// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * vrf.c: device driver to encapsulate a VRF space
 *
 * Copyright (c) 2015 Cumulus Networks. All rights reserved.
 * Copyright (c) 2015 Shrijeet Mukherjee <shm@cumulusnetworks.com>
 * Copyright (c) 2015 David Ahern <dsa@cumulusnetworks.com>
 *
 * Based on dummy, team and ipvlan drivers
 */

#include <linux/ethtool.h>
#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/netdevice.h>
#include <linux/etherdevice.h>
#include <linux/ip.h>
#include <linux/init.h>
#include <linux/moduleparam.h>
#include <linux/netfilter.h>
#include <linux/rtnetlink.h>
#include <net/rtnetlink.h>
#include <linux/u64_stats_sync.h>
#include <linux/hashtable.h>
#include <linux/spinlock_types.h>

#include <linux/inetdevice.h>
#include <net/arp.h>
#include <net/flow.h>
#include <net/ip.h>
#include <net/ip_fib.h>
#include <net/ip6_fib.h>
#include <net/ip6_route.h>
#include <net/route.h>
#include <net/addrconf.h>
#include <net/l3mdev.h>
#include <net/fib_rules.h>
#include <net/netdev_lock.h>
#include <net/sch_generic.h>
#include <net/netns/generic.h>
#include <net/netfilter/nf_conntrack.h>

#define DRV_NAME        "vrf"
#define DRV_VERSION     "1.1"

#define FIB_RULE_PREF  1000       /* default preference for FIB rules */

#define HT_MAP_BITS     4
#define HASH_INITVAL    ((u32)0xcafef00d)

struct  vrf_map {
        DECLARE_HASHTABLE(ht, HT_MAP_BITS);
        spinlock_t vmap_lock;

        /* shared_tables:
         * count how many distinct tables do not comply with the strict mode
         * requirement.
         * shared_tables value must be 0 in order to enable the strict mode.
         *
         * example of the evolution of shared_tables:
         *                                                        | time
         * add  vrf0 --> table 100        shared_tables = 0       | t0
         * add  vrf1 --> table 101        shared_tables = 0       | t1
         * add  vrf2 --> table 100        shared_tables = 1       | t2
         * add  vrf3 --> table 100        shared_tables = 1       | t3
         * add  vrf4 --> table 101        shared_tables = 2       v t4
         *
         * shared_tables is a "step function" (or "staircase function")
         * and it is increased by one when the second vrf is associated to a
         * table.
         *
         * at t2, vrf0 and vrf2 are bound to table 100: shared_tables = 1.
         *
         * at t3, another dev (vrf3) is bound to the same table 100 but the
         * value of shared_tables is still 1.
         * This means that no matter how many new vrfs will register on the
         * table 100, the shared_tables will not increase (considering only
         * table 100).
         *
         * at t4, vrf4 is bound to table 101, and shared_tables = 2.
         *
         * Looking at the value of shared_tables we can immediately know if
         * the strict_mode can or cannot be enforced. Indeed, strict_mode
         * can be enforced iff shared_tables = 0.
         *
         * Conversely, shared_tables is decreased when a vrf is de-associated
         * from a table with exactly two associated vrfs.
         */
        u32 shared_tables;

        bool strict_mode;
};

struct vrf_map_elem {
        struct hlist_node hnode;
        struct list_head vrf_list;  /* VRFs registered to this table */

        u32 table_id;
        int users;
        int ifindex;
};

static unsigned int vrf_net_id;

/* per netns vrf data */
struct netns_vrf {
        /* protected by rtnl lock */
        bool add_fib_rules;

        struct vrf_map vmap;
        struct ctl_table_header *ctl_hdr;
};

struct net_vrf {
        struct rtable __rcu     *rth;
        struct rt6_info __rcu   *rt6;
#if IS_ENABLED(CONFIG_IPV6)
        struct fib6_table       *fib6_table;
#endif
        u32                     tb_id;

        struct list_head        me_list;   /* entry in vrf_map_elem */
        int                     ifindex;
};

static void vrf_tx_error(struct net_device *vrf_dev, struct sk_buff *skb)
{
        vrf_dev->stats.tx_errors++;
        kfree_skb(skb);
}

static struct vrf_map *netns_vrf_map(struct net *net)
{
        struct netns_vrf *nn_vrf = net_generic(net, vrf_net_id);

        return &nn_vrf->vmap;
}

static struct vrf_map *netns_vrf_map_by_dev(struct net_device *dev)
{
        return netns_vrf_map(dev_net(dev));
}

static int vrf_map_elem_get_vrf_ifindex(struct vrf_map_elem *me)
{
        struct list_head *me_head = &me->vrf_list;
        struct net_vrf *vrf;

        if (list_empty(me_head))
                return -ENODEV;

        vrf = list_first_entry(me_head, struct net_vrf, me_list);

        return vrf->ifindex;
}

static struct vrf_map_elem *vrf_map_elem_alloc(gfp_t flags)
{
        struct vrf_map_elem *me;

        me = kmalloc_obj(*me, flags);
        if (!me)
                return NULL;

        return me;
}

static void vrf_map_elem_free(struct vrf_map_elem *me)
{
        kfree(me);
}

static void vrf_map_elem_init(struct vrf_map_elem *me, int table_id,
                              int ifindex, int users)
{
        me->table_id = table_id;
        me->ifindex = ifindex;
        me->users = users;
        INIT_LIST_HEAD(&me->vrf_list);
}

static struct vrf_map_elem *vrf_map_lookup_elem(struct vrf_map *vmap,
                                                u32 table_id)
{
        struct vrf_map_elem *me;
        u32 key;

        key = jhash_1word(table_id, HASH_INITVAL);
        hash_for_each_possible(vmap->ht, me, hnode, key) {
                if (me->table_id == table_id)
                        return me;
        }

        return NULL;
}

static void vrf_map_add_elem(struct vrf_map *vmap, struct vrf_map_elem *me)
{
        u32 table_id = me->table_id;
        u32 key;

        key = jhash_1word(table_id, HASH_INITVAL);
        hash_add(vmap->ht, &me->hnode, key);
}

static void vrf_map_del_elem(struct vrf_map_elem *me)
{
        hash_del(&me->hnode);
}

static void vrf_map_lock(struct vrf_map *vmap) __acquires(&vmap->vmap_lock)
{
        spin_lock(&vmap->vmap_lock);
}

static void vrf_map_unlock(struct vrf_map *vmap) __releases(&vmap->vmap_lock)
{
        spin_unlock(&vmap->vmap_lock);
}

/* called with rtnl lock held */
static int
vrf_map_register_dev(struct net_device *dev, struct netlink_ext_ack *extack)
{
        struct vrf_map *vmap = netns_vrf_map_by_dev(dev);
        struct net_vrf *vrf = netdev_priv(dev);
        struct vrf_map_elem *new_me, *me;
        u32 table_id = vrf->tb_id;
        bool free_new_me = false;
        int users;
        int res;

        /* we pre-allocate elements used in the spin-locked section (so that we
         * keep the spinlock as short as possible).
         */
        new_me = vrf_map_elem_alloc(GFP_KERNEL);
        if (!new_me)
                return -ENOMEM;

        vrf_map_elem_init(new_me, table_id, dev->ifindex, 0);

        vrf_map_lock(vmap);

        me = vrf_map_lookup_elem(vmap, table_id);
        if (!me) {
                me = new_me;
                vrf_map_add_elem(vmap, me);
                goto link_vrf;
        }

        /* we already have an entry in the vrf_map, so it means there is (at
         * least) a vrf registered on the specific table.
         */
        free_new_me = true;
        if (vmap->strict_mode) {
                /* vrfs cannot share the same table */
                NL_SET_ERR_MSG(extack, "Table is used by another VRF");
                res = -EBUSY;
                goto unlock;
        }

link_vrf:
        users = ++me->users;
        if (users == 2)
                ++vmap->shared_tables;

        list_add(&vrf->me_list, &me->vrf_list);

        res = 0;

unlock:
        vrf_map_unlock(vmap);

        /* clean-up, if needed */
        if (free_new_me)
                vrf_map_elem_free(new_me);

        return res;
}

/* called with rtnl lock held */
static void vrf_map_unregister_dev(struct net_device *dev)
{
        struct vrf_map *vmap = netns_vrf_map_by_dev(dev);
        struct net_vrf *vrf = netdev_priv(dev);
        u32 table_id = vrf->tb_id;
        struct vrf_map_elem *me;
        int users;

        vrf_map_lock(vmap);

        me = vrf_map_lookup_elem(vmap, table_id);
        if (!me)
                goto unlock;

        list_del(&vrf->me_list);

        users = --me->users;
        if (users == 1) {
                --vmap->shared_tables;
        } else if (users == 0) {
                vrf_map_del_elem(me);

                /* no one will refer to this element anymore */
                vrf_map_elem_free(me);
        }

unlock:
        vrf_map_unlock(vmap);
}

/* return the vrf device index associated with the table_id */
static int vrf_ifindex_lookup_by_table_id(struct net *net, u32 table_id)
{
        struct vrf_map *vmap = netns_vrf_map(net);
        struct vrf_map_elem *me;
        int ifindex;

        vrf_map_lock(vmap);

        if (!vmap->strict_mode) {
                ifindex = -EPERM;
                goto unlock;
        }

        me = vrf_map_lookup_elem(vmap, table_id);
        if (!me) {
                ifindex = -ENODEV;
                goto unlock;
        }

        ifindex = vrf_map_elem_get_vrf_ifindex(me);

unlock:
        vrf_map_unlock(vmap);

        return ifindex;
}

/* by default VRF devices do not have a qdisc and are expected
 * to be created with only a single queue.
 */
static bool qdisc_tx_is_default(const struct net_device *dev)
{
        struct netdev_queue *txq;

        if (dev->num_tx_queues > 1)
                return false;

        txq = netdev_get_tx_queue(dev, 0);

        return qdisc_txq_has_no_queue(txq);
}

/* Local traffic destined to local address. Reinsert the packet to rx
 * path, similar to loopback handling.
 */
static int vrf_local_xmit(struct sk_buff *skb, struct net_device *dev,
                          struct dst_entry *dst)
{
        unsigned int len = skb->len;

        skb_orphan(skb);

        skb_dst_set(skb, dst);

        /* set pkt_type to avoid skb hitting packet taps twice -
         * once on Tx and again in Rx processing
         */
        skb->pkt_type = PACKET_LOOPBACK;

        skb->protocol = eth_type_trans(skb, dev);

        if (likely(__netif_rx(skb) == NET_RX_SUCCESS))
                dev_dstats_rx_add(dev, len);
        else
                dev_dstats_rx_dropped(dev);

        return NETDEV_TX_OK;
}

static void vrf_nf_set_untracked(struct sk_buff *skb)
{
        if (skb_get_nfct(skb) == 0)
                nf_ct_set(skb, NULL, IP_CT_UNTRACKED);
}

static void vrf_nf_reset_ct(struct sk_buff *skb)
{
        if (skb_get_nfct(skb) == IP_CT_UNTRACKED)
                nf_reset_ct(skb);
}

#if IS_ENABLED(CONFIG_IPV6)
static int vrf_ip6_local_out(struct net *net, struct sock *sk,
                             struct sk_buff *skb)
{
        int err;

        vrf_nf_reset_ct(skb);

        err = nf_hook(NFPROTO_IPV6, NF_INET_LOCAL_OUT, net,
                      sk, skb, NULL, skb_dst(skb)->dev, dst_output);

        if (likely(err == 1))
                err = dst_output(net, sk, skb);

        return err;
}

static netdev_tx_t vrf_process_v6_outbound(struct sk_buff *skb,
                                           struct net_device *dev)
{
        const struct ipv6hdr *iph;
        struct net *net = dev_net(skb->dev);
        struct flowi6 fl6;
        int ret = NET_XMIT_DROP;
        struct dst_entry *dst;
        struct dst_entry *dst_null = &net->ipv6.ip6_null_entry->dst;

        if (!pskb_may_pull(skb, ETH_HLEN + sizeof(struct ipv6hdr)))
                goto err;

        iph = ipv6_hdr(skb);

        memset(&fl6, 0, sizeof(fl6));
        /* needed to match OIF rule */
        fl6.flowi6_l3mdev = dev->ifindex;
        fl6.flowi6_iif = LOOPBACK_IFINDEX;
        fl6.daddr = iph->daddr;
        fl6.saddr = iph->saddr;
        fl6.flowlabel = ip6_flowinfo(iph);
        fl6.flowi6_mark = skb->mark;
        fl6.flowi6_proto = iph->nexthdr;

        dst = ip6_dst_lookup_flow(net, NULL, &fl6, NULL);
        if (IS_ERR(dst) || dst == dst_null)
                goto err;

        skb_dst_drop(skb);

        /* if dst.dev is the VRF device again this is locally originated traffic
         * destined to a local address. Short circuit to Rx path.
         */
        if (dst->dev == dev)
                return vrf_local_xmit(skb, dev, dst);

        skb_dst_set(skb, dst);

        /* strip the ethernet header added for pass through VRF device */
        __skb_pull(skb, skb_network_offset(skb));

        memset(IP6CB(skb), 0, sizeof(*IP6CB(skb)));
        ret = vrf_ip6_local_out(net, skb->sk, skb);
        if (unlikely(net_xmit_eval(ret)))
                dev->stats.tx_errors++;
        else
                ret = NET_XMIT_SUCCESS;

        return ret;
err:
        vrf_tx_error(dev, skb);
        return NET_XMIT_DROP;
}
#else
static netdev_tx_t vrf_process_v6_outbound(struct sk_buff *skb,
                                           struct net_device *dev)
{
        vrf_tx_error(dev, skb);
        return NET_XMIT_DROP;
}
#endif

/* based on ip_local_out; can't use it b/c the dst is switched pointing to us */
static int vrf_ip_local_out(struct net *net, struct sock *sk,
                            struct sk_buff *skb)
{
        int err;

        vrf_nf_reset_ct(skb);

        err = nf_hook(NFPROTO_IPV4, NF_INET_LOCAL_OUT, net, sk,
                      skb, NULL, skb_dst(skb)->dev, dst_output);
        if (likely(err == 1))
                err = dst_output(net, sk, skb);

        return err;
}

static netdev_tx_t vrf_process_v4_outbound(struct sk_buff *skb,
                                           struct net_device *vrf_dev)
{
        struct iphdr *ip4h;
        int ret = NET_XMIT_DROP;
        struct flowi4 fl4;
        struct net *net = dev_net(vrf_dev);
        struct rtable *rt;

        if (!pskb_may_pull(skb, ETH_HLEN + sizeof(struct iphdr)))
                goto err;

        ip4h = ip_hdr(skb);

        memset(&fl4, 0, sizeof(fl4));
        /* needed to match OIF rule */
        fl4.flowi4_l3mdev = vrf_dev->ifindex;
        fl4.flowi4_iif = LOOPBACK_IFINDEX;
        fl4.flowi4_dscp = ip4h_dscp(ip4h);
        fl4.flowi4_flags = FLOWI_FLAG_ANYSRC;
        fl4.flowi4_proto = ip4h->protocol;
        fl4.daddr = ip4h->daddr;
        fl4.saddr = ip4h->saddr;

        rt = ip_route_output_flow(net, &fl4, NULL);
        if (IS_ERR(rt))
                goto err;

        skb_dst_drop(skb);

        /* if dst.dev is the VRF device again this is locally originated traffic
         * destined to a local address. Short circuit to Rx path.
         */
        if (rt->dst.dev == vrf_dev)
                return vrf_local_xmit(skb, vrf_dev, &rt->dst);

        skb_dst_set(skb, &rt->dst);

        /* strip the ethernet header added for pass through VRF device */
        __skb_pull(skb, skb_network_offset(skb));

        if (!ip4h->saddr) {
                ip4h->saddr = inet_select_addr(skb_dst(skb)->dev, 0,
                                               RT_SCOPE_LINK);
        }

        memset(IPCB(skb), 0, sizeof(*IPCB(skb)));
        ret = vrf_ip_local_out(dev_net(skb_dst(skb)->dev), skb->sk, skb);
        if (unlikely(net_xmit_eval(ret)))
                vrf_dev->stats.tx_errors++;
        else
                ret = NET_XMIT_SUCCESS;

out:
        return ret;
err:
        vrf_tx_error(vrf_dev, skb);
        goto out;
}

static netdev_tx_t is_ip_tx_frame(struct sk_buff *skb, struct net_device *dev)
{
        switch (skb->protocol) {
        case htons(ETH_P_IP):
                return vrf_process_v4_outbound(skb, dev);
        case htons(ETH_P_IPV6):
                return vrf_process_v6_outbound(skb, dev);
        default:
                vrf_tx_error(dev, skb);
                return NET_XMIT_DROP;
        }
}

static netdev_tx_t vrf_xmit(struct sk_buff *skb, struct net_device *dev)
{
        unsigned int len = skb->len;
        netdev_tx_t ret;

        ret = is_ip_tx_frame(skb, dev);
        if (likely(ret == NET_XMIT_SUCCESS || ret == NET_XMIT_CN))
                dev_dstats_tx_add(dev, len);
        else
                dev_dstats_tx_dropped(dev);

        return ret;
}

static void vrf_finish_direct(struct sk_buff *skb)
{
        struct net_device *vrf_dev = skb->dev;

        if (!list_empty(&vrf_dev->ptype_all) &&
            likely(skb_headroom(skb) >= ETH_HLEN)) {
                struct ethhdr *eth = skb_push(skb, ETH_HLEN);

                ether_addr_copy(eth->h_source, vrf_dev->dev_addr);
                eth_zero_addr(eth->h_dest);
                eth->h_proto = skb->protocol;

                rcu_read_lock_bh();
                dev_queue_xmit_nit(skb, vrf_dev);
                rcu_read_unlock_bh();

                skb_pull(skb, ETH_HLEN);
        }

        vrf_nf_reset_ct(skb);
}

#if IS_ENABLED(CONFIG_IPV6)
/* modelled after ip6_finish_output2 */
static int vrf_finish_output6(struct net *net, struct sock *sk,
                              struct sk_buff *skb)
{
        struct dst_entry *dst = skb_dst(skb);
        struct net_device *dev = dst->dev;
        const struct in6_addr *nexthop;
        struct neighbour *neigh;
        int ret;

        vrf_nf_reset_ct(skb);

        skb->protocol = htons(ETH_P_IPV6);
        skb->dev = dev;

        rcu_read_lock();
        nexthop = rt6_nexthop(dst_rt6_info(dst), &ipv6_hdr(skb)->daddr);
        neigh = __ipv6_neigh_lookup_noref(dst->dev, nexthop);
        if (unlikely(!neigh))
                neigh = __neigh_create(&nd_tbl, nexthop, dst->dev, false);
        if (!IS_ERR(neigh)) {
                sock_confirm_neigh(skb, neigh);
                ret = neigh_output(neigh, skb, false);
                rcu_read_unlock();
                return ret;
        }
        rcu_read_unlock();

        IP6_INC_STATS(dev_net(dst->dev),
                      ip6_dst_idev(dst), IPSTATS_MIB_OUTNOROUTES);
        kfree_skb(skb);
        return -EINVAL;
}

/* modelled after ip6_output */
static int vrf_output6(struct net *net, struct sock *sk, struct sk_buff *skb)
{
        return NF_HOOK_COND(NFPROTO_IPV6, NF_INET_POST_ROUTING,
                            net, sk, skb, NULL, skb_dst(skb)->dev,
                            vrf_finish_output6,
                            !(IP6CB(skb)->flags & IP6SKB_REROUTED));
}

/* set dst on skb to send packet to us via dev_xmit path. Allows
 * packet to go through device based features such as qdisc, netfilter
 * hooks and packet sockets with skb->dev set to vrf device.
 */
static struct sk_buff *vrf_ip6_out_redirect(struct net_device *vrf_dev,
                                            struct sk_buff *skb)
{
        struct net_vrf *vrf = netdev_priv(vrf_dev);
        struct dst_entry *dst = NULL;
        struct rt6_info *rt6;

        rcu_read_lock();

        rt6 = rcu_dereference(vrf->rt6);
        if (likely(rt6)) {
                dst = &rt6->dst;
                dst_hold(dst);
        }

        rcu_read_unlock();

        if (unlikely(!dst)) {
                vrf_tx_error(vrf_dev, skb);
                return NULL;
        }

        skb_dst_drop(skb);
        skb_dst_set(skb, dst);

        return skb;
}

static int vrf_output6_direct_finish(struct net *net, struct sock *sk,
                                     struct sk_buff *skb)
{
        vrf_finish_direct(skb);

        return vrf_ip6_local_out(net, sk, skb);
}

static int vrf_output6_direct(struct net *net, struct sock *sk,
                              struct sk_buff *skb)
{
        int err = 1;

        skb->protocol = htons(ETH_P_IPV6);

        if (!(IPCB(skb)->flags & IPSKB_REROUTED))
                err = nf_hook(NFPROTO_IPV6, NF_INET_POST_ROUTING, net, sk, skb,
                              NULL, skb->dev, vrf_output6_direct_finish);

        if (likely(err == 1))
                vrf_finish_direct(skb);

        return err;
}

static int vrf_ip6_out_direct_finish(struct net *net, struct sock *sk,
                                     struct sk_buff *skb)
{
        int err;

        err = vrf_output6_direct(net, sk, skb);
        if (likely(err == 1))
                err = vrf_ip6_local_out(net, sk, skb);

        return err;
}

static struct sk_buff *vrf_ip6_out_direct(struct net_device *vrf_dev,
                                          struct sock *sk,
                                          struct sk_buff *skb)
{
        struct net *net = dev_net(vrf_dev);
        int err;

        skb->dev = vrf_dev;

        err = nf_hook(NFPROTO_IPV6, NF_INET_LOCAL_OUT, net, sk,
                      skb, NULL, vrf_dev, vrf_ip6_out_direct_finish);

        if (likely(err == 1))
                err = vrf_output6_direct(net, sk, skb);

        if (likely(err == 1))
                return skb;

        return NULL;
}

static struct sk_buff *vrf_ip6_out(struct net_device *vrf_dev,
                                   struct sock *sk,
                                   struct sk_buff *skb)
{
        /* don't divert link scope packets */
        if (rt6_need_strict(&ipv6_hdr(skb)->daddr))
                return skb;

        vrf_nf_set_untracked(skb);

        if (qdisc_tx_is_default(vrf_dev) ||
            IP6CB(skb)->flags & IP6SKB_XFRM_TRANSFORMED)
                return vrf_ip6_out_direct(vrf_dev, sk, skb);

        return vrf_ip6_out_redirect(vrf_dev, skb);
}

/* holding rtnl */
static void vrf_rt6_release(struct net_device *dev, struct net_vrf *vrf)
{
        struct rt6_info *rt6 = rtnl_dereference(vrf->rt6);
        struct net *net = dev_net(dev);
        struct dst_entry *dst;

        RCU_INIT_POINTER(vrf->rt6, NULL);
        synchronize_rcu();

        /* move dev in dst's to loopback so this VRF device can be deleted
         * - based on dst_ifdown
         */
        if (rt6) {
                dst = &rt6->dst;
                netdev_ref_replace(dst->dev, net->loopback_dev,
                                   &dst->dev_tracker, GFP_KERNEL);
                dst->dev = net->loopback_dev;
                dst_release(dst);
        }
}

static int vrf_rt6_create(struct net_device *dev)
{
        int flags = DST_NOPOLICY | DST_NOXFRM;
        struct net_vrf *vrf = netdev_priv(dev);
        struct net *net = dev_net(dev);
        struct rt6_info *rt6;
        int rc = -ENOMEM;

        /* IPv6 can be CONFIG enabled and then disabled runtime */
        if (!ipv6_mod_enabled())
                return 0;

        vrf->fib6_table = fib6_new_table(net, vrf->tb_id);
        if (!vrf->fib6_table)
                goto out;

        /* create a dst for routing packets out a VRF device */
        rt6 = ip6_dst_alloc(net, dev, flags);
        if (!rt6)
                goto out;

        rt6->dst.output = vrf_output6;

        rcu_assign_pointer(vrf->rt6, rt6);

        rc = 0;
out:
        return rc;
}
#else
static struct sk_buff *vrf_ip6_out(struct net_device *vrf_dev,
                                   struct sock *sk,
                                   struct sk_buff *skb)
{
        return skb;
}

static void vrf_rt6_release(struct net_device *dev, struct net_vrf *vrf)
{
}

static int vrf_rt6_create(struct net_device *dev)
{
        return 0;
}
#endif

/* modelled after ip_finish_output2 */
static int vrf_finish_output(struct net *net, struct sock *sk, struct sk_buff *skb)
{
        struct dst_entry *dst = skb_dst(skb);
        struct rtable *rt = dst_rtable(dst);
        struct net_device *dev = dst->dev;
        unsigned int hh_len = LL_RESERVED_SPACE(dev);
        struct neighbour *neigh;
        bool is_v6gw = false;

        vrf_nf_reset_ct(skb);

        /* Be paranoid, rather than too clever. */
        if (unlikely(skb_headroom(skb) < hh_len && dev->header_ops)) {
                skb = skb_expand_head(skb, hh_len);
                if (!skb) {
                        dev->stats.tx_errors++;
                        return -ENOMEM;
                }
        }

        rcu_read_lock();

        neigh = ip_neigh_for_gw(rt, skb, &is_v6gw);
        if (!IS_ERR(neigh)) {
                int ret;

                sock_confirm_neigh(skb, neigh);
                /* if crossing protocols, can not use the cached header */
                ret = neigh_output(neigh, skb, is_v6gw);
                rcu_read_unlock();
                return ret;
        }

        rcu_read_unlock();
        vrf_tx_error(skb->dev, skb);
        return -EINVAL;
}

static int vrf_output(struct net *net, struct sock *sk, struct sk_buff *skb)
{
        struct net_device *dev = skb_dst(skb)->dev;

        IP_UPD_PO_STATS(net, IPSTATS_MIB_OUT, skb->len);

        skb->dev = dev;
        skb->protocol = htons(ETH_P_IP);

        return NF_HOOK_COND(NFPROTO_IPV4, NF_INET_POST_ROUTING,
                            net, sk, skb, NULL, dev,
                            vrf_finish_output,
                            !(IPCB(skb)->flags & IPSKB_REROUTED));
}

/* set dst on skb to send packet to us via dev_xmit path. Allows
 * packet to go through device based features such as qdisc, netfilter
 * hooks and packet sockets with skb->dev set to vrf device.
 */
static struct sk_buff *vrf_ip_out_redirect(struct net_device *vrf_dev,
                                           struct sk_buff *skb)
{
        struct net_vrf *vrf = netdev_priv(vrf_dev);
        struct dst_entry *dst = NULL;
        struct rtable *rth;

        rcu_read_lock();

        rth = rcu_dereference(vrf->rth);
        if (likely(rth)) {
                dst = &rth->dst;
                dst_hold(dst);
        }

        rcu_read_unlock();

        if (unlikely(!dst)) {
                vrf_tx_error(vrf_dev, skb);
                return NULL;
        }

        skb_dst_drop(skb);
        skb_dst_set(skb, dst);

        return skb;
}

static int vrf_output_direct_finish(struct net *net, struct sock *sk,
                                    struct sk_buff *skb)
{
        vrf_finish_direct(skb);

        return vrf_ip_local_out(net, sk, skb);
}

static int vrf_output_direct(struct net *net, struct sock *sk,
                             struct sk_buff *skb)
{
        int err = 1;

        skb->protocol = htons(ETH_P_IP);

        if (!(IPCB(skb)->flags & IPSKB_REROUTED))
                err = nf_hook(NFPROTO_IPV4, NF_INET_POST_ROUTING, net, sk, skb,
                              NULL, skb->dev, vrf_output_direct_finish);

        if (likely(err == 1))
                vrf_finish_direct(skb);

        return err;
}

static int vrf_ip_out_direct_finish(struct net *net, struct sock *sk,
                                    struct sk_buff *skb)
{
        int err;

        err = vrf_output_direct(net, sk, skb);
        if (likely(err == 1))
                err = vrf_ip_local_out(net, sk, skb);

        return err;
}

static struct sk_buff *vrf_ip_out_direct(struct net_device *vrf_dev,
                                         struct sock *sk,
                                         struct sk_buff *skb)
{
        struct net *net = dev_net(vrf_dev);
        int err;

        skb->dev = vrf_dev;

        err = nf_hook(NFPROTO_IPV4, NF_INET_LOCAL_OUT, net, sk,
                      skb, NULL, vrf_dev, vrf_ip_out_direct_finish);

        if (likely(err == 1))
                err = vrf_output_direct(net, sk, skb);

        if (likely(err == 1))
                return skb;

        return NULL;
}

static struct sk_buff *vrf_ip_out(struct net_device *vrf_dev,
                                  struct sock *sk,
                                  struct sk_buff *skb)
{
        /* don't divert multicast or local broadcast */
        if (ipv4_is_multicast(ip_hdr(skb)->daddr) ||
            ipv4_is_lbcast(ip_hdr(skb)->daddr))
                return skb;

        vrf_nf_set_untracked(skb);

        if (qdisc_tx_is_default(vrf_dev) ||
            IPCB(skb)->flags & IPSKB_XFRM_TRANSFORMED)
                return vrf_ip_out_direct(vrf_dev, sk, skb);

        return vrf_ip_out_redirect(vrf_dev, skb);
}

/* called with rcu lock held */
static struct sk_buff *vrf_l3_out(struct net_device *vrf_dev,
                                  struct sock *sk,
                                  struct sk_buff *skb,
                                  u16 proto)
{
        switch (proto) {
        case AF_INET:
                return vrf_ip_out(vrf_dev, sk, skb);
        case AF_INET6:
                return vrf_ip6_out(vrf_dev, sk, skb);
        }

        return skb;
}

/* holding rtnl */
static void vrf_rtable_release(struct net_device *dev, struct net_vrf *vrf)
{
        struct rtable *rth = rtnl_dereference(vrf->rth);
        struct net *net = dev_net(dev);
        struct dst_entry *dst;

        RCU_INIT_POINTER(vrf->rth, NULL);
        synchronize_rcu();

        /* move dev in dst's to loopback so this VRF device can be deleted
         * - based on dst_ifdown
         */
        if (rth) {
                dst = &rth->dst;
                netdev_ref_replace(dst->dev, net->loopback_dev,
                                   &dst->dev_tracker, GFP_KERNEL);
                dst->dev = net->loopback_dev;
                dst_release(dst);
        }
}

static int vrf_rtable_create(struct net_device *dev)
{
        struct net_vrf *vrf = netdev_priv(dev);
        struct rtable *rth;

        if (!fib_new_table(dev_net(dev), vrf->tb_id))
                return -ENOMEM;

        /* create a dst for routing packets out through a VRF device */
        rth = rt_dst_alloc(dev, 0, RTN_UNICAST, 1);
        if (!rth)
                return -ENOMEM;

        rth->dst.output = vrf_output;

        rcu_assign_pointer(vrf->rth, rth);

        return 0;
}

/**************************** device handling ********************/

/* cycle interface to flush neighbor cache and move routes across tables */
static void cycle_netdev(struct net_device *dev,
                         struct netlink_ext_ack *extack)
{
        unsigned int flags = dev->flags;
        int ret;

        if (!netif_running(dev))
                return;

        ret = dev_change_flags(dev, flags & ~IFF_UP, extack);
        if (ret >= 0)
                ret = dev_change_flags(dev, flags, extack);

        if (ret < 0) {
                netdev_err(dev,
                           "Failed to cycle device %s; route tables might be wrong!\n",
                           dev->name);
        }
}

static int do_vrf_add_slave(struct net_device *dev, struct net_device *port_dev,
                            struct netlink_ext_ack *extack)
{
        int ret;

        /* do not allow loopback device to be enslaved to a VRF.
         * The vrf device acts as the loopback for the vrf.
         */
        if (port_dev == dev_net(dev)->loopback_dev) {
                NL_SET_ERR_MSG(extack,
                               "Can not enslave loopback device to a VRF");
                return -EOPNOTSUPP;
        }

        port_dev->priv_flags |= IFF_L3MDEV_SLAVE;
        ret = netdev_master_upper_dev_link(port_dev, dev, NULL, NULL, extack);
        if (ret < 0)
                goto err;

        cycle_netdev(port_dev, extack);

        return 0;

err:
        port_dev->priv_flags &= ~IFF_L3MDEV_SLAVE;
        return ret;
}

static int vrf_add_slave(struct net_device *dev, struct net_device *port_dev,
                         struct netlink_ext_ack *extack)
{
        if (netif_is_l3_master(port_dev)) {
                NL_SET_ERR_MSG(extack,
                               "Can not enslave an L3 master device to a VRF");
                return -EINVAL;
        }

        if (netif_is_l3_slave(port_dev))
                return -EINVAL;

        return do_vrf_add_slave(dev, port_dev, extack);
}

/* inverse of do_vrf_add_slave */
static int do_vrf_del_slave(struct net_device *dev, struct net_device *port_dev)
{
        netdev_upper_dev_unlink(port_dev, dev);
        port_dev->priv_flags &= ~IFF_L3MDEV_SLAVE;

        cycle_netdev(port_dev, NULL);

        return 0;
}

static int vrf_del_slave(struct net_device *dev, struct net_device *port_dev)
{
        return do_vrf_del_slave(dev, port_dev);
}

static void vrf_dev_uninit(struct net_device *dev)
{
        struct net_vrf *vrf = netdev_priv(dev);

        vrf_rtable_release(dev, vrf);
        vrf_rt6_release(dev, vrf);
}

static int vrf_dev_init(struct net_device *dev)
{
        struct net_vrf *vrf = netdev_priv(dev);

        /* create the default dst which points back to us */
        if (vrf_rtable_create(dev) != 0)
                goto out_nomem;

        if (vrf_rt6_create(dev) != 0)
                goto out_rth;

        dev->flags = IFF_MASTER | IFF_NOARP;

        /* similarly, oper state is irrelevant; set to up to avoid confusion */
        dev->operstate = IF_OPER_UP;
        netdev_lockdep_set_classes(dev);
        return 0;

out_rth:
        vrf_rtable_release(dev, vrf);
out_nomem:
        return -ENOMEM;
}

static const struct net_device_ops vrf_netdev_ops = {
        .ndo_init               = vrf_dev_init,
        .ndo_uninit             = vrf_dev_uninit,
        .ndo_start_xmit         = vrf_xmit,
        .ndo_set_mac_address    = eth_mac_addr,
        .ndo_add_slave          = vrf_add_slave,
        .ndo_del_slave          = vrf_del_slave,
};

static u32 vrf_fib_table(const struct net_device *dev)
{
        struct net_vrf *vrf = netdev_priv(dev);

        return vrf->tb_id;
}

static int vrf_rcv_finish(struct net *net, struct sock *sk, struct sk_buff *skb)
{
        kfree_skb(skb);
        return 0;
}

static struct sk_buff *vrf_rcv_nfhook(u8 pf, unsigned int hook,
                                      struct sk_buff *skb,
                                      struct net_device *dev)
{
        struct net *net = dev_net(dev);

        if (nf_hook(pf, hook, net, NULL, skb, dev, NULL, vrf_rcv_finish) != 1)
                skb = NULL;    /* kfree_skb(skb) handled by nf code */

        return skb;
}

static int vrf_prepare_mac_header(struct sk_buff *skb,
                                  struct net_device *vrf_dev, u16 proto)
{
        struct ethhdr *eth;
        int err;

        /* in general, we do not know if there is enough space in the head of
         * the packet for hosting the mac header.
         */
        err = skb_cow_head(skb, LL_RESERVED_SPACE(vrf_dev));
        if (unlikely(err))
                /* no space in the skb head */
                return -ENOBUFS;

        __skb_push(skb, ETH_HLEN);
        eth = (struct ethhdr *)skb->data;

        skb_reset_mac_header(skb);
        skb_reset_mac_len(skb);

        /* we set the ethernet destination and the source addresses to the
         * address of the VRF device.
         */
        ether_addr_copy(eth->h_dest, vrf_dev->dev_addr);
        ether_addr_copy(eth->h_source, vrf_dev->dev_addr);
        eth->h_proto = htons(proto);

        /* the destination address of the Ethernet frame corresponds to the
         * address set on the VRF interface; therefore, the packet is intended
         * to be processed locally.
         */
        skb->protocol = eth->h_proto;
        skb->pkt_type = PACKET_HOST;

        skb_postpush_rcsum(skb, skb->data, ETH_HLEN);

        skb_pull_inline(skb, ETH_HLEN);

        return 0;
}

/* prepare and add the mac header to the packet if it was not set previously.
 * In this way, packet sniffers such as tcpdump can parse the packet correctly.
 * If the mac header was already set, the original mac header is left
 * untouched and the function returns immediately.
 */
static int vrf_add_mac_header_if_unset(struct sk_buff *skb,
                                       struct net_device *vrf_dev,
                                       u16 proto, struct net_device *orig_dev)
{
        if (skb_mac_header_was_set(skb) && dev_has_header(orig_dev))
                return 0;

        return vrf_prepare_mac_header(skb, vrf_dev, proto);
}

#if IS_ENABLED(CONFIG_IPV6)
/* neighbor handling is done with actual device; do not want
 * to flip skb->dev for those ndisc packets. This really fails
 * for multiple next protocols (e.g., NEXTHDR_HOP). But it is
 * a start.
 */
static bool ipv6_ndisc_frame(const struct sk_buff *skb)
{
        const struct ipv6hdr *iph = ipv6_hdr(skb);
        bool rc = false;

        if (iph->nexthdr == NEXTHDR_ICMP) {
                const struct icmp6hdr *icmph;
                struct icmp6hdr _icmph;

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

                switch (icmph->icmp6_type) {
                case NDISC_ROUTER_SOLICITATION:
                case NDISC_ROUTER_ADVERTISEMENT:
                case NDISC_NEIGHBOUR_SOLICITATION:
                case NDISC_NEIGHBOUR_ADVERTISEMENT:
                case NDISC_REDIRECT:
                        rc = true;
                        break;
                }
        }

out:
        return rc;
}

static struct rt6_info *vrf_ip6_route_lookup(struct net *net,
                                             const struct net_device *dev,
                                             struct flowi6 *fl6,
                                             int ifindex,
                                             const struct sk_buff *skb,
                                             int flags)
{
        struct net_vrf *vrf = netdev_priv(dev);

        return ip6_pol_route(net, vrf->fib6_table, ifindex, fl6, skb, flags);
}

static void vrf_ip6_input_dst(struct sk_buff *skb, struct net_device *vrf_dev,
                              int ifindex)
{
        const struct ipv6hdr *iph = ipv6_hdr(skb);
        struct flowi6 fl6 = {
                .flowi6_iif     = ifindex,
                .flowi6_mark    = skb->mark,
                .flowi6_proto   = iph->nexthdr,
                .daddr          = iph->daddr,
                .saddr          = iph->saddr,
                .flowlabel      = ip6_flowinfo(iph),
        };
        struct net *net = dev_net(vrf_dev);
        struct rt6_info *rt6;

        skb_dst_drop(skb);

        rt6 = vrf_ip6_route_lookup(net, vrf_dev, &fl6, ifindex, skb,
                                   RT6_LOOKUP_F_HAS_SADDR | RT6_LOOKUP_F_IFACE);
        if (unlikely(!rt6))
                return;

        if (unlikely(&rt6->dst == &net->ipv6.ip6_null_entry->dst))
                return;

        skb_dst_set(skb, &rt6->dst);
}

static struct sk_buff *vrf_ip6_rcv(struct net_device *vrf_dev,
                                   struct sk_buff *skb)
{
        int orig_iif = skb->skb_iif;
        bool need_strict = rt6_need_strict(&ipv6_hdr(skb)->daddr);
        bool is_ndisc = ipv6_ndisc_frame(skb);

        /* loopback, multicast & non-ND link-local traffic; do not push through
         * packet taps again. Reset pkt_type for upper layers to process skb.
         * For non-loopback strict packets, determine the dst using the original
         * ifindex.
         */
        if (skb->pkt_type == PACKET_LOOPBACK || (need_strict && !is_ndisc)) {
                skb->dev = vrf_dev;
                skb->skb_iif = vrf_dev->ifindex;
                IP6CB(skb)->flags |= IP6SKB_L3SLAVE;

                if (skb->pkt_type == PACKET_LOOPBACK)
                        skb->pkt_type = PACKET_HOST;
                else
                        vrf_ip6_input_dst(skb, vrf_dev, orig_iif);

                goto out;
        }

        /* if packet is NDISC then keep the ingress interface */
        if (!is_ndisc) {
                struct net_device *orig_dev = skb->dev;

                dev_dstats_rx_add(vrf_dev, skb->len);
                skb->dev = vrf_dev;
                skb->skb_iif = vrf_dev->ifindex;

                if (!list_empty(&vrf_dev->ptype_all)) {
                        int err;

                        err = vrf_add_mac_header_if_unset(skb, vrf_dev,
                                                          ETH_P_IPV6,
                                                          orig_dev);
                        if (likely(!err)) {
                                skb_push(skb, skb->mac_len);
                                dev_queue_xmit_nit(skb, vrf_dev);
                                skb_pull(skb, skb->mac_len);
                        }
                }

                IP6CB(skb)->flags |= IP6SKB_L3SLAVE;
        }

        if (need_strict)
                vrf_ip6_input_dst(skb, vrf_dev, orig_iif);

        skb = vrf_rcv_nfhook(NFPROTO_IPV6, NF_INET_PRE_ROUTING, skb, vrf_dev);
out:
        return skb;
}

#else
static struct sk_buff *vrf_ip6_rcv(struct net_device *vrf_dev,
                                   struct sk_buff *skb)
{
        return skb;
}
#endif

static struct sk_buff *vrf_ip_rcv(struct net_device *vrf_dev,
                                  struct sk_buff *skb)
{
        struct net_device *orig_dev = skb->dev;

        skb->dev = vrf_dev;
        skb->skb_iif = vrf_dev->ifindex;
        IPCB(skb)->flags |= IPSKB_L3SLAVE;

        if (ipv4_is_multicast(ip_hdr(skb)->daddr))
                goto out;

        /* loopback traffic; do not push through packet taps again.
         * Reset pkt_type for upper layers to process skb
         */
        if (skb->pkt_type == PACKET_LOOPBACK) {
                skb->pkt_type = PACKET_HOST;
                goto out;
        }

        dev_dstats_rx_add(vrf_dev, skb->len);

        if (!list_empty(&vrf_dev->ptype_all)) {
                int err;

                err = vrf_add_mac_header_if_unset(skb, vrf_dev, ETH_P_IP,
                                                  orig_dev);
                if (likely(!err)) {
                        skb_push(skb, skb->mac_len);
                        dev_queue_xmit_nit(skb, vrf_dev);
                        skb_pull(skb, skb->mac_len);
                }
        }

        skb = vrf_rcv_nfhook(NFPROTO_IPV4, NF_INET_PRE_ROUTING, skb, vrf_dev);
out:
        return skb;
}

/* called with rcu lock held */
static struct sk_buff *vrf_l3_rcv(struct net_device *vrf_dev,
                                  struct sk_buff *skb,
                                  u16 proto)
{
        switch (proto) {
        case AF_INET:
                return vrf_ip_rcv(vrf_dev, skb);
        case AF_INET6:
                return vrf_ip6_rcv(vrf_dev, skb);
        }

        return skb;
}

#if IS_ENABLED(CONFIG_IPV6)
/* send to link-local or multicast address via interface enslaved to
 * VRF device. Force lookup to VRF table without changing flow struct
 * Note: Caller to this function must hold rcu_read_lock() and no refcnt
 * is taken on the dst by this function.
 */
static struct dst_entry *vrf_link_scope_lookup(const struct net_device *dev,
                                              struct flowi6 *fl6)
{
        struct net *net = dev_net(dev);
        int flags = RT6_LOOKUP_F_IFACE | RT6_LOOKUP_F_DST_NOREF;
        struct dst_entry *dst = NULL;
        struct rt6_info *rt;

        /* VRF device does not have a link-local address and
         * sending packets to link-local or mcast addresses over
         * a VRF device does not make sense
         */
        if (fl6->flowi6_oif == dev->ifindex) {
                dst = &net->ipv6.ip6_null_entry->dst;
                return dst;
        }

        if (!ipv6_addr_any(&fl6->saddr))
                flags |= RT6_LOOKUP_F_HAS_SADDR;

        rt = vrf_ip6_route_lookup(net, dev, fl6, fl6->flowi6_oif, NULL, flags);
        if (rt)
                dst = &rt->dst;

        return dst;
}
#endif

static const struct l3mdev_ops vrf_l3mdev_ops = {
        .l3mdev_fib_table       = vrf_fib_table,
        .l3mdev_l3_rcv          = vrf_l3_rcv,
        .l3mdev_l3_out          = vrf_l3_out,
#if IS_ENABLED(CONFIG_IPV6)
        .l3mdev_link_scope_lookup = vrf_link_scope_lookup,
#endif
};

static void vrf_get_drvinfo(struct net_device *dev,
                            struct ethtool_drvinfo *info)
{
        strscpy(info->driver, DRV_NAME, sizeof(info->driver));
        strscpy(info->version, DRV_VERSION, sizeof(info->version));
}

static const struct ethtool_ops vrf_ethtool_ops = {
        .get_drvinfo    = vrf_get_drvinfo,
};

static inline size_t vrf_fib_rule_nl_size(void)
{
        size_t sz;

        sz  = NLMSG_ALIGN(sizeof(struct fib_rule_hdr));
        sz += nla_total_size(sizeof(u8));       /* FRA_L3MDEV */
        sz += nla_total_size(sizeof(u32));      /* FRA_PRIORITY */
        sz += nla_total_size(sizeof(u8));       /* FRA_PROTOCOL */

        return sz;
}

static int vrf_fib_rule(const struct net_device *dev, __u8 family, bool add_it)
{
        struct fib_rule_hdr *frh;
        struct nlmsghdr *nlh;
        struct sk_buff *skb;
        int err;

        if ((family == AF_INET6 || family == RTNL_FAMILY_IP6MR) &&
            !ipv6_mod_enabled())
                return 0;

        skb = nlmsg_new(vrf_fib_rule_nl_size(), GFP_KERNEL);
        if (!skb)
                return -ENOMEM;

        nlh = nlmsg_put(skb, 0, 0, 0, sizeof(*frh), 0);
        if (!nlh)
                goto nla_put_failure;

        /* rule only needs to appear once */
        nlh->nlmsg_flags |= NLM_F_EXCL;

        frh = nlmsg_data(nlh);
        memset(frh, 0, sizeof(*frh));
        frh->family = family;
        frh->action = FR_ACT_TO_TBL;

        if (nla_put_u8(skb, FRA_PROTOCOL, RTPROT_KERNEL))
                goto nla_put_failure;

        if (nla_put_u8(skb, FRA_L3MDEV, 1))
                goto nla_put_failure;

        if (nla_put_u32(skb, FRA_PRIORITY, FIB_RULE_PREF))
                goto nla_put_failure;

        nlmsg_end(skb, nlh);

        if (add_it) {
                err = fib_newrule(dev_net(dev), skb, nlh, NULL, true);
                if (err == -EEXIST)
                        err = 0;
        } else {
                err = fib_delrule(dev_net(dev), skb, nlh, NULL, true);
                if (err == -ENOENT)
                        err = 0;
        }
        nlmsg_free(skb);

        return err;

nla_put_failure:
        nlmsg_free(skb);

        return -EMSGSIZE;
}

static int vrf_add_fib_rules(const struct net_device *dev)
{
        int err;

        err = vrf_fib_rule(dev, AF_INET,  true);
        if (err < 0)
                goto out_err;

        err = vrf_fib_rule(dev, AF_INET6, true);
        if (err < 0)
                goto ipv6_err;

#if IS_ENABLED(CONFIG_IP_MROUTE_MULTIPLE_TABLES)
        err = vrf_fib_rule(dev, RTNL_FAMILY_IPMR, true);
        if (err < 0)
                goto ipmr_err;
#endif

#if IS_ENABLED(CONFIG_IPV6_MROUTE_MULTIPLE_TABLES)
        err = vrf_fib_rule(dev, RTNL_FAMILY_IP6MR, true);
        if (err < 0)
                goto ip6mr_err;
#endif

        return 0;

#if IS_ENABLED(CONFIG_IPV6_MROUTE_MULTIPLE_TABLES)
ip6mr_err:
        vrf_fib_rule(dev, RTNL_FAMILY_IPMR,  false);
#endif

#if IS_ENABLED(CONFIG_IP_MROUTE_MULTIPLE_TABLES)
ipmr_err:
        vrf_fib_rule(dev, AF_INET6,  false);
#endif

ipv6_err:
        vrf_fib_rule(dev, AF_INET,  false);

out_err:
        netdev_err(dev, "Failed to add FIB rules.\n");
        return err;
}

static void vrf_setup(struct net_device *dev)
{
        ether_setup(dev);

        /* Initialize the device structure. */
        dev->netdev_ops = &vrf_netdev_ops;
        dev->l3mdev_ops = &vrf_l3mdev_ops;
        dev->ethtool_ops = &vrf_ethtool_ops;
        dev->needs_free_netdev = true;

        /* Fill in device structure with ethernet-generic values. */
        eth_hw_addr_random(dev);

        /* don't acquire vrf device's netif_tx_lock when transmitting */
        dev->lltx = true;

        /* don't allow vrf devices to change network namespaces. */
        dev->netns_immutable = true;

        /* does not make sense for a VLAN to be added to a vrf device */
        dev->features   |= NETIF_F_VLAN_CHALLENGED;

        /* enable offload features */
        dev->features   |= NETIF_F_GSO_SOFTWARE;
        dev->features   |= NETIF_F_RXCSUM | NETIF_F_HW_CSUM | NETIF_F_SCTP_CRC;
        dev->features   |= NETIF_F_SG | NETIF_F_FRAGLIST | NETIF_F_HIGHDMA;

        dev->hw_features = dev->features;
        dev->hw_enc_features = dev->features;

        /* default to no qdisc; user can add if desired */
        dev->priv_flags |= IFF_NO_QUEUE;
        dev->priv_flags |= IFF_NO_RX_HANDLER;
        dev->priv_flags |= IFF_LIVE_ADDR_CHANGE;

        /* VRF devices do not care about MTU, but if the MTU is set
         * too low then the ipv4 and ipv6 protocols are disabled
         * which breaks networking.
         */
        dev->min_mtu = IPV6_MIN_MTU;
        dev->max_mtu = IP6_MAX_MTU;
        dev->mtu = dev->max_mtu;

        dev->pcpu_stat_type = NETDEV_PCPU_STAT_DSTATS;
}

static int vrf_validate(struct nlattr *tb[], struct nlattr *data[],
                        struct netlink_ext_ack *extack)
{
        if (tb[IFLA_ADDRESS]) {
                if (nla_len(tb[IFLA_ADDRESS]) != ETH_ALEN) {
                        NL_SET_ERR_MSG(extack, "Invalid hardware address");
                        return -EINVAL;
                }
                if (!is_valid_ether_addr(nla_data(tb[IFLA_ADDRESS]))) {
                        NL_SET_ERR_MSG(extack, "Invalid hardware address");
                        return -EADDRNOTAVAIL;
                }
        }
        return 0;
}

static void vrf_dellink(struct net_device *dev, struct list_head *head)
{
        struct net_device *port_dev;
        struct list_head *iter;

        netdev_for_each_lower_dev(dev, port_dev, iter)
                vrf_del_slave(dev, port_dev);

        vrf_map_unregister_dev(dev);

        unregister_netdevice_queue(dev, head);
}

static int vrf_newlink(struct net_device *dev,
                       struct rtnl_newlink_params *params,
                       struct netlink_ext_ack *extack)
{
        struct net_vrf *vrf = netdev_priv(dev);
        struct nlattr **data = params->data;
        struct netns_vrf *nn_vrf;
        bool *add_fib_rules;
        struct net *net;
        int err;

        if (!data || !data[IFLA_VRF_TABLE]) {
                NL_SET_ERR_MSG(extack, "VRF table id is missing");
                return -EINVAL;
        }

        vrf->tb_id = nla_get_u32(data[IFLA_VRF_TABLE]);
        if (vrf->tb_id == RT_TABLE_UNSPEC) {
                NL_SET_ERR_MSG_ATTR(extack, data[IFLA_VRF_TABLE],
                                    "Invalid VRF table id");
                return -EINVAL;
        }

        dev->priv_flags |= IFF_L3MDEV_MASTER;

        err = register_netdevice(dev);
        if (err)
                goto out;

        /* mapping between table_id and vrf;
         * note: such binding could not be done in the dev init function
         * because dev->ifindex id is not available yet.
         */
        vrf->ifindex = dev->ifindex;

        err = vrf_map_register_dev(dev, extack);
        if (err) {
                unregister_netdevice(dev);
                goto out;
        }

        net = dev_net(dev);
        nn_vrf = net_generic(net, vrf_net_id);

        add_fib_rules = &nn_vrf->add_fib_rules;
        if (*add_fib_rules) {
                err = vrf_add_fib_rules(dev);
                if (err) {
                        vrf_map_unregister_dev(dev);
                        unregister_netdevice(dev);
                        goto out;
                }
                *add_fib_rules = false;
        }

out:
        return err;
}

static size_t vrf_nl_getsize(const struct net_device *dev)
{
        return nla_total_size(sizeof(u32));  /* IFLA_VRF_TABLE */
}

static int vrf_fillinfo(struct sk_buff *skb,
                        const struct net_device *dev)
{
        struct net_vrf *vrf = netdev_priv(dev);

        return nla_put_u32(skb, IFLA_VRF_TABLE, vrf->tb_id);
}

static size_t vrf_get_slave_size(const struct net_device *bond_dev,
                                 const struct net_device *slave_dev)
{
        return nla_total_size(sizeof(u32));  /* IFLA_VRF_PORT_TABLE */
}

static int vrf_fill_slave_info(struct sk_buff *skb,
                               const struct net_device *vrf_dev,
                               const struct net_device *slave_dev)
{
        struct net_vrf *vrf = netdev_priv(vrf_dev);

        if (nla_put_u32(skb, IFLA_VRF_PORT_TABLE, vrf->tb_id))
                return -EMSGSIZE;

        return 0;
}

static const struct nla_policy vrf_nl_policy[IFLA_VRF_MAX + 1] = {
        [IFLA_VRF_TABLE] = { .type = NLA_U32 },
};

static struct rtnl_link_ops vrf_link_ops __read_mostly = {
        .kind           = DRV_NAME,
        .priv_size      = sizeof(struct net_vrf),

        .get_size       = vrf_nl_getsize,
        .policy         = vrf_nl_policy,
        .validate       = vrf_validate,
        .fill_info      = vrf_fillinfo,

        .get_slave_size  = vrf_get_slave_size,
        .fill_slave_info = vrf_fill_slave_info,

        .newlink        = vrf_newlink,
        .dellink        = vrf_dellink,
        .setup          = vrf_setup,
        .maxtype        = IFLA_VRF_MAX,
};

static int vrf_device_event(struct notifier_block *unused,
                            unsigned long event, void *ptr)
{
        struct net_device *dev = netdev_notifier_info_to_dev(ptr);

        /* only care about unregister events to drop slave references */
        if (event == NETDEV_UNREGISTER) {
                struct net_device *vrf_dev;

                if (!netif_is_l3_slave(dev))
                        goto out;

                vrf_dev = netdev_master_upper_dev_get(dev);
                vrf_del_slave(vrf_dev, dev);
        }
out:
        return NOTIFY_DONE;
}

static struct notifier_block vrf_notifier_block __read_mostly = {
        .notifier_call = vrf_device_event,
};

static int vrf_map_init(struct vrf_map *vmap)
{
        spin_lock_init(&vmap->vmap_lock);
        hash_init(vmap->ht);

        vmap->strict_mode = false;

        return 0;
}

#ifdef CONFIG_SYSCTL
static bool vrf_strict_mode(struct vrf_map *vmap)
{
        bool strict_mode;

        vrf_map_lock(vmap);
        strict_mode = vmap->strict_mode;
        vrf_map_unlock(vmap);

        return strict_mode;
}

static int vrf_strict_mode_change(struct vrf_map *vmap, bool new_mode)
{
        bool *cur_mode;
        int res = 0;

        vrf_map_lock(vmap);

        cur_mode = &vmap->strict_mode;
        if (*cur_mode == new_mode)
                goto unlock;

        if (*cur_mode) {
                /* disable strict mode */
                *cur_mode = false;
        } else {
                if (vmap->shared_tables) {
                        /* we cannot allow strict_mode because there are some
                         * vrfs that share one or more tables.
                         */
                        res = -EBUSY;
                        goto unlock;
                }

                /* no tables are shared among vrfs, so we can go back
                 * to 1:1 association between a vrf with its table.
                 */
                *cur_mode = true;
        }

unlock:
        vrf_map_unlock(vmap);

        return res;
}

static int vrf_shared_table_handler(const struct ctl_table *table, int write,
                                    void *buffer, size_t *lenp, loff_t *ppos)
{
        struct net *net = (struct net *)table->extra1;
        struct vrf_map *vmap = netns_vrf_map(net);
        int proc_strict_mode = 0;
        struct ctl_table tmp = {
                .procname       = table->procname,
                .data           = &proc_strict_mode,
                .maxlen         = sizeof(int),
                .mode           = table->mode,
                .extra1         = SYSCTL_ZERO,
                .extra2         = SYSCTL_ONE,
        };
        int ret;

        if (!write)
                proc_strict_mode = vrf_strict_mode(vmap);

        ret = proc_dointvec_minmax(&tmp, write, buffer, lenp, ppos);

        if (write && ret == 0)
                ret = vrf_strict_mode_change(vmap, (bool)proc_strict_mode);

        return ret;
}

static const struct ctl_table vrf_table[] = {
        {
                .procname       = "strict_mode",
                .data           = NULL,
                .maxlen         = sizeof(int),
                .mode           = 0644,
                .proc_handler   = vrf_shared_table_handler,
                /* set by the vrf_netns_init */
                .extra1         = NULL,
        },
};

static int vrf_netns_init_sysctl(struct net *net, struct netns_vrf *nn_vrf)
{
        struct ctl_table *table;

        table = kmemdup(vrf_table, sizeof(vrf_table), GFP_KERNEL);
        if (!table)
                return -ENOMEM;

        /* init the extra1 parameter with the reference to current netns */
        table[0].extra1 = net;

        nn_vrf->ctl_hdr = register_net_sysctl_sz(net, "net/vrf", table,
                                                 ARRAY_SIZE(vrf_table));
        if (!nn_vrf->ctl_hdr) {
                kfree(table);
                return -ENOMEM;
        }

        return 0;
}

static void vrf_netns_exit_sysctl(struct net *net)
{
        struct netns_vrf *nn_vrf = net_generic(net, vrf_net_id);
        const struct ctl_table *table;

        table = nn_vrf->ctl_hdr->ctl_table_arg;
        unregister_net_sysctl_table(nn_vrf->ctl_hdr);
        kfree(table);
}
#else
static int vrf_netns_init_sysctl(struct net *net, struct netns_vrf *nn_vrf)
{
        return 0;
}

static void vrf_netns_exit_sysctl(struct net *net)
{
}
#endif

/* Initialize per network namespace state */
static int __net_init vrf_netns_init(struct net *net)
{
        struct netns_vrf *nn_vrf = net_generic(net, vrf_net_id);

        nn_vrf->add_fib_rules = true;
        vrf_map_init(&nn_vrf->vmap);

        return vrf_netns_init_sysctl(net, nn_vrf);
}

static void __net_exit vrf_netns_exit(struct net *net)
{
        vrf_netns_exit_sysctl(net);
}

static struct pernet_operations vrf_net_ops __net_initdata = {
        .init = vrf_netns_init,
        .exit = vrf_netns_exit,
        .id   = &vrf_net_id,
        .size = sizeof(struct netns_vrf),
};

static int __init vrf_init_module(void)
{
        int rc;

        register_netdevice_notifier(&vrf_notifier_block);

        rc = register_pernet_subsys(&vrf_net_ops);
        if (rc < 0)
                goto error;

        rc = l3mdev_table_lookup_register(L3MDEV_TYPE_VRF,
                                          vrf_ifindex_lookup_by_table_id);
        if (rc < 0)
                goto unreg_pernet;

        rc = rtnl_link_register(&vrf_link_ops);
        if (rc < 0)
                goto table_lookup_unreg;

        return 0;

table_lookup_unreg:
        l3mdev_table_lookup_unregister(L3MDEV_TYPE_VRF,
                                       vrf_ifindex_lookup_by_table_id);

unreg_pernet:
        unregister_pernet_subsys(&vrf_net_ops);

error:
        unregister_netdevice_notifier(&vrf_notifier_block);
        return rc;
}

module_init(vrf_init_module);
MODULE_AUTHOR("Shrijeet Mukherjee, David Ahern");
MODULE_DESCRIPTION("Device driver to instantiate VRF domains");
MODULE_LICENSE("GPL");
MODULE_ALIAS_RTNL_LINK(DRV_NAME);
MODULE_VERSION(DRV_VERSION);