ip_input.c

/*
 * 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 <osdep.h>
#include "ip_icmp.h"

#ifdef LOG_ENABLED
struct ipstat ipstat;
#endif

struct ipq ipq;

static struct ip *ip_reass(register struct ip *ip, register struct ipq *fp);
static void ip_freef(struct ipq *fp);
static void ip_enq(register struct ipasfrag *p, register struct ipasfrag *prev);
static void ip_deq(register struct ipasfrag *p);

/*
 * IP initialization: fill in IP protocol switch table.
 * All protocols not implemented in kernel go to raw IP protocol handler.
 */
void ip_init()
{
    ipq.ip_link.next = ipq.ip_link.prev = &ipq.ip_link;
    ip_id = tt.tv_sec & 0xffff;
    udp_init();
    tcp_init();
}

/*
 * Ip input routine.  Checksum and byte swap header.  If fragmented
 * try to reassemble.  Process options.  Pass to next level.
 */
void ip_input(m) 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);

    STAT(ipstat.ips_total++);

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

    ip = mtod(m, struct ip *);

    if (ip->ip_v != IPVERSION) {
        STAT(ipstat.ips_badvers++);
        goto bad;
    }

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

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

    if (slirp_restrict) {
        if (memcmp(&ip->ip_dst.s_addr, &special_addr, 3)) {
            if (ip->ip_dst.s_addr == 0xffffffff && ip->ip_p != IPPROTO_UDP)
                goto bad;
        } else {
            int host = ntohl(ip->ip_dst.s_addr) & 0xff;
            struct ex_list *ex_ptr;

            if (host == 0xff)
                goto bad;

            for (ex_ptr = exec_list; ex_ptr; ex_ptr = ex_ptr->ex_next)
                if (ex_ptr->ex_addr == host)
                    break;

            if (!ex_ptr)
                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(m, ICMP_TIMXCEED, ICMP_TIMXCEED_INTRANS, 0, "ttl");
        goto bad;
    }

    /*
     * Process options and, if not destined for us,
     * ship it on.  ip_dooptions returns 1 when an
     * error was detected (causing an icmp message
     * to be sent and the original packet to be freed).
     */
    /* We do no IP options */
    /*	if (hlen > sizeof (struct ip) && ip_dooptions(m))
     *		goto next;
     */
    /*
     * 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
     */
    if (ip->ip_off & ~IP_DF) {
        register struct ipq *fp;
        struct qlink *l;
        /*
         * Look for queue of fragments
         * of this datagram.
         */
        for (l = ipq.ip_link.next; l != &ipq.ip_link; l = l->next) {
            fp = container_of(l, struct ipq, ip_link);
            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;
    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)
            ip->ip_tos |= 1;
        else
            ip->ip_tos &= ~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 (ip->ip_tos & 1 || ip->ip_off) {
            STAT(ipstat.ips_fragments++);
            ip = ip_reass(ip, fp);
            if (ip == 0)
                return;
            STAT(ipstat.ips_reassembled++);
            m = dtom(ip);
        } else if (fp)
            ip_freef(fp);

    } else
        ip->ip_len -= hlen;

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

#define iptofrag(P) ((struct ipasfrag *)(((char *)(P)) - sizeof(struct qlink)))
#define fragtoip(P) ((struct ip *)(((char *)(P)) + sizeof(struct qlink)))
/*
 * 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.
 */
static struct ip *ip_reass(register struct ip *ip, register struct ipq *fp)
{
    register struct mbuf *m = dtom(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()) == NULL)
            goto dropfrag;
        fp = mtod(t, struct ipq *);
        insque(&fp->ip_link, &ipq.ip_link);
        fp->ipq_ttl = IPFRAGTTL;
        fp->ipq_p = ip->ip_p;
        fp->ipq_id = ip->ip_id;
        fp->frag_link.next = fp->frag_link.prev = &fp->frag_link;
        fp->ipq_src = ip->ip_src;
        fp->ipq_dst = ip->ip_dst;
        q = (struct ipasfrag *)fp;
        goto insert;
    }

    /*
     * Find a segment which begins after this one does.
     */
    for (q = fp->frag_link.next; q != (struct ipasfrag *)&fp->frag_link;
         q = q->ipf_next)
        if (q->ipf_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 (q->ipf_prev != &fp->frag_link) {
        struct ipasfrag *pq = q->ipf_prev;
        i = pq->ipf_off + pq->ipf_len - ip->ip_off;
        if (i > 0) {
            if (i >= ip->ip_len)
                goto dropfrag;
            m_adj(dtom(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->frag_link &&
           ip->ip_off + ip->ip_len > q->ipf_off) {
        i = (ip->ip_off + ip->ip_len) - q->ipf_off;
        if (i < q->ipf_len) {
            q->ipf_len -= i;
            q->ipf_off += i;
            m_adj(dtom(q), i);
            break;
        }
        q = q->ipf_next;
        m_freem(dtom(q->ipf_prev));
        ip_deq(q->ipf_prev);
    }

insert:
    /*
     * Stick new segment in its place;
     * check for complete reassembly.
     */
    ip_enq(iptofrag(ip), q->ipf_prev);
    next = 0;
    for (q = fp->frag_link.next; q != (struct ipasfrag *)&fp->frag_link;
         q = q->ipf_next) {
        if (q->ipf_off != next)
            return (0);
        next += q->ipf_len;
    }
    if (((struct ipasfrag *)(q->ipf_prev))->ipf_tos & 1)
        return (0);

    /*
     * Reassembly is complete; concatenate fragments.
     */
    q = fp->frag_link.next;
    m = dtom(q);

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

    /*
     * Create header for new ip packet by
     * modifying header of first packet;
     * dequeue and discard fragment reassembly header.
     * Make header visible.
     */
    q = fp->frag_link.next;

    /*
     * 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;
        q = (struct ipasfrag *)(m->m_ext + delta);
    }

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

    ip = fragtoip(q);
    ip->ip_len = next;
    ip->ip_tos &= ~1;
    ip->ip_src = fp->ipq_src;
    ip->ip_dst = fp->ipq_dst;
    remque(&fp->ip_link);
    (void)m_free(dtom(fp));
    m->m_len += (ip->ip_hl << 2);
    m->m_data -= (ip->ip_hl << 2);

    return ip;

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

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

    for (q = fp->frag_link.next; q != (struct ipasfrag *)&fp->frag_link;
         q = p) {
        p = q->ipf_next;
        ip_deq(q);
        m_freem(dtom(q));
    }
    remque(&fp->ip_link);
    (void)m_free(dtom(fp));
}

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

/*
 * To ip_enq as remque is to insque.
 */
static void ip_deq(register struct ipasfrag *p)
{
    ((struct ipasfrag *)(p->ipf_prev))->ipf_next = p->ipf_next;
    ((struct ipasfrag *)(p->ipf_next))->ipf_prev = p->ipf_prev;
}

/*
 * IP timer processing;
 * if a timer expires on a reassembly
 * queue, discard it.
 */
void ip_slowtimo()
{
    struct qlink *l;

    DEBUG_CALL("ip_slowtimo");

    l = ipq.ip_link.next;

    if (l == 0)
        return;

    while (l != &ipq.ip_link) {
        struct ipq *fp = container_of(l, struct ipq, ip_link);
        l = l->next;
        if (--fp->ipq_ttl == 0) {
            STAT(ipstat.ips_fragtimeout++);
            ip_freef(fp);
        }
    }
}

/*
 * Do option processing on a datagram,
 * possibly discarding it if bad options are encountered,
 * or forwarding it if source-routed.
 * Returns 1 if packet has been forwarded/freed,
 * 0 if the packet should be processed further.
 */

#ifdef notdef

int ip_dooptions(m) struct mbuf *m;
{
    register struct ip *ip = mtod(m, struct ip *);
    register u_char *cp;
    register struct ip_timestamp *ipt;
    register struct in_ifaddr *ia;
    /*	int opt, optlen, cnt, off, code, type = ICMP_PARAMPROB, forward = 0; */
    int opt, optlen, cnt, off, code, type, forward = 0;
    struct in_addr *sin, dst;
    typedef u_int32_t n_time;
    n_time ntime;

    dst = ip->ip_dst;
    cp = (u_char *)(ip + 1);
    cnt = (ip->ip_hl << 2) - sizeof(struct ip);
    for (; cnt > 0; cnt -= optlen, cp += optlen) {
        opt = cp[IPOPT_OPTVAL];
        if (opt == IPOPT_EOL)
            break;
        if (opt == IPOPT_NOP)
            optlen = 1;
        else {
            optlen = cp[IPOPT_OLEN];
            if (optlen <= 0 || optlen > cnt) {
                code = &cp[IPOPT_OLEN] - (u_char *)ip;
                goto bad;
            }
        }
        switch (opt) {
        default:
            break;

        /*
         * Source routing with record.
         * Find interface with current destination address.
         * If none on this machine then drop if strictly routed,
         * or do nothing if loosely routed.
         * Record interface address and bring up next address
         * component.  If strictly routed make sure next
         * address is on directly accessible net.
         */
        case IPOPT_LSRR:
        case IPOPT_SSRR:
            if ((off = cp[IPOPT_OFFSET]) < IPOPT_MINOFF) {
                code = &cp[IPOPT_OFFSET] - (u_char *)ip;
                goto bad;
            }
            ipaddr.sin_addr = ip->ip_dst;
            ia = (struct in_ifaddr *)ifa_ifwithaddr((struct sockaddr *)&ipaddr);
            if (ia == 0) {
                if (opt == IPOPT_SSRR) {
                    type = ICMP_UNREACH;
                    code = ICMP_UNREACH_SRCFAIL;
                    goto bad;
                }
                /*
                 * Loose routing, and not at next destination
                 * yet; nothing to do except forward.
                 */
                break;
            }
            off--;
            / *0 origin * / if (off > optlen - sizeof(struct in_addr))
            {
                /*
                 * End of source route.  Should be for us.
                 */
                save_rte(cp, ip->ip_src);
                break;
            }
            /*
             * locate outgoing interface
             */
            bcopy((caddr_t)(cp + off), (caddr_t)&ipaddr.sin_addr,
                  sizeof(ipaddr.sin_addr));
            if (opt == IPOPT_SSRR) {
#define INA struct in_ifaddr *
#define SA struct sockaddr *
                if ((ia = (INA)ifa_ifwithdstaddr((SA)&ipaddr)) == 0)
                    ia = (INA)ifa_ifwithnet((SA)&ipaddr);
            } else
                ia = ip_rtaddr(ipaddr.sin_addr);
            if (ia == 0) {
                type = ICMP_UNREACH;
                code = ICMP_UNREACH_SRCFAIL;
                goto bad;
            }
            ip->ip_dst = ipaddr.sin_addr;
            bcopy((caddr_t) & (IA_SIN(ia)->sin_addr), (caddr_t)(cp + off),
                  sizeof(struct in_addr));
            cp[IPOPT_OFFSET] += sizeof(struct in_addr);
            /*
             * Let ip_intr's mcast routing check handle mcast pkts
             */
            forward = !IN_MULTICAST(ntohl(ip->ip_dst.s_addr));
            break;

        case IPOPT_RR:
            if ((off = cp[IPOPT_OFFSET]) < IPOPT_MINOFF) {
                code = &cp[IPOPT_OFFSET] - (u_char *)ip;
                goto bad;
            }
            /*
             * If no space remains, ignore.
             */
            off--;
            *0 origin *if (off > optlen - sizeof(struct in_addr)) break;
            bcopy((caddr_t)(&ip->ip_dst), (caddr_t)&ipaddr.sin_addr,
                  sizeof(ipaddr.sin_addr));
            /*
             * locate outgoing interface; if we're the destination,
             * use the incoming interface (should be same).
             */
            if ((ia = (INA)ifa_ifwithaddr((SA)&ipaddr)) == 0 &&
                (ia = ip_rtaddr(ipaddr.sin_addr)) == 0) {
                type = ICMP_UNREACH;
                code = ICMP_UNREACH_HOST;
                goto bad;
            }
            bcopy((caddr_t) & (IA_SIN(ia)->sin_addr), (caddr_t)(cp + off),
                  sizeof(struct in_addr));
            cp[IPOPT_OFFSET] += sizeof(struct in_addr);
            break;

        case IPOPT_TS:
            code = cp - (u_char *)ip;
            ipt = (struct ip_timestamp *)cp;
            if (ipt->ipt_len < 5)
                goto bad;
            if (ipt->ipt_ptr > ipt->ipt_len - sizeof(int32_t)) {
                if (++ipt->ipt_oflw == 0)
                    goto bad;
                break;
            }
            sin = (struct in_addr *)(cp + ipt->ipt_ptr - 1);
            switch (ipt->ipt_flg) {
            case IPOPT_TS_TSONLY:
                break;

            case IPOPT_TS_TSANDADDR:
                if (ipt->ipt_ptr + sizeof(n_time) + sizeof(struct in_addr) >
                    ipt->ipt_len)
                    goto bad;
                ipaddr.sin_addr = dst;
                ia = (INA)ifaof_ i f p foraddr((SA)&ipaddr, m->m_pkthdr.rcvif);
                if (ia == 0)
                    continue;
                bcopy((caddr_t)&IA_SIN(ia)->sin_addr, (caddr_t)sin,
                      sizeof(struct in_addr));
                ipt->ipt_ptr += sizeof(struct in_addr);
                break;

            case IPOPT_TS_PRESPEC:
                if (ipt->ipt_ptr + sizeof(n_time) + sizeof(struct in_addr) >
                    ipt->ipt_len)
                    goto bad;
                bcopy((caddr_t)sin, (caddr_t)&ipaddr.sin_addr,
                      sizeof(struct in_addr));
                if (ifa_ifwithaddr((SA)&ipaddr) == 0)
                    continue;
                ipt->ipt_ptr += sizeof(struct in_addr);
                break;

            default:
                goto bad;
            }
            ntime = iptime();
            bcopy((caddr_t)&ntime, (caddr_t)cp + ipt->ipt_ptr - 1,
                  sizeof(n_time));
            ipt->ipt_ptr += sizeof(n_time);
        }
    }
    if (forward) {
        ip_forward(m, 1);
        return (1);
    }
}
}
return (0);
bad :
    /* ip->ip_len -= ip->ip_hl << 2;   XXX icmp_error adds in hdr length */

    /* Not yet */
    icmp_error(m, type, code, 0, 0);

STAT(ipstat.ips_badoptions++);
return (1);
}

#endif /* notdef */

/*
 * 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(m, mopt) register 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;
}