/*
 * 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
 *
 * 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 <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/inetdevice.h>
#include <net/arp.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/netns/generic.h>

#define DRV_NAME        "vrf"
#define DRV_VERSION     "1.0"

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

static unsigned int vrf_net_id;

struct net_vrf {
        struct rtable __rcu     *rth;
        struct rtable __rcu     *rth_local;
        struct rt6_info __rcu   *rt6;
        struct rt6_info __rcu   *rt6_local;
        u32                     tb_id;
};

struct pcpu_dstats {
        u64                     tx_pkts;
        u64                     tx_bytes;
        u64                     tx_drps;
        u64                     rx_pkts;
        u64                     rx_bytes;
        u64                     rx_drps;
        struct u64_stats_sync   syncp;
};

static void vrf_rx_stats(struct net_device *dev, int len)
{
        struct pcpu_dstats *dstats = this_cpu_ptr(dev->dstats);

        u64_stats_update_begin(&dstats->syncp);
        dstats->rx_pkts++;
        dstats->rx_bytes += len;
        u64_stats_update_end(&dstats->syncp);
}

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

static void vrf_get_stats64(struct net_device *dev,
                            struct rtnl_link_stats64 *stats)
{
        int i;

        for_each_possible_cpu(i) {
                const struct pcpu_dstats *dstats;
                u64 tbytes, tpkts, tdrops, rbytes, rpkts;
                unsigned int start;

                dstats = per_cpu_ptr(dev->dstats, i);
                do {
                        start = u64_stats_fetch_begin_irq(&dstats->syncp);
                        tbytes = dstats->tx_bytes;
                        tpkts = dstats->tx_pkts;
                        tdrops = dstats->tx_drps;
                        rbytes = dstats->rx_bytes;
                        rpkts = dstats->rx_pkts;
                } while (u64_stats_fetch_retry_irq(&dstats->syncp, start));
                stats->tx_bytes += tbytes;
                stats->tx_packets += tpkts;
                stats->tx_dropped += tdrops;
                stats->rx_bytes += rbytes;
                stats->rx_packets += rpkts;
        }
}

/* 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;
        struct Qdisc *qdisc;

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

        txq = netdev_get_tx_queue(dev, 0);
        qdisc = rcu_access_pointer(txq->qdisc);

        return !qdisc->enqueue;
}

/* 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)
{
        int len = skb->len;

        skb_orphan(skb);

        skb_dst_set(skb, dst);
        skb_dst_force(skb);

        /* 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))
                vrf_rx_stats(dev, len);
        else
                this_cpu_inc(dev->dstats->rx_drps);

        return NETDEV_TX_OK;
}

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

        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 = ipv6_hdr(skb);
        struct net *net = dev_net(skb->dev);
        struct flowi6 fl6 = {
                /* needed to match OIF rule */
                .flowi6_oif = dev->ifindex,
                .flowi6_iif = LOOPBACK_IFINDEX,
                .daddr = iph->daddr,
                .saddr = iph->saddr,
                .flowlabel = ip6_flowinfo(iph),
                .flowi6_mark = skb->mark,
                .flowi6_proto = iph->nexthdr,
                .flowi6_flags = FLOWI_FLAG_SKIP_NH_OIF,
        };
        int ret = NET_XMIT_DROP;
        struct dst_entry *dst;
        struct dst_entry *dst_null = &net->ipv6.ip6_null_entry->dst;

        dst = ip6_route_output(net, NULL, &fl6);
        if (dst == dst_null)
                goto err;

        skb_dst_drop(skb);

        /* if dst.dev is loopback or the VRF device again this is locally
         * originated traffic destined to a local address. Short circuit
         * to Rx path using our local dst
         */
        if (dst->dev == net->loopback_dev || dst->dev == dev) {
                struct net_vrf *vrf = netdev_priv(dev);
                struct rt6_info *rt6_local;

                /* release looked up dst and use cached local dst */
                dst_release(dst);

                rcu_read_lock();

                rt6_local = rcu_dereference(vrf->rt6_local);
                if (unlikely(!rt6_local)) {
                        rcu_read_unlock();
                        goto err;
                }

                /* Ordering issue: cached local dst is created on newlink
                 * before the IPv6 initialization. Using the local dst
                 * requires rt6i_idev to be set so make sure it is.
                 */
                if (unlikely(!rt6_local->rt6i_idev)) {
                        rt6_local->rt6i_idev = in6_dev_get(dev);
                        if (!rt6_local->rt6i_idev) {
                                rcu_read_unlock();
                                goto err;
                        }
                }

                dst = &rt6_local->dst;
                dst_hold(dst);

                rcu_read_unlock();

                return vrf_local_xmit(skb, dev, &rt6_local->dst);
        }

        skb_dst_set(skb, dst);

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

        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 = ip_hdr(skb);
        int ret = NET_XMIT_DROP;
        struct flowi4 fl4 = {
                /* needed to match OIF rule */
                .flowi4_oif = vrf_dev->ifindex,
                .flowi4_iif = LOOPBACK_IFINDEX,
                .flowi4_tos = RT_TOS(ip4h->tos),
                .flowi4_flags = FLOWI_FLAG_ANYSRC | FLOWI_FLAG_SKIP_NH_OIF,
                .flowi4_proto = ip4h->protocol,
                .daddr = ip4h->daddr,
                .saddr = ip4h->saddr,
        };
        struct net *net = dev_net(vrf_dev);
        struct rtable *rt;

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

        skb_dst_drop(skb);

        /* if dst.dev is loopback or the VRF device again this is locally
         * originated traffic destined to a local address. Short circuit
         * to Rx path using our local dst
         */
        if (rt->dst.dev == net->loopback_dev || rt->dst.dev == vrf_dev) {
                struct net_vrf *vrf = netdev_priv(vrf_dev);
                struct rtable *rth_local;
                struct dst_entry *dst = NULL;

                ip_rt_put(rt);

                rcu_read_lock();

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

                rcu_read_unlock();

                if (unlikely(!dst))
                        goto err;

                return vrf_local_xmit(skb, vrf_dev, 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);
        }

        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)
{
        int len = skb->len;
        netdev_tx_t ret = is_ip_tx_frame(skb, dev);

        if (likely(ret == NET_XMIT_SUCCESS || ret == NET_XMIT_CN)) {
                struct pcpu_dstats *dstats = this_cpu_ptr(dev->dstats);

                u64_stats_update_begin(&dstats->syncp);
                dstats->tx_pkts++;
                dstats->tx_bytes += len;
                u64_stats_update_end(&dstats->syncp);
        } else {
                this_cpu_inc(dev->dstats->tx_drps);
        }

        return ret;
}

static int vrf_finish_direct(struct net *net, struct sock *sk,
                             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);
        }

        return 1;
}

#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;
        struct neighbour *neigh;
        struct in6_addr *nexthop;
        int ret;

        nf_reset(skb);

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

        rcu_read_lock_bh();
        nexthop = rt6_nexthop((struct 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);
                rcu_read_unlock_bh();
                return ret;
        }
        rcu_read_unlock_bh();

        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(struct net *net, struct sock *sk,
                              struct sk_buff *skb)
{
        skb->protocol = htons(ETH_P_IPV6);

        return NF_HOOK_COND(NFPROTO_IPV6, NF_INET_POST_ROUTING,
                            net, sk, skb, NULL, skb->dev,
                            vrf_finish_direct,
                            !(IPCB(skb)->flags & IPSKB_REROUTED));
}

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_output6_direct);

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

        /* reset skb device */
        if (likely(err == 1))
                nf_reset(skb);
        else
                skb = NULL;

        return skb;
}

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;

        if (qdisc_tx_is_default(vrf_dev))
                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 rt6_info *rt6_local = rtnl_dereference(vrf->rt6_local);
        struct net *net = dev_net(dev);
        struct dst_entry *dst;

        RCU_INIT_POINTER(vrf->rt6, NULL);
        RCU_INIT_POINTER(vrf->rt6_local, 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;
                dev_put(dst->dev);
                dst->dev = net->loopback_dev;
                dev_hold(dst->dev);
                dst_release(dst);
        }

        if (rt6_local) {
                if (rt6_local->rt6i_idev) {
                        in6_dev_put(rt6_local->rt6i_idev);
                        rt6_local->rt6i_idev = NULL;
                }

                dst = &rt6_local->dst;
                dev_put(dst->dev);
                dst->dev = net->loopback_dev;
                dev_hold(dst->dev);
                dst_release(dst);
        }
}

static int vrf_rt6_create(struct net_device *dev)
{
        int flags = DST_HOST | DST_NOPOLICY | DST_NOXFRM;
        struct net_vrf *vrf = netdev_priv(dev);
        struct net *net = dev_net(dev);
        struct fib6_table *rt6i_table;
        struct rt6_info *rt6, *rt6_local;
        int rc = -ENOMEM;

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

        rt6i_table = fib6_new_table(net, vrf->tb_id);
        if (!rt6i_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->rt6i_table = rt6i_table;
        rt6->dst.output = vrf_output6;

        /* create a dst for local routing - packets sent locally
         * to local address via the VRF device as a loopback
         */
        rt6_local = ip6_dst_alloc(net, dev, flags);
        if (!rt6_local) {
                dst_release(&rt6->dst);
                goto out;
        }

        rt6_local->rt6i_idev  = in6_dev_get(dev);
        rt6_local->rt6i_flags = RTF_UP | RTF_NONEXTHOP | RTF_LOCAL;
        rt6_local->rt6i_table = rt6i_table;
        rt6_local->dst.input  = ip6_input;

        rcu_assign_pointer(vrf->rt6, rt6);
        rcu_assign_pointer(vrf->rt6_local, rt6_local);

        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 = (struct rtable *)dst;
        struct net_device *dev = dst->dev;
        unsigned int hh_len = LL_RESERVED_SPACE(dev);
        struct neighbour *neigh;
        u32 nexthop;
        int ret = -EINVAL;

        nf_reset(skb);

        /* Be paranoid, rather than too clever. */
        if (unlikely(skb_headroom(skb) < hh_len && dev->header_ops)) {
                struct sk_buff *skb2;

                skb2 = skb_realloc_headroom(skb, LL_RESERVED_SPACE(dev));
                if (!skb2) {
                        ret = -ENOMEM;
                        goto err;
                }
                if (skb->sk)
                        skb_set_owner_w(skb2, skb->sk);

                consume_skb(skb);
                skb = skb2;
        }

        rcu_read_lock_bh();

        nexthop = (__force u32)rt_nexthop(rt, ip_hdr(skb)->daddr);
        neigh = __ipv4_neigh_lookup_noref(dev, nexthop);
        if (unlikely(!neigh))
                neigh = __neigh_create(&arp_tbl, &nexthop, dev, false);
        if (!IS_ERR(neigh)) {
                sock_confirm_neigh(skb, neigh);
                ret = neigh_output(neigh, skb);
        }

        rcu_read_unlock_bh();
err:
        if (unlikely(ret < 0))
                vrf_tx_error(skb->dev, skb);
        return ret;
}

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(struct net *net, struct sock *sk,
                             struct sk_buff *skb)
{
        skb->protocol = htons(ETH_P_IP);

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

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_output_direct);

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

        /* reset skb device */
        if (likely(err == 1))
                nf_reset(skb);
        else
                skb = NULL;

        return skb;
}

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

        if (qdisc_tx_is_default(vrf_dev))
                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 rtable *rth_local = rtnl_dereference(vrf->rth_local);
        struct net *net = dev_net(dev);
        struct dst_entry *dst;

        RCU_INIT_POINTER(vrf->rth, NULL);
        RCU_INIT_POINTER(vrf->rth_local, 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;
                dev_put(dst->dev);
                dst->dev = net->loopback_dev;
                dev_hold(dst->dev);
                dst_release(dst);
        }

        if (rth_local) {
                dst = &rth_local->dst;
                dev_put(dst->dev);
                dst->dev = net->loopback_dev;
                dev_hold(dst->dev);
                dst_release(dst);
        }
}

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

        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, 1, 0);
        if (!rth)
                return -ENOMEM;

        /* create a dst for local ingress routing - packets sent locally
         * to local address via the VRF device as a loopback
         */
        rth_local = rt_dst_alloc(dev, RTCF_LOCAL, RTN_LOCAL, 1, 1, 0);
        if (!rth_local) {
                dst_release(&rth->dst);
                return -ENOMEM;
        }

        rth->dst.output = vrf_output;
        rth->rt_table_id = vrf->tb_id;

        rth_local->rt_table_id = vrf->tb_id;

        rcu_assign_pointer(vrf->rth, rth);
        rcu_assign_pointer(vrf->rth_local, rth_local);

        return 0;
}

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

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

        if (!netif_running(dev))
                return;

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

        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)
{
        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)
                return -EOPNOTSUPP;

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

        cycle_netdev(port_dev);

        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)
{
        if (netif_is_l3_master(port_dev) || netif_is_l3_slave(port_dev))
                return -EINVAL;

        return do_vrf_add_slave(dev, port_dev);
}

/* 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);

        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);

        free_percpu(dev->dstats);
        dev->dstats = NULL;
}

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

        dev->dstats = netdev_alloc_pcpu_stats(struct pcpu_dstats);
        if (!dev->dstats)
                goto out_nomem;

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

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

        dev->flags = IFF_MASTER | IFF_NOARP;

        /* MTU is irrelevant for VRF device; set to 64k similar to lo */
        dev->mtu = 64 * 1024;

        /* 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_stats:
        free_percpu(dev->dstats);
        dev->dstats = NULL;
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_get_stats64        = vrf_get_stats64,
        .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;
}

#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,
                                             int flags)
{
        struct net_vrf *vrf = netdev_priv(dev);
        struct fib6_table *table = NULL;
        struct rt6_info *rt6;

        rcu_read_lock();

        /* fib6_table does not have a refcnt and can not be freed */
        rt6 = rcu_dereference(vrf->rt6);
        if (likely(rt6))
                table = rt6->rt6i_table;

        rcu_read_unlock();

        if (!table)
                return NULL;

        return ip6_pol_route(net, table, ifindex, fl6, 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 = {
                .daddr          = iph->daddr,
                .saddr          = iph->saddr,
                .flowlabel      = ip6_flowinfo(iph),
                .flowi6_mark    = skb->mark,
                .flowi6_proto   = iph->nexthdr,
                .flowi6_iif     = ifindex,
        };
        struct net *net = dev_net(vrf_dev);
        struct rt6_info *rt6;

        rt6 = vrf_ip6_route_lookup(net, vrf_dev, &fl6, ifindex,
                                   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;

        /* 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->dev = vrf_dev;
                skb->skb_iif = vrf_dev->ifindex;
                IP6CB(skb)->flags |= IP6SKB_L3SLAVE;
                skb->pkt_type = PACKET_HOST;
                goto out;
        }

        /* if packet is NDISC or addressed to multicast or link-local
         * then keep the ingress interface
         */
        need_strict = rt6_need_strict(&ipv6_hdr(skb)->daddr);
        if (!ipv6_ndisc_frame(skb) && !need_strict) {
                vrf_rx_stats(vrf_dev, skb->len);
                skb->dev = vrf_dev;
                skb->skb_iif = vrf_dev->ifindex;

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

        vrf_rx_stats(vrf_dev, skb->len);

        if (!list_empty(&vrf_dev->ptype_all)) {
                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
 */
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;
        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;
                dst_hold(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, 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)
{
        strlcpy(info->driver, DRV_NAME, sizeof(info->driver));
        strlcpy(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 */

        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 && !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_u32(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);

        /* fib_nl_{new,del}rule handling looks for net from skb->sk */
        skb->sk = dev_net(dev)->rtnl;
        if (add_it) {
                err = fib_nl_newrule(skb, nlh, NULL);
                if (err == -EEXIST)
                        err = 0;
        } else {
                err = fib_nl_delrule(skb, nlh, NULL);
                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

        return 0;

#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->features |= NETIF_F_LLTX;

        /* don't allow vrf devices to change network namespaces. */
        dev->features |= NETIF_F_NETNS_LOCAL;

        /* 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;
        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;
}

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)
                        return -EINVAL;
                if (!is_valid_ether_addr(nla_data(tb[IFLA_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);

        unregister_netdevice_queue(dev, head);
}

static int vrf_newlink(struct net *src_net, struct net_device *dev,
                       struct nlattr *tb[], struct nlattr *data[],
                       struct netlink_ext_ack *extack)
{
        struct net_vrf *vrf = netdev_priv(dev);
        bool *add_fib_rules;
        struct net *net;
        int err;

        if (!data || !data[IFLA_VRF_TABLE])
                return -EINVAL;

        vrf->tb_id = nla_get_u32(data[IFLA_VRF_TABLE]);
        if (vrf->tb_id == RT_TABLE_UNSPEC)
                return -EINVAL;

        dev->priv_flags |= IFF_L3MDEV_MASTER;

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

        net = dev_net(dev);
        add_fib_rules = net_generic(net, vrf_net_id);
        if (*add_fib_rules) {
                err = vrf_add_fib_rules(dev);
                if (err) {
                        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,
};

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

        *add_fib_rules = true;

        return 0;
}

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

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 = rtnl_link_register(&vrf_link_ops);
        if (rc < 0) {
                unregister_pernet_subsys(&vrf_net_ops);
                goto error;
        }

        return 0;

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);