOTIFY;
	if (IPCB(skb)->flags & IPSKB_DOREDIRECT)
		r->rtm_flags |= RTCF_DOREDIRECT;

	if (nla_put_in_addr(skb, RTA_DST, dst))
		goto nla_put_failure;
	if (src) {
		r->rtm_src_len = 32;
		if (nla_put_in_addr(skb, RTA_SRC, src))
			goto nla_put_failure;
	}
	if (rt->dst.dev &&
	    nla_put_u32(skb, RTA_OIF, rt->dst.dev->ifindex))
		goto nla_put_failure;
	if (rt->dst.lwtstate &&
	    lwtunnel_fill_encap(skb, rt->dst.lwtstate, RTA_ENCAP, RTA_ENCAP_TYPE) < 0)
		goto nla_put_failure;
#ifdef CONFIG_IP_ROUTE_CLASSID
	if (rt->dst.tclassid &&
	    nla_put_u32(skb, RTA_FLOW, rt->dst.tclassid))
		goto nla_put_failure;
#endif
	if (fl4 && !rt_is_input_route(rt) &&
	    fl4->saddr != src) {
		if (nla_put_in_addr(skb, RTA_PREFSRC, fl4->saddr))
			goto nla_put_failure;
	}
	if (rt->rt_uses_gateway) {
		if (rt->rt_gw_family == AF_INET &&
		    nla_put_in_addr(skb, RTA_GATEWAY, rt->rt_gw4)) {
			goto nla_put_failure;
		} else if (rt->rt_gw_family == AF_INET6) {
			int alen = sizeof(struct in6_addr);
			struct nlattr *nla;
			struct rtvia *via;

			nla = nla_reserve(skb, RTA_VIA, alen + 2);
			if (!nla)
				goto nla_put_failure;

			via = nla_data(nla);
			via->rtvia_family = AF_INET6;
			memcpy(via->rtvia_addr, &rt->rt_gw6, alen);
		}
	}

	expires = rt->dst.expires;
	if (expires) {
		unsigned long now = jiffies;

		if (time_before(now, expires))
			expires -= now;
		else
			expires = 0;
	}

	memcpy(metrics, dst_metrics_ptr(&rt->dst), sizeof(metrics));
	if (rt->rt_pmtu && expires)
		metrics[RTAX_MTU - 1] = rt->rt_pmtu;
	if (rt->rt_mtu_locked && expires)
		metrics[RTAX_LOCK - 1] |= BIT(RTAX_MTU);
	if (rtnetlink_put_metrics(skb, metrics) < 0)
		goto nla_put_failure;

	if (fl4) {
		if (fl4->flowi4_mark &&
		    nla_put_u32(skb, RTA_MARK, fl4->flowi4_mark))
			goto nla_put_failure;

		if (!uid_eq(fl4->flowi4_uid, INVALID_UID) &&
		    nla_put_u32(skb, RTA_UID,
				from_kuid_munged(current_user_ns(),
						 fl4->flowi4_uid)))
			goto nla_put_failure;

		if (rt_is_input_route(rt)) {
#ifdef CONFIG_IP_MROUTE
			if (ipv4_is_multicast(dst) &&
			    !ipv4_is_local_multicast(dst) &&
			    IPV4_DEVCONF_ALL_RO(net, MC_FORWARDING)) {
				int err = ipmr_get_route(net, skb,
							 fl4->saddr, fl4->daddr,
							 r, portid);

				if (err <= 0) {
					if (err == 0)
						return 0;
					goto nla_put_failure;
				}
			} else
#endif
				if (nla_put_u32(skb, RTA_IIF, fl4->flowi4_iif))
					goto nla_put_failure;
		}
	}

	error = rt->dst.error;

	if (rtnl_put_cacheinfo(skb, &rt->dst, 0, expires, error) < 0)
		goto nla_put_failure;

	nlmsg_end(skb, nlh);
	return 0;

nla_put_failure:
	nlmsg_cancel(skb, nlh);
	return -EMSGSIZE;
}

static int fnhe_dump_bucket(struct net *net, struct sk_buff *skb,
			    struct netlink_callback *cb, u32 table_id,
			    struct fnhe_hash_bucket *bucket, int genid,
			    int *fa_index, int fa_start, unsigned int flags)
{
	int i;

	for (i = 0; i < FNHE_HASH_SIZE; i++) {
		struct fib_nh_exception *fnhe;

		for (fnhe = rcu_dereference(bucket[i].chain); fnhe;
		     fnhe = rcu_dereference(fnhe->fnhe_next)) {
			struct rtable *rt;
			int err;

			if (*fa_index < fa_start)
				goto next;

			if (fnhe->fnhe_genid != genid)
				goto next;

			if (fnhe->fnhe_expires &&
			    time_after(jiffies, fnhe->fnhe_expires))
				goto next;

			rt = rcu_dereference(fnhe->fnhe_rth_input);
			if (!rt)
				rt = rcu_dereference(fnhe->fnhe_rth_output);
			if (!rt)
				goto next;

			err = rt_fill_info(net, fnhe->fnhe_daddr, 0, rt,
					   table_id, 0, NULL, skb,
					   NETLINK_CB(cb->skb).portid,
					   cb->nlh->nlmsg_seq, flags);
			if (err)
				return err;
next:
			(*fa_index)++;
		}
	}

	return 0;
}

int fib_dump_info_fnhe(struct sk_buff *skb, struct netlink_callback *cb,
		       u32 table_id, struct fib_info *fi,
		       int *fa_index, int fa_start, unsigned int flags)
{
	struct net *net = sock_net(cb->skb->sk);
	int nhsel, genid = fnhe_genid(net);

	for (nhsel = 0; nhsel < fib_info_num_path(fi); nhsel++) {
		struct fib_nh_common *nhc = fib_info_nhc(fi, nhsel);
		struct fnhe_hash_bucket *bucket;
		int err;

		if (nhc->nhc_flags & RTNH_F_DEAD)
			continue;

		rcu_read_lock();
		bucket = rcu_dereference(nhc->nhc_exceptions);
		err = 0;
		if (bucket)
			err = fnhe_dump_bucket(net, skb, cb, table_id, bucket,
					       genid, fa_index, fa_start,
					       flags);
		rcu_read_unlock();
		if (err)
			return err;
	}

	return 0;
}

static struct sk_buff *inet_rtm_getroute_build_skb(__be32 src, __be32 dst,
						   u8 ip_proto, __be16 sport,
						   __be16 dport)
{
	struct sk_buff *skb;
	struct iphdr *iph;

	skb = alloc_skb(NLMSG_GOODSIZE, GFP_KERNEL);
	if (!skb)
		return NULL;

	/* Reserve room for dummy headers, this skb can pass
	 * through good chunk of routing engine.
	 */
	skb_reset_mac_header(skb);
	skb_reset_network_header(skb);
	skb->protocol = htons(ETH_P_IP);
	iph = skb_put(skb, sizeof(struct iphdr));
	iph->protocol = ip_proto;
	iph->saddr = src;
	iph->daddr = dst;
	iph->version = 0x4;
	iph->frag_off = 0;
	iph->ihl = 0x5;
	skb_set_transport_header(skb, skb->len);

	switch (iph->protocol) {
	case IPPROTO_UDP: {
		struct udphdr *udph;

		udph = skb_put_zero(skb, sizeof(struct udphdr));
		udph->source = sport;
		udph->dest = dport;
		udph->len = htons(sizeof(struct udphdr));
		udph->check = 0;
		break;
	}
	case IPPROTO_TCP: {
		struct tcphdr *tcph;

		tcph = skb_put_zero(skb, sizeof(struct tcphdr));
		tcph->source	= sport;
		tcph->dest	= dport;
		tcph->doff	= sizeof(struct tcphdr) / 4;
		tcph->rst = 1;
		tcph->check = ~tcp_v4_check(sizeof(struct tcphdr),
					    src, dst, 0);
		break;
	}
	case IPPROTO_ICMP: {
		struct icmphdr *icmph;

		icmph = skb_put_zero(skb, sizeof(struct icmphdr));
		icmph->type = ICMP_ECHO;
		icmph->code = 0;
	}
	}

	return skb;
}

static int inet_rtm_valid_getroute_req(struct sk_buff *skb,
				       const struct nlmsghdr *nlh,
				       struct nlattr **tb,
				       struct netlink_ext_ack *extack)
{
	struct rtmsg *rtm;
	int i, err;

	if (nlh->nlmsg_len < nlmsg_msg_size(sizeof(*rtm))) {
		NL_SET_ERR_MSG(extack,
			       "ipv4: Invalid header for route get request");
		return -EINVAL;
	}

	if (!netlink_strict_get_check(skb))
		return nlmsg_parse_deprecated(nlh, sizeof(*rtm), tb, RTA_MAX,
					      rtm_ipv4_policy, extack);

	rtm = nlmsg_data(nlh);
	if ((rtm->rtm_src_len && rtm->rtm_src_len != 32) ||
	    (rtm->rtm_dst_len && rtm->rtm_dst_len != 32) ||
	    rtm->rtm_table || rtm->rtm_protocol ||
	    rtm->rtm_scope || rtm->rtm_type) {
		NL_SET_ERR_MSG(extack, "ipv4: Invalid values in header for route get request");
		return -EINVAL;
	}

	if (rtm->rtm_flags & ~(RTM_F_NOTIFY |
			       RTM_F_LOOKUP_TABLE |
			       RTM_F_FIB_MATCH)) {
		NL_SET_ERR_MSG(extack, "ipv4: Unsupported rtm_flags for route get request");
		return -EINVAL;
	}

	err = nlmsg_parse_deprecated_strict(nlh, sizeof(*rtm), tb, RTA_MAX,
					    rtm_ipv4_policy, extack);
	if (err)
		return err;

	if ((tb[RTA_SRC] && !rtm->rtm_src_len) ||
	    (tb[RTA_DST] && !rtm->rtm_dst_len)) {
		NL_SET_ERR_MSG(extack, "ipv4: rtm_src_len and rtm_dst_len must be 32 for IPv4");
		return -EINVAL;
	}

	for (i = 0; i <= RTA_MAX; i++) {
		if (!tb[i])
			continue;

		switch (i) {
		case RTA_IIF:
		case RTA_OIF:
		case RTA_SRC:
		case RTA_DST:
		case RTA_IP_PROTO:
		case RTA_SPORT:
		case RTA_DPORT:
		case RTA_MARK:
		case RTA_UID:
			break;
		default:
			NL_SET_ERR_MSG(extack, "ipv4: Unsupported attribute in route get request");
			return -EINVAL;
		}
	}

	return 0;
}

static int inet_rtm_getroute(struct sk_buff *in_skb, struct nlmsghdr *nlh,
			     struct netlink_ext_ack *extack)
{
	struct net *net = sock_net(in_skb->sk);
	struct nlattr *tb[RTA_MAX+1];
	u32 table_id = RT_TABLE_MAIN;
	__be16 sport = 0, dport = 0;
	struct fib_result res = {};
	u8 ip_proto = IPPROTO_UDP;
	struct rtable *rt = NULL;
	struct sk_buff *skb;
	struct rtmsg *rtm;
	struct flowi4 fl4 = {};
	__be32 dst = 0;
	__be32 src = 0;
	kuid_t uid;
	u32 iif;
	int err;
	int mark;

	err = inet_rtm_valid_getroute_req(in_skb, nlh, tb, extack);
	if (err < 0)
		return err;

	rtm = nlmsg_data(nlh);
	src = nla_get_in_addr_default(tb[RTA_SRC], 0);
	dst = nla_get_in_addr_default(tb[RTA_DST], 0);
	iif = nla_get_u32_default(tb[RTA_IIF], 0);
	mark = nla_get_u32_default(tb[RTA_MARK], 0);
	if (tb[RTA_UID])
		uid = make_kuid(current_user_ns(), nla_get_u32(tb[RTA_UID]));
	else
		uid = (iif ? INVALID_UID : current_uid());

	if (tb[RTA_IP_PROTO]) {
		err = rtm_getroute_parse_ip_proto(tb[RTA_IP_PROTO],
						  &ip_proto, AF_INET, extack);
		if (err)
			return err;
	}

	if (tb[RTA_SPORT])
		sport = nla_get_be16(tb[RTA_SPORT]);

	if (tb[RTA_DPORT])
		dport = nla_get_be16(tb[RTA_DPORT]);

	skb = inet_rtm_getroute_build_skb(src, dst, ip_proto, sport, dport);
	if (!skb)
		return -ENOBUFS;

	fl4.daddr = dst;
	fl4.saddr = src;
	fl4.flowi4_tos = rtm->rtm_tos & INET_DSCP_MASK;
	fl4.flowi4_oif = nla_get_u32_default(tb[RTA_OIF], 0);
	fl4.flowi4_mark = mark;
	fl4.flowi4_uid = uid;
	if (sport)
		fl4.fl4_sport = sport;
	if (dport)
		fl4.fl4_dport = dport;
	fl4.flowi4_proto = ip_proto;

	rcu_read_lock();

	if (iif) {
		struct net_device *dev;

		dev = dev_get_by_index_rcu(net, iif);
		if (!dev) {
			err = -ENODEV;
			goto errout_rcu;
		}

		fl4.flowi4_iif = iif; /* for rt_fill_info */
		skb->dev	= dev;
		skb->mark	= mark;
		err = ip_route_input_rcu(skb, dst, src,
					 inet_dsfield_to_dscp(rtm->rtm_tos),
					 dev, &res) ? -EINVAL : 0;

		rt = skb_rtable(skb);
		if (err == 0 && rt->dst.error)
			err = -rt->dst.error;
	} else {
		fl4.flowi4_iif = LOOPBACK_IFINDEX;
		skb->dev = net->loopback_dev;
		rt = ip_route_output_key_hash_rcu(net, &fl4, &res, skb);
		err = 0;
		if (IS_ERR(rt))
			err = PTR_ERR(rt);
		else
			skb_dst_set(skb, &rt->dst);
	}

	if (err)
		goto errout_rcu;

	if (rtm->rtm_flags & RTM_F_NOTIFY)
		rt->rt_flags |= RTCF_NOTIFY;

	if (rtm->rtm_flags & RTM_F_LOOKUP_TABLE)
		table_id = res.table ? res.table->tb_id : 0;

	/* reset skb for netlink reply msg */
	skb_trim(skb, 0);
	skb_reset_network_header(skb);
	skb_reset_transport_header(skb);
	skb_reset_mac_header(skb);

	if (rtm->rtm_flags & RTM_F_FIB_MATCH) {
		struct fib_rt_info fri;

		if (!res.fi) {
			err = fib_props[res.type].error;
			if (!err)
				err = -EHOSTUNREACH;
			goto errout_rcu;
		}
		fri.fi = res.fi;
		fri.tb_id = table_id;
		fri.dst = res.prefix;
		fri.dst_len = res.prefixlen;
		fri.dscp = res.dscp;
		fri.type = rt->rt_type;
		fri.offload = 0;
		fri.trap = 0;
		fri.offload_failed = 0;
		if (res.fa_head) {
			struct fib_alias *fa;

			hlist_for_each_entry_rcu(fa, res.fa_head, fa_list) {
				u8 slen = 32 - fri.dst_len;

				if (fa->fa_slen == slen &&
				    fa->tb_id == fri.tb_id &&
				    fa->fa_dscp == fri.dscp &&
				    fa->fa_info == res.fi &&
				    fa->fa_type == fri.type) {
					fri.offload = READ_ONCE(fa->offload);
					fri.trap = READ_ONCE(fa->trap);
					fri.offload_failed =
						READ_ONCE(fa->offload_failed);
					break;
				}
			}
		}
		err = fib_dump_info(skb, NETLINK_CB(in_skb).portid,
				    nlh->nlmsg_seq, RTM_NEWROUTE, &fri, 0);
	} else {
		err = rt_fill_info(net, dst, src, rt, table_id, res.dscp, &fl4,
				   skb, NETLINK_CB(in_skb).portid,
				   nlh->nlmsg_seq, 0);
	}
	if (err < 0)
		goto errout_rcu;

	rcu_read_unlock();

	err = rtnl_unicast(skb, net, NETLINK_CB(in_skb).portid);

errout_free:
	return err;
errout_rcu:
	rcu_read_unlock();
	kfree_skb(skb);
	goto errout_free;
}

void ip_rt_multicast_event(struct in_device *in_dev)
{
	rt_cache_flush(dev_net(in_dev->dev));
}

#ifdef CONFIG_SYSCTL
static int ip_rt_gc_interval __read_mostly  = 60 * HZ;
static int ip_rt_gc_min_interval __read_mostly	= HZ / 2;
static int ip_rt_gc_elasticity __read_mostly	= 8;
static int ip_min_valid_pmtu __read_mostly	= IPV4_MIN_MTU;

static int ipv4_sysctl_rtcache_flush(const struct ctl_table *__ctl, int write,
		void *buffer, size_t *lenp, loff_t *ppos)
{
	struct net *net = (struct net *)__ctl->extra1;

	if (write) {
		rt_cache_flush(net);
		fnhe_genid_bump(net);
		return 0;
	}

	return -EINVAL;
}

static struct ctl_table ipv4_route_table[] = {
	{
		.procname	= "gc_thresh",
		.data		= &ipv4_dst_ops.gc_thresh,
		.maxlen		= sizeof(int),
		.mode		= 0644,
		.proc_handler	= proc_dointvec,
	},
	{
		.procname	= "max_size",
		.data		= &ip_rt_max_size,
		.maxlen		= sizeof(int),
		.mode		= 0644,
		.proc_handler	= proc_dointvec,
	},
	{
		/*  Deprecated. Use gc_min_interval_ms */

		.procname	= "gc_min_interval",
		.data		= &ip_rt_gc_min_interval,
		.maxlen		= sizeof(int),
		.mode		= 0644,
		.proc_handler	= proc_dointvec_jiffies,
	},
	{
		.procname	= "gc_min_interval_ms",
		.data		= &ip_rt_gc_min_interval,
		.maxlen		= sizeof(int),
		.mode		= 0644,
		.proc_handler	= proc_dointvec_ms_jiffies,
	},
	{
		.procname	= "gc_timeout",
		.data		= &ip_rt_gc_timeout,
		.maxlen		= sizeof(int),
		.mode		= 0644,
		.proc_handler	= proc_dointvec_jiffies,
	},
	{
		.procname	= "gc_interval",
		.data		= &ip_rt_gc_interval,
		.maxlen		= sizeof(int),
		.mode		= 0644,
		.proc_handler	= proc_dointvec_jiffies,
	},
	{
		.procname	= "redirect_load",
		.data		= &ip_rt_redirect_load,
		.maxlen		= sizeof(int),
		.mode		= 0644,
		.proc_handler	= proc_dointvec,
	},
	{
		.procname	= "redirect_number",
		.data		= &ip_rt_redirect_number,
		.maxlen		= sizeof(int),
		.mode		= 0644,
		.proc_handler	= proc_dointvec,
	},
	{
		.procname	= "redirect_silence",
		.data		= &ip_rt_redirect_silence,
		.maxlen		= sizeof(int),
		.mode		= 0644,
		.proc_handler	= proc_dointvec,
	},
	{
		.procname	= "error_cost",
		.data		= &ip_rt_error_cost,
		.maxlen		= sizeof(int),
		.mode		= 0644,
		.proc_handler	= proc_dointvec,
	},
	{
		.procname	= "error_burst",
		.data		= &ip_rt_error_burst,
		.maxlen		= sizeof(int),
		.mode		= 0644,
		.proc_handler	= proc_dointvec,
	},
	{
		.procname	= "gc_elasticity",
		.data		= &ip_rt_gc_elasticity,
		.maxlen		= sizeof(int),
		.mode		= 0644,
		.proc_handler	= proc_dointvec,
	},
};

static const char ipv4_route_flush_procname[] = "flush";

static struct ctl_table ipv4_route_netns_table[] = {
	{
		.procname	= ipv4_route_flush_procname,
		.maxlen		= sizeof(int),
		.mode		= 0200,
		.proc_handler	= ipv4_sysctl_rtcache_flush,
	},
	{
		.procname       = "min_pmtu",
		.data           = &init_net.ipv4.ip_rt_min_pmtu,
		.maxlen         = sizeof(int),
		.mode           = 0644,
		.proc_handler   = proc_dointvec_minmax,
		.extra1         = &ip_min_valid_pmtu,
	},
	{
		.procname       = "mtu_expires",
		.data           = &init_net.ipv4.ip_rt_mtu_expires,
		.maxlen         = sizeof(int),
		.mode           = 0644,
		.proc_handler   = proc_dointvec_jiffies,
	},
	{
		.procname   = "min_adv_mss",
		.data       = &init_net.ipv4.ip_rt_min_advmss,
		.maxlen     = sizeof(int),
		.mode       = 0644,
		.proc_handler   = proc_dointvec,
	},
};

static __net_init int sysctl_route_net_init(struct net *net)
{
	struct ctl_table *tbl;
	size_t table_size = ARRAY_SIZE(ipv4_route_netns_table);

	tbl = ipv4_route_netns_table;
	if (!net_eq(net, &init_net)) {
		int i;

		tbl = kmemdup(tbl, sizeof(ipv4_route_netns_table), GFP_KERNEL);
		if (!tbl)
			goto err_dup;

		/* Don't export non-whitelisted sysctls to unprivileged users */
		if (net->user_ns != &init_user_ns) {
			if (tbl[0].procname != ipv4_route_flush_procname)
				table_size = 0;
		}

		/* Update the variables to point into the current struct net
		 * except for the first element flush
		 */
		for (i = 1; i < table_size; i++)
			tbl[i].data += (void *)net - (void *)&init_net;
	}
	tbl[0].extra1 = net;

	net->ipv4.route_hdr = register_net_sysctl_sz(net, "net/ipv4/route",
						     tbl, table_size);
	if (!net->ipv4.route_hdr)
		goto err_reg;
	return 0;

err_reg:
	if (tbl != ipv4_route_netns_table)
		kfree(tbl);
err_dup:
	return -ENOMEM;
}

static __net_exit void sysctl_route_net_exit(struct net *net)
{
	const struct ctl_table *tbl;

	tbl = net->ipv4.route_hdr->ctl_table_arg;
	unregister_net_sysctl_table(net->ipv4.route_hdr);
	BUG_ON(tbl == ipv4_route_netns_table);
	kfree(tbl);
}

static __net_initdata struct pernet_operations sysctl_route_ops = {
	.init = sysctl_route_net_init,
	.exit = sysctl_route_net_exit,
};
#endif

static __net_init int netns_ip_rt_init(struct net *net)
{
	/* Set default value for namespaceified sysctls */
	net->ipv4.ip_rt_min_pmtu = DEFAULT_MIN_PMTU;
	net->ipv4.ip_rt_mtu_expires = DEFAULT_MTU_EXPIRES;
	net->ipv4.ip_rt_min_advmss = DEFAULT_MIN_ADVMSS;
	return 0;
}

static struct pernet_operations __net_initdata ip_rt_ops = {
	.init = netns_ip_rt_init,
};

static __net_init int rt_genid_init(struct net *net)
{
	atomic_set(&net->ipv4.rt_genid, 0);
	atomic_set(&net->fnhe_genid, 0);
	atomic_set(&net->ipv4.dev_addr_genid, get_random_u32());
	return 0;
}

static __net_initdata struct pernet_operations rt_genid_ops = {
	.init = rt_genid_init,
};

static int __net_init ipv4_inetpeer_init(struct net *net)
{
	struct inet_peer_base *bp = kmalloc(sizeof(*bp), GFP_KERNEL);

	if (!bp)
		return -ENOMEM;
	inet_peer_base_init(bp);
	net->ipv4.peers = bp;
	return 0;
}

static void __net_exit ipv4_inetpeer_exit(struct net *net)
{
	struct inet_peer_base *bp = net->ipv4.peers;

	net->ipv4.peers = NULL;
	inetpeer_invalidate_tree(bp);
	kfree(bp);
}

static __net_initdata struct pernet_operations ipv4_inetpeer_ops = {
	.init	=	ipv4_inetpeer_init,
	.exit	=	ipv4_inetpeer_exit,
};

#ifdef CONFIG_IP_ROUTE_CLASSID
struct ip_rt_acct __percpu *ip_rt_acct __read_mostly;
#endif /* CONFIG_IP_ROUTE_CLASSID */

static const struct rtnl_msg_handler ip_rt_rtnl_msg_handlers[] __initconst = {
	{.protocol = PF_INET, .msgtype = RTM_GETROUTE,
	 .doit = inet_rtm_getroute, .flags = RTNL_FLAG_DOIT_UNLOCKED},
};

int __init ip_rt_init(void)
{
	void *idents_hash;
	int cpu;

	/* For modern hosts, this will use 2 MB of memory */
	idents_hash = alloc_large_system_hash("IP idents",
					      sizeof(*ip_idents) + sizeof(*ip_tstamps),
					      0,
					      16, /* one bucket per 64 KB */
					      HASH_ZERO,
					      NULL,
					      &ip_idents_mask,
					      2048,
					      256*1024);

	ip_idents = idents_hash;

	get_random_bytes(ip_idents, (ip_idents_mask + 1) * sizeof(*ip_idents));

	ip_tstamps = idents_hash + (ip_idents_mask + 1) * sizeof(*ip_idents);

	for_each_possible_cpu(cpu) {
		struct uncached_list *ul = &per_cpu(rt_uncached_list, cpu);

		INIT_LIST_HEAD(&ul->head);
		spin_lock_init(&ul->lock);
	}
#ifdef CONFIG_IP_ROUTE_CLASSID
	ip_rt_acct = __alloc_percpu(256 * sizeof(struct ip_rt_acct), __alignof__(struct ip_rt_acct));
	if (!ip_rt_acct)
		panic("IP: failed to allocate ip_rt_acct\n");
#endif

	ipv4_dst_ops.kmem_cachep = KMEM_CACHE(rtable,
					      SLAB_HWCACHE_ALIGN | SLAB_PANIC);

	ipv4_dst_blackhole_ops.kmem_cachep = ipv4_dst_ops.kmem_cachep;

	if (dst_entries_init(&ipv4_dst_ops) < 0)
		panic("IP: failed to allocate ipv4_dst_ops counter\n");

	if (dst_entries_init(&ipv4_dst_blackhole_ops) < 0)
		panic("IP: failed to allocate ipv4_dst_blackhole_ops counter\n");

	ipv4_dst_ops.gc_thresh = ~0;
	ip_rt_max_size = INT_MAX;

	devinet_init();
	ip_fib_init();

	if (ip_rt_proc_init())
		pr_err("Unable to create route proc files\n");
#ifdef CONFIG_XFRM
	xfrm_init();
	xfrm4_init();
#endif
	rtnl_register_many(ip_rt_rtnl_msg_handlers);

#ifdef CONFIG_SYSCTL
	register_pernet_subsys(&sysctl_route_ops);
#endif
	register_pernet_subsys(&ip_rt_ops);
	register_pernet_subsys(&rt_genid_ops);
	register_pernet_subsys(&ipv4_inetpeer_ops);
	return 0;
}

#ifdef CONFIG_SYSCTL
/*
 * We really need to sanitize the damn ipv4 init order, then all
 * this nonsense will go away.
 */
void __init ip_static_sysctl_init(void)
{
	register_net_sysctl(&init_net, "net/ipv4/route", ipv4_route_table);
}
#endif