xnu-3248.60.10.tar.gz

[apple/xnu.git] / bsd / net / if_stf.c

/*
 * Copyright (c) 2000-2013 Apple Inc. All rights reserved.
 *
 * @APPLE_OSREFERENCE_LICENSE_HEADER_START@
 * 
 * This file contains Original Code and/or Modifications of Original Code
 * as defined in and that are subject to the Apple Public Source License
 * Version 2.0 (the 'License'). You may not use this file except in
 * compliance with the License. The rights granted to you under the License
 * may not be used to create, or enable the creation or redistribution of,
 * unlawful or unlicensed copies of an Apple operating system, or to
 * circumvent, violate, or enable the circumvention or violation of, any
 * terms of an Apple operating system software license agreement.
 * 
 * Please obtain a copy of the License at
 * http://www.opensource.apple.com/apsl/ and read it before using this file.
 * 
 * The Original Code and all software distributed under the License are
 * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
 * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
 * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
 * Please see the License for the specific language governing rights and
 * limitations under the License.
 * 
 * @APPLE_OSREFERENCE_LICENSE_HEADER_END@
 */

/*      $FreeBSD: src/sys/net/if_stf.c,v 1.1.2.6 2001/07/24 19:10:18 brooks Exp $       */
/*      $KAME: if_stf.c,v 1.62 2001/06/07 22:32:16 itojun Exp $ */

/*
 * Copyright (C) 2000 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.
 */
/*
 * NOTICE: This file was modified by SPARTA, Inc. in 2006 to introduce
 * support for mandatory and extensible security protections.  This notice
 * is included in support of clause 2.2 (b) of the Apple Public License,
 * Version 2.0.
 */

/*
 * 6to4 interface, based on RFC3056.
 *
 * 6to4 interface is NOT capable of link-layer (I mean, IPv4) multicasting.
 * There is no address mapping defined from IPv6 multicast address to IPv4
 * address.  Therefore, we do not have IFF_MULTICAST on the interface.
 *
 * Due to the lack of address mapping for link-local addresses, we cannot
 * throw packets toward link-local addresses (fe80::x).  Also, we cannot throw
 * packets to link-local multicast addresses (ff02::x).
 *
 * Here are interesting symptoms due to the lack of link-local address:
 *
 * Unicast routing exchange:
 * - RIPng: Impossible.  Uses link-local multicast packet toward ff02::9,
 *   and link-local addresses as nexthop.
 * - OSPFv6: Impossible.  OSPFv6 assumes that there's link-local address
 *   assigned to the link, and makes use of them.  Also, HELLO packets use
 *   link-local multicast addresses (ff02::5 and ff02::6).
 * - BGP4+: Maybe.  You can only use global address as nexthop, and global
 *   address as TCP endpoint address.
 *
 * Multicast routing protocols:
 * - PIM: Hello packet cannot be used to discover adjacent PIM routers.
 *   Adjacent PIM routers must be configured manually (is it really spec-wise
 *   correct thing to do?).
 *
 * ICMPv6:
 * - Redirects cannot be used due to the lack of link-local address.
 *
 * stf interface does not have, and will not need, a link-local address.  
 * It seems to have no real benefit and does not help the above symptoms much.
 * Even if we assign link-locals to interface, we cannot really
 * use link-local unicast/multicast on top of 6to4 cloud (since there's no
 * encapsulation defined for link-local address), and the above analysis does
 * not change.  RFC3056 does not mandate the assignment of link-local address
 * either.
 *
 * 6to4 interface has security issues.  Refer to
 * http://playground.iijlab.net/i-d/draft-itojun-ipv6-transition-abuse-00.txt
 * for details.  The code tries to filter out some of malicious packets.
 * Note that there is no way to be 100% secure.
 */

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/socket.h>
#include <sys/sockio.h>
#include <sys/mbuf.h>
#include <sys/errno.h>
#include <sys/protosw.h>
#include <sys/kernel.h>
#include <sys/syslog.h>

#include <sys/malloc.h>

#include <kern/locks.h>

#include <net/if.h>
#include <net/route.h>
#include <net/if_types.h>

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

#include <netinet/ip6.h>
#include <netinet6/ip6_var.h>
#include <netinet6/in6_var.h>
#include <netinet/ip_ecn.h>

#include <netinet/ip_encap.h>
#include <net/kpi_interface.h>
#include <net/kpi_protocol.h>


#include <net/net_osdep.h>

#include <net/bpf.h>

#if CONFIG_MACF_NET
#include <security/mac_framework.h>
#endif

#define GET_V4(x) ((const struct in_addr *)(const void *)(&(x)->s6_addr16[1])) 

static lck_grp_t *stf_mtx_grp;

struct stf_softc {
        ifnet_t                         sc_if;     /* common area */
        u_int32_t                               sc_protocol_family; /* dlil protocol attached */
        union {
                struct route  __sc_ro4;
                struct route_in6 __sc_ro6; /* just for safety */
        } __sc_ro46;
#define sc_ro   __sc_ro46.__sc_ro4
        decl_lck_mtx_data(, sc_ro_mtx);
        const struct encaptab *encap_cookie;
        bpf_tap_mode            tap_mode;
        bpf_packet_func         tap_callback;
};

void stfattach (void);

static int ip_stf_ttl = 40;
static int stf_init_done;

static void in_stf_input(struct mbuf *, int);
static void stfinit(void);

static struct protosw in_stf_protosw =
{
        .pr_type =              SOCK_RAW,
        .pr_protocol =          IPPROTO_IPV6,
        .pr_flags =             PR_ATOMIC|PR_ADDR,
        .pr_input =             in_stf_input,
        .pr_ctloutput =         rip_ctloutput,
        .pr_usrreqs =           &rip_usrreqs,
        .pr_unlock =            rip_unlock,
};

static int stf_encapcheck(const struct mbuf *, int, int, void *);
static struct in6_ifaddr *stf_getsrcifa6(struct ifnet *);
int stf_pre_output(struct ifnet *, protocol_family_t, struct mbuf **,
        const struct sockaddr *, void *, char *, char *);
static int stf_checkaddr4(struct stf_softc *, const struct in_addr *,
        struct ifnet *);
static int stf_checkaddr6(struct stf_softc *, struct in6_addr *,
        struct ifnet *);
static void stf_rtrequest(int, struct rtentry *, struct sockaddr *);
static errno_t stf_ioctl(ifnet_t ifp, u_long cmd, void *data);
static errno_t stf_output(ifnet_t ifp, mbuf_t m);

static void
stfinit(void)
{
        if (!stf_init_done) {
                stf_mtx_grp = lck_grp_alloc_init("stf", LCK_GRP_ATTR_NULL);
                stf_init_done = 1;
        }
}

/*
 * gif_input is the input handler for IP and IPv6 attached to gif
 */
static errno_t
stf_media_input(
        __unused ifnet_t        ifp,
        protocol_family_t       protocol_family,
        mbuf_t                          m,
        __unused char           *frame_header)
{
        if (proto_input(protocol_family, m) != 0)
                m_freem(m);

        return (0);
}



static errno_t
stf_add_proto(
        ifnet_t                                                                 ifp,
        protocol_family_t                                               protocol_family,
        __unused const struct ifnet_demux_desc  *demux_array,
        __unused u_int32_t                                              demux_count)
{
        /* Only one protocol may be attached at a time */
        struct stf_softc* stf = ifnet_softc(ifp);
        if (stf->sc_protocol_family == 0)
                stf->sc_protocol_family = protocol_family;
        else {
                printf("stf_add_proto: stf already has a proto\n");
                return EBUSY;
        }
        
        return 0;
}

static errno_t
stf_del_proto(
        ifnet_t                         ifp,
        protocol_family_t       protocol_family)
{
        if (((struct stf_softc*)ifnet_softc(ifp))->sc_protocol_family == protocol_family)
                ((struct stf_softc*)ifnet_softc(ifp))->sc_protocol_family = 0;
        
        return 0;
}

static errno_t
stf_attach_inet6(
        ifnet_t                         ifp,
        protocol_family_t       protocol_family)
{
    struct ifnet_attach_proto_param     reg;
    errno_t                                                     stat;
    
    if (protocol_family != PF_INET6)
        return EPROTONOSUPPORT;

        bzero(&reg, sizeof(reg));
    reg.input = stf_media_input;
    reg.pre_output = stf_pre_output;

    stat = ifnet_attach_protocol(ifp, protocol_family, &reg);
    if (stat && stat != EEXIST) {
        printf("stf_attach_proto_family can't attach interface fam=%d\n",
                   protocol_family);
    }

    return stat;
}

static errno_t
stf_demux(
        ifnet_t                                 ifp,
        __unused mbuf_t                 m,
        __unused char                   *frame_ptr,
        protocol_family_t               *protocol_family)
{
        struct stf_softc* stf = ifnet_softc(ifp);
        *protocol_family = stf->sc_protocol_family;
        return 0;
}

static errno_t
stf_set_bpf_tap(
        ifnet_t                 ifp,
        bpf_tap_mode    mode,
        bpf_packet_func callback)
{
        struct stf_softc        *sc = ifnet_softc(ifp);
        
        sc->tap_mode = mode;
        sc->tap_callback = callback;
        
        return 0;
}

void
stfattach(void)
{
        struct stf_softc *sc;
        int error;
        const struct encaptab *p;
        struct ifnet_init_params        stf_init;

        stfinit();

        error = proto_register_plumber(PF_INET6, APPLE_IF_FAM_STF,
                                                                   stf_attach_inet6, NULL);
        if (error != 0)
                printf("proto_register_plumber failed for AF_INET6 error=%d\n", error);

        sc = _MALLOC(sizeof(struct stf_softc), M_DEVBUF, M_WAITOK | M_ZERO);
        if (sc == 0) {
                printf("stf softc attach failed\n" );
                return;
        }
        
        p = encap_attach_func(AF_INET, IPPROTO_IPV6, stf_encapcheck,
            &in_stf_protosw, sc);
        if (p == NULL) {
                printf("sftattach encap_attach_func failed\n");
                FREE(sc, M_DEVBUF);
                return;
        }
        sc->encap_cookie = p;
        lck_mtx_init(&sc->sc_ro_mtx, stf_mtx_grp, LCK_ATTR_NULL);
        
        bzero(&stf_init, sizeof(stf_init));
        stf_init.name = "stf";
        stf_init.unit = 0;
        stf_init.type = IFT_STF;
        stf_init.family = IFNET_FAMILY_STF;
        stf_init.output = stf_output;
        stf_init.demux = stf_demux;
        stf_init.add_proto = stf_add_proto;
        stf_init.del_proto = stf_del_proto;
        stf_init.softc = sc;
        stf_init.ioctl = stf_ioctl;
        stf_init.set_bpf_tap = stf_set_bpf_tap;
        
        error = ifnet_allocate(&stf_init, &sc->sc_if);
        if (error != 0) {
                printf("stfattach, ifnet_allocate failed - %d\n", error);
                encap_detach(sc->encap_cookie);
                lck_mtx_destroy(&sc->sc_ro_mtx, stf_mtx_grp);
                FREE(sc, M_DEVBUF);
                return;
        }
        ifnet_set_mtu(sc->sc_if, IPV6_MMTU);
        ifnet_set_flags(sc->sc_if, 0, 0xffff); /* clear all flags */
#if 0
        /* turn off ingress filter */
        ifnet_set_flags(sc->sc_if, IFF_LINK2, IFF_LINK2);
#endif

#if CONFIG_MACF_NET
        mac_ifnet_label_init(&sc->sc_if);
#endif
        
        error = ifnet_attach(sc->sc_if, NULL);
        if (error != 0) {
                printf("stfattach: ifnet_attach returned error=%d\n", error);
                encap_detach(sc->encap_cookie);
                ifnet_release(sc->sc_if);
                lck_mtx_destroy(&sc->sc_ro_mtx, stf_mtx_grp);
                FREE(sc, M_DEVBUF);
                return;
        }
        
        bpfattach(sc->sc_if, DLT_NULL, sizeof(u_int));
        
        return;
}

static int
stf_encapcheck(
        const struct mbuf *m,
        __unused int off,
        int proto,
        void *arg)
{
        struct ip ip;
        struct in6_ifaddr *ia6;
        struct stf_softc *sc;
        struct in_addr a, b;

        sc = (struct stf_softc *)arg;
        if (sc == NULL)
                return 0;

        if ((ifnet_flags(sc->sc_if) & IFF_UP) == 0)
                return 0;

        /* IFF_LINK0 means "no decapsulation" */
        if ((ifnet_flags(sc->sc_if) & IFF_LINK0) != 0)
                return 0;

        if (proto != IPPROTO_IPV6)
                return 0;

        mbuf_copydata((struct mbuf *)(size_t)m, 0, sizeof(ip), &ip);

        if (ip.ip_v != 4)
                return 0;

        ia6 = stf_getsrcifa6(sc->sc_if);
        if (ia6 == NULL)
                return 0;

        /*
         * check if IPv4 dst matches the IPv4 address derived from the
         * local 6to4 address.
         * success on: dst = 10.1.1.1, ia6->ia_addr = 2002:0a01:0101:...
         */
        IFA_LOCK(&ia6->ia_ifa);
        if (bcmp(GET_V4(&ia6->ia_addr.sin6_addr), &ip.ip_dst,
            sizeof(ip.ip_dst)) != 0) {
                IFA_UNLOCK(&ia6->ia_ifa);
                IFA_REMREF(&ia6->ia_ifa);
                return 0;
        }
        /*
         * check if IPv4 src matches the IPv4 address derived from the
         * local 6to4 address masked by prefixmask.
         * success on: src = 10.1.1.1, ia6->ia_addr = 2002:0a00:.../24
         * fail on: src = 10.1.1.1, ia6->ia_addr = 2002:0b00:.../24
         */
        bzero(&a, sizeof(a));
        a.s_addr = GET_V4(&ia6->ia_addr.sin6_addr)->s_addr;
        a.s_addr &= GET_V4(&ia6->ia_prefixmask.sin6_addr)->s_addr;
        b = ip.ip_src;
        b.s_addr &= GET_V4(&ia6->ia_prefixmask.sin6_addr)->s_addr;
        if (a.s_addr != b.s_addr) {
                IFA_UNLOCK(&ia6->ia_ifa);
                IFA_REMREF(&ia6->ia_ifa);
                return 0;
        }
        /* stf interface makes single side match only */
        IFA_UNLOCK(&ia6->ia_ifa);
        IFA_REMREF(&ia6->ia_ifa);
        return 32;
}

static struct in6_ifaddr *
stf_getsrcifa6(struct ifnet *ifp)
{
        struct ifaddr *ia;
        struct in_ifaddr *ia4;
        struct sockaddr_in6 *sin6;
        struct in_addr in;

        ifnet_lock_shared(ifp);
        for (ia = ifp->if_addrlist.tqh_first; ia; ia = ia->ifa_list.tqe_next) {
                IFA_LOCK(ia);
                if (ia->ifa_addr == NULL) {
                        IFA_UNLOCK(ia);
                        continue;
                }
                if (ia->ifa_addr->sa_family != AF_INET6) {
                        IFA_UNLOCK(ia);
                        continue;
                }
                sin6 = (struct sockaddr_in6 *)(void *)ia->ifa_addr;
                if (!IN6_IS_ADDR_6TO4(&sin6->sin6_addr)) {
                        IFA_UNLOCK(ia);
                        continue;
                }
                bcopy(GET_V4(&sin6->sin6_addr), &in, sizeof(in));
                IFA_UNLOCK(ia);
                lck_rw_lock_shared(in_ifaddr_rwlock);
                for (ia4 = TAILQ_FIRST(&in_ifaddrhead);
                     ia4;
                     ia4 = TAILQ_NEXT(ia4, ia_link))
                {
                        IFA_LOCK(&ia4->ia_ifa);
                        if (ia4->ia_addr.sin_addr.s_addr == in.s_addr) {
                                IFA_UNLOCK(&ia4->ia_ifa);
                                break;
                        }
                        IFA_UNLOCK(&ia4->ia_ifa);
                }
                lck_rw_done(in_ifaddr_rwlock);
                if (ia4 == NULL)
                        continue;

                IFA_ADDREF(ia);         /* for caller */
                ifnet_lock_done(ifp);
                return ((struct in6_ifaddr *)ia);
        }
        ifnet_lock_done(ifp);

        return (NULL);
}

int
stf_pre_output(
        struct ifnet    *ifp,
        __unused protocol_family_t  protocol_family,
        struct mbuf     **m0,
        const struct sockaddr   *dst,
        __unused void *route,
        __unused char *desk_linkaddr,
        __unused char *frame_type)
{
        struct mbuf *m = *m0;
        struct stf_softc *sc;
        const struct sockaddr_in6 *dst6;
        const struct in_addr *in4;
        u_int8_t tos;
        struct ip *ip;
        struct ip6_hdr *ip6;
        struct in6_ifaddr *ia6;
        struct sockaddr_in      *dst4;
        struct ip_out_args ipoa =
            { IFSCOPE_NONE, { 0 }, IPOAF_SELECT_SRCIF, 0 };
        errno_t                         result = 0;

        sc = ifnet_softc(ifp);
        dst6 = (const struct sockaddr_in6 *)(const void *)dst;

        /* just in case */
        if ((ifnet_flags(ifp) & IFF_UP) == 0) {
                printf("stf: IFF_DOWN\n");
                return ENETDOWN;
        }

        /*
         * If we don't have an ip4 address that match my inner ip6 address,
         * we shouldn't generate output.  Without this check, we'll end up
         * using wrong IPv4 source.
         */
        ia6 = stf_getsrcifa6(ifp);
        if (ia6 == NULL) {
                return ENETDOWN;
        }

        if (mbuf_len(m) < sizeof(*ip6)) {
                m = m_pullup(m, sizeof(*ip6));
                if (!m) {
                        *m0 = NULL; /* makes sure this won't be double freed */
                        IFA_REMREF(&ia6->ia_ifa);
                        return ENOBUFS;
                }
        }
        ip6 = mtod(m, struct ip6_hdr *);
        tos = (ntohl(ip6->ip6_flow) >> 20) & 0xff;

        /*
         * Pickup the right outer dst addr from the list of candidates.
         * ip6_dst has priority as it may be able to give us shorter IPv4 hops.
         */
        if (IN6_IS_ADDR_6TO4(&ip6->ip6_dst))
                in4 = GET_V4(&ip6->ip6_dst);
        else if (IN6_IS_ADDR_6TO4(&dst6->sin6_addr))
                in4 = GET_V4(&dst6->sin6_addr);
        else {
                IFA_REMREF(&ia6->ia_ifa);
                return ENETUNREACH;
        }

        if (ifp->if_bpf) {
                /* We need to prepend the address family as a four byte field. */
                u_int32_t af = AF_INET6;
                
                bpf_tap_out(ifp, 0, m, &af, sizeof(af));
        }

        M_PREPEND(m, sizeof(struct ip), M_DONTWAIT, 1);
        if (m && mbuf_len(m) < sizeof(struct ip))
                m = m_pullup(m, sizeof(struct ip));
        if (m == NULL) {
                *m0 = NULL; 
                IFA_REMREF(&ia6->ia_ifa);
                return ENOBUFS;
        }
        ip = mtod(m, struct ip *);

        bzero(ip, sizeof(*ip));

        IFA_LOCK_SPIN(&ia6->ia_ifa);
        bcopy(GET_V4(&((struct sockaddr_in6 *)&ia6->ia_addr)->sin6_addr),
            &ip->ip_src, sizeof(ip->ip_src));
        IFA_UNLOCK(&ia6->ia_ifa);
        bcopy(in4, &ip->ip_dst, sizeof(ip->ip_dst));
        ip->ip_p = IPPROTO_IPV6;
        ip->ip_ttl = ip_stf_ttl;
        ip->ip_len = m->m_pkthdr.len;   /*host order*/
        if (ifp->if_flags & IFF_LINK1)
                ip_ecn_ingress(ECN_NORMAL, &ip->ip_tos, &tos);
        else
                ip_ecn_ingress(ECN_NOCARE, &ip->ip_tos, &tos);

        lck_mtx_lock(&sc->sc_ro_mtx);
        dst4 = (struct sockaddr_in *)(void *)&sc->sc_ro.ro_dst;
        if (ROUTE_UNUSABLE(&sc->sc_ro) || dst4->sin_family != AF_INET ||
            bcmp(&dst4->sin_addr, &ip->ip_dst, sizeof(ip->ip_dst)) != 0) {
                ROUTE_RELEASE(&sc->sc_ro);
                /* cache route doesn't match: always the case during the first use */
                dst4->sin_family = AF_INET;
                dst4->sin_len = sizeof(struct sockaddr_in);
                bcopy(&ip->ip_dst, &dst4->sin_addr, sizeof(dst4->sin_addr));
        }

        result = ip_output(m, NULL, &sc->sc_ro, IP_OUTARGS, NULL, &ipoa);
        lck_mtx_unlock(&sc->sc_ro_mtx);

        /* Assumption: ip_output will free mbuf on errors */
        /* All the output processing is done here, don't let stf_output be called */
        if (result == 0)
                result = EJUSTRETURN;
        *m0 = NULL;
        IFA_REMREF(&ia6->ia_ifa);
        return result;
}
static errno_t
stf_output(
        __unused ifnet_t        ifp,
        __unused mbuf_t m)
{
        /* All processing is done in stf_pre_output
         * this shouldn't be called as the pre_output returns "EJUSTRETURN"
         */
        return 0;
}       

static int
stf_checkaddr4(
        struct stf_softc *sc,
        const struct in_addr *in,
        struct ifnet *inifp)    /* incoming interface */
{
        struct in_ifaddr *ia4;

        /*
         * reject packets with the following address:
         * 224.0.0.0/4 0.0.0.0/8 127.0.0.0/8 255.0.0.0/8
         */
        if (IN_MULTICAST(ntohl(in->s_addr)))
                return -1;
        switch ((ntohl(in->s_addr) & 0xff000000) >> 24) {
        case 0: case 127: case 255:
                return -1;
        }

        /*
         * reject packets with broadcast
         */
        lck_rw_lock_shared(in_ifaddr_rwlock);
        for (ia4 = TAILQ_FIRST(&in_ifaddrhead);
             ia4;
             ia4 = TAILQ_NEXT(ia4, ia_link))
        {
                IFA_LOCK(&ia4->ia_ifa);
                if ((ia4->ia_ifa.ifa_ifp->if_flags & IFF_BROADCAST) == 0) {
                        IFA_UNLOCK(&ia4->ia_ifa);
                        continue;
                }
                if (in->s_addr == ia4->ia_broadaddr.sin_addr.s_addr) {
                        IFA_UNLOCK(&ia4->ia_ifa);
                        lck_rw_done(in_ifaddr_rwlock);
                        return -1;
                }
                IFA_UNLOCK(&ia4->ia_ifa);
        }
        lck_rw_done(in_ifaddr_rwlock);

        /*
         * perform ingress filter
         */
        if (sc && (ifnet_flags(sc->sc_if) & IFF_LINK2) == 0 && inifp) {
                struct sockaddr_in sin;
                struct rtentry *rt;

                bzero(&sin, sizeof(sin));
                sin.sin_family = AF_INET;
                sin.sin_len = sizeof(struct sockaddr_in);
                sin.sin_addr = *in;
                rt = rtalloc1((struct sockaddr *)&sin, 0, 0);
                if (rt != NULL)
                        RT_LOCK(rt);
                if (rt == NULL || rt->rt_ifp != inifp) {
#if 1
                        log(LOG_WARNING, "%s: packet from 0x%x dropped "
                            "due to ingress filter\n", if_name(sc->sc_if),
                            (u_int32_t)ntohl(sin.sin_addr.s_addr));
#endif
                        if (rt != NULL) {
                                RT_UNLOCK(rt);
                                rtfree(rt);
                        }
                        return -1;
                }
                RT_UNLOCK(rt);
                rtfree(rt);
        }

        return 0;
}

static int
stf_checkaddr6(
        struct stf_softc *sc,
        struct in6_addr *in6,
        struct ifnet *inifp)    /* incoming interface */
{
        /*
         * check 6to4 addresses
         */
        if (IN6_IS_ADDR_6TO4(in6))
                return stf_checkaddr4(sc, GET_V4(in6), inifp);

        /*
         * reject anything that look suspicious.  the test is implemented
         * in ip6_input too, but we check here as well to
         * (1) reject bad packets earlier, and
         * (2) to be safe against future ip6_input change.
         */
        if (IN6_IS_ADDR_V4COMPAT(in6) || IN6_IS_ADDR_V4MAPPED(in6))
                return -1;

        return 0;
}

static void
in_stf_input(
        struct mbuf *m,
        int off)
{
        struct stf_softc *sc;
        struct ip *ip;
        struct ip6_hdr ip6;
        u_int8_t otos, itos;
        int proto;
        struct ifnet *ifp;
        struct ifnet_stat_increment_param       stats;

        ip = mtod(m, struct ip *);
        proto = ip->ip_p;

        if (proto != IPPROTO_IPV6) {
                m_freem(m);
                return;
        }

        ip = mtod(m, struct ip *);

        sc = (struct stf_softc *)encap_getarg(m);

        if (sc == NULL || (ifnet_flags(sc->sc_if) & IFF_UP) == 0) {
                m_freem(m);
                return;
        }

        ifp = sc->sc_if;

#if MAC_LABEL
        mac_mbuf_label_associate_ifnet(ifp, m);
#endif

        /*
         * perform sanity check against outer src/dst.
         * for source, perform ingress filter as well.
         */
        if (stf_checkaddr4(sc, &ip->ip_dst, NULL) < 0 ||
            stf_checkaddr4(sc, &ip->ip_src, m->m_pkthdr.rcvif) < 0) {
                m_freem(m);
                return;
        }

        otos = ip->ip_tos;
        mbuf_copydata(m, off, sizeof(ip6), &ip6);

        /*
         * perform sanity check against inner src/dst.
         * for source, perform ingress filter as well.
         */
        if (stf_checkaddr6(sc, &ip6.ip6_dst, NULL) < 0 ||
            stf_checkaddr6(sc, &ip6.ip6_src, m->m_pkthdr.rcvif) < 0) {
                m_freem(m);
                return;
        }

        itos = (ntohl(ip6.ip6_flow) >> 20) & 0xff;
        if ((ifnet_flags(ifp) & IFF_LINK1) != 0)
                ip_ecn_egress(ECN_NORMAL, &otos, &itos);
        else
                ip_ecn_egress(ECN_NOCARE, &otos, &itos);
        ip6.ip6_flow &= ~htonl(0xff << 20);
        ip6.ip6_flow |= htonl((u_int32_t)itos << 20);

        m->m_pkthdr.rcvif = ifp;
        mbuf_pkthdr_setheader(m, mbuf_data(m));
        mbuf_adj(m, off);
        
        if (ifp->if_bpf) {
                /* We need to prepend the address family as a four byte field. */
                u_int32_t af = AF_INET6;
                bpf_tap_in(ifp, 0, m, &af, sizeof(af));
        }

        /*
         * Put the packet to the network layer input queue according to the
         * specified address family.
         * See net/if_gif.c for possible issues with packet processing
         * reorder due to extra queueing.
         */
        bzero(&stats, sizeof(stats));
        stats.packets_in = 1;
        stats.bytes_in = mbuf_pkthdr_len(m);
        mbuf_pkthdr_setrcvif(m, ifp);
        ifnet_input(ifp, m, &stats);
        
        return;
}

static void
stf_rtrequest(
        __unused int cmd,
        struct rtentry *rt,
        __unused struct sockaddr *sa)
{
        if (rt != NULL) {
                RT_LOCK_ASSERT_HELD(rt);
                rt->rt_rmx.rmx_mtu = IPV6_MMTU;
        }
}

static errno_t
stf_ioctl(
        ifnet_t         ifp,
        u_long          cmd,
        void            *data)
{
        struct ifaddr *ifa;
        struct ifreq *ifr;
        struct sockaddr_in6 *sin6;
        int error;

        error = 0;
        switch (cmd) {
        case SIOCSIFADDR:
                ifa = (struct ifaddr *)data;
                if (ifa == NULL) {
                        error = EAFNOSUPPORT;
                        break;
                }
                IFA_LOCK(ifa);
                if (ifa->ifa_addr->sa_family != AF_INET6) {
                        IFA_UNLOCK(ifa);
                        error = EAFNOSUPPORT;
                        break;
                }
                sin6 = (struct sockaddr_in6 *)(void *)ifa->ifa_addr;
                if (IN6_IS_ADDR_6TO4(&sin6->sin6_addr)) {
                        if ( !(ifnet_flags( ifp ) & IFF_UP) ) {
                                /* do this only if the interface is not already up */
                                ifa->ifa_rtrequest = stf_rtrequest;
                                IFA_UNLOCK(ifa);
                                ifnet_set_flags(ifp, IFF_UP, IFF_UP);
                        } else {
                                IFA_UNLOCK(ifa);
                        }
                } else {
                        IFA_UNLOCK(ifa);
                        error = EINVAL;
                }
                IFA_LOCK_ASSERT_NOTHELD(ifa);
                break;

        case SIOCADDMULTI:
        case SIOCDELMULTI:
                ifr = (struct ifreq *)data;
                if (ifr && ifr->ifr_addr.sa_family == AF_INET6)
                        ;
                else
                        error = EAFNOSUPPORT;
                break;

        default:
                error = EOPNOTSUPP;
                break;
        }

        return error;
}