/*-
 * SPDX-License-Identifier: BSD-2-Clause
 *
 * Copyright (c) 2015-2019 Yandex LLC
 * Copyright (c) 2015-2019 Andrey V. Elsukov <ae@FreeBSD.org>
 *
 * 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/kernel.h>
#include <sys/lock.h>
#include <sys/mbuf.h>
#include <sys/module.h>
#include <sys/rmlock.h>
#include <sys/rwlock.h>
#include <sys/socket.h>
#include <sys/sysctl.h>

#include <net/if.h>
#include <net/if_var.h>
#include <net/if_pflog.h>
#include <net/pfil.h>

#include <netinet/in.h>
#include <netinet/ip.h>
#include <netinet/ip_icmp.h>
#include <netinet/ip_var.h>
#include <netinet/ip_fw.h>
#include <netinet/ip6.h>
#include <netinet/icmp6.h>
#include <netinet6/ip_fw_nat64.h>

#include <netpfil/ipfw/ip_fw_private.h>
#include <netpfil/pf/pf.h>

#include "nat64stl.h"

#define NAT64_LOOKUP(chain, cmd)        \
    (struct nat64stl_cfg *)SRV_OBJECT((chain), insntod(cmd, kidx)->kidx)

static void
nat64stl_log(struct pfloghdr *plog, struct mbuf *m, sa_family_t family,
    uint32_t kidx)
{
        static uint32_t pktid = 0;

        memset(plog, 0, sizeof(*plog));
        plog->length = PFLOG_REAL_HDRLEN;
        plog->af = family;
        plog->action = PF_NAT;
        plog->dir = PF_IN;
        plog->rulenr = htonl(kidx);
        pktid++;
        plog->subrulenr = htonl(pktid);
        plog->ruleset[0] = '\0';
        strlcpy(plog->ifname, "NAT64STL", sizeof(plog->ifname));
        ipfw_pflog_tap(plog, m);
}

static int
nat64stl_handle_ip4(struct ip_fw_chain *chain, struct nat64stl_cfg *cfg,
    struct mbuf *m, uint32_t tablearg)
{
        struct pfloghdr loghdr, *logdata;
        struct in6_addr saddr, daddr;
        struct ip *ip;

        ip = mtod(m, struct ip*);
        if (nat64_check_ip4(ip->ip_src.s_addr) != 0 ||
            nat64_check_ip4(ip->ip_dst.s_addr) != 0 ||
            nat64_check_private_ip4(&cfg->base, ip->ip_src.s_addr) != 0 ||
            nat64_check_private_ip4(&cfg->base, ip->ip_dst.s_addr) != 0)
                return (NAT64SKIP);

        daddr = TARG_VAL(chain, tablearg, nh6);
        if (nat64_check_ip6(&daddr) != 0)
                return (NAT64MFREE);

        saddr = cfg->base.plat_prefix;
        nat64_embed_ip4(&saddr, cfg->base.plat_plen, ip->ip_src.s_addr);
        if (cfg->base.flags & NAT64_LOG) {
                logdata = &loghdr;
                nat64stl_log(logdata, m, AF_INET, cfg->no.kidx);
        } else
                logdata = NULL;
        return (nat64_do_handle_ip4(m, &saddr, &daddr, 0, &cfg->base,
            logdata));
}

static int
nat64stl_handle_ip6(struct ip_fw_chain *chain, struct nat64stl_cfg *cfg,
    struct mbuf *m, uint32_t tablearg)
{
        struct pfloghdr loghdr, *logdata;
        struct ip6_hdr *ip6;
        uint32_t aaddr;

        aaddr = htonl(TARG_VAL(chain, tablearg, nh4));
        if (nat64_check_private_ip4(&cfg->base, aaddr) != 0) {
                NAT64STAT_INC(&cfg->base.stats, dropped);
                return (NAT64MFREE);
        }
        /*
         * NOTE: we expect ipfw_chk() did m_pullup() up to upper level
         * protocol's headers. Also we skip some checks, that ip6_input(),
         * ip6_forward(), ip6_fastfwd() and ipfw_chk() already did.
         */
        ip6 = mtod(m, struct ip6_hdr *);
        /* Check ip6_dst matches configured prefix */
        if (memcmp(&ip6->ip6_dst, &cfg->base.plat_prefix,
            cfg->base.plat_plen / 8) != 0)
                return (NAT64SKIP);

        if (cfg->base.flags & NAT64_LOG) {
                logdata = &loghdr;
                nat64stl_log(logdata, m, AF_INET6, cfg->no.kidx);
        } else
                logdata = NULL;
        return (nat64_do_handle_ip6(m, aaddr, 0, &cfg->base, logdata));
}

static int
nat64stl_handle_icmp6(struct ip_fw_chain *chain, struct nat64stl_cfg *cfg,
    struct mbuf *m)
{
        struct pfloghdr loghdr, *logdata;
        struct nat64_counters *stats;
        struct ip6_hdr *ip6i;
        struct icmp6_hdr *icmp6;
        uint32_t tablearg;
        int hlen, proto;

        hlen = 0;
        stats = &cfg->base.stats;
        proto = nat64_getlasthdr(m, &hlen);
        if (proto != IPPROTO_ICMPV6) {
                NAT64STAT_INC(stats, dropped);
                return (NAT64MFREE);
        }
        icmp6 = mtodo(m, hlen);
        switch (icmp6->icmp6_type) {
        case ICMP6_DST_UNREACH:
        case ICMP6_PACKET_TOO_BIG:
        case ICMP6_TIME_EXCEED_TRANSIT:
        case ICMP6_PARAM_PROB:
                break;
        default:
                NAT64STAT_INC(stats, dropped);
                return (NAT64MFREE);
        }
        hlen += sizeof(struct icmp6_hdr);
        if (m->m_pkthdr.len < hlen + sizeof(struct ip6_hdr) + ICMP_MINLEN) {
                NAT64STAT_INC(stats, dropped);
                return (NAT64MFREE);
        }
        if (m->m_len < hlen + sizeof(struct ip6_hdr) + ICMP_MINLEN)
                m = m_pullup(m, hlen + sizeof(struct ip6_hdr) + ICMP_MINLEN);
        if (m == NULL) {
                NAT64STAT_INC(stats, nomem);
                return (NAT64RETURN);
        }
        /*
         * Use destination address from inner IPv6 header to determine
         * IPv4 mapped address.
         */
        ip6i = mtodo(m, hlen);
        if (ipfw_lookup_table(chain, cfg->map64,
            sizeof(struct in6_addr), &ip6i->ip6_dst, &tablearg) == 0) {
                m_freem(m);
                return (NAT64RETURN);
        }
        if (cfg->base.flags & NAT64_LOG) {
                logdata = &loghdr;
                nat64stl_log(logdata, m, AF_INET6, cfg->no.kidx);
        } else
                logdata = NULL;
        return (nat64_handle_icmp6(m, 0,
            htonl(TARG_VAL(chain, tablearg, nh4)), 0, &cfg->base, logdata));
}

int
ipfw_nat64stl(struct ip_fw_chain *chain, struct ip_fw_args *args,
    ipfw_insn *cmd, int *done)
{
        struct nat64stl_cfg *cfg;
        ipfw_insn *icmd;
        in_addr_t dst4;
        uint32_t tablearg;
        int ret;

        IPFW_RLOCK_ASSERT(chain);

        *done = 0; /* try next rule if not matched */
        icmd = cmd + F_LEN(cmd);
        if (cmd->opcode != O_EXTERNAL_ACTION ||
            insntod(cmd, kidx)->kidx != V_nat64stl_eid ||
            icmd->opcode != O_EXTERNAL_INSTANCE ||
            (cfg = NAT64_LOOKUP(chain, icmd)) == NULL)
                return (0);

        switch (args->f_id.addr_type) {
        case 4:
                dst4 = htonl(args->f_id.dst_ip);
                ret = ipfw_lookup_table(chain, cfg->map46, sizeof(in_addr_t),
                    &dst4, &tablearg);
                break;
        case 6:
                ret = ipfw_lookup_table(chain, cfg->map64,
                    sizeof(struct in6_addr), &args->f_id.src_ip6, &tablearg);
                break;
        default:
                return (0);
        }
        if (ret == 0) {
                /*
                 * In case when packet is ICMPv6 message from an intermediate
                 * router, the source address of message will not match the
                 * addresses from our map64 table.
                 */
                if (args->f_id.proto != IPPROTO_ICMPV6)
                        return (0);

                ret = nat64stl_handle_icmp6(chain, cfg, args->m);
        } else {
                if (args->f_id.addr_type == 4)
                        ret = nat64stl_handle_ip4(chain, cfg, args->m,
                            tablearg);
                else
                        ret = nat64stl_handle_ip6(chain, cfg, args->m,
                            tablearg);
        }
        if (ret == NAT64SKIP)
                return (0);

        *done = 1; /* terminate the search */
        if (ret == NAT64MFREE)
                m_freem(args->m);
        args->m = NULL;
        return (IP_FW_NAT64);
}