mip6.c

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/*
 * Copyright (C)2003-2006 Helsinki University of Technology
 * Copyright (C)2003-2006 USAGI/WIDE Project
 *
 * 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.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */
/*
 * Authors:
 *  Noriaki TAKAMIYA @USAGI
 *  Masahide NAKAMURA @USAGI
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/module.h>
#include <linux/skbuff.h>
#include <linux/time.h>
#include <linux/ipv6.h>
#include <linux/icmpv6.h>
#include <net/sock.h>
#include <net/ipv6.h>
#include <net/ip6_checksum.h>
#include <net/rawv6.h>
#include <net/xfrm.h>
#include <net/mip6.h>

static inline unsigned int calc_padlen(unsigned int len, unsigned int n)
{
    return (n - len + 16) & 0x7;
}

static inline void *mip6_padn(__u8 *data, __u8 padlen)
{
    if (!data)
        return NULL;
    if (padlen == 1) {
        data[0] = IPV6_TLV_PAD1;
    } else if (padlen > 1) {
        data[0] = IPV6_TLV_PADN;
        data[1] = padlen - 2;
        if (padlen > 2)
            memset(data+2, 0, data[1]);
    }
    return data + padlen;
}

static inline void mip6_param_prob(struct sk_buff *skb, u8 code, int pos)
{
    icmpv6_send(skb, ICMPV6_PARAMPROB, code, pos);
}

static int mip6_mh_len(int type)
{
    int len = 0;

    switch (type) {
    case IP6_MH_TYPE_BRR:
        len = 0;
        break;
    case IP6_MH_TYPE_HOTI:
    case IP6_MH_TYPE_COTI:
    case IP6_MH_TYPE_BU:
    case IP6_MH_TYPE_BACK:
        len = 1;
        break;
    case IP6_MH_TYPE_HOT:
    case IP6_MH_TYPE_COT:
    case IP6_MH_TYPE_BERROR:
        len = 2;
        break;
    }
    return len;
}

static int mip6_mh_filter(struct sock *sk, struct sk_buff *skb)
{
    struct ip6_mh _hdr;
    const struct ip6_mh *mh;

    mh = skb_header_pointer(skb, skb_transport_offset(skb),
                sizeof(_hdr), &_hdr);
    if (!mh)
        return -1;

    if (((mh->ip6mh_hdrlen + 1) << 3) > skb->len)
        return -1;

    if (mh->ip6mh_hdrlen < mip6_mh_len(mh->ip6mh_type)) {
        LIMIT_NETDEBUG(KERN_DEBUG "mip6: MH message too short: %d vs >=%d\n",
                   mh->ip6mh_hdrlen, mip6_mh_len(mh->ip6mh_type));
        mip6_param_prob(skb, 0, offsetof(struct ip6_mh, ip6mh_hdrlen) +
                skb_network_header_len(skb));
        return -1;
    }

    if (mh->ip6mh_proto != IPPROTO_NONE) {
        LIMIT_NETDEBUG(KERN_DEBUG "mip6: MH invalid payload proto = %d\n",
                   mh->ip6mh_proto);
        mip6_param_prob(skb, 0, offsetof(struct ip6_mh, ip6mh_proto) +
                skb_network_header_len(skb));
        return -1;
    }

    return 0;
}

struct mip6_report_rate_limiter {
    spinlock_t lock;
    struct timeval stamp;
    int iif;
    struct in6_addr src;
    struct in6_addr dst;
};

static struct mip6_report_rate_limiter mip6_report_rl = {
    .lock = __SPIN_LOCK_UNLOCKED(mip6_report_rl.lock)
};

static int mip6_destopt_input(struct xfrm_state *x, struct sk_buff *skb)
{
    const struct ipv6hdr *iph = ipv6_hdr(skb);
    struct ipv6_destopt_hdr *destopt = (struct ipv6_destopt_hdr *)skb->data;
    int err = destopt->nexthdr;

    spin_lock(&x->lock);
    if (!ipv6_addr_equal(&iph->saddr, (struct in6_addr *)x->coaddr) &&
        !ipv6_addr_any((struct in6_addr *)x->coaddr))
        err = -ENOENT;
    spin_unlock(&x->lock);

    return err;
}

/* Destination Option Header is inserted.
 * IP Header's src address is replaced with Home Address Option in
 * Destination Option Header.
 */
static int mip6_destopt_output(struct xfrm_state *x, struct sk_buff *skb)
{
    struct ipv6hdr *iph;
    struct ipv6_destopt_hdr *dstopt;
    struct ipv6_destopt_hao *hao;
    u8 nexthdr;
    int len;

    skb_push(skb, -skb_network_offset(skb));
    iph = ipv6_hdr(skb);

    nexthdr = *skb_mac_header(skb);
    *skb_mac_header(skb) = IPPROTO_DSTOPTS;

    dstopt = (struct ipv6_destopt_hdr *)skb_transport_header(skb);
    dstopt->nexthdr = nexthdr;

    hao = mip6_padn((char *)(dstopt + 1),
            calc_padlen(sizeof(*dstopt), 6));

    hao->type = IPV6_TLV_HAO;
    BUILD_BUG_ON(sizeof(*hao) != 18);
    hao->length = sizeof(*hao) - 2;

    len = ((char *)hao - (char *)dstopt) + sizeof(*hao);

    memcpy(&hao->addr, &iph->saddr, sizeof(hao->addr));
    spin_lock_bh(&x->lock);
    memcpy(&iph->saddr, x->coaddr, sizeof(iph->saddr));
    spin_unlock_bh(&x->lock);

    WARN_ON(len != x->props.header_len);
    dstopt->hdrlen = (x->props.header_len >> 3) - 1;

    return 0;
}

static inline int mip6_report_rl_allow(struct timeval *stamp,
                       const struct in6_addr *dst,
                       const struct in6_addr *src, int iif)
{
    int allow = 0;

    spin_lock_bh(&mip6_report_rl.lock);
    if (mip6_report_rl.stamp.tv_sec != stamp->tv_sec ||
        mip6_report_rl.stamp.tv_usec != stamp->tv_usec ||
        mip6_report_rl.iif != iif ||
        !ipv6_addr_equal(&mip6_report_rl.src, src) ||
        !ipv6_addr_equal(&mip6_report_rl.dst, dst)) {
        mip6_report_rl.stamp.tv_sec = stamp->tv_sec;
        mip6_report_rl.stamp.tv_usec = stamp->tv_usec;
        mip6_report_rl.iif = iif;
        mip6_report_rl.src = *src;
        mip6_report_rl.dst = *dst;
        allow = 1;
    }
    spin_unlock_bh(&mip6_report_rl.lock);
    return allow;
}

static int mip6_destopt_reject(struct xfrm_state *x, struct sk_buff *skb,
                   const struct flowi *fl)
{
    struct net *net = xs_net(x);
    struct inet6_skb_parm *opt = (struct inet6_skb_parm *)skb->cb;
    const struct flowi6 *fl6 = &fl->u.ip6;
    struct ipv6_destopt_hao *hao = NULL;
    struct xfrm_selector sel;
    int offset;
    struct timeval stamp;
    int err = 0;

    if (unlikely(fl6->flowi6_proto == IPPROTO_MH &&
             fl6->fl6_mh_type <= IP6_MH_TYPE_MAX))
        goto out;

    if (likely(opt->dsthao)) {
        offset = ipv6_find_tlv(skb, opt->dsthao, IPV6_TLV_HAO);
        if (likely(offset >= 0))
            hao = (struct ipv6_destopt_hao *)
                    (skb_network_header(skb) + offset);
    }

    skb_get_timestamp(skb, &stamp);

    if (!mip6_report_rl_allow(&stamp, &ipv6_hdr(skb)->daddr,
                  hao ? &hao->addr : &ipv6_hdr(skb)->saddr,
                  opt->iif))
        goto out;

    memset(&sel, 0, sizeof(sel));
    memcpy(&sel.daddr, (xfrm_address_t *)&ipv6_hdr(skb)->daddr,
           sizeof(sel.daddr));
    sel.prefixlen_d = 128;
    memcpy(&sel.saddr, (xfrm_address_t *)&ipv6_hdr(skb)->saddr,
           sizeof(sel.saddr));
    sel.prefixlen_s = 128;
    sel.family = AF_INET6;
    sel.proto = fl6->flowi6_proto;
    sel.dport = xfrm_flowi_dport(fl, &fl6->uli);
    if (sel.dport)
        sel.dport_mask = htons(~0);
    sel.sport = xfrm_flowi_sport(fl, &fl6->uli);
    if (sel.sport)
        sel.sport_mask = htons(~0);
    sel.ifindex = fl6->flowi6_oif;

    err = km_report(net, IPPROTO_DSTOPTS, &sel,
            (hao ? (xfrm_address_t *)&hao->addr : NULL));

 out:
    return err;
}

static int mip6_destopt_offset(struct xfrm_state *x, struct sk_buff *skb,
                   u8 **nexthdr)
{
    u16 offset = sizeof(struct ipv6hdr);
    struct ipv6_opt_hdr *exthdr =
                   (struct ipv6_opt_hdr *)(ipv6_hdr(skb) + 1);
    const unsigned char *nh = skb_network_header(skb);
    unsigned int packet_len = skb->tail - skb->network_header;
    int found_rhdr = 0;

    *nexthdr = &ipv6_hdr(skb)->nexthdr;

    while (offset + 1 <= packet_len) {

        switch (**nexthdr) {
        case NEXTHDR_HOP:
            break;
        case NEXTHDR_ROUTING:
            found_rhdr = 1;
            break;
        case NEXTHDR_DEST:
            /*
             * HAO MUST NOT appear more than once.
             * XXX: It is better to try to find by the end of
             * XXX: packet if HAO exists.
             */
            if (ipv6_find_tlv(skb, offset, IPV6_TLV_HAO) >= 0) {
                LIMIT_NETDEBUG(KERN_WARNING "mip6: hao exists already, override\n");
                return offset;
            }

            if (found_rhdr)
                return offset;

            break;
        default:
            return offset;
        }

        offset += ipv6_optlen(exthdr);
        *nexthdr = &exthdr->nexthdr;
        exthdr = (struct ipv6_opt_hdr *)(nh + offset);
    }

    return offset;
}

static int mip6_destopt_init_state(struct xfrm_state *x)
{
    if (x->id.spi) {
        pr_info("%s: spi is not 0: %u\n", __func__, x->id.spi);
        return -EINVAL;
    }
    if (x->props.mode != XFRM_MODE_ROUTEOPTIMIZATION) {
        pr_info("%s: state's mode is not %u: %u\n",
            __func__, XFRM_MODE_ROUTEOPTIMIZATION, x->props.mode);
        return -EINVAL;
    }

    x->props.header_len = sizeof(struct ipv6_destopt_hdr) +
        calc_padlen(sizeof(struct ipv6_destopt_hdr), 6) +
        sizeof(struct ipv6_destopt_hao);
    WARN_ON(x->props.header_len != 24);

    return 0;
}

/*
 * Do nothing about destroying since it has no specific operation for
 * destination options header unlike IPsec protocols.
 */
static void mip6_destopt_destroy(struct xfrm_state *x)
{
}

static const struct xfrm_type mip6_destopt_type =
{
    .description    = "MIP6DESTOPT",
    .owner      = THIS_MODULE,
    .proto          = IPPROTO_DSTOPTS,
    .flags      = XFRM_TYPE_NON_FRAGMENT | XFRM_TYPE_LOCAL_COADDR,
    .init_state = mip6_destopt_init_state,
    .destructor = mip6_destopt_destroy,
    .input      = mip6_destopt_input,
    .output     = mip6_destopt_output,
    .reject     = mip6_destopt_reject,
    .hdr_offset = mip6_destopt_offset,
};

static int mip6_rthdr_input(struct xfrm_state *x, struct sk_buff *skb)
{
    const struct ipv6hdr *iph = ipv6_hdr(skb);
    struct rt2_hdr *rt2 = (struct rt2_hdr *)skb->data;
    int err = rt2->rt_hdr.nexthdr;

    spin_lock(&x->lock);
    if (!ipv6_addr_equal(&iph->daddr, (struct in6_addr *)x->coaddr) &&
        !ipv6_addr_any((struct in6_addr *)x->coaddr))
        err = -ENOENT;
    spin_unlock(&x->lock);

    return err;
}

/* Routing Header type 2 is inserted.
 * IP Header's dst address is replaced with Routing Header's Home Address.
 */
static int mip6_rthdr_output(struct xfrm_state *x, struct sk_buff *skb)
{
    struct ipv6hdr *iph;
    struct rt2_hdr *rt2;
    u8 nexthdr;

    skb_push(skb, -skb_network_offset(skb));
    iph = ipv6_hdr(skb);

    nexthdr = *skb_mac_header(skb);
    *skb_mac_header(skb) = IPPROTO_ROUTING;

    rt2 = (struct rt2_hdr *)skb_transport_header(skb);
    rt2->rt_hdr.nexthdr = nexthdr;
    rt2->rt_hdr.hdrlen = (x->props.header_len >> 3) - 1;
    rt2->rt_hdr.type = IPV6_SRCRT_TYPE_2;
    rt2->rt_hdr.segments_left = 1;
    memset(&rt2->reserved, 0, sizeof(rt2->reserved));

    WARN_ON(rt2->rt_hdr.hdrlen != 2);

    memcpy(&rt2->addr, &iph->daddr, sizeof(rt2->addr));
    spin_lock_bh(&x->lock);
    memcpy(&iph->daddr, x->coaddr, sizeof(iph->daddr));
    spin_unlock_bh(&x->lock);

    return 0;
}

static int mip6_rthdr_offset(struct xfrm_state *x, struct sk_buff *skb,
                 u8 **nexthdr)
{
    u16 offset = sizeof(struct ipv6hdr);
    struct ipv6_opt_hdr *exthdr =
                   (struct ipv6_opt_hdr *)(ipv6_hdr(skb) + 1);
    const unsigned char *nh = skb_network_header(skb);
    unsigned int packet_len = skb->tail - skb->network_header;
    int found_rhdr = 0;

    *nexthdr = &ipv6_hdr(skb)->nexthdr;

    while (offset + 1 <= packet_len) {

        switch (**nexthdr) {
        case NEXTHDR_HOP:
            break;
        case NEXTHDR_ROUTING:
            if (offset + 3 <= packet_len) {
                struct ipv6_rt_hdr *rt;
                rt = (struct ipv6_rt_hdr *)(nh + offset);
                if (rt->type != 0)
                    return offset;
            }
            found_rhdr = 1;
            break;
        case NEXTHDR_DEST:
            if (ipv6_find_tlv(skb, offset, IPV6_TLV_HAO) >= 0)
                return offset;

            if (found_rhdr)
                return offset;

            break;
        default:
            return offset;
        }

        offset += ipv6_optlen(exthdr);
        *nexthdr = &exthdr->nexthdr;
        exthdr = (struct ipv6_opt_hdr *)(nh + offset);
    }

    return offset;
}

static int mip6_rthdr_init_state(struct xfrm_state *x)
{
    if (x->id.spi) {
        pr_info("%s: spi is not 0: %u\n", __func__, x->id.spi);
        return -EINVAL;
    }
    if (x->props.mode != XFRM_MODE_ROUTEOPTIMIZATION) {
        pr_info("%s: state's mode is not %u: %u\n",
            __func__, XFRM_MODE_ROUTEOPTIMIZATION, x->props.mode);
        return -EINVAL;
    }

    x->props.header_len = sizeof(struct rt2_hdr);

    return 0;
}

/*
 * Do nothing about destroying since it has no specific operation for routing
 * header type 2 unlike IPsec protocols.
 */
static void mip6_rthdr_destroy(struct xfrm_state *x)
{
}

static const struct xfrm_type mip6_rthdr_type =
{
    .description    = "MIP6RT",
    .owner      = THIS_MODULE,
    .proto          = IPPROTO_ROUTING,
    .flags      = XFRM_TYPE_NON_FRAGMENT | XFRM_TYPE_REMOTE_COADDR,
    .init_state = mip6_rthdr_init_state,
    .destructor = mip6_rthdr_destroy,
    .input      = mip6_rthdr_input,
    .output     = mip6_rthdr_output,
    .hdr_offset = mip6_rthdr_offset,
};

static int __init mip6_init(void)
{
    pr_info("Mobile IPv6\n");

    if (xfrm_register_type(&mip6_destopt_type, AF_INET6) < 0) {
        pr_info("%s: can't add xfrm type(destopt)\n", __func__);
        goto mip6_destopt_xfrm_fail;
    }
    if (xfrm_register_type(&mip6_rthdr_type, AF_INET6) < 0) {
        pr_info("%s: can't add xfrm type(rthdr)\n", __func__);
        goto mip6_rthdr_xfrm_fail;
    }
    if (rawv6_mh_filter_register(mip6_mh_filter) < 0) {
        pr_info("%s: can't add rawv6 mh filter\n", __func__);
        goto mip6_rawv6_mh_fail;
    }


    return 0;

 mip6_rawv6_mh_fail:
    xfrm_unregister_type(&mip6_rthdr_type, AF_INET6);
 mip6_rthdr_xfrm_fail:
    xfrm_unregister_type(&mip6_destopt_type, AF_INET6);
 mip6_destopt_xfrm_fail:
    return -EAGAIN;
}

static void __exit mip6_fini(void)
{
    if (rawv6_mh_filter_unregister(mip6_mh_filter) < 0)
        pr_info("%s: can't remove rawv6 mh filter\n", __func__);
    if (xfrm_unregister_type(&mip6_rthdr_type, AF_INET6) < 0)
        pr_info("%s: can't remove xfrm type(rthdr)\n", __func__);
    if (xfrm_unregister_type(&mip6_destopt_type, AF_INET6) < 0)
        pr_info("%s: can't remove xfrm type(destopt)\n", __func__);
}

module_init(mip6_init);
module_exit(mip6_fini);

MODULE_LICENSE("GPL");
MODULE_ALIAS_XFRM_TYPE(AF_INET6, XFRM_PROTO_DSTOPTS);
MODULE_ALIAS_XFRM_TYPE(AF_INET6, XFRM_PROTO_ROUTING);