/*
 *      IPv6 virtual tunneling interface
 *
 *      Copyright (C) 2013 secunet Security Networks AG
 *
 *      Author:
 *      Steffen Klassert <steffen.klassert@secunet.com>
 *
 *      Based on:
 *      net/ipv6/ip6_tunnel.c
 *
 *      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/capability.h>
#include <linux/errno.h>
#include <linux/types.h>
#include <linux/sockios.h>
#include <linux/icmp.h>
#include <linux/if.h>
#include <linux/in.h>
#include <linux/ip.h>
#include <linux/net.h>
#include <linux/in6.h>
#include <linux/netdevice.h>
#include <linux/if_arp.h>
#include <linux/icmpv6.h>
#include <linux/init.h>
#include <linux/route.h>
#include <linux/rtnetlink.h>
#include <linux/netfilter_ipv6.h>
#include <linux/slab.h>
#include <linux/hash.h>

#include <linux/uaccess.h>
#include <linux/atomic.h>

#include <net/icmp.h>
#include <net/ip.h>
#include <net/ip_tunnels.h>
#include <net/ipv6.h>
#include <net/ip6_route.h>
#include <net/addrconf.h>
#include <net/ip6_tunnel.h>
#include <net/xfrm.h>
#include <net/net_namespace.h>
#include <net/netns/generic.h>
#include <linux/etherdevice.h>

#define IP6_VTI_HASH_SIZE_SHIFT  5
#define IP6_VTI_HASH_SIZE (1 << IP6_VTI_HASH_SIZE_SHIFT)

static u32 HASH(const struct in6_addr *addr1, const struct in6_addr *addr2)
{
        u32 hash = ipv6_addr_hash(addr1) ^ ipv6_addr_hash(addr2);

        return hash_32(hash, IP6_VTI_HASH_SIZE_SHIFT);
}

static int vti6_dev_init(struct net_device *dev);
static void vti6_dev_setup(struct net_device *dev);
static struct rtnl_link_ops vti6_link_ops __read_mostly;

static unsigned int vti6_net_id __read_mostly;
struct vti6_net {
        /* the vti6 tunnel fallback device */
        struct net_device *fb_tnl_dev;
        /* lists for storing tunnels in use */
        struct ip6_tnl __rcu *tnls_r_l[IP6_VTI_HASH_SIZE];
        struct ip6_tnl __rcu *tnls_wc[1];
        struct ip6_tnl __rcu **tnls[2];
};

#define for_each_vti6_tunnel_rcu(start) \
        for (t = rcu_dereference(start); t; t = rcu_dereference(t->next))

/**
 * vti6_tnl_lookup - fetch tunnel matching the end-point addresses
 *   @net: network namespace
 *   @remote: the address of the tunnel exit-point
 *   @local: the address of the tunnel entry-point
 *
 * Return:
 *   tunnel matching given end-points if found,
 *   else fallback tunnel if its device is up,
 *   else %NULL
 **/
static struct ip6_tnl *
vti6_tnl_lookup(struct net *net, const struct in6_addr *remote,
                const struct in6_addr *local)
{
        unsigned int hash = HASH(remote, local);
        struct ip6_tnl *t;
        struct vti6_net *ip6n = net_generic(net, vti6_net_id);
        struct in6_addr any;

        for_each_vti6_tunnel_rcu(ip6n->tnls_r_l[hash]) {
                if (ipv6_addr_equal(local, &t->parms.laddr) &&
                    ipv6_addr_equal(remote, &t->parms.raddr) &&
                    (t->dev->flags & IFF_UP))
                        return t;
        }

        memset(&any, 0, sizeof(any));
        hash = HASH(&any, local);
        for_each_vti6_tunnel_rcu(ip6n->tnls_r_l[hash]) {
                if (ipv6_addr_equal(local, &t->parms.laddr) &&
                    (t->dev->flags & IFF_UP))
                        return t;
        }

        hash = HASH(remote, &any);
        for_each_vti6_tunnel_rcu(ip6n->tnls_r_l[hash]) {
                if (ipv6_addr_equal(remote, &t->parms.raddr) &&
                    (t->dev->flags & IFF_UP))
                        return t;
        }

        t = rcu_dereference(ip6n->tnls_wc[0]);
        if (t && (t->dev->flags & IFF_UP))
                return t;

        return NULL;
}

/**
 * vti6_tnl_bucket - get head of list matching given tunnel parameters
 *   @p: parameters containing tunnel end-points
 *
 * Description:
 *   vti6_tnl_bucket() returns the head of the list matching the
 *   &struct in6_addr entries laddr and raddr in @p.
 *
 * Return: head of IPv6 tunnel list
 **/
static struct ip6_tnl __rcu **
vti6_tnl_bucket(struct vti6_net *ip6n, const struct __ip6_tnl_parm *p)
{
        const struct in6_addr *remote = &p->raddr;
        const struct in6_addr *local = &p->laddr;
        unsigned int h = 0;
        int prio = 0;

        if (!ipv6_addr_any(remote) || !ipv6_addr_any(local)) {
                prio = 1;
                h = HASH(remote, local);
        }
        return &ip6n->tnls[prio][h];
}

static void
vti6_tnl_link(struct vti6_net *ip6n, struct ip6_tnl *t)
{
        struct ip6_tnl __rcu **tp = vti6_tnl_bucket(ip6n, &t->parms);

        rcu_assign_pointer(t->next , rtnl_dereference(*tp));
        rcu_assign_pointer(*tp, t);
}

static void
vti6_tnl_unlink(struct vti6_net *ip6n, struct ip6_tnl *t)
{
        struct ip6_tnl __rcu **tp;
        struct ip6_tnl *iter;

        for (tp = vti6_tnl_bucket(ip6n, &t->parms);
             (iter = rtnl_dereference(*tp)) != NULL;
             tp = &iter->next) {
                if (t == iter) {
                        rcu_assign_pointer(*tp, t->next);
                        break;
                }
        }
}

static void vti6_dev_free(struct net_device *dev)
{
        free_percpu(dev->tstats);
}

static int vti6_tnl_create2(struct net_device *dev)
{
        struct ip6_tnl *t = netdev_priv(dev);
        struct net *net = dev_net(dev);
        struct vti6_net *ip6n = net_generic(net, vti6_net_id);
        int err;

        dev->rtnl_link_ops = &vti6_link_ops;
        err = register_netdevice(dev);
        if (err < 0)
                goto out;

        strcpy(t->parms.name, dev->name);

        dev_hold(dev);
        vti6_tnl_link(ip6n, t);

        return 0;

out:
        return err;
}

static struct ip6_tnl *vti6_tnl_create(struct net *net, struct __ip6_tnl_parm *p)
{
        struct net_device *dev;
        struct ip6_tnl *t;
        char name[IFNAMSIZ];
        int err;

        if (p->name[0]) {
                if (!dev_valid_name(p->name))
                        goto failed;
                strlcpy(name, p->name, IFNAMSIZ);
        } else {
                sprintf(name, "ip6_vti%%d");
        }

        dev = alloc_netdev(sizeof(*t), name, NET_NAME_UNKNOWN, vti6_dev_setup);
        if (!dev)
                goto failed;

        dev_net_set(dev, net);

        t = netdev_priv(dev);
        t->parms = *p;
        t->net = dev_net(dev);

        err = vti6_tnl_create2(dev);
        if (err < 0)
                goto failed_free;

        return t;

failed_free:
        free_netdev(dev);
failed:
        return NULL;
}

/**
 * vti6_locate - find or create tunnel matching given parameters
 *   @net: network namespace
 *   @p: tunnel parameters
 *   @create: != 0 if allowed to create new tunnel if no match found
 *
 * Description:
 *   vti6_locate() first tries to locate an existing tunnel
 *   based on @parms. If this is unsuccessful, but @create is set a new
 *   tunnel device is created and registered for use.
 *
 * Return:
 *   matching tunnel or NULL
 **/
static struct ip6_tnl *vti6_locate(struct net *net, struct __ip6_tnl_parm *p,
                                   int create)
{
        const struct in6_addr *remote = &p->raddr;
        const struct in6_addr *local = &p->laddr;
        struct ip6_tnl __rcu **tp;
        struct ip6_tnl *t;
        struct vti6_net *ip6n = net_generic(net, vti6_net_id);

        for (tp = vti6_tnl_bucket(ip6n, p);
             (t = rtnl_dereference(*tp)) != NULL;
             tp = &t->next) {
                if (ipv6_addr_equal(local, &t->parms.laddr) &&
                    ipv6_addr_equal(remote, &t->parms.raddr)) {
                        if (create)
                                return NULL;

                        return t;
                }
        }
        if (!create)
                return NULL;
        return vti6_tnl_create(net, p);
}

/**
 * vti6_dev_uninit - tunnel device uninitializer
 *   @dev: the device to be destroyed
 *
 * Description:
 *   vti6_dev_uninit() removes tunnel from its list
 **/
static void vti6_dev_uninit(struct net_device *dev)
{
        struct ip6_tnl *t = netdev_priv(dev);
        struct vti6_net *ip6n = net_generic(t->net, vti6_net_id);

        if (dev == ip6n->fb_tnl_dev)
                RCU_INIT_POINTER(ip6n->tnls_wc[0], NULL);
        else
                vti6_tnl_unlink(ip6n, t);
        dev_put(dev);
}

static int vti6_rcv(struct sk_buff *skb)
{
        struct ip6_tnl *t;
        const struct ipv6hdr *ipv6h = ipv6_hdr(skb);

        rcu_read_lock();
        t = vti6_tnl_lookup(dev_net(skb->dev), &ipv6h->saddr, &ipv6h->daddr);
        if (t) {
                if (t->parms.proto != IPPROTO_IPV6 && t->parms.proto != 0) {
                        rcu_read_unlock();
                        goto discard;
                }

                if (!xfrm6_policy_check(NULL, XFRM_POLICY_IN, skb)) {
                        rcu_read_unlock();
                        return 0;
                }

                ipv6h = ipv6_hdr(skb);
                if (!ip6_tnl_rcv_ctl(t, &ipv6h->daddr, &ipv6h->saddr)) {
                        t->dev->stats.rx_dropped++;
                        rcu_read_unlock();
                        goto discard;
                }

                rcu_read_unlock();

                return xfrm6_rcv_tnl(skb, t);
        }
        rcu_read_unlock();
        return -EINVAL;
discard:
        kfree_skb(skb);
        return 0;
}

static int vti6_rcv_cb(struct sk_buff *skb, int err)
{
        unsigned short family;
        struct net_device *dev;
        struct pcpu_sw_netstats *tstats;
        struct xfrm_state *x;
        struct xfrm_mode *inner_mode;
        struct ip6_tnl *t = XFRM_TUNNEL_SKB_CB(skb)->tunnel.ip6;
        u32 orig_mark = skb->mark;
        int ret;

        if (!t)
                return 1;

        dev = t->dev;

        if (err) {
                dev->stats.rx_errors++;
                dev->stats.rx_dropped++;

                return 0;
        }

        x = xfrm_input_state(skb);

        inner_mode = x->inner_mode;

        if (x->sel.family == AF_UNSPEC) {
                inner_mode = xfrm_ip2inner_mode(x, XFRM_MODE_SKB_CB(skb)->protocol);
                if (inner_mode == NULL) {
                        XFRM_INC_STATS(dev_net(skb->dev),
                                       LINUX_MIB_XFRMINSTATEMODEERROR);
                        return -EINVAL;
                }
        }

        family = inner_mode->afinfo->family;

        skb->mark = be32_to_cpu(t->parms.i_key);
        ret = xfrm_policy_check(NULL, XFRM_POLICY_IN, skb, family);
        skb->mark = orig_mark;

        if (!ret)
                return -EPERM;

        skb_scrub_packet(skb, !net_eq(t->net, dev_net(skb->dev)));
        skb->dev = dev;

        tstats = this_cpu_ptr(dev->tstats);
        u64_stats_update_begin(&tstats->syncp);
        tstats->rx_packets++;
        tstats->rx_bytes += skb->len;
        u64_stats_update_end(&tstats->syncp);

        return 0;
}

/**
 * vti6_addr_conflict - compare packet addresses to tunnel's own
 *   @t: the outgoing tunnel device
 *   @hdr: IPv6 header from the incoming packet
 *
 * Description:
 *   Avoid trivial tunneling loop by checking that tunnel exit-point
 *   doesn't match source of incoming packet.
 *
 * Return:
 *   1 if conflict,
 *   0 else
 **/
static inline bool
vti6_addr_conflict(const struct ip6_tnl *t, const struct ipv6hdr *hdr)
{
        return ipv6_addr_equal(&t->parms.raddr, &hdr->saddr);
}

static bool vti6_state_check(const struct xfrm_state *x,
                             const struct in6_addr *dst,
                             const struct in6_addr *src)
{
        xfrm_address_t *daddr = (xfrm_address_t *)dst;
        xfrm_address_t *saddr = (xfrm_address_t *)src;

        /* if there is no transform then this tunnel is not functional.
         * Or if the xfrm is not mode tunnel.
         */
        if (!x || x->props.mode != XFRM_MODE_TUNNEL ||
            x->props.family != AF_INET6)
                return false;

        if (ipv6_addr_any(dst))
                return xfrm_addr_equal(saddr, &x->props.saddr, AF_INET6);

        if (!xfrm_state_addr_check(x, daddr, saddr, AF_INET6))
                return false;

        return true;
}

/**
 * vti6_xmit - send a packet
 *   @skb: the outgoing socket buffer
 *   @dev: the outgoing tunnel device
 *   @fl: the flow informations for the xfrm_lookup
 **/
static int
vti6_xmit(struct sk_buff *skb, struct net_device *dev, struct flowi *fl)
{
        struct ip6_tnl *t = netdev_priv(dev);
        struct net_device_stats *stats = &t->dev->stats;
        struct dst_entry *dst = skb_dst(skb);
        struct net_device *tdev;
        struct xfrm_state *x;
        int pkt_len = skb->len;
        int err = -1;
        int mtu;

        if (!dst)
                goto tx_err_link_failure;

        dst_hold(dst);
        dst = xfrm_lookup(t->net, dst, fl, NULL, 0);
        if (IS_ERR(dst)) {
                err = PTR_ERR(dst);
                dst = NULL;
                goto tx_err_link_failure;
        }

        x = dst->xfrm;
        if (!vti6_state_check(x, &t->parms.raddr, &t->parms.laddr))
                goto tx_err_link_failure;

        if (!ip6_tnl_xmit_ctl(t, (const struct in6_addr *)&x->props.saddr,
                              (const struct in6_addr *)&x->id.daddr))
                goto tx_err_link_failure;

        tdev = dst->dev;

        if (tdev == dev) {
                stats->collisions++;
                net_warn_ratelimited("%s: Local routing loop detected!\n",
                                     t->parms.name);
                goto tx_err_dst_release;
        }

        mtu = dst_mtu(dst);
        if (skb->len > mtu) {
                skb_dst_update_pmtu(skb, mtu);

                if (skb->protocol == htons(ETH_P_IPV6)) {
                        if (mtu < IPV6_MIN_MTU)
                                mtu = IPV6_MIN_MTU;

                        icmpv6_send(skb, ICMPV6_PKT_TOOBIG, 0, mtu);
                } else {
                        icmp_send(skb, ICMP_DEST_UNREACH, ICMP_FRAG_NEEDED,
                                  htonl(mtu));
                }

                err = -EMSGSIZE;
                goto tx_err_dst_release;
        }

        skb_scrub_packet(skb, !net_eq(t->net, dev_net(dev)));
        skb_dst_set(skb, dst);
        skb->dev = skb_dst(skb)->dev;

        err = dst_output(t->net, skb->sk, skb);
        if (net_xmit_eval(err) == 0)
                err = pkt_len;
        iptunnel_xmit_stats(dev, err);

        return 0;
tx_err_link_failure:
        stats->tx_carrier_errors++;
        dst_link_failure(skb);
tx_err_dst_release:
        dst_release(dst);
        return err;
}

static netdev_tx_t
vti6_tnl_xmit(struct sk_buff *skb, struct net_device *dev)
{
        struct ip6_tnl *t = netdev_priv(dev);
        struct net_device_stats *stats = &t->dev->stats;
        struct ipv6hdr *ipv6h;
        struct flowi fl;
        int ret;

        memset(&fl, 0, sizeof(fl));

        switch (skb->protocol) {
        case htons(ETH_P_IPV6):
                ipv6h = ipv6_hdr(skb);

                if ((t->parms.proto != IPPROTO_IPV6 && t->parms.proto != 0) ||
                    vti6_addr_conflict(t, ipv6h))
                        goto tx_err;

                xfrm_decode_session(skb, &fl, AF_INET6);
                memset(IP6CB(skb), 0, sizeof(*IP6CB(skb)));
                break;
        case htons(ETH_P_IP):
                xfrm_decode_session(skb, &fl, AF_INET);
                memset(IPCB(skb), 0, sizeof(*IPCB(skb)));
                break;
        default:
                goto tx_err;
        }

        /* override mark with tunnel output key */
        fl.flowi_mark = be32_to_cpu(t->parms.o_key);

        ret = vti6_xmit(skb, dev, &fl);
        if (ret < 0)
                goto tx_err;

        return NETDEV_TX_OK;

tx_err:
        stats->tx_errors++;
        stats->tx_dropped++;
        kfree_skb(skb);
        return NETDEV_TX_OK;
}

static int vti6_err(struct sk_buff *skb, struct inet6_skb_parm *opt,
                    u8 type, u8 code, int offset, __be32 info)
{
        __be32 spi;
        __u32 mark;
        struct xfrm_state *x;
        struct ip6_tnl *t;
        struct ip_esp_hdr *esph;
        struct ip_auth_hdr *ah;
        struct ip_comp_hdr *ipch;
        struct net *net = dev_net(skb->dev);
        const struct ipv6hdr *iph = (const struct ipv6hdr *)skb->data;
        int protocol = iph->nexthdr;

        t = vti6_tnl_lookup(dev_net(skb->dev), &iph->daddr, &iph->saddr);
        if (!t)
                return -1;

        mark = be32_to_cpu(t->parms.o_key);

        switch (protocol) {
        case IPPROTO_ESP:
                esph = (struct ip_esp_hdr *)(skb->data + offset);
                spi = esph->spi;
                break;
        case IPPROTO_AH:
                ah = (struct ip_auth_hdr *)(skb->data + offset);
                spi = ah->spi;
                break;
        case IPPROTO_COMP:
                ipch = (struct ip_comp_hdr *)(skb->data + offset);
                spi = htonl(ntohs(ipch->cpi));
                break;
        default:
                return 0;
        }

        if (type != ICMPV6_PKT_TOOBIG &&
            type != NDISC_REDIRECT)
                return 0;

        x = xfrm_state_lookup(net, mark, (const xfrm_address_t *)&iph->daddr,
                              spi, protocol, AF_INET6);
        if (!x)
                return 0;

        if (type == NDISC_REDIRECT)
                ip6_redirect(skb, net, skb->dev->ifindex, 0,
                             sock_net_uid(net, NULL));
        else
                ip6_update_pmtu(skb, net, info, 0, 0, sock_net_uid(net, NULL));
        xfrm_state_put(x);

        return 0;
}

static void vti6_link_config(struct ip6_tnl *t, bool keep_mtu)
{
        struct net_device *dev = t->dev;
        struct __ip6_tnl_parm *p = &t->parms;
        struct net_device *tdev = NULL;
        int mtu;

        memcpy(dev->dev_addr, &p->laddr, sizeof(struct in6_addr));
        memcpy(dev->broadcast, &p->raddr, sizeof(struct in6_addr));

        p->flags &= ~(IP6_TNL_F_CAP_XMIT | IP6_TNL_F_CAP_RCV |
                      IP6_TNL_F_CAP_PER_PACKET);
        p->flags |= ip6_tnl_get_cap(t, &p->laddr, &p->raddr);

        if (p->flags & IP6_TNL_F_CAP_XMIT && p->flags & IP6_TNL_F_CAP_RCV)
                dev->flags |= IFF_POINTOPOINT;
        else
                dev->flags &= ~IFF_POINTOPOINT;

        if (keep_mtu && dev->mtu) {
                dev->mtu = clamp(dev->mtu, dev->min_mtu, dev->max_mtu);
                return;
        }

        if (p->flags & IP6_TNL_F_CAP_XMIT) {
                int strict = (ipv6_addr_type(&p->raddr) &
                              (IPV6_ADDR_MULTICAST | IPV6_ADDR_LINKLOCAL));
                struct rt6_info *rt = rt6_lookup(t->net,
                                                 &p->raddr, &p->laddr,
                                                 p->link, NULL, strict);

                if (rt)
                        tdev = rt->dst.dev;
                ip6_rt_put(rt);
        }

        if (!tdev && p->link)
                tdev = __dev_get_by_index(t->net, p->link);

        if (tdev)
                mtu = tdev->mtu - sizeof(struct ipv6hdr);
        else
                mtu = ETH_DATA_LEN - LL_MAX_HEADER - sizeof(struct ipv6hdr);

        dev->mtu = max_t(int, mtu, IPV4_MIN_MTU);
}

/**
 * vti6_tnl_change - update the tunnel parameters
 *   @t: tunnel to be changed
 *   @p: tunnel configuration parameters
 *   @keep_mtu: MTU was set from userspace, don't re-compute it
 *
 * Description:
 *   vti6_tnl_change() updates the tunnel parameters
 **/
static int
vti6_tnl_change(struct ip6_tnl *t, const struct __ip6_tnl_parm *p,
                bool keep_mtu)
{
        t->parms.laddr = p->laddr;
        t->parms.raddr = p->raddr;
        t->parms.link = p->link;
        t->parms.i_key = p->i_key;
        t->parms.o_key = p->o_key;
        t->parms.proto = p->proto;
        t->parms.fwmark = p->fwmark;
        dst_cache_reset(&t->dst_cache);
        vti6_link_config(t, keep_mtu);
        return 0;
}

static int vti6_update(struct ip6_tnl *t, struct __ip6_tnl_parm *p,
                       bool keep_mtu)
{
        struct net *net = dev_net(t->dev);
        struct vti6_net *ip6n = net_generic(net, vti6_net_id);
        int err;

        vti6_tnl_unlink(ip6n, t);
        synchronize_net();
        err = vti6_tnl_change(t, p, keep_mtu);
        vti6_tnl_link(ip6n, t);
        netdev_state_change(t->dev);
        return err;
}

static void
vti6_parm_from_user(struct __ip6_tnl_parm *p, const struct ip6_tnl_parm2 *u)
{
        p->laddr = u->laddr;
        p->raddr = u->raddr;
        p->link = u->link;
        p->i_key = u->i_key;
        p->o_key = u->o_key;
        p->proto = u->proto;

        memcpy(p->name, u->name, sizeof(u->name));
}

static void
vti6_parm_to_user(struct ip6_tnl_parm2 *u, const struct __ip6_tnl_parm *p)
{
        u->laddr = p->laddr;
        u->raddr = p->raddr;
        u->link = p->link;
        u->i_key = p->i_key;
        u->o_key = p->o_key;
        if (u->i_key)
                u->i_flags |= GRE_KEY;
        if (u->o_key)
                u->o_flags |= GRE_KEY;
        u->proto = p->proto;

        memcpy(u->name, p->name, sizeof(u->name));
}

/**
 * vti6_ioctl - configure vti6 tunnels from userspace
 *   @dev: virtual device associated with tunnel
 *   @ifr: parameters passed from userspace
 *   @cmd: command to be performed
 *
 * Description:
 *   vti6_ioctl() is used for managing vti6 tunnels
 *   from userspace.
 *
 *   The possible commands are the following:
 *     %SIOCGETTUNNEL: get tunnel parameters for device
 *     %SIOCADDTUNNEL: add tunnel matching given tunnel parameters
 *     %SIOCCHGTUNNEL: change tunnel parameters to those given
 *     %SIOCDELTUNNEL: delete tunnel
 *
 *   The fallback device "ip6_vti0", created during module
 *   initialization, can be used for creating other tunnel devices.
 *
 * Return:
 *   0 on success,
 *   %-EFAULT if unable to copy data to or from userspace,
 *   %-EPERM if current process hasn't %CAP_NET_ADMIN set
 *   %-EINVAL if passed tunnel parameters are invalid,
 *   %-EEXIST if changing a tunnel's parameters would cause a conflict
 *   %-ENODEV if attempting to change or delete a nonexisting device
 **/
static int
vti6_ioctl(struct net_device *dev, struct ifreq *ifr, int cmd)
{
        int err = 0;
        struct ip6_tnl_parm2 p;
        struct __ip6_tnl_parm p1;
        struct ip6_tnl *t = NULL;
        struct net *net = dev_net(dev);
        struct vti6_net *ip6n = net_generic(net, vti6_net_id);

        switch (cmd) {
        case SIOCGETTUNNEL:
                if (dev == ip6n->fb_tnl_dev) {
                        if (copy_from_user(&p, ifr->ifr_ifru.ifru_data, sizeof(p))) {
                                err = -EFAULT;
                                break;
                        }
                        vti6_parm_from_user(&p1, &p);
                        t = vti6_locate(net, &p1, 0);
                } else {
                        memset(&p, 0, sizeof(p));
                }
                if (!t)
                        t = netdev_priv(dev);
                vti6_parm_to_user(&p, &t->parms);
                if (copy_to_user(ifr->ifr_ifru.ifru_data, &p, sizeof(p)))
                        err = -EFAULT;
                break;
        case SIOCADDTUNNEL:
        case SIOCCHGTUNNEL:
                err = -EPERM;
                if (!ns_capable(net->user_ns, CAP_NET_ADMIN))
                        break;
                err = -EFAULT;
                if (copy_from_user(&p, ifr->ifr_ifru.ifru_data, sizeof(p)))
                        break;
                err = -EINVAL;
                if (p.proto != IPPROTO_IPV6  && p.proto != 0)
                        break;
                vti6_parm_from_user(&p1, &p);
                t = vti6_locate(net, &p1, cmd == SIOCADDTUNNEL);
                if (dev != ip6n->fb_tnl_dev && cmd == SIOCCHGTUNNEL) {
                        if (t) {
                                if (t->dev != dev) {
                                        err = -EEXIST;
                                        break;
                                }
                        } else
                                t = netdev_priv(dev);

                        err = vti6_update(t, &p1, false);
                }
                if (t) {
                        err = 0;
                        vti6_parm_to_user(&p, &t->parms);
                        if (copy_to_user(ifr->ifr_ifru.ifru_data, &p, sizeof(p)))
                                err = -EFAULT;

                } else
                        err = (cmd == SIOCADDTUNNEL ? -ENOBUFS : -ENOENT);
                break;
        case SIOCDELTUNNEL:
                err = -EPERM;
                if (!ns_capable(net->user_ns, CAP_NET_ADMIN))
                        break;

                if (dev == ip6n->fb_tnl_dev) {
                        err = -EFAULT;
                        if (copy_from_user(&p, ifr->ifr_ifru.ifru_data, sizeof(p)))
                                break;
                        err = -ENOENT;
                        vti6_parm_from_user(&p1, &p);
                        t = vti6_locate(net, &p1, 0);
                        if (!t)
                                break;
                        err = -EPERM;
                        if (t->dev == ip6n->fb_tnl_dev)
                                break;
                        dev = t->dev;
                }
                err = 0;
                unregister_netdevice(dev);
                break;
        default:
                err = -EINVAL;
        }
        return err;
}

static const struct net_device_ops vti6_netdev_ops = {
        .ndo_init       = vti6_dev_init,
        .ndo_uninit     = vti6_dev_uninit,
        .ndo_start_xmit = vti6_tnl_xmit,
        .ndo_do_ioctl   = vti6_ioctl,
        .ndo_get_stats64 = ip_tunnel_get_stats64,
        .ndo_get_iflink = ip6_tnl_get_iflink,
};

/**
 * vti6_dev_setup - setup virtual tunnel device
 *   @dev: virtual device associated with tunnel
 *
 * Description:
 *   Initialize function pointers and device parameters
 **/
static void vti6_dev_setup(struct net_device *dev)
{
        dev->netdev_ops = &vti6_netdev_ops;
        dev->needs_free_netdev = true;
        dev->priv_destructor = vti6_dev_free;

        dev->type = ARPHRD_TUNNEL6;
        dev->min_mtu = IPV4_MIN_MTU;
        dev->max_mtu = IP_MAX_MTU - sizeof(struct ipv6hdr);
        dev->flags |= IFF_NOARP;
        dev->addr_len = sizeof(struct in6_addr);
        netif_keep_dst(dev);
        /* This perm addr will be used as interface identifier by IPv6 */
        dev->addr_assign_type = NET_ADDR_RANDOM;
        eth_random_addr(dev->perm_addr);
}

/**
 * vti6_dev_init_gen - general initializer for all tunnel devices
 *   @dev: virtual device associated with tunnel
 **/
static inline int vti6_dev_init_gen(struct net_device *dev)
{
        struct ip6_tnl *t = netdev_priv(dev);

        t->dev = dev;
        t->net = dev_net(dev);
        dev->tstats = netdev_alloc_pcpu_stats(struct pcpu_sw_netstats);
        if (!dev->tstats)
                return -ENOMEM;
        return 0;
}

/**
 * vti6_dev_init - initializer for all non fallback tunnel devices
 *   @dev: virtual device associated with tunnel
 **/
static int vti6_dev_init(struct net_device *dev)
{
        struct ip6_tnl *t = netdev_priv(dev);
        int err = vti6_dev_init_gen(dev);

        if (err)
                return err;
        vti6_link_config(t, true);
        return 0;
}

/**
 * vti6_fb_tnl_dev_init - initializer for fallback tunnel device
 *   @dev: fallback device
 *
 * Return: 0
 **/
static int __net_init vti6_fb_tnl_dev_init(struct net_device *dev)
{
        struct ip6_tnl *t = netdev_priv(dev);
        struct net *net = dev_net(dev);
        struct vti6_net *ip6n = net_generic(net, vti6_net_id);

        t->parms.proto = IPPROTO_IPV6;
        dev_hold(dev);

        rcu_assign_pointer(ip6n->tnls_wc[0], t);
        return 0;
}

static int vti6_validate(struct nlattr *tb[], struct nlattr *data[],
                         struct netlink_ext_ack *extack)
{
        return 0;
}

static void vti6_netlink_parms(struct nlattr *data[],
                               struct __ip6_tnl_parm *parms)
{
        memset(parms, 0, sizeof(*parms));

        if (!data)
                return;

        if (data[IFLA_VTI_LINK])
                parms->link = nla_get_u32(data[IFLA_VTI_LINK]);

        if (data[IFLA_VTI_LOCAL])
                parms->laddr = nla_get_in6_addr(data[IFLA_VTI_LOCAL]);

        if (data[IFLA_VTI_REMOTE])
                parms->raddr = nla_get_in6_addr(data[IFLA_VTI_REMOTE]);

        if (data[IFLA_VTI_IKEY])
                parms->i_key = nla_get_be32(data[IFLA_VTI_IKEY]);

        if (data[IFLA_VTI_OKEY])
                parms->o_key = nla_get_be32(data[IFLA_VTI_OKEY]);

        if (data[IFLA_VTI_FWMARK])
                parms->fwmark = nla_get_u32(data[IFLA_VTI_FWMARK]);
}

static int vti6_newlink(struct net *src_net, struct net_device *dev,
                        struct nlattr *tb[], struct nlattr *data[],
                        struct netlink_ext_ack *extack)
{
        struct net *net = dev_net(dev);
        struct ip6_tnl *nt;

        nt = netdev_priv(dev);
        vti6_netlink_parms(data, &nt->parms);

        nt->parms.proto = IPPROTO_IPV6;

        if (vti6_locate(net, &nt->parms, 0))
                return -EEXIST;

        return vti6_tnl_create2(dev);
}

static void vti6_dellink(struct net_device *dev, struct list_head *head)
{
        struct net *net = dev_net(dev);
        struct vti6_net *ip6n = net_generic(net, vti6_net_id);

        if (dev != ip6n->fb_tnl_dev)
                unregister_netdevice_queue(dev, head);
}

static int vti6_changelink(struct net_device *dev, struct nlattr *tb[],
                           struct nlattr *data[],
                           struct netlink_ext_ack *extack)

{
        struct ip6_tnl *t;
        struct __ip6_tnl_parm p;
        struct net *net = dev_net(dev);
        struct vti6_net *ip6n = net_generic(net, vti6_net_id);

        if (dev == ip6n->fb_tnl_dev)
                return -EINVAL;

        vti6_netlink_parms(data, &p);

        t = vti6_locate(net, &p, 0);

        if (t) {
                if (t->dev != dev)
                        return -EEXIST;
        } else
                t = netdev_priv(dev);

        return vti6_update(t, &p, tb && tb[IFLA_MTU]);
}

static size_t vti6_get_size(const struct net_device *dev)
{
        return
                /* IFLA_VTI_LINK */
                nla_total_size(4) +
                /* IFLA_VTI_LOCAL */
                nla_total_size(sizeof(struct in6_addr)) +
                /* IFLA_VTI_REMOTE */
                nla_total_size(sizeof(struct in6_addr)) +
                /* IFLA_VTI_IKEY */
                nla_total_size(4) +
                /* IFLA_VTI_OKEY */
                nla_total_size(4) +
                /* IFLA_VTI_FWMARK */
                nla_total_size(4) +
                0;
}

static int vti6_fill_info(struct sk_buff *skb, const struct net_device *dev)
{
        struct ip6_tnl *tunnel = netdev_priv(dev);
        struct __ip6_tnl_parm *parm = &tunnel->parms;

        if (nla_put_u32(skb, IFLA_VTI_LINK, parm->link) ||
            nla_put_in6_addr(skb, IFLA_VTI_LOCAL, &parm->laddr) ||
            nla_put_in6_addr(skb, IFLA_VTI_REMOTE, &parm->raddr) ||
            nla_put_be32(skb, IFLA_VTI_IKEY, parm->i_key) ||
            nla_put_be32(skb, IFLA_VTI_OKEY, parm->o_key) ||
            nla_put_u32(skb, IFLA_VTI_FWMARK, parm->fwmark))
                goto nla_put_failure;
        return 0;

nla_put_failure:
        return -EMSGSIZE;
}

static const struct nla_policy vti6_policy[IFLA_VTI_MAX + 1] = {
        [IFLA_VTI_LINK]         = { .type = NLA_U32 },
        [IFLA_VTI_LOCAL]        = { .len = sizeof(struct in6_addr) },
        [IFLA_VTI_REMOTE]       = { .len = sizeof(struct in6_addr) },
        [IFLA_VTI_IKEY]         = { .type = NLA_U32 },
        [IFLA_VTI_OKEY]         = { .type = NLA_U32 },
        [IFLA_VTI_FWMARK]       = { .type = NLA_U32 },
};

static struct rtnl_link_ops vti6_link_ops __read_mostly = {
        .kind           = "vti6",
        .maxtype        = IFLA_VTI_MAX,
        .policy         = vti6_policy,
        .priv_size      = sizeof(struct ip6_tnl),
        .setup          = vti6_dev_setup,
        .validate       = vti6_validate,
        .newlink        = vti6_newlink,
        .dellink        = vti6_dellink,
        .changelink     = vti6_changelink,
        .get_size       = vti6_get_size,
        .fill_info      = vti6_fill_info,
        .get_link_net   = ip6_tnl_get_link_net,
};

static void __net_exit vti6_destroy_tunnels(struct vti6_net *ip6n,
                                            struct list_head *list)
{
        int h;
        struct ip6_tnl *t;

        for (h = 0; h < IP6_VTI_HASH_SIZE; h++) {
                t = rtnl_dereference(ip6n->tnls_r_l[h]);
                while (t) {
                        unregister_netdevice_queue(t->dev, list);
                        t = rtnl_dereference(t->next);
                }
        }

        t = rtnl_dereference(ip6n->tnls_wc[0]);
        if (t)
                unregister_netdevice_queue(t->dev, list);
}

static int __net_init vti6_init_net(struct net *net)
{
        struct vti6_net *ip6n = net_generic(net, vti6_net_id);
        struct ip6_tnl *t = NULL;
        int err;

        ip6n->tnls[0] = ip6n->tnls_wc;
        ip6n->tnls[1] = ip6n->tnls_r_l;

        if (!net_has_fallback_tunnels(net))
                return 0;
        err = -ENOMEM;
        ip6n->fb_tnl_dev = alloc_netdev(sizeof(struct ip6_tnl), "ip6_vti0",
                                        NET_NAME_UNKNOWN, vti6_dev_setup);

        if (!ip6n->fb_tnl_dev)
                goto err_alloc_dev;
        dev_net_set(ip6n->fb_tnl_dev, net);
        ip6n->fb_tnl_dev->rtnl_link_ops = &vti6_link_ops;

        err = vti6_fb_tnl_dev_init(ip6n->fb_tnl_dev);
        if (err < 0)
                goto err_register;

        err = register_netdev(ip6n->fb_tnl_dev);
        if (err < 0)
                goto err_register;

        t = netdev_priv(ip6n->fb_tnl_dev);

        strcpy(t->parms.name, ip6n->fb_tnl_dev->name);
        return 0;

err_register:
        free_netdev(ip6n->fb_tnl_dev);
err_alloc_dev:
        return err;
}

static void __net_exit vti6_exit_batch_net(struct list_head *net_list)
{
        struct vti6_net *ip6n;
        struct net *net;
        LIST_HEAD(list);

        rtnl_lock();
        list_for_each_entry(net, net_list, exit_list) {
                ip6n = net_generic(net, vti6_net_id);
                vti6_destroy_tunnels(ip6n, &list);
        }
        unregister_netdevice_many(&list);
        rtnl_unlock();
}

static struct pernet_operations vti6_net_ops = {
        .init = vti6_init_net,
        .exit_batch = vti6_exit_batch_net,
        .id   = &vti6_net_id,
        .size = sizeof(struct vti6_net),
};

static struct xfrm6_protocol vti_esp6_protocol __read_mostly = {
        .handler        =       vti6_rcv,
        .cb_handler     =       vti6_rcv_cb,
        .err_handler    =       vti6_err,
        .priority       =       100,
};

static struct xfrm6_protocol vti_ah6_protocol __read_mostly = {
        .handler        =       vti6_rcv,
        .cb_handler     =       vti6_rcv_cb,
        .err_handler    =       vti6_err,
        .priority       =       100,
};

static struct xfrm6_protocol vti_ipcomp6_protocol __read_mostly = {
        .handler        =       vti6_rcv,
        .cb_handler     =       vti6_rcv_cb,
        .err_handler    =       vti6_err,
        .priority       =       100,
};

/**
 * vti6_tunnel_init - register protocol and reserve needed resources
 *
 * Return: 0 on success
 **/
static int __init vti6_tunnel_init(void)
{
        const char *msg;
        int err;

        msg = "tunnel device";
        err = register_pernet_device(&vti6_net_ops);
        if (err < 0)
                goto pernet_dev_failed;

        msg = "tunnel protocols";
        err = xfrm6_protocol_register(&vti_esp6_protocol, IPPROTO_ESP);
        if (err < 0)
                goto xfrm_proto_esp_failed;
        err = xfrm6_protocol_register(&vti_ah6_protocol, IPPROTO_AH);
        if (err < 0)
                goto xfrm_proto_ah_failed;
        err = xfrm6_protocol_register(&vti_ipcomp6_protocol, IPPROTO_COMP);
        if (err < 0)
                goto xfrm_proto_comp_failed;

        msg = "netlink interface";
        err = rtnl_link_register(&vti6_link_ops);
        if (err < 0)
                goto rtnl_link_failed;

        return 0;

rtnl_link_failed:
        xfrm6_protocol_deregister(&vti_ipcomp6_protocol, IPPROTO_COMP);
xfrm_proto_comp_failed:
        xfrm6_protocol_deregister(&vti_ah6_protocol, IPPROTO_AH);
xfrm_proto_ah_failed:
        xfrm6_protocol_deregister(&vti_esp6_protocol, IPPROTO_ESP);
xfrm_proto_esp_failed:
        unregister_pernet_device(&vti6_net_ops);
pernet_dev_failed:
        pr_err("vti6 init: failed to register %s\n", msg);
        return err;
}

/**
 * vti6_tunnel_cleanup - free resources and unregister protocol
 **/
static void __exit vti6_tunnel_cleanup(void)
{
        rtnl_link_unregister(&vti6_link_ops);
        xfrm6_protocol_deregister(&vti_ipcomp6_protocol, IPPROTO_COMP);
        xfrm6_protocol_deregister(&vti_ah6_protocol, IPPROTO_AH);
        xfrm6_protocol_deregister(&vti_esp6_protocol, IPPROTO_ESP);
        unregister_pernet_device(&vti6_net_ops);
}

module_init(vti6_tunnel_init);
module_exit(vti6_tunnel_cleanup);
MODULE_LICENSE("GPL");
MODULE_ALIAS_RTNL_LINK("vti6");
MODULE_ALIAS_NETDEV("ip6_vti0");
MODULE_AUTHOR("Steffen Klassert");
MODULE_DESCRIPTION("IPv6 virtual tunnel interface");