/*-
 * SPDX-License-Identifier: BSD-2-Clause
 *
 * Copyright (c) 2019 Yandex LLC
 * Copyright (c) 2019 Andrey V. Elsukov <ae@FreeBSD.org>
 * Copyright (c) 2019 Boris N. Lytochkin <lytboris@gmail.com>
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/counter.h>
#include <sys/errno.h>
#include <sys/kernel.h>
#include <sys/lock.h>
#include <sys/malloc.h>
#include <sys/mbuf.h>
#include <sys/module.h>
#include <sys/rmlock.h>
#include <sys/rwlock.h>
#include <sys/socket.h>
#include <sys/sockopt.h>
#include <sys/syslog.h>
#include <sys/sysctl.h>

#include <net/if.h>
#include <net/if_var.h>
#include <net/route.h>
#include <net/vnet.h>

#include <netinet/in.h>
#include <netinet/ip_var.h>
#include <netinet/ip_fw.h>
#include <netinet6/in6_var.h>
#include <netinet6/ip6_var.h>
#include <netinet6/ip_fw_nat64.h>

#include <netpfil/ipfw/ip_fw_private.h>

#include "nat64clat.h"

VNET_DEFINE(uint32_t, nat64clat_eid) = 0;

static struct nat64clat_cfg *nat64clat_alloc_config(const char *name,
    uint8_t set);
static void nat64clat_free_config(struct nat64clat_cfg *cfg);
static struct nat64clat_cfg *nat64clat_find(struct namedobj_instance *ni,
    const char *name, uint8_t set);

static struct nat64clat_cfg *
nat64clat_alloc_config(const char *name, uint8_t set)
{
        struct nat64clat_cfg *cfg;

        cfg = malloc(sizeof(struct nat64clat_cfg), M_IPFW, M_WAITOK | M_ZERO);
        COUNTER_ARRAY_ALLOC(cfg->base.stats.cnt, NAT64STATS, M_WAITOK);
        cfg->no.name = cfg->name;
        cfg->no.etlv = IPFW_TLV_NAT64CLAT_NAME;
        cfg->no.set = set;
        strlcpy(cfg->name, name, sizeof(cfg->name));
        return (cfg);
}

static void
nat64clat_free_config(struct nat64clat_cfg *cfg)
{

        COUNTER_ARRAY_FREE(cfg->base.stats.cnt, NAT64STATS);
        free(cfg, M_IPFW);
}

static void
nat64clat_export_config(struct ip_fw_chain *ch, struct nat64clat_cfg *cfg,
    ipfw_nat64clat_cfg *uc)
{
        uc->plat_prefix = cfg->base.plat_prefix;
        uc->plat_plen = cfg->base.plat_plen;
        uc->clat_prefix = cfg->base.clat_prefix;
        uc->clat_plen = cfg->base.clat_plen;
        uc->flags = cfg->base.flags & NAT64CLAT_FLAGSMASK;
        uc->set = cfg->no.set;
        strlcpy(uc->name, cfg->no.name, sizeof(uc->name));
}

struct nat64clat_dump_arg {
        struct ip_fw_chain *ch;
        struct sockopt_data *sd;
};

static int
export_config_cb(struct namedobj_instance *ni, struct named_object *no,
    void *arg)
{
        struct nat64clat_dump_arg *da = (struct nat64clat_dump_arg *)arg;
        ipfw_nat64clat_cfg *uc;

        uc = (ipfw_nat64clat_cfg *)ipfw_get_sopt_space(da->sd, sizeof(*uc));
        nat64clat_export_config(da->ch, (struct nat64clat_cfg *)no, uc);
        return (0);
}

static struct nat64clat_cfg *
nat64clat_find(struct namedobj_instance *ni, const char *name, uint8_t set)
{
        struct nat64clat_cfg *cfg;

        cfg = (struct nat64clat_cfg *)ipfw_objhash_lookup_name_type(ni, set,
            IPFW_TLV_NAT64CLAT_NAME, name);

        return (cfg);
}

/*
 * Creates new consumer-side nat64 translator instance.
 * Data layout (v0)(current):
 * Request: [ ipfw_obj_lheader ipfw_nat64clat_cfg ]
 *
 * Returns 0 on success
 */
static int
nat64clat_create(struct ip_fw_chain *ch, ip_fw3_opheader *op3,
    struct sockopt_data *sd)
{
        ipfw_obj_lheader *olh;
        ipfw_nat64clat_cfg *uc;
        struct namedobj_instance *ni;
        struct nat64clat_cfg *cfg;

        if (sd->valsize != sizeof(*olh) + sizeof(*uc))
                return (EINVAL);

        olh = (ipfw_obj_lheader *)sd->kbuf;
        uc = (ipfw_nat64clat_cfg *)(olh + 1);

        if (ipfw_check_object_name_generic(uc->name) != 0)
                return (EINVAL);

        if (uc->set >= IPFW_MAX_SETS ||
            nat64_check_prefix6(&uc->plat_prefix, uc->plat_plen) != 0 ||
            nat64_check_prefix6(&uc->clat_prefix, uc->clat_plen) != 0)
                return (EINVAL);

        ni = CHAIN_TO_SRV(ch);

        IPFW_UH_RLOCK(ch);
        if (nat64clat_find(ni, uc->name, uc->set) != NULL) {
                IPFW_UH_RUNLOCK(ch);
                return (EEXIST);
        }
        IPFW_UH_RUNLOCK(ch);

        cfg = nat64clat_alloc_config(uc->name, uc->set);
        cfg->base.plat_prefix = uc->plat_prefix;
        cfg->base.plat_plen = uc->plat_plen;
        cfg->base.clat_prefix = uc->clat_prefix;
        cfg->base.clat_plen = uc->clat_plen;
        cfg->base.flags = (uc->flags & NAT64CLAT_FLAGSMASK) |
            NAT64_CLATPFX | NAT64_PLATPFX;
        if (IN6_IS_ADDR_WKPFX(&cfg->base.plat_prefix))
                cfg->base.flags |= NAT64_WKPFX;

        IPFW_UH_WLOCK(ch);

        if (nat64clat_find(ni, uc->name, uc->set) != NULL) {
                IPFW_UH_WUNLOCK(ch);
                nat64clat_free_config(cfg);
                return (EEXIST);
        }

        if (ipfw_objhash_alloc_idx(ni, &cfg->no.kidx) != 0) {
                IPFW_UH_WUNLOCK(ch);
                nat64clat_free_config(cfg);
                return (ENOSPC);
        }
        ipfw_objhash_add(CHAIN_TO_SRV(ch), &cfg->no);
        /* Okay, let's link data */
        SRV_OBJECT(ch, cfg->no.kidx) = cfg;
        IPFW_UH_WUNLOCK(ch);

        return (0);
}

/*
 * Change existing nat64clat instance configuration.
 * Data layout (v0)(current):
 * Request: [ ipfw_obj_header ipfw_nat64clat_cfg ]
 * Reply: [ ipfw_obj_header ipfw_nat64clat_cfg ]
 *
 * Returns 0 on success
 */
static int
nat64clat_config(struct ip_fw_chain *ch, ip_fw3_opheader *op,
    struct sockopt_data *sd)
{
        ipfw_obj_header *oh;
        ipfw_nat64clat_cfg *uc;
        struct nat64clat_cfg *cfg;
        struct namedobj_instance *ni;
        uint32_t flags;

        if (sd->valsize != sizeof(*oh) + sizeof(*uc))
                return (EINVAL);

        oh = (ipfw_obj_header *)ipfw_get_sopt_space(sd,
            sizeof(*oh) + sizeof(*uc));
        uc = (ipfw_nat64clat_cfg *)(oh + 1);

        if (ipfw_check_object_name_generic(oh->ntlv.name) != 0 ||
            oh->ntlv.set >= IPFW_MAX_SETS)
                return (EINVAL);

        ni = CHAIN_TO_SRV(ch);
        if (sd->sopt->sopt_dir == SOPT_GET) {
                IPFW_UH_RLOCK(ch);
                cfg = nat64clat_find(ni, oh->ntlv.name, oh->ntlv.set);
                if (cfg == NULL) {
                        IPFW_UH_RUNLOCK(ch);
                        return (ENOENT);
                }
                nat64clat_export_config(ch, cfg, uc);
                IPFW_UH_RUNLOCK(ch);
                return (0);
        }

        IPFW_UH_WLOCK(ch);
        cfg = nat64clat_find(ni, oh->ntlv.name, oh->ntlv.set);
        if (cfg == NULL) {
                IPFW_UH_WUNLOCK(ch);
                return (ENOENT);
        }

        /*
         * For now allow to change only following values:
         *  plat_prefix, plat_plen, clat_prefix, clat_plen, flags.
         */
        flags = 0;
        if (uc->plat_plen != cfg->base.plat_plen ||
            !IN6_ARE_ADDR_EQUAL(&uc->plat_prefix, &cfg->base.plat_prefix)) {
                if (nat64_check_prefix6(&uc->plat_prefix, uc->plat_plen) != 0) {
                        IPFW_UH_WUNLOCK(ch);
                        return (EINVAL);
                }
                flags |= NAT64_PLATPFX;
        }

        if (uc->clat_plen != cfg->base.clat_plen ||
            !IN6_ARE_ADDR_EQUAL(&uc->clat_prefix, &cfg->base.clat_prefix)) {
                if (nat64_check_prefix6(&uc->clat_prefix, uc->clat_plen) != 0) {
                        IPFW_UH_WUNLOCK(ch);
                        return (EINVAL);
                }
                flags |= NAT64_CLATPFX;
        }

        if (flags != 0) {
                IPFW_WLOCK(ch);
                if (flags & NAT64_PLATPFX) {
                        cfg->base.plat_prefix = uc->plat_prefix;
                        cfg->base.plat_plen = uc->plat_plen;
                }
                if (flags & NAT64_CLATPFX) {
                        cfg->base.clat_prefix = uc->clat_prefix;
                        cfg->base.clat_plen = uc->clat_plen;
                }
                IPFW_WUNLOCK(ch);
        }

        cfg->base.flags &= ~NAT64CLAT_FLAGSMASK;
        cfg->base.flags |= uc->flags & NAT64CLAT_FLAGSMASK;

        IPFW_UH_WUNLOCK(ch);
        return (0);
}

static void
nat64clat_detach_config(struct ip_fw_chain *ch, struct nat64clat_cfg *cfg)
{

        IPFW_UH_WLOCK_ASSERT(ch);

        ipfw_objhash_del(CHAIN_TO_SRV(ch), &cfg->no);
        ipfw_objhash_free_idx(CHAIN_TO_SRV(ch), cfg->no.kidx);
}

/*
 * Destroys nat64 instance.
 * Data layout (v0)(current):
 * Request: [ ipfw_obj_header ]
 *
 * Returns 0 on success
 */
static int
nat64clat_destroy(struct ip_fw_chain *ch, ip_fw3_opheader *op3,
    struct sockopt_data *sd)
{
        ipfw_obj_header *oh;
        struct nat64clat_cfg *cfg;

        if (sd->valsize != sizeof(*oh))
                return (EINVAL);

        oh = (ipfw_obj_header *)sd->kbuf;
        if (ipfw_check_object_name_generic(oh->ntlv.name) != 0)
                return (EINVAL);

        IPFW_UH_WLOCK(ch);
        cfg = nat64clat_find(CHAIN_TO_SRV(ch), oh->ntlv.name, oh->ntlv.set);
        if (cfg == NULL) {
                IPFW_UH_WUNLOCK(ch);
                return (ENOENT);
        }
        if (cfg->no.refcnt > 0) {
                IPFW_UH_WUNLOCK(ch);
                return (EBUSY);
        }

        ipfw_reset_eaction_instance(ch, V_nat64clat_eid, cfg->no.kidx);
        SRV_OBJECT(ch, cfg->no.kidx) = NULL;
        nat64clat_detach_config(ch, cfg);
        IPFW_UH_WUNLOCK(ch);

        nat64clat_free_config(cfg);
        return (0);
}

/*
 * Lists all nat64clat instances currently available in kernel.
 * Data layout (v0)(current):
 * Request: [ ipfw_obj_lheader ]
 * Reply: [ ipfw_obj_lheader ipfw_nat64clat_cfg x N ]
 *
 * Returns 0 on success
 */
static int
nat64clat_list(struct ip_fw_chain *ch, ip_fw3_opheader *op3,
    struct sockopt_data *sd)
{
        ipfw_obj_lheader *olh;
        struct nat64clat_dump_arg da;

        /* Check minimum header size */
        if (sd->valsize < sizeof(ipfw_obj_lheader))
                return (EINVAL);

        olh = (ipfw_obj_lheader *)ipfw_get_sopt_header(sd, sizeof(*olh));

        IPFW_UH_RLOCK(ch);
        olh->count = ipfw_objhash_count_type(CHAIN_TO_SRV(ch),
            IPFW_TLV_NAT64CLAT_NAME);
        olh->objsize = sizeof(ipfw_nat64clat_cfg);
        olh->size = sizeof(*olh) + olh->count * olh->objsize;

        if (sd->valsize < olh->size) {
                IPFW_UH_RUNLOCK(ch);
                return (ENOMEM);
        }
        memset(&da, 0, sizeof(da));
        da.ch = ch;
        da.sd = sd;
        ipfw_objhash_foreach_type(CHAIN_TO_SRV(ch), export_config_cb,
            &da, IPFW_TLV_NAT64CLAT_NAME);
        IPFW_UH_RUNLOCK(ch);

        return (0);
}

#define __COPY_STAT_FIELD(_cfg, _stats, _field) \
        (_stats)->_field = NAT64STAT_FETCH(&(_cfg)->base.stats, _field)
static void
export_stats(struct ip_fw_chain *ch, struct nat64clat_cfg *cfg,
    struct ipfw_nat64clat_stats *stats)
{

        __COPY_STAT_FIELD(cfg, stats, opcnt64);
        __COPY_STAT_FIELD(cfg, stats, opcnt46);
        __COPY_STAT_FIELD(cfg, stats, ofrags);
        __COPY_STAT_FIELD(cfg, stats, ifrags);
        __COPY_STAT_FIELD(cfg, stats, oerrors);
        __COPY_STAT_FIELD(cfg, stats, noroute4);
        __COPY_STAT_FIELD(cfg, stats, noroute6);
        __COPY_STAT_FIELD(cfg, stats, noproto);
        __COPY_STAT_FIELD(cfg, stats, nomem);
        __COPY_STAT_FIELD(cfg, stats, dropped);
}

/*
 * Get nat64clat statistics.
 * Data layout (v0)(current):
 * Request: [ ipfw_obj_header ]
 * Reply: [ ipfw_obj_header ipfw_obj_ctlv [ uint64_t x N ]]
 *
 * Returns 0 on success
 */
static int
nat64clat_stats(struct ip_fw_chain *ch, ip_fw3_opheader *op,
    struct sockopt_data *sd)
{
        struct ipfw_nat64clat_stats stats;
        struct nat64clat_cfg *cfg;
        ipfw_obj_header *oh;
        ipfw_obj_ctlv *ctlv;
        size_t sz;

        sz = sizeof(ipfw_obj_header) + sizeof(ipfw_obj_ctlv) + sizeof(stats);
        if (sd->valsize % sizeof(uint64_t))
                return (EINVAL);
        if (sd->valsize < sz)
                return (ENOMEM);
        oh = (ipfw_obj_header *)ipfw_get_sopt_header(sd, sz);
        if (oh == NULL)
                return (EINVAL);
        memset(&stats, 0, sizeof(stats));

        IPFW_UH_RLOCK(ch);
        cfg = nat64clat_find(CHAIN_TO_SRV(ch), oh->ntlv.name, oh->ntlv.set);
        if (cfg == NULL) {
                IPFW_UH_RUNLOCK(ch);
                return (ENOENT);
        }
        export_stats(ch, cfg, &stats);
        IPFW_UH_RUNLOCK(ch);

        ctlv = (ipfw_obj_ctlv *)(oh + 1);
        memset(ctlv, 0, sizeof(*ctlv));
        ctlv->head.type = IPFW_TLV_COUNTERS;
        ctlv->head.length = sz - sizeof(ipfw_obj_header);
        ctlv->count = sizeof(stats) / sizeof(uint64_t);
        ctlv->objsize = sizeof(uint64_t);
        ctlv->version = IPFW_NAT64_VERSION;
        memcpy(ctlv + 1, &stats, sizeof(stats));
        return (0);
}

/*
 * Reset nat64clat statistics.
 * Data layout (v0)(current):
 * Request: [ ipfw_obj_header ]
 *
 * Returns 0 on success
 */
static int
nat64clat_reset_stats(struct ip_fw_chain *ch, ip_fw3_opheader *op,
    struct sockopt_data *sd)
{
        struct nat64clat_cfg *cfg;
        ipfw_obj_header *oh;

        if (sd->valsize != sizeof(*oh))
                return (EINVAL);
        oh = (ipfw_obj_header *)sd->kbuf;
        if (ipfw_check_object_name_generic(oh->ntlv.name) != 0 ||
            oh->ntlv.set >= IPFW_MAX_SETS)
                return (EINVAL);

        IPFW_UH_WLOCK(ch);
        cfg = nat64clat_find(CHAIN_TO_SRV(ch), oh->ntlv.name, oh->ntlv.set);
        if (cfg == NULL) {
                IPFW_UH_WUNLOCK(ch);
                return (ENOENT);
        }
        COUNTER_ARRAY_ZERO(cfg->base.stats.cnt, NAT64STATS);
        IPFW_UH_WUNLOCK(ch);
        return (0);
}

static struct ipfw_sopt_handler scodes[] = {
    { IP_FW_NAT64CLAT_CREATE,   IP_FW3_OPVER, HDIR_SET, nat64clat_create },
    { IP_FW_NAT64CLAT_DESTROY,  IP_FW3_OPVER, HDIR_SET, nat64clat_destroy },
    { IP_FW_NAT64CLAT_CONFIG,   IP_FW3_OPVER, HDIR_BOTH, nat64clat_config },
    { IP_FW_NAT64CLAT_LIST,     IP_FW3_OPVER, HDIR_GET, nat64clat_list },
    { IP_FW_NAT64CLAT_STATS,    IP_FW3_OPVER, HDIR_GET, nat64clat_stats },
    { IP_FW_NAT64CLAT_RESET_STATS, IP_FW3_OPVER, HDIR_SET, nat64clat_reset_stats },
};

static int
nat64clat_manage_sets(struct ip_fw_chain *ch, uint32_t set, uint8_t new_set,
    enum ipfw_sets_cmd cmd)
{

        return (ipfw_obj_manage_sets(CHAIN_TO_SRV(ch),
            IPFW_TLV_NAT64CLAT_NAME, set, new_set, cmd));
}
NAT64_DEFINE_OPCODE_REWRITER(nat64clat, NAT64CLAT, opcodes);

static int
destroy_config_cb(struct namedobj_instance *ni, struct named_object *no,
    void *arg)
{
        struct nat64clat_cfg *cfg;
        struct ip_fw_chain *ch;

        ch = (struct ip_fw_chain *)arg;
        cfg = (struct nat64clat_cfg *)SRV_OBJECT(ch, no->kidx);
        SRV_OBJECT(ch, no->kidx) = NULL;
        nat64clat_detach_config(ch, cfg);
        nat64clat_free_config(cfg);
        return (0);
}

int
nat64clat_init(struct ip_fw_chain *ch, int first)
{

        V_nat64clat_eid = ipfw_add_eaction(ch, ipfw_nat64clat, "nat64clat");
        if (V_nat64clat_eid == 0)
                return (ENXIO);
        IPFW_ADD_SOPT_HANDLER(first, scodes);
        IPFW_ADD_OBJ_REWRITER(first, opcodes);
        return (0);
}

void
nat64clat_uninit(struct ip_fw_chain *ch, int last)
{

        IPFW_DEL_OBJ_REWRITER(last, opcodes);
        IPFW_DEL_SOPT_HANDLER(last, scodes);
        ipfw_del_eaction(ch, V_nat64clat_eid);
        /*
         * Since we already have deregistered external action,
         * our named objects become unaccessible via rules, because
         * all rules were truncated by ipfw_del_eaction().
         * So, we can unlink and destroy our named objects without holding
         * IPFW_WLOCK().
         */
        IPFW_UH_WLOCK(ch);
        ipfw_objhash_foreach_type(CHAIN_TO_SRV(ch), destroy_config_cb, ch,
            IPFW_TLV_NAT64CLAT_NAME);
        V_nat64clat_eid = 0;
        IPFW_UH_WUNLOCK(ch);
}