/*
 * INET         An implementation of the TCP/IP protocol suite for the LINUX
 *              operating system.  INET is implemented using the  BSD Socket
 *              interface as the means of communication with the user level.
 *
 *              IPv4 Forwarding Information Base: semantics.
 *
 * Authors:     Alexey Kuznetsov, <kuznet@ms2.inr.ac.ru>
 *
 *              This program is free software; you can redistribute it and/or
 *              modify it under the terms of the GNU General Public License
 *              as published by the Free Software Foundation; either version
 *              2 of the License, or (at your option) any later version.
 */

#include <asm/uaccess.h>
#include <asm/system.h>
#include <linux/bitops.h>
#include <linux/types.h>
#include <linux/kernel.h>
#include <linux/jiffies.h>
#include <linux/mm.h>
#include <linux/string.h>
#include <linux/socket.h>
#include <linux/sockios.h>
#include <linux/errno.h>
#include <linux/in.h>
#include <linux/inet.h>
#include <linux/inetdevice.h>
#include <linux/netdevice.h>
#include <linux/if_arp.h>
#include <linux/proc_fs.h>
#include <linux/skbuff.h>
#include <linux/init.h>
#include <linux/slab.h>

#include <net/arp.h>
#include <net/ip.h>
#include <net/protocol.h>
#include <net/route.h>
#include <net/tcp.h>
#include <net/sock.h>
#include <net/ip_fib.h>
#include <net/netlink.h>
#include <net/nexthop.h>

#include "fib_lookup.h"

static DEFINE_SPINLOCK(fib_info_lock);
static struct hlist_head *fib_info_hash;
static struct hlist_head *fib_info_laddrhash;
static unsigned int fib_hash_size;
static unsigned int fib_info_cnt;

#define DEVINDEX_HASHBITS 8
#define DEVINDEX_HASHSIZE (1U << DEVINDEX_HASHBITS)
static struct hlist_head fib_info_devhash[DEVINDEX_HASHSIZE];

#ifdef CONFIG_IP_ROUTE_MULTIPATH

static DEFINE_SPINLOCK(fib_multipath_lock);

#define for_nexthops(fi) {                                              \
        int nhsel; const struct fib_nh *nh;                             \
        for (nhsel = 0, nh = (fi)->fib_nh;                              \
             nhsel < (fi)->fib_nhs;                                     \
             nh++, nhsel++)

#define change_nexthops(fi) {                                           \
        int nhsel; struct fib_nh *nexthop_nh;                           \
        for (nhsel = 0, nexthop_nh = (struct fib_nh *)((fi)->fib_nh);   \
             nhsel < (fi)->fib_nhs;                                     \
             nexthop_nh++, nhsel++)

#else /* CONFIG_IP_ROUTE_MULTIPATH */

/* Hope, that gcc will optimize it to get rid of dummy loop */

#define for_nexthops(fi) {                                              \
        int nhsel; const struct fib_nh *nh = (fi)->fib_nh;              \
        for (nhsel = 0; nhsel < 1; nhsel++)

#define change_nexthops(fi) {                                           \
        int nhsel;                                                      \
        struct fib_nh *nexthop_nh = (struct fib_nh *)((fi)->fib_nh);    \
        for (nhsel = 0; nhsel < 1; nhsel++)

#endif /* CONFIG_IP_ROUTE_MULTIPATH */

#define endfor_nexthops(fi) }


static const struct
{
        int     error;
        u8      scope;
} fib_props[RTN_MAX + 1] = {
        [RTN_UNSPEC] = {
                .error  = 0,
                .scope  = RT_SCOPE_NOWHERE,
        },
        [RTN_UNICAST] = {
                .error  = 0,
                .scope  = RT_SCOPE_UNIVERSE,
        },
        [RTN_LOCAL] = {
                .error  = 0,
                .scope  = RT_SCOPE_HOST,
        },
        [RTN_BROADCAST] = {
                .error  = 0,
                .scope  = RT_SCOPE_LINK,
        },
        [RTN_ANYCAST] = {
                .error  = 0,
                .scope  = RT_SCOPE_LINK,
        },
        [RTN_MULTICAST] = {
                .error  = 0,
                .scope  = RT_SCOPE_UNIVERSE,
        },
        [RTN_BLACKHOLE] = {
                .error  = -EINVAL,
                .scope  = RT_SCOPE_UNIVERSE,
        },
        [RTN_UNREACHABLE] = {
                .error  = -EHOSTUNREACH,
                .scope  = RT_SCOPE_UNIVERSE,
        },
        [RTN_PROHIBIT] = {
                .error  = -EACCES,
                .scope  = RT_SCOPE_UNIVERSE,
        },
        [RTN_THROW] = {
                .error  = -EAGAIN,
                .scope  = RT_SCOPE_UNIVERSE,
        },
        [RTN_NAT] = {
                .error  = -EINVAL,
                .scope  = RT_SCOPE_NOWHERE,
        },
        [RTN_XRESOLVE] = {
                .error  = -EINVAL,
                .scope  = RT_SCOPE_NOWHERE,
        },
};


/* Release a nexthop info record */

static void free_fib_info_rcu(struct rcu_head *head)
{
        struct fib_info *fi = container_of(head, struct fib_info, rcu);

        kfree(fi);
}

void free_fib_info(struct fib_info *fi)
{
        if (fi->fib_dead == 0) {
                pr_warning("Freeing alive fib_info %p\n", fi);
                return;
        }
        change_nexthops(fi) {
                if (nexthop_nh->nh_dev)
                        dev_put(nexthop_nh->nh_dev);
                nexthop_nh->nh_dev = NULL;
        } endfor_nexthops(fi);
        fib_info_cnt--;
        release_net(fi->fib_net);
        call_rcu(&fi->rcu, free_fib_info_rcu);
}

void fib_release_info(struct fib_info *fi)
{
        spin_lock_bh(&fib_info_lock);
        if (fi && --fi->fib_treeref == 0) {
                hlist_del(&fi->fib_hash);
                if (fi->fib_prefsrc)
                        hlist_del(&fi->fib_lhash);
                change_nexthops(fi) {
                        if (!nexthop_nh->nh_dev)
                                continue;
                        hlist_del(&nexthop_nh->nh_hash);
                } endfor_nexthops(fi)
                fi->fib_dead = 1;
                fib_info_put(fi);
        }
        spin_unlock_bh(&fib_info_lock);
}

static inline int nh_comp(const struct fib_info *fi, const struct fib_info *ofi)
{
        const struct fib_nh *onh = ofi->fib_nh;

        for_nexthops(fi) {
                if (nh->nh_oif != onh->nh_oif ||
                    nh->nh_gw  != onh->nh_gw ||
                    nh->nh_scope != onh->nh_scope ||
#ifdef CONFIG_IP_ROUTE_MULTIPATH
                    nh->nh_weight != onh->nh_weight ||
#endif
#ifdef CONFIG_NET_CLS_ROUTE
                    nh->nh_tclassid != onh->nh_tclassid ||
#endif
                    ((nh->nh_flags ^ onh->nh_flags) & ~RTNH_F_DEAD))
                        return -1;
                onh++;
        } endfor_nexthops(fi);
        return 0;
}

static inline unsigned int fib_devindex_hashfn(unsigned int val)
{
        unsigned int mask = DEVINDEX_HASHSIZE - 1;

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

static inline unsigned int fib_info_hashfn(const struct fib_info *fi)
{
        unsigned int mask = (fib_hash_size - 1);
        unsigned int val = fi->fib_nhs;

        val ^= fi->fib_protocol;
        val ^= (__force u32)fi->fib_prefsrc;
        val ^= fi->fib_priority;
        for_nexthops(fi) {
                val ^= fib_devindex_hashfn(nh->nh_oif);
        } endfor_nexthops(fi)

        return (val ^ (val >> 7) ^ (val >> 12)) & mask;
}

static struct fib_info *fib_find_info(const struct fib_info *nfi)
{
        struct hlist_head *head;
        struct hlist_node *node;
        struct fib_info *fi;
        unsigned int hash;

        hash = fib_info_hashfn(nfi);
        head = &fib_info_hash[hash];

        hlist_for_each_entry(fi, node, head, fib_hash) {
                if (!net_eq(fi->fib_net, nfi->fib_net))
                        continue;
                if (fi->fib_nhs != nfi->fib_nhs)
                        continue;
                if (nfi->fib_protocol == fi->fib_protocol &&
                    nfi->fib_prefsrc == fi->fib_prefsrc &&
                    nfi->fib_priority == fi->fib_priority &&
                    memcmp(nfi->fib_metrics, fi->fib_metrics,
                           sizeof(fi->fib_metrics)) == 0 &&
                    ((nfi->fib_flags ^ fi->fib_flags) & ~RTNH_F_DEAD) == 0 &&
                    (nfi->fib_nhs == 0 || nh_comp(fi, nfi) == 0))
                        return fi;
        }

        return NULL;
}

/* Check, that the gateway is already configured.
 * Used only by redirect accept routine.
 */
int ip_fib_check_default(__be32 gw, struct net_device *dev)
{
        struct hlist_head *head;
        struct hlist_node *node;
        struct fib_nh *nh;
        unsigned int hash;

        spin_lock(&fib_info_lock);

        hash = fib_devindex_hashfn(dev->ifindex);
        head = &fib_info_devhash[hash];
        hlist_for_each_entry(nh, node, head, nh_hash) {
                if (nh->nh_dev == dev &&
                    nh->nh_gw == gw &&
                    !(nh->nh_flags & RTNH_F_DEAD)) {
                        spin_unlock(&fib_info_lock);
                        return 0;
                }
        }

        spin_unlock(&fib_info_lock);

        return -1;
}

static inline size_t fib_nlmsg_size(struct fib_info *fi)
{
        size_t payload = NLMSG_ALIGN(sizeof(struct rtmsg))
                         + nla_total_size(4) /* RTA_TABLE */
                         + nla_total_size(4) /* RTA_DST */
                         + nla_total_size(4) /* RTA_PRIORITY */
                         + nla_total_size(4); /* RTA_PREFSRC */

        /* space for nested metrics */
        payload += nla_total_size((RTAX_MAX * nla_total_size(4)));

        if (fi->fib_nhs) {
                /* Also handles the special case fib_nhs == 1 */

                /* each nexthop is packed in an attribute */
                size_t nhsize = nla_total_size(sizeof(struct rtnexthop));

                /* may contain flow and gateway attribute */
                nhsize += 2 * nla_total_size(4);

                /* all nexthops are packed in a nested attribute */
                payload += nla_total_size(fi->fib_nhs * nhsize);
        }

        return payload;
}

void rtmsg_fib(int event, __be32 key, struct fib_alias *fa,
               int dst_len, u32 tb_id, struct nl_info *info,
               unsigned int nlm_flags)
{
        struct sk_buff *skb;
        u32 seq = info->nlh ? info->nlh->nlmsg_seq : 0;
        int err = -ENOBUFS;

        skb = nlmsg_new(fib_nlmsg_size(fa->fa_info), GFP_KERNEL);
        if (skb == NULL)
                goto errout;

        err = fib_dump_info(skb, info->pid, seq, event, tb_id,
                            fa->fa_type, fa->fa_scope, key, dst_len,
                            fa->fa_tos, fa->fa_info, nlm_flags);
        if (err < 0) {
                /* -EMSGSIZE implies BUG in fib_nlmsg_size() */
                WARN_ON(err == -EMSGSIZE);
                kfree_skb(skb);
                goto errout;
        }
        rtnl_notify(skb, info->nl_net, info->pid, RTNLGRP_IPV4_ROUTE,
                    info->nlh, GFP_KERNEL);
        return;
errout:
        if (err < 0)
                rtnl_set_sk_err(info->nl_net, RTNLGRP_IPV4_ROUTE, err);
}

/* Return the first fib alias matching TOS with
 * priority less than or equal to PRIO.
 */
struct fib_alias *fib_find_alias(struct list_head *fah, u8 tos, u32 prio)
{
        if (fah) {
                struct fib_alias *fa;
                list_for_each_entry(fa, fah, fa_list) {
                        if (fa->fa_tos > tos)
                                continue;
                        if (fa->fa_info->fib_priority >= prio ||
                            fa->fa_tos < tos)
                                return fa;
                }
        }
        return NULL;
}

int fib_detect_death(struct fib_info *fi, int order,
                     struct fib_info **last_resort, int *last_idx, int dflt)
{
        struct neighbour *n;
        int state = NUD_NONE;

        n = neigh_lookup(&arp_tbl, &fi->fib_nh[0].nh_gw, fi->fib_dev);
        if (n) {
                state = n->nud_state;
                neigh_release(n);
        }
        if (state == NUD_REACHABLE)
                return 0;
        if ((state & NUD_VALID) && order != dflt)
                return 0;
        if ((state & NUD_VALID) ||
            (*last_idx < 0 && order > dflt)) {
                *last_resort = fi;
                *last_idx = order;
        }
        return 1;
}

#ifdef CONFIG_IP_ROUTE_MULTIPATH

static int fib_count_nexthops(struct rtnexthop *rtnh, int remaining)
{
        int nhs = 0;

        while (rtnh_ok(rtnh, remaining)) {
                nhs++;
                rtnh = rtnh_next(rtnh, &remaining);
        }

        /* leftover implies invalid nexthop configuration, discard it */
        return remaining > 0 ? 0 : nhs;
}

static int fib_get_nhs(struct fib_info *fi, struct rtnexthop *rtnh,
                       int remaining, struct fib_config *cfg)
{
        change_nexthops(fi) {
                int attrlen;

                if (!rtnh_ok(rtnh, remaining))
                        return -EINVAL;

                nexthop_nh->nh_flags =
                        (cfg->fc_flags & ~0xFF) | rtnh->rtnh_flags;
                nexthop_nh->nh_oif = rtnh->rtnh_ifindex;
                nexthop_nh->nh_weight = rtnh->rtnh_hops + 1;

                attrlen = rtnh_attrlen(rtnh);
                if (attrlen > 0) {
                        struct nlattr *nla, *attrs = rtnh_attrs(rtnh);

                        nla = nla_find(attrs, attrlen, RTA_GATEWAY);
                        nexthop_nh->nh_gw = nla ? nla_get_be32(nla) : 0;
#ifdef CONFIG_NET_CLS_ROUTE
                        nla = nla_find(attrs, attrlen, RTA_FLOW);
                        nexthop_nh->nh_tclassid = nla ? nla_get_u32(nla) : 0;
#endif
                }

                rtnh = rtnh_next(rtnh, &remaining);
        } endfor_nexthops(fi);

        return 0;
}

#endif

int fib_nh_match(struct fib_config *cfg, struct fib_info *fi)
{
#ifdef CONFIG_IP_ROUTE_MULTIPATH
        struct rtnexthop *rtnh;
        int remaining;
#endif

        if (cfg->fc_priority && cfg->fc_priority != fi->fib_priority)
                return 1;

        if (cfg->fc_oif || cfg->fc_gw) {
                if ((!cfg->fc_oif || cfg->fc_oif == fi->fib_nh->nh_oif) &&
                    (!cfg->fc_gw  || cfg->fc_gw == fi->fib_nh->nh_gw))
                        return 0;
                return 1;
        }

#ifdef CONFIG_IP_ROUTE_MULTIPATH
        if (cfg->fc_mp == NULL)
                return 0;

        rtnh = cfg->fc_mp;
        remaining = cfg->fc_mp_len;

        for_nexthops(fi) {
                int attrlen;

                if (!rtnh_ok(rtnh, remaining))
                        return -EINVAL;

                if (rtnh->rtnh_ifindex && rtnh->rtnh_ifindex != nh->nh_oif)
                        return 1;

                attrlen = rtnh_attrlen(rtnh);
                if (attrlen < 0) {
                        struct nlattr *nla, *attrs = rtnh_attrs(rtnh);

                        nla = nla_find(attrs, attrlen, RTA_GATEWAY);
                        if (nla && nla_get_be32(nla) != nh->nh_gw)
                                return 1;
#ifdef CONFIG_NET_CLS_ROUTE
                        nla = nla_find(attrs, attrlen, RTA_FLOW);
                        if (nla && nla_get_u32(nla) != nh->nh_tclassid)
                                return 1;
#endif
                }

                rtnh = rtnh_next(rtnh, &remaining);
        } endfor_nexthops(fi);
#endif
        return 0;
}


/*
 * Picture
 * -------
 *
 * Semantics of nexthop is very messy by historical reasons.
 * We have to take into account, that:
 * a) gateway can be actually local interface address,
 *    so that gatewayed route is direct.
 * b) gateway must be on-link address, possibly
 *    described not by an ifaddr, but also by a direct route.
 * c) If both gateway and interface are specified, they should not
 *    contradict.
 * d) If we use tunnel routes, gateway could be not on-link.
 *
 * Attempt to reconcile all of these (alas, self-contradictory) conditions
 * results in pretty ugly and hairy code with obscure logic.
 *
 * I chose to generalized it instead, so that the size
 * of code does not increase practically, but it becomes
 * much more general.
 * Every prefix is assigned a "scope" value: "host" is local address,
 * "link" is direct route,
 * [ ... "site" ... "interior" ... ]
 * and "universe" is true gateway route with global meaning.
 *
 * Every prefix refers to a set of "nexthop"s (gw, oif),
 * where gw must have narrower scope. This recursion stops
 * when gw has LOCAL scope or if "nexthop" is declared ONLINK,
 * which means that gw is forced to be on link.
 *
 * Code is still hairy, but now it is apparently logically
 * consistent and very flexible. F.e. as by-product it allows
 * to co-exists in peace independent exterior and interior
 * routing processes.
 *
 * Normally it looks as following.
 *
 * {universe prefix}  -> (gw, oif) [scope link]
 *                |
 *                |-> {link prefix} -> (gw, oif) [scope local]
 *                                      |
 *                                      |-> {local prefix} (terminal node)
 */
static int fib_check_nh(struct fib_config *cfg, struct fib_info *fi,
                        struct fib_nh *nh)
{
        int err;
        struct net *net;
        struct net_device *dev;

        net = cfg->fc_nlinfo.nl_net;
        if (nh->nh_gw) {
                struct fib_result res;

                if (nh->nh_flags & RTNH_F_ONLINK) {

                        if (cfg->fc_scope >= RT_SCOPE_LINK)
                                return -EINVAL;
                        if (inet_addr_type(net, nh->nh_gw) != RTN_UNICAST)
                                return -EINVAL;
                        dev = __dev_get_by_index(net, nh->nh_oif);
                        if (!dev)
                                return -ENODEV;
                        if (!(dev->flags & IFF_UP))
                                return -ENETDOWN;
                        nh->nh_dev = dev;
                        dev_hold(dev);
                        nh->nh_scope = RT_SCOPE_LINK;
                        return 0;
                }
                rcu_read_lock();
                {
                        struct flowi fl = {
                                .fl4_dst = nh->nh_gw,
                                .fl4_scope = cfg->fc_scope + 1,
                                .oif = nh->nh_oif,
                        };

                        /* It is not necessary, but requires a bit of thinking */
                        if (fl.fl4_scope < RT_SCOPE_LINK)
                                fl.fl4_scope = RT_SCOPE_LINK;
                        err = fib_lookup(net, &fl, &res);
                        if (err) {
                                rcu_read_unlock();
                                return err;
                        }
                }
                err = -EINVAL;
                if (res.type != RTN_UNICAST && res.type != RTN_LOCAL)
                        goto out;
                nh->nh_scope = res.scope;
                nh->nh_oif = FIB_RES_OIF(res);
                nh->nh_dev = dev = FIB_RES_DEV(res);
                if (!dev)
                        goto out;
                dev_hold(dev);
                err = (dev->flags & IFF_UP) ? 0 : -ENETDOWN;
        } else {
                struct in_device *in_dev;

                if (nh->nh_flags & (RTNH_F_PERVASIVE | RTNH_F_ONLINK))
                        return -EINVAL;

                rcu_read_lock();
                err = -ENODEV;
                in_dev = inetdev_by_index(net, nh->nh_oif);
                if (in_dev == NULL)
                        goto out;
                err = -ENETDOWN;
                if (!(in_dev->dev->flags & IFF_UP))
                        goto out;
                nh->nh_dev = in_dev->dev;
                dev_hold(nh->nh_dev);
                nh->nh_scope = RT_SCOPE_HOST;
                err = 0;
        }
out:
        rcu_read_unlock();
        return err;
}

static inline unsigned int fib_laddr_hashfn(__be32 val)
{
        unsigned int mask = (fib_hash_size - 1);

        return ((__force u32)val ^
                ((__force u32)val >> 7) ^
                ((__force u32)val >> 14)) & mask;
}

static struct hlist_head *fib_hash_alloc(int bytes)
{
        if (bytes <= PAGE_SIZE)
                return kzalloc(bytes, GFP_KERNEL);
        else
                return (struct hlist_head *)
                        __get_free_pages(GFP_KERNEL | __GFP_ZERO,
                                         get_order(bytes));
}

static void fib_hash_free(struct hlist_head *hash, int bytes)
{
        if (!hash)
                return;

        if (bytes <= PAGE_SIZE)
                kfree(hash);
        else
                free_pages((unsigned long) hash, get_order(bytes));
}

static void fib_hash_move(struct hlist_head *new_info_hash,
                          struct hlist_head *new_laddrhash,
                          unsigned int new_size)
{
        struct hlist_head *old_info_hash, *old_laddrhash;
        unsigned int old_size = fib_hash_size;
        unsigned int i, bytes;

        spin_lock_bh(&fib_info_lock);
        old_info_hash = fib_info_hash;
        old_laddrhash = fib_info_laddrhash;
        fib_hash_size = new_size;

        for (i = 0; i < old_size; i++) {
                struct hlist_head *head = &fib_info_hash[i];
                struct hlist_node *node, *n;
                struct fib_info *fi;

                hlist_for_each_entry_safe(fi, node, n, head, fib_hash) {
                        struct hlist_head *dest;
                        unsigned int new_hash;

                        hlist_del(&fi->fib_hash);

                        new_hash = fib_info_hashfn(fi);
                        dest = &new_info_hash[new_hash];
                        hlist_add_head(&fi->fib_hash, dest);
                }
        }
        fib_info_hash = new_info_hash;

        for (i = 0; i < old_size; i++) {
                struct hlist_head *lhead = &fib_info_laddrhash[i];
                struct hlist_node *node, *n;
                struct fib_info *fi;

                hlist_for_each_entry_safe(fi, node, n, lhead, fib_lhash) {
                        struct hlist_head *ldest;
                        unsigned int new_hash;

                        hlist_del(&fi->fib_lhash);

                        new_hash = fib_laddr_hashfn(fi->fib_prefsrc);
                        ldest = &new_laddrhash[new_hash];
                        hlist_add_head(&fi->fib_lhash, ldest);
                }
        }
        fib_info_laddrhash = new_laddrhash;

        spin_unlock_bh(&fib_info_lock);

        bytes = old_size * sizeof(struct hlist_head *);
        fib_hash_free(old_info_hash, bytes);
        fib_hash_free(old_laddrhash, bytes);
}

struct fib_info *fib_create_info(struct fib_config *cfg)
{
        int err;
        struct fib_info *fi = NULL;
        struct fib_info *ofi;
        int nhs = 1;
        struct net *net = cfg->fc_nlinfo.nl_net;

        /* Fast check to catch the most weird cases */
        if (fib_props[cfg->fc_type].scope > cfg->fc_scope)
                goto err_inval;

#ifdef CONFIG_IP_ROUTE_MULTIPATH
        if (cfg->fc_mp) {
                nhs = fib_count_nexthops(cfg->fc_mp, cfg->fc_mp_len);
                if (nhs == 0)
                        goto err_inval;
        }
#endif

        err = -ENOBUFS;
        if (fib_info_cnt >= fib_hash_size) {
                unsigned int new_size = fib_hash_size << 1;
                struct hlist_head *new_info_hash;
                struct hlist_head *new_laddrhash;
                unsigned int bytes;

                if (!new_size)
                        new_size = 1;
                bytes = new_size * sizeof(struct hlist_head *);
                new_info_hash = fib_hash_alloc(bytes);
                new_laddrhash = fib_hash_alloc(bytes);
                if (!new_info_hash || !new_laddrhash) {
                        fib_hash_free(new_info_hash, bytes);
                        fib_hash_free(new_laddrhash, bytes);
                } else
                        fib_hash_move(new_info_hash, new_laddrhash, new_size);

                if (!fib_hash_size)
                        goto failure;
        }

        fi = kzalloc(sizeof(*fi)+nhs*sizeof(struct fib_nh), GFP_KERNEL);
        if (fi == NULL)
                goto failure;
        fib_info_cnt++;

        fi->fib_net = hold_net(net);
        fi->fib_protocol = cfg->fc_protocol;
        fi->fib_flags = cfg->fc_flags;
        fi->fib_priority = cfg->fc_priority;
        fi->fib_prefsrc = cfg->fc_prefsrc;

        fi->fib_nhs = nhs;
        change_nexthops(fi) {
                nexthop_nh->nh_parent = fi;
        } endfor_nexthops(fi)

        if (cfg->fc_mx) {
                struct nlattr *nla;
                int remaining;

                nla_for_each_attr(nla, cfg->fc_mx, cfg->fc_mx_len, remaining) {
                        int type = nla_type(nla);

                        if (type) {
                                if (type > RTAX_MAX)
                                        goto err_inval;
                                fi->fib_metrics[type - 1] = nla_get_u32(nla);
                        }
                }
        }

        if (cfg->fc_mp) {
#ifdef CONFIG_IP_ROUTE_MULTIPATH
                err = fib_get_nhs(fi, cfg->fc_mp, cfg->fc_mp_len, cfg);
                if (err != 0)
                        goto failure;
                if (cfg->fc_oif && fi->fib_nh->nh_oif != cfg->fc_oif)
                        goto err_inval;
                if (cfg->fc_gw && fi->fib_nh->nh_gw != cfg->fc_gw)
                        goto err_inval;
#ifdef CONFIG_NET_CLS_ROUTE
                if (cfg->fc_flow && fi->fib_nh->nh_tclassid != cfg->fc_flow)
                        goto err_inval;
#endif
#else
                goto err_inval;
#endif
        } else {
                struct fib_nh *nh = fi->fib_nh;

                nh->nh_oif = cfg->fc_oif;
                nh->nh_gw = cfg->fc_gw;
                nh->nh_flags = cfg->fc_flags;
#ifdef CONFIG_NET_CLS_ROUTE
                nh->nh_tclassid = cfg->fc_flow;
#endif
#ifdef CONFIG_IP_ROUTE_MULTIPATH
                nh->nh_weight = 1;
#endif
        }

        if (fib_props[cfg->fc_type].error) {
                if (cfg->fc_gw || cfg->fc_oif || cfg->fc_mp)
                        goto err_inval;
                goto link_it;
        }

        if (cfg->fc_scope > RT_SCOPE_HOST)
                goto err_inval;

        if (cfg->fc_scope == RT_SCOPE_HOST) {
                struct fib_nh *nh = fi->fib_nh;

                /* Local address is added. */
                if (nhs != 1 || nh->nh_gw)
                        goto err_inval;
                nh->nh_scope = RT_SCOPE_NOWHERE;
                nh->nh_dev = dev_get_by_index(net, fi->fib_nh->nh_oif);
                err = -ENODEV;
                if (nh->nh_dev == NULL)
                        goto failure;
        } else {
                change_nexthops(fi) {
                        err = fib_check_nh(cfg, fi, nexthop_nh);
                        if (err != 0)
                                goto failure;
                } endfor_nexthops(fi)
        }

        if (fi->fib_prefsrc) {
                if (cfg->fc_type != RTN_LOCAL || !cfg->fc_dst ||
                    fi->fib_prefsrc != cfg->fc_dst)
                        if (inet_addr_type(net, fi->fib_prefsrc) != RTN_LOCAL)
                                goto err_inval;
        }

link_it:
        ofi = fib_find_info(fi);
        if (ofi) {
                fi->fib_dead = 1;
                free_fib_info(fi);
                ofi->fib_treeref++;
                return ofi;
        }

        fi->fib_treeref++;
        atomic_inc(&fi->fib_clntref);
        spin_lock_bh(&fib_info_lock);
        hlist_add_head(&fi->fib_hash,
                       &fib_info_hash[fib_info_hashfn(fi)]);
        if (fi->fib_prefsrc) {
                struct hlist_head *head;

                head = &fib_info_laddrhash[fib_laddr_hashfn(fi->fib_prefsrc)];
                hlist_add_head(&fi->fib_lhash, head);
        }
        change_nexthops(fi) {
                struct hlist_head *head;
                unsigned int hash;

                if (!nexthop_nh->nh_dev)
                        continue;
                hash = fib_devindex_hashfn(nexthop_nh->nh_dev->ifindex);
                head = &fib_info_devhash[hash];
                hlist_add_head(&nexthop_nh->nh_hash, head);
        } endfor_nexthops(fi)
        spin_unlock_bh(&fib_info_lock);
        return fi;

err_inval:
        err = -EINVAL;

failure:
        if (fi) {
                fi->fib_dead = 1;
                free_fib_info(fi);
        }

        return ERR_PTR(err);
}

/* Note! fib_semantic_match intentionally uses  RCU list functions. */
int fib_semantic_match(struct list_head *head, const struct flowi *flp,
                       struct fib_result *res, int prefixlen, int fib_flags)
{
        struct fib_alias *fa;
        int nh_sel = 0;

        list_for_each_entry_rcu(fa, head, fa_list) {
                int err;

                if (fa->fa_tos &&
                    fa->fa_tos != flp->fl4_tos)
                        continue;

                if (fa->fa_scope < flp->fl4_scope)
                        continue;

                fib_alias_accessed(fa);

                err = fib_props[fa->fa_type].error;
                if (err == 0) {
                        struct fib_info *fi = fa->fa_info;

                        if (fi->fib_flags & RTNH_F_DEAD)
                                continue;

                        switch (fa->fa_type) {
                        case RTN_UNICAST:
                        case RTN_LOCAL:
                        case RTN_BROADCAST:
                        case RTN_ANYCAST:
                        case RTN_MULTICAST:
                                for_nexthops(fi) {
                                        if (nh->nh_flags & RTNH_F_DEAD)
                                                continue;
                                        if (!flp->oif || flp->oif == nh->nh_oif)
                                                break;
                                }
#ifdef CONFIG_IP_ROUTE_MULTIPATH
                                if (nhsel < fi->fib_nhs) {
                                        nh_sel = nhsel;
                                        goto out_fill_res;
                                }
#else
                                if (nhsel < 1)
                                        goto out_fill_res;
#endif
                                endfor_nexthops(fi);
                                continue;

                        default:
                                pr_warning("fib_semantic_match bad type %#x\n",
                                           fa->fa_type);
                                return -EINVAL;
                        }
                }
                return err;
        }
        return 1;

out_fill_res:
        res->prefixlen = prefixlen;
        res->nh_sel = nh_sel;
        res->type = fa->fa_type;
        res->scope = fa->fa_scope;
        res->fi = fa->fa_info;
        if (!(fib_flags & FIB_LOOKUP_NOREF))
                atomic_inc(&res->fi->fib_clntref);
        return 0;
}

/* Find appropriate source address to this destination */

__be32 __fib_res_prefsrc(struct fib_result *res)
{
        return inet_select_addr(FIB_RES_DEV(*res), FIB_RES_GW(*res), res->scope);
}

int fib_dump_info(struct sk_buff *skb, u32 pid, u32 seq, int event,
                  u32 tb_id, u8 type, u8 scope, __be32 dst, int dst_len, u8 tos,
                  struct fib_info *fi, unsigned int flags)
{
        struct nlmsghdr *nlh;
        struct rtmsg *rtm;

        nlh = nlmsg_put(skb, pid, seq, event, sizeof(*rtm), flags);
        if (nlh == NULL)
                return -EMSGSIZE;

        rtm = nlmsg_data(nlh);
        rtm->rtm_family = AF_INET;
        rtm->rtm_dst_len = dst_len;
        rtm->rtm_src_len = 0;
        rtm->rtm_tos = tos;
        if (tb_id < 256)
                rtm->rtm_table = tb_id;
        else
                rtm->rtm_table = RT_TABLE_COMPAT;
        NLA_PUT_U32(skb, RTA_TABLE, tb_id);
        rtm->rtm_type = type;
        rtm->rtm_flags = fi->fib_flags;
        rtm->rtm_scope = scope;
        rtm->rtm_protocol = fi->fib_protocol;

        if (rtm->rtm_dst_len)
                NLA_PUT_BE32(skb, RTA_DST, dst);

        if (fi->fib_priority)
                NLA_PUT_U32(skb, RTA_PRIORITY, fi->fib_priority);

        if (rtnetlink_put_metrics(skb, fi->fib_metrics) < 0)
                goto nla_put_failure;

        if (fi->fib_prefsrc)
                NLA_PUT_BE32(skb, RTA_PREFSRC, fi->fib_prefsrc);

        if (fi->fib_nhs == 1) {
                if (fi->fib_nh->nh_gw)

                        NLA_PUT_BE32(skb, RTA_GATEWAY, fi->fib_nh->nh_gw);

                if (fi->fib_nh->nh_oif)
                        NLA_PUT_U32(skb, RTA_OIF, fi->fib_nh->nh_oif);
#ifdef CONFIG_NET_CLS_ROUTE
                if (fi->fib_nh[0].nh_tclassid)
                        NLA_PUT_U32(skb, RTA_FLOW, fi->fib_nh[0].nh_tclassid);
#endif
        }
#ifdef CONFIG_IP_ROUTE_MULTIPATH
        if (fi->fib_nhs > 1) {
                struct rtnexthop *rtnh;
                struct nlattr *mp;

                mp = nla_nest_start(skb, RTA_MULTIPATH);
                if (mp == NULL)
                        goto nla_put_failure;

                for_nexthops(fi) {
                        rtnh = nla_reserve_nohdr(skb, sizeof(*rtnh));
                        if (rtnh == NULL)
                                goto nla_put_failure;

                        rtnh->rtnh_flags = nh->nh_flags & 0xFF;
                        rtnh->rtnh_hops = nh->nh_weight - 1;
                        rtnh->rtnh_ifindex = nh->nh_oif;

                        if (nh->nh_gw)
                                NLA_PUT_BE32(skb, RTA_GATEWAY, nh->nh_gw);
#ifdef CONFIG_NET_CLS_ROUTE
                        if (nh->nh_tclassid)
                                NLA_PUT_U32(skb, RTA_FLOW, nh->nh_tclassid);
#endif
                        /* length of rtnetlink header + attributes */
                        rtnh->rtnh_len = nlmsg_get_pos(skb) - (void *) rtnh;
                } endfor_nexthops(fi);

                nla_nest_end(skb, mp);
        }
#endif
        return nlmsg_end(skb, nlh);

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

/*
 * Update FIB if:
 * - local address disappeared -> we must delete all the entries
 *   referring to it.
 * - device went down -> we must shutdown all nexthops going via it.
 */
int fib_sync_down_addr(struct net *net, __be32 local)
{
        int ret = 0;
        unsigned int hash = fib_laddr_hashfn(local);
        struct hlist_head *head = &fib_info_laddrhash[hash];
        struct hlist_node *node;
        struct fib_info *fi;

        if (fib_info_laddrhash == NULL || local == 0)
                return 0;

        hlist_for_each_entry(fi, node, head, fib_lhash) {
                if (!net_eq(fi->fib_net, net))
                        continue;
                if (fi->fib_prefsrc == local) {
                        fi->fib_flags |= RTNH_F_DEAD;
                        ret++;
                }
        }
        return ret;
}

int fib_sync_down_dev(struct net_device *dev, int force)
{
        int ret = 0;
        int scope = RT_SCOPE_NOWHERE;
        struct fib_info *prev_fi = NULL;
        unsigned int hash = fib_devindex_hashfn(dev->ifindex);
        struct hlist_head *head = &fib_info_devhash[hash];
        struct hlist_node *node;
        struct fib_nh *nh;

        if (force)
                scope = -1;

        hlist_for_each_entry(nh, node, head, nh_hash) {
                struct fib_info *fi = nh->nh_parent;
                int dead;

                BUG_ON(!fi->fib_nhs);
                if (nh->nh_dev != dev || fi == prev_fi)
                        continue;
                prev_fi = fi;
                dead = 0;
                change_nexthops(fi) {
                        if (nexthop_nh->nh_flags & RTNH_F_DEAD)
                                dead++;
                        else if (nexthop_nh->nh_dev == dev &&
                                 nexthop_nh->nh_scope != scope) {
                                nexthop_nh->nh_flags |= RTNH_F_DEAD;
#ifdef CONFIG_IP_ROUTE_MULTIPATH
                                spin_lock_bh(&fib_multipath_lock);
                                fi->fib_power -= nexthop_nh->nh_power;
                                nexthop_nh->nh_power = 0;
                                spin_unlock_bh(&fib_multipath_lock);
#endif
                                dead++;
                        }
#ifdef CONFIG_IP_ROUTE_MULTIPATH
                        if (force > 1 && nexthop_nh->nh_dev == dev) {
                                dead = fi->fib_nhs;
                                break;
                        }
#endif
                } endfor_nexthops(fi)
                if (dead == fi->fib_nhs) {
                        fi->fib_flags |= RTNH_F_DEAD;
                        ret++;
                }
        }

        return ret;
}

#ifdef CONFIG_IP_ROUTE_MULTIPATH

/*
 * Dead device goes up. We wake up dead nexthops.
 * It takes sense only on multipath routes.
 */
int fib_sync_up(struct net_device *dev)
{
        struct fib_info *prev_fi;
        unsigned int hash;
        struct hlist_head *head;
        struct hlist_node *node;
        struct fib_nh *nh;
        int ret;

        if (!(dev->flags & IFF_UP))
                return 0;

        prev_fi = NULL;
        hash = fib_devindex_hashfn(dev->ifindex);
        head = &fib_info_devhash[hash];
        ret = 0;

        hlist_for_each_entry(nh, node, head, nh_hash) {
                struct fib_info *fi = nh->nh_parent;
                int alive;

                BUG_ON(!fi->fib_nhs);
                if (nh->nh_dev != dev || fi == prev_fi)
                        continue;

                prev_fi = fi;
                alive = 0;
                change_nexthops(fi) {
                        if (!(nexthop_nh->nh_flags & RTNH_F_DEAD)) {
                                alive++;
                                continue;
                        }
                        if (nexthop_nh->nh_dev == NULL ||
                            !(nexthop_nh->nh_dev->flags & IFF_UP))
                                continue;
                        if (nexthop_nh->nh_dev != dev ||
                            !__in_dev_get_rtnl(dev))
                                continue;
                        alive++;
                        spin_lock_bh(&fib_multipath_lock);
                        nexthop_nh->nh_power = 0;
                        nexthop_nh->nh_flags &= ~RTNH_F_DEAD;
                        spin_unlock_bh(&fib_multipath_lock);
                } endfor_nexthops(fi)

                if (alive > 0) {
                        fi->fib_flags &= ~RTNH_F_DEAD;
                        ret++;
                }
        }

        return ret;
}

/*
 * The algorithm is suboptimal, but it provides really
 * fair weighted route distribution.
 */
void fib_select_multipath(const struct flowi *flp, struct fib_result *res)
{
        struct fib_info *fi = res->fi;
        int w;

        spin_lock_bh(&fib_multipath_lock);
        if (fi->fib_power <= 0) {
                int power = 0;
                change_nexthops(fi) {
                        if (!(nexthop_nh->nh_flags & RTNH_F_DEAD)) {
                                power += nexthop_nh->nh_weight;
                                nexthop_nh->nh_power = nexthop_nh->nh_weight;
                        }
                } endfor_nexthops(fi);
                fi->fib_power = power;
                if (power <= 0) {
                        spin_unlock_bh(&fib_multipath_lock);
                        /* Race condition: route has just become dead. */
                        res->nh_sel = 0;
                        return;
                }
        }


        /* w should be random number [0..fi->fib_power-1],
         * it is pretty bad approximation.
         */

        w = jiffies % fi->fib_power;

        change_nexthops(fi) {
                if (!(nexthop_nh->nh_flags & RTNH_F_DEAD) &&
                    nexthop_nh->nh_power) {
                        w -= nexthop_nh->nh_power;
                        if (w <= 0) {
                                nexthop_nh->nh_power--;
                                fi->fib_power--;
                                res->nh_sel = nhsel;
                                spin_unlock_bh(&fib_multipath_lock);
                                return;
                        }
                }
        } endfor_nexthops(fi);

        /* Race condition: route has just become dead. */
        res->nh_sel = 0;
        spin_unlock_bh(&fib_multipath_lock);
}
#endif