// SPDX-License-Identifier: GPL-2.0-only
/*
 *  ebt_ip
 *
 *      Authors:
 *      Bart De Schuymer <bdschuym@pandora.be>
 *
 *  April, 2002
 *
 *  Changes:
 *    added ip-sport and ip-dport
 *    Innominate Security Technologies AG <mhopf@innominate.com>
 *    September, 2002
 */
#include <linux/ip.h>
#include <net/ip.h>
#include <linux/in.h>
#include <linux/module.h>
#include <linux/netfilter/x_tables.h>
#include <linux/netfilter_bridge/ebtables.h>
#include <linux/netfilter_bridge/ebt_ip.h>

union pkthdr {
        struct {
                __be16 src;
                __be16 dst;
        } tcpudphdr;
        struct {
                u8 type;
                u8 code;
        } icmphdr;
        struct {
                u8 type;
        } igmphdr;
};

static bool
ebt_ip_mt(const struct sk_buff *skb, struct xt_action_param *par)
{
        const struct ebt_ip_info *info = par->matchinfo;
        const struct iphdr *ih;
        struct iphdr _iph;
        const union pkthdr *pptr;
        union pkthdr _pkthdr;

        ih = skb_header_pointer(skb, 0, sizeof(_iph), &_iph);
        if (ih == NULL)
                return false;
        if ((info->bitmask & EBT_IP_TOS) &&
            NF_INVF(info, EBT_IP_TOS, info->tos != ih->tos))
                return false;
        if ((info->bitmask & EBT_IP_SOURCE) &&
            NF_INVF(info, EBT_IP_SOURCE,
                    (ih->saddr & info->smsk) != info->saddr))
                return false;
        if ((info->bitmask & EBT_IP_DEST) &&
            NF_INVF(info, EBT_IP_DEST,
                    (ih->daddr & info->dmsk) != info->daddr))
                return false;
        if (info->bitmask & EBT_IP_PROTO) {
                if (NF_INVF(info, EBT_IP_PROTO, info->protocol != ih->protocol))
                        return false;
                if (!(info->bitmask & (EBT_IP_DPORT | EBT_IP_SPORT |
                                       EBT_IP_ICMP | EBT_IP_IGMP)))
                        return true;
                if (ntohs(ih->frag_off) & IP_OFFSET)
                        return false;

                /* min icmp/igmp headersize is 4, so sizeof(_pkthdr) is ok. */
                pptr = skb_header_pointer(skb, ih->ihl*4,
                                          sizeof(_pkthdr), &_pkthdr);
                if (pptr == NULL)
                        return false;
                if (info->bitmask & EBT_IP_DPORT) {
                        u32 dst = ntohs(pptr->tcpudphdr.dst);
                        if (NF_INVF(info, EBT_IP_DPORT,
                                    dst < info->dport[0] ||
                                    dst > info->dport[1]))
                                return false;
                }
                if (info->bitmask & EBT_IP_SPORT) {
                        u32 src = ntohs(pptr->tcpudphdr.src);
                        if (NF_INVF(info, EBT_IP_SPORT,
                                    src < info->sport[0] ||
                                    src > info->sport[1]))
                                return false;
                }
                if ((info->bitmask & EBT_IP_ICMP) &&
                    NF_INVF(info, EBT_IP_ICMP,
                            pptr->icmphdr.type < info->icmp_type[0] ||
                            pptr->icmphdr.type > info->icmp_type[1] ||
                            pptr->icmphdr.code < info->icmp_code[0] ||
                            pptr->icmphdr.code > info->icmp_code[1]))
                        return false;
                if ((info->bitmask & EBT_IP_IGMP) &&
                    NF_INVF(info, EBT_IP_IGMP,
                            pptr->igmphdr.type < info->igmp_type[0] ||
                            pptr->igmphdr.type > info->igmp_type[1]))
                        return false;
        }
        return true;
}

static int ebt_ip_mt_check(const struct xt_mtchk_param *par)
{
        const struct ebt_ip_info *info = par->matchinfo;
        const struct ebt_entry *e = par->entryinfo;

        if (e->ethproto != htons(ETH_P_IP) ||
           e->invflags & EBT_IPROTO)
                return -EINVAL;
        if (info->bitmask & ~EBT_IP_MASK || info->invflags & ~EBT_IP_MASK)
                return -EINVAL;
        if (info->bitmask & (EBT_IP_DPORT | EBT_IP_SPORT)) {
                if (info->invflags & EBT_IP_PROTO)
                        return -EINVAL;
                if (info->protocol != IPPROTO_TCP &&
                    info->protocol != IPPROTO_UDP &&
                    info->protocol != IPPROTO_UDPLITE &&
                    info->protocol != IPPROTO_SCTP &&
                    info->protocol != IPPROTO_DCCP)
                         return -EINVAL;
        }
        if (info->bitmask & EBT_IP_DPORT && info->dport[0] > info->dport[1])
                return -EINVAL;
        if (info->bitmask & EBT_IP_SPORT && info->sport[0] > info->sport[1])
                return -EINVAL;
        if (info->bitmask & EBT_IP_ICMP) {
                if ((info->invflags & EBT_IP_PROTO) ||
                    info->protocol != IPPROTO_ICMP)
                        return -EINVAL;
                if (info->icmp_type[0] > info->icmp_type[1] ||
                    info->icmp_code[0] > info->icmp_code[1])
                        return -EINVAL;
        }
        if (info->bitmask & EBT_IP_IGMP) {
                if ((info->invflags & EBT_IP_PROTO) ||
                    info->protocol != IPPROTO_IGMP)
                        return -EINVAL;
                if (info->igmp_type[0] > info->igmp_type[1])
                        return -EINVAL;
        }
        return 0;
}

static struct xt_match ebt_ip_mt_reg __read_mostly = {
        .name           = "ip",
        .revision       = 0,
        .family         = NFPROTO_BRIDGE,
        .match          = ebt_ip_mt,
        .checkentry     = ebt_ip_mt_check,
        .matchsize      = sizeof(struct ebt_ip_info),
        .me             = THIS_MODULE,
};

static int __init ebt_ip_init(void)
{
        return xt_register_match(&ebt_ip_mt_reg);
}

static void __exit ebt_ip_fini(void)
{
        xt_unregister_match(&ebt_ip_mt_reg);
}

module_init(ebt_ip_init);
module_exit(ebt_ip_fini);
MODULE_DESCRIPTION("Ebtables: IPv4 protocol packet match");
MODULE_LICENSE("GPL");