tools/adflib: build only host variant which is used by Sam440 target

[AROS.git] / workbench / network / stacks / AROSTCP / bsdsocket / netinet / ip_output.c

/*
 * Copyright (c) 1982, 1986, 1988, 1990, 1993
 *      The Regents of the University of California.  All rights reserved.
 * Copyright (c) 2005 - 2006 Pavel Fedin
 *
 * 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_output.c 8.3 (Berkeley) 1/21/94
 */
#include <conf.h>

#include <libraries/miami.h>
#include <sys/param.h>
#include <sys/malloc.h>
#include <sys/mbuf.h>
#include <sys/errno.h>
#include <sys/socket.h>
#include <sys/socketvar.h>
#include <sys/protosw.h>
#include <sys/synch.h>
#include <sys/syslog.h>

#include <net/route.h>
#include <net/if.h>
#include <net/if_protos.h>
#include <net/pfil.h>

#include <netinet/in.h>
#include <netinet/in_systm.h>
#include <netinet/ip.h>
#include <netinet/in_pcb.h>
#include <netinet/in_var.h>
#include <netinet/ip_var.h>

#include <kern/amiga_subr.h>

#ifdef vax
#include <machine/mtpr.h>
#endif

#ifndef IP_RAWOUTPUT
#define IP_RAWOUTPUT 0
#endif

static struct mbuf *ip_insertoptions __P((struct mbuf *, struct mbuf *, int *));
#ifdef ENABLE_MULTICAST
static void ip_mloopback
        __P((struct ifnet *, struct mbuf *, struct sockaddr_in *));
#endif

/*
 * IP output.  The packet in mbuf chain m contains a skeletal IP
 * header (with len, off, ttl, proto, tos, src, dst).
 * The mbuf chain containing the packet will be freed.
 * The mbuf opt, if present, will not be freed.
 */
int     STKARGFUN ip_output(void *args, ...)
{
        struct mbuf *m0 = args;
        struct mbuf *opt;
        struct route *ro;
        int flags;
#ifdef ENABLE_MULTICAST
        struct ip_moptions *imo;
#endif
        register struct ip *ip, *mhip;
        register struct ifnet *ifp;
        register struct mbuf *m = m0;
        register int hlen = sizeof (struct ip);
        int len, off, error = 0;
        struct route iproute;
        struct sockaddr_in *dst;
        struct in_ifaddr *ia;
        va_list va;

        va_start(va, args);
        opt = va_arg(va, struct mbuf *);
        ro  = va_arg(va, struct route *);
        flags = va_arg(va, int);
#ifdef ENABLE_MULTICAST
        imo = v_arg(va, struct ip_moptions *);
#endif
        va_end(va);

#ifdef  DIAGNOSTIC
        if ((m->m_flags & M_PKTHDR) == 0)
                panic("ip_output no HDR");
#endif
        if (opt) {
                m = ip_insertoptions(m, opt, &len);
                hlen = len;
        }
        ip = mtod(m, struct ip *);
        /*
         * Fill in IP header.
         */
        if ((flags & (IP_FORWARDING|IP_RAWOUTPUT)) == 0) {
                ip->ip_v = IPVERSION;
                ip->ip_off &= IP_DF;
                ip->ip_id = htons(ip_id++);
                ip->ip_hl = hlen >> 2;
                ipstat.ips_localout++;
        } else {
                hlen = ip->ip_hl << 2;
        }
        /*
         * Route packet.
         */
        if (ro == 0) {
                ro = &iproute;
                bzero((caddr_t)ro, sizeof (*ro));
        }
        dst = (struct sockaddr_in *)&ro->ro_dst;
        /*
         * If there is a cached route,
         * check that it is to the same destination
         * and is still up.  If not, free it and try again.
         */
        if (ro->ro_rt && ((ro->ro_rt->rt_flags & RTF_UP) == 0 ||
           dst->sin_addr.s_addr != ip->ip_dst.s_addr)) {
                RTFREE(ro->ro_rt);
                ro->ro_rt = (struct rtentry *)0;
        }
        if (ro->ro_rt == 0) {
                dst->sin_family = AF_INET;
                dst->sin_len = sizeof(*dst);
                dst->sin_addr = ip->ip_dst;
        }
        /*
         * If routing to interface only,
         * short circuit routing lookup.
         */
#define ifatoia(ifa)    ((struct in_ifaddr *)(ifa))
#define sintosa(sin)    ((struct sockaddr *)(sin))
        if (flags & IP_ROUTETOIF) {
                if ((ia = ifatoia(ifa_ifwithdstaddr(sintosa(dst)))) == 0 &&
                    (ia = ifatoia(ifa_ifwithnet(sintosa(dst)))) == 0) {
                        ipstat.ips_noroute++;
                        error = ENETUNREACH;
                        goto bad;
                }
                ifp = ia->ia_ifp;
                ip->ip_ttl = 1;
        } else {
                if (ro->ro_rt == 0)
                        rtalloc(ro);
                if (ro->ro_rt == 0) {
                        ipstat.ips_noroute++;
                        error = EHOSTUNREACH;
                        DROUTE(log(LOG_DEBUG,"ip_output(): packet dropped\n");)
                        goto bad;
                }
                ia = ifatoia(ro->ro_rt->rt_ifa);
                ifp = ro->ro_rt->rt_ifp;
                ro->ro_rt->rt_use++;
                if (ro->ro_rt->rt_flags & RTF_GATEWAY)
                        dst = (struct sockaddr_in *)ro->ro_rt->rt_gateway;
        }
#ifdef ENABLE_MULTICAST
        if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr))) {
                struct in_multi *inm;
                extern struct ifnet loif;

                m->m_flags |= M_MCAST;
                /*
                 * IP destination address is multicast.  Make sure "dst"
                 * still points to the address in "ro".  (It may have been
                 * changed to point to a gateway address, above.)
                 */
                dst = (struct sockaddr_in *)&ro->ro_dst;
                /*
                 * See if the caller provided any multicast options
                 */
                if (imo != NULL) {
                        ip->ip_ttl = imo->imo_multicast_ttl;
                        if (imo->imo_multicast_ifp != NULL)
                                ifp = imo->imo_multicast_ifp;
                } else
                        ip->ip_ttl = IP_DEFAULT_MULTICAST_TTL;
                /*
                 * Confirm that the outgoing interface supports multicast.
                 */
                if ((ifp->if_flags & IFF_MULTICAST) == 0) {
                        ipstat.ips_noroute++;
                        error = ENETUNREACH;
                        goto bad;
                }
                /*
                 * If source address not specified yet, use address
                 * of outgoing interface.
                 */
                if (ip->ip_src.s_addr == INADDR_ANY) {
                        register struct in_ifaddr *ia;

                        for (ia = in_ifaddr; ia; ia = ia->ia_next)
                                if (ia->ia_ifp == ifp) {
                                        ip->ip_src = IA_SIN(ia)->sin_addr;
                                        break;
                                }
                }

                IN_LOOKUP_MULTI(ip->ip_dst, ifp, inm);
                if (inm != NULL &&
                   (imo == NULL || imo->imo_multicast_loop)) {
                        /*
                         * If we belong to the destination multicast group
                         * on the outgoing interface, and the caller did not
                         * forbid loopback, loop back a copy.
                         */
                        ip_mloopback(ifp, m, dst);
                }
#ifdef MROUTING
                else {
                        /*
                         * If we are acting as a multicast router, perform
                         * multicast forwarding as if the packet had just
                         * arrived on the interface to which we are about
                         * to send.  The multicast forwarding function
                         * recursively calls this function, using the
                         * IP_FORWARDING flag to prevent infinite recursion.
                         *
                         * Multicasts that are looped back by ip_mloopback(),
                         * above, will be forwarded by the ip_input() routine,
                         * if necessary.
                         */
                        extern struct socket *ip_mrouter;
                        if (ip_mrouter && (flags & IP_FORWARDING) == 0) {
                                if (ip_mforward(m, ifp) != 0) {
                                        m_freem(m);
                                        goto done;
                                }
                        }
                }
#endif
                /*
                 * Multicasts with a time-to-live of zero may be looped-
                 * back, above, but must not be transmitted on a network.
                 * Also, multicasts addressed to the loopback interface
                 * are not sent -- the above call to ip_mloopback() will
                 * loop back a copy if this host actually belongs to the
                 * destination group on the loopback interface.
                 */
                if (ip->ip_ttl == 0 || ifp == &loif) {
                        m_freem(m);
                        goto done;
                }

                goto sendit;
        }
#endif
#ifndef notdef
        /*
         * If source address not specified yet, use address
         * of outgoing interface.
         */
        if (ip->ip_src.s_addr == INADDR_ANY)
                ip->ip_src = IA_SIN(ia)->sin_addr;
#endif
        /*
         * Look for broadcast address and
         * and verify user is allowed to send
         * such a packet.
         */
/* TODO: NicJA - Function proto changed?? needs reflected in protos/netinet/in_protos.h */
#if !defined(__AROS__)
        if (in_broadcast(dst->sin_addr, ifp)) {
#else
        if (in_broadcast(dst->sin_addr)) {
#endif
                if ((ifp->if_flags & IFF_BROADCAST) == 0) {
                        error = EADDRNOTAVAIL;
                        goto bad;
                }
                if ((flags & IP_ALLOWBROADCAST) == 0) {
                        error = EACCES;
                        goto bad;
                }
                /* don't allow broadcast messages to be fragmented */
                if ((u_short)ip->ip_len > ifp->if_mtu) {
                        error = EMSGSIZE;
                        goto bad;
                }
                m->m_flags |= M_BCAST;
        } else
                m->m_flags &= ~M_BCAST;

#ifdef ENABLE_MULTICAST
sendit:
#endif
        /* Run through list of hooks */
        pfil_run_hooks(m, ifp, MIAMIPFBPT_IP);

        /*
         * If small enough for interface, can just send directly.
         */
        if ((u_short)ip->ip_len <= ifp->if_mtu) {
                ip->ip_len = htons((u_short)ip->ip_len);
                ip->ip_off = htons((u_short)ip->ip_off);
                ip->ip_sum = 0;
                ip->ip_sum = in_cksum(m, hlen);
                error = (*ifp->if_output)(ifp, m,
                                (struct sockaddr *)dst, ro->ro_rt);
                goto done;
        }
        /*
         * Too large for interface; fragment if possible.
         * Must be able to put at least 8 bytes per fragment.
         */
        if (ip->ip_off & IP_DF) {
                error = EMSGSIZE;
                ipstat.ips_cantfrag++;
                goto bad;
        }
        len = (ifp->if_mtu - hlen) &~ 7;
        if (len < 8) {
                error = EMSGSIZE;
                goto bad;
        }

    {
        int mhlen, firstlen = len;
        struct mbuf **mnext = &m->m_nextpkt;

        /*
         * 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 < (u_short)ip->ip_len; off += len) {
                MGETHDR(m, M_DONTWAIT, MT_HEADER);
                if (m == 0) {
                        error = ENOBUFS;
                        ipstat.ips_odropped++;
                        goto sendorfree;
                }
                m->m_data += max_linkhdr;
                mhip = mtod(m, struct ip *);
                *mhip = *ip;
                if (hlen > sizeof (struct ip)) {
                        mhlen = ip_optcopy(ip, mhip) + sizeof (struct ip);
                        mhip->ip_hl = mhlen >> 2;
                }
                m->m_len = mhlen;
                mhip->ip_off = ((off - hlen) >> 3) + (ip->ip_off & ~IP_MF);
                if (ip->ip_off & IP_MF)
                        mhip->ip_off |= IP_MF;
                if (off + len >= (u_short)ip->ip_len)
                        len = (u_short)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) {
                        (void) m_free(m);
                        error = ENOBUFS;        /* ??? */
                        ipstat.ips_odropped++;
                        goto sendorfree;
                }
                m->m_pkthdr.len = mhlen + len;
                m->m_pkthdr.rcvif = (struct ifnet *)0;
                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_nextpkt;
                ipstat.ips_ofragments++;
        }
        /*
         * Update first fragment by trimming what's been copied out
         * and updating header, then send each fragment (in order).
         */
        m = m0;
        m_adj(m, hlen + firstlen - (u_short)ip->ip_len);
        m->m_pkthdr.len = hlen + firstlen;
        ip->ip_len = htons((u_short)m->m_pkthdr.len);
        ip->ip_off = htons((u_short)(ip->ip_off | IP_MF));
        ip->ip_sum = 0;
        ip->ip_sum = in_cksum(m, hlen);
sendorfree:
        for (m = m0; m; m = m0) {
                m0 = m->m_nextpkt;
                m->m_nextpkt = 0;
                if (error == 0)
                        error = (*ifp->if_output)(ifp, m,
                            (struct sockaddr *)dst, ro->ro_rt);
                else
                        m_freem(m);
        }

        if (error == 0)
                ipstat.ips_fragmented++;
    }
done:
        if (ro == &iproute && (flags & IP_ROUTETOIF) == 0 && ro->ro_rt)
                RTFREE(ro->ro_rt);
        return (error);
bad:
        m_freem(m0);
        goto done;
}

/*
 * Insert IP options into preformed packet.
 * Adjust IP destination as required for IP source routing,
 * as indicated by a non-zero in_addr at the start of the options.
 */
static struct mbuf *
ip_insertoptions(m, opt, phlen)
        register struct mbuf *m;
        struct mbuf *opt;
        int *phlen;
{
        register struct ipoption *p = mtod(opt, struct ipoption *);
        struct mbuf *n;
        register struct ip *ip = mtod(m, struct ip *);
        unsigned optlen;

        optlen = opt->m_len - sizeof(p->ipopt_dst);
        if (optlen + (u_short)ip->ip_len > IP_MAXPACKET)
                return (m);             /* XXX should fail */
        if (p->ipopt_dst.s_addr)
                ip->ip_dst = p->ipopt_dst;
        if (m->m_flags & M_EXT || m->m_data - optlen < m->m_pktdat) {
                MGETHDR(n, M_DONTWAIT, MT_HEADER);
                if (n == 0)
                        return (m);
                n->m_pkthdr.len = m->m_pkthdr.len + optlen;
                m->m_len -= sizeof(struct ip);
                m->m_data += sizeof(struct ip);
                n->m_next = m;
                m = n;
                m->m_len = optlen + sizeof(struct ip);
                m->m_data += max_linkhdr;
                bcopy((caddr_t)ip, mtod(m, caddr_t), sizeof(struct ip));
        } else {
                m->m_data -= optlen;
                m->m_len += optlen;
                m->m_pkthdr.len += optlen;
                ovbcopy((caddr_t)ip, mtod(m, caddr_t), sizeof(struct ip));
        }
        ip = mtod(m, struct ip *);
        bcopy((caddr_t)p->ipopt_list, (caddr_t)(ip + 1), (unsigned)optlen);
        *phlen = sizeof(struct ip) + optlen;
        ip->ip_len += optlen;
        return (m);
}

/*
 * Copy options from ip to jp,
 * omitting those not copied during fragmentation.
 */
int
ip_optcopy(ip, jp)
        struct ip *ip, *jp;
{
        register u_char *cp, *dp;
        int opt, optlen, cnt;

        cp = (u_char *)(ip + 1);
        dp = (u_char *)(jp + 1);
        cnt = (ip->ip_hl << 2) - sizeof (struct ip);
        for (; cnt > 0; cnt -= optlen, cp += optlen) {
                opt = cp[0];
                if (opt == IPOPT_EOL)
                        break;
                if (opt == IPOPT_NOP) {
                        /* Preserve for IP mcast tunnel's LSRR alignment. */
                        *dp++ = IPOPT_NOP;
                        optlen = 1;
                        continue;
                } else
                        optlen = cp[IPOPT_OLEN];
                /* bogus lengths should have been caught by ip_dooptions */
                if (optlen > cnt)
                        optlen = cnt;
                if (IPOPT_COPIED(opt)) {
                        bcopy((caddr_t)cp, (caddr_t)dp, (unsigned)optlen);
                        dp += optlen;
                }
        }
        for (optlen = dp - (u_char *)(jp+1); optlen & 0x3; optlen++)
                *dp++ = IPOPT_EOL;
        return (optlen);
}

/*
 * IP socket option processing.
 */
int
ip_ctloutput(op, so, level, optname, mp)
        int op;
        struct socket *so;
        int level, optname;
        struct mbuf **mp;
{
        register struct inpcb *inp = sotoinpcb(so);
        register struct mbuf *m = *mp;
        register int optval;
        int error = 0;

        if (level != IPPROTO_IP) {
                error = EINVAL;
                if (op == PRCO_SETOPT && *mp)
                        (void) m_free(*mp);
        } else switch (op) {

        case PRCO_SETOPT:
                switch (optname) {
                case IP_OPTIONS:
#ifdef notyet
                case IP_RETOPTS:
                        return (ip_pcbopts(optname, &inp->inp_options, m));
#else
                        return (ip_pcbopts(&inp->inp_options, m));
#endif

                case IP_TOS:
                case IP_TTL:
                case IP_RECVOPTS:
                case IP_RECVRETOPTS:
                case IP_RECVDSTADDR:
                        if (m->m_len != sizeof(int))
                                error = EINVAL;
                        else {
                                optval = *mtod(m, int *);
                                switch (optname) {

                                case IP_TOS:
                                        inp->inp_ip.ip_tos = optval;
                                        break;

                                case IP_TTL:
                                        inp->inp_ip.ip_ttl = optval;
                                        break;
#define OPTSET(bit) \
        if (optval) \
                inp->inp_flags |= bit; \
        else \
                inp->inp_flags &= ~bit;

                                case IP_RECVOPTS:
                                        OPTSET(INP_RECVOPTS);
                                        break;

                                case IP_RECVRETOPTS:
                                        OPTSET(INP_RECVRETOPTS);
                                        break;

                                case IP_RECVDSTADDR:
                                        OPTSET(INP_RECVDSTADDR);
                                        break;
                                }
                        }
                        break;
#undef OPTSET
#ifdef ENABLE_MULTICAST
                case IP_MULTICAST_IF:
                case IP_MULTICAST_TTL:
                case IP_MULTICAST_LOOP:
                case IP_ADD_MEMBERSHIP:
                case IP_DROP_MEMBERSHIP:
                        error = ip_setmoptions(optname, &inp->inp_moptions, m);
                        break;
#endif
                default:
                        error = ENOPROTOOPT;
                        break;
                }
                if (m)
                        (void)m_free(m);
                break;

        case PRCO_GETOPT:
                switch (optname) {
                case IP_OPTIONS:
                case IP_RETOPTS:
                        *mp = m = m_get(M_WAIT, MT_SOOPTS);
                        if (inp->inp_options) {
                                m->m_len = inp->inp_options->m_len;
                                bcopy(mtod(inp->inp_options, caddr_t),
                                    mtod(m, caddr_t), (unsigned)m->m_len);
                        } else
                                m->m_len = 0;
                        break;

                case IP_TOS:
                case IP_TTL:
                case IP_RECVOPTS:
                case IP_RECVRETOPTS:
                case IP_RECVDSTADDR:
                        *mp = m = m_get(M_WAIT, MT_SOOPTS);
                        m->m_len = sizeof(int);
                        switch (optname) {

                        case IP_TOS:
                                optval = inp->inp_ip.ip_tos;
                                break;

                        case IP_TTL:
                                optval = inp->inp_ip.ip_ttl;
                                break;

#define OPTBIT(bit)     (inp->inp_flags & bit ? 1 : 0)

                        case IP_RECVOPTS:
                                optval = OPTBIT(INP_RECVOPTS);
                                break;

                        case IP_RECVRETOPTS:
                                optval = OPTBIT(INP_RECVRETOPTS);
                                break;

                        case IP_RECVDSTADDR:
                                optval = OPTBIT(INP_RECVDSTADDR);
                                break;
                        }
                        *mtod(m, int *) = optval;
                        break;
#ifdef ENABLE_MULTICAST
                case IP_MULTICAST_IF:
                case IP_MULTICAST_TTL:
                case IP_MULTICAST_LOOP:
                case IP_ADD_MEMBERSHIP:
                case IP_DROP_MEMBERSHIP:
                        error = ip_getmoptions(optname, inp->inp_moptions, mp);
                        break;
#endif
                default:
                        error = ENOPROTOOPT;
                        break;
                }
                break;
        }
        return (error);
}

/*
 * Set up IP options in pcb for insertion in output packets.
 * Store in mbuf with pointer in pcbopt, adding pseudo-option
 * with destination address if source routed.
 */
int
#ifdef notyet
ip_pcbopts(optname, pcbopt, m)
        int optname;
#else
ip_pcbopts(pcbopt, m)
#endif
        struct mbuf **pcbopt;
        register struct mbuf *m;
{
        register int cnt, optlen;
        register u_char *cp;
        u_char opt;

        /* turn off any old options */
        if (*pcbopt)
                (void)m_free(*pcbopt);
        *pcbopt = 0;
        if (m == (struct mbuf *)0 || m->m_len == 0) {
                /*
                 * Only turning off any previous options.
                 */
                if (m)
                        (void)m_free(m);
                return (0);
        }

#ifndef vax
        if (m->m_len % sizeof(long))
                goto bad;
#endif
        /*
         * IP first-hop destination address will be stored before
         * actual options; move other options back
         * and clear it when none present.
         */
        if (m->m_data + m->m_len + sizeof(struct in_addr) >= &m->m_dat[MLEN])
                goto bad;
        cnt = m->m_len;
        m->m_len += sizeof(struct in_addr);
        cp = mtod(m, u_char *) + sizeof(struct in_addr);
        ovbcopy(mtod(m, caddr_t), (caddr_t)cp, (unsigned)cnt);
        bzero(mtod(m, caddr_t), sizeof(struct in_addr));

        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 <= IPOPT_OLEN || optlen > cnt)
                                goto bad;
                }
                switch (opt) {

                default:
                        break;

                case IPOPT_LSRR:
                case IPOPT_SSRR:
                        /*
                         * user process specifies route as:
                         *      ->A->B->C->D
                         * D must be our final destination (but we can't
                         * check that since we may not have connected yet).
                         * A is first hop destination, which doesn't appear in
                         * actual IP option, but is stored before the options.
                         */
                        if (optlen < IPOPT_MINOFF - 1 + sizeof(struct in_addr))
                                goto bad;
                        m->m_len -= sizeof(struct in_addr);
                        cnt -= sizeof(struct in_addr);
                        optlen -= sizeof(struct in_addr);
                        cp[IPOPT_OLEN] = optlen;
                        /*
                         * Move first hop before start of options.
                         */
                        bcopy((caddr_t)&cp[IPOPT_OFFSET+1], mtod(m, caddr_t),
                            sizeof(struct in_addr));
                        /*
                         * Then copy rest of options back
                         * to close up the deleted entry.
                         */
                        ovbcopy((caddr_t)(&cp[IPOPT_OFFSET+1] +
                            sizeof(struct in_addr)),
                            (caddr_t)&cp[IPOPT_OFFSET+1],
                            (unsigned)cnt + sizeof(struct in_addr));
                        break;
                }
        }
        if (m->m_len > MAX_IPOPTLEN + sizeof(struct in_addr))
                goto bad;
        *pcbopt = m;
        return (0);

bad:
        (void)m_free(m);
        return (EINVAL);
}

#ifdef ENABLE_MULTICAST
/*
 * Set the IP multicast options in response to user setsockopt().
 */
int
ip_setmoptions(optname, imop, m)
        int optname;
        struct ip_moptions **imop;
        struct mbuf *m;
{
        register int error = 0;
        u_char loop;
        register int i;
        struct in_addr addr;
        register struct ip_mreq *mreq;
        register struct ifnet *ifp;
        register struct ip_moptions *imo = *imop;
        struct route ro;
        register struct sockaddr_in *dst;

        if (imo == NULL) {
                /*
                 * No multicast option buffer attached to the pcb;
                 * allocate one and initialize to default values.
                 */
                imo = (struct ip_moptions*)malloc(sizeof(*imo), M_IPMOPTS,
                    M_WAITOK);

                if (imo == NULL)
                        return (ENOBUFS);
                *imop = imo;
                imo->imo_multicast_ifp = NULL;
                imo->imo_multicast_ttl = IP_DEFAULT_MULTICAST_TTL;
                imo->imo_multicast_loop = IP_DEFAULT_MULTICAST_LOOP;
                imo->imo_num_memberships = 0;
        }

        switch (optname) {

        case IP_MULTICAST_IF:
                /*
                 * Select the interface for outgoing multicast packets.
                 */
                if (m == NULL || m->m_len != sizeof(struct in_addr)) {
                        error = EINVAL;
                        break;
                }
                addr = *(mtod(m, struct in_addr *));
                /*
                 * INADDR_ANY is used to remove a previous selection.
                 * When no interface is selected, a default one is
                 * chosen every time a multicast packet is sent.
                 */
                if (addr.s_addr == INADDR_ANY) {
                        imo->imo_multicast_ifp = NULL;
                        break;
                }
                /*
                 * The selected interface is identified by its local
                 * IP address.  Find the interface and confirm that
                 * it supports multicasting.
                 */
                INADDR_TO_IFP(addr, ifp);
                if (ifp == NULL || (ifp->if_flags & IFF_MULTICAST) == 0) {
                        error = EADDRNOTAVAIL;
                        break;
                }
                imo->imo_multicast_ifp = ifp;
                break;

        case IP_MULTICAST_TTL:
                /*
                 * Set the IP time-to-live for outgoing multicast packets.
                 */
                if (m == NULL || m->m_len != 1) {
                        error = EINVAL;
                        break;
                }
                imo->imo_multicast_ttl = *(mtod(m, u_char *));
                break;

        case IP_MULTICAST_LOOP:
                /*
                 * Set the loopback flag for outgoing multicast packets.
                 * Must be zero or one.
                 */
                if (m == NULL || m->m_len != 1 ||
                   (loop = *(mtod(m, u_char *))) > 1) {
                        error = EINVAL;
                        break;
                }
                imo->imo_multicast_loop = loop;
                break;

        case IP_ADD_MEMBERSHIP:
                /*
                 * Add a multicast group membership.
                 * Group must be a valid IP multicast address.
                 */
                if (m == NULL || m->m_len != sizeof(struct ip_mreq)) {
                        error = EINVAL;
                        break;
                }
                mreq = mtod(m, struct ip_mreq *);
                if (!IN_MULTICAST(ntohl(mreq->imr_multiaddr.s_addr))) {
                        error = EINVAL;
                        break;
                }
                /*
                 * If no interface address was provided, use the interface of
                 * the route to the given multicast address.
                 */
                if (mreq->imr_interface.s_addr == INADDR_ANY) {
                        ro.ro_rt = NULL;
                        dst = (struct sockaddr_in *)&ro.ro_dst;
                        dst->sin_len = sizeof(*dst);
                        dst->sin_family = AF_INET;
                        dst->sin_addr = mreq->imr_multiaddr;
                        rtalloc(&ro);
                        if (ro.ro_rt == NULL) {
                                error = EADDRNOTAVAIL;
                                break;
                        }
                        ifp = ro.ro_rt->rt_ifp;
                        rtfree(ro.ro_rt);
                }
                else {
                        INADDR_TO_IFP(mreq->imr_interface, ifp);
                }
                /*
                 * See if we found an interface, and confirm that it
                 * supports multicast.
                 */
                if (ifp == NULL || (ifp->if_flags & IFF_MULTICAST) == 0) {
                        error = EADDRNOTAVAIL;
                        break;
                }
                /*
                 * See if the membership already exists or if all the
                 * membership slots are full.
                 */
                for (i = 0; i < imo->imo_num_memberships; ++i) {
                        if (imo->imo_membership[i]->inm_ifp == ifp &&
                            imo->imo_membership[i]->inm_addr.s_addr
                                                == mreq->imr_multiaddr.s_addr)
                                break;
                }
                if (i < imo->imo_num_memberships) {
                        error = EADDRINUSE;
                        break;
                }
                if (i == IP_MAX_MEMBERSHIPS) {
                        error = ETOOMANYREFS;
                        break;
                }
                /*
                 * Everything looks good; add a new record to the multicast
                 * address list for the given interface.
                 */
                if ((imo->imo_membership[i] =
                    in_addmulti(&mreq->imr_multiaddr, ifp)) == NULL) {
                        error = ENOBUFS;
                        break;
                }
                ++imo->imo_num_memberships;
                break;

        case IP_DROP_MEMBERSHIP:
                /*
                 * Drop a multicast group membership.
                 * Group must be a valid IP multicast address.
                 */
                if (m == NULL || m->m_len != sizeof(struct ip_mreq)) {
                        error = EINVAL;
                        break;
                }
                mreq = mtod(m, struct ip_mreq *);
                if (!IN_MULTICAST(ntohl(mreq->imr_multiaddr.s_addr))) {
                        error = EINVAL;
                        break;
                }
                /*
                 * If an interface address was specified, get a pointer
                 * to its ifnet structure.
                 */
                if (mreq->imr_interface.s_addr == INADDR_ANY)
                        ifp = NULL;
                else {
                        INADDR_TO_IFP(mreq->imr_interface, ifp);
                        if (ifp == NULL) {
                                error = EADDRNOTAVAIL;
                                break;
                        }
                }
                /*
                 * Find the membership in the membership array.
                 */
                for (i = 0; i < imo->imo_num_memberships; ++i) {
                        if ((ifp == NULL ||
                             imo->imo_membership[i]->inm_ifp == ifp) &&
                             imo->imo_membership[i]->inm_addr.s_addr ==
                             mreq->imr_multiaddr.s_addr)
                                break;
                }
                if (i == imo->imo_num_memberships) {
                        error = EADDRNOTAVAIL;
                        break;
                }
                /*
                 * Give up the multicast address record to which the
                 * membership points.
                 */
                in_delmulti(imo->imo_membership[i]);
                /*
                 * Remove the gap in the membership array.
                 */
                for (++i; i < imo->imo_num_memberships; ++i)
                        imo->imo_membership[i-1] = imo->imo_membership[i];
                --imo->imo_num_memberships;
                break;

        default:
                error = EOPNOTSUPP;
                break;
        }

        /*
         * If all options have default values, no need to keep the mbuf.
         */
        if (imo->imo_multicast_ifp == NULL &&
            imo->imo_multicast_ttl == IP_DEFAULT_MULTICAST_TTL &&
            imo->imo_multicast_loop == IP_DEFAULT_MULTICAST_LOOP &&
            imo->imo_num_memberships == 0) {
                free(*imop, M_IPMOPTS);
                *imop = NULL;
        }

        return (error);
}

/*
 * Return the IP multicast options in response to user getsockopt().
 */
int
ip_getmoptions(optname, imo, mp)
        int optname;
        register struct ip_moptions *imo;
        register struct mbuf **mp;
{
        u_char *ttl;
        u_char *loop;
        struct in_addr *addr;
        struct in_ifaddr *ia;

        *mp = m_get(M_WAIT, MT_SOOPTS);

        switch (optname) {

        case IP_MULTICAST_IF:
                addr = mtod(*mp, struct in_addr *);
                (*mp)->m_len = sizeof(struct in_addr);
                if (imo == NULL || imo->imo_multicast_ifp == NULL)
                        addr->s_addr = INADDR_ANY;
                else {
                        IFP_TO_IA(imo->imo_multicast_ifp, ia);
                        addr->s_addr = (ia == NULL) ? INADDR_ANY
                                        : IA_SIN(ia)->sin_addr.s_addr;
                }
                return (0);

        case IP_MULTICAST_TTL:
                ttl = mtod(*mp, u_char *);
                (*mp)->m_len = 1;
                *ttl = (imo == NULL) ? IP_DEFAULT_MULTICAST_TTL
                                     : imo->imo_multicast_ttl;
                return (0);

        case IP_MULTICAST_LOOP:
                loop = mtod(*mp, u_char *);
                (*mp)->m_len = 1;
                *loop = (imo == NULL) ? IP_DEFAULT_MULTICAST_LOOP
                                      : imo->imo_multicast_loop;
                return (0);

        default:
                return (EOPNOTSUPP);
        }
}

/*
 * Discard the IP multicast options.
 */
void
ip_freemoptions(imo)
        register struct ip_moptions *imo;
{
        register int i;

        if (imo != NULL) {
                for (i = 0; i < imo->imo_num_memberships; ++i)
                        in_delmulti(imo->imo_membership[i]);
                free(imo, M_IPMOPTS);
        }
}

/*
 * Routine called from ip_output() to loop back a copy of an IP multicast
 * packet to the input queue of a specified interface.  Note that this
 * calls the output routine of the loopback "driver", but with an interface
 * pointer that might NOT be &loif -- easier than replicating that code here.
 */
static void
ip_mloopback(ifp, m, dst)
        struct ifnet *ifp;
        register struct mbuf *m;
        register struct sockaddr_in *dst;
{
        register struct ip *ip;
        struct mbuf *copym;

        copym = m_copy(m, 0, M_COPYALL);
        if (copym != NULL) {
                /*
                 * We don't bother to fragment if the IP length is greater
                 * than the interface's MTU.  Can this possibly matter?
                 */
                ip = mtod(copym, struct ip *);
                ip->ip_len = htons((u_short)ip->ip_len);
                ip->ip_off = htons((u_short)ip->ip_off);
                ip->ip_sum = 0;
                ip->ip_sum = in_cksum(copym, ip->ip_hl << 2);
                (void) looutput(ifp, copym, (struct sockaddr *)dst, NULL);
        }
}
#endif