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[mirror_ubuntu-artful-kernel.git] / net / ipv4 / ipip.c

/*
 *      Linux NET3:     IP/IP protocol decoder.
 *
 *      Authors:
 *              Sam Lantinga (slouken@cs.ucdavis.edu)  02/01/95
 *
 *      Fixes:
 *              Alan Cox        :       Merged and made usable non modular (its so tiny its silly as
 *                                      a module taking up 2 pages).
 *              Alan Cox        :       Fixed bug with 1.3.18 and IPIP not working (now needs to set skb->h.iph)
 *                                      to keep ip_forward happy.
 *              Alan Cox        :       More fixes for 1.3.21, and firewall fix. Maybe this will work soon 8).
 *              Kai Schulte     :       Fixed #defines for IP_FIREWALL->FIREWALL
 *              David Woodhouse :       Perform some basic ICMP handling.
 *                                      IPIP Routing without decapsulation.
 *              Carlos Picoto   :       GRE over IP support
 *              Alexey Kuznetsov:       Reworked. Really, now it is truncated version of ipv4/ip_gre.c.
 *                                      I do not want to merge them together.
 *
 *      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.
 *
 */

/* tunnel.c: an IP tunnel driver

        The purpose of this driver is to provide an IP tunnel through
        which you can tunnel network traffic transparently across subnets.

        This was written by looking at Nick Holloway's dummy driver
        Thanks for the great code!

                -Sam Lantinga   (slouken@cs.ucdavis.edu)  02/01/95

        Minor tweaks:
                Cleaned up the code a little and added some pre-1.3.0 tweaks.
                dev->hard_header/hard_header_len changed to use no headers.
                Comments/bracketing tweaked.
                Made the tunnels use dev->name not tunnel: when error reporting.
                Added tx_dropped stat

                -Alan Cox       (alan@lxorguk.ukuu.org.uk) 21 March 95

        Reworked:
                Changed to tunnel to destination gateway in addition to the
                        tunnel's pointopoint address
                Almost completely rewritten
                Note:  There is currently no firewall or ICMP handling done.

                -Sam Lantinga   (slouken@cs.ucdavis.edu) 02/13/96

*/

/* Things I wish I had known when writing the tunnel driver:

        When the tunnel_xmit() function is called, the skb contains the
        packet to be sent (plus a great deal of extra info), and dev
        contains the tunnel device that _we_ are.

        When we are passed a packet, we are expected to fill in the
        source address with our source IP address.

        What is the proper way to allocate, copy and free a buffer?
        After you allocate it, it is a "0 length" chunk of memory
        starting at zero.  If you want to add headers to the buffer
        later, you'll have to call "skb_reserve(skb, amount)" with
        the amount of memory you want reserved.  Then, you call
        "skb_put(skb, amount)" with the amount of space you want in
        the buffer.  skb_put() returns a pointer to the top (#0) of
        that buffer.  skb->len is set to the amount of space you have
        "allocated" with skb_put().  You can then write up to skb->len
        bytes to that buffer.  If you need more, you can call skb_put()
        again with the additional amount of space you need.  You can
        find out how much more space you can allocate by calling
        "skb_tailroom(skb)".
        Now, to add header space, call "skb_push(skb, header_len)".
        This creates space at the beginning of the buffer and returns
        a pointer to this new space.  If later you need to strip a
        header from a buffer, call "skb_pull(skb, header_len)".
        skb_headroom() will return how much space is left at the top
        of the buffer (before the main data).  Remember, this headroom
        space must be reserved before the skb_put() function is called.
        */

/*
   This version of net/ipv4/ipip.c is cloned of net/ipv4/ip_gre.c

   For comments look at net/ipv4/ip_gre.c --ANK
 */


#include <linux/capability.h>
#include <linux/module.h>
#include <linux/types.h>
#include <linux/kernel.h>
#include <linux/slab.h>
#include <linux/uaccess.h>
#include <linux/skbuff.h>
#include <linux/netdevice.h>
#include <linux/in.h>
#include <linux/tcp.h>
#include <linux/udp.h>
#include <linux/if_arp.h>
#include <linux/init.h>
#include <linux/netfilter_ipv4.h>
#include <linux/if_ether.h>
#include <linux/inetdevice.h>
#include <linux/rculist.h>

#include <net/sock.h>
#include <net/ip.h>
#include <net/icmp.h>
#include <net/ip_tunnels.h>
#include <net/inet_ecn.h>
#include <net/xfrm.h>
#include <net/net_namespace.h>
#include <net/netns/generic.h>
#include <net/dst_metadata.h>

static bool log_ecn_error = true;
module_param(log_ecn_error, bool, 0644);
MODULE_PARM_DESC(log_ecn_error, "Log packets received with corrupted ECN");

static unsigned int ipip_net_id __read_mostly;

static int ipip_tunnel_init(struct net_device *dev);
static struct rtnl_link_ops ipip_link_ops __read_mostly;

static int ipip_err(struct sk_buff *skb, u32 info)
{

/* All the routers (except for Linux) return only
   8 bytes of packet payload. It means, that precise relaying of
   ICMP in the real Internet is absolutely infeasible.
 */
        struct net *net = dev_net(skb->dev);
        struct ip_tunnel_net *itn = net_generic(net, ipip_net_id);
        const struct iphdr *iph = (const struct iphdr *)skb->data;
        struct ip_tunnel *t;
        int err;
        const int type = icmp_hdr(skb)->type;
        const int code = icmp_hdr(skb)->code;

        err = -ENOENT;
        t = ip_tunnel_lookup(itn, skb->dev->ifindex, TUNNEL_NO_KEY,
                             iph->daddr, iph->saddr, 0);
        if (!t)
                goto out;

        if (type == ICMP_DEST_UNREACH && code == ICMP_FRAG_NEEDED) {
                ipv4_update_pmtu(skb, dev_net(skb->dev), info,
                                 t->parms.link, 0, iph->protocol, 0);
                err = 0;
                goto out;
        }

        if (type == ICMP_REDIRECT) {
                ipv4_redirect(skb, dev_net(skb->dev), t->parms.link, 0,
                              iph->protocol, 0);
                err = 0;
                goto out;
        }

        if (t->parms.iph.daddr == 0)
                goto out;

        err = 0;
        if (t->parms.iph.ttl == 0 && type == ICMP_TIME_EXCEEDED)
                goto out;

        if (time_before(jiffies, t->err_time + IPTUNNEL_ERR_TIMEO))
                t->err_count++;
        else
                t->err_count = 1;
        t->err_time = jiffies;

out:
        return err;
}

static const struct tnl_ptk_info ipip_tpi = {
        /* no tunnel info required for ipip. */
        .proto = htons(ETH_P_IP),
};

#if IS_ENABLED(CONFIG_MPLS)
static const struct tnl_ptk_info mplsip_tpi = {
        /* no tunnel info required for mplsip. */
        .proto = htons(ETH_P_MPLS_UC),
};
#endif

static int ipip_tunnel_rcv(struct sk_buff *skb, u8 ipproto)
{
        struct net *net = dev_net(skb->dev);
        struct ip_tunnel_net *itn = net_generic(net, ipip_net_id);
        struct metadata_dst *tun_dst = NULL;
        struct ip_tunnel *tunnel;
        const struct iphdr *iph;

        iph = ip_hdr(skb);
        tunnel = ip_tunnel_lookup(itn, skb->dev->ifindex, TUNNEL_NO_KEY,
                        iph->saddr, iph->daddr, 0);
        if (tunnel) {
                const struct tnl_ptk_info *tpi;

                if (tunnel->parms.iph.protocol != ipproto &&
                    tunnel->parms.iph.protocol != 0)
                        goto drop;

                if (!xfrm4_policy_check(NULL, XFRM_POLICY_IN, skb))
                        goto drop;
#if IS_ENABLED(CONFIG_MPLS)
                if (ipproto == IPPROTO_MPLS)
                        tpi = &mplsip_tpi;
                else
#endif
                        tpi = &ipip_tpi;
                if (iptunnel_pull_header(skb, 0, tpi->proto, false))
                        goto drop;
                if (tunnel->collect_md) {
                        tun_dst = ip_tun_rx_dst(skb, 0, 0, 0);
                        if (!tun_dst)
                                return 0;
                }
                return ip_tunnel_rcv(tunnel, skb, tpi, tun_dst, log_ecn_error);
        }

        return -1;

drop:
        kfree_skb(skb);
        return 0;
}

static int ipip_rcv(struct sk_buff *skb)
{
        return ipip_tunnel_rcv(skb, IPPROTO_IPIP);
}

#if IS_ENABLED(CONFIG_MPLS)
static int mplsip_rcv(struct sk_buff *skb)
{
        return ipip_tunnel_rcv(skb, IPPROTO_MPLS);
}
#endif

static struct ip_fan_map *ipip_fan_find_map(struct ip_tunnel *t, __be32 daddr)
{
        struct ip_fan_map *fan_map;

        rcu_read_lock();
        list_for_each_entry_rcu(fan_map, &t->fan.fan_maps, list) {
                if (fan_map->overlay ==
                    (daddr & inet_make_mask(fan_map->overlay_prefix))) {
                        rcu_read_unlock();
                        return fan_map;
                }
        }
        rcu_read_unlock();

        return NULL;
}

/* Determine fan tunnel endpoint to send packet to, based on the inner IP
 * address.  
 *
 * Given a /8 overlay and /16 underlay, for an overlay (inner) address
 * Y.A.B.C, the transformation is F.G.A.B, where "F" and "G" are the first
 * two octets of the underlay network (the network portion of a /16), "A"
 * and "B" are the low order two octets of the underlay network host (the
 * host portion of a /16), and "Y" is a configured first octet of the
 * overlay network.
 *
 * E.g., underlay host 10.88.3.4/16 with an overlay of 99.0.0.0/8 would
 * host overlay subnet 99.3.4.0/24.  An overlay network datagram from
 * 99.3.4.5 to 99.6.7.8, would be directed to underlay host 10.88.6.7,
 * which hosts overlay network subnet 99.6.7.0/24.  This transformation is
 * described in detail further below.
 *
 * Using netmasks for the overlay and underlay other than /8 and /16, as
 * shown above, can yield larger (or smaller) overlay subnets, with the
 * trade-off of allowing fewer (or more) underlay hosts to participate.
 *
 * The size of each overlay network subnet is defined by the total of the
 * network mask of the overlay plus the size of host portion of the
 * underlay network. In the above example, /8 + /16 = /24.
 *
 * E.g., consider underlay host 10.99.238.5/20 and overlay 99.0.0.0/8. In
 * this case, the network portion of the underlay is 10.99.224.0/20, and
 * the host portion is 0.0.14.5 (12 bits).  To determine the overlay
 * network subnet, the 12 bits of host portion are left shifted 12 bits
 * (/20 - /8) and ORed with the overlay subnet prefix.  This yields an
 * overlay subnet of 99.224.80/20, composed of 8 bits overlay, followed by
 * 12 bits underlay.  This yields 12 bits in the overlay network portion,
 * allowing for 4094 addresses in each overlay network subnet.  The
 * trade-off is that fewer hosts may participate in the underlay network,
 * as its host address size has shrunk from 16 bits (65534 addresses) in
 * the first example to 12 bits (4094 addresses) here.
 *
 * For fewer hosts per overlay subnet (permitting a larger number of
 * underlay hosts to participate), the underlay netmask may be made
 * smaller.
 *
 * E.g., underlay host 10.111.1.2/12 (network 10.96.0.0/12, host portion
 * is 0.15.1.2, 20 bits) with an overlay of 33.0.0.0/8 would left shift
 * the 20 bits of host by 4 (so that it's highest order bit is adjacent to
 * the lowest order bit of the /8 overlay).  This yields an overlay subnet
 * of 33.240.16.32/28 (8 bits overlay, 20 bits from the host portion of
 * the underlay).  This provides more addresses for the underlay network
 * (approximately 2^20), but each host's segment of the overlay provides
 * only 4 bits of addresses (14 usable).
 *
 * It is also possible to adjust the overlay subnet.
 *
 * For an overlay of 240.0.0.0/5 and underlay of 10.88.0.0/20, consider
 * underlay host 10.88.129.2; the 12 bits of host, 0.0.1.2, are left
 * shifted 15 bits (/20 - /5), yielding an overlay network of
 * 240.129.0.0/17.  An underlay host of 10.88.244.215 would yield an
 * overlay network of 242.107.128.0/17.
 *
 * For an overlay of 100.64.0.0/10 and underlay of 10.224.220.0/24, for
 * underlay host 10.224.220.10, the underlay host portion (.10) is left
 * shifted 14 bits, yielding an overlay network subnet of 100.66.128.0/18.
 * This would permit 254 addresses on the underlay, with each overlay
 * segment providing approximately 2^14 - 2 addresses (16382).
 *
 * For packets being encapsulated, the overlay network destination IP
 * address is deconstructed into its overlay and underlay-derived
 * portions.  The underlay portion (determined by the overlay mask and
 * overlay subnet mask) is right shifted according to the size of the
 * underlay network mask.  This value is then ORed with the network
 * portion of the underlay network to produce the underlay network
 * destination for the encapsulated datagram.
 *
 * For example, using the initial example of underlay 10.88.3.4/16 and
 * overlay 99.0.0.0/8, with underlay host 10.88.3.4/16 providing overlay
 * subnet 99.3.4.0/24 with specfic host 99.3.4.5.  A datagram from
 * 99.3.4.5 to 99.6.7.8 would first have the underlay host derived portion
 * of the address extracted.  This is a number of bits equal to underlay
 * network host portion.  In the destination address, the highest order of
 * these bits is one bit lower than the lowest order bit from the overlay
 * network mask.
 *
 * Using the sample value, 99.6.7.8, the overlay mask is /8, and the
 * underlay mask is /16 (leaving 16 bits for the host portion).  The bits
 * to be shifted are the middle two octets, 0.6.7.0, as this is 99.6.7.8
 * ANDed with the mask 0x00ffff00 (which is 16 bits, the highest order of
 * which is 1 bit lower than the lowest order overlay address bit).
 *
 * These octets, 0.6.7.0, are then right shifted 8 bits, yielding 0.0.6.7.
 * This value is then ORed with the underlay network portion,
 * 10.88.0.0/16, providing 10.88.6.7 as the final underlay destination for
 * the encapuslated datagram.
 *
 * Another transform using the final example: overlay 100.64.0.0/10 and
 * underlay 10.224.220.0/24.  Consider overlay address 100.66.128.1
 * sending a datagram to 100.66.200.5.  In this case, 8 bits (the host
 * portion size of 10.224.220.0/24) beginning after the 100.64/10 overlay
 * prefix are masked off, yielding 0.2.192.0.  This is right shifted 14
 * (32 - 10 - (32 - 24), i.e., the number of bits between the overlay
 * network portion and the underlay host portion) bits, yielding 0.0.0.11.
 * This is ORed with the underlay network portion, 10.224.220.0/24, giving
 * the underlay destination of 10.224.220.11 for overlay destination
 * 100.66.200.5.
 */
static int ipip_build_fan_iphdr(struct ip_tunnel *tunnel, struct sk_buff *skb, struct iphdr *iph)
{
        struct ip_fan_map *f_map;
        u32 daddr, underlay;

        f_map = ipip_fan_find_map(tunnel, ip_hdr(skb)->daddr);
        if (!f_map)
                return -ENOENT;

        daddr = ntohl(ip_hdr(skb)->daddr);
        underlay = ntohl(f_map->underlay);
        if (!underlay)
                return -EINVAL;

        *iph = tunnel->parms.iph;
        iph->daddr = htonl(underlay |
                           ((daddr & ~f_map->overlay_mask) >>
                            (32 - f_map->overlay_prefix -
                             (32 - f_map->underlay_prefix))));
        return 0;
}

/*
 *      This function assumes it is being called from dev_queue_xmit()
 *      and that skb is filled properly by that function.
 */
static netdev_tx_t ipip_tunnel_xmit(struct sk_buff *skb,
                                    struct net_device *dev)
{
        struct ip_tunnel *tunnel = netdev_priv(dev);
        const struct iphdr  *tiph = &tunnel->parms.iph;
        u8 ipproto;
        struct iphdr fiph;

        switch (skb->protocol) {
        case htons(ETH_P_IP):
                ipproto = IPPROTO_IPIP;
                break;
#if IS_ENABLED(CONFIG_MPLS)
        case htons(ETH_P_MPLS_UC):
                ipproto = IPPROTO_MPLS;
                break;
#endif
        default:
                goto tx_error;
        }

        if (tiph->protocol != ipproto && tiph->protocol != 0)
                goto tx_error;

        if (iptunnel_handle_offloads(skb, SKB_GSO_IPXIP4))
                goto tx_error;

        if (fan_has_map(&tunnel->fan)) {
                if (ipip_build_fan_iphdr(tunnel, skb, &fiph))
                        goto tx_error;
                tiph = &fiph;
        } else {
                tiph = &tunnel->parms.iph;
        }

        skb_set_inner_ipproto(skb, ipproto);

        if (tunnel->collect_md)
                ip_md_tunnel_xmit(skb, dev, ipproto);
        else
                ip_tunnel_xmit(skb, dev, tiph, ipproto);
        return NETDEV_TX_OK;

tx_error:
        kfree_skb(skb);

        dev->stats.tx_errors++;
        return NETDEV_TX_OK;
}

static bool ipip_tunnel_ioctl_verify_protocol(u8 ipproto)
{
        switch (ipproto) {
        case 0:
        case IPPROTO_IPIP:
#if IS_ENABLED(CONFIG_MPLS)
        case IPPROTO_MPLS:
#endif
                return true;
        }

        return false;
}

static int
ipip_tunnel_ioctl(struct net_device *dev, struct ifreq *ifr, int cmd)
{
        int err = 0;
        struct ip_tunnel_parm p;

        if (copy_from_user(&p, ifr->ifr_ifru.ifru_data, sizeof(p)))
                return -EFAULT;

        if (cmd == SIOCADDTUNNEL || cmd == SIOCCHGTUNNEL) {
                if (p.iph.version != 4 ||
                    !ipip_tunnel_ioctl_verify_protocol(p.iph.protocol) ||
                    p.iph.ihl != 5 || (p.iph.frag_off&htons(~IP_DF)))
                        return -EINVAL;
        }

        p.i_key = p.o_key = 0;
        p.i_flags = p.o_flags = 0;
        err = ip_tunnel_ioctl(dev, &p, cmd);
        if (err)
                return err;

        if (copy_to_user(ifr->ifr_ifru.ifru_data, &p, sizeof(p)))
                return -EFAULT;

        return 0;
}

static const struct net_device_ops ipip_netdev_ops = {
        .ndo_init       = ipip_tunnel_init,
        .ndo_uninit     = ip_tunnel_uninit,
        .ndo_start_xmit = ipip_tunnel_xmit,
        .ndo_do_ioctl   = ipip_tunnel_ioctl,
        .ndo_change_mtu = ip_tunnel_change_mtu,
        .ndo_get_stats64 = ip_tunnel_get_stats64,
        .ndo_get_iflink = ip_tunnel_get_iflink,
};

#define IPIP_FEATURES (NETIF_F_SG |             \
                       NETIF_F_FRAGLIST |       \
                       NETIF_F_HIGHDMA |        \
                       NETIF_F_GSO_SOFTWARE |   \
                       NETIF_F_HW_CSUM)

static void ipip_tunnel_setup(struct net_device *dev)
{
        struct ip_tunnel *t = netdev_priv(dev);

        dev->netdev_ops         = &ipip_netdev_ops;

        dev->type               = ARPHRD_TUNNEL;
        dev->flags              = IFF_NOARP;
        dev->addr_len           = 4;
        dev->features           |= NETIF_F_LLTX;
        netif_keep_dst(dev);

        dev->features           |= IPIP_FEATURES;
        dev->hw_features        |= IPIP_FEATURES;
        ip_tunnel_setup(dev, ipip_net_id);
        INIT_LIST_HEAD(&t->fan.fan_maps);
}

static int ipip_tunnel_init(struct net_device *dev)
{
        struct ip_tunnel *tunnel = netdev_priv(dev);

        memcpy(dev->dev_addr, &tunnel->parms.iph.saddr, 4);
        memcpy(dev->broadcast, &tunnel->parms.iph.daddr, 4);

        tunnel->tun_hlen = 0;
        tunnel->hlen = tunnel->tun_hlen + tunnel->encap_hlen;
        return ip_tunnel_init(dev);
}

static int ipip_tunnel_validate(struct nlattr *tb[], struct nlattr *data[],
                                struct netlink_ext_ack *extack)
{
        u8 proto;

        if (!data || !data[IFLA_IPTUN_PROTO])
                return 0;

        proto = nla_get_u8(data[IFLA_IPTUN_PROTO]);
        if (proto != IPPROTO_IPIP && proto != IPPROTO_MPLS && proto != 0)
                return -EINVAL;

        return 0;
}

static void ipip_netlink_parms(struct nlattr *data[],
                               struct ip_tunnel_parm *parms, bool *collect_md,
                               __u32 *fwmark)
{
        memset(parms, 0, sizeof(*parms));

        parms->iph.version = 4;
        parms->iph.protocol = IPPROTO_IPIP;
        parms->iph.ihl = 5;
        *collect_md = false;

        if (!data)
                return;

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

        if (data[IFLA_IPTUN_LOCAL])
                parms->iph.saddr = nla_get_in_addr(data[IFLA_IPTUN_LOCAL]);

        if (data[IFLA_IPTUN_REMOTE])
                parms->iph.daddr = nla_get_in_addr(data[IFLA_IPTUN_REMOTE]);

        if (data[IFLA_IPTUN_TTL]) {
                parms->iph.ttl = nla_get_u8(data[IFLA_IPTUN_TTL]);
                if (parms->iph.ttl)
                        parms->iph.frag_off = htons(IP_DF);
        }

        if (data[IFLA_IPTUN_TOS])
                parms->iph.tos = nla_get_u8(data[IFLA_IPTUN_TOS]);

        if (data[IFLA_IPTUN_PROTO])
                parms->iph.protocol = nla_get_u8(data[IFLA_IPTUN_PROTO]);

        if (!data[IFLA_IPTUN_PMTUDISC] || nla_get_u8(data[IFLA_IPTUN_PMTUDISC]))
                parms->iph.frag_off = htons(IP_DF);

        if (data[IFLA_IPTUN_COLLECT_METADATA])
                *collect_md = true;

        if (data[IFLA_IPTUN_FWMARK])
                *fwmark = nla_get_u32(data[IFLA_IPTUN_FWMARK]);
}

/* This function returns true when ENCAP attributes are present in the nl msg */
static bool ipip_netlink_encap_parms(struct nlattr *data[],
                                     struct ip_tunnel_encap *ipencap)
{
        bool ret = false;

        memset(ipencap, 0, sizeof(*ipencap));

        if (!data)
                return ret;

        if (data[IFLA_IPTUN_ENCAP_TYPE]) {
                ret = true;
                ipencap->type = nla_get_u16(data[IFLA_IPTUN_ENCAP_TYPE]);
        }

        if (data[IFLA_IPTUN_ENCAP_FLAGS]) {
                ret = true;
                ipencap->flags = nla_get_u16(data[IFLA_IPTUN_ENCAP_FLAGS]);
        }

        if (data[IFLA_IPTUN_ENCAP_SPORT]) {
                ret = true;
                ipencap->sport = nla_get_be16(data[IFLA_IPTUN_ENCAP_SPORT]);
        }

        if (data[IFLA_IPTUN_ENCAP_DPORT]) {
                ret = true;
                ipencap->dport = nla_get_be16(data[IFLA_IPTUN_ENCAP_DPORT]);
        }

        return ret;
}

static void ipip_fan_flush_map(struct ip_tunnel *t)
{
        struct ip_fan_map *fan_map;

        list_for_each_entry_rcu(fan_map, &t->fan.fan_maps, list) {
                list_del_rcu(&fan_map->list);
                kfree_rcu(fan_map, rcu);
        }
}

static int ipip_fan_del_map(struct ip_tunnel *t, __be32 overlay)
{
        struct ip_fan_map *fan_map;

        fan_map = ipip_fan_find_map(t, overlay);
        if (!fan_map)
                return -ENOENT;

        list_del_rcu(&fan_map->list);
        kfree_rcu(fan_map, rcu);

        return 0;
}

static int ipip_fan_add_map(struct ip_tunnel *t, struct ifla_fan_map *map)
{
        __be32 overlay_mask, underlay_mask;
        struct ip_fan_map *fan_map;

        overlay_mask = inet_make_mask(map->overlay_prefix);
        underlay_mask = inet_make_mask(map->underlay_prefix);

        if ((map->overlay & ~overlay_mask) || (map->underlay & ~underlay_mask))
                return -EINVAL;

        if (!(map->overlay & overlay_mask) && (map->underlay & underlay_mask))
                return -EINVAL;

        /* Special case: overlay 0 and underlay 0: flush all mappings */
        if (!map->overlay && !map->underlay) {
                ipip_fan_flush_map(t);
                return 0;
        }
        
        /* Special case: overlay set and underlay 0: clear map for overlay */
        if (!map->underlay)
                return ipip_fan_del_map(t, map->overlay);

        if (ipip_fan_find_map(t, map->overlay))
                return -EEXIST;

        fan_map = kmalloc(sizeof(*fan_map), GFP_KERNEL);
        fan_map->underlay = map->underlay;
        fan_map->overlay = map->overlay;
        fan_map->underlay_prefix = map->underlay_prefix;
        fan_map->overlay_mask = ntohl(overlay_mask);
        fan_map->overlay_prefix = map->overlay_prefix;

        list_add_tail_rcu(&fan_map->list, &t->fan.fan_maps);

        return 0;
}
        

static int ipip_netlink_fan(struct nlattr *data[], struct ip_tunnel *t,
                            struct ip_tunnel_parm *parms)
{
        struct ifla_fan_map *map;
        struct nlattr *attr;
        int rem, rv;

        if (!data[IFLA_IPTUN_FAN_MAP])
                return 0;

        if (parms->iph.daddr)
                return -EINVAL;

        nla_for_each_nested(attr, data[IFLA_IPTUN_FAN_MAP], rem) {
                map = nla_data(attr);
                rv = ipip_fan_add_map(t, map);
                if (rv)
                        return rv;
        }

        return 0;
}

static int ipip_newlink(struct net *src_net, struct net_device *dev,
                        struct nlattr *tb[], struct nlattr *data[],
                        struct netlink_ext_ack *extack)
{
        struct ip_tunnel *t = netdev_priv(dev);
        struct ip_tunnel_parm p;
        struct ip_tunnel_encap ipencap;
        __u32 fwmark = 0;
        int err;

        if (ipip_netlink_encap_parms(data, &ipencap)) {
                err = ip_tunnel_encap_setup(t, &ipencap);

                if (err < 0)
                        return err;
        }

        ipip_netlink_parms(data, &p, &t->collect_md, &fwmark);
        err = ipip_netlink_fan(data, t, &p);
        if (err < 0)
                return err;
        return ip_tunnel_newlink(dev, tb, &p, fwmark);
}

static int ipip_changelink(struct net_device *dev, struct nlattr *tb[],
                           struct nlattr *data[],
                           struct netlink_ext_ack *extack)
{
        struct ip_tunnel *t = netdev_priv(dev);
        struct ip_tunnel_parm p;
        struct ip_tunnel_encap ipencap;
        bool collect_md;
        __u32 fwmark = t->fwmark;
        int err;

        if (ipip_netlink_encap_parms(data, &ipencap)) {
                err = ip_tunnel_encap_setup(t, &ipencap);

                if (err < 0)
                        return err;
        }

        ipip_netlink_parms(data, &p, &collect_md, &fwmark);
        if (collect_md)
                return -EINVAL;
        err = ipip_netlink_fan(data, t, &p);
        if (err < 0)
                return err;

        if (((dev->flags & IFF_POINTOPOINT) && !p.iph.daddr) ||
            (!(dev->flags & IFF_POINTOPOINT) && p.iph.daddr))
                return -EINVAL;

        return ip_tunnel_changelink(dev, tb, &p, fwmark);
}

static size_t ipip_get_size(const struct net_device *dev)
{
        return
                /* IFLA_IPTUN_LINK */
                nla_total_size(4) +
                /* IFLA_IPTUN_LOCAL */
                nla_total_size(4) +
                /* IFLA_IPTUN_REMOTE */
                nla_total_size(4) +
                /* IFLA_IPTUN_TTL */
                nla_total_size(1) +
                /* IFLA_IPTUN_TOS */
                nla_total_size(1) +
                /* IFLA_IPTUN_PROTO */
                nla_total_size(1) +
                /* IFLA_IPTUN_PMTUDISC */
                nla_total_size(1) +
                /* IFLA_IPTUN_ENCAP_TYPE */
                nla_total_size(2) +
                /* IFLA_IPTUN_ENCAP_FLAGS */
                nla_total_size(2) +
                /* IFLA_IPTUN_ENCAP_SPORT */
                nla_total_size(2) +
                /* IFLA_IPTUN_ENCAP_DPORT */
                nla_total_size(2) +
                /* IFLA_IPTUN_COLLECT_METADATA */
                nla_total_size(0) +
                /* IFLA_IPTUN_FWMARK */
                nla_total_size(4) +
                /* IFLA_IPTUN_FAN_MAP */
                nla_total_size(sizeof(struct ifla_fan_map)) * 256 +
                0;
}

static int ipip_fill_info(struct sk_buff *skb, const struct net_device *dev)
{
        struct ip_tunnel *tunnel = netdev_priv(dev);
        struct ip_tunnel_parm *parm = &tunnel->parms;

        if (nla_put_u32(skb, IFLA_IPTUN_LINK, parm->link) ||
            nla_put_in_addr(skb, IFLA_IPTUN_LOCAL, parm->iph.saddr) ||
            nla_put_in_addr(skb, IFLA_IPTUN_REMOTE, parm->iph.daddr) ||
            nla_put_u8(skb, IFLA_IPTUN_TTL, parm->iph.ttl) ||
            nla_put_u8(skb, IFLA_IPTUN_TOS, parm->iph.tos) ||
            nla_put_u8(skb, IFLA_IPTUN_PROTO, parm->iph.protocol) ||
            nla_put_u8(skb, IFLA_IPTUN_PMTUDISC,
                       !!(parm->iph.frag_off & htons(IP_DF))) ||
            nla_put_u32(skb, IFLA_IPTUN_FWMARK, tunnel->fwmark))
                goto nla_put_failure;

        if (nla_put_u16(skb, IFLA_IPTUN_ENCAP_TYPE,
                        tunnel->encap.type) ||
            nla_put_be16(skb, IFLA_IPTUN_ENCAP_SPORT,
                         tunnel->encap.sport) ||
            nla_put_be16(skb, IFLA_IPTUN_ENCAP_DPORT,
                         tunnel->encap.dport) ||
            nla_put_u16(skb, IFLA_IPTUN_ENCAP_FLAGS,
                        tunnel->encap.flags))
                goto nla_put_failure;

        if (tunnel->collect_md)
                if (nla_put_flag(skb, IFLA_IPTUN_COLLECT_METADATA))
                        goto nla_put_failure;
        if (fan_has_map(&tunnel->fan)) {
                struct nlattr *fan_nest;
                struct ip_fan_map *fan_map;

                fan_nest = nla_nest_start(skb, IFLA_IPTUN_FAN_MAP);
                if (!fan_nest)
                        goto nla_put_failure;
                list_for_each_entry_rcu(fan_map, &tunnel->fan.fan_maps, list) {
                        struct ifla_fan_map map;

                        map.underlay = fan_map->underlay;
                        map.underlay_prefix = fan_map->underlay_prefix;
                        map.overlay = fan_map->overlay;
                        map.overlay_prefix = fan_map->overlay_prefix;
                        if (nla_put(skb, IFLA_FAN_MAPPING, sizeof(map), &map))
                                goto nla_put_failure;
                }
                nla_nest_end(skb, fan_nest);
        }

        return 0;

nla_put_failure:
        return -EMSGSIZE;
}

static const struct nla_policy ipip_policy[IFLA_IPTUN_MAX + 1] = {
        [IFLA_IPTUN_LINK]               = { .type = NLA_U32 },
        [IFLA_IPTUN_LOCAL]              = { .type = NLA_U32 },
        [IFLA_IPTUN_REMOTE]             = { .type = NLA_U32 },
        [IFLA_IPTUN_TTL]                = { .type = NLA_U8 },
        [IFLA_IPTUN_TOS]                = { .type = NLA_U8 },
        [IFLA_IPTUN_PROTO]              = { .type = NLA_U8 },
        [IFLA_IPTUN_PMTUDISC]           = { .type = NLA_U8 },
        [IFLA_IPTUN_ENCAP_TYPE]         = { .type = NLA_U16 },
        [IFLA_IPTUN_ENCAP_FLAGS]        = { .type = NLA_U16 },
        [IFLA_IPTUN_ENCAP_SPORT]        = { .type = NLA_U16 },
        [IFLA_IPTUN_ENCAP_DPORT]        = { .type = NLA_U16 },
        [IFLA_IPTUN_COLLECT_METADATA]   = { .type = NLA_FLAG },
        [IFLA_IPTUN_FWMARK]             = { .type = NLA_U32 },

        [__IFLA_IPTUN_VENDOR_BREAK ... IFLA_IPTUN_MAX]  = { .type = NLA_BINARY },
        [IFLA_IPTUN_FAN_MAP]            = { .type = NLA_NESTED },
};

static struct rtnl_link_ops ipip_link_ops __read_mostly = {
        .kind           = "ipip",
        .maxtype        = IFLA_IPTUN_MAX,
        .policy         = ipip_policy,
        .priv_size      = sizeof(struct ip_tunnel),
        .setup          = ipip_tunnel_setup,
        .validate       = ipip_tunnel_validate,
        .newlink        = ipip_newlink,
        .changelink     = ipip_changelink,
        .dellink        = ip_tunnel_dellink,
        .get_size       = ipip_get_size,
        .fill_info      = ipip_fill_info,
        .get_link_net   = ip_tunnel_get_link_net,
};

static struct xfrm_tunnel ipip_handler __read_mostly = {
        .handler        =       ipip_rcv,
        .err_handler    =       ipip_err,
        .priority       =       1,
};

#if IS_ENABLED(CONFIG_MPLS)
static struct xfrm_tunnel mplsip_handler __read_mostly = {
        .handler        =       mplsip_rcv,
        .err_handler    =       ipip_err,
        .priority       =       1,
};
#endif

static int __net_init ipip_init_net(struct net *net)
{
        return ip_tunnel_init_net(net, ipip_net_id, &ipip_link_ops, "tunl0");
}

static void __net_exit ipip_exit_net(struct net *net)
{
        struct ip_tunnel_net *itn = net_generic(net, ipip_net_id);
        ip_tunnel_delete_net(itn, &ipip_link_ops);
}

static struct pernet_operations ipip_net_ops = {
        .init = ipip_init_net,
        .exit = ipip_exit_net,
        .id   = &ipip_net_id,
        .size = sizeof(struct ip_tunnel_net),
};

#ifdef CONFIG_SYSCTL
static struct ctl_table_header *ipip_fan_header;
static unsigned int ipip_fan_version = 3;

static struct ctl_table ipip_fan_sysctls[] = {
        {
                .procname       = "version",
                .data           = &ipip_fan_version,
                .maxlen         = sizeof(ipip_fan_version),
                .mode           = 0444,
                .proc_handler   = proc_dointvec,
        },
        {},
};

#endif /* CONFIG_SYSCTL */

static int __init ipip_init(void)
{
        int err;

        pr_info("ipip: IPv4 and MPLS over IPv4 tunneling driver\n");

        err = register_pernet_device(&ipip_net_ops);
        if (err < 0)
                return err;
        err = xfrm4_tunnel_register(&ipip_handler, AF_INET);
        if (err < 0) {
                pr_info("%s: can't register tunnel\n", __func__);
                goto xfrm_tunnel_ipip_failed;
        }
#if IS_ENABLED(CONFIG_MPLS)
        err = xfrm4_tunnel_register(&mplsip_handler, AF_MPLS);
        if (err < 0) {
                pr_info("%s: can't register tunnel\n", __func__);
                goto xfrm_tunnel_mplsip_failed;
        }
#endif
        err = rtnl_link_register(&ipip_link_ops);
        if (err < 0)
                goto rtnl_link_failed;

#ifdef CONFIG_SYSCTL
        ipip_fan_header = register_net_sysctl(&init_net, "net/fan",
                                              ipip_fan_sysctls);
        if (!ipip_fan_header) {
                err = -ENOMEM;
                goto sysctl_failed;
        }
#endif /* CONFIG_SYSCTL */

out:
        return err;

#ifdef CONFIG_SYSCTL
sysctl_failed:
        rtnl_link_unregister(&ipip_link_ops);
#endif /* CONFIG_SYSCTL */
rtnl_link_failed:
#if IS_ENABLED(CONFIG_MPLS)
        xfrm4_tunnel_deregister(&mplsip_handler, AF_INET);
xfrm_tunnel_mplsip_failed:

#endif
        xfrm4_tunnel_deregister(&ipip_handler, AF_INET);
xfrm_tunnel_ipip_failed:
        unregister_pernet_device(&ipip_net_ops);
        goto out;
}

static void __exit ipip_fini(void)
{
#ifdef CONFIG_SYSCTL
        unregister_net_sysctl_table(ipip_fan_header);
#endif /* CONFIG_SYSCTL */
        rtnl_link_unregister(&ipip_link_ops);
        if (xfrm4_tunnel_deregister(&ipip_handler, AF_INET))
                pr_info("%s: can't deregister tunnel\n", __func__);
#if IS_ENABLED(CONFIG_MPLS)
        if (xfrm4_tunnel_deregister(&mplsip_handler, AF_MPLS))
                pr_info("%s: can't deregister tunnel\n", __func__);
#endif
        unregister_pernet_device(&ipip_net_ops);
}

module_init(ipip_init);
module_exit(ipip_fini);
MODULE_LICENSE("GPL");
MODULE_ALIAS_RTNL_LINK("ipip");
MODULE_ALIAS_NETDEV("tunl0");