// SPDX-License-Identifier: GPL-2.0-only
/*
 *      xt_conntrack - Netfilter module to match connection tracking
 *      information. (Superset of Rusty's minimalistic state match.)
 *
 *      (C) 2001  Marc Boucher (marc@mbsi.ca).
 *      (C) 2006-2012 Patrick McHardy <kaber@trash.net>
 *      Copyright © CC Computer Consultants GmbH, 2007 - 2008
 */
#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
#include <linux/module.h>
#include <linux/skbuff.h>
#include <net/ipv6.h>
#include <linux/netfilter/x_tables.h>
#include <linux/netfilter/xt_conntrack.h>
#include <net/netfilter/nf_conntrack.h>

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Marc Boucher <marc@mbsi.ca>");
MODULE_AUTHOR("Jan Engelhardt <jengelh@medozas.de>");
MODULE_DESCRIPTION("Xtables: connection tracking state match");
MODULE_ALIAS("ipt_conntrack");
MODULE_ALIAS("ip6t_conntrack");

static bool
conntrack_addrcmp(const union nf_inet_addr *kaddr,
                  const union nf_inet_addr *uaddr,
                  const union nf_inet_addr *umask, unsigned int l3proto)
{
        if (l3proto == NFPROTO_IPV4)
                return ((kaddr->ip ^ uaddr->ip) & umask->ip) == 0;
        else if (l3proto == NFPROTO_IPV6)
                return ipv6_masked_addr_cmp(&kaddr->in6, &umask->in6,
                       &uaddr->in6) == 0;
        else
                return false;
}

static inline bool
conntrack_mt_origsrc(const struct nf_conn *ct,
                     const struct xt_conntrack_mtinfo2 *info,
                     u_int8_t family)
{
        return conntrack_addrcmp(&ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.src.u3,
               &info->origsrc_addr, &info->origsrc_mask, family);
}

static inline bool
conntrack_mt_origdst(const struct nf_conn *ct,
                     const struct xt_conntrack_mtinfo2 *info,
                     u_int8_t family)
{
        return conntrack_addrcmp(&ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple.dst.u3,
               &info->origdst_addr, &info->origdst_mask, family);
}

static inline bool
conntrack_mt_replsrc(const struct nf_conn *ct,
                     const struct xt_conntrack_mtinfo2 *info,
                     u_int8_t family)
{
        return conntrack_addrcmp(&ct->tuplehash[IP_CT_DIR_REPLY].tuple.src.u3,
               &info->replsrc_addr, &info->replsrc_mask, family);
}

static inline bool
conntrack_mt_repldst(const struct nf_conn *ct,
                     const struct xt_conntrack_mtinfo2 *info,
                     u_int8_t family)
{
        return conntrack_addrcmp(&ct->tuplehash[IP_CT_DIR_REPLY].tuple.dst.u3,
               &info->repldst_addr, &info->repldst_mask, family);
}

static inline bool
ct_proto_port_check(const struct xt_conntrack_mtinfo2 *info,
                    const struct nf_conn *ct)
{
        const struct nf_conntrack_tuple *tuple;

        tuple = &ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple;
        if ((info->match_flags & XT_CONNTRACK_PROTO) &&
            (nf_ct_protonum(ct) == info->l4proto) ^
            !(info->invert_flags & XT_CONNTRACK_PROTO))
                return false;

        /* Shortcut to match all recognized protocols by using ->src.all. */
        if ((info->match_flags & XT_CONNTRACK_ORIGSRC_PORT) &&
            (tuple->src.u.all == info->origsrc_port) ^
            !(info->invert_flags & XT_CONNTRACK_ORIGSRC_PORT))
                return false;

        if ((info->match_flags & XT_CONNTRACK_ORIGDST_PORT) &&
            (tuple->dst.u.all == info->origdst_port) ^
            !(info->invert_flags & XT_CONNTRACK_ORIGDST_PORT))
                return false;

        tuple = &ct->tuplehash[IP_CT_DIR_REPLY].tuple;

        if ((info->match_flags & XT_CONNTRACK_REPLSRC_PORT) &&
            (tuple->src.u.all == info->replsrc_port) ^
            !(info->invert_flags & XT_CONNTRACK_REPLSRC_PORT))
                return false;

        if ((info->match_flags & XT_CONNTRACK_REPLDST_PORT) &&
            (tuple->dst.u.all == info->repldst_port) ^
            !(info->invert_flags & XT_CONNTRACK_REPLDST_PORT))
                return false;

        return true;
}

static inline bool
port_match(u16 min, u16 max, u16 port, bool invert)
{
        return (port >= min && port <= max) ^ invert;
}

static inline bool
ct_proto_port_check_v3(const struct xt_conntrack_mtinfo3 *info,
                       const struct nf_conn *ct)
{
        const struct nf_conntrack_tuple *tuple;

        tuple = &ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple;
        if ((info->match_flags & XT_CONNTRACK_PROTO) &&
            (nf_ct_protonum(ct) == info->l4proto) ^
            !(info->invert_flags & XT_CONNTRACK_PROTO))
                return false;

        /* Shortcut to match all recognized protocols by using ->src.all. */
        if ((info->match_flags & XT_CONNTRACK_ORIGSRC_PORT) &&
            !port_match(info->origsrc_port, info->origsrc_port_high,
                        ntohs(tuple->src.u.all),
                        info->invert_flags & XT_CONNTRACK_ORIGSRC_PORT))
                return false;

        if ((info->match_flags & XT_CONNTRACK_ORIGDST_PORT) &&
            !port_match(info->origdst_port, info->origdst_port_high,
                        ntohs(tuple->dst.u.all),
                        info->invert_flags & XT_CONNTRACK_ORIGDST_PORT))
                return false;

        tuple = &ct->tuplehash[IP_CT_DIR_REPLY].tuple;

        if ((info->match_flags & XT_CONNTRACK_REPLSRC_PORT) &&
            !port_match(info->replsrc_port, info->replsrc_port_high,
                        ntohs(tuple->src.u.all),
                        info->invert_flags & XT_CONNTRACK_REPLSRC_PORT))
                return false;

        if ((info->match_flags & XT_CONNTRACK_REPLDST_PORT) &&
            !port_match(info->repldst_port, info->repldst_port_high,
                        ntohs(tuple->dst.u.all),
                        info->invert_flags & XT_CONNTRACK_REPLDST_PORT))
                return false;

        return true;
}

static bool
conntrack_mt(const struct sk_buff *skb, struct xt_action_param *par,
             u16 state_mask, u16 status_mask)
{
        const struct xt_conntrack_mtinfo2 *info = par->matchinfo;
        enum ip_conntrack_info ctinfo;
        const struct nf_conn *ct;
        unsigned int statebit;

        ct = nf_ct_get(skb, &ctinfo);

        if (ct)
                statebit = XT_CONNTRACK_STATE_BIT(ctinfo);
        else if (ctinfo == IP_CT_UNTRACKED)
                statebit = XT_CONNTRACK_STATE_UNTRACKED;
        else
                statebit = XT_CONNTRACK_STATE_INVALID;

        if (info->match_flags & XT_CONNTRACK_STATE) {
                if (ct != NULL) {
                        if (test_bit(IPS_SRC_NAT_BIT, &ct->status))
                                statebit |= XT_CONNTRACK_STATE_SNAT;
                        if (test_bit(IPS_DST_NAT_BIT, &ct->status))
                                statebit |= XT_CONNTRACK_STATE_DNAT;
                }
                if (!!(state_mask & statebit) ^
                    !(info->invert_flags & XT_CONNTRACK_STATE))
                        return false;
        }

        if (ct == NULL)
                return info->match_flags & XT_CONNTRACK_STATE;
        if ((info->match_flags & XT_CONNTRACK_DIRECTION) &&
            (CTINFO2DIR(ctinfo) == IP_CT_DIR_ORIGINAL) ^
            !(info->invert_flags & XT_CONNTRACK_DIRECTION))
                return false;

        if (info->match_flags & XT_CONNTRACK_ORIGSRC)
                if (conntrack_mt_origsrc(ct, info, xt_family(par)) ^
                    !(info->invert_flags & XT_CONNTRACK_ORIGSRC))
                        return false;

        if (info->match_flags & XT_CONNTRACK_ORIGDST)
                if (conntrack_mt_origdst(ct, info, xt_family(par)) ^
                    !(info->invert_flags & XT_CONNTRACK_ORIGDST))
                        return false;

        if (info->match_flags & XT_CONNTRACK_REPLSRC)
                if (conntrack_mt_replsrc(ct, info, xt_family(par)) ^
                    !(info->invert_flags & XT_CONNTRACK_REPLSRC))
                        return false;

        if (info->match_flags & XT_CONNTRACK_REPLDST)
                if (conntrack_mt_repldst(ct, info, xt_family(par)) ^
                    !(info->invert_flags & XT_CONNTRACK_REPLDST))
                        return false;

        if (par->match->revision != 3) {
                if (!ct_proto_port_check(info, ct))
                        return false;
        } else {
                if (!ct_proto_port_check_v3(par->matchinfo, ct))
                        return false;
        }

        if ((info->match_flags & XT_CONNTRACK_STATUS) &&
            (!!(status_mask & ct->status) ^
            !(info->invert_flags & XT_CONNTRACK_STATUS)))
                return false;

        if (info->match_flags & XT_CONNTRACK_EXPIRES) {
                unsigned long expires = nf_ct_expires(ct) / HZ;

                if ((expires >= info->expires_min &&
                    expires <= info->expires_max) ^
                    !(info->invert_flags & XT_CONNTRACK_EXPIRES))
                        return false;
        }
        return true;
}

static bool
conntrack_mt_v1(const struct sk_buff *skb, struct xt_action_param *par)
{
        const struct xt_conntrack_mtinfo1 *info = par->matchinfo;

        return conntrack_mt(skb, par, info->state_mask, info->status_mask);
}

static bool
conntrack_mt_v2(const struct sk_buff *skb, struct xt_action_param *par)
{
        const struct xt_conntrack_mtinfo2 *info = par->matchinfo;

        return conntrack_mt(skb, par, info->state_mask, info->status_mask);
}

static bool
conntrack_mt_v3(const struct sk_buff *skb, struct xt_action_param *par)
{
        const struct xt_conntrack_mtinfo3 *info = par->matchinfo;

        return conntrack_mt(skb, par, info->state_mask, info->status_mask);
}

static int conntrack_mt_check(const struct xt_mtchk_param *par)
{
        int ret;

        ret = nf_ct_netns_get(par->net, par->family);
        if (ret < 0)
                pr_info_ratelimited("cannot load conntrack support for proto=%u\n",
                                    par->family);
        return ret;
}

static void conntrack_mt_destroy(const struct xt_mtdtor_param *par)
{
        nf_ct_netns_put(par->net, par->family);
}

static struct xt_match conntrack_mt_reg[] __read_mostly = {
        {
                .name       = "conntrack",
                .revision   = 1,
                .family     = NFPROTO_UNSPEC,
                .matchsize  = sizeof(struct xt_conntrack_mtinfo1),
                .match      = conntrack_mt_v1,
                .checkentry = conntrack_mt_check,
                .destroy    = conntrack_mt_destroy,
                .me         = THIS_MODULE,
        },
        {
                .name       = "conntrack",
                .revision   = 2,
                .family     = NFPROTO_UNSPEC,
                .matchsize  = sizeof(struct xt_conntrack_mtinfo2),
                .match      = conntrack_mt_v2,
                .checkentry = conntrack_mt_check,
                .destroy    = conntrack_mt_destroy,
                .me         = THIS_MODULE,
        },
        {
                .name       = "conntrack",
                .revision   = 3,
                .family     = NFPROTO_UNSPEC,
                .matchsize  = sizeof(struct xt_conntrack_mtinfo3),
                .match      = conntrack_mt_v3,
                .checkentry = conntrack_mt_check,
                .destroy    = conntrack_mt_destroy,
                .me         = THIS_MODULE,
        },
};

static int __init conntrack_mt_init(void)
{
        return xt_register_matches(conntrack_mt_reg,
               ARRAY_SIZE(conntrack_mt_reg));
}

static void __exit conntrack_mt_exit(void)
{
        xt_unregister_matches(conntrack_mt_reg, ARRAY_SIZE(conntrack_mt_reg));
}

module_init(conntrack_mt_init);
module_exit(conntrack_mt_exit);