
/*
 * 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);
#define	V_ipf_arrivetag		VNET(ipf_arrivetag)
#define	V_ipf_departtag		VNET(ipf_departtag)

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);
}

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);
	}
}


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);
}
