net/ipv6/route.c

/*
 *	Linux INET6 implementation
 *	FIB front-end.
 *
 *	Authors:
 *	Pedro Roque		<roque@di.fc.ul.pt>
 *
 *	This program is free software; you can redistribute it and/or
 *      modify it under the terms of the GNU General Public License
 *      as published by the Free Software Foundation; either version
 *      2 of the License, or (at your option) any later version.
 */

/*	Changes:
 *
 *	YOSHIFUJI Hideaki @USAGI
 *		reworked default router selection.
 *		- respect outgoing interface
 *		- select from (probably) reachable routers (i.e.
 *		routers in REACHABLE, STALE, DELAY or PROBE states).
 *		- always select the same router if it is (probably)
 *		reachable.  otherwise, round-robin the list.
 *	Ville Nuorvala
 *		Fixed routing subtrees.
 */

#define pr_fmt(fmt) "IPv6: " fmt

#include <linux/capability.h>
#include <linux/errno.h>
#include <linux/export.h>
#include <linux/types.h>
#include <linux/times.h>
#include <linux/socket.h>
#include <linux/sockios.h>
#include <linux/net.h>
#include <linux/route.h>
#include <linux/netdevice.h>
#include <linux/in6.h>
#include <linux/mroute6.h>
#include <linux/init.h>
#include <linux/if_arp.h>
#include <linux/proc_fs.h>
#include <linux/seq_file.h>
#include <linux/nsproxy.h>
#include <linux/slab.h>
#include <linux/jhash.h>
#include <net/net_namespace.h>
#include <net/snmp.h>
#include <net/ipv6.h>
#include <net/ip6_fib.h>
#include <net/ip6_route.h>
#include <net/ndisc.h>
#include <net/addrconf.h>
#include <net/tcp.h>
#include <linux/rtnetlink.h>
#include <net/dst.h>
#include <net/dst_metadata.h>
#include <net/xfrm.h>
#include <net/netevent.h>
#include <net/netlink.h>
#include <net/rtnh.h>
#include <net/lwtunnel.h>
#include <net/ip_tunnels.h>
#include <net/l3mdev.h>
#include <net/ip.h>
#include <linux/uaccess.h>

#ifdef CONFIG_SYSCTL
#include <linux/sysctl.h>
#endif

static int ip6_rt_type_to_error(u8 fib6_type);

#define CREATE_TRACE_POINTS
#include <trace/events/fib6.h>
EXPORT_TRACEPOINT_SYMBOL_GPL(fib6_table_lookup);
#undef CREATE_TRACE_POINTS

enum rt6_nud_state {
	RT6_NUD_FAIL_HARD = -3,
	RT6_NUD_FAIL_PROBE = -2,
	RT6_NUD_FAIL_DO_RR = -1,
	RT6_NUD_SUCCEED = 1
};

static struct dst_entry	*ip6_dst_check(struct dst_entry *dst, u32 cookie);
static unsigned int	 ip6_default_advmss(const struct dst_entry *dst);
static unsigned int	 ip6_mtu(const struct dst_entry *dst);
static struct dst_entry *ip6_negative_advice(struct dst_entry *);
static void		ip6_dst_destroy(struct dst_entry *);
static void		ip6_dst_ifdown(struct dst_entry *,
				       struct net_device *dev, int how);
static int		 ip6_dst_gc(struct dst_ops *ops);

static int		ip6_pkt_discard(struct sk_buff *skb);
static int		ip6_pkt_discard_out(struct net *net, struct sock *sk, struct sk_buff *skb);
static int		ip6_pkt_prohibit(struct sk_buff *skb);
static int		ip6_pkt_prohibit_out(struct net *net, struct sock *sk, struct sk_buff *skb);
static void		ip6_link_failure(struct sk_buff *skb);
static void		ip6_rt_update_pmtu(struct dst_entry *dst, struct sock *sk,
					   struct sk_buff *skb, u32 mtu);
static void		rt6_do_redirect(struct dst_entry *dst, struct sock *sk,
					struct sk_buff *skb);
static int rt6_score_route(const struct fib6_nh *nh, u32 fib6_flags, int oif,
			   int strict);
static size_t rt6_nlmsg_size(struct fib6_info *rt);
static int rt6_fill_node(struct net *net, struct sk_buff *skb,
			 struct fib6_info *rt, struct dst_entry *dst,
			 struct in6_addr *dest, struct in6_addr *src,
			 int iif, int type, u32 portid, u32 seq,
			 unsigned int flags);
static struct rt6_info *rt6_find_cached_rt(const struct fib6_result *res,
					   struct in6_addr *daddr,
					   struct in6_addr *saddr);

#ifdef CONFIG_IPV6_ROUTE_INFO
static struct fib6_info *rt6_add_route_info(struct net *net,
					   const struct in6_addr *prefix, int prefixlen,
					   const struct in6_addr *gwaddr,
					   struct net_device *dev,
					   unsigned int pref);
static struct fib6_info *rt6_get_route_info(struct net *net,
					   const struct in6_addr *prefix, int prefixlen,
					   const struct in6_addr *gwaddr,
					   struct net_device *dev);
#endif

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

static DEFINE_PER_CPU_ALIGNED(struct uncached_list, rt6_uncached_list);

void rt6_uncached_list_add(struct rt6_info *rt)
{
	struct uncached_list *ul = raw_cpu_ptr(&rt6_uncached_list);

	rt->rt6i_uncached_list = ul;

	spin_lock_bh(&ul->lock);
	list_add_tail(&rt->rt6i_uncached, &ul->head);
	spin_unlock_bh(&ul->lock);
}

void rt6_uncached_list_del(struct rt6_info *rt)
{
	if (!list_empty(&rt->rt6i_uncached)) {
		struct uncached_list *ul = rt->rt6i_uncached_list;
		struct net *net = dev_net(rt->dst.dev);

		spin_lock_bh(&ul->lock);
		list_del(&rt->rt6i_uncached);
		atomic_dec(&net->ipv6.rt6_stats->fib_rt_uncache);
		spin_unlock_bh(&ul->lock);
	}
}

static void rt6_uncached_list_flush_dev(struct net *net, struct net_device *dev)
{
	struct net_device *loopback_dev = net->loopback_dev;
	int cpu;

	if (dev == loopback_dev)
		return;

	for_each_possible_cpu(cpu) {
		struct uncached_list *ul = per_cpu_ptr(&rt6_uncached_list, cpu);
		struct rt6_info *rt;

		spin_lock_bh(&ul->lock);
		list_for_each_entry(rt, &ul->head, rt6i_uncached) {
			struct inet6_dev *rt_idev = rt->rt6i_idev;
			struct net_device *rt_dev = rt->dst.dev;

			if (rt_idev->dev == dev) {
				rt->rt6i_idev = in6_dev_get(loopback_dev);
				in6_dev_put(rt_idev);
			}

			if (rt_dev == dev) {
				rt->dst.dev = loopback_dev;
				dev_hold(rt->dst.dev);
				dev_put(rt_dev);
			}
		}
		spin_unlock_bh(&ul->lock);
	}
}

static inline const void *choose_neigh_daddr(const struct in6_addr *p,
					     struct sk_buff *skb,
					     const void *daddr)
{
	if (!ipv6_addr_any(p))
		return (const void *) p;
	else if (skb)
		return &ipv6_hdr(skb)->daddr;
	return daddr;
}

struct neighbour *ip6_neigh_lookup(const struct in6_addr *gw,
				   struct net_device *dev,
				   struct sk_buff *skb,
				   const void *daddr)
{
	struct neighbour *n;

	daddr = choose_neigh_daddr(gw, skb, daddr);
	n = __ipv6_neigh_lookup(dev, daddr);
	if (n)
		return n;

	n = neigh_create(&nd_tbl, daddr, dev);
	return IS_ERR(n) ? NULL : n;
}

static struct neighbour *ip6_dst_neigh_lookup(const struct dst_entry *dst,
					      struct sk_buff *skb,
					      const void *daddr)
{
	const struct rt6_info *rt = container_of(dst, struct rt6_info, dst);

	return ip6_neigh_lookup(&rt->rt6i_gateway, dst->dev, skb, daddr);
}

static void ip6_confirm_neigh(const struct dst_entry *dst, const void *daddr)
{
	struct net_device *dev = dst->dev;
	struct rt6_info *rt = (struct rt6_info *)dst;

	daddr = choose_neigh_daddr(&rt->rt6i_gateway, NULL, daddr);
	if (!daddr)
		return;
	if (dev->flags & (IFF_NOARP | IFF_LOOPBACK))
		return;
	if (ipv6_addr_is_multicast((const struct in6_addr *)daddr))
		return;
	__ipv6_confirm_neigh(dev, daddr);
}

static struct dst_ops ip6_dst_ops_template = {
	.family			=	AF_INET6,
	.gc			=	ip6_dst_gc,
	.gc_thresh		=	1024,
	.check			=	ip6_dst_check,
	.default_advmss		=	ip6_default_advmss,
	.mtu			=	ip6_mtu,
	.cow_metrics		=	dst_cow_metrics_generic,
	.destroy		=	ip6_dst_destroy,
	.ifdown			=	ip6_dst_ifdown,
	.negative_advice	=	ip6_negative_advice,
	.link_failure		=	ip6_link_failure,
	.update_pmtu		=	ip6_rt_update_pmtu,
	.redirect		=	rt6_do_redirect,
	.local_out		=	__ip6_local_out,
	.neigh_lookup		=	ip6_dst_neigh_lookup,
	.confirm_neigh		=	ip6_confirm_neigh,
};

static unsigned int ip6_blackhole_mtu(const struct dst_entry *dst)
{
	unsigned int mtu = dst_metric_raw(dst, RTAX_MTU);

	return mtu ? : dst->dev->mtu;
}

static void ip6_rt_blackhole_update_pmtu(struct dst_entry *dst, struct sock *sk,
					 struct sk_buff *skb, u32 mtu)
{
}

static void ip6_rt_blackhole_redirect(struct dst_entry *dst, struct sock *sk,
				      struct sk_buff *skb)
{
}

static struct dst_ops ip6_dst_blackhole_ops = {
	.family			=	AF_INET6,
	.destroy		=	ip6_dst_destroy,
	.check			=	ip6_dst_check,
	.mtu			=	ip6_blackhole_mtu,
	.default_advmss		=	ip6_default_advmss,
	.update_pmtu		=	ip6_rt_blackhole_update_pmtu,
	.redirect		=	ip6_rt_blackhole_redirect,
	.cow_metrics		=	dst_cow_metrics_generic,
	.neigh_lookup		=	ip6_dst_neigh_lookup,
};

static const u32 ip6_template_metrics[RTAX_MAX] = {
	[RTAX_HOPLIMIT - 1] = 0,
};

static const struct fib6_info fib6_null_entry_template = {
	.fib6_flags	= (RTF_REJECT | RTF_NONEXTHOP),
	.fib6_protocol  = RTPROT_KERNEL,
	.fib6_metric	= ~(u32)0,
	.fib6_ref	= REFCOUNT_INIT(1),
	.fib6_type	= RTN_UNREACHABLE,
	.fib6_metrics	= (struct dst_metrics *)&dst_default_metrics,
};

static const struct rt6_info ip6_null_entry_template = {
	.dst = {
		.__refcnt	= ATOMIC_INIT(1),
		.__use		= 1,
		.obsolete	= DST_OBSOLETE_FORCE_CHK,
		.error		= -ENETUNREACH,
		.input		= ip6_pkt_discard,
		.output		= ip6_pkt_discard_out,
	},
	.rt6i_flags	= (RTF_REJECT | RTF_NONEXTHOP),
};

#ifdef CONFIG_IPV6_MULTIPLE_TABLES

static const struct rt6_info ip6_prohibit_entry_template = {
	.dst = {
		.__refcnt	= ATOMIC_INIT(1),
		.__use		= 1,
		.obsolete	= DST_OBSOLETE_FORCE_CHK,
		.error		= -EACCES,
		.input		= ip6_pkt_prohibit,
		.output		= ip6_pkt_prohibit_out,
	},
	.rt6i_flags	= (RTF_REJECT | RTF_NONEXTHOP),
};

static const struct rt6_info ip6_blk_hole_entry_template = {
	.dst = {
		.__refcnt	= ATOMIC_INIT(1),
		.__use		= 1,
		.obsolete	= DST_OBSOLETE_FORCE_CHK,
		.error		= -EINVAL,
		.input		= dst_discard,
		.output		= dst_discard_out,
	},
	.rt6i_flags	= (RTF_REJECT | RTF_NONEXTHOP),
};

#endif

static void rt6_info_init(struct rt6_info *rt)
{
	struct dst_entry *dst = &rt->dst;

	memset(dst + 1, 0, sizeof(*rt) - sizeof(*dst));
	INIT_LIST_HEAD(&rt->rt6i_uncached);
}

/* allocate dst with ip6_dst_ops */
struct rt6_info *ip6_dst_alloc(struct net *net, struct net_device *dev,
			       int flags)
{
	struct rt6_info *rt = dst_alloc(&net->ipv6.ip6_dst_ops, dev,
					1, DST_OBSOLETE_FORCE_CHK, flags);

	if (rt) {
		rt6_info_init(rt);
		atomic_inc(&net->ipv6.rt6_stats->fib_rt_alloc);
	}

	return rt;
}
EXPORT_SYMBOL(ip6_dst_alloc);

static void ip6_dst_destroy(struct dst_entry *dst)
{
	struct rt6_info *rt = (struct rt6_info *)dst;
	struct fib6_info *from;
	struct inet6_dev *idev;

	ip_dst_metrics_put(dst);
	rt6_uncached_list_del(rt);

	idev = rt->rt6i_idev;
	if (idev) {
		rt->rt6i_idev = NULL;
		in6_dev_put(idev);
	}

	from = xchg((__force struct fib6_info **)&rt->from, NULL);
	fib6_info_release(from);
}

static void ip6_dst_ifdown(struct dst_entry *dst, struct net_device *dev,
			   int how)
{
	struct rt6_info *rt = (struct rt6_info *)dst;
	struct inet6_dev *idev = rt->rt6i_idev;
	struct net_device *loopback_dev =
		dev_net(dev)->loopback_dev;

	if (idev && idev->dev != loopback_dev) {
		struct inet6_dev *loopback_idev = in6_dev_get(loopback_dev);
		if (loopback_idev) {
			rt->rt6i_idev = loopback_idev;
			in6_dev_put(idev);
		}
	}
}

static bool __rt6_check_expired(const struct rt6_info *rt)
{
	if (rt->rt6i_flags & RTF_EXPIRES)
		return time_after(jiffies, rt->dst.expires);
	else
		return false;
}

static bool rt6_check_expired(const struct rt6_info *rt)
{
	struct fib6_info *from;

	from = rcu_dereference(rt->from);

	if (rt->rt6i_flags & RTF_EXPIRES) {
		if (time_after(jiffies, rt->dst.expires))
			return true;
	} else if (from) {
		return rt->dst.obsolete != DST_OBSOLETE_FORCE_CHK ||
			fib6_check_expired(from);
	}
	return false;
}

void fib6_select_path(const struct net *net, struct fib6_result *res,
		      struct flowi6 *fl6, int oif, bool have_oif_match,
		      const struct sk_buff *skb, int strict)
{
	struct fib6_info *sibling, *next_sibling;
	struct fib6_info *match = res->f6i;

	if (!match->fib6_nsiblings || have_oif_match)
		goto out;

	/* We might have already computed the hash for ICMPv6 errors. In such
	 * case it will always be non-zero. Otherwise now is the time to do it.
	 */
	if (!fl6->mp_hash)
		fl6->mp_hash = rt6_multipath_hash(net, fl6, skb, NULL);

	if (fl6->mp_hash <= atomic_read(&match->fib6_nh.fib_nh_upper_bound))
		goto out;

	list_for_each_entry_safe(sibling, next_sibling, &match->fib6_siblings,
				 fib6_siblings) {
		const struct fib6_nh *nh = &sibling->fib6_nh;
		int nh_upper_bound;

		nh_upper_bound = atomic_read(&nh->fib_nh_upper_bound);
		if (fl6->mp_hash > nh_upper_bound)
			continue;
		if (rt6_score_route(nh, sibling->fib6_flags, oif, strict) < 0)
			break;
		match = sibling;
		break;
	}

out:
	res->f6i = match;
	res->nh = &match->fib6_nh;
}

/*
 *	Route lookup. rcu_read_lock() should be held.
 */

static bool __rt6_device_match(struct net *net, const struct fib6_nh *nh,
			       const struct in6_addr *saddr, int oif, int flags)
{
	const struct net_device *dev;

	if (nh->fib_nh_flags & RTNH_F_DEAD)
		return false;

	dev = nh->fib_nh_dev;
	if (oif) {
		if (dev->ifindex == oif)
			return true;
	} else {
		if (ipv6_chk_addr(net, saddr, dev,
				  flags & RT6_LOOKUP_F_IFACE))
			return true;
	}

	return false;
}

static void rt6_device_match(struct net *net, struct fib6_result *res,
			     const struct in6_addr *saddr, int oif, int flags)
{
	struct fib6_info *f6i = res->f6i;
	struct fib6_info *spf6i;
	struct fib6_nh *nh;

	if (!oif && ipv6_addr_any(saddr)) {
		nh = &f6i->fib6_nh;
		if (!(nh->fib_nh_flags & RTNH_F_DEAD))
			goto out;
	}

	for (spf6i = f6i; spf6i; spf6i = rcu_dereference(spf6i->fib6_next)) {
		nh = &spf6i->fib6_nh;
		if (__rt6_device_match(net, nh, saddr, oif, flags)) {
			res->f6i = spf6i;
			goto out;
		}
	}

	if (oif && flags & RT6_LOOKUP_F_IFACE) {
		res->f6i = net->ipv6.fib6_null_entry;
		nh = &res->f6i->fib6_nh;
		goto out;
	}

	nh = &f6i->fib6_nh;
	if (nh->fib_nh_flags & RTNH_F_DEAD) {
		res->f6i = net->ipv6.fib6_null_entry;
		nh = &res->f6i->fib6_nh;
	}
out:
	res->nh = nh;
	res->fib6_type = res->f6i->fib6_type;
	res->fib6_flags = res->f6i->fib6_flags;
}

#ifdef CONFIG_IPV6_ROUTER_PREF
struct __rt6_probe_work {
	struct work_struct work;
	struct in6_addr target;
	struct net_device *dev;
};

static void rt6_probe_deferred(struct work_struct *w)
{
	struct in6_addr mcaddr;
	struct __rt6_probe_work *work =
		container_of(w, struct __rt6_probe_work, work);

	addrconf_addr_solict_mult(&work->target, &mcaddr);
	ndisc_send_ns(work->dev, &work->target, &mcaddr, NULL, 0);
	dev_put(work->dev);
	kfree(work);
}

static void rt6_probe(struct fib6_nh *fib6_nh)
{
	struct __rt6_probe_work *work = NULL;
	const struct in6_addr *nh_gw;
	struct neighbour *neigh;
	struct net_device *dev;
	struct inet6_dev *idev;

	/*
	 * Okay, this does not seem to be appropriate
	 * for now, however, we need to check if it
	 * is really so; aka Router Reachability Probing.
	 *
	 * Router Reachability Probe MUST be rate-limited
	 * to no more than one per minute.
	 */
	if (fib6_nh->fib_nh_gw_family)
		return;

	nh_gw = &fib6_nh->fib_nh_gw6;
	dev = fib6_nh->fib_nh_dev;
	rcu_read_lock_bh();
	idev = __in6_dev_get(dev);
	neigh = __ipv6_neigh_lookup_noref(dev, nh_gw);
	if (neigh) {
		if (neigh->nud_state & NUD_VALID)
			goto out;

		write_lock(&neigh->lock);
		if (!(neigh->nud_state & NUD_VALID) &&
		    time_after(jiffies,
			       neigh->updated + idev->cnf.rtr_probe_interval)) {
			work = kmalloc(sizeof(*work), GFP_ATOMIC);
			if (work)
				__neigh_set_probe_once(neigh);
		}
		write_unlock(&neigh->lock);
	} else if (time_after(jiffies, fib6_nh->last_probe +
				       idev->cnf.rtr_probe_interval)) {
		work = kmalloc(sizeof(*work), GFP_ATOMIC);
	}

	if (work) {
		fib6_nh->last_probe = jiffies;
		INIT_WORK(&work->work, rt6_probe_deferred);
		work->target = *nh_gw;
		dev_hold(dev);
		work->dev = dev;
		schedule_work(&work->work);
	}

out:
	rcu_read_unlock_bh();
}
#else
static inline void rt6_probe(struct fib6_nh *fib6_nh)
{
}
#endif

/*
 * Default Router Selection (RFC 2461 6.3.6)
 */
static enum rt6_nud_state rt6_check_neigh(const struct fib6_nh *fib6_nh)
{
	enum rt6_nud_state ret = RT6_NUD_FAIL_HARD;
	struct neighbour *neigh;

	rcu_read_lock_bh();
	neigh = __ipv6_neigh_lookup_noref(fib6_nh->fib_nh_dev,
					  &fib6_nh->fib_nh_gw6);
	if (neigh) {
		read_lock(&neigh->lock);
		if (neigh->nud_state & NUD_VALID)
			ret = RT6_NUD_SUCCEED;
#ifdef CONFIG_IPV6_ROUTER_PREF
		else if (!(neigh->nud_state & NUD_FAILED))
			ret = RT6_NUD_SUCCEED;
		else
			ret = RT6_NUD_FAIL_PROBE;
#endif
		read_unlock(&neigh->lock);
	} else {
		ret = IS_ENABLED(CONFIG_IPV6_ROUTER_PREF) ?
		      RT6_NUD_SUCCEED : RT6_NUD_FAIL_DO_RR;
	}
	rcu_read_unlock_bh();

	return ret;
}

static int rt6_score_route(const struct fib6_nh *nh, u32 fib6_flags, int oif,
			   int strict)
{
	int m = 0;

	if (!oif || nh->fib_nh_dev->ifindex == oif)
		m = 2;

	if (!m && (strict & RT6_LOOKUP_F_IFACE))
		return RT6_NUD_FAIL_HARD;
#ifdef CONFIG_IPV6_ROUTER_PREF
	m |= IPV6_DECODE_PREF(IPV6_EXTRACT_PREF(fib6_flags)) << 2;
#endif
	if ((strict & RT6_LOOKUP_F_REACHABLE) &&
	    !(fib6_flags & RTF_NONEXTHOP) && nh->fib_nh_gw_family) {
		int n = rt6_check_neigh(nh);
		if (n < 0)
			return n;
	}
	return m;
}

static bool find_match(struct fib6_nh *nh, u32 fib6_flags,
		       int oif, int strict, int *mpri, bool *do_rr)
{
	bool match_do_rr = false;
	bool rc = false;
	int m;

	if (nh->fib_nh_flags & RTNH_F_DEAD)
		goto out;

	if (ip6_ignore_linkdown(nh->fib_nh_dev) &&
	    nh->fib_nh_flags & RTNH_F_LINKDOWN &&
	    !(strict & RT6_LOOKUP_F_IGNORE_LINKSTATE))
		goto out;

	m = rt6_score_route(nh, fib6_flags, oif, strict);
	if (m == RT6_NUD_FAIL_DO_RR) {
		match_do_rr = true;
		m = 0; /* lowest valid score */
	} else if (m == RT6_NUD_FAIL_HARD) {
		goto out;
	}

	if (strict & RT6_LOOKUP_F_REACHABLE)
		rt6_probe(nh);

	/* note that m can be RT6_NUD_FAIL_PROBE at this point */
	if (m > *mpri) {
		*do_rr = match_do_rr;
		*mpri = m;
		rc = true;
	}
out:
	return rc;
}

static void __find_rr_leaf(struct fib6_info *f6i_start,
			   struct fib6_info *nomatch, u32 metric,
			   struct fib6_result *res, struct fib6_info **cont,
			   int oif, int strict, bool *do_rr, int *mpri)
{
	struct fib6_info *f6i;

	for (f6i = f6i_start;
	     f6i && f6i != nomatch;
	     f6i = rcu_dereference(f6i->fib6_next)) {
		struct fib6_nh *nh;

		if (cont && f6i->fib6_metric != metric) {
			*cont = f6i;
			return;
		}

		if (fib6_check_expired(f6i))
			continue;

		nh = &f6i->fib6_nh;
		if (find_match(nh, f6i->fib6_flags, oif, strict, mpri, do_rr)) {
			res->f6i = f6i;
			res->nh = nh;
			res->fib6_flags = f6i->fib6_flags;
			res->fib6_type = f6i->fib6_type;
		}
	}
}

static void find_rr_leaf(struct fib6_node *fn, struct fib6_info *leaf,
			 struct fib6_info *rr_head, int oif, int strict,
			 bool *do_rr, struct fib6_result *res)
{
	u32 metric = rr_head->fib6_metric;
	struct fib6_info *cont = NULL;
	int mpri = -1;

	__find_rr_leaf(rr_head, NULL, metric, res, &cont,
		       oif, strict, do_rr, &mpri);

	__find_rr_leaf(leaf, rr_head, metric, res, &cont,
		       oif, strict, do_rr, &mpri);

	if (res->f6i || !cont)
		return;

	__find_rr_leaf(cont, NULL, metric, res, NULL,
		       oif, strict, do_rr, &mpri);
}

static void rt6_select(struct net *net, struct fib6_node *fn, int oif,
		       struct fib6_result *res, int strict)
{
	struct fib6_info *leaf = rcu_dereference(fn->leaf);
	struct fib6_info *rt0;
	bool do_rr = false;
	int key_plen;

	/* make sure this function or its helpers sets f6i */
	res->f6i = NULL;

	if (!leaf || leaf == net->ipv6.fib6_null_entry)
		goto out;

	rt0 = rcu_dereference(fn->rr_ptr);
	if (!rt0)
		rt0 = leaf;

	/* Double check to make sure fn is not an intermediate node
	 * and fn->leaf does not points to its child's leaf
	 * (This might happen if all routes under fn are deleted from
	 * the tree and fib6_repair_tree() is called on the node.)
	 */
	key_plen = rt0->fib6_dst.plen;
#ifdef CONFIG_IPV6_SUBTREES
	if (rt0->fib6_src.plen)
		key_plen = rt0->fib6_src.plen;
#endif
	if (fn->fn_bit != key_plen)
		goto out;

	find_rr_leaf(fn, leaf, rt0, oif, strict, &do_rr, res);
	if (do_rr) {
		struct fib6_info *next = rcu_dereference(rt0->fib6_next);

		/* no entries matched; do round-robin */
		if (!next || next->fib6_metric != rt0->fib6_metric)
			next = leaf;

		if (next != rt0) {
			spin_lock_bh(&leaf->fib6_table->tb6_lock);
			/* make sure next is not being deleted from the tree */
			if (next->fib6_node)
				rcu_assign_pointer(fn->rr_ptr, next);
			spin_unlock_bh(&leaf->fib6_table->tb6_lock);
		}
	}

out:
	if (!res->f6i) {
		res->f6i = net->ipv6.fib6_null_entry;
		res->nh = &res->f6i->fib6_nh;
		res->fib6_flags = res->f6i->fib6_flags;
		res->fib6_type = res->f6i->fib6_type;
	}
}

static bool rt6_is_gw_or_nonexthop(const struct fib6_result *res)
{
	return (res->f6i->fib6_flags & RTF_NONEXTHOP) ||
	       res->nh->fib_nh_gw_family;
}

#ifdef CONFIG_IPV6_ROUTE_INFO
int rt6_route_rcv(struct net_device *dev, u8 *opt, int len,
		  const struct in6_addr *gwaddr)
{
	struct net *net = dev_net(dev);
	struct route_info *rinfo = (struct route_info *) opt;
	struct in6_addr prefix_buf, *prefix;
	unsigned int pref;
	unsigned long lifetime;
	struct fib6_info *rt;

	if (len < sizeof(struct route_info)) {
		return -EINVAL;
	}

	/* Sanity check for prefix_len and length */
	if (rinfo->length > 3) {
		return -EINVAL;
	} else if (rinfo->prefix_len > 128) {
		return -EINVAL;
	} else if (rinfo->prefix_len > 64) {
		if (rinfo->length < 2) {
			return -EINVAL;
		}
	} else if (rinfo->prefix_len > 0) {
		if (rinfo->length < 1) {
			return -EINVAL;
		}
	}

	pref = rinfo->route_pref;
	if (pref == ICMPV6_ROUTER_PREF_INVALID)
		return -EINVAL;

	lifetime = addrconf_timeout_fixup(ntohl(rinfo->lifetime), HZ);

	if (rinfo->length == 3)
		prefix = (struct in6_addr *)rinfo->prefix;
	else {
		/* this function is safe */
		ipv6_addr_prefix(&prefix_buf,
				 (struct in6_addr *)rinfo->prefix,
				 rinfo->prefix_len);
		prefix = &prefix_buf;
	}

	if (rinfo->prefix_len == 0)
		rt = rt6_get_dflt_router(net, gwaddr, dev);
	else
		rt = rt6_get_route_info(net, prefix, rinfo->prefix_len,
					gwaddr, dev);

	if (rt && !lifetime) {
		ip6_del_rt(net, rt);
		rt = NULL;
	}

	if (!rt && lifetime)
		rt = rt6_add_route_info(net, prefix, rinfo->prefix_len, gwaddr,
					dev, pref);
	else if (rt)
		rt->fib6_flags = RTF_ROUTEINFO |
				 (rt->fib6_flags & ~RTF_PREF_MASK) | RTF_PREF(pref);

	if (rt) {
		if (!addrconf_finite_timeout(lifetime))
			fib6_clean_expires(rt);
		else
			fib6_set_expires(rt, jiffies + HZ * lifetime);

		fib6_info_release(rt);
	}
	return 0;
}
#endif

/*
 *	Misc support functions
 */

/* called with rcu_lock held */
static struct net_device *ip6_rt_get_dev_rcu(const struct fib6_result *res)
{
	struct net_device *dev = res->nh->fib_nh_dev;

	if (res->fib6_flags & (RTF_LOCAL | RTF_ANYCAST)) {
		/* for copies of local routes, dst->dev needs to be the
		 * device if it is a master device, the master device if
		 * device is enslaved, and the loopback as the default
		 */
		if (netif_is_l3_slave(dev) &&
		    !rt6_need_strict(&res->f6i->fib6_dst.addr))
			dev = l3mdev_master_dev_rcu(dev);
		else if (!netif_is_l3_master(dev))
			dev = dev_net(dev)->loopback_dev;
		/* last case is netif_is_l3_master(dev) is true in which
		 * case we want dev returned to be dev
		 */
	}

	return dev;
}

static const int fib6_prop[RTN_MAX + 1] = {
	[RTN_UNSPEC]	= 0,
	[RTN_UNICAST]	= 0,
	[RTN_LOCAL]	= 0,
	[RTN_BROADCAST]	= 0,
	[RTN_ANYCAST]	= 0,
	[RTN_MULTICAST]	= 0,
	[RTN_BLACKHOLE]	= -EINVAL,
	[RTN_UNREACHABLE] = -EHOSTUNREACH,
	[RTN_PROHIBIT]	= -EACCES,
	[RTN_THROW]	= -EAGAIN,
	[RTN_NAT]	= -EINVAL,
	[RTN_XRESOLVE]	= -EINVAL,
};

static int ip6_rt_type_to_error(u8 fib6_type)
{
	return fib6_prop[fib6_type];
}

static unsigned short fib6_info_dst_flags(struct fib6_info *rt)
{
	unsigned short flags = 0;

	if (rt->dst_nocount)
		flags |= DST_NOCOUNT;
	if (rt->dst_nopolicy)
		flags |= DST_NOPOLICY;
	if (rt->dst_host)
		flags |= DST_HOST;

	return flags;
}

static void ip6_rt_init_dst_reject(struct rt6_info *rt, u8 fib6_type)
{
	rt->dst.error = ip6_rt_type_to_error(fib6_type);

	switch (fib6_type) {
	case RTN_BLACKHOLE:
		rt->dst.output = dst_discard_out;
		rt->dst.input = dst_discard;
		break;
	case RTN_PROHIBIT:
		rt->dst.output = ip6_pkt_prohibit_out;
		rt->dst.input = ip6_pkt_prohibit;
		break;
	case RTN_THROW:
	case RTN_UNREACHABLE:
	default:
		rt->dst.output = ip6_pkt_discard_out;
		rt->dst.input = ip6_pkt_discard;
		break;
	}
}

static void ip6_rt_init_dst(struct rt6_info *rt, const struct fib6_result *res)
{
	struct fib6_info *f6i = res->f6i;

	if (res->fib6_flags & RTF_REJECT) {
		ip6_rt_init_dst_reject(rt, res->fib6_type);
		return;
	}

	rt->dst.error = 0;
	rt->dst.output = ip6_output;

	if (res->fib6_type == RTN_LOCAL || res->fib6_type == RTN_ANYCAST) {
		rt->dst.input = ip6_input;
	} else if (ipv6_addr_type(&f6i->fib6_dst.addr) & IPV6_ADDR_MULTICAST) {
		rt->dst.input = ip6_mc_input;
	} else {
		rt->dst.input = ip6_forward;
	}

	if (res->nh->fib_nh_lws) {
		rt->dst.lwtstate = lwtstate_get(res->nh->fib_nh_lws);
		lwtunnel_set_redirect(&rt->dst);
	}

	rt->dst.lastuse = jiffies;
}

/* Caller must already hold reference to @from */
static void rt6_set_from(struct rt6_info *rt, struct fib6_info *from)
{
	rt->rt6i_flags &= ~RTF_EXPIRES;
	rcu_assign_pointer(rt->from, from);
	ip_dst_init_metrics(&rt->dst, from->fib6_metrics);
}

/* Caller must already hold reference to f6i in result */
static void ip6_rt_copy_init(struct rt6_info *rt, const struct fib6_result *res)
{
	const struct fib6_nh *nh = res->nh;
	const struct net_device *dev = nh->fib_nh_dev;
	struct fib6_info *f6i = res->f6i;

	ip6_rt_init_dst(rt, res);

	rt->rt6i_dst = f6i->fib6_dst;
	rt->rt6i_idev = dev ? in6_dev_get(dev) : NULL;
	rt->rt6i_flags = res->fib6_flags;
	if (nh->fib_nh_gw_family) {
		rt->rt6i_gateway = nh->fib_nh_gw6;
		rt->rt6i_flags |= RTF_GATEWAY;
	}
	rt6_set_from(rt, f6i);
#ifdef CONFIG_IPV6_SUBTREES
	rt->rt6i_src = f6i->fib6_src;
#endif
}

static struct fib6_node* fib6_backtrack(struct fib6_node *fn,
					struct in6_addr *saddr)
{
	struct fib6_node *pn, *sn;
	while (1) {
		if (fn->fn_flags & RTN_TL_ROOT)
			return NULL;
		pn = rcu_dereference(fn->parent);
		sn = FIB6_SUBTREE(pn);
		if (sn && sn != fn)
			fn = fib6_node_lookup(sn, NULL, saddr);
		else
			fn = pn;
		if (fn->fn_flags & RTN_RTINFO)
			return fn;
	}
}

static bool ip6_hold_safe(struct net *net, struct rt6_info **prt)
{
	struct rt6_info *rt = *prt;

	if (dst_hold_safe(&rt->dst))
		return true;
	if (net) {
		rt = net->ipv6.ip6_null_entry;
		dst_hold(&rt->dst);
	} else {
		rt = NULL;
	}
	*prt = rt;
	return false;
}

/* called with rcu_lock held */
static struct rt6_info *ip6_create_rt_rcu(const struct fib6_result *res)
{
	struct net_device *dev = res->nh->fib_nh_dev;
	struct fib6_info *f6i = res->f6i;
	unsigned short flags;
	struct rt6_info *nrt;

	if (!fib6_info_hold_safe(f6i))
		goto fallback;

	flags = fib6_info_dst_flags(f6i);
	nrt = ip6_dst_alloc(dev_net(dev), dev, flags);
	if (!nrt) {
		fib6_info_release(f6i);
		goto fallback;
	}

	ip6_rt_copy_init(nrt, res);
	return nrt;

fallback:
	nrt = dev_net(dev)->ipv6.ip6_null_entry;
	dst_hold(&nrt->dst);
	return nrt;
}

static struct rt6_info *ip6_pol_route_lookup(struct net *net,
					     struct fib6_table *table,
					     struct flowi6 *fl6,
					     const struct sk_buff *skb,
					     int flags)
{
	struct fib6_result res = {};
	struct fib6_node *fn;
	struct rt6_info *rt;

	if (fl6->flowi6_flags & FLOWI_FLAG_SKIP_NH_OIF)
		flags &= ~RT6_LOOKUP_F_IFACE;

	rcu_read_lock();
	fn = fib6_node_lookup(&table->tb6_root, &fl6->daddr, &fl6->saddr);
restart:
	res.f6i = rcu_dereference(fn->leaf);
	if (!res.f6i)
		res.f6i = net->ipv6.fib6_null_entry;
	else
		rt6_device_match(net, &res, &fl6->saddr, fl6->flowi6_oif,
				 flags);

	if (res.f6i == net->ipv6.fib6_null_entry) {
		fn = fib6_backtrack(fn, &fl6->saddr);
		if (fn)
			goto restart;

		rt = net->ipv6.ip6_null_entry;
		dst_hold(&rt->dst);
		goto out;
	}

	fib6_select_path(net, &res, fl6, fl6->flowi6_oif,
			 fl6->flowi6_oif != 0, skb, flags);

	/* Search through exception table */
	rt = rt6_find_cached_rt(&res, &fl6->daddr, &fl6->saddr);
	if (rt) {
		if (ip6_hold_safe(net, &rt))
			dst_use_noref(&rt->dst, jiffies);
	} else {
		rt = ip6_create_rt_rcu(&res);
	}

out:
	trace_fib6_table_lookup(net, &res, table, fl6);

	rcu_read_unlock();

	return rt;
}

struct dst_entry *ip6_route_lookup(struct net *net, struct flowi6 *fl6,
				   const struct sk_buff *skb, int flags)
{
	return fib6_rule_lookup(net, fl6, skb, flags, ip6_pol_route_lookup);
}
EXPORT_SYMBOL_GPL(ip6_route_lookup);

struct rt6_info *rt6_lookup(struct net *net, const struct in6_addr *daddr,
			    const struct in6_addr *saddr, int oif,
			    const struct sk_buff *skb, int strict)
{
	struct flowi6 fl6 = {
		.flowi6_oif = oif,
		.daddr = *daddr,
	};
	struct dst_entry *dst;
	int flags = strict ? RT6_LOOKUP_F_IFACE : 0;

	if (saddr) {
		memcpy(&fl6.saddr, saddr, sizeof(*saddr));
		flags |= RT6_LOOKUP_F_HAS_SADDR;
	}

	dst = fib6_rule_lookup(net, &fl6, skb, flags, ip6_pol_route_lookup);
	if (dst->error == 0)
		return (struct rt6_info *) dst;

	dst_release(dst);

	return NULL;
}
EXPORT_SYMBOL(rt6_lookup);

/* ip6_ins_rt is called with FREE table->tb6_lock.
 * It takes new route entry, the addition fails by any reason the
 * route is released.
 * Caller must hold dst before calling it.
 */

static int __ip6_ins_rt(struct fib6_info *rt, struct nl_info *info,
			struct netlink_ext_ack *extack)
{
	int err;
	struct fib6_table *table;

	table = rt->fib6_table;
	spin_lock_bh(&table->tb6_lock);
	err = fib6_add(&table->tb6_root, rt, info, extack);
	spin_unlock_bh(&table->tb6_lock);

	return err;
}

int ip6_ins_rt(struct net *net, struct fib6_info *rt)
{
	struct nl_info info = {	.nl_net = net, };

	return __ip6_ins_rt(rt, &info, NULL);
}

static struct rt6_info *ip6_rt_cache_alloc(const struct fib6_result *res,
					   const struct in6_addr *daddr,
					   const struct in6_addr *saddr)
{
	struct fib6_info *f6i = res->f6i;
	struct net_device *dev;
	struct rt6_info *rt;

	/*
	 *	Clone the route.
	 */

	if (!fib6_info_hold_safe(f6i))
		return NULL;

	dev = ip6_rt_get_dev_rcu(res);
	rt = ip6_dst_alloc(dev_net(dev), dev, 0);
	if (!rt) {
		fib6_info_release(f6i);
		return NULL;
	}

	ip6_rt_copy_init(rt, res);
	rt->rt6i_flags |= RTF_CACHE;
	rt->dst.flags |= DST_HOST;
	rt->rt6i_dst.addr = *daddr;
	rt->rt6i_dst.plen = 128;

	if (!rt6_is_gw_or_nonexthop(res)) {
		if (f6i->fib6_dst.plen != 128 &&
		    ipv6_addr_equal(&f6i->fib6_dst.addr, daddr))
			rt->rt6i_flags |= RTF_ANYCAST;
#ifdef CONFIG_IPV6_SUBTREES
		if (rt->rt6i_src.plen && saddr) {
			rt->rt6i_src.addr = *saddr;
			rt->rt6i_src.plen = 128;
		}
#endif
	}

	return rt;
}

static struct rt6_info *ip6_rt_pcpu_alloc(const struct fib6_result *res)
{
	struct fib6_info *f6i = res->f6i;
	unsigned short flags = fib6_info_dst_flags(f6i);
	struct net_device *dev;
	struct rt6_info *pcpu_rt;

	if (!fib6_info_hold_safe(f6i))
		return NULL;

	rcu_read_lock();
	dev = ip6_rt_get_dev_rcu(res);
	pcpu_rt = ip6_dst_alloc(dev_net(dev), dev, flags);
	rcu_read_unlock();
	if (!pcpu_rt) {
		fib6_info_release(f6i);
		return NULL;
	}
	ip6_rt_copy_init(pcpu_rt, res);
	pcpu_rt->rt6i_flags |= RTF_PCPU;
	return pcpu_rt;
}

/* It should be called with rcu_read_lock() acquired */
static struct rt6_info *rt6_get_pcpu_route(const struct fib6_result *res)
{
	struct rt6_info *pcpu_rt, **p;

	p = this_cpu_ptr(res->f6i->rt6i_pcpu);
	pcpu_rt = *p;

	if (pcpu_rt)
		ip6_hold_safe(NULL, &pcpu_rt);

	return pcpu_rt;
}

static struct rt6_info *rt6_make_pcpu_route(struct net *net,
					    const struct fib6_result *res)
{
	struct rt6_info *pcpu_rt, *prev, **p;

	pcpu_rt = ip6_rt_pcpu_alloc(res);
	if (!pcpu_rt) {
		dst_hold(&net->ipv6.ip6_null_entry->dst);
		return net->ipv6.ip6_null_entry;
	}

	dst_hold(&pcpu_rt->dst);
	p = this_cpu_ptr(res->f6i->rt6i_pcpu);
	prev = cmpxchg(p, NULL, pcpu_rt);
	BUG_ON(prev);

	return pcpu_rt;
}

/* exception hash table implementation
 */
static DEFINE_SPINLOCK(rt6_exception_lock);

/* Remove rt6_ex from hash table and free the memory
 * Caller must hold rt6_exception_lock
 */
static void rt6_remove_exception(struct rt6_exception_bucket *bucket,
				 struct rt6_exception *rt6_ex)
{
	struct fib6_info *from;
	struct net *net;

	if (!bucket || !rt6_ex)
		return;

	net = dev_net(rt6_ex->rt6i->dst.dev);
	net->ipv6.rt6_stats->fib_rt_cache--;

	/* purge completely the exception to allow releasing the held resources:
	 * some [sk] cache may keep the dst around for unlimited time
	 */
	from = xchg((__force struct fib6_info **)&rt6_ex->rt6i->from, NULL);
	fib6_info_release(from);
	dst_dev_put(&rt6_ex->rt6i->dst);

	hlist_del_rcu(&rt6_ex->hlist);
	dst_release(&rt6_ex->rt6i->dst);
	kfree_rcu(rt6_ex, rcu);
	WARN_ON_ONCE(!bucket->depth);
	bucket->depth--;
}

/* Remove oldest rt6_ex in bucket and free the memory
 * Caller must hold rt6_exception_lock
 */
static void rt6_exception_remove_oldest(struct rt6_exception_bucket *bucket)
{
	struct rt6_exception *rt6_ex, *oldest = NULL;

	if (!bucket)
		return;

	hlist_for_each_entry(rt6_ex, &bucket->chain, hlist) {
		if (!oldest || time_before(rt6_ex->stamp, oldest->stamp))
			oldest = rt6_ex;
	}
	rt6_remove_exception(bucket, oldest);
}

static u32 rt6_exception_hash(const struct in6_addr *dst,
			      const struct in6_addr *src)
{
	static u32 seed __read_mostly;
	u32 val;

	net_get_random_once(&seed, sizeof(seed));
	val = jhash(dst, sizeof(*dst), seed);

#ifdef CONFIG_IPV6_SUBTREES
	if (src)
		val = jhash(src, sizeof(*src), val);
#endif
	return hash_32(val, FIB6_EXCEPTION_BUCKET_SIZE_SHIFT);
}

/* Helper function to find the cached rt in the hash table
 * and update bucket pointer to point to the bucket for this
 * (daddr, saddr) pair
 * Caller must hold rt6_exception_lock
 */
static struct rt6_exception *
__rt6_find_exception_spinlock(struct rt6_exception_bucket **bucket,
			      const struct in6_addr *daddr,
			      const struct in6_addr *saddr)
{
	struct rt6_exception *rt6_ex;
	u32 hval;

	if (!(*bucket) || !daddr)
		return NULL;

	hval = rt6_exception_hash(daddr, saddr);
	*bucket += hval;

	hlist_for_each_entry(rt6_ex, &(*bucket)->chain, hlist) {
		struct rt6_info *rt6 = rt6_ex->rt6i;
		bool matched = ipv6_addr_equal(daddr, &rt6->rt6i_dst.addr);

#ifdef CONFIG_IPV6_SUBTREES
		if (matched && saddr)
			matched = ipv6_addr_equal(saddr, &rt6->rt6i_src.addr);
#endif
		if (matched)
			return rt6_ex;
	}
	return NULL;
}

/* Helper function to find the cached rt in the hash table
 * and update bucket pointer to point to the bucket for this
 * (daddr, saddr) pair
 * Caller must hold rcu_read_lock()
 */
static struct rt6_exception *
__rt6_find_exception_rcu(struct rt6_exception_bucket **bucket,
			 const struct in6_addr *daddr,
			 const struct in6_addr *saddr)
{
	struct rt6_exception *rt6_ex;
	u32 hval;

	WARN_ON_ONCE(!rcu_read_lock_held());

	if (!(*bucket) || !daddr)
		return NULL;

	hval = rt6_exception_hash(daddr, saddr);
	*bucket += hval;

	hlist_for_each_entry_rcu(rt6_ex, &(*bucket)->chain, hlist) {
		struct rt6_info *rt6 = rt6_ex->rt6i;
		bool matched = ipv6_addr_equal(daddr, &rt6->rt6i_dst.addr);

#ifdef CONFIG_IPV6_SUBTREES
		if (matched && saddr)
			matched = ipv6_addr_equal(saddr, &rt6->rt6i_src.addr);
#endif
		if (matched)
			return rt6_ex;
	}
	return NULL;
}

static unsigned int fib6_mtu(const struct fib6_result *res)
{
	const struct fib6_nh *nh = res->nh;
	unsigned int mtu;

	if (res->f6i->fib6_pmtu) {
		mtu = res->f6i->fib6_pmtu;
	} else {
		struct net_device *dev = nh->fib_nh_dev;
		struct inet6_dev *idev;

		rcu_read_lock();
		idev = __in6_dev_get(dev);
		mtu = idev->cnf.mtu6;
		rcu_read_unlock();
	}

	mtu = min_t(unsigned int, mtu, IP6_MAX_MTU);

	return mtu - lwtunnel_headroom(nh->fib_nh_lws, mtu);
}

static int rt6_insert_exception(struct rt6_info *nrt,
				const struct fib6_result *res)
{
	struct net *net = dev_net(nrt->dst.dev);
	struct rt6_exception_bucket *bucket;
	struct in6_addr *src_key = NULL;
	struct rt6_exception *rt6_ex;
	struct fib6_info *f6i = res->f6i;
	int err = 0;

	spin_lock_bh(&rt6_exception_lock);

	if (f6i->exception_bucket_flushed) {
		err = -EINVAL;
		goto out;
	}

	bucket = rcu_dereference_protected(f6i->rt6i_exception_bucket,
					lockdep_is_held(&rt6_exception_lock));
	if (!bucket) {
		bucket = kcalloc(FIB6_EXCEPTION_BUCKET_SIZE, sizeof(*bucket),
				 GFP_ATOMIC);
		if (!bucket) {
			err = -ENOMEM;
			goto out;
		}
		rcu_assign_pointer(f6i->rt6i_exception_bucket, bucket);
	}

#ifdef CONFIG_IPV6_SUBTREES
	/* fib6_src.plen != 0 indicates f6i is in subtree
	 * and exception table is indexed by a hash of
	 * both fib6_dst and fib6_src.
	 * Otherwise, the exception table is indexed by
	 * a hash of only fib6_dst.
	 */
	if (f6i->fib6_src.plen)
		src_key = &nrt->rt6i_src.addr;
#endif
	/* rt6_mtu_change() might lower mtu on f6i.
	 * Only insert this exception route if its mtu
	 * is less than f6i's mtu value.
	 */
	if (dst_metric_raw(&nrt->dst, RTAX_MTU) >= fib6_mtu(res)) {
		err = -EINVAL;
		goto out;
	}

	rt6_ex = __rt6_find_exception_spinlock(&bucket, &nrt->rt6i_dst.addr,
					       src_key);
	if (rt6_ex)
		rt6_remove_exception(bucket, rt6_ex);

	rt6_ex = kzalloc(sizeof(*rt6_ex), GFP_ATOMIC);
	if (!rt6_ex) {
		err = -ENOMEM;
		goto out;
	}
	rt6_ex->rt6i = nrt;
	rt6_ex->stamp = jiffies;
	hlist_add_head_rcu(&rt6_ex->hlist, &bucket->chain);
	bucket->depth++;
	net->ipv6.rt6_stats->fib_rt_cache++;

	if (bucket->depth > FIB6_MAX_DEPTH)
		rt6_exception_remove_oldest(bucket);

out:
	spin_unlock_bh(&rt6_exception_lock);

	/* Update fn->fn_sernum to invalidate all cached dst */
	if (!err) {
		spin_lock_bh(&f6i->fib6_table->tb6_lock);
		fib6_update_sernum(net, f6i);
		spin_unlock_bh(&f6i->fib6_table->tb6_lock);
		fib6_force_start_gc(net);
	}

	return err;
}

void rt6_flush_exceptions(struct fib6_info *rt)
{
	struct rt6_exception_bucket *bucket;
	struct rt6_exception *rt6_ex;
	struct hlist_node *tmp;
	int i;

	spin_lock_bh(&rt6_exception_lock);
	/* Prevent rt6_insert_exception() to recreate the bucket list */
	rt->exception_bucket_flushed = 1;

	bucket = rcu_dereference_protected(rt->rt6i_exception_bucket,
				    lockdep_is_held(&rt6_exception_lock));
	if (!bucket)
		goto out;

	for (i = 0; i < FIB6_EXCEPTION_BUCKET_SIZE; i++) {
		hlist_for_each_entry_safe(rt6_ex, tmp, &bucket->chain, hlist)
			rt6_remove_exception(bucket, rt6_ex);
		WARN_ON_ONCE(bucket->depth);
		bucket++;
	}

out:
	spin_unlock_bh(&rt6_exception_lock);
}

/* Find cached rt in the hash table inside passed in rt
 * Caller has to hold rcu_read_lock()
 */
static struct rt6_info *rt6_find_cached_rt(const struct fib6_result *res,
					   struct in6_addr *daddr,
					   struct in6_addr *saddr)
{
	struct rt6_exception_bucket *bucket;
	struct in6_addr *src_key = NULL;
	struct rt6_exception *rt6_ex;
	struct rt6_info *ret = NULL;

	bucket = rcu_dereference(res->f6i->rt6i_exception_bucket);

#ifdef CONFIG_IPV6_SUBTREES
	/* fib6i_src.plen != 0 indicates f6i is in subtree
	 * and exception table is indexed by a hash of
	 * both fib6_dst and fib6_src.
	 * Otherwise, the exception table is indexed by
	 * a hash of only fib6_dst.
	 */
	if (res->f6i->fib6_src.plen)
		src_key = saddr;
#endif
	rt6_ex = __rt6_find_exception_rcu(&bucket, daddr, src_key);

	if (rt6_ex && !rt6_check_expired(rt6_ex->rt6i))
		ret = rt6_ex->rt6i;

	return ret;
}

/* Remove the passed in cached rt from the hash table that contains it */
static int rt6_remove_exception_rt(struct rt6_info *rt)
{
	struct rt6_exception_bucket *bucket;
	struct in6_addr *src_key = NULL;
	struct rt6_exception *rt6_ex;
	struct fib6_info *from;
	int err;

	from = rcu_dereference(rt->from);
	if (!from ||
	    !(rt->rt6i_flags & RTF_CACHE))
		return -EINVAL;

	if (!rcu_access_pointer(from->rt6i_exception_bucket))
		return -ENOENT;

	spin_lock_bh(&rt6_exception_lock);
	bucket = rcu_dereference_protected(from->rt6i_exception_bucket,
				    lockdep_is_held(&rt6_exception_lock));
#ifdef CONFIG_IPV6_SUBTREES
	/* rt6i_src.plen != 0 indicates 'from' is in subtree
	 * and exception table is indexed by a hash of
	 * both rt6i_dst and rt6i_src.
	 * Otherwise, the exception table is indexed by
	 * a hash of only rt6i_dst.
	 */
	if (from->fib6_src.plen)
		src_key = &rt->rt6i_src.addr;
#endif
	rt6_ex = __rt6_find_exception_spinlock(&bucket,
					       &rt->rt6i_dst.addr,
					       src_key);
	if (rt6_ex) {
		rt6_remove_exception(bucket, rt6_ex);
		err = 0;
	} else {
		err = -ENOENT;
	}

	spin_unlock_bh(&rt6_exception_lock);
	return err;
}

/* Find rt6_ex which contains the passed in rt cache and
 * refresh its stamp
 */
static void rt6_update_exception_stamp_rt(struct rt6_info *rt)
{
	struct rt6_exception_bucket *bucket;
	struct in6_addr *src_key = NULL;
	struct rt6_exception *rt6_ex;
	struct fib6_info *from;

	rcu_read_lock();
	from = rcu_dereference(rt->from);
	if (!from || !(rt->rt6i_flags & RTF_CACHE))
		goto unlock;

	bucket = rcu_dereference(from->rt6i_exception_bucket);

#ifdef CONFIG_IPV6_SUBTREES
	/* rt6i_src.plen != 0 indicates 'from' is in subtree
	 * and exception table is indexed by a hash of
	 * both rt6i_dst and rt6i_src.
	 * Otherwise, the exception table is indexed by
	 * a hash of only rt6i_dst.
	 */
	if (from->fib6_src.plen)
		src_key = &rt->rt6i_src.addr;
#endif
	rt6_ex = __rt6_find_exception_rcu(&bucket,
					  &rt->rt6i_dst.addr,
					  src_key);
	if (rt6_ex)
		rt6_ex->stamp = jiffies;

unlock:
	rcu_read_unlock();
}

static bool rt6_mtu_change_route_allowed(struct inet6_dev *idev,
					 struct rt6_info *rt, int mtu)
{
	/* If the new MTU is lower than the route PMTU, this new MTU will be the
	 * lowest MTU in the path: always allow updating the route PMTU to
	 * reflect PMTU decreases.
	 *
	 * If the new MTU is higher, and the route PMTU is equal to the local
	 * MTU, this means the old MTU is the lowest in the path, so allow
	 * updating it: if other nodes now have lower MTUs, PMTU discovery will
	 * handle this.
	 */

	if (dst_mtu(&rt->dst) >= mtu)
		return true;

	if (dst_mtu(&rt->dst) == idev->cnf.mtu6)
		return true;

	return false;
}

static void rt6_exceptions_update_pmtu(struct inet6_dev *idev,
				       struct fib6_info *rt, int mtu)
{
	struct rt6_exception_bucket *bucket;
	struct rt6_exception *rt6_ex;
	int i;

	bucket = rcu_dereference_protected(rt->rt6i_exception_bucket,
					lockdep_is_held(&rt6_exception_lock));

	if (!bucket)
		return;

	for (i = 0; i < FIB6_EXCEPTION_BUCKET_SIZE; i++) {
		hlist_for_each_entry(rt6_ex, &bucket->chain, hlist) {
			struct rt6_info *entry = rt6_ex->rt6i;

			/* For RTF_CACHE with rt6i_pmtu == 0 (i.e. a redirected
			 * route), the metrics of its rt->from have already
			 * been updated.
			 */
			if (dst_metric_raw(&entry->dst, RTAX_MTU) &&
			    rt6_mtu_change_route_allowed(idev, entry, mtu))
				dst_metric_set(&entry->dst, RTAX_MTU, mtu);
		}
		bucket++;
	}
}

#define RTF_CACHE_GATEWAY	(RTF_GATEWAY | RTF_CACHE)

static void rt6_exceptions_clean_tohost(struct fib6_info *rt,
					struct in6_addr *gateway)
{
	struct rt6_exception_bucket *bucket;
	struct rt6_exception *rt6_ex;
	struct hlist_node *tmp;
	int i;

	if (!rcu_access_pointer(rt->rt6i_exception_bucket))
		return;

	spin_lock_bh(&rt6_exception_lock);
	bucket = rcu_dereference_protected(rt->rt6i_exception_bucket,
				     lockdep_is_held(&rt6_exception_lock));

	if (bucket) {
		for (i = 0; i < FIB6_EXCEPTION_BUCKET_SIZE; i++) {
			hlist_for_each_entry_safe(rt6_ex, tmp,
						  &bucket->chain, hlist) {
				struct rt6_info *entry = rt6_ex->rt6i;

				if ((entry->rt6i_flags & RTF_CACHE_GATEWAY) ==
				    RTF_CACHE_GATEWAY &&
				    ipv6_addr_equal(gateway,
						    &entry->rt6i_gateway)) {
					rt6_remove_exception(bucket, rt6_ex);
				}
			}
			bucket++;
		}
	}

	spin_unlock_bh(&rt6_exception_lock);
}

static void rt6_age_examine_exception(struct rt6_exception_bucket *bucket,
				      struct rt6_exception *rt6_ex,
				      struct fib6_gc_args *gc_args,
				      unsigned long now)
{
	struct rt6_info *rt = rt6_ex->rt6i;

	/* we are pruning and obsoleting aged-out and non gateway exceptions
	 * even if others have still references to them, so that on next
	 * dst_check() such references can be dropped.
	 * EXPIRES exceptions - e.g. pmtu-generated ones are pruned when
	 * expired, independently from their aging, as per RFC 8201 section 4
	 */
	if (!(rt->rt6i_flags & RTF_EXPIRES)) {
		if (time_after_eq(now, rt->dst.lastuse + gc_args->timeout)) {
			RT6_TRACE("aging clone %p\n", rt);
			rt6_remove_exception(bucket, rt6_ex);
			return;
		}
	} else if (time_after(jiffies, rt->dst.expires)) {
		RT6_TRACE("purging expired route %p\n", rt);
		rt6_remove_exception(bucket, rt6_ex);
		return;
	}

	if (rt->rt6i_flags & RTF_GATEWAY) {
		struct neighbour *neigh;
		__u8 neigh_flags = 0;

		neigh = __ipv6_neigh_lookup_noref(rt->dst.dev, &rt->rt6i_gateway);
		if (neigh)
			neigh_flags = neigh->flags;

		if (!(neigh_flags & NTF_ROUTER)) {
			RT6_TRACE("purging route %p via non-router but gateway\n",
				  rt);
			rt6_remove_exception(bucket, rt6_ex);
			return;
		}
	}

	gc_args->more++;
}

void rt6_age_exceptions(struct fib6_info *rt,
			struct fib6_gc_args *gc_args,
			unsigned long now)
{
	struct rt6_exception_bucket *bucket;
	struct rt6_exception *rt6_ex;
	struct hlist_node *tmp;
	int i;

	if (!rcu_access_pointer(rt->rt6i_exception_bucket))
		return;

	rcu_read_lock_bh();
	spin_lock(&rt6_exception_lock);
	bucket = rcu_dereference_protected(rt->rt6i_exception_bucket,
				    lockdep_is_held(&rt6_exception_lock));

	if (bucket) {
		for (i = 0; i < FIB6_EXCEPTION_BUCKET_SIZE; i++) {
			hlist_for_each_entry_safe(rt6_ex, tmp,
						  &bucket->chain, hlist) {
				rt6_age_examine_exception(bucket, rt6_ex,
							  gc_args, now);
			}
			bucket++;
		}
	}
	spin_unlock(&rt6_exception_lock);
	rcu_read_unlock_bh();
}

/* must be called with rcu lock held */
int fib6_table_lookup(struct net *net, struct fib6_table *table, int oif,
		      struct flowi6 *fl6, struct fib6_result *res, int strict)
{
	struct fib6_node *fn, *saved_fn;

	fn = fib6_node_lookup(&table->tb6_root, &fl6->daddr, &fl6->saddr);
	saved_fn = fn;

	if (fl6->flowi6_flags & FLOWI_FLAG_SKIP_NH_OIF)
		oif = 0;

redo_rt6_select:
	rt6_select(net, fn, oif, res, strict);
	if (res->f6i == net->ipv6.fib6_null_entry) {
		fn = fib6_backtrack(fn, &fl6->saddr);
		if (fn)
			goto redo_rt6_select;
		else if (strict & RT6_LOOKUP_F_REACHABLE) {
			/* also consider unreachable route */
			strict &= ~RT6_LOOKUP_F_REACHABLE;
			fn = saved_fn;
			goto redo_rt6_select;
		}
	}

	trace_fib6_table_lookup(net, res, table, fl6);

	return 0;
}

struct rt6_info *ip6_pol_route(struct net *net, struct fib6_table *table,
			       int oif, struct flowi6 *fl6,
			       const struct sk_buff *skb, int flags)
{
	struct fib6_result res = {};
	struct rt6_info *rt;
	int strict = 0;

	strict |= flags & RT6_LOOKUP_F_IFACE;
	strict |= flags & RT6_LOOKUP_F_IGNORE_LINKSTATE;
	if (net->ipv6.devconf_all->forwarding == 0)
		strict |= RT6_LOOKUP_F_REACHABLE;

	rcu_read_lock();

	fib6_table_lookup(net, table, oif, fl6, &res, strict);
	if (res.f6i == net->ipv6.fib6_null_entry) {
		rt = net->ipv6.ip6_null_entry;
		rcu_read_unlock();
		dst_hold(&rt->dst);
		return rt;
	}

	fib6_select_path(net, &res, fl6, oif, false, skb, strict);

	/*Search through exception table */
	rt = rt6_find_cached_rt(&res, &fl6->daddr, &fl6->saddr);
	if (rt) {
		if (ip6_hold_safe(net, &rt))
			dst_use_noref(&rt->dst, jiffies);

		rcu_read_unlock();
		return rt;
	} else if (unlikely((fl6->flowi6_flags & FLOWI_FLAG_KNOWN_NH) &&
			    !res.nh->fib_nh_gw_family)) {
		/* Create a RTF_CACHE clone which will not be
		 * owned by the fib6 tree.  It is for the special case where
		 * the daddr in the skb during the neighbor look-up is different
		 * from the fl6->daddr used to look-up route here.
		 */
		struct rt6_info *uncached_rt;

		uncached_rt = ip6_rt_cache_alloc(&res, &fl6->daddr, NULL);

		rcu_read_unlock();

		if (uncached_rt) {
			/* Uncached_rt's refcnt is taken during ip6_rt_cache_alloc()
			 * No need for another dst_hold()
			 */
			rt6_uncached_list_add(uncached_rt);
			atomic_inc(&net->ipv6.rt6_stats->fib_rt_uncache);
		} else {
			uncached_rt = net->ipv6.ip6_null_entry;
			dst_hold(&uncached_rt->dst);
		}

		return uncached_rt;
	} else {
		/* Get a percpu copy */

		struct rt6_info *pcpu_rt;

		local_bh_disable();
		pcpu_rt = rt6_get_pcpu_route(&res);

		if (!pcpu_rt)
			pcpu_rt = rt6_make_pcpu_route(net, &res);

		local_bh_enable();
		rcu_read_unlock();

		return pcpu_rt;
	}
}
EXPORT_SYMBOL_GPL(ip6_pol_route);

static struct rt6_info *ip6_pol_route_input(struct net *net,
					    struct fib6_table *table,
					    struct flowi6 *fl6,
					    const struct sk_buff *skb,
					    int flags)
{
	return ip6_pol_route(net, table, fl6->flowi6_iif, fl6, skb, flags);
}

struct dst_entry *ip6_route_input_lookup(struct net *net,
					 struct net_device *dev,
					 struct flowi6 *fl6,
					 const struct sk_buff *skb,
					 int flags)
{
	if (rt6_need_strict(&fl6->daddr) && dev->type != ARPHRD_PIMREG)
		flags |= RT6_LOOKUP_F_IFACE;

	return fib6_rule_lookup(net, fl6, skb, flags, ip6_pol_route_input);
}
EXPORT_SYMBOL_GPL(ip6_route_input_lookup);

static void ip6_multipath_l3_keys(const struct sk_buff *skb,
				  struct flow_keys *keys,
				  struct flow_keys *flkeys)
{
	const struct ipv6hdr *outer_iph = ipv6_hdr(skb);
	const struct ipv6hdr *key_iph = outer_iph;
	struct flow_keys *_flkeys = flkeys;
	const struct ipv6hdr *inner_iph;
	const struct icmp6hdr *icmph;
	struct ipv6hdr _inner_iph;
	struct icmp6hdr _icmph;

	if (likely(outer_iph->nexthdr != IPPROTO_ICMPV6))
		goto out;

	icmph = skb_header_pointer(skb, skb_transport_offset(skb),
				   sizeof(_icmph), &_icmph);
	if (!icmph)
		goto out;

	if (icmph->icmp6_type != ICMPV6_DEST_UNREACH &&
	    icmph->icmp6_type != ICMPV6_PKT_TOOBIG &&
	    icmph->icmp6_type != ICMPV6_TIME_EXCEED &&
	    icmph->icmp6_type != ICMPV6_PARAMPROB)
		goto out;

	inner_iph = skb_header_pointer(skb,
				       skb_transport_offset(skb) + sizeof(*icmph),
				       sizeof(_inner_iph), &_inner_iph);
	if (!inner_iph)
		goto out;

	key_iph = inner_iph;
	_flkeys = NULL;
out:
	if (_flkeys) {
		keys->addrs.v6addrs.src = _flkeys->addrs.v6addrs.src;
		keys->addrs.v6addrs.dst = _flkeys->addrs.v6addrs.dst;
		keys->tags.flow_label = _flkeys->tags.flow_label;
		keys->basic.ip_proto = _flkeys->basic.ip_proto;
	} else {
		keys->addrs.v6addrs.src = key_iph->saddr;
		keys->addrs.v6addrs.dst = key_iph->daddr;
		keys->tags.flow_label = ip6_flowlabel(key_iph);
		keys->basic.ip_proto = key_iph->nexthdr;
	}
}

/* if skb is set it will be used and fl6 can be NULL */
u32 rt6_multipath_hash(const struct net *net, const struct flowi6 *fl6,
		       const struct sk_buff *skb, struct flow_keys *flkeys)
{
	struct flow_keys hash_keys;
	u32 mhash;

	switch (ip6_multipath_hash_policy(net)) {
	case 0:
		memset(&hash_keys, 0, sizeof(hash_keys));
		hash_keys.control.addr_type = FLOW_DISSECTOR_KEY_IPV6_ADDRS;
		if (skb) {
			ip6_multipath_l3_keys(skb, &hash_keys, flkeys);
		} else {
			hash_keys.addrs.v6addrs.src = fl6->saddr;
			hash_keys.addrs.v6addrs.dst = fl6->daddr;
			hash_keys.tags.flow_label = (__force u32)flowi6_get_flowlabel(fl6);
			hash_keys.basic.ip_proto = fl6->flowi6_proto;
		}
		break;
	case 1:
		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_IPV6_ADDRS;
			hash_keys.addrs.v6addrs.src = flkeys->addrs.v6addrs.src;
			hash_keys.addrs.v6addrs.dst = flkeys->addrs.v6addrs.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_IPV6_ADDRS;
			hash_keys.addrs.v6addrs.src = fl6->saddr;
			hash_keys.addrs.v6addrs.dst = fl6->daddr;
			hash_keys.ports.src = fl6->fl6_sport;
			hash_keys.ports.dst = fl6->fl6_dport;
			hash_keys.basic.ip_proto = fl6->flowi6_proto;
		}
		break;
	}
	mhash = flow_hash_from_keys(&hash_keys);

	return mhash >> 1;
}

void ip6_route_input(struct sk_buff *skb)
{
	const struct ipv6hdr *iph = ipv6_hdr(skb);
	struct net *net = dev_net(skb->dev);
	int flags = RT6_LOOKUP_F_HAS_SADDR;
	struct ip_tunnel_info *tun_info;
	struct flowi6 fl6 = {
		.flowi6_iif = skb->dev->ifindex,
		.daddr = iph->daddr,
		.saddr = iph->saddr,
		.flowlabel = ip6_flowinfo(iph),
		.flowi6_mark = skb->mark,
		.flowi6_proto = iph->nexthdr,
	};
	struct flow_keys *flkeys = NULL, _flkeys;

	tun_info = skb_tunnel_info(skb);
	if (tun_info && !(tun_info->mode & IP_TUNNEL_INFO_TX))
		fl6.flowi6_tun_key.tun_id = tun_info->key.tun_id;

	if (fib6_rules_early_flow_dissect(net, skb, &fl6, &_flkeys))
		flkeys = &_flkeys;

	if (unlikely(fl6.flowi6_proto == IPPROTO_ICMPV6))
		fl6.mp_hash = rt6_multipath_hash(net, &fl6, skb, flkeys);
	skb_dst_drop(skb);
	skb_dst_set(skb,
		    ip6_route_input_lookup(net, skb->dev, &fl6, skb, flags));
}

static struct rt6_info *ip6_pol_route_output(struct net *net,
					     struct fib6_table *table,
					     struct flowi6 *fl6,
					     const struct sk_buff *skb,
					     int flags)
{
	return ip6_pol_route(net, table, fl6->flowi6_oif, fl6, skb, flags);
}

struct dst_entry *ip6_route_output_flags(struct net *net, const struct sock *sk,
					 struct flowi6 *fl6, int flags)
{
	bool any_src;

	if (ipv6_addr_type(&fl6->daddr) &
	    (IPV6_ADDR_MULTICAST | IPV6_ADDR_LINKLOCAL)) {
		struct dst_entry *dst;

		dst = l3mdev_link_scope_lookup(net, fl6);
		if (dst)
			return dst;
	}

	fl6->flowi6_iif = LOOPBACK_IFINDEX;

	any_src = ipv6_addr_any(&fl6->saddr);
	if ((sk && sk->sk_bound_dev_if) || rt6_need_strict(&fl6->daddr) ||
	    (fl6->flowi6_oif && any_src))
		flags |= RT6_LOOKUP_F_IFACE;

	if (!any_src)
		flags |= RT6_LOOKUP_F_HAS_SADDR;
	else if (sk)
		flags |= rt6_srcprefs2flags(inet6_sk(sk)->srcprefs);

	return fib6_rule_lookup(net, fl6, NULL, flags, ip6_pol_route_output);
}
EXPORT_SYMBOL_GPL(ip6_route_output_flags);

struct dst_entry *ip6_blackhole_route(struct net *net, struct dst_entry *dst_orig)
{
	struct rt6_info *rt, *ort = (struct rt6_info *) dst_orig;
	struct net_device *loopback_dev = net->loopback_dev;
	struct dst_entry *new = NULL;

	rt = dst_alloc(&ip6_dst_blackhole_ops, loopback_dev, 1,
		       DST_OBSOLETE_DEAD, 0);
	if (rt) {
		rt6_info_init(rt);
		atomic_inc(&net->ipv6.rt6_stats->fib_rt_alloc);

		new = &rt->dst;
		new->__use = 1;
		new->input = dst_discard;
		new->output = dst_discard_out;

		dst_copy_metrics(new, &ort->dst);

		rt->rt6i_idev = in6_dev_get(loopback_dev);
		rt->rt6i_gateway = ort->rt6i_gateway;
		rt->rt6i_flags = ort->rt6i_flags & ~RTF_PCPU;

		memcpy(&rt->rt6i_dst, &ort->rt6i_dst, sizeof(struct rt6key));
#ifdef CONFIG_IPV6_SUBTREES
		memcpy(&rt->rt6i_src, &ort->rt6i_src, sizeof(struct rt6key));
#endif
	}

	dst_release(dst_orig);
	return new ? new : ERR_PTR(-ENOMEM);
}

/*
 *	Destination cache support functions
 */

static bool fib6_check(struct fib6_info *f6i, u32 cookie)
{
	u32 rt_cookie = 0;

	if (!fib6_get_cookie_safe(f6i, &rt_cookie) || rt_cookie != cookie)
		return false;

	if (fib6_check_expired(f6i))
		return false;

	return true;
}

static struct dst_entry *rt6_check(struct rt6_info *rt,
				   struct fib6_info *from,
				   u32 cookie)
{
	u32 rt_cookie = 0;

	if ((from && !fib6_get_cookie_safe(from, &rt_cookie)) ||
	    rt_cookie != cookie)
		return NULL;

	if (rt6_check_expired(rt))
		return NULL;

	return &rt->dst;
}

static struct dst_entry *rt6_dst_from_check(struct rt6_info *rt,
					    struct fib6_info *from,
					    u32 cookie)
{
	if (!__rt6_check_expired(rt) &&
	    rt->dst.obsolete == DST_OBSOLETE_FORCE_CHK &&
	    fib6_check(from, cookie))
		return &rt->dst;
	else
		return NULL;
}

static struct dst_entry *ip6_dst_check(struct dst_entry *dst, u32 cookie)
{
	struct dst_entry *dst_ret;
	struct fib6_info *from;
	struct rt6_info *rt;

	rt = container_of(dst, struct rt6_info, dst);

	rcu_read_lock();

	/* All IPV6 dsts are created with ->obsolete set to the value
	 * DST_OBSOLETE_FORCE_CHK which forces validation calls down
	 * into this function always.
	 */

	from = rcu_dereference(rt->from);

	if (from && (rt->rt6i_flags & RTF_PCPU ||
	    unlikely(!list_empty(&rt->rt6i_uncached))))
		dst_ret = rt6_dst_from_check(rt, from, cookie);
	else
		dst_ret = rt6_check(rt, from, cookie);

	rcu_read_unlock();

	return dst_ret;
}

static struct dst_entry *ip6_negative_advice(struct dst_entry *dst)
{
	struct rt6_info *rt = (struct rt6_info *) dst;

	if (rt) {
		if (rt->rt6i_flags & RTF_CACHE) {
			rcu_read_lock();
			if (rt6_check_expired(rt)) {
				rt6_remove_exception_rt(rt);
				dst = NULL;
			}
			rcu_read_unlock();
		} else {
			dst_release(dst);
			dst = NULL;
		}
	}
	return dst;
}

static void ip6_link_failure(struct sk_buff *skb)
{
	struct rt6_info *rt;

	icmpv6_send(skb, ICMPV6_DEST_UNREACH, ICMPV6_ADDR_UNREACH, 0);

	rt = (struct rt6_info *) skb_dst(skb);
	if (rt) {
		rcu_read_lock();
		if (rt->rt6i_flags & RTF_CACHE) {
			rt6_remove_exception_rt(rt);
		} else {
			struct fib6_info *from;
			struct fib6_node *fn;

			from = rcu_dereference(rt->from);
			if (from) {
				fn = rcu_dereference(from->fib6_node);
				if (fn && (rt->rt6i_flags & RTF_DEFAULT))
					fn->fn_sernum = -1;
			}
		}
		rcu_read_unlock();
	}
}

static void rt6_update_expires(struct rt6_info *rt0, int timeout)
{
	if (!(rt0->rt6i_flags & RTF_EXPIRES)) {
		struct fib6_info *from;

		rcu_read_lock();
		from = rcu_dereference(rt0->from);
		if (from)
			rt0->dst.expires = from->expires;
		rcu_read_unlock();
	}

	dst_set_expires(&rt0->dst, timeout);
	rt0->rt6i_flags |= RTF_EXPIRES;
}

static void rt6_do_update_pmtu(struct rt6_info *rt, u32 mtu)
{
	struct net *net = dev_net(rt->dst.dev);

	dst_metric_set(&rt->dst, RTAX_MTU, mtu);
	rt->rt6i_flags |= RTF_MODIFIED;
	rt6_update_expires(rt, net->ipv6.sysctl.ip6_rt_mtu_expires);
}

static bool rt6_cache_allowed_for_pmtu(const struct rt6_info *rt)
{
	return !(rt->rt6i_flags & RTF_CACHE) &&
		(rt->rt6i_flags & RTF_PCPU || rcu_access_pointer(rt->from));
}

static void __ip6_rt_update_pmtu(struct dst_entry *dst, const struct sock *sk,
				 const struct ipv6hdr *iph, u32 mtu)
{
	const struct in6_addr *daddr, *saddr;
	struct rt6_info *rt6 = (struct rt6_info *)dst;

	if (dst_metric_locked(dst, RTAX_MTU))
		return;

	if (iph) {
		daddr = &iph->daddr;
		saddr = &iph->saddr;
	} else if (sk) {
		daddr = &sk->sk_v6_daddr;
		saddr = &inet6_sk(sk)->saddr;
	} else {
		daddr = NULL;
		saddr = NULL;
	}
	dst_confirm_neigh(dst, daddr);
	mtu = max_t(u32, mtu, IPV6_MIN_MTU);
	if (mtu >= dst_mtu(dst))
		return;

	if (!rt6_cache_allowed_for_pmtu(rt6)) {
		rt6_do_update_pmtu(rt6, mtu);
		/* update rt6_ex->stamp for cache */
		if (rt6->rt6i_flags & RTF_CACHE)
			rt6_update_exception_stamp_rt(rt6);
	} else if (daddr) {
		struct fib6_result res = {};
		struct rt6_info *nrt6;

		rcu_read_lock();
		res.f6i = rcu_dereference(rt6->from);
		if (!res.f6i) {
			rcu_read_unlock();
			return;
		}
		res.nh = &res.f6i->fib6_nh;
		res.fib6_flags = res.f6i->fib6_flags;
		res.fib6_type = res.f6i->fib6_type;

		nrt6 = ip6_rt_cache_alloc(&res, daddr, saddr);
		if (nrt6) {
			rt6_do_update_pmtu(nrt6, mtu);
			if (rt6_insert_exception(nrt6, &res))
				dst_release_immediate(&nrt6->dst);
		}
		rcu_read_unlock();
	}
}

static void ip6_rt_update_pmtu(struct dst_entry *dst, struct sock *sk,
			       struct sk_buff *skb, u32 mtu)
{
	__ip6_rt_update_pmtu(dst, sk, skb ? ipv6_hdr(skb) : NULL, mtu);
}

void ip6_update_pmtu(struct sk_buff *skb, struct net *net, __be32 mtu,
		     int oif, u32 mark, kuid_t uid)
{
	const struct ipv6hdr *iph = (struct ipv6hdr *) skb->data;
	struct dst_entry *dst;
	struct flowi6 fl6 = {
		.flowi6_oif = oif,
		.flowi6_mark = mark ? mark : IP6_REPLY_MARK(net, skb->mark),
		.daddr = iph->daddr,
		.saddr = iph->saddr,
		.flowlabel = ip6_flowinfo(iph),
		.flowi6_uid = uid,
	};

	dst = ip6_route_output(net, NULL, &fl6);
	if (!dst->error)
		__ip6_rt_update_pmtu(dst, NULL, iph, ntohl(mtu));
	dst_release(dst);
}
EXPORT_SYMBOL_GPL(ip6_update_pmtu);

void ip6_sk_update_pmtu(struct sk_buff *skb, struct sock *sk, __be32 mtu)
{
	int oif = sk->sk_bound_dev_if;
	struct dst_entry *dst;

	if (!oif && skb->dev)
		oif = l3mdev_master_ifindex(skb->dev);

	ip6_update_pmtu(skb, sock_net(sk), mtu, oif, sk->sk_mark, sk->sk_uid);

	dst = __sk_dst_get(sk);
	if (!dst || !dst->obsolete ||
	    dst->ops->check(dst, inet6_sk(sk)->dst_cookie))
		return;

	bh_lock_sock(sk);
	if (!sock_owned_by_user(sk) && !ipv6_addr_v4mapped(&sk->sk_v6_daddr))
		ip6_datagram_dst_update(sk, false);
	bh_unlock_sock(sk);
}
EXPORT_SYMBOL_GPL(ip6_sk_update_pmtu);

void ip6_sk_dst_store_flow(struct sock *sk, struct dst_entry *dst,
			   const struct flowi6 *fl6)
{
#ifdef CONFIG_IPV6_SUBTREES
	struct ipv6_pinfo *np = inet6_sk(sk);
#endif

	ip6_dst_store(sk, dst,
		      ipv6_addr_equal(&fl6->daddr, &sk->sk_v6_daddr) ?
		      &sk->sk_v6_daddr : NULL,
#ifdef CONFIG_IPV6_SUBTREES
		      ipv6_addr_equal(&fl6->saddr, &np->saddr) ?
		      &np->saddr :
#endif
		      NULL);
}

static bool ip6_redirect_nh_match(const struct fib6_result *res,
				  struct flowi6 *fl6,
				  const struct in6_addr *gw,
				  struct rt6_info **ret)
{
	const struct fib6_nh *nh = res->nh;

	if (nh->fib_nh_flags & RTNH_F_DEAD || !nh->fib_nh_gw_family ||
	    fl6->flowi6_oif != nh->fib_nh_dev->ifindex)
		return false;

	/* rt_cache's gateway might be different from its 'parent'
	 * in the case of an ip redirect.
	 * So we keep searching in the exception table if the gateway
	 * is different.
	 */
	if (!ipv6_addr_equal(gw, &nh->fib_nh_gw6)) {
		struct rt6_info *rt_cache;

		rt_cache = rt6_find_cached_rt(res, &fl6->daddr, &fl6->saddr);
		if (rt_cache &&
		    ipv6_addr_equal(gw, &rt_cache->rt6i_gateway)) {
			*ret = rt_cache;
			return true;
		}
		return false;
	}
	return true;
}

/* Handle redirects */
struct ip6rd_flowi {
	struct flowi6 fl6;
	struct in6_addr gateway;
};

static struct rt6_info *__ip6_route_redirect(struct net *net,
					     struct fib6_table *table,
					     struct flowi6 *fl6,
					     const struct sk_buff *skb,
					     int flags)
{
	struct ip6rd_flowi *rdfl = (struct ip6rd_flowi *)fl6;
	struct rt6_info *ret = NULL;
	struct fib6_result res = {};
	struct fib6_info *rt;
	struct fib6_node *fn;

	/* Get the "current" route for this destination and
	 * check if the redirect has come from appropriate router.
	 *
	 * RFC 4861 specifies that redirects should only be
	 * accepted if they come from the nexthop to the target.
	 * Due to the way the routes are chosen, this notion
	 * is a bit fuzzy and one might need to check all possible
	 * routes.
	 */

	rcu_read_lock();
	fn = fib6_node_lookup(&table->tb6_root, &fl6->daddr, &fl6->saddr);
restart:
	for_each_fib6_node_rt_rcu(fn) {
		res.f6i = rt;
		res.nh = &rt->fib6_nh;

		if (fib6_check_expired(rt))
			continue;
		if (rt->fib6_flags & RTF_REJECT)
			break;
		if (ip6_redirect_nh_match(&res, fl6, &rdfl->gateway, &ret))
			goto out;
	}

	if (!rt)
		rt = net->ipv6.fib6_null_entry;
	else if (rt->fib6_flags & RTF_REJECT) {
		ret = net->ipv6.ip6_null_entry;
		goto out;
	}

	if (rt == net->ipv6.fib6_null_entry) {
		fn = fib6_backtrack(fn, &fl6->saddr);
		if (fn)
			goto restart;
	}

	res.f6i = rt;
	res.nh = &rt->fib6_nh;
out:
	if (ret) {
		ip6_hold_safe(net, &ret);
	} else {
		res.fib6_flags = res.f6i->fib6_flags;
		res.fib6_type = res.f6i->fib6_type;
		ret = ip6_create_rt_rcu(&res);
	}

	rcu_read_unlock();

	trace_fib6_table_lookup(net, &res, table, fl6);
	return ret;
};

static struct dst_entry *ip6_route_redirect(struct net *net,
					    const struct flowi6 *fl6,
					    const struct sk_buff *skb,
					    const struct in6_addr *gateway)
{
	int flags = RT6_LOOKUP_F_HAS_SADDR;
	struct ip6rd_flowi rdfl;

	rdfl.fl6 = *fl6;
	rdfl.gateway = *gateway;

	return fib6_rule_lookup(net, &rdfl.fl6, skb,
				flags, __ip6_route_redirect);
}

void ip6_redirect(struct sk_buff *skb, struct net *net, int oif, u32 mark,
		  kuid_t uid)
{
	const struct ipv6hdr *iph = (struct ipv6hdr *) skb->data;
	struct dst_entry *dst;
	struct flowi6 fl6 = {
		.flowi6_iif = LOOPBACK_IFINDEX,
		.flowi6_oif = oif,
		.flowi6_mark = mark,
		.daddr = iph->daddr,
		.saddr = iph->saddr,
		.flowlabel = ip6_flowinfo(iph),
		.flowi6_uid = uid,
	};

	dst = ip6_route_redirect(net, &fl6, skb, &ipv6_hdr(skb)->saddr);
	rt6_do_redirect(dst, NULL, skb);
	dst_release(dst);
}
EXPORT_SYMBOL_GPL(ip6_redirect);

void ip6_redirect_no_header(struct sk_buff *skb, struct net *net, int oif)
{
	const struct ipv6hdr *iph = ipv6_hdr(skb);
	const struct rd_msg *msg = (struct rd_msg *)icmp6_hdr(skb);
	struct dst_entry *dst;
	struct flowi6 fl6 = {
		.flowi6_iif = LOOPBACK_IFINDEX,
		.flowi6_oif = oif,
		.daddr = msg->dest,
		.saddr = iph->daddr,
		.flowi6_uid = sock_net_uid(net, NULL),
	};

	dst = ip6_route_redirect(net, &fl6, skb, &iph->saddr);
	rt6_do_redirect(dst, NULL, skb);
	dst_release(dst);
}

void ip6_sk_redirect(struct sk_buff *skb, struct sock *sk)
{
	ip6_redirect(skb, sock_net(sk), sk->sk_bound_dev_if, sk->sk_mark,
		     sk->sk_uid);
}
EXPORT_SYMBOL_GPL(ip6_sk_redirect);

static unsigned int ip6_default_advmss(const struct dst_entry *dst)
{
	struct net_device *dev = dst->dev;
	unsigned int mtu = dst_mtu(dst);
	struct net *net = dev_net(dev);

	mtu -= sizeof(struct ipv6hdr) + sizeof(struct tcphdr);

	if (mtu < net->ipv6.sysctl.ip6_rt_min_advmss)
		mtu = net->ipv6.sysctl.ip6_rt_min_advmss;

	/*
	 * Maximal non-jumbo IPv6 payload is IPV6_MAXPLEN and
	 * corresponding MSS is IPV6_MAXPLEN - tcp_header_size.
	 * IPV6_MAXPLEN is also valid and means: "any MSS,
	 * rely only on pmtu discovery"
	 */
	if (mtu > IPV6_MAXPLEN - sizeof(struct tcphdr))
		mtu = IPV6_MAXPLEN;
	return mtu;
}

static unsigned int ip6_mtu(const struct dst_entry *dst)
{
	struct inet6_dev *idev;
	unsigned int mtu;

	mtu = dst_metric_raw(dst, RTAX_MTU);
	if (mtu)
		goto out;

	mtu = IPV6_MIN_MTU;

	rcu_read_lock();
	idev = __in6_dev_get(dst->dev);
	if (idev)
		mtu = idev->cnf.mtu6;
	rcu_read_unlock();

out:
	mtu = min_t(unsigned int, mtu, IP6_MAX_MTU);

	return mtu - lwtunnel_headroom(dst->lwtstate, mtu);
}

/* MTU selection:
 * 1. mtu on route is locked - use it
 * 2. mtu from nexthop exception
 * 3. mtu from egress device
 *
 * based on ip6_dst_mtu_forward and exception logic of
 * rt6_find_cached_rt; called with rcu_read_lock
 */
u32 ip6_mtu_from_fib6(const struct fib6_result *res,
		      const struct in6_addr *daddr,
		      const struct in6_addr *saddr)
{
	struct rt6_exception_bucket *bucket;
	const struct fib6_nh *nh = res->nh;
	struct fib6_info *f6i = res->f6i;
	const struct in6_addr *src_key;
	struct rt6_exception *rt6_ex;
	struct inet6_dev *idev;
	u32 mtu = 0;

	if (unlikely(fib6_metric_locked(f6i, RTAX_MTU))) {
		mtu = f6i->fib6_pmtu;
		if (mtu)
			goto out;
	}

	src_key = NULL;
#ifdef CONFIG_IPV6_SUBTREES
	if (f6i->fib6_src.plen)
		src_key = saddr;
#endif

	bucket = rcu_dereference(f6i->rt6i_exception_bucket);
	rt6_ex = __rt6_find_exception_rcu(&bucket, daddr, src_key);
	if (rt6_ex && !rt6_check_expired(rt6_ex->rt6i))
		mtu = dst_metric_raw(&rt6_ex->rt6i->dst, RTAX_MTU);

	if (likely(!mtu)) {
		struct net_device *dev = nh->fib_nh_dev;

		mtu = IPV6_MIN_MTU;
		idev = __in6_dev_get(dev);
		if (idev && idev->cnf.mtu6 > mtu)
			mtu = idev->cnf.mtu6;
	}

	mtu = min_t(unsigned int, mtu, IP6_MAX_MTU);
out:
	return mtu - lwtunnel_headroom(nh->fib_nh_lws, mtu);
}

struct dst_entry *icmp6_dst_alloc(struct net_device *dev,
				  struct flowi6 *fl6)
{
	struct dst_entry *dst;
	struct rt6_info *rt;
	struct inet6_dev *idev = in6_dev_get(dev);
	struct net *net = dev_net(dev);

	if (unlikely(!idev))
		return ERR_PTR(-ENODEV);

	rt = ip6_dst_alloc(net, dev, 0);
	if (unlikely(!rt)) {
		in6_dev_put(idev);
		dst = ERR_PTR(-ENOMEM);
		goto out;
	}

	rt->dst.flags |= DST_HOST;
	rt->dst.input = ip6_input;
	rt->dst.output  = ip6_output;
	rt->rt6i_gateway  = fl6->daddr;
	rt->rt6i_dst.addr = fl6->daddr;
	rt->rt6i_dst.plen = 128;
	rt->rt6i_idev     = idev;
	dst_metric_set(&rt->dst, RTAX_HOPLIMIT, 0);

	/* Add this dst into uncached_list so that rt6_disable_ip() can
	 * do proper release of the net_device
	 */
	rt6_uncached_list_add(rt);
	atomic_inc(&net->ipv6.rt6_stats->fib_rt_uncache);

	dst = xfrm_lookup(net, &rt->dst, flowi6_to_flowi(fl6), NULL, 0);

out:
	return dst;
}

static int ip6_dst_gc(struct dst_ops *ops)
{
	struct net *net = container_of(ops, struct net, ipv6.ip6_dst_ops);
	int rt_min_interval = net->ipv6.sysctl.ip6_rt_gc_min_interval;
	int rt_max_size = net->ipv6.sysctl.ip6_rt_max_size;
	int rt_elasticity = net->ipv6.sysctl.ip6_rt_gc_elasticity;
	int rt_gc_timeout = net->ipv6.sysctl.ip6_rt_gc_timeout;
	unsigned long rt_last_gc = net->ipv6.ip6_rt_last_gc;
	int entries;

	entries = dst_entries_get_fast(ops);
	if (time_after(rt_last_gc + rt_min_interval, jiffies) &&
	    entries <= rt_max_size)
		goto out;

	net->ipv6.ip6_rt_gc_expire++;
	fib6_run_gc(net->ipv6.ip6_rt_gc_expire, net, true);
	entries = dst_entries_get_slow(ops);
	if (entries < ops->gc_thresh)
		net->ipv6.ip6_rt_gc_expire = rt_gc_timeout>>1;
out:
	net->ipv6.ip6_rt_gc_expire -= net->ipv6.ip6_rt_gc_expire>>rt_elasticity;
	return entries > rt_max_size;
}

static struct rt6_info *ip6_nh_lookup_table(struct net *net,
					    struct fib6_config *cfg,
					    const struct in6_addr *gw_addr,
					    u32 tbid, int flags)
{
	struct flowi6 fl6 = {
		.flowi6_oif = cfg->fc_ifindex,
		.daddr = *gw_addr,
		.saddr = cfg->fc_prefsrc,
	};
	struct fib6_table *table;
	struct rt6_info *rt;

	table = fib6_get_table(net, tbid);
	if (!table)
		return NULL;

	if (!ipv6_addr_any(&cfg->fc_prefsrc))
		flags |= RT6_LOOKUP_F_HAS_SADDR;

	flags |= RT6_LOOKUP_F_IGNORE_LINKSTATE;
	rt = ip6_pol_route(net, table, cfg->fc_ifindex, &fl6, NULL, flags);

	/* if table lookup failed, fall back to full lookup */
	if (rt == net->ipv6.ip6_null_entry) {
		ip6_rt_put(rt);
		rt = NULL;
	}

	return rt;
}

static int ip6_route_check_nh_onlink(struct net *net,
				     struct fib6_config *cfg,
				     const struct net_device *dev,
				     struct netlink_ext_ack *extack)
{
	u32 tbid = l3mdev_fib_table(dev) ? : RT_TABLE_MAIN;
	const struct in6_addr *gw_addr = &cfg->fc_gateway;
	u32 flags = RTF_LOCAL | RTF_ANYCAST | RTF_REJECT;
	struct fib6_info *from;
	struct rt6_info *grt;
	int err;

	err = 0;
	grt = ip6_nh_lookup_table(net, cfg, gw_addr, tbid, 0);
	if (grt) {
		rcu_read_lock();
		from = rcu_dereference(grt->from);
		if (!grt->dst.error &&
		    /* ignore match if it is the default route */
		    from && !ipv6_addr_any(&from->fib6_dst.addr) &&
		    (grt->rt6i_flags & flags || dev != grt->dst.dev)) {
			NL_SET_ERR_MSG(extack,
				       "Nexthop has invalid gateway or device mismatch");
			err = -EINVAL;
		}
		rcu_read_unlock();

		ip6_rt_put(grt);
	}

	return err;
}

static int ip6_route_check_nh(struct net *net,
			      struct fib6_config *cfg,
			      struct net_device **_dev,
			      struct inet6_dev **idev)
{
	const struct in6_addr *gw_addr = &cfg->fc_gateway;
	struct net_device *dev = _dev ? *_dev : NULL;
	struct rt6_info *grt = NULL;
	int err = -EHOSTUNREACH;

	if (cfg->fc_table) {
		int flags = RT6_LOOKUP_F_IFACE;

		grt = ip6_nh_lookup_table(net, cfg, gw_addr,
					  cfg->fc_table, flags);
		if (grt) {
			if (grt->rt6i_flags & RTF_GATEWAY ||
			    (dev && dev != grt->dst.dev)) {
				ip6_rt_put(grt);
				grt = NULL;
			}
		}
	}

	if (!grt)
		grt = rt6_lookup(net, gw_addr, NULL, cfg->fc_ifindex, NULL, 1);

	if (!grt)
		goto out;

	if (dev) {
		if (dev != grt->dst.dev) {
			ip6_rt_put(grt);
			goto out;
		}
	} else {
		*_dev = dev = grt->dst.dev;
		*idev = grt->rt6i_idev;
		dev_hold(dev);
		in6_dev_hold(grt->rt6i_idev);
	}

	if (!(grt->rt6i_flags & RTF_GATEWAY))
		err = 0;

	ip6_rt_put(grt);

out:
	return err;
}

static int ip6_validate_gw(struct net *net, struct fib6_config *cfg,
			   struct net_device **_dev, struct inet6_dev **idev,
			   struct netlink_ext_ack *extack)
{
	const struct in6_addr *gw_addr = &cfg->fc_gateway;
	int gwa_type = ipv6_addr_type(gw_addr);
	bool skip_dev = gwa_type & IPV6_ADDR_LINKLOCAL ? false : true;
	const struct net_device *dev = *_dev;
	bool need_addr_check = !dev;
	int err = -EINVAL;

	/* if gw_addr is local we will fail to detect this in case
	 * address is still TENTATIVE (DAD in progress). rt6_lookup()
	 * will return already-added prefix route via interface that
	 * prefix route was assigned to, which might be non-loopback.
	 */
	if (dev &&
	    ipv6_chk_addr_and_flags(net, gw_addr, dev, skip_dev, 0, 0)) {
		NL_SET_ERR_MSG(extack, "Gateway can not be a local address");
		goto out;
	}

	if (gwa_type != (IPV6_ADDR_LINKLOCAL | IPV6_ADDR_UNICAST)) {
		/* IPv6 strictly inhibits using not link-local
		 * addresses as nexthop address.
		 * Otherwise, router will not able to send redirects.
		 * It is very good, but in some (rare!) circumstances
		 * (SIT, PtP, NBMA NOARP links) it is handy to allow
		 * some exceptions. --ANK
		 * We allow IPv4-mapped nexthops to support RFC4798-type
		 * addressing
		 */
		if (!(gwa_type & (IPV6_ADDR_UNICAST | IPV6_ADDR_MAPPED))) {
			NL_SET_ERR_MSG(extack, "Invalid gateway address");
			goto out;
		}

		if (cfg->fc_flags & RTNH_F_ONLINK)
			err = ip6_route_check_nh_onlink(net, cfg, dev, extack);
		else
			err = ip6_route_check_nh(net, cfg, _dev, idev);

		if (err)
			goto out;
	}

	/* reload in case device was changed */
	dev = *_dev;

	err = -EINVAL;
	if (!dev) {
		NL_SET_ERR_MSG(extack, "Egress device not specified");
		goto out;
	} else if (dev->flags & IFF_LOOPBACK) {
		NL_SET_ERR_MSG(extack,
			       "Egress device can not be loopback device for this route");
		goto out;
	}

	/* if we did not check gw_addr above, do so now that the
	 * egress device has been resolved.
	 */
	if (need_addr_check &&
	    ipv6_chk_addr_and_flags(net, gw_addr, dev, skip_dev, 0, 0)) {
		NL_SET_ERR_MSG(extack, "Gateway can not be a local address");
		goto out;
	}

	err = 0;
out:
	return err;
}

static bool fib6_is_reject(u32 flags, struct net_device *dev, int addr_type)
{
	if ((flags & RTF_REJECT) ||
	    (dev && (dev->flags & IFF_LOOPBACK) &&
	     !(addr_type & IPV6_ADDR_LOOPBACK) &&
	     !(flags & RTF_LOCAL)))
		return true;

	return false;
}

int fib6_nh_init(struct net *net, struct fib6_nh *fib6_nh,
		 struct fib6_config *cfg, gfp_t gfp_flags,
		 struct netlink_ext_ack *extack)
{
	struct net_device *dev = NULL;
	struct inet6_dev *idev = NULL;
	int addr_type;
	int err;

	fib6_nh->fib_nh_family = AF_INET6;

	err = -ENODEV;
	if (cfg->fc_ifindex) {
		dev = dev_get_by_index(net, cfg->fc_ifindex);
		if (!dev)
			goto out;
		idev = in6_dev_get(dev);
		if (!idev)
			goto out;
	}

	if (cfg->fc_flags & RTNH_F_ONLINK) {
		if (!dev) {
			NL_SET_ERR_MSG(extack,
				       "Nexthop device required for onlink");
			goto out;
		}

		if (!(dev->flags & IFF_UP)) {
			NL_SET_ERR_MSG(extack, "Nexthop device is not up");
			err = -ENETDOWN;