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

static struct ip *ip_reass(Slirp *slirp, struct ip *ip, struct ipq *fp);
static void ip_freef(Slirp *slirp, 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(Slirp *slirp)
{
    slirp->ipq.ip_link.next = slirp->ipq.ip_link.prev = &slirp->ipq.ip_link;
    udp_init(slirp);
    tcp_init(slirp);
    icmp_init(slirp);
}

void ip_cleanup(Slirp *slirp)
{
    udp_cleanup(slirp);
    tcp_cleanup(slirp);
    icmp_cleanup(slirp);
}

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

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

        if (m->m_len < sizeof (struct ip)) {
                return;
        }

        ip = mtod(m, struct ip *);

        if (ip->ip_v != IPVERSION) {
                goto bad;
        }

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

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

        /*
         * Convert fields to host representation.
         */
        NTOHS(ip->ip_len);
        if (ip->ip_len < hlen) {
                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) {
                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) {
          icmp_error(m, ICMP_TIMXCEED,ICMP_TIMXCEED_INTRANS, 0,"ttl");
          goto bad;
        }

        /*
         * 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 = (struct qlink *)slirp->ipq.ip_link.next; l != &slirp->ipq.ip_link;
                     l = (struct qlink *)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) {
                        ip = ip_reass(slirp, ip, fp);
                        if (ip == NULL)
                                return;
                        m = dtom(slirp, ip);
                } else
                        if (fp)
                           ip_freef(slirp, fp);

        } else
                ip->ip_len -= hlen;

        /*
         * Switch out to protocol's input routine.
         */
        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:
                m_free(m);
        }
        return;
bad:
        m_free(m);
}

#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(Slirp *slirp, struct ip *ip, struct ipq *fp)
{
        register struct mbuf *m = dtom(slirp, 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 == NULL) {
          struct mbuf *t = m_get(slirp);

          if (t == NULL) {
              goto dropfrag;
          }
          fp = mtod(t, struct ipq *);
          insque(&fp->ip_link, &slirp->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 = (struct ipasfrag *)fp->frag_link.next; q != (struct ipasfrag *)&fp->frag_link;
            q = (struct ipasfrag *)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 = (struct ipasfrag *)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(slirp, 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(slirp, q), i);
                        break;
                }
                q = (struct ipasfrag *)q->ipf_next;
                m_free(dtom(slirp, q->ipf_prev));
                ip_deq((struct ipasfrag*)q->ipf_prev);
        }

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

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

        q = (struct ipasfrag *) q->ipf_next;
        while (q != (struct ipasfrag*)&fp->frag_link) {
          struct mbuf *t = dtom(slirp, 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 = (struct ipasfrag*)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 = (char *)q - m->m_dat;
          q = (struct ipasfrag *)(m->m_ext + delta);
        }

    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(slirp, fp));
        m->m_len += (ip->ip_hl << 2);
        m->m_data -= (ip->ip_hl << 2);

        return ip;

dropfrag:
        m_free(m);
        return NULL;
}

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

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

        DEBUG_CALL("ip_slowtimo");

    l = (struct qlink*)slirp->ipq.ip_link.next;

        if (l == NULL)
           return;

    while (l != &slirp->ipq.ip_link) {
        struct ipq *fp = container_of(l, struct ipq, ip_link);
        l = (struct qlink*)l->next;
                if (--fp->ipq_ttl == 0) {
                        ip_freef(slirp, 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, forward = 0;
        struct in_addr *sin, dst;
typedef uint32_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:
        icmp_error(m, type, code, 0, 0);

        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(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;
}