/*      $FreeBSD: src/sys/net/if_stf.c,v 1.1.2.11 2003/01/23 21:06:44 sam Exp $ */
/*      $KAME: if_stf.c,v 1.73 2001/12/03 11:08:30 keiichi 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.
 */

/*
 * 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 "opt_inet.h"
#include "opt_inet6.h"

#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 <machine/cpu.h>

#include <sys/malloc.h>

#include <net/if.h>
#include <net/route.h>
#include <net/netisr.h>
#include <net/if_types.h>
#include <net/ifq_var.h>
#include <net/netisr2.h>
#include "if_stf.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 <netinet6/nd6.h>
#include <netinet/ip_ecn.h>

#include <netinet/ip_encap.h>

#include <machine/stdarg.h>

#include <net/net_osdep.h>

#include <net/bpf.h>

#define IN6_IS_ADDR_6TO4(x)     (ntohs((x)->s6_addr16[0]) == 0x2002)
#define GET_V4(x)       ((struct in_addr *)(&(x)->s6_addr16[1]))

struct stf_softc {
        struct ifnet    sc_if;     /* common area */
        struct route    *route_pcpu;
        const struct encaptab *encap_cookie;
};

static struct stf_softc *stf;

static MALLOC_DEFINE(M_STF, "stf", "6to4 Tunnel Interface");
static int ip_stf_ttl = 40;

extern  struct domain inetdomain;
struct protosw in_stf_protosw =
    {
        .pr_type = SOCK_RAW,
        .pr_domain = &inetdomain,
        .pr_protocol = IPPROTO_IPV6,
        .pr_flags = PR_ATOMIC|PR_ADDR,

        .pr_input = in_stf_input,
        .pr_output = rip_output,
        .pr_ctlinput = NULL,
        .pr_ctloutput = rip_ctloutput,

        .pr_usrreqs = &rip_usrreqs
    };

static int stfmodevent (module_t, int, void *);
static int stf_encapcheck (const struct mbuf *, int, int, void *);
static struct in6_ifaddr *stf_getsrcifa6 (struct ifnet *);
static int stf_output (struct ifnet *, struct mbuf *, struct sockaddr *,
        struct rtentry *);
static int stf_checkaddr4 (struct stf_softc *, struct in_addr *,
        struct ifnet *);
static int stf_checkaddr6 (struct stf_softc *, struct in6_addr *,
        struct ifnet *);
static void stf_rtrequest (int, struct rtentry *);
static int stf_ioctl (struct ifnet *, u_long, caddr_t, struct ucred *);

static int
stfmodevent(module_t mod, int type, void *data)
{
        struct stf_softc *sc;
        int err, cpu;
        const struct encaptab *p;

        switch (type) {
        case MOD_LOAD:
                stf = kmalloc(sizeof(struct stf_softc), M_STF,
                    M_WAITOK | M_ZERO);
                sc = stf;

                bzero(sc, sizeof(*sc));
                if_initname(&(sc->sc_if), "stf", 0);

                p = encap_attach_func(AF_INET, IPPROTO_IPV6, stf_encapcheck,
                    (void *)&in_stf_protosw, sc);
                if (p == NULL) {
                        kprintf("%s: attach failed\n", if_name(&sc->sc_if));
                        return (ENOMEM);
                }
                sc->encap_cookie = p;
                sc->route_pcpu = kmalloc(netisr_ncpus * sizeof(struct route),
                    M_STF, M_WAITOK | M_ZERO);

                sc->sc_if.if_mtu    = IPV6_MMTU;
                sc->sc_if.if_flags  = 0;
                sc->sc_if.if_ioctl  = stf_ioctl;
                sc->sc_if.if_output = stf_output;
                sc->sc_if.if_type   = IFT_STF;
#if 0
                /* turn off ingress filter */
                sc->sc_if.if_flags  |= IFF_LINK2;
#endif
                ifq_set_maxlen(&sc->sc_if.if_snd, IFQ_MAXLEN);
                if_attach(&sc->sc_if, NULL);
                bpfattach(&sc->sc_if, DLT_NULL, sizeof(uint32_t));
                /*
                 * 6to4 interface is very special: no multicast, no linklocal.
                 * RFC2529 specifies how to make linklocals, but there's no
                 * use and it is rather harmful to have one.
                 *
                 * NOTE: ND_IFINFO() is only available after if_attach().
                 */
                ND_IFINFO(&sc->sc_if)->flags &= ~ND6_IFF_AUTO_LINKLOCAL;
                ND_IFINFO(&sc->sc_if)->flags |= ND6_IFF_NO_DAD;
                break;
        case MOD_UNLOAD:
                sc = stf;
                bpfdetach(&sc->sc_if);
                if_detach(&sc->sc_if);
                err = encap_detach(sc->encap_cookie);
                KASSERT(err == 0, ("Unexpected error detaching encap_cookie"));
                for (cpu = 0; cpu < netisr_ncpus; ++cpu) {
                        if (sc->route_pcpu[cpu].ro_rt != NULL) {
                                rtfree_async(sc->route_pcpu[cpu].ro_rt);
                                sc->route_pcpu[cpu].ro_rt = NULL;
                        }
                }
                kfree(sc->route_pcpu, M_STF);
                kfree(sc, M_STF);
                break;
        }

        return (0);
}

static moduledata_t stf_mod = {
        "if_stf",
        stfmodevent,
        0
};

DECLARE_MODULE(if_stf, stf_mod, SI_SUB_PSEUDO, SI_ORDER_ANY);

static int
stf_encapcheck(const struct mbuf *m, 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 ((sc->sc_if.if_flags & IFF_UP) == 0)
                return 0;

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

        if (proto != IPPROTO_IPV6)
                return 0;

        m_copydata(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:...
         */
        if (bcmp(GET_V4(&ia6->ia_addr.sin6_addr), &ip.ip_dst,
            sizeof(ip.ip_dst)) != 0)
                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)
                return 0;

        /* stf interface makes single side match only */
        return 32;
}

static struct in6_ifaddr *
stf_getsrcifa6(struct ifnet *ifp)
{
        struct ifaddr_container *ifac;
        struct sockaddr_in6 *sin6;
        struct in_addr in;

        TAILQ_FOREACH(ifac, &ifp->if_addrheads[mycpuid], ifa_link) {
                struct ifaddr *ia = ifac->ifa;
                struct in_ifaddr_container *iac;

                if (ia->ifa_addr == NULL)
                        continue;
                if (ia->ifa_addr->sa_family != AF_INET6)
                        continue;
                sin6 = (struct sockaddr_in6 *)ia->ifa_addr;
                if (!IN6_IS_ADDR_6TO4(&sin6->sin6_addr))
                        continue;

                bcopy(GET_V4(&sin6->sin6_addr), &in, sizeof(in));
                LIST_FOREACH(iac, INADDR_HASH(in.s_addr), ia_hash) {
                        if (iac->ia->ia_addr.sin_addr.s_addr == in.s_addr)
                                break;
                }
                if (iac == NULL)
                        continue;

                return (struct in6_ifaddr *)ia;
        }

        return NULL;
}

static int
stf_output_serialized(struct ifnet *ifp, struct mbuf *m, struct sockaddr *dst,
                      struct rtentry *rt)
{
        struct stf_softc *sc;
        struct sockaddr_in6 *dst6;
        struct in_addr *in4;
        struct sockaddr_in *dst4;
        u_int8_t tos;
        struct ip *ip;
        struct ip6_hdr *ip6;
        struct in6_ifaddr *ia6;
        struct route *ro;
        static const uint32_t af = AF_INET6;

        ASSERT_NETISR_NCPUS(mycpuid);

        sc = (struct stf_softc*)ifp;
        dst6 = (struct sockaddr_in6 *)dst;

        /* just in case */
        if ((ifp->if_flags & IFF_UP) == 0) {
                m_freem(m);
                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) {
                m_freem(m);
                return ENETDOWN;
        }

        if (m->m_len < sizeof(*ip6)) {
                m = m_pullup(m, sizeof(*ip6));
                if (!m)
                        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 {
                m_freem(m);
                return ENETUNREACH;
        }

        if (ifp->if_bpf) {
                bpf_gettoken();
                if (ifp->if_bpf)
                        bpf_ptap(ifp->if_bpf, m, &af, sizeof(af));
                bpf_reltoken();
        }

        M_PREPEND(m, sizeof(struct ip), M_NOWAIT);
        if (m && m->m_len < sizeof(struct ip))
                m = m_pullup(m, sizeof(struct ip));
        if (m == NULL)
                return ENOBUFS;
        ip = mtod(m, struct ip *);

        bzero(ip, sizeof(*ip));

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

        ro = &sc->route_pcpu[mycpuid];
        dst4 = (struct sockaddr_in *)&ro->ro_dst;
        if (dst4->sin_family != AF_INET ||
            bcmp(&dst4->sin_addr, &ip->ip_dst, sizeof(ip->ip_dst)) != 0) {
                /* cache route doesn't match */
                dst4->sin_family = AF_INET;
                dst4->sin_len = sizeof(struct sockaddr_in);
                bcopy(&ip->ip_dst, &dst4->sin_addr, sizeof(dst4->sin_addr));
                if (ro->ro_rt) {
                        RTFREE(ro->ro_rt);
                        ro->ro_rt = NULL;
                }
        }
        if (ro->ro_rt != NULL && (ro->ro_rt->rt_flags & RTF_UP) == 0) {
                RTFREE(ro->ro_rt);
                ro->ro_rt = NULL;
        }

        if (ro->ro_rt == NULL) {
                rtalloc(ro);
                if (ro->ro_rt == NULL) {
                        m_freem(m);
                        return ENETUNREACH;
                }
        }

        return ip_output(m, NULL, ro, IP_DEBUGROUTE, NULL, NULL);
}

static int
stf_output(struct ifnet *ifp, struct mbuf *m, struct sockaddr *dst,
           struct rtentry *rt)
{
        struct ifaltq_subque *ifsq = ifq_get_subq_default(&ifp->if_snd);
        int error;

        ifsq_serialize_hw(ifsq);
        error = stf_output_serialized(ifp, m, dst, rt);
        ifsq_deserialize_hw(ifsq);

        return error;
}

/*
 * Parameters:
 *      inifp:  incoming interface
 */
static int
stf_checkaddr4(struct stf_softc *sc, struct in_addr *in, struct ifnet *inifp)
{
        struct in_ifaddr_container *iac;

        /*
         * 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
         */
        TAILQ_FOREACH(iac, &in_ifaddrheads[mycpuid], ia_link) {
                struct in_ifaddr *ia4 = iac->ia;

                if ((ia4->ia_ifa.ifa_ifp->if_flags & IFF_BROADCAST) == 0)
                        continue;
                if (in->s_addr == ia4->ia_broadaddr.sin_addr.s_addr)
                        return -1;
        }

        /*
         * perform ingress filter
         */
        if (sc && (sc->sc_if.if_flags & 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 = rtpurelookup((struct sockaddr *)&sin);
                if (!rt || rt->rt_ifp != inifp) {
#if 0
                        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)
                                rtfree(rt);
                        return -1;
                }
                rtfree(rt);
        }

        return 0;
}

/*
 * Parameters:
 *      inifp:  incoming interface
 */
static int
stf_checkaddr6(struct stf_softc *sc, struct in6_addr *in6, struct ifnet *inifp)
{
        /*
         * 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;
}

int
in_stf_input(struct mbuf **mp, int *offp, int proto)
{
        struct mbuf *m;
        struct stf_softc *sc;
        struct ip *ip;
        struct ip6_hdr *ip6;
        u_int8_t otos, itos;
        struct ifnet *ifp;
        int off;
        static const uint32_t af = AF_INET6;

        m = *mp;
        off = *offp;

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

        ip = mtod(m, struct ip *);

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

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

        ifp = &sc->sc_if;

        /*
         * 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(IPPROTO_DONE);
        }

        otos = ip->ip_tos;
        m_adj(m, off);

        if (m->m_len < sizeof(*ip6)) {
                m = m_pullup(m, sizeof(*ip6));
                if (!m)
                        return(IPPROTO_DONE);
        }
        ip6 = mtod(m, struct ip6_hdr *);

        /*
         * 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(IPPROTO_DONE);
        }

        itos = (ntohl(ip6->ip6_flow) >> 20) & 0xff;
        if ((ifp->if_flags & IFF_LINK1) != 0)
                ip_ecn_egress(ECN_ALLOWED, &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;

        if (ifp->if_bpf) {
                bpf_gettoken();
                if (ifp->if_bpf)
                        bpf_ptap(ifp->if_bpf, m, &af, sizeof(af));
                bpf_reltoken();
        }

        /*
         * 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.
         */
        IFNET_STAT_INC(ifp, ipackets, 1);
        IFNET_STAT_INC(ifp, ibytes, m->m_pkthdr.len);
        m->m_flags &= ~M_HASH;
        netisr_queue(NETISR_IPV6, m);
        return(IPPROTO_DONE);
}

/* ARGSUSED */
static void
stf_rtrequest(int cmd, struct rtentry *rt)
{

        if (rt)
                rt->rt_rmx.rmx_mtu = IPV6_MMTU;
}

static int
stf_ioctl(struct ifnet *ifp, u_long cmd, caddr_t data, struct ucred *cr)
{
        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 || ifa->ifa_addr->sa_family != AF_INET6) {
                        error = EAFNOSUPPORT;
                        break;
                }
                sin6 = (struct sockaddr_in6 *)ifa->ifa_addr;
                if (IN6_IS_ADDR_6TO4(&sin6->sin6_addr)) {
                        ifa->ifa_rtrequest = stf_rtrequest;
                        ifp->if_flags |= IFF_UP;
                } else
                        error = EINVAL;
                break;

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

        default:
                error = EINVAL;
                break;
        }

        return error;
}