/*      $NetBSD: ip_output.c,v 1.330 2025/07/17 06:48:39 ozaki-r Exp $  */

/*
 * Copyright (C) 1995, 1996, 1997, and 1998 WIDE Project.
 * 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 project 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 PROJECT 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 PROJECT 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.
 */

/*
 * Copyright (c) 1998 The NetBSD Foundation, Inc.
 * All rights reserved.
 *
 * This code is derived from software contributed to The NetBSD Foundation
 * by Public Access Networks Corporation ("Panix").  It was developed under
 * contract to Panix by Eric Haszlakiewicz and Thor Lancelot Simon.
 *
 * 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.
 *
 * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. 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 FOUNDATION 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.
 */

/*
 * Copyright (c) 1982, 1986, 1988, 1990, 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_output.c 8.3 (Berkeley) 1/21/94
 */

#include <sys/cdefs.h>
__KERNEL_RCSID(0, "$NetBSD: ip_output.c,v 1.330 2025/07/17 06:48:39 ozaki-r Exp $");

#ifdef _KERNEL_OPT
#include "opt_inet.h"
#include "opt_ipsec.h"
#include "opt_mrouting.h"
#include "opt_net_mpsafe.h"
#include "opt_mpls.h"
#endif

#include "arp.h"

#include <sys/param.h>
#include <sys/kmem.h>
#include <sys/mbuf.h>
#include <sys/socket.h>
#include <sys/socketvar.h>
#include <sys/kauth.h>
#include <sys/systm.h>
#include <sys/syslog.h>

#include <net/if.h>
#include <net/if_types.h>
#include <net/route.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 <netinet/ip_private.h>
#include <netinet/in_offload.h>
#include <netinet/portalgo.h>
#include <netinet/udp.h>
#include <netinet/udp_var.h>

#ifdef INET6
#include <netinet6/ip6_var.h>
#endif

#ifdef MROUTING
#include <netinet/ip_mroute.h>
#endif

#ifdef IPSEC
#include <netipsec/ipsec.h>
#include <netipsec/key.h>
#endif

#ifdef MPLS
#include <netmpls/mpls.h>
#include <netmpls/mpls_var.h>
#endif

static int ip_pcbopts(struct inpcb *, const struct sockopt *);
static struct mbuf *ip_insertoptions(struct mbuf *, struct mbuf *, int *);
static struct ifnet *ip_multicast_if(struct in_addr *, int *);
static void ip_mloopback(struct ifnet *, struct mbuf *,
    const struct sockaddr_in *);
static int ip_ifaddrvalid(const struct in_ifaddr *);

extern pfil_head_t *inet_pfil_hook;                     /* XXX */

int ip_do_loopback_cksum = 0;

static int
ip_mark_mpls(struct ifnet * const ifp, struct mbuf * const m,
    const struct rtentry *rt)
{
        int error = 0;
#ifdef MPLS
        union mpls_shim msh;

        if (rt == NULL || rt_gettag(rt) == NULL ||
            rt_gettag(rt)->sa_family != AF_MPLS ||
            (m->m_flags & (M_MCAST | M_BCAST)) != 0 ||
            ifp->if_type != IFT_ETHER)
                return 0;

        msh.s_addr = MPLS_GETSADDR(rt);
        if (msh.shim.label != MPLS_LABEL_IMPLNULL) {
                struct m_tag *mtag;
                /*
                 * XXX tentative solution to tell ether_output
                 * it's MPLS. Need some more efficient solution.
                 */
                mtag = m_tag_get(PACKET_TAG_MPLS,
                    sizeof(int) /* dummy */,
                    M_NOWAIT);
                if (mtag == NULL)
                        return ENOMEM;
                m_tag_prepend(m, mtag);
        }
#endif
        return error;
}

/*
 * Send an IP packet to a host.
 */
int
ip_if_output(struct ifnet * const ifp, struct mbuf * const m,
    const struct sockaddr * const dst, const struct rtentry *rt)
{
        int error = 0;

        if (rt != NULL) {
                error = rt_check_reject_route(rt, ifp);
                if (error != 0) {
                        IP_STATINC(IP_STAT_RTREJECT);
                        m_freem(m);
                        return error;
                }
        }

        error = ip_mark_mpls(ifp, m, rt);
        if (error != 0) {
                m_freem(m);
                return error;
        }

        error = if_output_lock(ifp, ifp, m, dst, rt);

        return error;
}

/*
 * 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
ip_output(struct mbuf *m0, struct mbuf *opt, struct route *ro, int flags,
    struct ip_moptions *imo, struct inpcb *inp)
{
        struct rtentry *rt;
        struct ip *ip;
        struct ifnet *ifp, *mifp = NULL;
        struct mbuf *m = m0;
        int len, hlen, error = 0;
        struct route iproute;
        const struct sockaddr_in *dst;
        struct in_ifaddr *ia = NULL;
        int isbroadcast;
        int sw_csum;
        u_long mtu;
        bool natt_frag = false;
        bool rtmtu_nolock;
        union {
                struct sockaddr         sa;
                struct sockaddr_in      sin;
        } udst, usrc;
        struct sockaddr *rdst = &udst.sa;       /* real IP destination, as
                                                 * opposed to the nexthop
                                                 */
        struct psref psref, psref_ia;
        int bound;
        bool bind_need_restore = false;
        const struct sockaddr *sa;
        bool need_ia4_release = false;

        len = 0;

        MCLAIM(m, &ip_tx_mowner);

        KASSERT((m->m_flags & M_PKTHDR) != 0);
        KASSERT((m->m_pkthdr.csum_flags & (M_CSUM_TCPv6|M_CSUM_UDPv6)) == 0);
        KASSERT((m->m_pkthdr.csum_flags & (M_CSUM_TCPv4|M_CSUM_UDPv4)) !=
            (M_CSUM_TCPv4|M_CSUM_UDPv4));
        KASSERT(m->m_len >= sizeof(struct ip));

        hlen = sizeof(struct ip);
        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 = htons(0);
                /* ip->ip_id filled in after we find out source ia */
                ip->ip_hl = hlen >> 2;
                IP_STATINC(IP_STAT_LOCALOUT);
        } else {
                hlen = ip->ip_hl << 2;
        }

        /*
         * Route packet.
         */
        if (ro == NULL) {
                memset(&iproute, 0, sizeof(iproute));
                ro = &iproute;
        }
        sockaddr_in_init(&udst.sin, &ip->ip_dst, 0);
        dst = satocsin(rtcache_getdst(ro));

        /*
         * 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.
         * The address family should also be checked in case of sharing
         * the cache with IPv6.
         */
        if (dst && (dst->sin_family != AF_INET ||
            !in_hosteq(dst->sin_addr, ip->ip_dst)))
                rtcache_free(ro);

        /* XXX must be before rtcache operations */
        bound = curlwp_bind();
        bind_need_restore = true;

        if ((rt = rtcache_validate(ro)) == NULL &&
            (rt = rtcache_update(ro, 1)) == NULL) {
                dst = &udst.sin;
                error = rtcache_setdst(ro, &udst.sa);
                if (error != 0) {
                        IP_STATINC(IP_STAT_ODROPPED);
                        goto bad;
                }
        }

        /*
         * If routing to interface only, short circuit routing lookup.
         */
        if (flags & IP_ROUTETOIF) {
                struct ifaddr *ifa = ifa_ifwithladdr_psref(sintocsa(dst), &psref_ia);
                if (ifa == NULL) {
                        IP_STATINC(IP_STAT_NOROUTE);
                        error = ENETUNREACH;
                        goto bad;
                }
                /* ia is already referenced by psref_ia */
                ia = ifatoia(ifa);
                need_ia4_release = true;

                /* Need a reference to keep ifp after ia4_release(ia). */
                ifp = mifp = if_get_byindex(ia->ia_ifp->if_index, &psref);
                if (__predict_false(ifp == NULL)) {
                        IP_STATINC(IP_STAT_NOROUTE);
                        error = ENETUNREACH;
                        goto bad;
                }
                mtu = ifp->if_mtu;
                ip->ip_ttl = 1;
                isbroadcast = in_broadcast(dst->sin_addr, ifp);
        } else if (((IN_MULTICAST(ip->ip_dst.s_addr) ||
            ip->ip_dst.s_addr == INADDR_BROADCAST) ||
            (flags & IP_ROUTETOIFINDEX)) &&
            imo != NULL && imo->imo_multicast_if_index != 0) {
                ifp = mifp = if_get_byindex(imo->imo_multicast_if_index, &psref);
                if (ifp == NULL) {
                        IP_STATINC(IP_STAT_NOROUTE);
                        error = ENETUNREACH;
                        goto bad;
                }
                mtu = ifp->if_mtu;
                ia = in_get_ia_from_ifp_psref(ifp, &psref_ia);
                need_ia4_release = true;
                if (IN_MULTICAST(ip->ip_dst.s_addr) ||
                    ip->ip_dst.s_addr == INADDR_BROADCAST) {
                        isbroadcast = 0;
                } else {
                        /* IP_ROUTETOIFINDEX */
                        isbroadcast = in_broadcast(dst->sin_addr, ifp);
                        if ((isbroadcast == 0) && ((ifp->if_flags &
                            (IFF_LOOPBACK | IFF_POINTOPOINT)) == 0) &&
                            (in_direct(dst->sin_addr, ifp) == 0)) {
                                /* gateway address required */
                                if (rt == NULL)
                                        rt = rtcache_init(ro);
                                if (rt == NULL || rt->rt_ifp != ifp) {
                                        IP_STATINC(IP_STAT_NOROUTE);
                                        error = EHOSTUNREACH;
                                        goto bad;
                                }
                                rt->rt_use++;
                                if (rt->rt_flags & RTF_GATEWAY)
                                        dst = satosin(rt->rt_gateway);
                                if (rt->rt_flags & RTF_HOST)
                                        isbroadcast =
                                            rt->rt_flags & RTF_BROADCAST;
                        }
                }
        } else {
                if (rt == NULL)
                        rt = rtcache_init(ro);
                if (rt == NULL) {
                        IP_STATINC(IP_STAT_NOROUTE);
                        error = EHOSTUNREACH;
                        goto bad;
                }
                /*
                 * Taking a psref of ifa via rt_ifa is racy, so use it as is, which
                 * is safe because rt_ifa is not freed during rt is held.
                 */
                ia = ifatoia(rt->rt_ifa);
                ifp = rt->rt_ifp;
                if ((mtu = rt->rt_rmx.rmx_mtu) == 0)
                        mtu = ifp->if_mtu;
                rt->rt_use++;
                if (rt->rt_flags & RTF_GATEWAY)
                        dst = satosin(rt->rt_gateway);
                if (rt->rt_flags & RTF_HOST)
                        isbroadcast = rt->rt_flags & RTF_BROADCAST;
                else
                        isbroadcast = in_broadcast(dst->sin_addr, ifp);
        }
        rtmtu_nolock = rt && (rt->rt_rmx.rmx_locks & RTV_MTU) == 0;

        if (IN_MULTICAST(ip->ip_dst.s_addr) ||
            (ip->ip_dst.s_addr == INADDR_BROADCAST)) {
                bool inmgroup;

                m->m_flags |= (ip->ip_dst.s_addr == INADDR_BROADCAST) ?
                    M_BCAST : M_MCAST;
                /*
                 * See if the caller provided any multicast options
                 */
                if (imo != NULL)
                        ip->ip_ttl = imo->imo_multicast_ttl;
                else
                        ip->ip_ttl = IP_DEFAULT_MULTICAST_TTL;

                /*
                 * if we don't know the outgoing ifp yet, we can't generate
                 * output
                 */
                if (!ifp) {
                        IP_STATINC(IP_STAT_NOROUTE);
                        error = ENETUNREACH;
                        goto bad;
                }

                /*
                 * If the packet is multicast or broadcast, confirm that
                 * the outgoing interface can transmit it.
                 */
                if (((m->m_flags & M_MCAST) &&
                     (ifp->if_flags & IFF_MULTICAST) == 0) ||
                    ((m->m_flags & M_BCAST) &&
                     (ifp->if_flags & (IFF_BROADCAST|IFF_POINTOPOINT)) == 0))  {
                        IP_STATINC(IP_STAT_NOROUTE);
                        error = ENETUNREACH;
                        goto bad;
                }
                /*
                 * If source address not specified yet, use an address
                 * of outgoing interface.
                 */
                if (in_nullhost(ip->ip_src)) {
                        struct in_ifaddr *xia;
                        struct ifaddr *ifa;
                        struct psref _psref;

                        xia = in_get_ia_from_ifp_psref(ifp, &_psref);
                        if (!xia) {
                                IP_STATINC(IP_STAT_IFNOADDR);
                                error = EADDRNOTAVAIL;
                                goto bad;
                        }
                        ifa = &xia->ia_ifa;
                        if (ifa->ifa_getifa != NULL) {
                                ia4_release(xia, &_psref);
                                /* FIXME ifa_getifa is NOMPSAFE */
                                xia = ifatoia((*ifa->ifa_getifa)(ifa, rdst));
                                if (xia == NULL) {
                                        IP_STATINC(IP_STAT_IFNOADDR);
                                        error = EADDRNOTAVAIL;
                                        goto bad;
                                }
                                ia4_acquire(xia, &_psref);
                        }
                        ip->ip_src = xia->ia_addr.sin_addr;
                        ia4_release(xia, &_psref);
                }

                inmgroup = in_multi_group(ip->ip_dst, ifp, flags);
                if (inmgroup && (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, &udst.sin);
                }
#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->if_flags & IFF_LOOPBACK) != 0) {
                        IP_STATINC(IP_STAT_ODROPPED);
                        m_freem(m);
                        goto done;
                }
                goto sendit;
        }

        /*
         * If source address not specified yet, use address
         * of outgoing interface.
         */
        if (in_nullhost(ip->ip_src)) {
                struct ifaddr *ifa;

                ifa = &ia->ia_ifa;
                if (ifa->ifa_getifa != NULL) {
                        if (need_ia4_release) {
                                ia4_release(ia, &psref_ia);
                                need_ia4_release = false;
                        }
                        /* FIXME ifa_getifa is NOMPSAFE */
                        ia = ifatoia((*ifa->ifa_getifa)(ifa, rdst));
                        if (ia == NULL) {
                                error = EADDRNOTAVAIL;
                                goto bad;
                        }
                        ia4_acquire(ia, &psref_ia);
                        need_ia4_release = true;
                }
                ip->ip_src = ia->ia_addr.sin_addr;
        }

        /*
         * Packets with Class-D address as source are not valid per
         * RFC1112.
         */
        if (IN_MULTICAST(ip->ip_src.s_addr)) {
                IP_STATINC(IP_STAT_ODROPPED);
                error = EADDRNOTAVAIL;
                goto bad;
        }

        /*
         * Look for broadcast address and verify user is allowed to
         * send such a packet.
         */
        if (isbroadcast) {
                if ((ifp->if_flags & IFF_BROADCAST) == 0) {
                        IP_STATINC(IP_STAT_BCASTDENIED);
                        error = EADDRNOTAVAIL;
                        goto bad;
                }
                if ((flags & IP_ALLOWBROADCAST) == 0) {
                        IP_STATINC(IP_STAT_BCASTDENIED);
                        error = EACCES;
                        goto bad;
                }
                /* don't allow broadcast messages to be fragmented */
                if (ntohs(ip->ip_len) > ifp->if_mtu) {
                        IP_STATINC(IP_STAT_BCASTDENIED);
                        error = EMSGSIZE;
                        goto bad;
                }
                m->m_flags |= M_BCAST;
        } else
                m->m_flags &= ~M_BCAST;

sendit:
        if ((flags & (IP_FORWARDING|IP_NOIPNEWID)) == 0) {
                if (m->m_pkthdr.len < IP_MINFRAGSIZE) {
                        ip->ip_id = 0;
                } else if ((m->m_pkthdr.csum_flags & M_CSUM_TSOv4) == 0) {
                        ip->ip_id = ip_newid();
                } else {
                        /*
                         * TSO capable interfaces (typically?) increment
                         * ip_id for each segment.
                         * "allocate" enough ids here to increase the chance
                         * for them to be unique.
                         *
                         * note that the following calculation is not
                         * needed to be precise.  wasting some ip_id is fine.
                         */

                        unsigned int segsz = m->m_pkthdr.segsz;
                        unsigned int datasz = ntohs(ip->ip_len) - hlen;
                        unsigned int num = howmany(datasz, segsz);

                        ip->ip_id = ip_newid_range(num);
                }
        }
        if (ia != NULL) {
                if (need_ia4_release) {
                        ia4_release(ia, &psref_ia);
                        need_ia4_release = false;
                }
                ia = NULL;
        }

        /*
         * If we're doing Path MTU Discovery, we need to set DF unless
         * the route's MTU is locked.
         */
        if ((flags & IP_MTUDISC) != 0 && rtmtu_nolock) {
                ip->ip_off |= htons(IP_DF);
        }

#ifdef IPSEC
        if (ipsec_used) {
                bool ipsec_done = false;
                bool count_drop = false;

                /* Perform IPsec processing, if any. */
                error = ipsec4_output(m, inp, flags, &mtu, &natt_frag,
                    &ipsec_done, &count_drop);
                if (count_drop)
                        IP_STATINC(IP_STAT_IPSECDROP_OUT);
                if (error || ipsec_done)
                        goto done;
        }

        if (!ipsec_used || !natt_frag)
#endif
        {
                /*
                 * Run through list of hooks for output packets.
                 */
                error = pfil_run_hooks(inet_pfil_hook, &m, ifp, PFIL_OUT);
                if (error || m == NULL) {
                        IP_STATINC(IP_STAT_PFILDROP_OUT);
                        goto done;
                }
        }

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

        m->m_pkthdr.csum_data |= hlen << 16;

        /*
         * search for the source address structure to
         * maintain output statistics, and verify address
         * validity
         */
        KASSERT(ia == NULL);
        sockaddr_in_init(&usrc.sin, &ip->ip_src, 0);
        ia = ifatoia(ifaof_ifpforaddr_psref(&usrc.sa, ifp, &psref_ia));
        if (ia != NULL)
                need_ia4_release = true;

        /*
         * Ensure we only send from a valid address.
         * A NULL address is valid because the packet could be
         * generated from a packet filter.
         */
        if (ia != NULL && (flags & IP_FORWARDING) == 0 &&
            (error = ip_ifaddrvalid(ia)) != 0)
        {
                ARPLOG(LOG_ERR,
                    "refusing to send from invalid address %s (pid %d)\n",
                    ARPLOGADDR(&ip->ip_src), curproc->p_pid);
                IP_STATINC(IP_STAT_ODROPPED);
                if (error == 1)
                        /*
                         * Address exists, but is tentative or detached.
                         * We can't send from it because it's invalid,
                         * so we drop the packet.
                         */
                        error = 0;
                else
                        error = EADDRNOTAVAIL;
                goto bad;
        }

        /* Maybe skip checksums on loopback interfaces. */
        if (IN_NEED_CHECKSUM(ifp, M_CSUM_IPv4)) {
                m->m_pkthdr.csum_flags |= M_CSUM_IPv4;
        }
        sw_csum = m->m_pkthdr.csum_flags & ~ifp->if_csum_flags_tx;

        /* Need to fragment the packet */
        if (ntohs(ip->ip_len) > mtu &&
            (m->m_pkthdr.csum_flags & M_CSUM_TSOv4) == 0) {
                goto fragment;
        }

#if IFA_STATS
        if (ia)
                ia->ia_ifa.ifa_data.ifad_outbytes += ntohs(ip->ip_len);
#endif
        /*
         * Always initialize the sum to 0!  Some HW assisted
         * checksumming requires this.
         */
        ip->ip_sum = 0;

        if ((m->m_pkthdr.csum_flags & M_CSUM_TSOv4) == 0) {
                /*
                 * Perform any checksums that the hardware can't do
                 * for us.
                 *
                 * XXX Does any hardware require the {th,uh}_sum
                 * XXX fields to be 0?
                 */
                if (sw_csum & M_CSUM_IPv4) {
                        KASSERT(IN_NEED_CHECKSUM(ifp, M_CSUM_IPv4));
                        ip->ip_sum = in_cksum(m, hlen);
                        m->m_pkthdr.csum_flags &= ~M_CSUM_IPv4;
                }
                if (sw_csum & (M_CSUM_TCPv4|M_CSUM_UDPv4)) {
                        if (IN_NEED_CHECKSUM(ifp,
                            sw_csum & (M_CSUM_TCPv4|M_CSUM_UDPv4))) {
                                in_undefer_cksum_tcpudp(m);
                        }
                        m->m_pkthdr.csum_flags &=
                            ~(M_CSUM_TCPv4|M_CSUM_UDPv4);
                }
        }

        sa = (m->m_flags & M_MCAST) ? sintocsa(rdst) : sintocsa(dst);

        /* Send it */
        if (__predict_false(sw_csum & M_CSUM_TSOv4)) {
                /*
                 * TSO4 is required by a packet, but disabled for
                 * the interface.
                 */
                error = ip_tso_output(ifp, m, sa, rt);
        } else
                error = ip_if_output(ifp, m, sa, rt);
        goto done;

fragment:
        /*
         * We can't use HW checksumming if we're about to fragment the packet.
         *
         * XXX Some hardware can do this.
         */
        if (m->m_pkthdr.csum_flags & (M_CSUM_TCPv4|M_CSUM_UDPv4)) {
                if (IN_NEED_CHECKSUM(ifp,
                    m->m_pkthdr.csum_flags & (M_CSUM_TCPv4|M_CSUM_UDPv4))) {
                        in_undefer_cksum_tcpudp(m);
                }
                m->m_pkthdr.csum_flags &= ~(M_CSUM_TCPv4|M_CSUM_UDPv4);
        }

        /*
         * Too large for interface; fragment if possible.
         * Must be able to put at least 8 bytes per fragment.
         */
        if (ntohs(ip->ip_off) & IP_DF) {
                if (flags & IP_RETURNMTU) {
                        KASSERT(inp != NULL);
                        in4p_errormtu(inp) = mtu;
                }
                error = EMSGSIZE;
                IP_STATINC(IP_STAT_CANTFRAG);
                goto bad;
        }

        error = ip_fragment(m, ifp, mtu);
        if (error) {
                m = NULL;
                goto bad;
        }

        for (; m; m = m0) {
                m0 = m->m_nextpkt;
                m->m_nextpkt = NULL;
                if (error) {
                        m_freem(m);
                        continue;
                }
#if IFA_STATS
                if (ia)
                        ia->ia_ifa.ifa_data.ifad_outbytes += ntohs(ip->ip_len);
#endif
                /*
                 * If we get there, the packet has not been handled by
                 * IPsec whereas it should have. Now that it has been
                 * fragmented, re-inject it in ip_output so that IPsec
                 * processing can occur.
                 */
                if (natt_frag) {
                        error = ip_output(m, opt, NULL,
                            flags | IP_RAWOUTPUT | IP_NOIPNEWID,
                            imo, inp);
                } else {
                        KASSERT((m->m_pkthdr.csum_flags &
                            (M_CSUM_UDPv4 | M_CSUM_TCPv4)) == 0);
                        error = ip_if_output(ifp, m, (m->m_flags & M_MCAST) ?
                            sintocsa(rdst) : sintocsa(dst), rt);
                }
        }
        if (error == 0) {
                IP_STATINC(IP_STAT_FRAGMENTED);
        }

done:
        if (need_ia4_release)
                ia4_release(ia, &psref_ia);
        rtcache_unref(rt, ro);
        if (ro == &iproute) {
                rtcache_free(&iproute);
        }
        if (mifp != NULL) {
                if_put(mifp, &psref);
        }
        if (bind_need_restore)
                curlwp_bindx(bound);
        return error;

bad:
        m_freem(m);
        goto done;
}

int
ip_fragment(struct mbuf *m, struct ifnet *ifp, u_long mtu)
{
        struct ip *ip, *mhip;
        struct mbuf *m0;
        int len, hlen, off;
        int mhlen, firstlen;
        struct mbuf **mnext;
        int sw_csum = m->m_pkthdr.csum_flags;
        int fragments = 0;
        int error = 0;
        int ipoff, ipflg;

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

        /* Preserve the offset and flags. */
        ipoff = ntohs(ip->ip_off) & IP_OFFMASK;
        ipflg = ntohs(ip->ip_off) & (IP_RF|IP_DF|IP_MF);

        if (ifp != NULL)
                sw_csum &= ~ifp->if_csum_flags_tx;

        len = (mtu - hlen) &~ 7;
        if (len < 8) {
                IP_STATINC(IP_STAT_CANTFRAG);
                m_freem(m);
                return EMSGSIZE;
        }

        firstlen = len;
        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 < ntohs(ip->ip_len); off += len) {
                MGETHDR(m, M_DONTWAIT, MT_HEADER);
                if (m == NULL) {
                        error = ENOBUFS;
                        IP_STATINC(IP_STAT_ODROPPED);
                        goto sendorfree;
                }
                MCLAIM(m, m0->m_owner);

                *mnext = m;
                mnext = &m->m_nextpkt;

                m->m_data += max_linkhdr;
                mhip = mtod(m, struct ip *);
                *mhip = *ip;

                /* we must inherit the flags */
                m->m_flags |= m0->m_flags & M_COPYFLAGS;

                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) + ipoff;
                mhip->ip_off |= ipflg;
                if (off + len >= ntohs(ip->ip_len))
                        len = ntohs(ip->ip_len) - off;
                else
                        mhip->ip_off |= IP_MF;
                HTONS(mhip->ip_off);

                mhip->ip_len = htons((u_int16_t)(len + mhlen));
                m->m_next = m_copym(m0, off, len, M_DONTWAIT);
                if (m->m_next == NULL) {
                        error = ENOBUFS;
                        IP_STATINC(IP_STAT_ODROPPED);
                        goto sendorfree;
                }

                m->m_pkthdr.len = mhlen + len;
                m_reset_rcvif(m);

                mhip->ip_sum = 0;
                KASSERT((m->m_pkthdr.csum_flags & M_CSUM_IPv4) == 0);
                if (sw_csum & M_CSUM_IPv4) {
                        mhip->ip_sum = in_cksum(m, mhlen);
                } else {
                        /*
                         * checksum is hw-offloaded or not necessary.
                         */
                        m->m_pkthdr.csum_flags |=
                            m0->m_pkthdr.csum_flags & M_CSUM_IPv4;
                        m->m_pkthdr.csum_data |= mhlen << 16;
                        KASSERT(!(ifp != NULL &&
                            IN_NEED_CHECKSUM(ifp, M_CSUM_IPv4)) ||
                            (m->m_pkthdr.csum_flags & M_CSUM_IPv4) != 0);
                }
                IP_STATINC(IP_STAT_OFRAGMENTS);
                fragments++;
        }

        /*
         * 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 - ntohs(ip->ip_len));
        m->m_pkthdr.len = hlen + firstlen;
        ip->ip_len = htons((u_int16_t)m->m_pkthdr.len);
        ip->ip_off |= htons(IP_MF);
        ip->ip_sum = 0;
        if (sw_csum & M_CSUM_IPv4) {
                ip->ip_sum = in_cksum(m, hlen);
                m->m_pkthdr.csum_flags &= ~M_CSUM_IPv4;
        } else {
                /*
                 * checksum is hw-offloaded or not necessary.
                 */
                KASSERT(!(ifp != NULL && IN_NEED_CHECKSUM(ifp, M_CSUM_IPv4)) ||
                    (m->m_pkthdr.csum_flags & M_CSUM_IPv4) != 0);
                KASSERT(M_CSUM_DATA_IPv4_IPHL(m->m_pkthdr.csum_data) >=
                    sizeof(struct ip));
        }

sendorfree:
        /*
         * If there is no room for all the fragments, don't queue
         * any of them.
         */
        if (ifp != NULL) {
                IFQ_LOCK(&ifp->if_snd);
                if (ifp->if_snd.ifq_maxlen - ifp->if_snd.ifq_len < fragments &&
                    error == 0) {
                        error = ENOBUFS;
                        IP_STATINC(IP_STAT_ODROPPED);
                        IFQ_INC_DROPS(&ifp->if_snd);
                }
                IFQ_UNLOCK(&ifp->if_snd);
        }
        if (error) {
                for (m = m0; m; m = m0) {
                        m0 = m->m_nextpkt;
                        m->m_nextpkt = NULL;
                        m_freem(m);
                }
        }

        return error;
}

/*
 * Determine the maximum length of the options to be inserted;
 * we would far rather allocate too much space rather than too little.
 */
u_int
ip_optlen(struct inpcb *inp)
{
        struct mbuf *m = inp->inp_options;

        if (m && m->m_len > offsetof(struct ipoption, ipopt_dst)) {
                return (m->m_len - offsetof(struct ipoption, ipopt_dst));
        }
        return 0;
}

/*
 * 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(struct mbuf *m, struct mbuf *opt, int *phlen)
{
        struct ipoption *p = mtod(opt, struct ipoption *);
        struct mbuf *n;
        struct ip *ip = mtod(m, struct ip *);
        unsigned optlen;

        optlen = opt->m_len - sizeof(p->ipopt_dst);
        KASSERT(optlen % 4 == 0);
        if (optlen + ntohs(ip->ip_len) > IP_MAXPACKET)
                return m;               /* XXX should fail */
        if (!in_nullhost(p->ipopt_dst))
                ip->ip_dst = p->ipopt_dst;
        if (M_READONLY(m) || M_LEADINGSPACE(m) < optlen) {
                MGETHDR(n, M_DONTWAIT, MT_HEADER);
                if (n == NULL)
                        return m;
                MCLAIM(n, m->m_owner);
                m_move_pkthdr(n, m);
                m->m_len -= sizeof(struct ip);
                m->m_data += sizeof(struct ip);
                n->m_next = m;
                n->m_len = optlen + sizeof(struct ip);
                n->m_data += max_linkhdr;
                memcpy(mtod(n, void *), ip, sizeof(struct ip));
                m = n;
        } else {
                m->m_data -= optlen;
                m->m_len += optlen;
                memmove(mtod(m, void *), ip, sizeof(struct ip));
        }
        m->m_pkthdr.len += optlen;
        ip = mtod(m, struct ip *);
        memcpy(ip + 1, p->ipopt_list, optlen);
        *phlen = sizeof(struct ip) + optlen;
        ip->ip_len = htons(ntohs(ip->ip_len) + optlen);
        return m;
}

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

        cp = (u_char *)(ipsrc + 1);
        dp = (u_char *)(ipdst + 1);
        cnt = (ipsrc->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;
                }

                KASSERT(cnt >= IPOPT_OLEN + sizeof(*cp));
                optlen = cp[IPOPT_OLEN];
                KASSERT(optlen >= IPOPT_OLEN + sizeof(*cp) && optlen < cnt);

                /* Invalid lengths should have been caught by ip_dooptions. */
                if (optlen > cnt)
                        optlen = cnt;
                if (IPOPT_COPIED(opt)) {
                        bcopy((void *)cp, (void *)dp, (unsigned)optlen);
                        dp += optlen;
                }
        }

        for (optlen = dp - (u_char *)(ipdst+1); optlen & 0x3; optlen++) {
                *dp++ = IPOPT_EOL;
        }

        return optlen;
}

/*
 * IP socket option processing.
 */
int
ip_ctloutput(int op, struct socket *so, struct sockopt *sopt)
{
        struct inpcb *inp = sotoinpcb(so);
        struct ip *ip = &in4p_ip(inp);
        int inpflags = inp->inp_flags;
        int optval = 0, error = 0;
        struct in_pktinfo pktinfo;

        KASSERT(solocked(so));

        if (sopt->sopt_level != IPPROTO_IP) {
                if (sopt->sopt_level == SOL_SOCKET && sopt->sopt_name == SO_NOHEADER)
                        return 0;
                return ENOPROTOOPT;
        }

        switch (op) {
        case PRCO_SETOPT:
                switch (sopt->sopt_name) {
                case IP_OPTIONS:
#ifdef notyet
                case IP_RETOPTS:
#endif
                        error = ip_pcbopts(inp, sopt);
                        break;

                case IP_TOS:
                case IP_TTL:
                case IP_MINTTL:
                case IP_RECVOPTS:
                case IP_RECVRETOPTS:
                case IP_RECVDSTADDR:
                case IP_RECVIF:
                case IP_RECVPKTINFO:
                case IP_RECVTTL:
                case IP_BINDANY:
                        error = sockopt_getint(sopt, &optval);
                        if (error)
                                break;

                        switch (sopt->sopt_name) {
                        case IP_TOS:
                                ip->ip_tos = optval;
                                break;

                        case IP_TTL:
                                ip->ip_ttl = optval;
                                break;

                        case IP_MINTTL:
                                if (optval > 0 && optval <= MAXTTL)
                                        in4p_ip_minttl(inp) = optval;
                                else
                                        error = EINVAL;
                                break;
#define OPTSET(bit) \
        if (optval) \
                inpflags |= bit; \
        else \
                inpflags &= ~bit;

                        case IP_RECVOPTS:
                                OPTSET(INP_RECVOPTS);
                                break;

                        case IP_RECVPKTINFO:
                                OPTSET(INP_RECVPKTINFO);
                                break;

                        case IP_RECVRETOPTS:
                                OPTSET(INP_RECVRETOPTS);
                                break;

                        case IP_RECVDSTADDR:
                                OPTSET(INP_RECVDSTADDR);
                                break;

                        case IP_RECVIF:
                                OPTSET(INP_RECVIF);
                                break;

                        case IP_RECVTTL:
                                OPTSET(INP_RECVTTL);
                                break;

                        case IP_BINDANY:
                                error = kauth_authorize_network(
                                    kauth_cred_get(), KAUTH_NETWORK_BIND,
                                    KAUTH_REQ_NETWORK_BIND_ANYADDR, so,
                                    NULL, NULL);
                                if (error == 0) {
                                        OPTSET(INP_BINDANY);
                                }
                                break;
                        }
                        break;
                case IP_PKTINFO:
                        error = sockopt_getint(sopt, &optval);
                        if (!error) {
                                /* Linux compatibility */
                                OPTSET(INP_RECVPKTINFO);
                                break;
                        }
                        error = sockopt_get(sopt, &pktinfo, sizeof(pktinfo));
                        if (error)
                                break;

                        if (pktinfo.ipi_ifindex == 0) {
                                in4p_prefsrcip(inp) = pktinfo.ipi_addr;
                                break;
                        }

                        /* Solaris compatibility */
                        struct ifnet *ifp;
                        struct in_ifaddr *ia;
                        int s;

                        /* pick up primary address */
                        s = pserialize_read_enter();
                        ifp = if_byindex(pktinfo.ipi_ifindex);
                        if (ifp == NULL) {
                                pserialize_read_exit(s);
                                error = EADDRNOTAVAIL;
                                break;
                        }
                        ia = in_get_ia_from_ifp(ifp);
                        if (ia == NULL) {
                                pserialize_read_exit(s);
                                error = EADDRNOTAVAIL;
                                break;
                        }
                        in4p_prefsrcip(inp) = IA_SIN(ia)->sin_addr;
                        pserialize_read_exit(s);
                        break;
                break;
#undef OPTSET

                case IP_MULTICAST_IF:
                case IP_MULTICAST_TTL:
                case IP_MULTICAST_LOOP:
                case IP_ADD_MEMBERSHIP:
                case IP_DROP_MEMBERSHIP:
                        error = ip_setmoptions(&inp->inp_moptions, sopt);
                        break;

                case IP_PORTRANGE:
                        error = sockopt_getint(sopt, &optval);
                        if (error)
                                break;

                        switch (optval) {
                        case IP_PORTRANGE_DEFAULT:
                        case IP_PORTRANGE_HIGH:
                                inpflags &= ~(INP_LOWPORT);
                                break;

                        case IP_PORTRANGE_LOW:
                                inpflags |= INP_LOWPORT;
                                break;

                        default:
                                error = EINVAL;
                                break;
                        }
                        break;

                case IP_PORTALGO:
                        error = sockopt_getint(sopt, &optval);
                        if (error)
                                break;

                        error = portalgo_algo_index_select(inp, optval);
                        break;

#if defined(IPSEC)
                case IP_IPSEC_POLICY:
                        if (ipsec_enabled) {
                                error = ipsec_set_policy(inp,
                                    sopt->sopt_data, sopt->sopt_size,
                                    curlwp->l_cred);
                        } else 
                                error = ENOPROTOOPT;
                        break;
#endif /* IPSEC */

                default:
                        error = ENOPROTOOPT;
                        break;
                }
                break;

        case PRCO_GETOPT:
                switch (sopt->sopt_name) {
                case IP_OPTIONS:
                case IP_RETOPTS: {
                        struct mbuf *mopts = inp->inp_options;

                        if (mopts) {
                                struct mbuf *m;

                                m = m_copym(mopts, 0, M_COPYALL, M_DONTWAIT);
                                if (m == NULL) {
                                        error = ENOBUFS;
                                        break;
                                }
                                error = sockopt_setmbuf(sopt, m);
                        }
                        break;
                }
                case IP_TOS:
                case IP_TTL:
                case IP_MINTTL:
                case IP_RECVOPTS:
                case IP_RECVRETOPTS:
                case IP_RECVDSTADDR:
                case IP_RECVIF:
                case IP_RECVPKTINFO:
                case IP_RECVTTL:
                case IP_ERRORMTU:
                case IP_BINDANY:
                        switch (sopt->sopt_name) {
                        case IP_TOS:
                                optval = ip->ip_tos;
                                break;

                        case IP_TTL:
                                optval = ip->ip_ttl;
                                break;

                        case IP_MINTTL:
                                optval = in4p_ip_minttl(inp);
                                break;

                        case IP_ERRORMTU:
                                optval = in4p_errormtu(inp);
                                break;

#define OPTBIT(bit)     (inpflags & bit ? 1 : 0)

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

                        case IP_RECVPKTINFO:
                                optval = OPTBIT(INP_RECVPKTINFO);
                                break;

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

                        case IP_RECVDSTADDR:
                                optval = OPTBIT(INP_RECVDSTADDR);
                                break;

                        case IP_RECVIF:
                                optval = OPTBIT(INP_RECVIF);
                                break;

                        case IP_RECVTTL:
                                optval = OPTBIT(INP_RECVTTL);
                                break;

                        case IP_BINDANY:
                                optval = OPTBIT(INP_BINDANY);
                                break;
                        }
                        error = sockopt_setint(sopt, optval);
                        break;

                case IP_PKTINFO:
                        switch (sopt->sopt_size) {
                        case sizeof(int):
                                /* Linux compatibility */
                                optval = OPTBIT(INP_RECVPKTINFO);
                                error = sockopt_setint(sopt, optval);
                                break;
                        case sizeof(struct in_pktinfo):
                                /* Solaris compatibility */
                                pktinfo.ipi_ifindex = 0;
                                pktinfo.ipi_addr = in4p_prefsrcip(inp);
                                error = sockopt_set(sopt, &pktinfo,
                                    sizeof(pktinfo));
                                break;
                        default:
                                /*
                                 * While size is stuck at 0, and, later, if
                                 * the caller doesn't use an exactly sized
                                 * recipient for the data, default to Linux
                                 * compatibility
                                 */
                                optval = OPTBIT(INP_RECVPKTINFO);
                                error = sockopt_setint(sopt, optval);
                                break;
                        }
                        break;

#if 0   /* defined(IPSEC) */
                case IP_IPSEC_POLICY:
                {
                        struct mbuf *m = NULL;

                        /* XXX this will return EINVAL as sopt is empty */
                        error = ipsec_get_policy(inp, sopt->sopt_data,
                            sopt->sopt_size, &m);
                        if (error == 0)
                                error = sockopt_setmbuf(sopt, m);
                        break;
                }
#endif /*IPSEC*/

                case IP_MULTICAST_IF:
                case IP_MULTICAST_TTL:
                case IP_MULTICAST_LOOP:
                case IP_ADD_MEMBERSHIP:
                case IP_DROP_MEMBERSHIP:
                        error = ip_getmoptions(inp->inp_moptions, sopt);
                        break;

                case IP_PORTRANGE:
                        if (inpflags & INP_LOWPORT)
                                optval = IP_PORTRANGE_LOW;
                        else
                                optval = IP_PORTRANGE_DEFAULT;
                        error = sockopt_setint(sopt, optval);
                        break;

                case IP_PORTALGO:
                        optval = inp->inp_portalgo;
                        error = sockopt_setint(sopt, optval);
                        break;

                default:
                        error = ENOPROTOOPT;
                        break;
                }
                break;
        }

        if (!error) {
                inp->inp_flags = inpflags;
        }
        return error;
}

static int
ip_pktinfo_prepare(const struct inpcb *inp, const struct in_pktinfo *pktinfo,
    struct ip_pktopts *pktopts, int *flags, kauth_cred_t cred)
{
        struct ip_moptions *imo;
        int error = 0;
        bool addrset = false;

        if (!in_nullhost(pktinfo->ipi_addr)) {
                pktopts->ippo_laddr.sin_addr = pktinfo->ipi_addr;
                /* EADDRNOTAVAIL? */
                error = inpcb_bindableaddr(inp, &pktopts->ippo_laddr, cred);
                if (error != 0)
                        return error;
                addrset = true;
        }

        if (pktinfo->ipi_ifindex != 0) {
                if (!addrset) {
                        struct ifnet *ifp;
                        struct in_ifaddr *ia;
                        int s;

                        /* pick up primary address */
                        s = pserialize_read_enter();
                        ifp = if_byindex(pktinfo->ipi_ifindex);
                        if (ifp == NULL) {
                                pserialize_read_exit(s);
                                return EADDRNOTAVAIL;
                        }
                        ia = in_get_ia_from_ifp(ifp);
                        if (ia == NULL) {
                                pserialize_read_exit(s);
                                return EADDRNOTAVAIL;
                        }
                        pktopts->ippo_laddr.sin_addr = IA_SIN(ia)->sin_addr;
                        pserialize_read_exit(s);
                }

                /*
                 * If specified ipi_ifindex,
                 * use copied or locally initialized ip_moptions.
                 * Original ip_moptions must not be modified.
                 */
                imo = &pktopts->ippo_imobuf;    /* local buf in pktopts */
                if (pktopts->ippo_imo != NULL) {
                        memcpy(imo, pktopts->ippo_imo, sizeof(*imo));
                } else {
                        memset(imo, 0, sizeof(*imo));
                        imo->imo_multicast_ttl = IP_DEFAULT_MULTICAST_TTL;
                        imo->imo_multicast_loop = IP_DEFAULT_MULTICAST_LOOP;
                }
                imo->imo_multicast_if_index = pktinfo->ipi_ifindex;
                pktopts->ippo_imo = imo;
                *flags |= IP_ROUTETOIFINDEX;
        }
        return error;
}

/*
 * Set up IP outgoing packet options. Even if control is NULL,
 * pktopts->ippo_laddr and pktopts->ippo_imo are set and used.
 */
int
ip_setpktopts(struct mbuf *control, struct ip_pktopts *pktopts, int *flags,
    struct inpcb *inp, kauth_cred_t cred)
{
        struct cmsghdr *cm;
        struct in_pktinfo pktinfo;
        int error;

        pktopts->ippo_imo = inp->inp_moptions;

        struct in_addr *ia = in_nullhost(in4p_prefsrcip(inp)) ? &in4p_laddr(inp) :
            &in4p_prefsrcip(inp);
        sockaddr_in_init(&pktopts->ippo_laddr, ia, 0);

        if (control == NULL)
                return 0;

        /*
         * XXX: Currently, we assume all the optional information is
         * stored in a single mbuf.
         */
        if (control->m_next)
                return EINVAL;

        for (; control->m_len > 0;
            control->m_data += CMSG_ALIGN(cm->cmsg_len),
            control->m_len -= CMSG_ALIGN(cm->cmsg_len)) {
                cm = mtod(control, struct cmsghdr *);
                if ((control->m_len < sizeof(*cm)) ||
                    (cm->cmsg_len == 0) ||
                    (cm->cmsg_len > control->m_len)) {
                        return EINVAL;
                }
                if (cm->cmsg_level != IPPROTO_IP)
                        continue;

                switch (cm->cmsg_type) {
                case IP_PKTINFO:
                        if (cm->cmsg_len != CMSG_LEN(sizeof(pktinfo)))
                                return EINVAL;
                        memcpy(&pktinfo, CMSG_DATA(cm), sizeof(pktinfo));
                        error = ip_pktinfo_prepare(inp, &pktinfo, pktopts,
                            flags, cred);
                        if (error)
                                return error;
                        break;
                case IP_SENDSRCADDR: /* FreeBSD compatibility */
                        if (cm->cmsg_len != CMSG_LEN(sizeof(struct in_addr)))
                                return EINVAL;
                        pktinfo.ipi_ifindex = 0;
                        pktinfo.ipi_addr =
                            ((struct in_pktinfo *)CMSG_DATA(cm))->ipi_addr;
                        error = ip_pktinfo_prepare(inp, &pktinfo, pktopts,
                            flags, cred);
                        if (error)
                                return error;
                        break;
                default:
                        return ENOPROTOOPT;
                }
        }
        return 0;
}

/*
 * 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.
 */
static int
ip_pcbopts(struct inpcb *inp, const struct sockopt *sopt)
{
        struct mbuf *m;
        const u_char *cp;
        u_char *dp;
        int cnt;

        KASSERT(inp_locked(inp));

        /* Turn off any old options. */
        if (inp->inp_options) {
                m_free(inp->inp_options);
        }
        inp->inp_options = NULL;
        if ((cnt = sopt->sopt_size) == 0) {
                /* Only turning off any previous options. */
                return 0;
        }
        cp = sopt->sopt_data;

        if (cnt % 4) {
                /* Must be 4-byte aligned, because there's no padding. */
                return EINVAL;
        }

        m = m_get(M_DONTWAIT, MT_SOOPTS);
        if (m == NULL)
                return ENOBUFS;

        dp = mtod(m, u_char *);
        memset(dp, 0, sizeof(struct in_addr));
        dp += sizeof(struct in_addr);
        m->m_len = sizeof(struct in_addr);

        /*
         * IP option list according to RFC791. Each option is of the form
         *
         *      [optval] [olen] [(olen - 2) data bytes]
         *
         * We validate the list and copy options to an mbuf for prepending
         * to data packets. The IP first-hop destination address will be
         * stored before actual options and is zero if unset.
         */
        while (cnt > 0) {
                uint8_t optval, olen, offset;

                optval = cp[IPOPT_OPTVAL];

                if (optval == IPOPT_EOL || optval == IPOPT_NOP) {
                        olen = 1;
                } else {
                        if (cnt < IPOPT_OLEN + 1)
                                goto bad;

                        olen = cp[IPOPT_OLEN];
                        if (olen < IPOPT_OLEN + 1 || olen > cnt)
                                goto bad;
                }

                if (optval == IPOPT_LSRR || optval == 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 (olen < IPOPT_OFFSET + 1 + sizeof(struct in_addr))
                                goto bad;

                        offset = cp[IPOPT_OFFSET];
                        memcpy(mtod(m, u_char *), cp + IPOPT_OFFSET + 1,
                            sizeof(struct in_addr));

                        cp += sizeof(struct in_addr);
                        cnt -= sizeof(struct in_addr);
                        olen -= sizeof(struct in_addr);

                        if (m->m_len + olen > MAX_IPOPTLEN + sizeof(struct in_addr))
                                goto bad;

                        memcpy(dp, cp, olen);
                        dp[IPOPT_OPTVAL] = optval;
                        dp[IPOPT_OLEN] = olen;
                        dp[IPOPT_OFFSET] = offset;
                        break;
                } else {
                        if (m->m_len + olen > MAX_IPOPTLEN + sizeof(struct in_addr))
                                goto bad;

                        memcpy(dp, cp, olen);
                        break;
                }

                dp += olen;
                m->m_len += olen;

                if (optval == IPOPT_EOL)
                        break;

                cp += olen;
                cnt -= olen;
        }

        inp->inp_options = m;
        return 0;

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

/*
 * following RFC1724 section 3.3, 0.0.0.0/8 is interpreted as interface index.
 * Must be called in a pserialize critical section.
 */
static struct ifnet *
ip_multicast_if(struct in_addr *a, int *ifindexp)
{
        int ifindex;
        struct ifnet *ifp = NULL;
        struct in_ifaddr *ia;

        if (ifindexp)
                *ifindexp = 0;
        if (ntohl(a->s_addr) >> 24 == 0) {
                ifindex = ntohl(a->s_addr) & 0xffffff;
                ifp = if_byindex(ifindex);
                if (!ifp)
                        return NULL;
                if (ifindexp)
                        *ifindexp = ifindex;
        } else {
                IN_ADDRHASH_READER_FOREACH(ia, a->s_addr) {
                        if (in_hosteq(ia->ia_addr.sin_addr, *a) &&
                            (ia->ia_ifp->if_flags & IFF_MULTICAST) != 0) {
                                ifp = ia->ia_ifp;
                                if (if_is_deactivated(ifp))
                                        ifp = NULL;
                                break;
                        }
                }
        }
        return ifp;
}

static int
ip_getoptval(const struct sockopt *sopt, u_int8_t *val, u_int maxval)
{
        u_int tval;
        u_char cval;
        int error;

        if (sopt == NULL)
                return EINVAL;

        switch (sopt->sopt_size) {
        case sizeof(u_char):
                error = sockopt_get(sopt, &cval, sizeof(u_char));
                tval = cval;
                break;

        case sizeof(u_int):
                error = sockopt_get(sopt, &tval, sizeof(u_int));
                break;

        default:
                error = EINVAL;
        }

        if (error)
                return error;

        if (tval > maxval)
                return EINVAL;

        *val = tval;
        return 0;
}

static int
ip_get_membership(const struct sockopt *sopt, struct ifnet **ifp,
    struct psref *psref, struct in_addr *ia, bool add)
{
        int error;
        struct ip_mreq mreq;

        error = sockopt_get(sopt, &mreq, sizeof(mreq));
        if (error)
                return error;

        if (!IN_MULTICAST(mreq.imr_multiaddr.s_addr))
                return EINVAL;

        memcpy(ia, &mreq.imr_multiaddr, sizeof(*ia));

        if (in_nullhost(mreq.imr_interface)) {
                union {
                        struct sockaddr         dst;
                        struct sockaddr_in      dst4;
                } u;
                struct route ro;

                if (!add) {
                        *ifp = NULL;
                        return 0;
                }
                /*
                 * If no interface address was provided, use the interface of
                 * the route to the given multicast address.
                 */
                struct rtentry *rt;
                memset(&ro, 0, sizeof(ro));

                sockaddr_in_init(&u.dst4, ia, 0);
                error = rtcache_setdst(&ro, &u.dst);
                if (error != 0)
                        return error;
                *ifp = (rt = rtcache_init(&ro)) != NULL ? rt->rt_ifp : NULL;
                if (*ifp != NULL) {
                        if (if_is_deactivated(*ifp))
                                *ifp = NULL;
                        else
                                if_acquire(*ifp, psref);
                }
                rtcache_unref(rt, &ro);
                rtcache_free(&ro);
        } else {
                int s = pserialize_read_enter();
                *ifp = ip_multicast_if(&mreq.imr_interface, NULL);
                if (!add && *ifp == NULL) {
                        pserialize_read_exit(s);
                        return EADDRNOTAVAIL;
                }
                if (*ifp != NULL) {
                        if (if_is_deactivated(*ifp))
                                *ifp = NULL;
                        else
                                if_acquire(*ifp, psref);
                }
                pserialize_read_exit(s);
        }
        return 0;
}

/*
 * Add a multicast group membership.
 * Group must be a valid IP multicast address.
 */
static int
ip_add_membership(struct ip_moptions *imo, const struct sockopt *sopt)
{
        struct ifnet *ifp = NULL;       // XXX: gcc [ppc]
        struct in_addr ia;
        int i, error, bound;
        struct psref psref;

        /* imo is protected by solock or referenced only by the caller */

        bound = curlwp_bind();
        if (sopt->sopt_size == sizeof(struct ip_mreq))
                error = ip_get_membership(sopt, &ifp, &psref, &ia, true);
        else {
#ifdef INET6
                error = ip6_get_membership(sopt, &ifp, &psref, &ia, sizeof(ia));
#else
                error = EINVAL;
#endif
        }

        if (error)
                goto out;

        /*
         * See if we found an interface, and confirm that it
         * supports multicast.
         */
        if (ifp == NULL || (ifp->if_flags & IFF_MULTICAST) == 0) {
                error = EADDRNOTAVAIL;
                goto out;
        }

        /*
         * 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 &&
                    in_hosteq(imo->imo_membership[i]->inm_addr, ia))
                        break;
        }
        if (i < imo->imo_num_memberships) {
                error = EADDRINUSE;
                goto out;
        }

        if (i == IP_MAX_MEMBERSHIPS) {
                error = ETOOMANYREFS;
                goto out;
        }

        /*
         * Everything looks good; add a new record to the multicast
         * address list for the given interface.
         */
        imo->imo_membership[i] = in_addmulti(&ia, ifp);
        if (imo->imo_membership[i] == NULL) {
                error = ENOBUFS;
                goto out;
        }

        ++imo->imo_num_memberships;
        error = 0;
out:
        if_put(ifp, &psref);
        curlwp_bindx(bound);
        return error;
}

/*
 * Drop a multicast group membership.
 * Group must be a valid IP multicast address.
 */
static int
ip_drop_membership(struct ip_moptions *imo, const struct sockopt *sopt)
{
        struct in_addr ia = { .s_addr = 0 };    // XXX: gcc [ppc]
        struct ifnet *ifp = NULL;               // XXX: gcc [ppc]
        int i, error, bound;
        struct psref psref;

        /* imo is protected by solock or referenced only by the caller */

        bound = curlwp_bind();
        if (sopt->sopt_size == sizeof(struct ip_mreq))
                error = ip_get_membership(sopt, &ifp, &psref, &ia, false);
        else {
#ifdef INET6
                error = ip6_get_membership(sopt, &ifp, &psref, &ia, sizeof(ia));
#else
                error = EINVAL;
#endif
        }

        if (error)
                goto out;

        /*
         * 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) &&
                    in_hosteq(imo->imo_membership[i]->inm_addr, ia))
                        break;
        }
        if (i == imo->imo_num_memberships) {
                error = EADDRNOTAVAIL;
                goto out;
        }

        /*
         * 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;
        error = 0;
out:
        if_put(ifp, &psref);
        curlwp_bindx(bound);
        return error;
}

/*
 * Set the IP multicast options in response to user setsockopt().
 */
int
ip_setmoptions(struct ip_moptions **pimo, const struct sockopt *sopt)
{
        struct ip_moptions *imo = *pimo;
        struct in_addr addr;
        struct ifnet *ifp;
        int ifindex, error = 0;

        /* The passed imo isn't NULL, it should be protected by solock */

        if (!imo) {
                /*
                 * No multicast option buffer attached to the pcb;
                 * allocate one and initialize to default values.
                 */
                imo = kmem_intr_alloc(sizeof(*imo), KM_NOSLEEP);
                if (imo == NULL)
                        return ENOBUFS;

                imo->imo_multicast_if_index = 0;
                imo->imo_multicast_addr.s_addr = INADDR_ANY;
                imo->imo_multicast_ttl = IP_DEFAULT_MULTICAST_TTL;
                imo->imo_multicast_loop = IP_DEFAULT_MULTICAST_LOOP;
                imo->imo_num_memberships = 0;
                *pimo = imo;
        }

        switch (sopt->sopt_name) {
        case IP_MULTICAST_IF: {
                int s;
                /*
                 * Select the interface for outgoing multicast packets.
                 */
                error = sockopt_get(sopt, &addr, sizeof(addr));
                if (error)
                        break;

                /*
                 * 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 (in_nullhost(addr)) {
                        imo->imo_multicast_if_index = 0;
                        break;
                }
                /*
                 * The selected interface is identified by its local
                 * IP address.  Find the interface and confirm that
                 * it supports multicasting.
                 */
                s = pserialize_read_enter();
                ifp = ip_multicast_if(&addr, &ifindex);
                if (ifp == NULL || (ifp->if_flags & IFF_MULTICAST) == 0) {
                        pserialize_read_exit(s);
                        error = EADDRNOTAVAIL;
                        break;
                }
                imo->imo_multicast_if_index = ifp->if_index;
                pserialize_read_exit(s);
                if (ifindex)
                        imo->imo_multicast_addr = addr;
                else
                        imo->imo_multicast_addr.s_addr = INADDR_ANY;
                break;
            }

        case IP_MULTICAST_TTL:
                /*
                 * Set the IP time-to-live for outgoing multicast packets.
                 */
                error = ip_getoptval(sopt, &imo->imo_multicast_ttl, MAXTTL);
                break;

        case IP_MULTICAST_LOOP:
                /*
                 * Set the loopback flag for outgoing multicast packets.
                 * Must be zero or one.
                 */
                error = ip_getoptval(sopt, &imo->imo_multicast_loop, 1);
                break;

        case IP_ADD_MEMBERSHIP: /* IPV6_JOIN_GROUP */
                error = ip_add_membership(imo, sopt);
                break;

        case IP_DROP_MEMBERSHIP: /* IPV6_LEAVE_GROUP */
                error = ip_drop_membership(imo, sopt);
                break;

        default:
                error = EOPNOTSUPP;
                break;
        }

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

        return error;
}

/*
 * Return the IP multicast options in response to user getsockopt().
 */
int
ip_getmoptions(struct ip_moptions *imo, struct sockopt *sopt)
{
        struct in_addr addr;
        uint8_t optval;
        int error = 0;

        /* imo is protected by solock or referenced only by the caller */

        switch (sopt->sopt_name) {
        case IP_MULTICAST_IF:
                if (imo == NULL || imo->imo_multicast_if_index == 0)
                        addr = zeroin_addr;
                else if (imo->imo_multicast_addr.s_addr) {
                        /* return the value user has set */
                        addr = imo->imo_multicast_addr;
                } else {
                        struct ifnet *ifp;
                        struct in_ifaddr *ia = NULL;
                        int s = pserialize_read_enter();

                        ifp = if_byindex(imo->imo_multicast_if_index);
                        if (ifp != NULL) {
                                ia = in_get_ia_from_ifp(ifp);
                        }
                        addr = ia ? ia->ia_addr.sin_addr : zeroin_addr;
                        pserialize_read_exit(s);
                }
                error = sockopt_set(sopt, &addr, sizeof(addr));
                break;

        case IP_MULTICAST_TTL:
                optval = imo ? imo->imo_multicast_ttl
                    : IP_DEFAULT_MULTICAST_TTL;

                error = sockopt_set(sopt, &optval, sizeof(optval));
                break;

        case IP_MULTICAST_LOOP:
                optval = imo ? imo->imo_multicast_loop
                    : IP_DEFAULT_MULTICAST_LOOP;

                error = sockopt_set(sopt, &optval, sizeof(optval));
                break;

        default:
                error = EOPNOTSUPP;
        }

        return error;
}

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

        /* The owner of imo (inp) should be protected by solock */

        if (imo != NULL) {
                for (i = 0; i < imo->imo_num_memberships; ++i) {
                        struct in_multi *inm = imo->imo_membership[i];
                        in_delmulti(inm);
                        /* ifp should not leave thanks to solock */
                }

                kmem_intr_free(imo, sizeof(*imo));
        }
}

/*
 * 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 lo0ifp -- easier than replicating that code here.
 */
static void
ip_mloopback(struct ifnet *ifp, struct mbuf *m, const struct sockaddr_in *dst)
{
        struct ip *ip;
        struct mbuf *copym;

        copym = m_copypacket(m, M_DONTWAIT);
        if (copym != NULL &&
            (copym->m_flags & M_EXT || copym->m_len < sizeof(struct ip)))
                copym = m_pullup(copym, sizeof(struct ip));
        if (copym == NULL)
                return;
        /*
         * 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 *);

        if (copym->m_pkthdr.csum_flags & (M_CSUM_TCPv4|M_CSUM_UDPv4)) {
                in_undefer_cksum_tcpudp(copym);
                copym->m_pkthdr.csum_flags &=
                    ~(M_CSUM_TCPv4|M_CSUM_UDPv4);
        }

        ip->ip_sum = 0;
        ip->ip_sum = in_cksum(copym, ip->ip_hl << 2);
        KERNEL_LOCK_UNLESS_NET_MPSAFE();
        (void)looutput(ifp, copym, sintocsa(dst), NULL);
        KERNEL_UNLOCK_UNLESS_NET_MPSAFE();
}

/*
 * Ensure sending address is valid.
 * Returns 0 on success, -1 if an error should be sent back or 1
 * if the packet could be dropped without error (protocol dependent).
 */
static int
ip_ifaddrvalid(const struct in_ifaddr *ia)
{

        if (ia->ia_addr.sin_addr.s_addr == INADDR_ANY)
                return 0;

        if (ia->ia4_flags & IN_IFF_DUPLICATED)
                return -1;
        else if (ia->ia4_flags & (IN_IFF_TENTATIVE | IN_IFF_DETACHED))
                return 1;

        return 0;
}