/*
 * Copyright (C) 2012 by Darren Reed.
 *
 * See the IPFILTER.LICENCE file for details on licencing.
 */

#if defined(KERNEL) || defined(_KERNEL)
# undef KERNEL
# undef _KERNEL
# define        KERNEL  1
# define        _KERNEL 1
#endif
#if defined(__FreeBSD__) && \
    !defined(KLD_MODULE) && !defined(IPFILTER_LKM)
# include "opt_inet6.h"
#endif
#include <sys/param.h>
#include <sys/eventhandler.h>
#include <sys/conf.h>
#include <sys/errno.h>
#include <sys/types.h>
#include <sys/file.h>
#include <sys/fcntl.h>
#include <sys/filio.h>
#include <sys/time.h>
#include <sys/systm.h>
#include <sys/dirent.h>
#if defined(__FreeBSD__)
# include <sys/jail.h>
#endif
#include <sys/malloc.h>
#include <sys/mbuf.h>
#include <sys/sockopt.h>
#include <sys/socket.h>
#include <sys/selinfo.h>
#include <net/if.h>
#include <net/if_var.h>
#include <net/netisr.h>
#include <net/route.h>
#include <net/route/nhop.h>
#include <netinet/in.h>
#include <netinet/in_fib.h>
#include <netinet/in_pcb.h>
#include <netinet/in_var.h>
#include <netinet/in_systm.h>
#include <netinet/ip.h>
#include <netinet/ip_var.h>
#include <netinet/tcp.h>
#include <netinet/tcp_var.h>
#include <net/vnet.h>
#include <netinet/udp.h>
#include <netinet/tcpip.h>
#include <netinet/ip_icmp.h>
#include "netinet/ip_compat.h"
#ifdef USE_INET6
# include <netinet/icmp6.h>
#endif
#include "netinet/ip_fil.h"
#include "netinet/ip_nat.h"
#include "netinet/ip_frag.h"
#include "netinet/ip_state.h"
#include "netinet/ip_proxy.h"
#include "netinet/ip_auth.h"
#include "netinet/ip_sync.h"
#include "netinet/ip_lookup.h"
#include "netinet/ip_dstlist.h"
#ifdef  IPFILTER_SCAN
# include "netinet/ip_scan.h"
#endif
#include "netinet/ip_pool.h"
#include <sys/malloc.h>
#include <sys/kernel.h>
#ifdef CSUM_DATA_VALID
# include <machine/in_cksum.h>
#endif
extern  int     ip_optcopy(struct ip *, struct ip *);

#ifdef IPFILTER_M_IPFILTER
MALLOC_DEFINE(M_IPFILTER, "ipfilter", "IP Filter packet filter data structures");
#endif


static  int     ipf_send_ip(fr_info_t *, mb_t *);
static void     ipf_timer_func(void *arg);

VNET_DEFINE(ipf_main_softc_t, ipfmain) = {
        .ipf_running            = -2,
};
#define V_ipfmain               VNET(ipfmain)
#define V0_ipfmain              VNET_VNET(vnet0,ipfmain)

#include <sys/conf.h>
#include <net/pfil.h>

VNET_DEFINE_STATIC(eventhandler_tag, ipf_arrivetag);
VNET_DEFINE_STATIC(eventhandler_tag, ipf_departtag);
VNET_DEFINE_STATIC(eventhandler_tag, ipf_renametag);
#define V_ipf_arrivetag         VNET(ipf_arrivetag)
#define V_ipf_departtag         VNET(ipf_departtag)
#define V_ipf_renametag         VNET(ipf_renametag)

static void ipf_ifevent(void *arg, struct ifnet *ifp);

static void ipf_ifevent(void *arg, struct ifnet *ifp)
{

        CURVNET_SET(ifp->if_vnet);
        if (V_ipfmain.ipf_running > 0)
                ipf_sync(&V_ipfmain, NULL);
        CURVNET_RESTORE();
}



static pfil_return_t
ipf_check_wrapper(struct mbuf **mp, struct ifnet *ifp, int flags,
    void *ruleset __unused, struct inpcb *inp)
{
        struct ip *ip = mtod(*mp, struct ip *);
        pfil_return_t rv;

        CURVNET_SET(ifp->if_vnet);
        rv = ipf_check(&V_ipfmain, ip, ip->ip_hl << 2, ifp,
            !!(flags & PFIL_OUT), mp);
        CURVNET_RESTORE();
        if (rv == 0 && *mp == NULL)
                return (PFIL_CONSUMED);
        return (rv == 0 ? PFIL_PASS : PFIL_DROPPED);
}

#ifdef USE_INET6
static pfil_return_t
ipf_check_wrapper6(struct mbuf **mp, struct ifnet *ifp, int flags,
    void *ruleset __unused, struct inpcb *inp)
{
        pfil_return_t rv;

        CURVNET_SET(ifp->if_vnet);
        rv = ipf_check(&V_ipfmain, mtod(*mp, struct ip *),
            sizeof(struct ip6_hdr), ifp, !!(flags & PFIL_OUT), mp);
        CURVNET_RESTORE();
        if (rv == 0 && *mp == NULL)
                return (PFIL_CONSUMED);

        return (rv == 0 ? PFIL_PASS : PFIL_DROPPED);
}
# endif
#if     defined(IPFILTER_LKM)
int ipf_identify(char *s)
{
        if (strcmp(s, "ipl") == 0)
                return (1);
        return (0);
}
#endif /* IPFILTER_LKM */


static void
ipf_timer_func(void *arg)
{
        ipf_main_softc_t *softc = arg;
        SPL_INT(s);

        SPL_NET(s);

        if (softc->ipf_running > 0)
                ipf_slowtimer(softc);

        if (softc->ipf_running == -1 || softc->ipf_running == 1) {
                callout_reset(&softc->ipf_slow_ch,
                        (hz / IPF_HZ_DIVIDE) * IPF_HZ_MULT,
                        ipf_timer_func, softc);
        }
        SPL_X(s);
}


int
ipfattach(ipf_main_softc_t *softc)
{
#ifdef USE_SPL
        int s;
#endif

        SPL_NET(s);
        if (softc->ipf_running > 0) {
                SPL_X(s);
                return (EBUSY);
        }

        if (ipf_init_all(softc) < 0) {
                SPL_X(s);
                return (EIO);
        }


        bzero((char *)V_ipfmain.ipf_selwait, sizeof(V_ipfmain.ipf_selwait));
        softc->ipf_running = 1;

        if (softc->ipf_control_forwarding & 1)
                V_ipforwarding = 1;

        SPL_X(s);
        callout_init_rw(&softc->ipf_slow_ch, &softc->ipf_global.ipf_lk, CALLOUT_SHAREDLOCK);
        callout_reset(&softc->ipf_slow_ch, (hz / IPF_HZ_DIVIDE) * IPF_HZ_MULT,
                ipf_timer_func, softc);
        return (0);
}


/*
 * Disable the filter by removing the hooks from the IP input/output
 * stream.
 */
int
ipfdetach(ipf_main_softc_t *softc)
{
#ifdef USE_SPL
        int s;
#endif

        if (softc->ipf_control_forwarding & 2)
                V_ipforwarding = 0;

        SPL_NET(s);

        callout_drain(&softc->ipf_slow_ch);

        ipf_fini_all(softc);

        softc->ipf_running = -2;

        SPL_X(s);

        return (0);
}


/*
 * Filter ioctl interface.
 */
int
ipfioctl(struct cdev *dev, ioctlcmd_t cmd, caddr_t data,
        int mode, struct thread *p)
#define p_cred  td_ucred
#define p_uid   td_ucred->cr_ruid
{
        int error = 0, unit = 0;
        SPL_INT(s);

        CURVNET_SET(TD_TO_VNET(p));
        if (securelevel_ge(p->p_cred, 3) && (mode & FWRITE))
        {
                V_ipfmain.ipf_interror = 130001;
                CURVNET_RESTORE();
                return (EPERM);
        }

        /*
         * Remember, the host system (with its vnet0) controls
         * whether a jail is allowed to use ipfilter or not.
         * The default is ipfilter cannot be used by a jail
         * unless the sysctl allows it.
         */
        if (V0_ipfmain.ipf_jail_allowed == 0) {
                if (jailed(p->p_cred)) {
                        V_ipfmain.ipf_interror = 130019;
                        CURVNET_RESTORE();
                        return (EOPNOTSUPP);
                }
        }

        if (jailed_without_vnet(p->p_cred)) {
                V_ipfmain.ipf_interror = 130018;
                CURVNET_RESTORE();
                return (EOPNOTSUPP);
        }

        unit = GET_MINOR(dev);
        if ((IPL_LOGMAX < unit) || (unit < 0)) {
                V_ipfmain.ipf_interror = 130002;
                CURVNET_RESTORE();
                return (ENXIO);
        }

        if (V_ipfmain.ipf_running <= 0) {
                if (unit != IPL_LOGIPF && cmd != SIOCIPFINTERROR) {
                        V_ipfmain.ipf_interror = 130003;
                        CURVNET_RESTORE();
                        return (EIO);
                }
                if (cmd != SIOCIPFGETNEXT && cmd != SIOCIPFGET &&
                    cmd != SIOCIPFSET && cmd != SIOCFRENB &&
                    cmd != SIOCGETFS && cmd != SIOCGETFF &&
                    cmd != SIOCIPFINTERROR) {
                        V_ipfmain.ipf_interror = 130004;
                        CURVNET_RESTORE();
                        return (EIO);
                }
        }

        SPL_NET(s);

        error = ipf_ioctlswitch(&V_ipfmain, unit, data, cmd, mode, p->p_uid, p);
        CURVNET_RESTORE();
        if (error != -1) {
                SPL_X(s);
                return (error);
        }

        SPL_X(s);

        return (error);
}


/*
 * ipf_send_reset - this could conceivably be a call to tcp_respond(), but that
 * requires a large amount of setting up and isn't any more efficient.
 */
int
ipf_send_reset(fr_info_t *fin)
{
        struct tcphdr *tcp, *tcp2;
        int tlen = 0, hlen;
        struct mbuf *m;
#ifdef USE_INET6
        ip6_t *ip6;
#endif
        ip_t *ip;

        tcp = fin->fin_dp;
        if (tcp_get_flags(tcp) & TH_RST)
                return (-1);            /* feedback loop */

        if (ipf_checkl4sum(fin) == -1)
                return (-1);

        tlen = fin->fin_dlen - (TCP_OFF(tcp) << 2) +
                        ((tcp_get_flags(tcp) & TH_SYN) ? 1 : 0) +
                        ((tcp_get_flags(tcp) & TH_FIN) ? 1 : 0);

#ifdef USE_INET6
        hlen = (fin->fin_v == 6) ? sizeof(ip6_t) : sizeof(ip_t);
#else
        hlen = sizeof(ip_t);
#endif
#ifdef MGETHDR
        MGETHDR(m, M_NOWAIT, MT_HEADER);
#else
        MGET(m, M_NOWAIT, MT_HEADER);
#endif
        if (m == NULL)
                return (-1);
        if (sizeof(*tcp2) + hlen > MLEN) {
                if (!(MCLGET(m, M_NOWAIT))) {
                        FREE_MB_T(m);
                        return (-1);
                }
        }

        m->m_len = sizeof(*tcp2) + hlen;
        m->m_data += max_linkhdr;
        m->m_pkthdr.len = m->m_len;
        m->m_pkthdr.rcvif = (struct ifnet *)0;
        ip = mtod(m, struct ip *);
        bzero((char *)ip, hlen);
#ifdef USE_INET6
        ip6 = (ip6_t *)ip;
#endif
        tcp2 = (struct tcphdr *)((char *)ip + hlen);
        tcp2->th_sport = tcp->th_dport;
        tcp2->th_dport = tcp->th_sport;

        if (tcp_get_flags(tcp) & TH_ACK) {
                tcp2->th_seq = tcp->th_ack;
                tcp_set_flags(tcp2, TH_RST);
                tcp2->th_ack = 0;
        } else {
                tcp2->th_seq = 0;
                tcp2->th_ack = ntohl(tcp->th_seq);
                tcp2->th_ack += tlen;
                tcp2->th_ack = htonl(tcp2->th_ack);
                tcp_set_flags(tcp2, TH_RST|TH_ACK);
        }
        TCP_OFF_A(tcp2, sizeof(*tcp2) >> 2);
        tcp2->th_win = tcp->th_win;
        tcp2->th_sum = 0;
        tcp2->th_urp = 0;

#ifdef USE_INET6
        if (fin->fin_v == 6) {
                ip6->ip6_flow = ((ip6_t *)fin->fin_ip)->ip6_flow;
                ip6->ip6_plen = htons(sizeof(struct tcphdr));
                ip6->ip6_nxt = IPPROTO_TCP;
                ip6->ip6_hlim = 0;
                ip6->ip6_src = fin->fin_dst6.in6;
                ip6->ip6_dst = fin->fin_src6.in6;
                tcp2->th_sum = in6_cksum(m, IPPROTO_TCP,
                                         sizeof(*ip6), sizeof(*tcp2));
                return (ipf_send_ip(fin, m));
        }
#endif
        ip->ip_p = IPPROTO_TCP;
        ip->ip_len = htons(sizeof(struct tcphdr));
        ip->ip_src.s_addr = fin->fin_daddr;
        ip->ip_dst.s_addr = fin->fin_saddr;
        tcp2->th_sum = in_cksum(m, hlen + sizeof(*tcp2));
        ip->ip_len = htons(hlen + sizeof(*tcp2));
        return (ipf_send_ip(fin, m));
}


/*
 * ip_len must be in network byte order when called.
 */
static int
ipf_send_ip(fr_info_t *fin, mb_t *m)
{
        fr_info_t fnew;
        ip_t *ip, *oip;
        int hlen;

        ip = mtod(m, ip_t *);
        bzero((char *)&fnew, sizeof(fnew));
        fnew.fin_main_soft = fin->fin_main_soft;

        IP_V_A(ip, fin->fin_v);
        switch (fin->fin_v)
        {
        case 4 :
                oip = fin->fin_ip;
                hlen = sizeof(*oip);
                fnew.fin_v = 4;
                fnew.fin_p = ip->ip_p;
                fnew.fin_plen = ntohs(ip->ip_len);
                IP_HL_A(ip, sizeof(*oip) >> 2);
                ip->ip_tos = oip->ip_tos;
                ip->ip_id = fin->fin_ip->ip_id;
                ip->ip_off = htons(V_path_mtu_discovery ? IP_DF : 0);
                ip->ip_ttl = V_ip_defttl;
                ip->ip_sum = 0;
                break;
#ifdef USE_INET6
        case 6 :
        {
                ip6_t *ip6 = (ip6_t *)ip;

                ip6->ip6_vfc = 0x60;
                ip6->ip6_hlim = IPDEFTTL;

                hlen = sizeof(*ip6);
                fnew.fin_p = ip6->ip6_nxt;
                fnew.fin_v = 6;
                fnew.fin_plen = ntohs(ip6->ip6_plen) + hlen;
                break;
        }
#endif
        default :
                return (EINVAL);
        }
#ifdef IPSEC_SUPPORT
        m->m_pkthdr.rcvif = NULL;
#endif

        fnew.fin_ifp = fin->fin_ifp;
        fnew.fin_flx = FI_NOCKSUM;
        fnew.fin_m = m;
        fnew.fin_ip = ip;
        fnew.fin_mp = &m;
        fnew.fin_hlen = hlen;
        fnew.fin_dp = (char *)ip + hlen;
        (void) ipf_makefrip(hlen, ip, &fnew);

        return (ipf_fastroute(m, &m, &fnew, NULL));
}


int
ipf_send_icmp_err(int type, fr_info_t *fin, int dst)
{
        int err, hlen, xtra, iclen, ohlen, avail;
        struct in_addr dst4;
        struct icmp *icmp;
        struct mbuf *m;
        i6addr_t dst6;
        void *ifp;
#ifdef USE_INET6
        int code;
        ip6_t *ip6;
#endif
        ip_t *ip, *ip2;

        if ((type < 0) || (type >= ICMP_MAXTYPE))
                return (-1);

#ifdef USE_INET6
        code = fin->fin_icode;
        /* See NetBSD ip_fil_netbsd.c r1.4: */
        if ((code < 0) || (code >= sizeof(icmptoicmp6unreach)/sizeof(int)))
                return (-1);
#endif

        if (ipf_checkl4sum(fin) == -1)
                return (-1);
#ifdef MGETHDR
        MGETHDR(m, M_NOWAIT, MT_HEADER);
#else
        MGET(m, M_NOWAIT, MT_HEADER);
#endif
        if (m == NULL)
                return (-1);
        avail = MHLEN;

        xtra = 0;
        hlen = 0;
        ohlen = 0;
        dst4.s_addr = 0;
        ifp = fin->fin_ifp;
        if (fin->fin_v == 4) {
                if ((fin->fin_p == IPPROTO_ICMP) && !(fin->fin_flx & FI_SHORT))
                        switch (ntohs(fin->fin_data[0]) >> 8)
                        {
                        case ICMP_ECHO :
                        case ICMP_TSTAMP :
                        case ICMP_IREQ :
                        case ICMP_MASKREQ :
                                break;
                        default :
                                FREE_MB_T(m);
                                return (0);
                        }

                if (dst == 0) {
                        if (ipf_ifpaddr(&V_ipfmain, 4, FRI_NORMAL, ifp,
                                        &dst6, NULL) == -1) {
                                FREE_MB_T(m);
                                return (-1);
                        }
                        dst4 = dst6.in4;
                } else
                        dst4.s_addr = fin->fin_daddr;

                hlen = sizeof(ip_t);
                ohlen = fin->fin_hlen;
                iclen = hlen + offsetof(struct icmp, icmp_ip) + ohlen;
                if (fin->fin_hlen < fin->fin_plen)
                        xtra = MIN(fin->fin_dlen, 8);
                else
                        xtra = 0;
        }

#ifdef USE_INET6
        else if (fin->fin_v == 6) {
                hlen = sizeof(ip6_t);
                ohlen = sizeof(ip6_t);
                iclen = hlen + offsetof(struct icmp, icmp_ip) + ohlen;
                type = icmptoicmp6types[type];
                if (type == ICMP6_DST_UNREACH)
                        code = icmptoicmp6unreach[code];

                if (iclen + max_linkhdr + fin->fin_plen > avail) {
                        if (!(MCLGET(m, M_NOWAIT))) {
                                FREE_MB_T(m);
                                return (-1);
                        }
                        avail = MCLBYTES;
                }
                xtra = MIN(fin->fin_plen, avail - iclen - max_linkhdr);
                xtra = MIN(xtra, IPV6_MMTU - iclen);
                if (dst == 0) {
                        if (ipf_ifpaddr(&V_ipfmain, 6, FRI_NORMAL, ifp,
                                        &dst6, NULL) == -1) {
                                FREE_MB_T(m);
                                return (-1);
                        }
                } else
                        dst6 = fin->fin_dst6;
        }
#endif
        else {
                FREE_MB_T(m);
                return (-1);
        }

        avail -= (max_linkhdr + iclen);
        if (avail < 0) {
                FREE_MB_T(m);
                return (-1);
        }
        if (xtra > avail)
                xtra = avail;
        iclen += xtra;
        m->m_data += max_linkhdr;
        m->m_pkthdr.rcvif = (struct ifnet *)0;
        m->m_pkthdr.len = iclen;
        m->m_len = iclen;
        ip = mtod(m, ip_t *);
        icmp = (struct icmp *)((char *)ip + hlen);
        ip2 = (ip_t *)&icmp->icmp_ip;

        icmp->icmp_type = type;
        icmp->icmp_code = fin->fin_icode;
        icmp->icmp_cksum = 0;
#ifdef icmp_nextmtu
        if (type == ICMP_UNREACH && fin->fin_icode == ICMP_UNREACH_NEEDFRAG) {
                if (fin->fin_mtu != 0) {
                        icmp->icmp_nextmtu = htons(fin->fin_mtu);

                } else if (ifp != NULL) {
                        icmp->icmp_nextmtu = htons(GETIFMTU_4(ifp));

                } else {        /* make up a number... */
                        icmp->icmp_nextmtu = htons(fin->fin_plen - 20);
                }
        }
#endif

        bcopy((char *)fin->fin_ip, (char *)ip2, ohlen);

#ifdef USE_INET6
        ip6 = (ip6_t *)ip;
        if (fin->fin_v == 6) {
                ip6->ip6_flow = ((ip6_t *)fin->fin_ip)->ip6_flow;
                ip6->ip6_plen = htons(iclen - hlen);
                ip6->ip6_nxt = IPPROTO_ICMPV6;
                ip6->ip6_hlim = 0;
                ip6->ip6_src = dst6.in6;
                ip6->ip6_dst = fin->fin_src6.in6;
                if (xtra > 0)
                        bcopy((char *)fin->fin_ip + ohlen,
                              (char *)&icmp->icmp_ip + ohlen, xtra);
                icmp->icmp_cksum = in6_cksum(m, IPPROTO_ICMPV6,
                                             sizeof(*ip6), iclen - hlen);
        } else
#endif
        {
                ip->ip_p = IPPROTO_ICMP;
                ip->ip_src.s_addr = dst4.s_addr;
                ip->ip_dst.s_addr = fin->fin_saddr;

                if (xtra > 0)
                        bcopy((char *)fin->fin_ip + ohlen,
                              (char *)&icmp->icmp_ip + ohlen, xtra);
                icmp->icmp_cksum = ipf_cksum((u_short *)icmp,
                                             sizeof(*icmp) + 8);
                ip->ip_len = htons(iclen);
                ip->ip_p = IPPROTO_ICMP;
        }
        err = ipf_send_ip(fin, m);
        return (err);
}




/*
 * m0 - pointer to mbuf where the IP packet starts
 * mpp - pointer to the mbuf pointer that is the start of the mbuf chain
 */
int
ipf_fastroute(mb_t *m0, mb_t **mpp, fr_info_t *fin, frdest_t *fdp)
{
        register struct ip *ip, *mhip;
        register struct mbuf *m = *mpp;
        int len, off, error = 0, hlen, code;
        struct ifnet *ifp, *sifp;
        struct route ro;
        struct sockaddr_in *dst;
        const struct sockaddr *gw;
        struct nhop_object *nh;
        u_long fibnum = 0;
        u_short ip_off;
        frdest_t node;
        frentry_t *fr;

#ifdef M_WRITABLE
        /*
        * HOT FIX/KLUDGE:
        *
        * If the mbuf we're about to send is not writable (because of
        * a cluster reference, for example) we'll need to make a copy
        * of it since this routine modifies the contents.
        *
        * If you have non-crappy network hardware that can transmit data
        * from the mbuf, rather than making a copy, this is gonna be a
        * problem.
        */
        if (M_WRITABLE(m) == 0) {
                m0 = m_dup(m, M_NOWAIT);
                if (m0 != NULL) {
                        FREE_MB_T(m);
                        m = m0;
                        *mpp = m;
                } else {
                        error = ENOBUFS;
                        FREE_MB_T(m);
                        goto done;
                }
        }
#endif

#ifdef USE_INET6
        if (fin->fin_v == 6) {
                /*
                 * currently "to <if>" and "to <if>:ip#" are not supported
                 * for IPv6
                 */
                return (ip6_output(m, NULL, NULL, 0, NULL, NULL, NULL));
        }
#endif

        hlen = fin->fin_hlen;
        ip = mtod(m0, struct ip *);
        ifp = NULL;

        /*
         * Route packet.
         */
        bzero(&ro, sizeof (ro));
        dst = (struct sockaddr_in *)&ro.ro_dst;
        dst->sin_family = AF_INET;
        dst->sin_addr = ip->ip_dst;
        dst->sin_len = sizeof(dst);
        gw = (const struct sockaddr *)dst;

        fr = fin->fin_fr;
        if ((fr != NULL) && !(fr->fr_flags & FR_KEEPSTATE) && (fdp != NULL) &&
            (fdp->fd_type == FRD_DSTLIST)) {
                if (ipf_dstlist_select_node(fin, fdp->fd_ptr, NULL, &node) == 0)
                        fdp = &node;
        }

        if (fdp != NULL)
                ifp = fdp->fd_ptr;
        else
                ifp = fin->fin_ifp;

        if ((ifp == NULL) && ((fr == NULL) || !(fr->fr_flags & FR_FASTROUTE))) {
                error = -2;
                goto bad;
        }

        if ((fdp != NULL) && (fdp->fd_ip.s_addr != 0))
                dst->sin_addr = fdp->fd_ip;

        fibnum = M_GETFIB(m0);
        NET_EPOCH_ASSERT();
        nh = fib4_lookup(fibnum, dst->sin_addr, 0, NHR_NONE, 0);
        if (nh == NULL) {
                if (in_localaddr(ip->ip_dst))
                        error = EHOSTUNREACH;
                else
                        error = ENETUNREACH;
                goto bad;
        }

        if (ifp == NULL)
                ifp = nh->nh_ifp;
        if (nh->nh_flags & NHF_GATEWAY) {
                gw = &nh->gw_sa;
                ro.ro_flags |= RT_HAS_GW;
        }

        /*
         * For input packets which are being "fastrouted", they won't
         * go back through output filtering and miss their chance to get
         * NAT'd and counted.  Duplicated packets aren't considered to be
         * part of the normal packet stream, so do not NAT them or pass
         * them through stateful checking, etc.
         */
        if ((fdp != &fr->fr_dif) && (fin->fin_out == 0)) {
                sifp = fin->fin_ifp;
                fin->fin_ifp = ifp;
                fin->fin_out = 1;
                (void) ipf_acctpkt(fin, NULL);
                fin->fin_fr = NULL;
                if (!fr || !(fr->fr_flags & FR_RETMASK)) {
                        u_32_t pass;

                        (void) ipf_state_check(fin, &pass);
                }

                switch (ipf_nat_checkout(fin, NULL))
                {
                case 0 :
                        break;
                case 1 :
                        ip->ip_sum = 0;
                        break;
                case -1 :
                        error = -1;
                        goto bad;
                        break;
                }

                fin->fin_ifp = sifp;
                fin->fin_out = 0;
        } else
                ip->ip_sum = 0;
        /*
         * If small enough for interface, can just send directly.
         */
        if (ntohs(ip->ip_len) <= ifp->if_mtu) {
                if (!ip->ip_sum)
                        ip->ip_sum = in_cksum(m, hlen);
                error = (*ifp->if_output)(ifp, m, gw, &ro);
                goto done;
        }
        /*
         * Too large for interface; fragment if possible.
         * Must be able to put at least 8 bytes per fragment.
         */
        ip_off = ntohs(ip->ip_off);
        if (ip_off & IP_DF) {
                error = EMSGSIZE;
                goto bad;
        }
        len = (ifp->if_mtu - hlen) &~ 7;
        if (len < 8) {
                error = EMSGSIZE;
                goto bad;
        }

    {
        int mhlen, firstlen = len;
        struct mbuf **mnext = &m->m_act;

        /*
         * Loop through length of segment after first fragment,
         * make new header and copy data of each part and link onto chain.
         */
        m0 = m;
        mhlen = sizeof (struct ip);
        for (off = hlen + len; off < ntohs(ip->ip_len); off += len) {
#ifdef MGETHDR
                MGETHDR(m, M_NOWAIT, MT_HEADER);
#else
                MGET(m, M_NOWAIT, MT_HEADER);
#endif
                if (m == NULL) {
                        m = m0;
                        error = ENOBUFS;
                        goto bad;
                }
                m->m_data += max_linkhdr;
                mhip = mtod(m, struct ip *);
                bcopy((char *)ip, (char *)mhip, sizeof(*ip));
                if (hlen > sizeof (struct ip)) {
                        mhlen = ip_optcopy(ip, mhip) + sizeof (struct ip);
                        IP_HL_A(mhip, mhlen >> 2);
                }
                m->m_len = mhlen;
                mhip->ip_off = ((off - hlen) >> 3) + ip_off;
                if (off + len >= ntohs(ip->ip_len))
                        len = ntohs(ip->ip_len) - off;
                else
                        mhip->ip_off |= IP_MF;
                mhip->ip_len = htons((u_short)(len + mhlen));
                *mnext = m;
                m->m_next = m_copym(m0, off, len, M_NOWAIT);
                if (m->m_next == 0) {
                        error = ENOBUFS;        /* ??? */
                        goto sendorfree;
                }
                m->m_pkthdr.len = mhlen + len;
                m->m_pkthdr.rcvif = NULL;
                mhip->ip_off = htons((u_short)mhip->ip_off);
                mhip->ip_sum = 0;
                mhip->ip_sum = in_cksum(m, mhlen);
                mnext = &m->m_act;
        }
        /*
         * Update first fragment by trimming what's been copied out
         * and updating header, then send each fragment (in order).
         */
        m_adj(m0, hlen + firstlen - ip->ip_len);
        ip->ip_len = htons((u_short)(hlen + firstlen));
        ip->ip_off = htons((u_short)IP_MF);
        ip->ip_sum = 0;
        ip->ip_sum = in_cksum(m0, hlen);
sendorfree:
        for (m = m0; m; m = m0) {
                m0 = m->m_act;
                m->m_act = 0;
                if (error == 0)
                        error = (*ifp->if_output)(ifp, m, gw, &ro);
                else
                        FREE_MB_T(m);
        }
    }
done:
        if (!error)
                V_ipfmain.ipf_frouteok[0]++;
        else
                V_ipfmain.ipf_frouteok[1]++;

        return (0);
bad:
        if (error == EMSGSIZE) {
                sifp = fin->fin_ifp;
                code = fin->fin_icode;
                fin->fin_icode = ICMP_UNREACH_NEEDFRAG;
                fin->fin_ifp = ifp;
                (void) ipf_send_icmp_err(ICMP_UNREACH, fin, 1);
                fin->fin_ifp = sifp;
                fin->fin_icode = code;
        }
        FREE_MB_T(m);
        goto done;
}


int
ipf_verifysrc(fr_info_t *fin)
{
        struct nhop_object *nh;

        NET_EPOCH_ASSERT();
        nh = fib4_lookup(RT_DEFAULT_FIB, fin->fin_src, 0, NHR_NONE, 0);
        if (nh == NULL)
                return (0);
        return (fin->fin_ifp == nh->nh_ifp);
}


/*
 * return the first IP Address associated with an interface
 */
int
ipf_ifpaddr(ipf_main_softc_t *softc, int v, int atype, void *ifptr,
        i6addr_t *inp, i6addr_t *inpmask)
{
#ifdef USE_INET6
        struct in6_addr *ia6 = NULL;
#endif
        struct sockaddr *sock, *mask;
        struct sockaddr_in *sin;
        struct ifaddr *ifa;
        struct ifnet *ifp;

        if ((ifptr == NULL) || (ifptr == (void *)-1))
                return (-1);

        sin = NULL;
        ifp = ifptr;

        if (v == 4)
                inp->in4.s_addr = 0;
#ifdef USE_INET6
        else if (v == 6)
                bzero((char *)inp, sizeof(*inp));
#endif
        ifa = CK_STAILQ_FIRST(&ifp->if_addrhead);

        sock = ifa->ifa_addr;
        while (sock != NULL && ifa != NULL) {
                sin = (struct sockaddr_in *)sock;
                if ((v == 4) && (sin->sin_family == AF_INET))
                        break;
#ifdef USE_INET6
                if ((v == 6) && (sin->sin_family == AF_INET6)) {
                        ia6 = &((struct sockaddr_in6 *)sin)->sin6_addr;
                        if (!IN6_IS_ADDR_LINKLOCAL(ia6) &&
                            !IN6_IS_ADDR_LOOPBACK(ia6))
                                break;
                }
#endif
                ifa = CK_STAILQ_NEXT(ifa, ifa_link);
                if (ifa != NULL)
                        sock = ifa->ifa_addr;
        }

        if (ifa == NULL || sin == NULL)
                return (-1);

        mask = ifa->ifa_netmask;
        if (atype == FRI_BROADCAST)
                sock = ifa->ifa_broadaddr;
        else if (atype == FRI_PEERADDR)
                sock = ifa->ifa_dstaddr;

        if (sock == NULL)
                return (-1);

#ifdef USE_INET6
        if (v == 6) {
                return (ipf_ifpfillv6addr(atype, (struct sockaddr_in6 *)sock,
                                         (struct sockaddr_in6 *)mask,
                                         inp, inpmask));
        }
#endif
        return (ipf_ifpfillv4addr(atype, (struct sockaddr_in *)sock,
                                 (struct sockaddr_in *)mask,
                                 &inp->in4, &inpmask->in4));
}


u_32_t
ipf_newisn(fr_info_t *fin)
{
        u_32_t newiss;
        newiss = arc4random();
        return (newiss);
}


int
ipf_checkv4sum(fr_info_t *fin)
{
#ifdef CSUM_DATA_VALID
        int manual = 0;
        u_short sum;
        ip_t *ip;
        mb_t *m;

        if ((fin->fin_flx & FI_NOCKSUM) != 0)
                return (0);

        if ((fin->fin_flx & FI_SHORT) != 0)
                return (1);

        if (fin->fin_cksum != FI_CK_NEEDED)
                return (fin->fin_cksum > FI_CK_NEEDED) ? 0 : -1;

        m = fin->fin_m;
        if (m == NULL) {
                manual = 1;
                goto skipauto;
        }
        ip = fin->fin_ip;

        if ((m->m_pkthdr.csum_flags & (CSUM_IP_CHECKED|CSUM_IP_VALID)) ==
            CSUM_IP_CHECKED) {
                fin->fin_cksum = FI_CK_BAD;
                fin->fin_flx |= FI_BAD;
                DT2(ipf_fi_bad_checkv4sum_csum_ip_checked, fr_info_t *, fin, u_int, m->m_pkthdr.csum_flags & (CSUM_IP_CHECKED|CSUM_IP_VALID));
                return (-1);
        }
        if (m->m_pkthdr.csum_flags & CSUM_DATA_VALID) {
                /* Depending on the driver, UDP may have zero checksum */
                if (fin->fin_p == IPPROTO_UDP && (fin->fin_flx &
                    (FI_FRAG|FI_SHORT|FI_BAD)) == 0) {
                        udphdr_t *udp = fin->fin_dp;
                        if (udp->uh_sum == 0) {
                                /*
                                 * we're good no matter what the hardware
                                 * checksum flags and csum_data say (handling
                                 * of csum_data for zero UDP checksum is not
                                 * consistent across all drivers)
                                 */
                                fin->fin_cksum = 1;
                                return (0);
                        }
                }

                if (m->m_pkthdr.csum_flags & CSUM_PSEUDO_HDR)
                        sum = m->m_pkthdr.csum_data;
                else
                        sum = in_pseudo(ip->ip_src.s_addr, ip->ip_dst.s_addr,
                                        htonl(m->m_pkthdr.csum_data +
                                        fin->fin_dlen + fin->fin_p));
                sum ^= 0xffff;
                if (sum != 0) {
                        fin->fin_cksum = FI_CK_BAD;
                        fin->fin_flx |= FI_BAD;
                        DT2(ipf_fi_bad_checkv4sum_sum, fr_info_t *, fin, u_int, sum);
                } else {
                        fin->fin_cksum = FI_CK_SUMOK;
                        return (0);
                }
        } else {
                if (m->m_pkthdr.csum_flags == CSUM_DELAY_DATA) {
                        fin->fin_cksum = FI_CK_L4FULL;
                        return (0);
                } else if (m->m_pkthdr.csum_flags == CSUM_TCP ||
                           m->m_pkthdr.csum_flags == CSUM_UDP ||
                           m->m_pkthdr.csum_flags == CSUM_IP) {
                        fin->fin_cksum = FI_CK_L4PART;
                        return (0);
                } else {
                        manual = 1;
                }
        }
skipauto:
        if (manual != 0) {
                if (ipf_checkl4sum(fin) == -1) {
                        fin->fin_flx |= FI_BAD;
                        DT2(ipf_fi_bad_checkv4sum_manual, fr_info_t *, fin, u_int, manual);
                        return (-1);
                }
        }
#else
        if (ipf_checkl4sum(fin) == -1) {
                fin->fin_flx |= FI_BAD;
                DT2(ipf_fi_bad_checkv4sum_checkl4sum, fr_info_t *, fin, u_int, -1);
                return (-1);
        }
#endif
        return (0);
}


#ifdef USE_INET6
int
ipf_checkv6sum(fr_info_t *fin)
{
        if ((fin->fin_flx & FI_NOCKSUM) != 0) {
                DT(ipf_checkv6sum_fi_nocksum);
                return (0);
        }

        if ((fin->fin_flx & FI_SHORT) != 0) {
                DT(ipf_checkv6sum_fi_short);
                return (1);
        }

        if (fin->fin_cksum != FI_CK_NEEDED) {
                DT(ipf_checkv6sum_fi_ck_needed);
                return (fin->fin_cksum > FI_CK_NEEDED) ? 0 : -1;
        }

        if (ipf_checkl4sum(fin) == -1) {
                fin->fin_flx |= FI_BAD;
                DT2(ipf_fi_bad_checkv6sum_checkl4sum, fr_info_t *, fin, u_int, -1);
                return (-1);
        }
        return (0);
}
#endif /* USE_INET6 */


size_t
mbufchainlen(struct mbuf *m0)
{
        size_t len;

        if ((m0->m_flags & M_PKTHDR) != 0) {
                len = m0->m_pkthdr.len;
        } else {
                struct mbuf *m;

                for (m = m0, len = 0; m != NULL; m = m->m_next)
                        len += m->m_len;
        }
        return (len);
}


/* ------------------------------------------------------------------------ */
/* Function:    ipf_pullup                                                  */
/* Returns:     NULL == pullup failed, else pointer to protocol header      */
/* Parameters:  xmin(I)- pointer to buffer where data packet starts         */
/*              fin(I) - pointer to packet information                      */
/*              len(I) - number of bytes to pullup                          */
/*                                                                          */
/* Attempt to move at least len bytes (from the start of the buffer) into a */
/* single buffer for ease of access.  Operating system native functions are */
/* used to manage buffers - if necessary.  If the entire packet ends up in  */
/* a single buffer, set the FI_COALESCE flag even though ipf_coalesce() has */
/* not been called.  Both fin_ip and fin_dp are updated before exiting _IF_ */
/* and ONLY if the pullup succeeds.                                         */
/*                                                                          */
/* We assume that 'xmin' is a pointer to a buffer that is part of the chain */
/* of buffers that starts at *fin->fin_mp.                                  */
/* ------------------------------------------------------------------------ */
ip_t *
ipf_pullup(mb_t *xmin, fr_info_t *fin, int len)
{
        int dpoff, ipoff;
        mb_t *m = xmin;
        ip_t *ip;

        if (m == NULL)
                return (NULL);

        ip = fin->fin_ip;
        if ((fin->fin_flx & FI_COALESCE) != 0)
                return (ip);

        ipoff = fin->fin_ipoff;
        if (fin->fin_dp != NULL)
                dpoff = (char *)fin->fin_dp - (char *)ip;
        else
                dpoff = 0;

        if (M_LEN(m) < len) {
                mb_t *n = *fin->fin_mp;
                /*
                 * Assume that M_PKTHDR is set and just work with what is left
                 * rather than check..
                 * Should not make any real difference, anyway.
                 */
                if (m != n) {
                        /*
                         * Record the mbuf that points to the mbuf that we're
                         * about to go to work on so that we can update the
                         * m_next appropriately later.
                         */
                        for (; n->m_next != m; n = n->m_next)
                                ;
                } else {
                        n = NULL;
                }

#ifdef MHLEN
                if (len > MHLEN)
#else
                if (len > MLEN)
#endif
                {
#ifdef HAVE_M_PULLDOWN
                        if (m_pulldown(m, 0, len, NULL) == NULL)
                                m = NULL;
#else
                        FREE_MB_T(*fin->fin_mp);
                        m = NULL;
                        n = NULL;
#endif
                } else
                {

                        m = m_pullup(m, len);
                }
                if (n != NULL)
                        n->m_next = m;
                if (m == NULL) {
                        /*
                         * When n is non-NULL, it indicates that m pointed to
                         * a sub-chain (tail) of the mbuf and that the head
                         * of this chain has not yet been free'd.
                         */
                        if (n != NULL) {
                                FREE_MB_T(*fin->fin_mp);
                        }

                        *fin->fin_mp = NULL;
                        fin->fin_m = NULL;
                        return (NULL);
                }

                if (n == NULL)
                        *fin->fin_mp = m;

                while (M_LEN(m) == 0) {
                        m = m->m_next;
                }
                fin->fin_m = m;
                ip = MTOD(m, ip_t *) + ipoff;

                fin->fin_ip = ip;
                if (fin->fin_dp != NULL)
                        fin->fin_dp = (char *)fin->fin_ip + dpoff;
                if (fin->fin_fraghdr != NULL)
                        fin->fin_fraghdr = (char *)ip +
                                           ((char *)fin->fin_fraghdr -
                                            (char *)fin->fin_ip);
        }

        if (len == fin->fin_plen)
                fin->fin_flx |= FI_COALESCE;
        return (ip);
}


int
ipf_inject(fr_info_t *fin, mb_t *m)
{
        struct epoch_tracker et;
        int error = 0;

        NET_EPOCH_ENTER(et);
        if (fin->fin_out == 0) {
                netisr_dispatch(NETISR_IP, m);
        } else {
                fin->fin_ip->ip_len = ntohs(fin->fin_ip->ip_len);
                fin->fin_ip->ip_off = ntohs(fin->fin_ip->ip_off);
                error = ip_output(m, NULL, NULL, IP_FORWARDING, NULL, NULL);
        }
        NET_EPOCH_EXIT(et);

        return (error);
}

VNET_DEFINE_STATIC(pfil_hook_t, ipf_inet_hook);
VNET_DEFINE_STATIC(pfil_hook_t, ipf_inet6_hook);
#define V_ipf_inet_hook         VNET(ipf_inet_hook)
#define V_ipf_inet6_hook        VNET(ipf_inet6_hook)

int ipf_pfil_unhook(void) {

        pfil_remove_hook(V_ipf_inet_hook);

#ifdef USE_INET6
        pfil_remove_hook(V_ipf_inet6_hook);
#endif

        return (0);
}

int ipf_pfil_hook(void) {
        int error, error6;

        struct pfil_hook_args pha = {
                .pa_version = PFIL_VERSION,
                .pa_flags = PFIL_IN | PFIL_OUT,
                .pa_modname = "ipfilter",
                .pa_rulname = "default-ip4",
                .pa_mbuf_chk = ipf_check_wrapper,
                .pa_type = PFIL_TYPE_IP4,
        };
        V_ipf_inet_hook = pfil_add_hook(&pha);

#ifdef USE_INET6
        pha.pa_rulname = "default-ip6";
        pha.pa_mbuf_chk = ipf_check_wrapper6;
        pha.pa_type = PFIL_TYPE_IP6;
        V_ipf_inet6_hook = pfil_add_hook(&pha);
#endif

        struct pfil_link_args pla = {
                .pa_version = PFIL_VERSION,
                .pa_flags = PFIL_IN | PFIL_OUT | PFIL_HEADPTR | PFIL_HOOKPTR,
                .pa_head = V_inet_pfil_head,
                .pa_hook = V_ipf_inet_hook,
        };
        error = pfil_link(&pla);

        error6 = 0;
#ifdef USE_INET6
        pla.pa_head = V_inet6_pfil_head;
        pla.pa_hook = V_ipf_inet6_hook;
        error6 = pfil_link(&pla);
#endif

        if (error || error6)
                error = ENODEV;
        else
                error = 0;

        return (error);
}

void
ipf_event_reg(void)
{
        V_ipf_arrivetag = EVENTHANDLER_REGISTER(ifnet_arrival_event, \
                                               ipf_ifevent, NULL, \
                                               EVENTHANDLER_PRI_ANY);
        V_ipf_departtag = EVENTHANDLER_REGISTER(ifnet_departure_event, \
                                               ipf_ifevent, NULL, \
                                               EVENTHANDLER_PRI_ANY);
        V_ipf_renametag = EVENTHANDLER_REGISTER(ifnet_rename_event, \
                                               ipf_ifevent, NULL, \
                                               EVENTHANDLER_PRI_ANY);
}

void
ipf_event_dereg(void)
{
        if (V_ipf_arrivetag != NULL) {
                EVENTHANDLER_DEREGISTER(ifnet_arrival_event, V_ipf_arrivetag);
        }
        if (V_ipf_departtag != NULL) {
                EVENTHANDLER_DEREGISTER(ifnet_departure_event, V_ipf_departtag);
        }
        if (V_ipf_renametag != NULL) {
                EVENTHANDLER_DEREGISTER(ifnet_rename_event, V_ipf_renametag);
        }
}


u_32_t
ipf_random(void)
{
        return (arc4random());
}


u_int
ipf_pcksum(fr_info_t *fin, int hlen, u_int sum)
{
        struct mbuf *m;
        u_int sum2;
        int off;

        m = fin->fin_m;
        off = (char *)fin->fin_dp - (char *)fin->fin_ip;
        m->m_data += hlen;
        m->m_len -= hlen;
        sum2 = in_cksum(fin->fin_m, fin->fin_plen - off);
        m->m_len += hlen;
        m->m_data -= hlen;

        /*
         * Both sum and sum2 are partial sums, so combine them together.
         */
        sum += ~sum2 & 0xffff;
        while (sum > 0xffff)
                sum = (sum & 0xffff) + (sum >> 16);
        sum2 = ~sum & 0xffff;
        return (sum2);
}

#ifdef  USE_INET6
u_int
ipf_pcksum6(struct mbuf *m, ip6_t *ip6, u_int32_t off, u_int32_t len)
{
#ifdef  _KERNEL
        int sum;

        if (m->m_len < sizeof(struct ip6_hdr)) {
                return (0xffff);
        }

        sum = in6_cksum(m, ip6->ip6_nxt, off, len);
        return (sum);
#else
        u_short *sp;
        u_int sum;

        sp = (u_short *)&ip6->ip6_src;
        sum = *sp++;   /* ip6_src */
        sum += *sp++;
        sum += *sp++;
        sum += *sp++;
        sum += *sp++;
        sum += *sp++;
        sum += *sp++;
        sum += *sp++;
        sum += *sp++;   /* ip6_dst */
        sum += *sp++;
        sum += *sp++;
        sum += *sp++;
        sum += *sp++;
        sum += *sp++;
        sum += *sp++;
        sum += *sp++;
        return (ipf_pcksum(fin, off, sum));
#endif
}
#endif

void
ipf_fbsd_kenv_get(ipf_main_softc_t *softc)
{
        TUNABLE_INT_FETCH("net.inet.ipf.large_nat",
                &softc->ipf_large_nat);
        TUNABLE_INT_FETCH("net.inet.ipf.jail_allowed",
                &softc->ipf_jail_allowed);
}