// SPDX-License-Identifier: GPL-2.0
/* Generic nexthop implementation
 *
 * Copyright (c) 2017-19 Cumulus Networks
 * Copyright (c) 2017-19 David Ahern <dsa@cumulusnetworks.com>
 */

#include <linux/nexthop.h>
#include <linux/rtnetlink.h>
#include <linux/slab.h>
#include <net/arp.h>
#include <net/ipv6_stubs.h>
#include <net/lwtunnel.h>
#include <net/ndisc.h>
#include <net/nexthop.h>
#include <net/route.h>
#include <net/sock.h>

#define NH_RES_DEFAULT_IDLE_TIMER       (120 * HZ)
#define NH_RES_DEFAULT_UNBALANCED_TIMER 0       /* No forced rebalancing. */

static void remove_nexthop(struct net *net, struct nexthop *nh,
                           struct nl_info *nlinfo);

#define NH_DEV_HASHBITS  8
#define NH_DEV_HASHSIZE (1U << NH_DEV_HASHBITS)

static const struct nla_policy rtm_nh_policy_new[] = {
        [NHA_ID]                = { .type = NLA_U32 },
        [NHA_GROUP]             = { .type = NLA_BINARY },
        [NHA_GROUP_TYPE]        = { .type = NLA_U16 },
        [NHA_BLACKHOLE]         = { .type = NLA_FLAG },
        [NHA_OIF]               = { .type = NLA_U32 },
        [NHA_GATEWAY]           = { .type = NLA_BINARY },
        [NHA_ENCAP_TYPE]        = { .type = NLA_U16 },
        [NHA_ENCAP]             = { .type = NLA_NESTED },
        [NHA_FDB]               = { .type = NLA_FLAG },
        [NHA_RES_GROUP]         = { .type = NLA_NESTED },
};

static const struct nla_policy rtm_nh_policy_get[] = {
        [NHA_ID]                = { .type = NLA_U32 },
};

static const struct nla_policy rtm_nh_policy_dump[] = {
        [NHA_OIF]               = { .type = NLA_U32 },
        [NHA_GROUPS]            = { .type = NLA_FLAG },
        [NHA_MASTER]            = { .type = NLA_U32 },
        [NHA_FDB]               = { .type = NLA_FLAG },
};

static const struct nla_policy rtm_nh_res_policy_new[] = {
        [NHA_RES_GROUP_BUCKETS]                 = { .type = NLA_U16 },
        [NHA_RES_GROUP_IDLE_TIMER]              = { .type = NLA_U32 },
        [NHA_RES_GROUP_UNBALANCED_TIMER]        = { .type = NLA_U32 },
};

static const struct nla_policy rtm_nh_policy_dump_bucket[] = {
        [NHA_ID]                = { .type = NLA_U32 },
        [NHA_OIF]               = { .type = NLA_U32 },
        [NHA_MASTER]            = { .type = NLA_U32 },
        [NHA_RES_BUCKET]        = { .type = NLA_NESTED },
};

static const struct nla_policy rtm_nh_res_bucket_policy_dump[] = {
        [NHA_RES_BUCKET_NH_ID]  = { .type = NLA_U32 },
};

static const struct nla_policy rtm_nh_policy_get_bucket[] = {
        [NHA_ID]                = { .type = NLA_U32 },
        [NHA_RES_BUCKET]        = { .type = NLA_NESTED },
};

static const struct nla_policy rtm_nh_res_bucket_policy_get[] = {
        [NHA_RES_BUCKET_INDEX]  = { .type = NLA_U16 },
};

static bool nexthop_notifiers_is_empty(struct net *net)
{
        return !net->nexthop.notifier_chain.head;
}

static void
__nh_notifier_single_info_init(struct nh_notifier_single_info *nh_info,
                               const struct nh_info *nhi)
{
        nh_info->dev = nhi->fib_nhc.nhc_dev;
        nh_info->gw_family = nhi->fib_nhc.nhc_gw_family;
        if (nh_info->gw_family == AF_INET)
                nh_info->ipv4 = nhi->fib_nhc.nhc_gw.ipv4;
        else if (nh_info->gw_family == AF_INET6)
                nh_info->ipv6 = nhi->fib_nhc.nhc_gw.ipv6;

        nh_info->is_reject = nhi->reject_nh;
        nh_info->is_fdb = nhi->fdb_nh;
        nh_info->has_encap = !!nhi->fib_nhc.nhc_lwtstate;
}

static int nh_notifier_single_info_init(struct nh_notifier_info *info,
                                        const struct nexthop *nh)
{
        struct nh_info *nhi = rtnl_dereference(nh->nh_info);

        info->type = NH_NOTIFIER_INFO_TYPE_SINGLE;
        info->nh = kzalloc(sizeof(*info->nh), GFP_KERNEL);
        if (!info->nh)
                return -ENOMEM;

        __nh_notifier_single_info_init(info->nh, nhi);

        return 0;
}

static void nh_notifier_single_info_fini(struct nh_notifier_info *info)
{
        kfree(info->nh);
}

static int nh_notifier_mpath_info_init(struct nh_notifier_info *info,
                                       struct nh_group *nhg)
{
        u16 num_nh = nhg->num_nh;
        int i;

        info->type = NH_NOTIFIER_INFO_TYPE_GRP;
        info->nh_grp = kzalloc(struct_size(info->nh_grp, nh_entries, num_nh),
                               GFP_KERNEL);
        if (!info->nh_grp)
                return -ENOMEM;

        info->nh_grp->num_nh = num_nh;
        info->nh_grp->is_fdb = nhg->fdb_nh;

        for (i = 0; i < num_nh; i++) {
                struct nh_grp_entry *nhge = &nhg->nh_entries[i];
                struct nh_info *nhi;

                nhi = rtnl_dereference(nhge->nh->nh_info);
                info->nh_grp->nh_entries[i].id = nhge->nh->id;
                info->nh_grp->nh_entries[i].weight = nhge->weight;
                __nh_notifier_single_info_init(&info->nh_grp->nh_entries[i].nh,
                                               nhi);
        }

        return 0;
}

static int nh_notifier_res_table_info_init(struct nh_notifier_info *info,
                                           struct nh_group *nhg)
{
        struct nh_res_table *res_table = rtnl_dereference(nhg->res_table);
        u16 num_nh_buckets = res_table->num_nh_buckets;
        unsigned long size;
        u16 i;

        info->type = NH_NOTIFIER_INFO_TYPE_RES_TABLE;
        size = struct_size(info->nh_res_table, nhs, num_nh_buckets);
        info->nh_res_table = __vmalloc(size, GFP_KERNEL | __GFP_ZERO |
                                       __GFP_NOWARN);
        if (!info->nh_res_table)
                return -ENOMEM;

        info->nh_res_table->num_nh_buckets = num_nh_buckets;

        for (i = 0; i < num_nh_buckets; i++) {
                struct nh_res_bucket *bucket = &res_table->nh_buckets[i];
                struct nh_grp_entry *nhge;
                struct nh_info *nhi;

                nhge = rtnl_dereference(bucket->nh_entry);
                nhi = rtnl_dereference(nhge->nh->nh_info);
                __nh_notifier_single_info_init(&info->nh_res_table->nhs[i],
                                               nhi);
        }

        return 0;
}

static int nh_notifier_grp_info_init(struct nh_notifier_info *info,
                                     const struct nexthop *nh)
{
        struct nh_group *nhg = rtnl_dereference(nh->nh_grp);

        if (nhg->hash_threshold)
                return nh_notifier_mpath_info_init(info, nhg);
        else if (nhg->resilient)
                return nh_notifier_res_table_info_init(info, nhg);
        return -EINVAL;
}

static void nh_notifier_grp_info_fini(struct nh_notifier_info *info,
                                      const struct nexthop *nh)
{
        struct nh_group *nhg = rtnl_dereference(nh->nh_grp);

        if (nhg->hash_threshold)
                kfree(info->nh_grp);
        else if (nhg->resilient)
                vfree(info->nh_res_table);
}

static int nh_notifier_info_init(struct nh_notifier_info *info,
                                 const struct nexthop *nh)
{
        info->id = nh->id;

        if (nh->is_group)
                return nh_notifier_grp_info_init(info, nh);
        else
                return nh_notifier_single_info_init(info, nh);
}

static void nh_notifier_info_fini(struct nh_notifier_info *info,
                                  const struct nexthop *nh)
{
        if (nh->is_group)
                nh_notifier_grp_info_fini(info, nh);
        else
                nh_notifier_single_info_fini(info);
}

static int call_nexthop_notifiers(struct net *net,
                                  enum nexthop_event_type event_type,
                                  struct nexthop *nh,
                                  struct netlink_ext_ack *extack)
{
        struct nh_notifier_info info = {
                .net = net,
                .extack = extack,
        };
        int err;

        ASSERT_RTNL();

        if (nexthop_notifiers_is_empty(net))
                return 0;

        err = nh_notifier_info_init(&info, nh);
        if (err) {
                NL_SET_ERR_MSG(extack, "Failed to initialize nexthop notifier info");
                return err;
        }

        err = blocking_notifier_call_chain(&net->nexthop.notifier_chain,
                                           event_type, &info);
        nh_notifier_info_fini(&info, nh);

        return notifier_to_errno(err);
}

static int
nh_notifier_res_bucket_idle_timer_get(const struct nh_notifier_info *info,
                                      bool force, unsigned int *p_idle_timer_ms)
{
        struct nh_res_table *res_table;
        struct nh_group *nhg;
        struct nexthop *nh;
        int err = 0;

        /* When 'force' is false, nexthop bucket replacement is performed
         * because the bucket was deemed to be idle. In this case, capable
         * listeners can choose to perform an atomic replacement: The bucket is
         * only replaced if it is inactive. However, if the idle timer interval
         * is smaller than the interval in which a listener is querying
         * buckets' activity from the device, then atomic replacement should
         * not be tried. Pass the idle timer value to listeners, so that they
         * could determine which type of replacement to perform.
         */
        if (force) {
                *p_idle_timer_ms = 0;
                return 0;
        }

        rcu_read_lock();

        nh = nexthop_find_by_id(info->net, info->id);
        if (!nh) {
                err = -EINVAL;
                goto out;
        }

        nhg = rcu_dereference(nh->nh_grp);
        res_table = rcu_dereference(nhg->res_table);
        *p_idle_timer_ms = jiffies_to_msecs(res_table->idle_timer);

out:
        rcu_read_unlock();

        return err;
}

static int nh_notifier_res_bucket_info_init(struct nh_notifier_info *info,
                                            u16 bucket_index, bool force,
                                            struct nh_info *oldi,
                                            struct nh_info *newi)
{
        unsigned int idle_timer_ms;
        int err;

        err = nh_notifier_res_bucket_idle_timer_get(info, force,
                                                    &idle_timer_ms);
        if (err)
                return err;

        info->type = NH_NOTIFIER_INFO_TYPE_RES_BUCKET;
        info->nh_res_bucket = kzalloc(sizeof(*info->nh_res_bucket),
                                      GFP_KERNEL);
        if (!info->nh_res_bucket)
                return -ENOMEM;

        info->nh_res_bucket->bucket_index = bucket_index;
        info->nh_res_bucket->idle_timer_ms = idle_timer_ms;
        info->nh_res_bucket->force = force;
        __nh_notifier_single_info_init(&info->nh_res_bucket->old_nh, oldi);
        __nh_notifier_single_info_init(&info->nh_res_bucket->new_nh, newi);
        return 0;
}

static void nh_notifier_res_bucket_info_fini(struct nh_notifier_info *info)
{
        kfree(info->nh_res_bucket);
}

static int __call_nexthop_res_bucket_notifiers(struct net *net, u32 nhg_id,
                                               u16 bucket_index, bool force,
                                               struct nh_info *oldi,
                                               struct nh_info *newi,
                                               struct netlink_ext_ack *extack)
{
        struct nh_notifier_info info = {
                .net = net,
                .extack = extack,
                .id = nhg_id,
        };
        int err;

        if (nexthop_notifiers_is_empty(net))
                return 0;

        err = nh_notifier_res_bucket_info_init(&info, bucket_index, force,
                                               oldi, newi);
        if (err)
                return err;

        err = blocking_notifier_call_chain(&net->nexthop.notifier_chain,
                                           NEXTHOP_EVENT_BUCKET_REPLACE, &info);
        nh_notifier_res_bucket_info_fini(&info);

        return notifier_to_errno(err);
}

/* There are three users of RES_TABLE, and NHs etc. referenced from there:
 *
 * 1) a collection of callbacks for NH maintenance. This operates under
 *    RTNL,
 * 2) the delayed work that gradually balances the resilient table,
 * 3) and nexthop_select_path(), operating under RCU.
 *
 * Both the delayed work and the RTNL block are writers, and need to
 * maintain mutual exclusion. Since there are only two and well-known
 * writers for each table, the RTNL code can make sure it has exclusive
 * access thus:
 *
 * - Have the DW operate without locking;
 * - synchronously cancel the DW;
 * - do the writing;
 * - if the write was not actually a delete, call upkeep, which schedules
 *   DW again if necessary.
 *
 * The functions that are always called from the RTNL context use
 * rtnl_dereference(). The functions that can also be called from the DW do
 * a raw dereference and rely on the above mutual exclusion scheme.
 */
#define nh_res_dereference(p) (rcu_dereference_raw(p))

static int call_nexthop_res_bucket_notifiers(struct net *net, u32 nhg_id,
                                             u16 bucket_index, bool force,
                                             struct nexthop *old_nh,
                                             struct nexthop *new_nh,
                                             struct netlink_ext_ack *extack)
{
        struct nh_info *oldi = nh_res_dereference(old_nh->nh_info);
        struct nh_info *newi = nh_res_dereference(new_nh->nh_info);

        return __call_nexthop_res_bucket_notifiers(net, nhg_id, bucket_index,
                                                   force, oldi, newi, extack);
}

static int call_nexthop_res_table_notifiers(struct net *net, struct nexthop *nh,
                                            struct netlink_ext_ack *extack)
{
        struct nh_notifier_info info = {
                .net = net,
                .extack = extack,
        };
        struct nh_group *nhg;
        int err;

        ASSERT_RTNL();

        if (nexthop_notifiers_is_empty(net))
                return 0;

        /* At this point, the nexthop buckets are still not populated. Only
         * emit a notification with the logical nexthops, so that a listener
         * could potentially veto it in case of unsupported configuration.
         */
        nhg = rtnl_dereference(nh->nh_grp);
        err = nh_notifier_mpath_info_init(&info, nhg);
        if (err) {
                NL_SET_ERR_MSG(extack, "Failed to initialize nexthop notifier info");
                return err;
        }

        err = blocking_notifier_call_chain(&net->nexthop.notifier_chain,
                                           NEXTHOP_EVENT_RES_TABLE_PRE_REPLACE,
                                           &info);
        kfree(info.nh_grp);

        return notifier_to_errno(err);
}

static int call_nexthop_notifier(struct notifier_block *nb, struct net *net,
                                 enum nexthop_event_type event_type,
                                 struct nexthop *nh,
                                 struct netlink_ext_ack *extack)
{
        struct nh_notifier_info info = {
                .net = net,
                .extack = extack,
        };
        int err;

        err = nh_notifier_info_init(&info, nh);
        if (err)
                return err;

        err = nb->notifier_call(nb, event_type, &info);
        nh_notifier_info_fini(&info, nh);

        return notifier_to_errno(err);
}

static unsigned int nh_dev_hashfn(unsigned int val)
{
        unsigned int mask = NH_DEV_HASHSIZE - 1;

        return (val ^
                (val >> NH_DEV_HASHBITS) ^
                (val >> (NH_DEV_HASHBITS * 2))) & mask;
}

static void nexthop_devhash_add(struct net *net, struct nh_info *nhi)
{
        struct net_device *dev = nhi->fib_nhc.nhc_dev;
        struct hlist_head *head;
        unsigned int hash;

        WARN_ON(!dev);

        hash = nh_dev_hashfn(dev->ifindex);
        head = &net->nexthop.devhash[hash];
        hlist_add_head(&nhi->dev_hash, head);
}

static void nexthop_free_group(struct nexthop *nh)
{
        struct nh_group *nhg;
        int i;

        nhg = rcu_dereference_raw(nh->nh_grp);
        for (i = 0; i < nhg->num_nh; ++i) {
                struct nh_grp_entry *nhge = &nhg->nh_entries[i];

                WARN_ON(!list_empty(&nhge->nh_list));
                nexthop_put(nhge->nh);
        }

        WARN_ON(nhg->spare == nhg);

        if (nhg->resilient)
                vfree(rcu_dereference_raw(nhg->res_table));

        kfree(nhg->spare);
        kfree(nhg);
}

static void nexthop_free_single(struct nexthop *nh)
{
        struct nh_info *nhi;

        nhi = rcu_dereference_raw(nh->nh_info);
        switch (nhi->family) {
        case AF_INET:
                fib_nh_release(nh->net, &nhi->fib_nh);
                break;
        case AF_INET6:
                ipv6_stub->fib6_nh_release(&nhi->fib6_nh);
                break;
        }
        kfree(nhi);
}

void nexthop_free_rcu(struct rcu_head *head)
{
        struct nexthop *nh = container_of(head, struct nexthop, rcu);

        if (nh->is_group)
                nexthop_free_group(nh);
        else
                nexthop_free_single(nh);

        kfree(nh);
}
EXPORT_SYMBOL_GPL(nexthop_free_rcu);

static struct nexthop *nexthop_alloc(void)
{
        struct nexthop *nh;

        nh = kzalloc(sizeof(struct nexthop), GFP_KERNEL);
        if (nh) {
                INIT_LIST_HEAD(&nh->fi_list);
                INIT_LIST_HEAD(&nh->f6i_list);
                INIT_LIST_HEAD(&nh->grp_list);
                INIT_LIST_HEAD(&nh->fdb_list);
        }
        return nh;
}

static struct nh_group *nexthop_grp_alloc(u16 num_nh)
{
        struct nh_group *nhg;

        nhg = kzalloc(struct_size(nhg, nh_entries, num_nh), GFP_KERNEL);
        if (nhg)
                nhg->num_nh = num_nh;

        return nhg;
}

static void nh_res_table_upkeep_dw(struct work_struct *work);

static struct nh_res_table *
nexthop_res_table_alloc(struct net *net, u32 nhg_id, struct nh_config *cfg)
{
        const u16 num_nh_buckets = cfg->nh_grp_res_num_buckets;
        struct nh_res_table *res_table;
        unsigned long size;

        size = struct_size(res_table, nh_buckets, num_nh_buckets);
        res_table = __vmalloc(size, GFP_KERNEL | __GFP_ZERO | __GFP_NOWARN);
        if (!res_table)
                return NULL;

        res_table->net = net;
        res_table->nhg_id = nhg_id;
        INIT_DELAYED_WORK(&res_table->upkeep_dw, &nh_res_table_upkeep_dw);
        INIT_LIST_HEAD(&res_table->uw_nh_entries);
        res_table->idle_timer = cfg->nh_grp_res_idle_timer;
        res_table->unbalanced_timer = cfg->nh_grp_res_unbalanced_timer;
        res_table->num_nh_buckets = num_nh_buckets;
        return res_table;
}

static void nh_base_seq_inc(struct net *net)
{
        while (++net->nexthop.seq == 0)
                ;
}

/* no reference taken; rcu lock or rtnl must be held */
struct nexthop *nexthop_find_by_id(struct net *net, u32 id)
{
        struct rb_node **pp, *parent = NULL, *next;

        pp = &net->nexthop.rb_root.rb_node;
        while (1) {
                struct nexthop *nh;

                next = rcu_dereference_raw(*pp);
                if (!next)
                        break;
                parent = next;

                nh = rb_entry(parent, struct nexthop, rb_node);
                if (id < nh->id)
                        pp = &next->rb_left;
                else if (id > nh->id)
                        pp = &next->rb_right;
                else
                        return nh;
        }
        return NULL;
}
EXPORT_SYMBOL_GPL(nexthop_find_by_id);

/* used for auto id allocation; called with rtnl held */
static u32 nh_find_unused_id(struct net *net)
{
        u32 id_start = net->nexthop.last_id_allocated;

        while (1) {
                net->nexthop.last_id_allocated++;
                if (net->nexthop.last_id_allocated == id_start)
                        break;

                if (!nexthop_find_by_id(net, net->nexthop.last_id_allocated))
                        return net->nexthop.last_id_allocated;
        }
        return 0;
}

static void nh_res_time_set_deadline(unsigned long next_time,
                                     unsigned long *deadline)
{
        if (time_before(next_time, *deadline))
                *deadline = next_time;
}

static clock_t nh_res_table_unbalanced_time(struct nh_res_table *res_table)
{
        if (list_empty(&res_table->uw_nh_entries))
                return 0;
        return jiffies_delta_to_clock_t(jiffies - res_table->unbalanced_since);
}

static int nla_put_nh_group_res(struct sk_buff *skb, struct nh_group *nhg)
{
        struct nh_res_table *res_table = rtnl_dereference(nhg->res_table);
        struct nlattr *nest;

        nest = nla_nest_start(skb, NHA_RES_GROUP);
        if (!nest)
                return -EMSGSIZE;

        if (nla_put_u16(skb, NHA_RES_GROUP_BUCKETS,
                        res_table->num_nh_buckets) ||
            nla_put_u32(skb, NHA_RES_GROUP_IDLE_TIMER,
                        jiffies_to_clock_t(res_table->idle_timer)) ||
            nla_put_u32(skb, NHA_RES_GROUP_UNBALANCED_TIMER,
                        jiffies_to_clock_t(res_table->unbalanced_timer)) ||
            nla_put_u64_64bit(skb, NHA_RES_GROUP_UNBALANCED_TIME,
                              nh_res_table_unbalanced_time(res_table),
                              NHA_RES_GROUP_PAD))
                goto nla_put_failure;

        nla_nest_end(skb, nest);
        return 0;

nla_put_failure:
        nla_nest_cancel(skb, nest);
        return -EMSGSIZE;
}

static int nla_put_nh_group(struct sk_buff *skb, struct nh_group *nhg)
{
        struct nexthop_grp *p;
        size_t len = nhg->num_nh * sizeof(*p);
        struct nlattr *nla;
        u16 group_type = 0;
        int i;

        if (nhg->hash_threshold)
                group_type = NEXTHOP_GRP_TYPE_MPATH;
        else if (nhg->resilient)
                group_type = NEXTHOP_GRP_TYPE_RES;

        if (nla_put_u16(skb, NHA_GROUP_TYPE, group_type))
                goto nla_put_failure;

        nla = nla_reserve(skb, NHA_GROUP, len);
        if (!nla)
                goto nla_put_failure;

        p = nla_data(nla);
        for (i = 0; i < nhg->num_nh; ++i) {
                p->id = nhg->nh_entries[i].nh->id;
                p->weight = nhg->nh_entries[i].weight - 1;
                p += 1;
        }

        if (nhg->resilient && nla_put_nh_group_res(skb, nhg))
                goto nla_put_failure;

        return 0;

nla_put_failure:
        return -EMSGSIZE;
}

static int nh_fill_node(struct sk_buff *skb, struct nexthop *nh,
                        int event, u32 portid, u32 seq, unsigned int nlflags)
{
        struct fib6_nh *fib6_nh;
        struct fib_nh *fib_nh;
        struct nlmsghdr *nlh;
        struct nh_info *nhi;
        struct nhmsg *nhm;

        nlh = nlmsg_put(skb, portid, seq, event, sizeof(*nhm), nlflags);
        if (!nlh)
                return -EMSGSIZE;

        nhm = nlmsg_data(nlh);
        nhm->nh_family = AF_UNSPEC;
        nhm->nh_flags = nh->nh_flags;
        nhm->nh_protocol = nh->protocol;
        nhm->nh_scope = 0;
        nhm->resvd = 0;

        if (nla_put_u32(skb, NHA_ID, nh->id))
                goto nla_put_failure;

        if (nh->is_group) {
                struct nh_group *nhg = rtnl_dereference(nh->nh_grp);

                if (nhg->fdb_nh && nla_put_flag(skb, NHA_FDB))
                        goto nla_put_failure;
                if (nla_put_nh_group(skb, nhg))
                        goto nla_put_failure;
                goto out;
        }

        nhi = rtnl_dereference(nh->nh_info);
        nhm->nh_family = nhi->family;
        if (nhi->reject_nh) {
                if (nla_put_flag(skb, NHA_BLACKHOLE))
                        goto nla_put_failure;
                goto out;
        } else if (nhi->fdb_nh) {
                if (nla_put_flag(skb, NHA_FDB))
                        goto nla_put_failure;
        } else {
                const struct net_device *dev;

                dev = nhi->fib_nhc.nhc_dev;
                if (dev && nla_put_u32(skb, NHA_OIF, dev->ifindex))
                        goto nla_put_failure;
        }

        nhm->nh_scope = nhi->fib_nhc.nhc_scope;
        switch (nhi->family) {
        case AF_INET:
                fib_nh = &nhi->fib_nh;
                if (fib_nh->fib_nh_gw_family &&
                    nla_put_be32(skb, NHA_GATEWAY, fib_nh->fib_nh_gw4))
                        goto nla_put_failure;
                break;

        case AF_INET6:
                fib6_nh = &nhi->fib6_nh;
                if (fib6_nh->fib_nh_gw_family &&
                    nla_put_in6_addr(skb, NHA_GATEWAY, &fib6_nh->fib_nh_gw6))
                        goto nla_put_failure;
                break;
        }

        if (nhi->fib_nhc.nhc_lwtstate &&
            lwtunnel_fill_encap(skb, nhi->fib_nhc.nhc_lwtstate,
                                NHA_ENCAP, NHA_ENCAP_TYPE) < 0)
                goto nla_put_failure;

out:
        nlmsg_end(skb, nlh);
        return 0;

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

static size_t nh_nlmsg_size_grp_res(struct nh_group *nhg)
{
        return nla_total_size(0) +      /* NHA_RES_GROUP */
                nla_total_size(2) +     /* NHA_RES_GROUP_BUCKETS */
                nla_total_size(4) +     /* NHA_RES_GROUP_IDLE_TIMER */
                nla_total_size(4) +     /* NHA_RES_GROUP_UNBALANCED_TIMER */
                nla_total_size_64bit(8);/* NHA_RES_GROUP_UNBALANCED_TIME */
}

static size_t nh_nlmsg_size_grp(struct nexthop *nh)
{
        struct nh_group *nhg = rtnl_dereference(nh->nh_grp);
        size_t sz = sizeof(struct nexthop_grp) * nhg->num_nh;
        size_t tot = nla_total_size(sz) +
                nla_total_size(2); /* NHA_GROUP_TYPE */

        if (nhg->resilient)
                tot += nh_nlmsg_size_grp_res(nhg);

        return tot;
}

static size_t nh_nlmsg_size_single(struct nexthop *nh)
{
        struct nh_info *nhi = rtnl_dereference(nh->nh_info);
        size_t sz;

        /* covers NHA_BLACKHOLE since NHA_OIF and BLACKHOLE
         * are mutually exclusive
         */
        sz = nla_total_size(4);  /* NHA_OIF */

        switch (nhi->family) {
        case AF_INET:
                if (nhi->fib_nh.fib_nh_gw_family)
                        sz += nla_total_size(4);  /* NHA_GATEWAY */
                break;

        case AF_INET6:
                /* NHA_GATEWAY */
                if (nhi->fib6_nh.fib_nh_gw_family)
                        sz += nla_total_size(sizeof(const struct in6_addr));
                break;
        }

        if (nhi->fib_nhc.nhc_lwtstate) {
                sz += lwtunnel_get_encap_size(nhi->fib_nhc.nhc_lwtstate);
                sz += nla_total_size(2);  /* NHA_ENCAP_TYPE */
        }

        return sz;
}

static size_t nh_nlmsg_size(struct nexthop *nh)
{
        size_t sz = NLMSG_ALIGN(sizeof(struct nhmsg));

        sz += nla_total_size(4); /* NHA_ID */

        if (nh->is_group)
                sz += nh_nlmsg_size_grp(nh);
        else
                sz += nh_nlmsg_size_single(nh);

        return sz;
}

static void nexthop_notify(int event, struct nexthop *nh, struct nl_info *info)
{
        unsigned int nlflags = info->nlh ? info->nlh->nlmsg_flags : 0;
        u32 seq = info->nlh ? info->nlh->nlmsg_seq : 0;
        struct sk_buff *skb;
        int err = -ENOBUFS;

        skb = nlmsg_new(nh_nlmsg_size(nh), gfp_any());
        if (!skb)
                goto errout;

        err = nh_fill_node(skb, nh, event, info->portid, seq, nlflags);
        if (err < 0) {
                /* -EMSGSIZE implies BUG in nh_nlmsg_size() */
                WARN_ON(err == -EMSGSIZE);
                kfree_skb(skb);
                goto errout;
        }

        rtnl_notify(skb, info->nl_net, info->portid, RTNLGRP_NEXTHOP,
                    info->nlh, gfp_any());
        return;
errout:
        if (err < 0)
                rtnl_set_sk_err(info->nl_net, RTNLGRP_NEXTHOP, err);
}

static unsigned long nh_res_bucket_used_time(const struct nh_res_bucket *bucket)
{
        return (unsigned long)atomic_long_read(&bucket->used_time);
}

static unsigned long
nh_res_bucket_idle_point(const struct nh_res_table *res_table,
                         const struct nh_res_bucket *bucket,
                         unsigned long now)
{
        unsigned long time = nh_res_bucket_used_time(bucket);

        /* Bucket was not used since it was migrated. The idle time is now. */
        if (time == bucket->migrated_time)
                return now;

        return time + res_table->idle_timer;
}

static unsigned long
nh_res_table_unb_point(const struct nh_res_table *res_table)
{
        return res_table->unbalanced_since + res_table->unbalanced_timer;
}

static void nh_res_bucket_set_idle(const struct nh_res_table *res_table,
                                   struct nh_res_bucket *bucket)
{
        unsigned long now = jiffies;

        atomic_long_set(&bucket->used_time, (long)now);
        bucket->migrated_time = now;
}

static void nh_res_bucket_set_busy(struct nh_res_bucket *bucket)
{
        atomic_long_set(&bucket->used_time, (long)jiffies);
}

static clock_t nh_res_bucket_idle_time(const struct nh_res_bucket *bucket)
{
        unsigned long used_time = nh_res_bucket_used_time(bucket);

        return jiffies_delta_to_clock_t(jiffies - used_time);
}

static int nh_fill_res_bucket(struct sk_buff *skb, struct nexthop *nh,
                              struct nh_res_bucket *bucket, u16 bucket_index,
                              int event, u32 portid, u32 seq,
                              unsigned int nlflags,
                              struct netlink_ext_ack *extack)
{
        struct nh_grp_entry *nhge = nh_res_dereference(bucket->nh_entry);
        struct nlmsghdr *nlh;
        struct nlattr *nest;
        struct nhmsg *nhm;

        nlh = nlmsg_put(skb, portid, seq, event, sizeof(*nhm), nlflags);
        if (!nlh)
                return -EMSGSIZE;

        nhm = nlmsg_data(nlh);
        nhm->nh_family = AF_UNSPEC;
        nhm->nh_flags = bucket->nh_flags;
        nhm->nh_protocol = nh->protocol;
        nhm->nh_scope = 0;
        nhm->resvd = 0;

        if (nla_put_u32(skb, NHA_ID, nh->id))
                goto nla_put_failure;

        nest = nla_nest_start(skb, NHA_RES_BUCKET);
        if (!nest)
                goto nla_put_failure;

        if (nla_put_u16(skb, NHA_RES_BUCKET_INDEX, bucket_index) ||
            nla_put_u32(skb, NHA_RES_BUCKET_NH_ID, nhge->nh->id) ||
            nla_put_u64_64bit(skb, NHA_RES_BUCKET_IDLE_TIME,
                              nh_res_bucket_idle_time(bucket),
                              NHA_RES_BUCKET_PAD))
                goto nla_put_failure_nest;

        nla_nest_end(skb, nest);
        nlmsg_end(skb, nlh);
        return 0;

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

static void nexthop_bucket_notify(struct nh_res_table *res_table,
                                  u16 bucket_index)
{
        struct nh_res_bucket *bucket = &res_table->nh_buckets[bucket_index];
        struct nh_grp_entry *nhge = nh_res_dereference(bucket->nh_entry);
        struct nexthop *nh = nhge->nh_parent;
        struct sk_buff *skb;
        int err = -ENOBUFS;

        skb = alloc_skb(NLMSG_GOODSIZE, GFP_KERNEL);
        if (!skb)
                goto errout;

        err = nh_fill_res_bucket(skb, nh, bucket, bucket_index,
                                 RTM_NEWNEXTHOPBUCKET, 0, 0, NLM_F_REPLACE,
                                 NULL);
        if (err < 0) {
                kfree_skb(skb);
                goto errout;
        }

        rtnl_notify(skb, nh->net, 0, RTNLGRP_NEXTHOP, NULL, GFP_KERNEL);
        return;
errout:
        if (err < 0)
                rtnl_set_sk_err(nh->net, RTNLGRP_NEXTHOP, err);
}

static bool valid_group_nh(struct nexthop *nh, unsigned int npaths,
                           bool *is_fdb, struct netlink_ext_ack *extack)
{
        if (nh->is_group) {
                struct nh_group *nhg = rtnl_dereference(nh->nh_grp);

                /* Nesting groups within groups is not supported. */
                if (nhg->hash_threshold) {
                        NL_SET_ERR_MSG(extack,
                                       "Hash-threshold group can not be a nexthop within a group");
                        return false;
                }
                if (nhg->resilient) {

                        NL_SET_ERR_MSG(extack,
                                       "Resilient group can not be a nexthop within a group");
                        return false;
                }
                *is_fdb = nhg->fdb_nh;
        } else {
                struct nh_info *nhi = rtnl_dereference(nh->nh_info);

                if (nhi->reject_nh && npaths > 1) {
                        NL_SET_ERR_MSG(extack,
                                       "Blackhole nexthop can not be used in a group with more than 1 path");
                        return false;
                }
                *is_fdb = nhi->fdb_nh;
        }

        return true;
}

static int nh_check_attr_fdb_group(struct nexthop *nh, u8 *nh_family,
                                   struct netlink_ext_ack *extack)
{
        struct nh_info *nhi;

        nhi = rtnl_dereference(nh->nh_info);

        if (!nhi->fdb_nh) {
                NL_SET_ERR_MSG(extack, "FDB nexthop group can only have fdb nexthops");
                return -EINVAL;
        }

        if (*nh_family == AF_UNSPEC) {
                *nh_family = nhi->family;
        } else if (*nh_family != nhi->family) {
                NL_SET_ERR_MSG(extack, "FDB nexthop group cannot have mixed family nexthops");
                return -EINVAL;
        }

        return 0;
}

static int nh_check_attr_group(struct net *net,
                               struct nlattr *tb[], size_t tb_size,
                               u16 nh_grp_type, struct netlink_ext_ack *extack)
{
        unsigned int len = nla_len(tb[NHA_GROUP]);
        u8 nh_family = AF_UNSPEC;
        struct nexthop_grp *nhg;
        unsigned int i, j;
        u8 nhg_fdb = 0;

        if (!len || len & (sizeof(struct nexthop_grp) - 1)) {
                NL_SET_ERR_MSG(extack,
                               "Invalid length for nexthop group attribute");
                return -EINVAL;
        }

        /* convert len to number of nexthop ids */
        len /= sizeof(*nhg);

        nhg = nla_data(tb[NHA_GROUP]);
        for (i = 0; i < len; ++i) {
                if (nhg[i].resvd1 || nhg[i].resvd2) {
                        NL_SET_ERR_MSG(extack, "Reserved fields in nexthop_grp must be 0");
                        return -EINVAL;
                }
                if (nhg[i].weight > 254) {
                        NL_SET_ERR_MSG(extack, "Invalid value for weight");
                        return -EINVAL;
                }
                for (j = i + 1; j < len; ++j) {
                        if (nhg[i].id == nhg[j].id) {
                                NL_SET_ERR_MSG(extack, "Nexthop id can not be used twice in a group");
                                return -EINVAL;
                        }
                }
        }

        if (tb[NHA_FDB])
                nhg_fdb = 1;
        nhg = nla_data(tb[NHA_GROUP]);
        for (i = 0; i < len; ++i) {
                struct nexthop *nh;
                bool is_fdb_nh;

                nh = nexthop_find_by_id(net, nhg[i].id);
                if (!nh) {
                        NL_SET_ERR_MSG(extack, "Invalid nexthop id");
                        return -EINVAL;
                }
                if (!valid_group_nh(nh, len, &is_fdb_nh, extack))
                        return -EINVAL;

                if (nhg_fdb && nh_check_attr_fdb_group(nh, &nh_family, extack))
                        return -EINVAL;

                if (!nhg_fdb && is_fdb_nh) {
                        NL_SET_ERR_MSG(extack, "Non FDB nexthop group cannot have fdb nexthops");
                        return -EINVAL;
                }
        }
        for (i = NHA_GROUP_TYPE + 1; i < tb_size; ++i) {
                if (!tb[i])
                        continue;
                switch (i) {
                case NHA_FDB:
                        continue;
                case NHA_RES_GROUP:
                        if (nh_grp_type == NEXTHOP_GRP_TYPE_RES)
                                continue;
                        break;
                }
                NL_SET_ERR_MSG(extack,
                               "No other attributes can be set in nexthop groups");
                return -EINVAL;
        }

        return 0;
}

static bool ipv6_good_nh(const struct fib6_nh *nh)
{
        int state = NUD_REACHABLE;
        struct neighbour *n;

        rcu_read_lock_bh();

        n = __ipv6_neigh_lookup_noref_stub(nh->fib_nh_dev, &nh->fib_nh_gw6);
        if (n)
                state = n->nud_state;

        rcu_read_unlock_bh();

        return !!(state & NUD_VALID);
}

static bool ipv4_good_nh(const struct fib_nh *nh)
{
        int state = NUD_REACHABLE;
        struct neighbour *n;

        rcu_read_lock_bh();

        n = __ipv4_neigh_lookup_noref(nh->fib_nh_dev,
                                      (__force u32)nh->fib_nh_gw4);
        if (n)
                state = n->nud_state;

        rcu_read_unlock_bh();

        return !!(state & NUD_VALID);
}

static struct nexthop *nexthop_select_path_hthr(struct nh_group *nhg, int hash)
{
        struct nexthop *rc = NULL;
        int i;

        for (i = 0; i < nhg->num_nh; ++i) {
                struct nh_grp_entry *nhge = &nhg->nh_entries[i];
                struct nh_info *nhi;

                if (hash > atomic_read(&nhge->hthr.upper_bound))
                        continue;

                nhi = rcu_dereference(nhge->nh->nh_info);
                if (nhi->fdb_nh)
                        return nhge->nh;

                /* nexthops always check if it is good and does
                 * not rely on a sysctl for this behavior
                 */
                switch (nhi->family) {
                case AF_INET:
                        if (ipv4_good_nh(&nhi->fib_nh))
                                return nhge->nh;
                        break;
                case AF_INET6:
                        if (ipv6_good_nh(&nhi->fib6_nh))
                                return nhge->nh;
                        break;
                }

                if (!rc)
                        rc = nhge->nh;
        }

        return rc;
}

static struct nexthop *nexthop_select_path_res(struct nh_group *nhg, int hash)
{
        struct nh_res_table *res_table = rcu_dereference(nhg->res_table);
        u16 bucket_index = hash % res_table->num_nh_buckets;
        struct nh_res_bucket *bucket;
        struct nh_grp_entry *nhge;

        /* nexthop_select_path() is expected to return a non-NULL value, so
         * skip protocol validation and just hand out whatever there is.
         */
        bucket = &res_table->nh_buckets[bucket_index];
        nh_res_bucket_set_busy(bucket);
        nhge = rcu_dereference(bucket->nh_entry);
        return nhge->nh;
}

struct nexthop *nexthop_select_path(struct nexthop *nh, int hash)
{
        struct nh_group *nhg;

        if (!nh->is_group)
                return nh;

        nhg = rcu_dereference(nh->nh_grp);
        if (nhg->hash_threshold)
                return nexthop_select_path_hthr(nhg, hash);
        else if (nhg->resilient)
                return nexthop_select_path_res(nhg, hash);

        /* Unreachable. */
        return NULL;
}
EXPORT_SYMBOL_GPL(nexthop_select_path);

int nexthop_for_each_fib6_nh(struct nexthop *nh,
                             int (*cb)(struct fib6_nh *nh, void *arg),
                             void *arg)
{
        struct nh_info *nhi;
        int err;

        if (nh->is_group) {
                struct nh_group *nhg;
                int i;

                nhg = rcu_dereference_rtnl(nh->nh_grp);
                for (i = 0; i < nhg->num_nh; i++) {
                        struct nh_grp_entry *nhge = &nhg->nh_entries[i];

                        nhi = rcu_dereference_rtnl(nhge->nh->nh_info);
                        err = cb(&nhi->fib6_nh, arg);
                        if (err)
                                return err;
                }
        } else {
                nhi = rcu_dereference_rtnl(nh->nh_info);
                err = cb(&nhi->fib6_nh, arg);
                if (err)
                        return err;
        }

        return 0;
}
EXPORT_SYMBOL_GPL(nexthop_for_each_fib6_nh);

static int check_src_addr(const struct in6_addr *saddr,
                          struct netlink_ext_ack *extack)
{
        if (!ipv6_addr_any(saddr)) {
                NL_SET_ERR_MSG(extack, "IPv6 routes using source address can not use nexthop objects");
                return -EINVAL;
        }
        return 0;
}

int fib6_check_nexthop(struct nexthop *nh, struct fib6_config *cfg,
                       struct netlink_ext_ack *extack)
{
        struct nh_info *nhi;
        bool is_fdb_nh;

        /* fib6_src is unique to a fib6_info and limits the ability to cache
         * routes in fib6_nh within a nexthop that is potentially shared
         * across multiple fib entries. If the config wants to use source
         * routing it can not use nexthop objects. mlxsw also does not allow
         * fib6_src on routes.
         */
        if (cfg && check_src_addr(&cfg->fc_src, extack) < 0)
                return -EINVAL;

        if (nh->is_group) {
                struct nh_group *nhg;

                nhg = rtnl_dereference(nh->nh_grp);
                if (nhg->has_v4)
                        goto no_v4_nh;
                is_fdb_nh = nhg->fdb_nh;
        } else {
                nhi = rtnl_dereference(nh->nh_info);
                if (nhi->family == AF_INET)
                        goto no_v4_nh;
                is_fdb_nh = nhi->fdb_nh;
        }

        if (is_fdb_nh) {
                NL_SET_ERR_MSG(extack, "Route cannot point to a fdb nexthop");
                return -EINVAL;
        }

        return 0;
no_v4_nh:
        NL_SET_ERR_MSG(extack, "IPv6 routes can not use an IPv4 nexthop");
        return -EINVAL;
}
EXPORT_SYMBOL_GPL(fib6_check_nexthop);

/* if existing nexthop has ipv6 routes linked to it, need
 * to verify this new spec works with ipv6
 */
static int fib6_check_nh_list(struct nexthop *old, struct nexthop *new,
                              struct netlink_ext_ack *extack)
{
        struct fib6_info *f6i;

        if (list_empty(&old->f6i_list))
                return 0;

        list_for_each_entry(f6i, &old->f6i_list, nh_list) {
                if (check_src_addr(&f6i->fib6_src.addr, extack) < 0)
                        return -EINVAL;
        }

        return fib6_check_nexthop(new, NULL, extack);
}

static int nexthop_check_scope(struct nh_info *nhi, u8 scope,
                               struct netlink_ext_ack *extack)
{
        if (scope == RT_SCOPE_HOST && nhi->fib_nhc.nhc_gw_family) {
                NL_SET_ERR_MSG(extack,
                               "Route with host scope can not have a gateway");
                return -EINVAL;
        }

        if (nhi->fib_nhc.nhc_flags & RTNH_F_ONLINK && scope >= RT_SCOPE_LINK) {
                NL_SET_ERR_MSG(extack, "Scope mismatch with nexthop");
                return -EINVAL;
        }

        return 0;
}

/* Invoked by fib add code to verify nexthop by id is ok with
 * config for prefix; parts of fib_check_nh not done when nexthop
 * object is used.
 */
int fib_check_nexthop(struct nexthop *nh, u8 scope,
                      struct netlink_ext_ack *extack)
{
        struct nh_info *nhi;
        int err = 0;

        if (nh->is_group) {
                struct nh_group *nhg;

                nhg = rtnl_dereference(nh->nh_grp);
                if (nhg->fdb_nh) {
                        NL_SET_ERR_MSG(extack, "Route cannot point to a fdb nexthop");
                        err = -EINVAL;
                        goto out;
                }

                if (scope == RT_SCOPE_HOST) {
                        NL_SET_ERR_MSG(extack, "Route with host scope can not have multiple nexthops");
                        err = -EINVAL;
                        goto out;
                }

                /* all nexthops in a group have the same scope */
                nhi = rtnl_dereference(nhg->nh_entries[0].nh->nh_info);
                err = nexthop_check_scope(nhi, scope, extack);
        } else {
                nhi = rtnl_dereference(nh->nh_info);
                if (nhi->fdb_nh) {
                        NL_SET_ERR_MSG(extack, "Route cannot point to a fdb nexthop");
                        err = -EINVAL;
                        goto out;
                }
                err = nexthop_check_scope(nhi, scope, extack);
        }

out:
        return err;
}

static int fib_check_nh_list(struct nexthop *old, struct nexthop *new,
                             struct netlink_ext_ack *extack)
{
        struct fib_info *fi;

        list_for_each_entry(fi, &old->fi_list, nh_list) {
                int err;

                err = fib_check_nexthop(new, fi->fib_scope, extack);
                if (err)
                        return err;
        }
        return 0;
}

static bool nh_res_nhge_is_balanced(const struct nh_grp_entry *nhge)
{
        return nhge->res.count_buckets == nhge->res.wants_buckets;
}

static bool nh_res_nhge_is_ow(const struct nh_grp_entry *nhge)
{
        return nhge->res.count_buckets > nhge->res.wants_buckets;
}

static bool nh_res_nhge_is_uw(const struct nh_grp_entry *nhge)
{
        return nhge->res.count_buckets < nhge->res.wants_buckets;
}

static bool nh_res_table_is_balanced(const struct nh_res_table *res_table)
{
        return list_empty(&res_table->uw_nh_entries);
}

static void nh_res_bucket_unset_nh(struct nh_res_bucket *bucket)
{
        struct nh_grp_entry *nhge;

        if (bucket->occupied) {
                nhge = nh_res_dereference(bucket->nh_entry);
                nhge->res.count_buckets--;
                bucket->occupied = false;
        }
}

static void nh_res_bucket_set_nh(struct nh_res_bucket *bucket,
                                 struct nh_grp_entry *nhge)
{
        nh_res_bucket_unset_nh(bucket);

        bucket->occupied = true;
        rcu_assign_pointer(bucket->nh_entry, nhge);
        nhge->res.count_buckets++;
}

static bool nh_res_bucket_should_migrate(struct nh_res_table *res_table,
                                         struct nh_res_bucket *bucket,
                                         unsigned long *deadline, bool *force)
{
        unsigned long now = jiffies;
        struct nh_grp_entry *nhge;
        unsigned long idle_point;

        if (!bucket->occupied) {
                /* The bucket is not occupied, its NHGE pointer is either
                 * NULL or obsolete. We _have to_ migrate: set force.
                 */
                *force = true;
                return true;
        }

        nhge = nh_res_dereference(bucket->nh_entry);

        /* If the bucket is populated by an underweight or balanced
         * nexthop, do not migrate.
         */
        if (!nh_res_nhge_is_ow(nhge))
                return false;

        /* At this point we know that the bucket is populated with an
         * overweight nexthop. It needs to be migrated to a new nexthop if
         * the idle timer of unbalanced timer expired.
         */

        idle_point = nh_res_bucket_idle_point(res_table, bucket, now);
        if (time_after_eq(now, idle_point)) {
                /* The bucket is idle. We _can_ migrate: unset force. */
                *force = false;
                return true;
        }

        /* Unbalanced timer of 0 means "never force". */
        if (res_table->unbalanced_timer) {
                unsigned long unb_point;

                unb_point = nh_res_table_unb_point(res_table);
                if (time_after(now, unb_point)) {
                        /* The bucket is not idle, but the unbalanced timer
                         * expired. We _can_ migrate, but set force anyway,
                         * so that drivers know to ignore activity reports
                         * from the HW.
                         */
                        *force = true;
                        return true;
                }

                nh_res_time_set_deadline(unb_point, deadline);
        }

        nh_res_time_set_deadline(idle_point, deadline);
        return false;
}

static bool nh_res_bucket_migrate(struct nh_res_table *res_table,
                                  u16 bucket_index, bool notify,
                                  bool notify_nl, bool force)
{
        struct nh_res_bucket *bucket = &res_table->nh_buckets[bucket_index];
        struct nh_grp_entry *new_nhge;
        struct netlink_ext_ack extack;
        int err;

        new_nhge = list_first_entry_or_null(&res_table->uw_nh_entries,
                                            struct nh_grp_entry,
                                            res.uw_nh_entry);
        if (WARN_ON_ONCE(!new_nhge))
                /* If this function is called, "bucket" is either not
                 * occupied, or it belongs to a next hop that is
                 * overweight. In either case, there ought to be a
                 * corresponding underweight next hop.
                 */
                return false;

        if (notify) {
                struct nh_grp_entry *old_nhge;

                old_nhge = nh_res_dereference(bucket->nh_entry);
                err = call_nexthop_res_bucket_notifiers(res_table->net,
                                                        res_table->nhg_id,
                                                        bucket_index, force,
                                                        old_nhge->nh,
                                                        new_nhge->nh, &extack);
                if (err) {
                        pr_err_ratelimited("%s\n", extack._msg);
                        if (!force)
                                return false;
                        /* It is not possible to veto a forced replacement, so
                         * just clear the hardware flags from the nexthop
                         * bucket to indicate to user space that this bucket is
                         * not correctly populated in hardware.
                         */
                        bucket->nh_flags &= ~(RTNH_F_OFFLOAD | RTNH_F_TRAP);
                }
        }

        nh_res_bucket_set_nh(bucket, new_nhge);
        nh_res_bucket_set_idle(res_table, bucket);

        if (notify_nl)
                nexthop_bucket_notify(res_table, bucket_index);

        if (nh_res_nhge_is_balanced(new_nhge))
                list_del(&new_nhge->res.uw_nh_entry);
        return true;
}

#define NH_RES_UPKEEP_DW_MINIMUM_INTERVAL (HZ / 2)

static void nh_res_table_upkeep(struct nh_res_table *res_table,
                                bool notify, bool notify_nl)
{
        unsigned long now = jiffies;
        unsigned long deadline;
        u16 i;

        /* Deadline is the next time that upkeep should be run. It is the
         * earliest time at which one of the buckets might be migrated.
         * Start at the most pessimistic estimate: either unbalanced_timer
         * from now, or if there is none, idle_timer from now. For each
         * encountered time point, call nh_res_time_set_deadline() to
         * refine the estimate.
         */
        if (res_table->unbalanced_timer)
                deadline = now + res_table->unbalanced_timer;
        else
                deadline = now + res_table->idle_timer;

        for (i = 0; i < res_table->num_nh_buckets; i++) {
                struct nh_res_bucket *bucket = &res_table->nh_buckets[i];
                bool force;

                if (nh_res_bucket_should_migrate(res_table, bucket,
                                                 &deadline, &force)) {
                        if (!nh_res_bucket_migrate(res_table, i, notify,
                                                   notify_nl, force)) {
                                unsigned long idle_point;

                                /* A driver can override the migration
                                 * decision if the HW reports that the
                                 * bucket is actually not idle. Therefore
                                 * remark the bucket as busy again and
                                 * update the deadline.
                                 */
                                nh_res_bucket_set_busy(bucket);
                                idle_point = nh_res_bucket_idle_point(res_table,
                                                                      bucket,
                                                                      now);
                                nh_res_time_set_deadline(idle_point, &deadline);
                        }
                }
        }

        /* If the group is still unbalanced, schedule the next upkeep to
         * either the deadline computed above, or the minimum deadline,
         * whichever comes later.
         */
        if (!nh_res_table_is_balanced(res_table)) {
                unsigned long now = jiffies;
                unsigned long min_deadline;

                min_deadline = now + NH_RES_UPKEEP_DW_MINIMUM_INTERVAL;
                if (time_before(deadline, min_deadline))
                        deadline = min_deadline;

                queue_delayed_work(system_power_efficient_wq,
                                   &res_table->upkeep_dw, deadline - now);
        }
}

static void nh_res_table_upkeep_dw(struct work_struct *work)
{
        struct delayed_work *dw = to_delayed_work(work);
        struct nh_res_table *res_table;

        res_table = container_of(dw, struct nh_res_table, upkeep_dw);
        nh_res_table_upkeep(res_table, true, true);
}

static void nh_res_table_cancel_upkeep(struct nh_res_table *res_table)
{
        cancel_delayed_work_sync(&res_table->upkeep_dw);
}

static void nh_res_group_rebalance(struct nh_group *nhg,
                                   struct nh_res_table *res_table)
{
        int prev_upper_bound = 0;
        int total = 0;
        int w = 0;
        int i;

        INIT_LIST_HEAD(&res_table->uw_nh_entries);

        for (i = 0; i < nhg->num_nh; ++i)
                total += nhg->nh_entries[i].weight;

        for (i = 0; i < nhg->num_nh; ++i) {
                struct nh_grp_entry *nhge = &nhg->nh_entries[i];
                int upper_bound;

                w += nhge->weight;
                upper_bound = DIV_ROUND_CLOSEST(res_table->num_nh_buckets * w,
                                                total);
                nhge->res.wants_buckets = upper_bound - prev_upper_bound;
                prev_upper_bound = upper_bound;

                if (nh_res_nhge_is_uw(nhge)) {
                        if (list_empty(&res_table->uw_nh_entries))
                                res_table->unbalanced_since = jiffies;
                        list_add(&nhge->res.uw_nh_entry,
                                 &res_table->uw_nh_entries);
                }
        }
}

/* Migrate buckets in res_table so that they reference NHGE's from NHG with
 * the right NH ID. Set those buckets that do not have a corresponding NHGE
 * entry in NHG as not occupied.
 */
static void nh_res_table_migrate_buckets(struct nh_res_table *res_table,
                                         struct nh_group *nhg)
{
        u16 i;

        for (i = 0; i < res_table->num_nh_buckets; i++) {
                struct nh_res_bucket *bucket = &res_table->nh_buckets[i];
                u32 id = rtnl_dereference(bucket->nh_entry)->nh->id;
                bool found = false;
                int j;

                for (j = 0; j < nhg->num_nh; j++) {
                        struct nh_grp_entry *nhge = &nhg->nh_entries[j];

                        if (nhge->nh->id == id) {
                                nh_res_bucket_set_nh(bucket, nhge);
                                found = true;
                                break;
                        }
                }

                if (!found)
                        nh_res_bucket_unset_nh(bucket);
        }
}

static void replace_nexthop_grp_res(struct nh_group *oldg,
                                    struct nh_group *newg)
{
        /* For NH group replacement, the new NHG might only have a stub
         * hash table with 0 buckets, because the number of buckets was not
         * specified. For NH removal, oldg and newg both reference the same
         * res_table. So in any case, in the following, we want to work
         * with oldg->res_table.
         */
        struct nh_res_table *old_res_table = rtnl_dereference(oldg->res_table);
        unsigned long prev_unbalanced_since = old_res_table->unbalanced_since;
        bool prev_has_uw = !list_empty(&old_res_table->uw_nh_entries);

        nh_res_table_cancel_upkeep(old_res_table);
        nh_res_table_migrate_buckets(old_res_table, newg);
        nh_res_group_rebalance(newg, old_res_table);
        if (prev_has_uw && !list_empty(&old_res_table->uw_nh_entries))
                old_res_table->unbalanced_since = prev_unbalanced_since;
        nh_res_table_upkeep(old_res_table, true, false);
}

static void nh_hthr_group_rebalance(struct nh_group *nhg)
{
        int total = 0;
        int w = 0;
        int i;

        for (i = 0; i < nhg->num_nh; ++i)
                total += nhg->nh_entries[i].weight;

        for (i = 0; i < nhg->num_nh; ++i) {
                struct nh_grp_entry *nhge = &nhg->nh_entries[i];
                int upper_bound;

                w += nhge->weight;
                upper_bound = DIV_ROUND_CLOSEST_ULL((u64)w << 31, total) - 1;
                atomic_set(&nhge->hthr.upper_bound, upper_bound);
        }
}

static void remove_nh_grp_entry(struct net *net, struct nh_grp_entry *nhge,
                                struct nl_info *nlinfo)
{
        struct nh_grp_entry *nhges, *new_nhges;
        struct nexthop *nhp = nhge->nh_parent;
        struct netlink_ext_ack extack;
        struct nexthop *nh = nhge->nh;
        struct nh_group *nhg, *newg;
        int i, j, err;

        WARN_ON(!nh);

        nhg = rtnl_dereference(nhp->nh_grp);
        newg = nhg->spare;

        /* last entry, keep it visible and remove the parent */
        if (nhg->num_nh == 1) {
                remove_nexthop(net, nhp, nlinfo);
                return;
        }

        newg->has_v4 = false;
        newg->is_multipath = nhg->is_multipath;
        newg->hash_threshold = nhg->hash_threshold;
        newg->resilient = nhg->resilient;
        newg->fdb_nh = nhg->fdb_nh;
        newg->num_nh = nhg->num_nh;

        /* copy old entries to new except the one getting removed */
        nhges = nhg->nh_entries;
        new_nhges = newg->nh_entries;
        for (i = 0, j = 0; i < nhg->num_nh; ++i) {
                struct nh_info *nhi;

                /* current nexthop getting removed */
                if (nhg->nh_entries[i].nh == nh) {
                        newg->num_nh--;
                        continue;
                }

                nhi = rtnl_dereference(nhges[i].nh->nh_info);
                if (nhi->family == AF_INET)
                        newg->has_v4 = true;

                list_del(&nhges[i].nh_list);
                new_nhges[j].nh_parent = nhges[i].nh_parent;
                new_nhges[j].nh = nhges[i].nh;
                new_nhges[j].weight = nhges[i].weight;
                list_add(&new_nhges[j].nh_list, &new_nhges[j].nh->grp_list);
                j++;
        }

        if (newg->hash_threshold)
                nh_hthr_group_rebalance(newg);
        else if (newg->resilient)
                replace_nexthop_grp_res(nhg, newg);

        rcu_assign_pointer(nhp->nh_grp, newg);

        list_del(&nhge->nh_list);
        nexthop_put(nhge->nh);

        /* Removal of a NH from a resilient group is notified through
         * bucket notifications.
         */
        if (newg->hash_threshold) {
                err = call_nexthop_notifiers(net, NEXTHOP_EVENT_REPLACE, nhp,
                                             &extack);
                if (err)
                        pr_err("%s\n", extack._msg);
        }

        if (nlinfo)
                nexthop_notify(RTM_NEWNEXTHOP, nhp, nlinfo);
}

static void remove_nexthop_from_groups(struct net *net, struct nexthop *nh,
                                       struct nl_info *nlinfo)
{
        struct nh_grp_entry *nhge, *tmp;

        list_for_each_entry_safe(nhge, tmp, &nh->grp_list, nh_list)
                remove_nh_grp_entry(net, nhge, nlinfo);

        /* make sure all see the newly published array before releasing rtnl */
        synchronize_net();
}

static void remove_nexthop_group(struct nexthop *nh, struct nl_info *nlinfo)
{
        struct nh_group *nhg = rcu_dereference_rtnl(nh->nh_grp);
        struct nh_res_table *res_table;
        int i, num_nh = nhg->num_nh;

        for (i = 0; i < num_nh; ++i) {
                struct nh_grp_entry *nhge = &nhg->nh_entries[i];

                if (WARN_ON(!nhge->nh))
                        continue;

                list_del_init(&nhge->nh_list);
        }

        if (nhg->resilient) {
                res_table = rtnl_dereference(nhg->res_table);
                nh_res_table_cancel_upkeep(res_table);
        }
}

/* not called for nexthop replace */
static void __remove_nexthop_fib(struct net *net, struct nexthop *nh)
{
        struct fib6_info *f6i, *tmp;
        bool do_flush = false;
        struct fib_info *fi;

        list_for_each_entry(fi, &nh->fi_list, nh_list) {
                fi->fib_flags |= RTNH_F_DEAD;
                do_flush = true;
        }
        if (do_flush)
                fib_flush(net);

        /* ip6_del_rt removes the entry from this list hence the _safe */
        list_for_each_entry_safe(f6i, tmp, &nh->f6i_list, nh_list) {
                /* __ip6_del_rt does a release, so do a hold here */
                fib6_info_hold(f6i);
                ipv6_stub->ip6_del_rt(net, f6i,
                                      !net->ipv4.sysctl_nexthop_compat_mode);
        }
}

static void __remove_nexthop(struct net *net, struct nexthop *nh,
                             struct nl_info *nlinfo)
{
        __remove_nexthop_fib(net, nh);

        if (nh->is_group) {
                remove_nexthop_group(nh, nlinfo);
        } else {
                struct nh_info *nhi;

                nhi = rtnl_dereference(nh->nh_info);
                if (nhi->fib_nhc.nhc_dev)
                        hlist_del(&nhi->dev_hash);

                remove_nexthop_from_groups(net, nh, nlinfo);
        }
}

static void remove_nexthop(struct net *net, struct nexthop *nh,
                           struct nl_info *nlinfo)
{
        call_nexthop_notifiers(net, NEXTHOP_EVENT_DEL, nh, NULL);

        /* remove from the tree */
        rb_erase(&nh->rb_node, &net->nexthop.rb_root);

        if (nlinfo)
                nexthop_notify(RTM_DELNEXTHOP, nh, nlinfo);

        __remove_nexthop(net, nh, nlinfo);
        nh_base_seq_inc(net);

        nexthop_put(nh);
}

/* if any FIB entries reference this nexthop, any dst entries
 * need to be regenerated
 */
static void nh_rt_cache_flush(struct net *net, struct nexthop *nh)
{
        struct fib6_info *f6i;

        if (!list_empty(&nh->fi_list))
                rt_cache_flush(net);

        list_for_each_entry(f6i, &nh->f6i_list, nh_list)
                ipv6_stub->fib6_update_sernum(net, f6i);
}

static int replace_nexthop_grp(struct net *net, struct nexthop *old,
                               struct nexthop *new, const struct nh_config *cfg,
                               struct netlink_ext_ack *extack)
{
        struct nh_res_table *tmp_table = NULL;
        struct nh_res_table *new_res_table;
        struct nh_res_table *old_res_table;
        struct nh_group *oldg, *newg;
        int i, err;

        if (!new->is_group) {
                NL_SET_ERR_MSG(extack, "Can not replace a nexthop group with a nexthop.");
                return -EINVAL;
        }

        oldg = rtnl_dereference(old->nh_grp);
        newg = rtnl_dereference(new->nh_grp);

        if (newg->hash_threshold != oldg->hash_threshold) {
                NL_SET_ERR_MSG(extack, "Can not replace a nexthop group with one of a different type.");
                return -EINVAL;
        }

        if (newg->hash_threshold) {
                err = call_nexthop_notifiers(net, NEXTHOP_EVENT_REPLACE, new,
                                             extack);
                if (err)
                        return err;
        } else if (newg->resilient) {
                new_res_table = rtnl_dereference(newg->res_table);
                old_res_table = rtnl_dereference(oldg->res_table);

                /* Accept if num_nh_buckets was not given, but if it was
                 * given, demand that the value be correct.
                 */
                if (cfg->nh_grp_res_has_num_buckets &&
                    cfg->nh_grp_res_num_buckets !=
                    old_res_table->num_nh_buckets) {
                        NL_SET_ERR_MSG(extack, "Can not change number of buckets of a resilient nexthop group.");
                        return -EINVAL;
                }

                /* Emit a pre-replace notification so that listeners could veto
                 * a potentially unsupported configuration. Otherwise,
                 * individual bucket replacement notifications would need to be
                 * vetoed, which is something that should only happen if the
                 * bucket is currently active.
                 */
                err = call_nexthop_res_table_notifiers(net, new, extack);
                if (err)
                        return err;

                if (cfg->nh_grp_res_has_idle_timer)
                        old_res_table->idle_timer = cfg->nh_grp_res_idle_timer;
                if (cfg->nh_grp_res_has_unbalanced_timer)
                        old_res_table->unbalanced_timer =
                                cfg->nh_grp_res_unbalanced_timer;

                replace_nexthop_grp_res(oldg, newg);

                tmp_table = new_res_table;
                rcu_assign_pointer(newg->res_table, old_res_table);
                rcu_assign_pointer(newg->spare->res_table, old_res_table);
        }

        /* update parents - used by nexthop code for cleanup */
        for (i = 0; i < newg->num_nh; i++)
                newg->nh_entries[i].nh_parent = old;

        rcu_assign_pointer(old->nh_grp, newg);

        if (newg->resilient) {
                rcu_assign_pointer(oldg->res_table, tmp_table);
                rcu_assign_pointer(oldg->spare->res_table, tmp_table);
        }

        for (i = 0; i < oldg->num_nh; i++)
                oldg->nh_entries[i].nh_parent = new;

        rcu_assign_pointer(new->nh_grp, oldg);

        return 0;
}

static void nh_group_v4_update(struct nh_group *nhg)
{
        struct nh_grp_entry *nhges;
        bool has_v4 = false;

        int i;

        nhges = nhg->nh_entries;
        for (i = 0; i < nhg->num_nh; i++) {
                struct nh_info *nhi;

                nhi = rtnl_dereference(nhges[i].nh->nh_info);
                if (nhi->family == AF_INET)
                        has_v4 = true;
        }
        nhg->has_v4 = has_v4;
}

static int replace_nexthop_single_notify_res(struct net *net,
                                             struct nh_res_table *res_table,
                                             struct nexthop *old,
                                             struct nh_info *oldi,
                                             struct nh_info *newi,
                                             struct netlink_ext_ack *extack)
{
        u32 nhg_id = res_table->nhg_id;
        int err;
        u16 i;

        for (i = 0; i < res_table->num_nh_buckets; i++) {
                struct nh_res_bucket *bucket = &res_table->nh_buckets[i];
                struct nh_grp_entry *nhge;

                nhge = rtnl_dereference(bucket->nh_entry);
                if (nhge->nh == old) {
                        err = __call_nexthop_res_bucket_notifiers(net, nhg_id,
                                                                  i, true,
                                                                  oldi, newi,
                                                                  extack);
                        if (err)
                                goto err_notify;
                }
        }

        return 0;

err_notify:
        while (i-- > 0) {
                struct nh_res_bucket *bucket = &res_table->nh_buckets[i];
                struct nh_grp_entry *nhge;

                nhge = rtnl_dereference(bucket->nh_entry);
                if (nhge->nh == old)
                        __call_nexthop_res_bucket_notifiers(net, nhg_id, i,
                                                            true, newi, oldi,
                                                            extack);
        }
        return err;
}

static int replace_nexthop_single_notify(struct net *net,
                                         struct nexthop *group_nh,
                                         struct nexthop *old,
                                         struct nh_info *oldi,
                                         struct nh_info *newi,
                                         struct netlink_ext_ack *extack)
{
        struct nh_group *nhg = rtnl_dereference(group_nh->nh_grp);
        struct nh_res_table *res_table;

        if (nhg->hash_threshold) {
                return call_nexthop_notifiers(net, NEXTHOP_EVENT_REPLACE,
                                              group_nh, extack);
        } else if (nhg->resilient) {
                res_table = rtnl_dereference(nhg->res_table);
                return replace_nexthop_single_notify_res(net, res_table,
                                                         old, oldi, newi,
                                                         extack);
        }

        return -EINVAL;
}

static int replace_nexthop_single(struct net *net, struct nexthop *old,
                                  struct nexthop *new,
                                  struct netlink_ext_ack *extack)
{
        u8 old_protocol, old_nh_flags;
        struct nh_info *oldi, *newi;
        struct nh_grp_entry *nhge;
        int err;

        if (new->is_group) {
                NL_SET_ERR_MSG(extack, "Can not replace a nexthop with a nexthop group.");
                return -EINVAL;
        }

        err = call_nexthop_notifiers(net, NEXTHOP_EVENT_REPLACE, new, extack);
        if (err)
                return err;

        /* Hardware flags were set on 'old' as 'new' is not in the red-black
         * tree. Therefore, inherit the flags from 'old' to 'new'.
         */
        new->nh_flags |= old->nh_flags & (RTNH_F_OFFLOAD | RTNH_F_TRAP);

        oldi = rtnl_dereference(old->nh_info);
        newi = rtnl_dereference(new->nh_info);

        newi->nh_parent = old;
        oldi->nh_parent = new;

        old_protocol = old->protocol;
        old_nh_flags = old->nh_flags;

        old->protocol = new->protocol;
        old->nh_flags = new->nh_flags;

        rcu_assign_pointer(old->nh_info, newi);
        rcu_assign_pointer(new->nh_info, oldi);

        /* Send a replace notification for all the groups using the nexthop. */
        list_for_each_entry(nhge, &old->grp_list, nh_list) {
                struct nexthop *nhp = nhge->nh_parent;

                err = replace_nexthop_single_notify(net, nhp, old, oldi, newi,
                                                    extack);
                if (err)
                        goto err_notify;
        }

        /* When replacing an IPv4 nexthop with an IPv6 nexthop, potentially
         * update IPv4 indication in all the groups using the nexthop.
         */
        if (oldi->family == AF_INET && newi->family == AF_INET6) {
                list_for_each_entry(nhge, &old->grp_list, nh_list) {
                        struct nexthop *nhp = nhge->nh_parent;
                        struct nh_group *nhg;

                        nhg = rtnl_dereference(nhp->nh_grp);
                        nh_group_v4_update(nhg);
                }
        }

        return 0;

err_notify:
        rcu_assign_pointer(new->nh_info, newi);
        rcu_assign_pointer(old->nh_info, oldi);
        old->nh_flags = old_nh_flags;
        old->protocol = old_protocol;
        oldi->nh_parent = old;
        newi->nh_parent = new;
        list_for_each_entry_continue_reverse(nhge, &old->grp_list, nh_list) {
                struct nexthop *nhp = nhge->nh_parent;

                replace_nexthop_single_notify(net, nhp, old, newi, oldi, NULL);
        }
        call_nexthop_notifiers(net, NEXTHOP_EVENT_REPLACE, old, extack);
        return err;
}

static void __nexthop_replace_notify(struct net *net, struct nexthop *nh,
                                     struct nl_info *info)
{
        struct fib6_info *f6i;

        if (!list_empty(&nh->fi_list)) {
                struct fib_info *fi;

                /* expectation is a few fib_info per nexthop and then
                 * a lot of routes per fib_info. So mark the fib_info
                 * and then walk the fib tables once
                 */
                list_for_each_entry(fi, &nh->fi_list, nh_list)
                        fi->nh_updated = true;

                fib_info_notify_update(net, info);

                list_for_each_entry(fi, &nh->fi_list, nh_list)
                        fi->nh_updated = false;
        }

        list_for_each_entry(f6i, &nh->f6i_list, nh_list)
                ipv6_stub->fib6_rt_update(net, f6i, info);
}

/* send RTM_NEWROUTE with REPLACE flag set for all FIB entries
 * linked to this nexthop and for all groups that the nexthop
 * is a member of
 */
static void nexthop_replace_notify(struct net *net, struct nexthop *nh,
                                   struct nl_info *info)
{
        struct nh_grp_entry *nhge;

        __nexthop_replace_notify(net, nh, info);

        list_for_each_entry(nhge, &nh->grp_list, nh_list)
                __nexthop_replace_notify(net, nhge->nh_parent, info);
}

static int replace_nexthop(struct net *net, struct nexthop *old,
                           struct nexthop *new, const struct nh_config *cfg,
                           struct netlink_ext_ack *extack)
{
        bool new_is_reject = false;
        struct nh_grp_entry *nhge;
        int err;

        /* check that existing FIB entries are ok with the
         * new nexthop definition
         */
        err = fib_check_nh_list(old, new, extack);
        if (err)
                return err;

        err = fib6_check_nh_list(old, new, extack);
        if (err)
                return err;

        if (!new->is_group) {
                struct nh_info *nhi = rtnl_dereference(new->nh_info);

                new_is_reject = nhi->reject_nh;
        }

        list_for_each_entry(nhge, &old->grp_list, nh_list) {
                /* if new nexthop is a blackhole, any groups using this
                 * nexthop cannot have more than 1 path
                 */
                if (new_is_reject &&
                    nexthop_num_path(nhge->nh_parent) > 1) {
                        NL_SET_ERR_MSG(extack, "Blackhole nexthop can not be a member of a group with more than one path");
                        return -EINVAL;
                }

                err = fib_check_nh_list(nhge->nh_parent, new, extack);
                if (err)
                        return err;

                err = fib6_check_nh_list(nhge->nh_parent, new, extack);
                if (err)
                        return err;
        }

        if (old->is_group)
                err = replace_nexthop_grp(net, old, new, cfg, extack);
        else
                err = replace_nexthop_single(net, old, new, extack);

        if (!err) {
                nh_rt_cache_flush(net, old);

                __remove_nexthop(net, new, NULL);
                nexthop_put(new);
        }

        return err;
}

/* called with rtnl_lock held */
static int insert_nexthop(struct net *net, struct nexthop *new_nh,
                          struct nh_config *cfg, struct netlink_ext_ack *extack)
{
        struct rb_node **pp, *parent = NULL, *next;
        struct rb_root *root = &net->nexthop.rb_root;
        bool replace = !!(cfg->nlflags & NLM_F_REPLACE);
        bool create = !!(cfg->nlflags & NLM_F_CREATE);
        u32 new_id = new_nh->id;
        int replace_notify = 0;
        int rc = -EEXIST;

        pp = &root->rb_node;
        while (1) {
                struct nexthop *nh;

                next = *pp;
                if (!next)
                        break;

                parent = next;

                nh = rb_entry(parent, struct nexthop, rb_node);
                if (new_id < nh->id) {
                        pp = &next->rb_left;
                } else if (new_id > nh->id) {
                        pp = &next->rb_right;
                } else if (replace) {
                        rc = replace_nexthop(net, nh, new_nh, cfg, extack);
                        if (!rc) {
                                new_nh = nh; /* send notification with old nh */
                                replace_notify = 1;
                        }
                        goto out;
                } else {
                        /* id already exists and not a replace */
                        goto out;
                }
        }

        if (replace && !create) {
                NL_SET_ERR_MSG(extack, "Replace specified without create and no entry exists");
                rc = -ENOENT;
                goto out;
        }

        if (new_nh->is_group) {
                struct nh_group *nhg = rtnl_dereference(new_nh->nh_grp);
                struct nh_res_table *res_table;

                if (nhg->resilient) {
                        res_table = rtnl_dereference(nhg->res_table);

                        /* Not passing the number of buckets is OK when
                         * replacing, but not when creating a new group.
                         */
                        if (!cfg->nh_grp_res_has_num_buckets) {
                                NL_SET_ERR_MSG(extack, "Number of buckets not specified for nexthop group insertion");
                                rc = -EINVAL;
                                goto out;
                        }

                        nh_res_group_rebalance(nhg, res_table);

                        /* Do not send bucket notifications, we do full
                         * notification below.
                         */
                        nh_res_table_upkeep(res_table, false, false);
                }
        }

        rb_link_node_rcu(&new_nh->rb_node, parent, pp);
        rb_insert_color(&new_nh->rb_node, root);

        /* The initial insertion is a full notification for hash-threshold as
         * well as resilient groups.
         */
        rc = call_nexthop_notifiers(net, NEXTHOP_EVENT_REPLACE, new_nh, extack);
        if (rc)
                rb_erase(&new_nh->rb_node, &net->nexthop.rb_root);

out:
        if (!rc) {
                nh_base_seq_inc(net);
                nexthop_notify(RTM_NEWNEXTHOP, new_nh, &cfg->nlinfo);
                if (replace_notify && net->ipv4.sysctl_nexthop_compat_mode)
                        nexthop_replace_notify(net, new_nh, &cfg->nlinfo);
        }

        return rc;
}

/* rtnl */
/* remove all nexthops tied to a device being deleted */
static void nexthop_flush_dev(struct net_device *dev, unsigned long event)
{
        unsigned int hash = nh_dev_hashfn(dev->ifindex);
        struct net *net = dev_net(dev);
        struct hlist_head *head = &net->nexthop.devhash[hash];
        struct hlist_node *n;
        struct nh_info *nhi;

        hlist_for_each_entry_safe(nhi, n, head, dev_hash) {
                if (nhi->fib_nhc.nhc_dev != dev)
                        continue;

                if (nhi->reject_nh &&
                    (event == NETDEV_DOWN || event == NETDEV_CHANGE))
                        continue;

                remove_nexthop(net, nhi->nh_parent, NULL);
        }
}

/* rtnl; called when net namespace is deleted */
static void flush_all_nexthops(struct net *net)
{
        struct rb_root *root = &net->nexthop.rb_root;
        struct rb_node *node;
        struct nexthop *nh;

        while ((node = rb_first(root))) {
                nh = rb_entry(node, struct nexthop, rb_node);
                remove_nexthop(net, nh, NULL);
                cond_resched();
        }
}

static struct nexthop *nexthop_create_group(struct net *net,
                                            struct nh_config *cfg)
{
        struct nlattr *grps_attr = cfg->nh_grp;
        struct nexthop_grp *entry = nla_data(grps_attr);
        u16 num_nh = nla_len(grps_attr) / sizeof(*entry);
        struct nh_group *nhg;
        struct nexthop *nh;
        int err;
        int i;

        if (WARN_ON(!num_nh))
                return ERR_PTR(-EINVAL);

        nh = nexthop_alloc();
        if (!nh)
                return ERR_PTR(-ENOMEM);

        nh->is_group = 1;

        nhg = nexthop_grp_alloc(num_nh);
        if (!nhg) {
                kfree(nh);
                return ERR_PTR(-ENOMEM);
        }

        /* spare group used for removals */
        nhg->spare = nexthop_grp_alloc(num_nh);
        if (!nhg->spare) {
                kfree(nhg);
                kfree(nh);
                return ERR_PTR(-ENOMEM);
        }
        nhg->spare->spare = nhg;

        for (i = 0; i < nhg->num_nh; ++i) {
                struct nexthop *nhe;
                struct nh_info *nhi;

                nhe = nexthop_find_by_id(net, entry[i].id);
                if (!nexthop_get(nhe)) {
                        err = -ENOENT;
                        goto out_no_nh;
                }

                nhi = rtnl_dereference(nhe->nh_info);
                if (nhi->family == AF_INET)
                        nhg->has_v4 = true;

                nhg->nh_entries[i].nh = nhe;
                nhg->nh_entries[i].weight = entry[i].weight + 1;
                list_add(&nhg->nh_entries[i].nh_list, &nhe->grp_list);
                nhg->nh_entries[i].nh_parent = nh;
        }

        if (cfg->nh_grp_type == NEXTHOP_GRP_TYPE_MPATH) {
                nhg->hash_threshold = 1;
                nhg->is_multipath = true;
        } else if (cfg->nh_grp_type == NEXTHOP_GRP_TYPE_RES) {
                struct nh_res_table *res_table;

                res_table = nexthop_res_table_alloc(net, cfg->nh_id, cfg);
                if (!res_table) {
                        err = -ENOMEM;
                        goto out_no_nh;
                }

                rcu_assign_pointer(nhg->spare->res_table, res_table);
                rcu_assign_pointer(nhg->res_table, res_table);
                nhg->resilient = true;
                nhg->is_multipath = true;
        }

        WARN_ON_ONCE(nhg->hash_threshold + nhg->resilient != 1);

        if (nhg->hash_threshold)
                nh_hthr_group_rebalance(nhg);

        if (cfg->nh_fdb)
                nhg->fdb_nh = 1;

        rcu_assign_pointer(nh->nh_grp, nhg);

        return nh;

out_no_nh:
        for (i--; i >= 0; --i) {
                list_del(&nhg->nh_entries[i].nh_list);
                nexthop_put(nhg->nh_entries[i].nh);
        }

        kfree(nhg->spare);
        kfree(nhg);
        kfree(nh);

        return ERR_PTR(err);
}

static int nh_create_ipv4(struct net *net, struct nexthop *nh,
                          struct nh_info *nhi, struct nh_config *cfg,
                          struct netlink_ext_ack *extack)
{
        struct fib_nh *fib_nh = &nhi->fib_nh;
        struct fib_config fib_cfg = {
                .fc_oif   = cfg->nh_ifindex,
                .fc_gw4   = cfg->gw.ipv4,
                .fc_gw_family = cfg->gw.ipv4 ? AF_INET : 0,
                .fc_flags = cfg->nh_flags,
                .fc_encap = cfg->nh_encap,
                .fc_encap_type = cfg->nh_encap_type,
        };
        u32 tb_id = (cfg->dev ? l3mdev_fib_table(cfg->dev) : RT_TABLE_MAIN);
        int err;

        err = fib_nh_init(net, fib_nh, &fib_cfg, 1, extack);
        if (err) {
                fib_nh_release(net, fib_nh);
                goto out;
        }

        if (nhi->fdb_nh)
                goto out;

        /* sets nh_dev if successful */
        err = fib_check_nh(net, fib_nh, tb_id, 0, extack);
        if (!err) {
                nh->nh_flags = fib_nh->fib_nh_flags;
                fib_info_update_nhc_saddr(net, &fib_nh->nh_common,
                                          fib_nh->fib_nh_scope);
        } else {
                fib_nh_release(net, fib_nh);
        }
out:
        return err;
}

static int nh_create_ipv6(struct net *net,  struct nexthop *nh,
                          struct nh_info *nhi, struct nh_config *cfg,
                          struct netlink_ext_ack *extack)
{
        struct fib6_nh *fib6_nh = &nhi->fib6_nh;
        struct fib6_config fib6_cfg = {
                .fc_table = l3mdev_fib_table(cfg->dev),
                .fc_ifindex = cfg->nh_ifindex,
                .fc_gateway = cfg->gw.ipv6,
                .fc_flags = cfg->nh_flags,
                .fc_encap = cfg->nh_encap,
                .fc_encap_type = cfg->nh_encap_type,
                .fc_is_fdb = cfg->nh_fdb,
        };
        int err;

        if (!ipv6_addr_any(&cfg->gw.ipv6))
                fib6_cfg.fc_flags |= RTF_GATEWAY;

        /* sets nh_dev if successful */
        err = ipv6_stub->fib6_nh_init(net, fib6_nh, &fib6_cfg, GFP_KERNEL,
                                      extack);
        if (err)
                ipv6_stub->fib6_nh_release(fib6_nh);
        else
                nh->nh_flags = fib6_nh->fib_nh_flags;

        return err;
}

static struct nexthop *nexthop_create(struct net *net, struct nh_config *cfg,
                                      struct netlink_ext_ack *extack)
{
        struct nh_info *nhi;
        struct nexthop *nh;
        int err = 0;

        nh = nexthop_alloc();
        if (!nh)
                return ERR_PTR(-ENOMEM);

        nhi = kzalloc(sizeof(*nhi), GFP_KERNEL);
        if (!nhi) {
                kfree(nh);
                return ERR_PTR(-ENOMEM);
        }

        nh->nh_flags = cfg->nh_flags;
        nh->net = net;

        nhi->nh_parent = nh;
        nhi->family = cfg->nh_family;
        nhi->fib_nhc.nhc_scope = RT_SCOPE_LINK;

        if (cfg->nh_fdb)
                nhi->fdb_nh = 1;

        if (cfg->nh_blackhole) {
                nhi->reject_nh = 1;
                cfg->nh_ifindex = net->loopback_dev->ifindex;
        }

        switch (cfg->nh_family) {
        case AF_INET:
                err = nh_create_ipv4(net, nh, nhi, cfg, extack);
                break;
        case AF_INET6:
                err = nh_create_ipv6(net, nh, nhi, cfg, extack);
                break;
        }

        if (err) {
                kfree(nhi);
                kfree(nh);
                return ERR_PTR(err);
        }

        /* add the entry to the device based hash */
        if (!nhi->fdb_nh)
                nexthop_devhash_add(net, nhi);

        rcu_assign_pointer(nh->nh_info, nhi);

        return nh;
}

/* called with rtnl lock held */
static struct nexthop *nexthop_add(struct net *net, struct nh_config *cfg,
                                   struct netlink_ext_ack *extack)
{
        struct nexthop *nh;
        int err;

        if (cfg->nlflags & NLM_F_REPLACE && !cfg->nh_id) {
                NL_SET_ERR_MSG(extack, "Replace requires nexthop id");
                return ERR_PTR(-EINVAL);
        }

        if (!cfg->nh_id) {
                cfg->nh_id = nh_find_unused_id(net);
                if (!cfg->nh_id) {
                        NL_SET_ERR_MSG(extack, "No unused id");
                        return ERR_PTR(-EINVAL);
                }
        }

        if (cfg->nh_grp)
                nh = nexthop_create_group(net, cfg);
        else
                nh = nexthop_create(net, cfg, extack);

        if (IS_ERR(nh))
                return nh;

        refcount_set(&nh->refcnt, 1);
        nh->id = cfg->nh_id;
        nh->protocol = cfg->nh_protocol;
        nh->net = net;

        err = insert_nexthop(net, nh, cfg, extack);
        if (err) {
                __remove_nexthop(net, nh, NULL);
                nexthop_put(nh);
                nh = ERR_PTR(err);
        }

        return nh;
}

static int rtm_nh_get_timer(struct nlattr *attr, unsigned long fallback,
                            unsigned long *timer_p, bool *has_p,
                            struct netlink_ext_ack *extack)
{
        unsigned long timer;
        u32 value;

        if (!attr) {
                *timer_p = fallback;
                *has_p = false;
                return 0;
        }

        value = nla_get_u32(attr);
        timer = clock_t_to_jiffies(value);
        if (timer == ~0UL) {
                NL_SET_ERR_MSG(extack, "Timer value too large");
                return -EINVAL;
        }

        *timer_p = timer;
        *has_p = true;
        return 0;
}

static int rtm_to_nh_config_grp_res(struct nlattr *res, struct nh_config *cfg,
                                    struct netlink_ext_ack *extack)
{
        struct nlattr *tb[ARRAY_SIZE(rtm_nh_res_policy_new)] = {};
        int err;

        if (res) {
                err = nla_parse_nested(tb,
                                       ARRAY_SIZE(rtm_nh_res_policy_new) - 1,
                                       res, rtm_nh_res_policy_new, extack);
                if (err < 0)
                        return err;
        }

        if (tb[NHA_RES_GROUP_BUCKETS]) {
                cfg->nh_grp_res_num_buckets =
                        nla_get_u16(tb[NHA_RES_GROUP_BUCKETS]);
                cfg->nh_grp_res_has_num_buckets = true;
                if (!cfg->nh_grp_res_num_buckets) {
                        NL_SET_ERR_MSG(extack, "Number of buckets needs to be non-0");
                        return -EINVAL;
                }
        }

        err = rtm_nh_get_timer(tb[NHA_RES_GROUP_IDLE_TIMER],
                               NH_RES_DEFAULT_IDLE_TIMER,
                               &cfg->nh_grp_res_idle_timer,
                               &cfg->nh_grp_res_has_idle_timer,
                               extack);
        if (err)
                return err;

        return rtm_nh_get_timer(tb[NHA_RES_GROUP_UNBALANCED_TIMER],
                                NH_RES_DEFAULT_UNBALANCED_TIMER,
                                &cfg->nh_grp_res_unbalanced_timer,
                                &cfg->nh_grp_res_has_unbalanced_timer,
                                extack);
}

static int rtm_to_nh_config(struct net *net, struct sk_buff *skb,
                            struct nlmsghdr *nlh, struct nh_config *cfg,
                            struct netlink_ext_ack *extack)
{
        struct nhmsg *nhm = nlmsg_data(nlh);
        struct nlattr *tb[ARRAY_SIZE(rtm_nh_policy_new)];
        int err;

        err = nlmsg_parse(nlh, sizeof(*nhm), tb,
                          ARRAY_SIZE(rtm_nh_policy_new) - 1,
                          rtm_nh_policy_new, extack);
        if (err < 0)
                return err;

        err = -EINVAL;
        if (nhm->resvd || nhm->nh_scope) {
                NL_SET_ERR_MSG(extack, "Invalid values in ancillary header");
                goto out;
        }
        if (nhm->nh_flags & ~NEXTHOP_VALID_USER_FLAGS) {
                NL_SET_ERR_MSG(extack, "Invalid nexthop flags in ancillary header");
                goto out;
        }

        switch (nhm->nh_family) {
        case AF_INET:
        case AF_INET6:
                break;
        case AF_UNSPEC:
                if (tb[NHA_GROUP])
                        break;
                fallthrough;
        default:
                NL_SET_ERR_MSG(extack, "Invalid address family");
                goto out;
        }

        memset(cfg, 0, sizeof(*cfg));
        cfg->nlflags = nlh->nlmsg_flags;
        cfg->nlinfo.portid = NETLINK_CB(skb).portid;
        cfg->nlinfo.nlh = nlh;
        cfg->nlinfo.nl_net = net;

        cfg->nh_family = nhm->nh_family;
        cfg->nh_protocol = nhm->nh_protocol;
        cfg->nh_flags = nhm->nh_flags;

        if (tb[NHA_ID])
                cfg->nh_id = nla_get_u32(tb[NHA_ID]);

        if (tb[NHA_FDB]) {
                if (tb[NHA_OIF] || tb[NHA_BLACKHOLE] ||
                    tb[NHA_ENCAP]   || tb[NHA_ENCAP_TYPE]) {
                        NL_SET_ERR_MSG(extack, "Fdb attribute can not be used with encap, oif or blackhole");
                        goto out;
                }
                if (nhm->nh_flags) {
                        NL_SET_ERR_MSG(extack, "Unsupported nexthop flags in ancillary header");
                        goto out;
                }
                cfg->nh_fdb = nla_get_flag(tb[NHA_FDB]);
        }

        if (tb[NHA_GROUP]) {
                if (nhm->nh_family != AF_UNSPEC) {
                        NL_SET_ERR_MSG(extack, "Invalid family for group");
                        goto out;
                }
                cfg->nh_grp = tb[NHA_GROUP];

                cfg->nh_grp_type = NEXTHOP_GRP_TYPE_MPATH;
                if (tb[NHA_GROUP_TYPE])
                        cfg->nh_grp_type = nla_get_u16(tb[NHA_GROUP_TYPE]);

                if (cfg->nh_grp_type > NEXTHOP_GRP_TYPE_MAX) {
                        NL_SET_ERR_MSG(extack, "Invalid group type");
                        goto out;
                }
                err = nh_check_attr_group(net, tb, ARRAY_SIZE(tb),
                                          cfg->nh_grp_type, extack);
                if (err)
                        goto out;

                if (cfg->nh_grp_type == NEXTHOP_GRP_TYPE_RES)
                        err = rtm_to_nh_config_grp_res(tb[NHA_RES_GROUP],
                                                       cfg, extack);

                /* no other attributes should be set */
                goto out;
        }

        if (tb[NHA_BLACKHOLE]) {
                if (tb[NHA_GATEWAY] || tb[NHA_OIF] ||
                    tb[NHA_ENCAP]   || tb[NHA_ENCAP_TYPE] || tb[NHA_FDB]) {
                        NL_SET_ERR_MSG(extack, "Blackhole attribute can not be used with gateway, oif, encap or fdb");
                        goto out;
                }

                cfg->nh_blackhole = 1;
                err = 0;
                goto out;
        }

        if (!cfg->nh_fdb && !tb[NHA_OIF]) {
                NL_SET_ERR_MSG(extack, "Device attribute required for non-blackhole and non-fdb nexthops");
                goto out;
        }

        if (!cfg->nh_fdb && tb[NHA_OIF]) {
                cfg->nh_ifindex = nla_get_u32(tb[NHA_OIF]);
                if (cfg->nh_ifindex)
                        cfg->dev = __dev_get_by_index(net, cfg->nh_ifindex);

                if (!cfg->dev) {
                        NL_SET_ERR_MSG(extack, "Invalid device index");
                        goto out;
                } else if (!(cfg->dev->flags & IFF_UP)) {
                        NL_SET_ERR_MSG(extack, "Nexthop device is not up");
                        err = -ENETDOWN;
                        goto out;
                } else if (!netif_carrier_ok(cfg->dev)) {
                        NL_SET_ERR_MSG(extack, "Carrier for nexthop device is down");
                        err = -ENETDOWN;
                        goto out;
                }
        }

        err = -EINVAL;
        if (tb[NHA_GATEWAY]) {
                struct nlattr *gwa = tb[NHA_GATEWAY];

                switch (cfg->nh_family) {
                case AF_INET:
                        if (nla_len(gwa) != sizeof(u32)) {
                                NL_SET_ERR_MSG(extack, "Invalid gateway");
                                goto out;
                        }
                        cfg->gw.ipv4 = nla_get_be32(gwa);
                        break;
                case AF_INET6:
                        if (nla_len(gwa) != sizeof(struct in6_addr)) {
                                NL_SET_ERR_MSG(extack, "Invalid gateway");
                                goto out;
                        }
                        cfg->gw.ipv6 = nla_get_in6_addr(gwa);
                        break;
                default:
                        NL_SET_ERR_MSG(extack,
                                       "Unknown address family for gateway");
                        goto out;
                }
        } else {
                /* device only nexthop (no gateway) */
                if (cfg->nh_flags & RTNH_F_ONLINK) {
                        NL_SET_ERR_MSG(extack,
                                       "ONLINK flag can not be set for nexthop without a gateway");
                        goto out;
                }
        }

        if (tb[NHA_ENCAP]) {
                cfg->nh_encap = tb[NHA_ENCAP];

                if (!tb[NHA_ENCAP_TYPE]) {
                        NL_SET_ERR_MSG(extack, "LWT encapsulation type is missing");
                        goto out;
                }

                cfg->nh_encap_type = nla_get_u16(tb[NHA_ENCAP_TYPE]);
                err = lwtunnel_valid_encap_type(cfg->nh_encap_type, extack);
                if (err < 0)
                        goto out;

        } else if (tb[NHA_ENCAP_TYPE]) {
                NL_SET_ERR_MSG(extack, "LWT encapsulation attribute is missing");
                goto out;
        }


        err = 0;
out:
        return err;
}

/* rtnl */
static int rtm_new_nexthop(struct sk_buff *skb, struct nlmsghdr *nlh,
                           struct netlink_ext_ack *extack)
{
        struct net *net = sock_net(skb->sk);
        struct nh_config cfg;
        struct nexthop *nh;
        int err;

        err = rtm_to_nh_config(net, skb, nlh, &cfg, extack);
        if (!err) {
                nh = nexthop_add(net, &cfg, extack);
                if (IS_ERR(nh))
                        err = PTR_ERR(nh);
        }

        return err;
}

static int __nh_valid_get_del_req(const struct nlmsghdr *nlh,
                                  struct nlattr **tb, u32 *id,
                                  struct netlink_ext_ack *extack)
{
        struct nhmsg *nhm = nlmsg_data(nlh);

        if (nhm->nh_protocol || nhm->resvd || nhm->nh_scope || nhm->nh_flags) {
                NL_SET_ERR_MSG(extack, "Invalid values in header");
                return -EINVAL;
        }

        if (!tb[NHA_ID]) {
                NL_SET_ERR_MSG(extack, "Nexthop id is missing");
                return -EINVAL;
        }

        *id = nla_get_u32(tb[NHA_ID]);
        if (!(*id)) {
                NL_SET_ERR_MSG(extack, "Invalid nexthop id");
                return -EINVAL;
        }

        return 0;
}

static int nh_valid_get_del_req(const struct nlmsghdr *nlh, u32 *id,
                                struct netlink_ext_ack *extack)
{
        struct nlattr *tb[ARRAY_SIZE(rtm_nh_policy_get)];
        int err;

        err = nlmsg_parse(nlh, sizeof(struct nhmsg), tb,
                          ARRAY_SIZE(rtm_nh_policy_get) - 1,
                          rtm_nh_policy_get, extack);
        if (err < 0)
                return err;

        return __nh_valid_get_del_req(nlh, tb, id, extack);
}

/* rtnl */
static int rtm_del_nexthop(struct sk_buff *skb, struct nlmsghdr *nlh,
                           struct netlink_ext_ack *extack)
{
        struct net *net = sock_net(skb->sk);
        struct nl_info nlinfo = {
                .nlh = nlh,
                .nl_net = net,
                .portid = NETLINK_CB(skb).portid,
        };
        struct nexthop *nh;
        int err;
        u32 id;

        err = nh_valid_get_del_req(nlh, &id, extack);
        if (err)
                return err;

        nh = nexthop_find_by_id(net, id);
        if (!nh)
                return -ENOENT;

        remove_nexthop(net, nh, &nlinfo);

        return 0;
}

/* rtnl */
static int rtm_get_nexthop(struct sk_buff *in_skb, struct nlmsghdr *nlh,
                           struct netlink_ext_ack *extack)
{
        struct net *net = sock_net(in_skb->sk);
        struct sk_buff *skb = NULL;
        struct nexthop *nh;
        int err;
        u32 id;

        err = nh_valid_get_del_req(nlh, &id, extack);
        if (err)
                return err;

        err = -ENOBUFS;
        skb = alloc_skb(NLMSG_GOODSIZE, GFP_KERNEL);
        if (!skb)