ip_fil_sunos4.c

/*
 * Copyright (C) 2011 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
#include <sys/param.h>
#include <sys/errno.h>
#include <sys/types.h>
#include <sys/file.h>
#include <sys/ioctl.h>
#include <sys/time.h>
#include <sys/systm.h>
#include <sys/dir.h>
#include <sys/mbuf.h>
#include <sys/protosw.h>
#include <sys/socket.h>

#include <net/if.h>
#include <net/af.h>
#include <net/route.h>
#include <netinet/in.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_timer.h>
#include <netinet/udp.h>
#include <netinet/tcpip.h>
#include <netinet/ip_icmp.h>
#include "netinet/ip_compat.h"
#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"
#ifdef	IPFILTER_SCAN
#include "netinet/ip_scan.h"
#endif
#include "netinet/ip_pool.h"
#include "md5.h"
#include <sys/kernel.h>
extern	int	ip_optcopy __P((struct ip *, struct ip *));

#if !defined(lint)
static const char sccsid[] = "@(#)ip_fil.c	2.41 6/5/96 (C) 1993-2000 Darren Reed";
static const char rcsid[] = "@(#)$Id$";
#endif

extern	struct	protosw	inetsw[];
extern	int	ip_forwarding;

static	u_short	ipid = 0;
static	int	(*ipf_savep) __P((ip_t *, int, void *, int, struct mbuf **));
static	int	ipf_send_ip __P((fr_info_t *, mb_t *));


#if defined(IPFILTER_LKM)
int
iplidentify(s)
	char *s;
{
	if (strcmp(s, "ipl") == 0)
		return 1;
	return 0;
}
#endif /* IPFILTER_LKM */


int
ipfattach()
{
	int s;

	SPL_NET(s);
	if ((ipf_running > 0) || (ipf_checkp == ipf_check)) {
		printf("IP Filter: already initialized\n");
		SPL_X(s);
		return EBUSY;
	}

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

	bzero((char *)ipfcache, sizeof(ipfcache));
	ipf_savep = ipf_checkp;
	ipf_checkp = ipf_check;

	if (ipf_control_forwarding & 1)
		ip_forwarding = 1;

	ipid = 0;

	SPL_X(s);
	timeout(ipf_slowtimer, &ipfmain, (hz / IPF_HZ_DIVIDE) * IPF_HZ_MULT);
	return 0;
}


static void
ipf_timer_func(ptr)
	void *ptr;
{
	ipf_main_softc_t *softc = ptr;
	int s;

	SPL_NET(s);

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

	if (softc->ipf_running == -1 || softc->ipf_running == 1)
		timeout(ipf_timer_func, &ipfmain,
			(hz / IPF_HZ_DIVIDE) * IPF_HZ_MULT);

	SPL_X(s);
}


/*
 * Disable the filter by removing the hooks from the IP input/output
 * stream.
 */
int
ipfdetach()
{
	int s;

	SPL_NET(s);

	untimeout(ipf_slowtimer, &ipfmain);

	if (ipf_control_forwarding & 2)
		ip_forwarding = 0;

	ipf_deinitialise();

	if (ipf_savep != NULL)
		ipf_checkp = ipf_savep;
	ipf_savep = NULL;

	(void) ipf_flush(IPL_LOGIPF, FR_INQUE|FR_OUTQUE|FR_INACTIVE);
	(void) ipf_flush(IPL_LOGIPF, FR_INQUE|FR_OUTQUE);

	SPL_X(s);

	return 0;
}


/*
 * Filter ioctl interface.
 */
int
ipfioctl(dev, cmd, data, mode)
	dev_t dev;
	int cmd;
	caddr_t data;
	int mode;
{
	int error = 0, unit = 0;
	SPL_INT(s);

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

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

	SPL_NET(s);

	error = ipf_ioctlswitch(unit, data, cmd, mode, curproc->p_uid, curproc);
	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(fin)
	fr_info_t *fin;
{
	struct tcphdr *tcp, *tcp2;
	int tlen = 0, hlen;
	struct mbuf *m;
	ip_t *ip;

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

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

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

	MGET(m, M_DONTWAIT, MT_HEADER);
	if (m == NULL)
		return -1;

	hlen = sizeof(ip_t);
	m->m_len = sizeof(*tcp2) + hlen;
	ip = mtod(m, struct ip *);
	bzero((char *)ip, hlen);

	tcp2 = (struct tcphdr *)((char *)ip + hlen);
	tcp2->th_sport = tcp->th_dport;
	tcp2->th_dport = tcp->th_sport;

	if (tcp->th_flags & TH_ACK) {
		tcp2->th_seq = tcp->th_ack;
		tcp2->th_flags = 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);
		tcp2->th_flags = TH_RST|TH_ACK;
	}
	tcp2->th_off = sizeof(*tcp2) >> 2;;
	tcp2->th_x2 = 0;
	tcp2->th_win = tcp->th_win;
	tcp2->th_sum = 0;
	tcp2->th_urp = 0;

	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 = hlen + sizeof(*tcp2);
	return ipf_send_ip(fin, m);
}


static int
ipf_send_ip(fin, m)
	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 :
		hlen = sizeof(*oip);
		oip = fin->fin_ip;
		fnew.fin_v = 4;
		fnew.fin_p = ip->ip_p;
		fnew.fin_plen = ntohs(ip->ip_len) + hlen;
		IP_HL_A(ip, sizeof(*oip) >> 2);
		ip->ip_tos = oip->ip_tos;
		ip->ip_id = fin->fin_ip->ip_id;
		ip->ip_off = 0;
		ip->ip_ttl = tcp_ttl;
		ip->ip_sum = 0;
		break;
	default :
		return EINVAL;
	}

	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(type, fin, dst)
	int type;
	fr_info_t *fin;
	int dst;
{
	int err, hlen = 0, xtra = 0, iclen, ohlen = 0, avail, code;
	struct in_addr dst4;
	struct icmp *icmp;
	struct mbuf *m;
	i6addr_t dst6;
	void *ifp;
	ip_t *ip, *ip2;

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

	if (ipf_checkl4sum(fin) == -1)
		return -1;
	MGET(m, M_DONTWAIT, MT_HEADER);
	if (m == NULL)
		return -1;
	avail = MLEN;

	code = fin->fin_icode;

	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(&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;
		if (fin->fin_hlen < fin->fin_plen)
			xtra = MIN(fin->fin_dlen, 8);
		else
			xtra = 0;
	} else {
		FREE_MB_T(m);
		return -1;
	}

	iclen = hlen + sizeof(*icmp) + xtra;
	avail -= (m->m_off + iclen);
	if (xtra > avail)
		xtra = avail;
	iclen += xtra;
	if (avail < 0) {
		FREE_MB_T(m);
		return -1;
	}
	m->m_len = iclen;
	ip = mtod(m, ip_t *);
	icmp = (struct icmp *)((char *)ip + hlen);
	ip2 = (ip_t *)&icmp->icmp_ip;
	bzero((char *)ip, iclen);

	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);

	ip2->ip_len = htons(ip2->ip_len);
	ip2->ip_off = htons(ip2->ip_off);

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


#if !defined(IPFILTER_LKM)
int iplinit __P((void));

int
iplinit()
{
	if (ipfattach() != 0)
		printf("IP Filter failed to attach\n");
	ip_init();
}
#endif


size_t
mbufchainlen(m0)
	register struct mbuf *m0;
{
	register size_t len = 0;

	for (; m0; m0 = m0->m_next)
		len += m0->m_len;
	return len;
}


/*
 * 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(m0, mpp, fin, fdp)
	struct mbuf *m0, **mpp;
	fr_info_t *fin;
	frdest_t *fdp;
{
	register struct ip *ip, *mhip;
	register struct mbuf *m = *mpp;
	register struct route *ro;
	int len, off, error = 0, hlen, code;
	struct ifnet *ifp, *sifp;
	struct sockaddr_in *dst;
	struct route iproute;
	u_short ip_off;
	frdest_t node;
	frentry_t *fr;

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

	/*
	 * Route packet.
	 */
	ro = &iproute;
	bzero((caddr_t)ro, sizeof (*ro));
	dst = (struct sockaddr_in *)&ro->ro_dst;
	dst->sin_family = AF_INET;
	dst->sin_addr = ip->ip_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 ((fdp != NULL) && (fdp->fd_ip.s_addr != 0))
		dst->sin_addr = fdp->fd_ip;

	rtalloc(ro);
	if (ifp == NULL) {
		if (!fr || !(fr->fr_flags & FR_FASTROUTE)) {
			error = -2;
			goto bad;
		}
		if (ro->ro_rt == 0 || (ifp = ro->ro_rt->rt_ifp) == 0) {
			if (in_localaddr(ip->ip_dst))
				error = EHOSTUNREACH;
			else
				error = ENETUNREACH;
			goto bad;
		}
		if (ro->ro_rt->rt_flags & RTF_GATEWAY)
			dst = (struct sockaddr_in *)&ro->ro_rt->rt_gateway;
	}
	if (ro->ro_rt != NULL)
		ro->ro_rt->rt_use++;

	/*
	 * 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 :
			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 (ip->ip_len <= ifp->if_mtu) {
		ip->ip_len = htons(ip->ip_len);
		ip->ip_off = htons(ip->ip_off);
		if (!ip->ip_sum)
			ip->ip_sum = in_cksum(m, hlen);
		error = (*ifp->if_output)(ifp, m, (struct sockaddr *)dst);
		goto done;
	}
	/*
	 * Too large for interface; fragment if possible.
	 * Must be able to put at least 8 bytes per fragment.
	 */
	ip_off = 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 < ip->ip_len; off += len) {
		MGET(m, M_DONTWAIT, MT_HEADER);
		if (m == 0) {
			m = m0;
			error = ENOBUFS;
			goto bad;
		}
		m->m_off = MMAXOFF - hlen;
		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 >= ip->ip_len)
			len = ip->ip_len - off;
		else
			mhip->ip_off |= IP_MF;
		mhip->ip_len = htons((u_short)(len + mhlen));
		m->m_next = m_copy(m0, off, len);
		if (m->m_next == 0) {
			error = ENOBUFS;	/* ??? */
			goto sendorfree;
		}
		mhip->ip_off = htons((u_short)mhip->ip_off);
		mhip->ip_sum = 0;
		mhip->ip_sum = in_cksum(m, mhlen);
		*mnext = m;
		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,
			    (struct sockaddr *)dst);
		else
			FREE_MB_T(m);
	}
    }
done:
	if (!error)
		ipf_frouteok[0]++;
	else
		ipf_frouteok[1]++;

	if (ro->ro_rt != NULL) {
		RTFREE(ro->ro_rt);
	}
	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(fin)
	fr_info_t *fin;
{
	struct sockaddr_in *dst;
	struct route iproute;
	void *rtifp;

	bzero((char *)&iproute, sizeof(iproute));
	dst = (struct sockaddr_in *)&iproute.ro_dst;
	dst->sin_family = AF_INET;
	dst->sin_addr.s_addr = fin->fin_saddr;
	rtalloc(&iproute);
	if (iproute.ro_rt == NULL)
		return 0;
	rtifp = iproute.ro_rt->rt_ifp;
	RTFREE(iproute.ro_rt);
	return (fin->fin_ifp == rtifp);
}


/*
 * return the first IP Address associated with an interface
 */
int
ipf_ifpaddr(softc, v, atype, ifptr, inp, inpmask)
	ipf_main_softc_t *softc;
	int v, atype;
	void *ifptr;
	i6addr_t *inp, *inpmask;
{
	struct sockaddr_in *sin, *mask;
	struct in_ifaddr *ia;
	struct ifnet *ifp;

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

	ifp = ifptr;
	if (ifp == NULL)
		return -1;

	for (ia = in_ifaddr; ia != NULL; ia = ia->ia_next)
		if (ia->ia_ifp == ifp) {
			sin = (struct sockaddr_in *)&ia->ia_addr;
			break;
		}

	if (ia == NULL)
		return -1;

	if (atype == FRI_BROADCAST)
		sin = (struct sockaddr_in *)&ia->ia_broadaddr;
	else if (atype == FRI_PEERADDR)
		sin = (struct sockaddr_in *)&ia->ia_dstaddr;
	mask = (struct sockaddr_in *)&ia->ia_subnetmask;

	return ipf_ifpfillv4addr(atype, sin, mask, &inp->in4, &inpmask->in4);
}


u_32_t
ipf_newisn(fin)
	fr_info_t *fin;
{
	static iss_seq_off = 0;
	u_char hash[16];
	u_32_t newiss;
	MD5_CTX ctx;

	/*
	 * Compute the base value of the ISS.  It is a hash
	 * of (saddr, sport, daddr, dport, secret).
	 */
	MD5Init(&ctx);

	MD5Update(&ctx, (u_char *) &fin->fin_fi.fi_src,
		  sizeof(fin->fin_fi.fi_src));
	MD5Update(&ctx, (u_char *) &fin->fin_fi.fi_dst,
		  sizeof(fin->fin_fi.fi_dst));
	MD5Update(&ctx, (u_char *) &fin->fin_dat, sizeof(fin->fin_dat));

	MD5Update(&ctx, ipf_iss_secret, sizeof(ipf_iss_secret));

	MD5Final(hash, &ctx);

	memcpy(&newiss, hash, sizeof(newiss));

	/*
	 * Now increment our "timer", and add it in to
	 * the computed value.
	 *
	 * XXX Use `addin'?
	 * XXX TCP_ISSINCR too large to use?
	 */
	iss_seq_off += 0x00010000;
	newiss += iss_seq_off;
	return newiss;
}


/* ------------------------------------------------------------------------ */
/* Function:    ipf_nextipid                                                */
/* Returns:     int - 0 == success, -1 == error (packet should be droppped) */
/* Parameters:  fin(I) - pointer to packet information                      */
/*                                                                          */
/* Returns the next IPv4 ID to use for this packet.                         */
/* ------------------------------------------------------------------------ */
INLINE u_short
ipf_nextipid(fin)
	fr_info_t *fin;
{
	u_short id;

	id = ipid++;

	return id;
}


INLINE int
ipf_checkv4sum(fin)
	fr_info_t *fin;
{
	if ((fin->fin_flx & FI_NOCKSUM) != 0)
		return 0;

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

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

	if (ipf_checkl4sum(fin) == -1) {
		fin->fin_flx |= FI_BAD;
		return -1;
	}
	return 0;
}


/* ------------------------------------------------------------------------ */
/* 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.                                  */
/* ------------------------------------------------------------------------ */
void *
ipf_pullup(xmin, fin, len)
	mb_t *xmin;
	fr_info_t *fin;
	int len;
{
	int out = fin->fin_out, dpoff, ipoff;
	mb_t *m = xmin;
	char *ip;

	if (m == NULL)
		return NULL;

	ip = (char *)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;

		if (m != n) {
			for (; n->m_next != m; n = n->m_next)
				;
		} else {
			n = NULL;
		}

		if (len > MLEN) {
			FREE_MB_T(*fin->fin_mp);
			m = NULL;
			n = NULL;
		} else {
			m = m_pullup(m, len);
		}

		if (n != NULL)
			n->m_next = m;

		if (m == NULL) {
			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, char *) + ipoff;

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

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


int
ipf_inject(fin, m)
	fr_info_t *fin;
	mb_t *m;
{
	int error;

	if (fin->fin_out == 0) {
		struct ifqueue *ifq;

		ifq = &ipintrq;

		if (IF_QFULL(ifq)) {
			IF_DROP(ifq);
			FREE_MB_T(m);
			error = ENOBUFS;
		} else {
			IF_ENQUEUE(ifq, m);
			error = 0;
		}
	} else {
		error = ip_output(m, NULL, NULL, IP_FORWARDING, NULL);
	}

	return error;
}


/*
 * In the face of no kernel random function, this is implemented...it is
 * not meant to be random, just a fill in.
 */
int
ipf_random()
{
	static int last = 0;
	static int calls = 0;
	struct timeval tv;
	int number;

	GETKTIME(&tv);
	last *= tv.tv_usec + calls++;
	last += (int)&range * ipf_ticks;
	number = last + tv.tv_sec;
	return number;
}


u_short
ipf_pcksum(fin, hlen, sum)
{
	u_short sum2;

	slen = fin->fin_plen - hlen;
	m->m_off += hlen;
	m->m_len -= hlen;
	sum2 = in_cksum(fin->fin_m, slen);
	m->m_len += hlen;
	m->m_off -= 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;
}