nf_nat_core.c

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/*
 * (C) 1999-2001 Paul `Rusty' Russell
 * (C) 2002-2006 Netfilter Core Team <[email protected]>
 * (C) 2011 Patrick McHardy <[email protected]>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 */

#include <linux/module.h>
#include <linux/types.h>
#include <linux/timer.h>
#include <linux/skbuff.h>
#include <linux/gfp.h>
#include <net/xfrm.h>
#include <linux/jhash.h>
#include <linux/rtnetlink.h>

#include <net/netfilter/nf_conntrack.h>
#include <net/netfilter/nf_conntrack_core.h>
#include <net/netfilter/nf_nat.h>
#include <net/netfilter/nf_nat_l3proto.h>
#include <net/netfilter/nf_nat_l4proto.h>
#include <net/netfilter/nf_nat_core.h>
#include <net/netfilter/nf_nat_helper.h>
#include <net/netfilter/nf_conntrack_helper.h>
#include <net/netfilter/nf_conntrack_l3proto.h>
#include <net/netfilter/nf_conntrack_zones.h>
#include <linux/netfilter/nf_nat.h>

static DEFINE_SPINLOCK(nf_nat_lock);

static DEFINE_MUTEX(nf_nat_proto_mutex);
static const struct nf_nat_l3proto __rcu *nf_nat_l3protos[NFPROTO_NUMPROTO]
                        __read_mostly;
static const struct nf_nat_l4proto __rcu **nf_nat_l4protos[NFPROTO_NUMPROTO]
                        __read_mostly;


inline const struct nf_nat_l3proto *
__nf_nat_l3proto_find(u8 family)
{
    return rcu_dereference(nf_nat_l3protos[family]);
}

inline const struct nf_nat_l4proto *
__nf_nat_l4proto_find(u8 family, u8 protonum)
{
    return rcu_dereference(nf_nat_l4protos[family][protonum]);
}
EXPORT_SYMBOL_GPL(__nf_nat_l4proto_find);

#ifdef CONFIG_XFRM
static void __nf_nat_decode_session(struct sk_buff *skb, struct flowi *fl)
{
    const struct nf_nat_l3proto *l3proto;
    const struct nf_conn *ct;
    enum ip_conntrack_info ctinfo;
    enum ip_conntrack_dir dir;
    unsigned  long statusbit;
    u8 family;

    ct = nf_ct_get(skb, &ctinfo);
    if (ct == NULL)
        return;

    family = ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.l3num;
    rcu_read_lock();
    l3proto = __nf_nat_l3proto_find(family);
    if (l3proto == NULL)
        goto out;

    dir = CTINFO2DIR(ctinfo);
    if (dir == IP_CT_DIR_ORIGINAL)
        statusbit = IPS_DST_NAT;
    else
        statusbit = IPS_SRC_NAT;

    l3proto->decode_session(skb, ct, dir, statusbit, fl);
out:
    rcu_read_unlock();
}

int nf_xfrm_me_harder(struct sk_buff *skb, unsigned int family)
{
    struct flowi fl;
    unsigned int hh_len;
    struct dst_entry *dst;

    if (xfrm_decode_session(skb, &fl, family) < 0)
        return -1;

    dst = skb_dst(skb);
    if (dst->xfrm)
        dst = ((struct xfrm_dst *)dst)->route;
    dst_hold(dst);

    dst = xfrm_lookup(dev_net(dst->dev), dst, &fl, skb->sk, 0);
    if (IS_ERR(dst))
        return -1;

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

    /* Change in oif may mean change in hh_len. */
    hh_len = skb_dst(skb)->dev->hard_header_len;
    if (skb_headroom(skb) < hh_len &&
        pskb_expand_head(skb, hh_len - skb_headroom(skb), 0, GFP_ATOMIC))
        return -1;
    return 0;
}
EXPORT_SYMBOL(nf_xfrm_me_harder);
#endif /* CONFIG_XFRM */

/* We keep an extra hash for each conntrack, for fast searching. */
static inline unsigned int
hash_by_src(const struct net *net, u16 zone,
        const struct nf_conntrack_tuple *tuple)
{
    unsigned int hash;

    /* Original src, to ensure we map it consistently if poss. */
    hash = jhash2((u32 *)&tuple->src, sizeof(tuple->src) / sizeof(u32),
              tuple->dst.protonum ^ zone ^ nf_conntrack_hash_rnd);
    return ((u64)hash * net->ct.nat_htable_size) >> 32;
}

/* Is this tuple already taken? (not by us) */
int
nf_nat_used_tuple(const struct nf_conntrack_tuple *tuple,
          const struct nf_conn *ignored_conntrack)
{
    /* Conntrack tracking doesn't keep track of outgoing tuples; only
     * incoming ones.  NAT means they don't have a fixed mapping,
     * so we invert the tuple and look for the incoming reply.
     *
     * We could keep a separate hash if this proves too slow.
     */
    struct nf_conntrack_tuple reply;

    nf_ct_invert_tuplepr(&reply, tuple);
    return nf_conntrack_tuple_taken(&reply, ignored_conntrack);
}
EXPORT_SYMBOL(nf_nat_used_tuple);

/* If we source map this tuple so reply looks like reply_tuple, will
 * that meet the constraints of range.
 */
static int in_range(const struct nf_nat_l3proto *l3proto,
            const struct nf_nat_l4proto *l4proto,
            const struct nf_conntrack_tuple *tuple,
            const struct nf_nat_range *range)
{
    /* If we are supposed to map IPs, then we must be in the
     * range specified, otherwise let this drag us onto a new src IP.
     */
    if (range->flags & NF_NAT_RANGE_MAP_IPS &&
        !l3proto->in_range(tuple, range))
        return 0;

    if (!(range->flags & NF_NAT_RANGE_PROTO_SPECIFIED) ||
        l4proto->in_range(tuple, NF_NAT_MANIP_SRC,
                  &range->min_proto, &range->max_proto))
        return 1;

    return 0;
}

static inline int
same_src(const struct nf_conn *ct,
     const struct nf_conntrack_tuple *tuple)
{
    const struct nf_conntrack_tuple *t;

    t = &ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple;
    return (t->dst.protonum == tuple->dst.protonum &&
        nf_inet_addr_cmp(&t->src.u3, &tuple->src.u3) &&
        t->src.u.all == tuple->src.u.all);
}

/* Only called for SRC manip */
static int
find_appropriate_src(struct net *net, u16 zone,
             const struct nf_nat_l3proto *l3proto,
             const struct nf_nat_l4proto *l4proto,
             const struct nf_conntrack_tuple *tuple,
             struct nf_conntrack_tuple *result,
             const struct nf_nat_range *range)
{
    unsigned int h = hash_by_src(net, zone, tuple);
    const struct nf_conn_nat *nat;
    const struct nf_conn *ct;
    const struct hlist_node *n;

    hlist_for_each_entry_rcu(nat, n, &net->ct.nat_bysource[h], bysource) {
        ct = nat->ct;
        if (same_src(ct, tuple) && nf_ct_zone(ct) == zone) {
            /* Copy source part from reply tuple. */
            nf_ct_invert_tuplepr(result,
                       &ct->tuplehash[IP_CT_DIR_REPLY].tuple);
            result->dst = tuple->dst;

            if (in_range(l3proto, l4proto, result, range))
                return 1;
        }
    }
    return 0;
}

/* For [FUTURE] fragmentation handling, we want the least-used
 * src-ip/dst-ip/proto triple.  Fairness doesn't come into it.  Thus
 * if the range specifies 1.2.3.4 ports 10000-10005 and 1.2.3.5 ports
 * 1-65535, we don't do pro-rata allocation based on ports; we choose
 * the ip with the lowest src-ip/dst-ip/proto usage.
 */
static void
find_best_ips_proto(u16 zone, struct nf_conntrack_tuple *tuple,
            const struct nf_nat_range *range,
            const struct nf_conn *ct,
            enum nf_nat_manip_type maniptype)
{
    union nf_inet_addr *var_ipp;
    unsigned int i, max;
    /* Host order */
    u32 minip, maxip, j, dist;
    bool full_range;

    /* No IP mapping?  Do nothing. */
    if (!(range->flags & NF_NAT_RANGE_MAP_IPS))
        return;

    if (maniptype == NF_NAT_MANIP_SRC)
        var_ipp = &tuple->src.u3;
    else
        var_ipp = &tuple->dst.u3;

    /* Fast path: only one choice. */
    if (nf_inet_addr_cmp(&range->min_addr, &range->max_addr)) {
        *var_ipp = range->min_addr;
        return;
    }

    if (nf_ct_l3num(ct) == NFPROTO_IPV4)
        max = sizeof(var_ipp->ip) / sizeof(u32) - 1;
    else
        max = sizeof(var_ipp->ip6) / sizeof(u32) - 1;

    /* Hashing source and destination IPs gives a fairly even
     * spread in practice (if there are a small number of IPs
     * involved, there usually aren't that many connections
     * anyway).  The consistency means that servers see the same
     * client coming from the same IP (some Internet Banking sites
     * like this), even across reboots.
     */
    j = jhash2((u32 *)&tuple->src.u3, sizeof(tuple->src.u3) / sizeof(u32),
           range->flags & NF_NAT_RANGE_PERSISTENT ?
            0 : (__force u32)tuple->dst.u3.all[max] ^ zone);

    full_range = false;
    for (i = 0; i <= max; i++) {
        /* If first bytes of the address are at the maximum, use the
         * distance. Otherwise use the full range.
         */
        if (!full_range) {
            minip = ntohl((__force __be32)range->min_addr.all[i]);
            maxip = ntohl((__force __be32)range->max_addr.all[i]);
            dist  = maxip - minip + 1;
        } else {
            minip = 0;
            dist  = ~0;
        }

        var_ipp->all[i] = (__force __u32)
            htonl(minip + (((u64)j * dist) >> 32));
        if (var_ipp->all[i] != range->max_addr.all[i])
            full_range = true;

        if (!(range->flags & NF_NAT_RANGE_PERSISTENT))
            j ^= (__force u32)tuple->dst.u3.all[i];
    }
}

/* Manipulate the tuple into the range given. For NF_INET_POST_ROUTING,
 * we change the source to map into the range. For NF_INET_PRE_ROUTING
 * and NF_INET_LOCAL_OUT, we change the destination to map into the
 * range. It might not be possible to get a unique tuple, but we try.
 * At worst (or if we race), we will end up with a final duplicate in
 * __ip_conntrack_confirm and drop the packet. */
static void
get_unique_tuple(struct nf_conntrack_tuple *tuple,
         const struct nf_conntrack_tuple *orig_tuple,
         const struct nf_nat_range *range,
         struct nf_conn *ct,
         enum nf_nat_manip_type maniptype)
{
    const struct nf_nat_l3proto *l3proto;
    const struct nf_nat_l4proto *l4proto;
    struct net *net = nf_ct_net(ct);
    u16 zone = nf_ct_zone(ct);

    rcu_read_lock();
    l3proto = __nf_nat_l3proto_find(orig_tuple->src.l3num);
    l4proto = __nf_nat_l4proto_find(orig_tuple->src.l3num,
                    orig_tuple->dst.protonum);

    /* 1) If this srcip/proto/src-proto-part is currently mapped,
     * and that same mapping gives a unique tuple within the given
     * range, use that.
     *
     * This is only required for source (ie. NAT/masq) mappings.
     * So far, we don't do local source mappings, so multiple
     * manips not an issue.
     */
    if (maniptype == NF_NAT_MANIP_SRC &&
        !(range->flags & NF_NAT_RANGE_PROTO_RANDOM)) {
        /* try the original tuple first */
        if (in_range(l3proto, l4proto, orig_tuple, range)) {
            if (!nf_nat_used_tuple(orig_tuple, ct)) {
                *tuple = *orig_tuple;
                goto out;
            }
        } else if (find_appropriate_src(net, zone, l3proto, l4proto,
                        orig_tuple, tuple, range)) {
            pr_debug("get_unique_tuple: Found current src map\n");
            if (!nf_nat_used_tuple(tuple, ct))
                goto out;
        }
    }

    /* 2) Select the least-used IP/proto combination in the given range */
    *tuple = *orig_tuple;
    find_best_ips_proto(zone, tuple, range, ct, maniptype);

    /* 3) The per-protocol part of the manip is made to map into
     * the range to make a unique tuple.
     */

    /* Only bother mapping if it's not already in range and unique */
    if (!(range->flags & NF_NAT_RANGE_PROTO_RANDOM)) {
        if (range->flags & NF_NAT_RANGE_PROTO_SPECIFIED) {
            if (l4proto->in_range(tuple, maniptype,
                          &range->min_proto,
                          &range->max_proto) &&
                (range->min_proto.all == range->max_proto.all ||
                 !nf_nat_used_tuple(tuple, ct)))
                goto out;
        } else if (!nf_nat_used_tuple(tuple, ct)) {
            goto out;
        }
    }

    /* Last change: get protocol to try to obtain unique tuple. */
    l4proto->unique_tuple(l3proto, tuple, range, maniptype, ct);
out:
    rcu_read_unlock();
}

unsigned int
nf_nat_setup_info(struct nf_conn *ct,
          const struct nf_nat_range *range,
          enum nf_nat_manip_type maniptype)
{
    struct net *net = nf_ct_net(ct);
    struct nf_conntrack_tuple curr_tuple, new_tuple;
    struct nf_conn_nat *nat;

    /* nat helper or nfctnetlink also setup binding */
    nat = nfct_nat(ct);
    if (!nat) {
        nat = nf_ct_ext_add(ct, NF_CT_EXT_NAT, GFP_ATOMIC);
        if (nat == NULL) {
            pr_debug("failed to add NAT extension\n");
            return NF_ACCEPT;
        }
    }

    NF_CT_ASSERT(maniptype == NF_NAT_MANIP_SRC ||
             maniptype == NF_NAT_MANIP_DST);
    BUG_ON(nf_nat_initialized(ct, maniptype));

    /* What we've got will look like inverse of reply. Normally
     * this is what is in the conntrack, except for prior
     * manipulations (future optimization: if num_manips == 0,
     * orig_tp = ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple)
     */
    nf_ct_invert_tuplepr(&curr_tuple,
                 &ct->tuplehash[IP_CT_DIR_REPLY].tuple);

    get_unique_tuple(&new_tuple, &curr_tuple, range, ct, maniptype);

    if (!nf_ct_tuple_equal(&new_tuple, &curr_tuple)) {
        struct nf_conntrack_tuple reply;

        /* Alter conntrack table so will recognize replies. */
        nf_ct_invert_tuplepr(&reply, &new_tuple);
        nf_conntrack_alter_reply(ct, &reply);

        /* Non-atomic: we own this at the moment. */
        if (maniptype == NF_NAT_MANIP_SRC)
            ct->status |= IPS_SRC_NAT;
        else
            ct->status |= IPS_DST_NAT;
    }

    if (maniptype == NF_NAT_MANIP_SRC) {
        unsigned int srchash;

        srchash = hash_by_src(net, nf_ct_zone(ct),
                      &ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple);
        spin_lock_bh(&nf_nat_lock);
        /* nf_conntrack_alter_reply might re-allocate extension aera */
        nat = nfct_nat(ct);
        nat->ct = ct;
        hlist_add_head_rcu(&nat->bysource,
                   &net->ct.nat_bysource[srchash]);
        spin_unlock_bh(&nf_nat_lock);
    }

    /* It's done. */
    if (maniptype == NF_NAT_MANIP_DST)
        ct->status |= IPS_DST_NAT_DONE;
    else
        ct->status |= IPS_SRC_NAT_DONE;

    return NF_ACCEPT;
}
EXPORT_SYMBOL(nf_nat_setup_info);

/* Do packet manipulations according to nf_nat_setup_info. */
unsigned int nf_nat_packet(struct nf_conn *ct,
               enum ip_conntrack_info ctinfo,
               unsigned int hooknum,
               struct sk_buff *skb)
{
    const struct nf_nat_l3proto *l3proto;
    const struct nf_nat_l4proto *l4proto;
    enum ip_conntrack_dir dir = CTINFO2DIR(ctinfo);
    unsigned long statusbit;
    enum nf_nat_manip_type mtype = HOOK2MANIP(hooknum);

    if (mtype == NF_NAT_MANIP_SRC)
        statusbit = IPS_SRC_NAT;
    else
        statusbit = IPS_DST_NAT;

    /* Invert if this is reply dir. */
    if (dir == IP_CT_DIR_REPLY)
        statusbit ^= IPS_NAT_MASK;

    /* Non-atomic: these bits don't change. */
    if (ct->status & statusbit) {
        struct nf_conntrack_tuple target;

        /* We are aiming to look like inverse of other direction. */
        nf_ct_invert_tuplepr(&target, &ct->tuplehash[!dir].tuple);

        l3proto = __nf_nat_l3proto_find(target.src.l3num);
        l4proto = __nf_nat_l4proto_find(target.src.l3num,
                        target.dst.protonum);
        if (!l3proto->manip_pkt(skb, 0, l4proto, &target, mtype))
            return NF_DROP;
    }
    return NF_ACCEPT;
}
EXPORT_SYMBOL_GPL(nf_nat_packet);

struct nf_nat_proto_clean {
    u8  l3proto;
    u8  l4proto;
    bool    hash;
};

/* Clear NAT section of all conntracks, in case we're loaded again. */
static int nf_nat_proto_clean(struct nf_conn *i, void *data)
{
    const struct nf_nat_proto_clean *clean = data;
    struct nf_conn_nat *nat = nfct_nat(i);

    if (!nat)
        return 0;
    if (!(i->status & IPS_SRC_NAT_DONE))
        return 0;
    if ((clean->l3proto && nf_ct_l3num(i) != clean->l3proto) ||
        (clean->l4proto && nf_ct_protonum(i) != clean->l4proto))
        return 0;

    if (clean->hash) {
        spin_lock_bh(&nf_nat_lock);
        hlist_del_rcu(&nat->bysource);
        spin_unlock_bh(&nf_nat_lock);
    } else {
        memset(nat, 0, sizeof(*nat));
        i->status &= ~(IPS_NAT_MASK | IPS_NAT_DONE_MASK |
                   IPS_SEQ_ADJUST);
    }
    return 0;
}

static void nf_nat_l4proto_clean(u8 l3proto, u8 l4proto)
{
    struct nf_nat_proto_clean clean = {
        .l3proto = l3proto,
        .l4proto = l4proto,
    };
    struct net *net;

    rtnl_lock();
    /* Step 1 - remove from bysource hash */
    clean.hash = true;
    for_each_net(net)
        nf_ct_iterate_cleanup(net, nf_nat_proto_clean, &clean);
    synchronize_rcu();

    /* Step 2 - clean NAT section */
    clean.hash = false;
    for_each_net(net)
        nf_ct_iterate_cleanup(net, nf_nat_proto_clean, &clean);
    rtnl_unlock();
}

static void nf_nat_l3proto_clean(u8 l3proto)
{
    struct nf_nat_proto_clean clean = {
        .l3proto = l3proto,
    };
    struct net *net;

    rtnl_lock();
    /* Step 1 - remove from bysource hash */
    clean.hash = true;
    for_each_net(net)
        nf_ct_iterate_cleanup(net, nf_nat_proto_clean, &clean);
    synchronize_rcu();

    /* Step 2 - clean NAT section */
    clean.hash = false;
    for_each_net(net)
        nf_ct_iterate_cleanup(net, nf_nat_proto_clean, &clean);
    rtnl_unlock();
}

/* Protocol registration. */
int nf_nat_l4proto_register(u8 l3proto, const struct nf_nat_l4proto *l4proto)
{
    const struct nf_nat_l4proto **l4protos;
    unsigned int i;
    int ret = 0;

    mutex_lock(&nf_nat_proto_mutex);
    if (nf_nat_l4protos[l3proto] == NULL) {
        l4protos = kmalloc(IPPROTO_MAX * sizeof(struct nf_nat_l4proto *),
                   GFP_KERNEL);
        if (l4protos == NULL) {
            ret = -ENOMEM;
            goto out;
        }

        for (i = 0; i < IPPROTO_MAX; i++)
            RCU_INIT_POINTER(l4protos[i], &nf_nat_l4proto_unknown);

        /* Before making proto_array visible to lockless readers,
         * we must make sure its content is committed to memory.
         */
        smp_wmb();

        nf_nat_l4protos[l3proto] = l4protos;
    }

    if (rcu_dereference_protected(
            nf_nat_l4protos[l3proto][l4proto->l4proto],
            lockdep_is_held(&nf_nat_proto_mutex)
            ) != &nf_nat_l4proto_unknown) {
        ret = -EBUSY;
        goto out;
    }
    RCU_INIT_POINTER(nf_nat_l4protos[l3proto][l4proto->l4proto], l4proto);
 out:
    mutex_unlock(&nf_nat_proto_mutex);
    return ret;
}
EXPORT_SYMBOL_GPL(nf_nat_l4proto_register);

/* No one stores the protocol anywhere; simply delete it. */
void nf_nat_l4proto_unregister(u8 l3proto, const struct nf_nat_l4proto *l4proto)
{
    mutex_lock(&nf_nat_proto_mutex);
    RCU_INIT_POINTER(nf_nat_l4protos[l3proto][l4proto->l4proto],
             &nf_nat_l4proto_unknown);
    mutex_unlock(&nf_nat_proto_mutex);
    synchronize_rcu();

    nf_nat_l4proto_clean(l3proto, l4proto->l4proto);
}
EXPORT_SYMBOL_GPL(nf_nat_l4proto_unregister);

int nf_nat_l3proto_register(const struct nf_nat_l3proto *l3proto)
{
    int err;

    err = nf_ct_l3proto_try_module_get(l3proto->l3proto);
    if (err < 0)
        return err;

    mutex_lock(&nf_nat_proto_mutex);
    RCU_INIT_POINTER(nf_nat_l4protos[l3proto->l3proto][IPPROTO_TCP],
             &nf_nat_l4proto_tcp);
    RCU_INIT_POINTER(nf_nat_l4protos[l3proto->l3proto][IPPROTO_UDP],
             &nf_nat_l4proto_udp);
    mutex_unlock(&nf_nat_proto_mutex);

    RCU_INIT_POINTER(nf_nat_l3protos[l3proto->l3proto], l3proto);
    return 0;
}
EXPORT_SYMBOL_GPL(nf_nat_l3proto_register);

void nf_nat_l3proto_unregister(const struct nf_nat_l3proto *l3proto)
{
    mutex_lock(&nf_nat_proto_mutex);
    RCU_INIT_POINTER(nf_nat_l3protos[l3proto->l3proto], NULL);
    mutex_unlock(&nf_nat_proto_mutex);
    synchronize_rcu();

    nf_nat_l3proto_clean(l3proto->l3proto);
    nf_ct_l3proto_module_put(l3proto->l3proto);
}
EXPORT_SYMBOL_GPL(nf_nat_l3proto_unregister);

/* No one using conntrack by the time this called. */
static void nf_nat_cleanup_conntrack(struct nf_conn *ct)
{
    struct nf_conn_nat *nat = nf_ct_ext_find(ct, NF_CT_EXT_NAT);

    if (nat == NULL || nat->ct == NULL)
        return;

    NF_CT_ASSERT(nat->ct->status & IPS_SRC_NAT_DONE);

    spin_lock_bh(&nf_nat_lock);
    hlist_del_rcu(&nat->bysource);
    spin_unlock_bh(&nf_nat_lock);
}

static void nf_nat_move_storage(void *new, void *old)
{
    struct nf_conn_nat *new_nat = new;
    struct nf_conn_nat *old_nat = old;
    struct nf_conn *ct = old_nat->ct;

    if (!ct || !(ct->status & IPS_SRC_NAT_DONE))
        return;

    spin_lock_bh(&nf_nat_lock);
    hlist_replace_rcu(&old_nat->bysource, &new_nat->bysource);
    spin_unlock_bh(&nf_nat_lock);
}

static struct nf_ct_ext_type nat_extend __read_mostly = {
    .len        = sizeof(struct nf_conn_nat),
    .align      = __alignof__(struct nf_conn_nat),
    .destroy    = nf_nat_cleanup_conntrack,
    .move       = nf_nat_move_storage,
    .id     = NF_CT_EXT_NAT,
    .flags      = NF_CT_EXT_F_PREALLOC,
};

#if defined(CONFIG_NF_CT_NETLINK) || defined(CONFIG_NF_CT_NETLINK_MODULE)

#include <linux/netfilter/nfnetlink.h>
#include <linux/netfilter/nfnetlink_conntrack.h>

static const struct nla_policy protonat_nla_policy[CTA_PROTONAT_MAX+1] = {
    [CTA_PROTONAT_PORT_MIN] = { .type = NLA_U16 },
    [CTA_PROTONAT_PORT_MAX] = { .type = NLA_U16 },
};

static int nfnetlink_parse_nat_proto(struct nlattr *attr,
                     const struct nf_conn *ct,
                     struct nf_nat_range *range)
{
    struct nlattr *tb[CTA_PROTONAT_MAX+1];
    const struct nf_nat_l4proto *l4proto;
    int err;

    err = nla_parse_nested(tb, CTA_PROTONAT_MAX, attr, protonat_nla_policy);
    if (err < 0)
        return err;

    l4proto = __nf_nat_l4proto_find(nf_ct_l3num(ct), nf_ct_protonum(ct));
    if (l4proto->nlattr_to_range)
        err = l4proto->nlattr_to_range(tb, range);

    return err;
}

static const struct nla_policy nat_nla_policy[CTA_NAT_MAX+1] = {
    [CTA_NAT_V4_MINIP]  = { .type = NLA_U32 },
    [CTA_NAT_V4_MAXIP]  = { .type = NLA_U32 },
    [CTA_NAT_V6_MINIP]  = { .len = sizeof(struct in6_addr) },
    [CTA_NAT_V6_MAXIP]  = { .len = sizeof(struct in6_addr) },
    [CTA_NAT_PROTO]     = { .type = NLA_NESTED },
};

static int
nfnetlink_parse_nat(const struct nlattr *nat,
            const struct nf_conn *ct, struct nf_nat_range *range)
{
    const struct nf_nat_l3proto *l3proto;
    struct nlattr *tb[CTA_NAT_MAX+1];
    int err;

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

    err = nla_parse_nested(tb, CTA_NAT_MAX, nat, nat_nla_policy);
    if (err < 0)
        return err;

    rcu_read_lock();
    l3proto = __nf_nat_l3proto_find(nf_ct_l3num(ct));
    if (l3proto == NULL) {
        err = -EAGAIN;
        goto out;
    }
    err = l3proto->nlattr_to_range(tb, range);
    if (err < 0)
        goto out;

    if (!tb[CTA_NAT_PROTO])
        goto out;

    err = nfnetlink_parse_nat_proto(tb[CTA_NAT_PROTO], ct, range);
out:
    rcu_read_unlock();
    return err;
}

static int
nfnetlink_parse_nat_setup(struct nf_conn *ct,
              enum nf_nat_manip_type manip,
              const struct nlattr *attr)
{
    struct nf_nat_range range;
    int err;

    err = nfnetlink_parse_nat(attr, ct, &range);
    if (err < 0)
        return err;
    if (nf_nat_initialized(ct, manip))
        return -EEXIST;

    return nf_nat_setup_info(ct, &range, manip);
}
#else
static int
nfnetlink_parse_nat_setup(struct nf_conn *ct,
              enum nf_nat_manip_type manip,
              const struct nlattr *attr)
{
    return -EOPNOTSUPP;
}
#endif

static int __net_init nf_nat_net_init(struct net *net)
{
    /* Leave them the same for the moment. */
    net->ct.nat_htable_size = net->ct.htable_size;
    net->ct.nat_bysource = nf_ct_alloc_hashtable(&net->ct.nat_htable_size, 0);
    if (!net->ct.nat_bysource)
        return -ENOMEM;
    return 0;
}

static void __net_exit nf_nat_net_exit(struct net *net)
{
    struct nf_nat_proto_clean clean = {};

    nf_ct_iterate_cleanup(net, &nf_nat_proto_clean, &clean);
    synchronize_rcu();
    nf_ct_free_hashtable(net->ct.nat_bysource, net->ct.nat_htable_size);
}

static struct pernet_operations nf_nat_net_ops = {
    .init = nf_nat_net_init,
    .exit = nf_nat_net_exit,
};

static struct nf_ct_helper_expectfn follow_master_nat = {
    .name       = "nat-follow-master",
    .expectfn   = nf_nat_follow_master,
};

static struct nfq_ct_nat_hook nfq_ct_nat = {
    .seq_adjust = nf_nat_tcp_seq_adjust,
};

static int __init nf_nat_init(void)
{
    int ret;

    ret = nf_ct_extend_register(&nat_extend);
    if (ret < 0) {
        printk(KERN_ERR "nf_nat_core: Unable to register extension\n");
        return ret;
    }

    ret = register_pernet_subsys(&nf_nat_net_ops);
    if (ret < 0)
        goto cleanup_extend;

    nf_ct_helper_expectfn_register(&follow_master_nat);

    /* Initialize fake conntrack so that NAT will skip it */
    nf_ct_untracked_status_or(IPS_NAT_DONE_MASK);

    BUG_ON(nf_nat_seq_adjust_hook != NULL);
    RCU_INIT_POINTER(nf_nat_seq_adjust_hook, nf_nat_seq_adjust);
    BUG_ON(nfnetlink_parse_nat_setup_hook != NULL);
    RCU_INIT_POINTER(nfnetlink_parse_nat_setup_hook,
               nfnetlink_parse_nat_setup);
    BUG_ON(nf_ct_nat_offset != NULL);
    RCU_INIT_POINTER(nf_ct_nat_offset, nf_nat_get_offset);
    RCU_INIT_POINTER(nfq_ct_nat_hook, &nfq_ct_nat);
#ifdef CONFIG_XFRM
    BUG_ON(nf_nat_decode_session_hook != NULL);
    RCU_INIT_POINTER(nf_nat_decode_session_hook, __nf_nat_decode_session);
#endif
    return 0;

 cleanup_extend:
    nf_ct_extend_unregister(&nat_extend);
    return ret;
}

static void __exit nf_nat_cleanup(void)
{
    unsigned int i;

    unregister_pernet_subsys(&nf_nat_net_ops);
    nf_ct_extend_unregister(&nat_extend);
    nf_ct_helper_expectfn_unregister(&follow_master_nat);
    RCU_INIT_POINTER(nf_nat_seq_adjust_hook, NULL);
    RCU_INIT_POINTER(nfnetlink_parse_nat_setup_hook, NULL);
    RCU_INIT_POINTER(nf_ct_nat_offset, NULL);
    RCU_INIT_POINTER(nfq_ct_nat_hook, NULL);
#ifdef CONFIG_XFRM
    RCU_INIT_POINTER(nf_nat_decode_session_hook, NULL);
#endif
    for (i = 0; i < NFPROTO_NUMPROTO; i++)
        kfree(nf_nat_l4protos[i]);
    synchronize_net();
}

MODULE_LICENSE("GPL");

module_init(nf_nat_init);
module_exit(nf_nat_cleanup);