source: vbox/trunk/src/VBox/Devices/Network/slirp/ip_input.c@ 15450

/*
 * Copyright (c) 1982, 1986, 1988, 1993
 *      The Regents of the University of California.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *      This product includes software developed by the University of
 *      California, Berkeley and its contributors.
 * 4. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 *      @(#)ip_input.c  8.2 (Berkeley) 1/4/94
 * ip_input.c,v 1.11 1994/11/16 10:17:08 jkh Exp
 */

/*
 * Changes and additions relating to SLiRP are
 * Copyright (c) 1995 Danny Gasparovski.
 *
 * Please read the file COPYRIGHT for the
 * terms and conditions of the copyright.
 */

#include <slirp.h>
#include "ip_icmp.h"


/*
 * IP initialization: fill in IP protocol switch table.
 * All protocols not implemented in kernel go to raw IP protocol handler.
 */
void
ip_init(PNATState pData)
{
#ifndef VBOX_WITH_BSD_REASS
    ipq.next = ipq.prev = ptr_to_u32(pData, &ipq);
#else /* !VBOX_WITH_BSD_REASS */
    int i = 0;
    for (i = 0; i < IPREASS_NHASH; ++i)
        TAILQ_INIT(&ipq[i]);
    maxnipq = 100; /* ??? */
    maxfragsperpacket = 16;
    nipq = 0;
#endif /* VBOX_WITH_BSD_REASS */
    ip_currid = tt.tv_sec & 0xffff;
    udp_init(pData);
    tcp_init(pData);
}

/*
 * Ip input routine.  Checksum and byte swap header.  If fragmented
 * try to reassemble.  Process options.  Pass to next level.
 */
void
ip_input(PNATState pData, struct mbuf *m)
{
    register struct ip *ip;
    int hlen;

    DEBUG_CALL("ip_input");
    DEBUG_ARG("m = %lx", (long)m);
    DEBUG_ARG("m_len = %d", m->m_len);

    ipstat.ips_total++;

    if (m->m_len < sizeof(struct ip))
    {
        ipstat.ips_toosmall++;
        return;
    }

    ip = mtod(m, struct ip *);
    if (ip->ip_v != IPVERSION)
    {
        ipstat.ips_badvers++;
        goto bad;
    }

    hlen = ip->ip_hl << 2;
    if (   hlen < sizeof(struct ip)
        || hlen > m->m_len)
    {
        /* min header length */
        ipstat.ips_badhlen++;                     /* or packet too short */
        goto bad;
    }

    /* keep ip header intact for ICMP reply
     * ip->ip_sum = cksum(m, hlen);
     * if (ip->ip_sum) {
     */
    if(cksum(m,hlen))
    {
        ipstat.ips_badsum++;
        goto bad;
    }

    /*
     * Convert fields to host representation.
     */
    NTOHS(ip->ip_len);
    if (ip->ip_len < hlen)
    {
        ipstat.ips_badlen++;
        goto bad;
    }
    NTOHS(ip->ip_id);
    NTOHS(ip->ip_off);

    /*
     * Check that the amount of data in the buffers
     * is as at least much as the IP header would have us expect.
     * Trim mbufs if longer than we expect.
     * Drop packet if shorter than we expect.
     */
    if (m->m_len < ip->ip_len)
    {
        ipstat.ips_tooshort++;
        goto bad;
    }
    /* Should drop packet if mbuf too long? hmmm... */
    if (m->m_len > ip->ip_len)
        m_adj(m, ip->ip_len - m->m_len);

    /* check ip_ttl for a correct ICMP reply */
    if (ip->ip_ttl==0 || ip->ip_ttl == 1)
    {
        icmp_error(pData, m, ICMP_TIMXCEED,ICMP_TIMXCEED_INTRANS, 0,"ttl");
        goto bad;
    }

#ifdef VBOX_WITH_SLIRP_ICMP
    ip->ip_ttl--;
#endif
    /*
     * If offset or IP_MF are set, must reassemble.
     * Otherwise, nothing need be done.
     * (We could look in the reassembly queue to see
     * if the packet was previously fragmented,
     * but it's not worth the time; just let them time out.)
     *
     * XXX This should fail, don't fragment yet
     */
#ifndef VBOX_WITH_BSD_REASS
    if (ip->ip_off &~ IP_DF)
    {
        register struct ipq_t *fp;
        /*
         * Look for queue of fragments
         * of this datagram.
         */
        for (fp = u32_to_ptr(pData, ipq.next, struct ipq_t *);
                fp != &ipq;
                fp = u32_to_ptr(pData, fp->next, struct ipq_t *))
            if (   ip->ip_id == fp->ipq_id
                && ip->ip_src.s_addr == fp->ipq_src.s_addr
                && ip->ip_dst.s_addr == fp->ipq_dst.s_addr
                && ip->ip_p == fp->ipq_p)
                goto found;
        fp = 0;
found:

        /*
         * Adjust ip_len to not reflect header,
         * set ip_mff if more fragments are expected,
         * convert offset of this to bytes.
         */
        ip->ip_len -= hlen;
        if (ip->ip_off & IP_MF)
            ((struct ipasfrag *)ip)->ipf_mff |= 1;
        else
            ((struct ipasfrag *)ip)->ipf_mff &= ~1;

        ip->ip_off <<= 3;

        /*
         * If datagram marked as having more fragments
         * or if this is not the first fragment,
         * attempt reassembly; if it succeeds, proceed.
         */
        if (((struct ipasfrag *)ip)->ipf_mff & 1 || ip->ip_off)
        {
            ipstat.ips_fragments++;
            ip = ip_reass(pData, (struct ipasfrag *)ip, fp);
            if (ip == 0)
                return;
            ipstat.ips_reassembled++;
            m = dtom(pData, ip);
        }
        else
            if (fp)
                ip_freef(pData, fp);

    }
    else
        ip->ip_len -= hlen;
#else /* !VBOX_WITH_BSD_REASS */
    if (ip->ip_off & (IP_MF | IP_OFFMASK))
    {
        m = ip_reass(pData, m);
        if (m == NULL)
            return;
        ip = mtod(m, struct ip *);
        hlen = ip->ip_len;
    }
    else
        ip->ip_len -= hlen;
#endif /* VBOX_WITH_BSD_REASS */

    /*
     * Switch out to protocol's input routine.
     */
    ipstat.ips_delivered++;
    switch (ip->ip_p)
    {
        case IPPROTO_TCP:
            tcp_input(pData, m, hlen, (struct socket *)NULL);
            break;
        case IPPROTO_UDP:
            udp_input(pData, m, hlen);
            break;
        case IPPROTO_ICMP:
            icmp_input(pData, m, hlen);
            break;
        default:
            ipstat.ips_noproto++;
            m_free(pData, m);
    }
    return;
bad:
    m_freem(pData, m);
    return;
}

#ifndef VBOX_WITH_BSD_REASS
/*
 * Take incoming datagram fragment and try to
 * reassemble it into whole datagram.  If a chain for
 * reassembly of this datagram already exists, then it
 * is given as fp; otherwise have to make a chain.
 */
struct ip *
ip_reass(PNATState pData, register struct ipasfrag *ip, register struct ipq_t *fp)
{
    register struct mbuf *m = dtom(pData, ip);
    register struct ipasfrag *q;
    int hlen = ip->ip_hl << 2;
    int i, next;

    DEBUG_CALL("ip_reass");
    DEBUG_ARG("ip = %lx", (long)ip);
    DEBUG_ARG("fp = %lx", (long)fp);
    DEBUG_ARG("m = %lx", (long)m);

    /*
     * Presence of header sizes in mbufs
     * would confuse code below.
     * Fragment m_data is concatenated.
     */
    m->m_data += hlen;
    m->m_len -= hlen;

    /*
     * If first fragment to arrive, create a reassembly queue.
     */
    if (fp == 0)
    {
        struct mbuf *t;
        if ((t = m_get(pData)) == NULL) goto dropfrag;
        fp = mtod(t, struct ipq_t *);
        insque_32(pData, fp, &ipq);
        fp->ipq_ttl = IPFRAGTTL;
        fp->ipq_p = ip->ip_p;
        fp->ipq_id = ip->ip_id;
        fp->ipq_next = fp->ipq_prev = ptr_to_u32(pData, (struct ipasfrag *)fp);
        fp->ipq_src = ((struct ip *)ip)->ip_src;
        fp->ipq_dst = ((struct ip *)ip)->ip_dst;
        q = (struct ipasfrag *)fp;
        goto insert;
    }

    /*
     * Find a segment which begins after this one does.
     */
    for (q = u32_to_ptr(pData, fp->ipq_next, struct ipasfrag *);
         q != (struct ipasfrag *)fp;
         q = u32_to_ptr(pData, q->ipf_next, struct ipasfrag *))
        if (q->ip_off > ip->ip_off)
            break;

    /*
     * If there is a preceding segment, it may provide some of
     * our data already.  If so, drop the data from the incoming
     * segment.  If it provides all of our data, drop us.
     */
    if (u32_to_ptr(pData, q->ipf_prev, struct ipq_t *) != fp)
    {
        i = (u32_to_ptr(pData, q->ipf_prev, struct ipasfrag *))->ip_off +
            (u32_to_ptr(pData, q->ipf_prev, struct ipasfrag *))->ip_len - ip->ip_off;
        if (i > 0)
        {
            if (i >= ip->ip_len)
                goto dropfrag;
            m_adj(dtom(pData, ip), i);
            ip->ip_off += i;
            ip->ip_len -= i;
        }
    }

    /*
     * While we overlap succeeding segments trim them or,
     * if they are completely covered, dequeue them.
     */
    while (q != (struct ipasfrag *)fp && ip->ip_off + ip->ip_len > q->ip_off)
    {
        i = (ip->ip_off + ip->ip_len) - q->ip_off;
        if (i < q->ip_len) {
            q->ip_len -= i;
            q->ip_off += i;
            m_adj(dtom(pData, q), i);
            break;
        }
        q = u32_to_ptr(pData, q->ipf_next, struct ipasfrag *);
        m_freem(pData, dtom(pData, u32_to_ptr(pData, q->ipf_prev, struct ipasfrag *)));
        ip_deq(pData, u32_to_ptr(pData, q->ipf_prev, struct ipasfrag *));
    }

insert:
    /*
     * Stick new segment in its place;
     * check for complete reassembly.
     */
    ip_enq(pData, ip, u32_to_ptr(pData, q->ipf_prev, struct ipasfrag *));
    next = 0;
    for (q = u32_to_ptr(pData, fp->ipq_next, struct ipasfrag *);
         q != (struct ipasfrag *)fp;
         q = u32_to_ptr(pData, q->ipf_next, struct ipasfrag *))
    {
        if (q->ip_off != next)
            return (0);
        next += q->ip_len;
    }
    if (u32_to_ptr(pData, q->ipf_prev, struct ipasfrag *)->ipf_mff & 1)
        return (0);

    /*
     * Reassembly is complete; concatenate fragments.
     */
    q = u32_to_ptr(pData, fp->ipq_next, struct ipasfrag *);
    m = dtom(pData, q);

    q = u32_to_ptr(pData, q->ipf_next, struct ipasfrag *);
    while (q != (struct ipasfrag *)fp)
    {
        struct mbuf *t;
        t = dtom(pData, q);
        q = u32_to_ptr(pData, q->ipf_next, struct ipasfrag *);
        m_cat(pData, m, t);
    }

    /*
     * Create header for new ip packet by
     * modifying header of first packet;
     * dequeue and discard fragment reassembly header.
     * Make header visible.
     */
    ip = u32_to_ptr(pData, fp->ipq_next, struct ipasfrag *);

    /*
     * If the fragments concatenated to an mbuf that's
     * bigger than the total size of the fragment, then and
     * m_ext buffer was alloced. But fp->ipq_next points to
     * the old buffer (in the mbuf), so we must point ip
     * into the new buffer.
     */
    if (m->m_flags & M_EXT)
    {
        int delta;
        delta = (char *)ip - m->m_dat;
        ip = (struct ipasfrag *)(m->m_ext + delta);
    }

    /* DEBUG_ARG("ip = %lx", (long)ip);
     * ip=(struct ipasfrag *)m->m_data; */

    ip->ip_len = next;
    ip->ipf_mff &= ~1;
    ((struct ip *)ip)->ip_src = fp->ipq_src;
    ((struct ip *)ip)->ip_dst = fp->ipq_dst;
    remque_32(pData, fp);
    (void) m_free(pData, dtom(pData, fp));
    m = dtom(pData, ip);
    m->m_len += (ip->ip_hl << 2);
    m->m_data -= (ip->ip_hl << 2);

    return ((struct ip *)ip);

dropfrag:
    ipstat.ips_fragdropped++;
    m_freem(pData, m);
    return (0);
}

/*
 * Free a fragment reassembly header and all
 * associated datagrams.
 */
void
ip_freef(PNATState pData, struct ipq_t *fp)
{
    register struct ipasfrag *q, *p;

    for (q = u32_to_ptr(pData, fp->ipq_next, struct ipasfrag *);
         q != (struct ipasfrag *)fp;
         q = p)
    {
        p = u32_to_ptr(pData, q->ipf_next, struct ipasfrag *);
        ip_deq(pData, q);
        m_freem(pData, dtom(pData, q));
    }
    remque_32(pData, fp);
    (void) m_free(pData, dtom(pData, fp));
}

#else /* VBOX_WITH_BSD_REASS */

struct mbuf *
ip_reass(PNATState pData, struct mbuf* m)
{
    struct ip *ip;
    struct mbuf *p, *q, *nq, *t;
    struct ipq_t *fp = NULL;
    struct ipqhead *head;
    int i, hlen, next;
    u_short hash;

    /* If maxnipq or maxfragsperpacket are 0, never accept fragments. */
    if (   maxnipq == 0
        || maxfragsperpacket == 0)
    {
        ipstat.ips_fragments++;
        ipstat.ips_fragdropped++;
        m_freem(pData, m);
        return (NULL);
    }

    ip = mtod(m, struct ip *);
    hlen = ip->ip_hl << 2;

    hash = IPREASS_HASH(ip->ip_src.s_addr, ip->ip_id);
    head = &ipq[hash];

    /*
     * Look for queue of fragments
     * of this datagram.
     */
    TAILQ_FOREACH(fp, head, ipq_list)
        if (ip->ip_id == fp->ipq_id &&
            ip->ip_src.s_addr == fp->ipq_src.s_addr &&
            ip->ip_dst.s_addr == fp->ipq_dst.s_addr &&
            ip->ip_p == fp->ipq_p)
            goto found;

    fp = NULL;

    /*
     * Attempt to trim the number of allocated fragment queues if it
     * exceeds the administrative limit.
     */
    if ((nipq > maxnipq) && (maxnipq > 0))
    {
        /*
         * drop something from the tail of the current queue
         * before proceeding further
         */
        struct ipq_t *q = TAILQ_LAST(head, ipqhead);
        if (q == NULL)
        { 
            /* gak */
            for (i = 0; i < IPREASS_NHASH; i++)
            {
                struct ipq_t *r = TAILQ_LAST(&ipq[i], ipqhead);
                if (r)
                {
                    ipstat.ips_fragtimeout += r->ipq_nfrags;
                    ip_freef(pData, &ipq[i], r);
                    break;
                }
            }
        }
        else
        {
            ipstat.ips_fragtimeout += q->ipq_nfrags;
            ip_freef(pData, head, q);
        }
    }

found:
    /*
     * Adjust ip_len to not reflect header,
     * convert offset of this to bytes.
     */
    ip->ip_len -= hlen;
    if (ip->ip_off & IP_MF)
    {
        /*
         * Make sure that fragments have a data length
         * that's a non-zero multiple of 8 bytes.
         */
        if (ip->ip_len == 0 || (ip->ip_len & 0x7) != 0)
        {
            ipstat.ips_toosmall++; /* XXX */
            goto dropfrag;
        }
        m->m_flags |= M_FRAG;
    }
    else
        m->m_flags &= ~M_FRAG;
    ip->ip_off <<= 3;


    /*
     * Attempt reassembly; if it succeeds, proceed.
     * ip_reass() will return a different mbuf.
     */
    ipstat.ips_fragments++;
    m->m_hdr.header = ip;

    /* Previous ip_reass() started here. */
    /*
     * Presence of header sizes in mbufs
     * would confuse code below.
     */
    m->m_data += hlen;
    m->m_len -= hlen;

    /*
     * If first fragment to arrive, create a reassembly queue.
     */
    if (fp == NULL)
    {
        fp = malloc(sizeof(struct ipq_t));
        if (fp == NULL)
            goto dropfrag;
        TAILQ_INSERT_HEAD(head, fp, ipq_list);
        nipq++;
        fp->ipq_nfrags = 1;
        fp->ipq_ttl = IPFRAGTTL;
        fp->ipq_p = ip->ip_p;
        fp->ipq_id = ip->ip_id;
        fp->ipq_src = ip->ip_src;
        fp->ipq_dst = ip->ip_dst;
        fp->ipq_frags = m;
        m->m_nextpkt = NULL;
        goto done;
    }
    else
    {
        fp->ipq_nfrags++;
    }

#define GETIP(m)    ((struct ip*)((m)->m_hdr.header))


    /*
     * Find a segment which begins after this one does.
     */
    for (p = NULL, q = fp->ipq_frags; q; p = q, q = q->m_nextpkt)
        if (GETIP(q)->ip_off > ip->ip_off)
            break;

    /*
     * If there is a preceding segment, it may provide some of
     * our data already.  If so, drop the data from the incoming
     * segment.  If it provides all of our data, drop us, otherwise
     * stick new segment in the proper place.
     *
     * If some of the data is dropped from the the preceding
     * segment, then it's checksum is invalidated.
     */
    if (p)
    {
        i = GETIP(p)->ip_off + GETIP(p)->ip_len - ip->ip_off;
        if (i > 0)
        {
            if (i >= ip->ip_len)
                goto dropfrag;
            m_adj(m, i);
            ip->ip_off += i;
            ip->ip_len -= i;
        }
        m->m_nextpkt = p->m_nextpkt;
        p->m_nextpkt = m;
    }
    else
    {
        m->m_nextpkt = fp->ipq_frags;
        fp->ipq_frags = m;
    }

    /*
     * While we overlap succeeding segments trim them or,
     * if they are completely covered, dequeue them.
     */
    for (; q != NULL && ip->ip_off + ip->ip_len > GETIP(q)->ip_off;
         q = nq)
    {
        i = (ip->ip_off + ip->ip_len) - GETIP(q)->ip_off;
        if (i < GETIP(q)->ip_len)
        {
            GETIP(q)->ip_len -= i;
            GETIP(q)->ip_off += i;
            m_adj(q, i);
            break;
        }
        nq = q->m_nextpkt;
        m->m_nextpkt = nq;
        ipstat.ips_fragdropped++;
        fp->ipq_nfrags--;
        m_freem(pData, q);
    }

    /*
     * Check for complete reassembly and perform frag per packet
     * limiting.
     *
     * Frag limiting is performed here so that the nth frag has
     * a chance to complete the packet before we drop the packet.
     * As a result, n+1 frags are actually allowed per packet, but
     * only n will ever be stored. (n = maxfragsperpacket.)
     *
     */
    next = 0;
    for (p = NULL, q = fp->ipq_frags; q; p = q, q = q->m_nextpkt)
    {
        if (GETIP(q)->ip_off != next)
        {
            if (fp->ipq_nfrags > maxfragsperpacket)
            {
                ipstat.ips_fragdropped += fp->ipq_nfrags;
                ip_freef(pData, head, fp);
            }
            goto done;
        }
        next += GETIP(q)->ip_len;
    }
    /* Make sure the last packet didn't have the IP_MF flag */
    if (p->m_flags & M_FRAG)
    {
        if (fp->ipq_nfrags > maxfragsperpacket)
        {
            ipstat.ips_fragdropped += fp->ipq_nfrags;
            ip_freef(pData, head, fp);
        }
        goto done;
    }

    /*
     * Reassembly is complete.  Make sure the packet is a sane size.
     */
    q = fp->ipq_frags;
    ip = GETIP(q);
    if (next + (ip->ip_hl << 2) > IP_MAXPACKET)
    {
        ipstat.ips_fragdropped += fp->ipq_nfrags;
        ip_freef(pData, head, fp);
        goto done;
    }

    /*
     * Concatenate fragments.
     */
    m = q;
#if 0
    t = m->m_next;
    m->m_next = NULL;
    m_cat(pData, m, t);
#endif
    nq = q->m_nextpkt;
    q->m_nextpkt = NULL;
    for (q = nq; q != NULL; q = nq)
    {
        nq = q->m_nextpkt;
        q->m_nextpkt = NULL;
        m_cat(pData, m, q);
    }

    /*
     * Create header for new ip packet by modifying header of first
     * packet;  dequeue and discard fragment reassembly header.
     * Make header visible.
     */
#if 0
    ip->ip_len = (ip->ip_hl << 2) + next;
#else
    ip->ip_len = next;
#endif
    ip->ip_src = fp->ipq_src;
    ip->ip_dst = fp->ipq_dst;
    TAILQ_REMOVE(head, fp, ipq_list);
    nipq--;
    free(fp);

    m->m_len += (ip->ip_hl << 2);
    m->m_data -= (ip->ip_hl << 2);
    /* some debugging cruft by sklower, below, will go away soon */
#if 0
    if (m->m_flags & M_PKTHDR)    /* XXX this should be done elsewhere */
        m_fixhdr(m);
#endif
    ipstat.ips_reassembled++;
    return (m);

dropfrag:
    ipstat.ips_fragdropped++;
    if (fp != NULL)
        fp->ipq_nfrags--;
    m_freem(pData, m);

done:
    return NULL;

#undef GETIP
}

void
ip_freef(PNATState pData, struct ipqhead *fhp, struct ipq_t *fp)
{
    struct mbuf *q;

    while (fp->ipq_frags)
    {
        q = fp->ipq_frags;
        fp->ipq_frags = q->m_nextpkt;
        m_freem(pData, q);
    }
    TAILQ_REMOVE(fhp, fp, ipq_list);
    free(fp);
    nipq--;
}
#endif /* VBOX_WITH_BSD_REASS */

#ifndef VBOX_WITH_BSD_REASS
/*
 * Put an ip fragment on a reassembly chain.
 * Like insque, but pointers in middle of structure.
 */
void
ip_enq(PNATState pData, register struct ipasfrag *p, register struct ipasfrag *prev)
{
    DEBUG_CALL("ip_enq");
    DEBUG_ARG("prev = %lx", (long)prev);
    p->ipf_prev = ptr_to_u32(pData, prev);
    p->ipf_next = prev->ipf_next;
    u32_to_ptr(pData, prev->ipf_next, struct ipasfrag *)->ipf_prev = ptr_to_u32(pData, p);
    prev->ipf_next = ptr_to_u32(pData, p);
}

/*
 * To ip_enq as remque is to insque.
 */
void
ip_deq(PNATState pData, register struct ipasfrag *p)
{
    struct ipasfrag *prev = u32_to_ptr(pData, p->ipf_prev, struct ipasfrag *);
    struct ipasfrag *next = u32_to_ptr(pData, p->ipf_next, struct ipasfrag *);
    u32ptr_done(pData, prev->ipf_next, p);
    prev->ipf_next = p->ipf_next;
    next->ipf_prev = p->ipf_prev;
}
#endif /* !VBOX_WITH_BSD_REASS */

/*
 * IP timer processing;
 * if a timer expires on a reassembly
 * queue, discard it.
 */
void
ip_slowtimo(PNATState pData)
{
    register struct ipq_t *fp;

#ifndef VBOX_WITH_BSD_REASS
    DEBUG_CALL("ip_slowtimo");

    fp = u32_to_ptr(pData, ipq.next, struct ipq_t *);
    if (fp == 0)
        return;

    while (fp != &ipq)
    {
        --fp->ipq_ttl;
        fp = u32_to_ptr(pData, fp->next, struct ipq_t *);
        if (u32_to_ptr(pData, fp->prev, struct ipq_t *)->ipq_ttl == 0)
        {
            ipstat.ips_fragtimeout++;
            ip_freef(pData, u32_to_ptr(pData, fp->prev, struct ipq_t *));
        }
        }
#else /* VBOX_WITH_BSD_REASS */
    /* XXX: the fragment expiration is the same but requier
     * additional loop see (see ip_input.c in FreeBSD tree)
     */
    int i;
    DEBUG_CALL("ip_slowtimo");
    for (i = 0; i < IPREASS_NHASH; i++)
    {
        for(fp = TAILQ_FIRST(&ipq[i]); fp;)
        {
            struct ipq_t *fpp;

            fpp = fp;
            fp = TAILQ_NEXT(fp, ipq_list);
            if(--fpp->ipq_ttl == 0) {
                ipstat.ips_fragtimeout += fpp->ipq_nfrags;
                ip_freef(pData, &ipq[i], fpp);
            }
        }
    }
    /*
     * If we are over the maximum number of fragments
     * (due to the limit being lowered), drain off
     * enough to get down to the new limit.
     */
    if (maxnipq >= 0 && nipq > maxnipq)
    {
        for (i = 0; i < IPREASS_NHASH; i++)
        {
            while (nipq > maxnipq && !TAILQ_EMPTY(&ipq[i]))
            {
                ipstat.ips_fragdropped += TAILQ_FIRST(&ipq[i])->ipq_nfrags;
                ip_freef(pData, &ipq[i], TAILQ_FIRST(&ipq[i]));
            }
        }
    }
#endif /* VBOX_WITH_BSD_REASS */
}


/*
 * Strip out IP options, at higher
 * level protocol in the kernel.
 * Second argument is buffer to which options
 * will be moved, and return value is their length.
 * (XXX) should be deleted; last arg currently ignored.
 */
void
ip_stripoptions(struct mbuf *m, struct mbuf *mopt)
{
    register int i;
    struct ip *ip = mtod(m, struct ip *);
    register caddr_t opts;
    int olen;

    olen = (ip->ip_hl<<2) - sizeof(struct ip);
    opts = (caddr_t)(ip + 1);
    i = m->m_len - (sizeof(struct ip) + olen);
    memcpy(opts, opts  + olen, (unsigned)i);
    m->m_len -= olen;

    ip->ip_hl = sizeof(struct ip) >> 2;
}