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/* Everything about the rules for NAT. */

#include <linux/types.h>

#include <linux/ip.h>

#include <linux/netfilter.h>

#include <linux/netfilter_ipv4.h>

#include <linux/module.h>

#include <linux/kmod.h>

#include <linux/skbuff.h>

#include <linux/proc_fs.h>

#include <net/checksum.h>

#include <linux/bitops.h>

#include <linux/version.h>

#define ASSERT_READ_LOCK(x) MUST_BE_READ_LOCKED(&ip_nat_lock)

#define ASSERT_WRITE_LOCK(x) MUST_BE_WRITE_LOCKED(&ip_nat_lock)

#include <linux/netfilter_ipv4/ip_tables.h>

#include <linux/netfilter_ipv4/ip_nat.h>

#include <linux/netfilter_ipv4/ip_nat_core.h>

#include <linux/netfilter_ipv4/ip_nat_rule.h>

#include <linux/netfilter_ipv4/listhelp.h>

#if 0

#define DEBUGP printk

#else

#define DEBUGP(format, args...)

#endif

#define NAT_VALID_HOOKS ((1<<NF_IP_PRE_ROUTING) | (1<<NF_IP_POST_ROUTING) | (1<<NF_IP_LOCAL_OUT))

/* Standard entry. */

struct ipt_standard

{

        struct ipt_entry entry;

        struct ipt_standard_target target;

};

struct ipt_error_target

{

        struct ipt_entry_target target;

        char errorname[IPT_FUNCTION_MAXNAMELEN];

};

struct ipt_error

{

        struct ipt_entry entry;

        struct ipt_error_target target;

};

static struct

{

        struct ipt_replace repl;

        struct ipt_standard entries[3];

        struct ipt_error term;

} nat_initial_table __initdata

= { { "nat", NAT_VALID_HOOKS, 4,

      sizeof(struct ipt_standard) * 3 + sizeof(struct ipt_error),

      { [NF_IP_PRE_ROUTING] 0,

        [NF_IP_POST_ROUTING] sizeof(struct ipt_standard),

        [NF_IP_LOCAL_OUT] sizeof(struct ipt_standard) * 2 },

      { [NF_IP_PRE_ROUTING] 0,

        [NF_IP_POST_ROUTING] sizeof(struct ipt_standard),

        [NF_IP_LOCAL_OUT] sizeof(struct ipt_standard) * 2 },

      0, NULL, { } },

    {

            /* PRE_ROUTING */

            { { { { 0 }, { 0 }, { 0 }, { 0 }, "", "", { 0 }, { 0 }, 0, 0, 0 },

                0,

                sizeof(struct ipt_entry),

                sizeof(struct ipt_standard),

                0, { 0, 0 }, { } },

              { { { { IPT_ALIGN(sizeof(struct ipt_standard_target)), "" } }, { } },

                -NF_ACCEPT - 1 } },

            /* POST_ROUTING */

            { { { { 0 }, { 0 }, { 0 }, { 0 }, "", "", { 0 }, { 0 }, 0, 0, 0 },

                0,

                sizeof(struct ipt_entry),

                sizeof(struct ipt_standard),

                0, { 0, 0 }, { } },

              { { { { IPT_ALIGN(sizeof(struct ipt_standard_target)), "" } }, { } },

                -NF_ACCEPT - 1 } },

            /* LOCAL_OUT */

            { { { { 0 }, { 0 }, { 0 }, { 0 }, "", "", { 0 }, { 0 }, 0, 0, 0 },

                0,

                sizeof(struct ipt_entry),

                sizeof(struct ipt_standard),

                0, { 0, 0 }, { } },

              { { { { IPT_ALIGN(sizeof(struct ipt_standard_target)), "" } }, { } },

                -NF_ACCEPT - 1 } }

    },

    /* ERROR */

    { { { { 0 }, { 0 }, { 0 }, { 0 }, "", "", { 0 }, { 0 }, 0, 0, 0 },

        0,

        sizeof(struct ipt_entry),

        sizeof(struct ipt_error),

        0, { 0, 0 }, { } },

      { { { { IPT_ALIGN(sizeof(struct ipt_error_target)), IPT_ERROR_TARGET } },

          { } },

        "ERROR"

      }

    }

};

static struct ipt_table nat_table

= { { NULL, NULL }, "nat", &nat_initial_table.repl,

    NAT_VALID_HOOKS, RW_LOCK_UNLOCKED, NULL, THIS_MODULE };

/* Source NAT */

static unsigned int ipt_snat_target(struct sk_buff **pskb,

                                    unsigned int hooknum,

                                    const struct net_device *in,

                                    const struct net_device *out,

                                    const void *targinfo,

                                    void *userinfo)

{

        struct ip_conntrack *ct;

        enum ip_conntrack_info ctinfo;

        IP_NF_ASSERT(hooknum == NF_IP_POST_ROUTING);

        ct = ip_conntrack_get(*pskb, &ctinfo);

        /* Connection must be valid and new. */

        IP_NF_ASSERT(ct && (ctinfo == IP_CT_NEW || ctinfo == IP_CT_RELATED));

        IP_NF_ASSERT(out);

        return ip_nat_setup_info(ct, targinfo, hooknum);

}

static unsigned int ipt_dnat_target(struct sk_buff **pskb,

                                    unsigned int hooknum,

                                    const struct net_device *in,

                                    const struct net_device *out,

                                    const void *targinfo,

                                    void *userinfo)

{

        struct ip_conntrack *ct;

        enum ip_conntrack_info ctinfo;

#ifdef CONFIG_IP_NF_NAT_LOCAL

        IP_NF_ASSERT(hooknum == NF_IP_PRE_ROUTING

                     || hooknum == NF_IP_LOCAL_OUT);

#else

        IP_NF_ASSERT(hooknum == NF_IP_PRE_ROUTING);

#endif

        ct = ip_conntrack_get(*pskb, &ctinfo);

        /* Connection must be valid and new. */

        IP_NF_ASSERT(ct && (ctinfo == IP_CT_NEW || ctinfo == IP_CT_RELATED));

        return ip_nat_setup_info(ct, targinfo, hooknum);

}

static int ipt_snat_checkentry(const char *tablename,

                               const struct ipt_entry *e,

                               void *targinfo,

                               unsigned int targinfosize,

                               unsigned int hook_mask)

{

        struct ip_nat_multi_range *mr = targinfo;

        /* Must be a valid range */

        if (targinfosize < sizeof(struct ip_nat_multi_range)) {

                DEBUGP("SNAT: Target size %u too small\n", targinfosize);

                return 0;

        }

        if (targinfosize != IPT_ALIGN((sizeof(struct ip_nat_multi_range)

                                       + (sizeof(struct ip_nat_range)

                                          * (mr->rangesize - 1))))) {

                DEBUGP("SNAT: Target size %u wrong for %u ranges\n",

                       targinfosize, mr->rangesize);

                return 0;

        }

        /* Only allow these for NAT. */

        if (strcmp(tablename, "nat") != 0) {

                DEBUGP("SNAT: wrong table %s\n", tablename);

                return 0;

        }

        if (hook_mask & ~(1 << NF_IP_POST_ROUTING)) {

                DEBUGP("SNAT: hook mask 0x%x bad\n", hook_mask);

                return 0;

        }

        return 1;

}

static int ipt_dnat_checkentry(const char *tablename,

                               const struct ipt_entry *e,

                               void *targinfo,

                               unsigned int targinfosize,

                               unsigned int hook_mask)

{

        struct ip_nat_multi_range *mr = targinfo;

        /* Must be a valid range */

        if (targinfosize < sizeof(struct ip_nat_multi_range)) {

                DEBUGP("DNAT: Target size %u too small\n", targinfosize);

                return 0;

        }

        if (targinfosize != IPT_ALIGN((sizeof(struct ip_nat_multi_range)

                                       + (sizeof(struct ip_nat_range)

                                          * (mr->rangesize - 1))))) {

                DEBUGP("DNAT: Target size %u wrong for %u ranges\n",

                       targinfosize, mr->rangesize);

                return 0;

        }

        /* Only allow these for NAT. */

        if (strcmp(tablename, "nat") != 0) {

                DEBUGP("DNAT: wrong table %s\n", tablename);

                return 0;

        }

        if (hook_mask & ~((1 << NF_IP_PRE_ROUTING) | (1 << NF_IP_LOCAL_OUT))) {

                DEBUGP("DNAT: hook mask 0x%x bad\n", hook_mask);

                return 0;

        }

#ifndef CONFIG_IP_NF_NAT_LOCAL

        if (hook_mask & (1 << NF_IP_LOCAL_OUT)) {

                DEBUGP("DNAT: CONFIG_IP_NF_NAT_LOCAL not enabled\n");

                return 0;

        }

#endif

        return 1;

}

inline unsigned int

alloc_null_binding(struct ip_conntrack *conntrack,

                   struct ip_nat_info *info,

                   unsigned int hooknum)

{

        /* Force range to this IP; let proto decide mapping for

           per-proto parts (hence not IP_NAT_RANGE_PROTO_SPECIFIED).

           Use reply in case it's already been mangled (eg local packet).

        */

        u_int32_t ip

                = (HOOK2MANIP(hooknum) == IP_NAT_MANIP_SRC

                   ? conntrack->tuplehash[IP_CT_DIR_REPLY].tuple.dst.ip

                   : conntrack->tuplehash[IP_CT_DIR_REPLY].tuple.src.ip);

        struct ip_nat_multi_range mr

                = { 1, { { IP_NAT_RANGE_MAP_IPS, ip, ip, { 0 }, { 0 } } } };

        DEBUGP("Allocating NULL binding for %p (%u.%u.%u.%u)\n", conntrack,

               NIPQUAD(ip));

        return ip_nat_setup_info(conntrack, &mr, hooknum);

}

int ip_nat_rule_find(struct sk_buff **pskb,

                     unsigned int hooknum,

                     const struct net_device *in,

                     const struct net_device *out,

                     struct ip_conntrack *ct,

                     struct ip_nat_info *info)

{

        int ret;

        ret = ipt_do_table(pskb, hooknum, in, out, &nat_table, NULL);

        if (ret == NF_ACCEPT) {

                if (!(info->initialized & (1 << HOOK2MANIP(hooknum))))

                        /* NUL mapping */

                        ret = alloc_null_binding(ct, info, hooknum);

        }

        return ret;

}

static struct ipt_target ipt_snat_reg

= { { NULL, NULL }, "SNAT", ipt_snat_target, ipt_snat_checkentry, NULL };

static struct ipt_target ipt_dnat_reg

= { { NULL, NULL }, "DNAT", ipt_dnat_target, ipt_dnat_checkentry, NULL };

int __init ip_nat_rule_init(void)

{

        int ret;

        ret = ipt_register_table(&nat_table);

        if (ret != 0)

                return ret;

        ret = ipt_register_target(&ipt_snat_reg);

        if (ret != 0)

                goto unregister_table;

        ret = ipt_register_target(&ipt_dnat_reg);

        if (ret != 0)

                goto unregister_snat;

        return ret;

 unregister_snat:

        ipt_unregister_target(&ipt_snat_reg);

 unregister_table:

        ipt_unregister_table(&nat_table);

        return ret;

}

void ip_nat_rule_cleanup(void)

{

        ipt_unregister_target(&ipt_dnat_reg);

        ipt_unregister_target(&ipt_snat_reg);

        ipt_unregister_table(&nat_table);

}