/*      $NetBSD: in6_gif.c,v 1.96 2022/12/07 08:30:15 knakahara Exp $   */
/*      $KAME: in6_gif.c,v 1.62 2001/07/29 04:27:25 itojun 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.
 */

#include <sys/cdefs.h>
__KERNEL_RCSID(0, "$NetBSD: in6_gif.c,v 1.96 2022/12/07 08:30:15 knakahara Exp $");

#ifdef _KERNEL_OPT
#include "opt_inet.h"
#endif

#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/ioctl.h>
#include <sys/queue.h>
#include <sys/syslog.h>
#include <sys/kernel.h>

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

#include <netinet/in.h>
#include <netinet/in_systm.h>
#ifdef INET
#include <netinet/ip.h>
#endif
#include <netinet/ip_encap.h>
#ifdef INET6
#include <netinet/ip6.h>
#include <netinet6/ip6_var.h>
#include <netinet6/ip6_private.h>
#include <netinet6/in6_gif.h>
#include <netinet6/in6_var.h>
#endif
#include <netinet6/ip6protosw.h> /* for struct ip6ctlparam */
#include <netinet/ip_ecn.h>

#include <net/if_gif.h>

static int gif_validate6(const struct ip6_hdr *, struct gif_variant *,
        struct ifnet *);

int     ip6_gif_hlim = GIF_HLIM;
int     ip6_gif_pmtu = 0;

static const struct encapsw in6_gif_encapsw;

/* 
 * family - family of the packet to be encapsulate. 
 */

static int
in6_gif_output(struct gif_variant *var, int family, struct mbuf *m)
{
        struct rtentry *rt;
        struct gif_softc *sc;
        struct sockaddr_in6 *sin6_src;
        struct sockaddr_in6 *sin6_dst;
        struct ifnet *ifp;
        struct ip6_hdr *ip6;
        struct route *ro_pc;
        kmutex_t *lock_pc;
        int proto, error;
        u_int8_t itos, otos;

        KASSERT(gif_heldref_variant(var));

        sin6_src = satosin6(var->gv_psrc);
        sin6_dst = satosin6(var->gv_pdst);
        ifp = &var->gv_softc->gif_if;

        if (sin6_src == NULL || sin6_dst == NULL ||
            sin6_src->sin6_family != AF_INET6 ||
            sin6_dst->sin6_family != AF_INET6) {
                m_freem(m);
                return EAFNOSUPPORT;
        }

        switch (family) {
#ifdef INET
        case AF_INET:
            {
                struct ip *ip;

                proto = IPPROTO_IPV4;
                if (m->m_len < sizeof(*ip)) {
                        m = m_pullup(m, sizeof(*ip));
                        if (!m)
                                return ENOBUFS;
                }
                ip = mtod(m, struct ip *);
                itos = ip->ip_tos;
                break;
            }
#endif
#ifdef INET6
        case AF_INET6:
            {
                proto = IPPROTO_IPV6;
                if (m->m_len < sizeof(*ip6)) {
                        m = m_pullup(m, sizeof(*ip6));
                        if (!m)
                                return ENOBUFS;
                }
                ip6 = mtod(m, struct ip6_hdr *);
                itos = (ntohl(ip6->ip6_flow) >> 20) & 0xff;
                break;
            }
#endif
        default:
#ifdef DEBUG
                printf("in6_gif_output: warning: unknown family %d passed\n",
                        family);
#endif
                m_freem(m);
                return EAFNOSUPPORT;
        }

        /* prepend new IP header */
        M_PREPEND(m, sizeof(struct ip6_hdr), M_DONTWAIT);
        if (m && m->m_len < sizeof(struct ip6_hdr))
                m = m_pullup(m, sizeof(struct ip6_hdr));
        if (m == NULL)
                return ENOBUFS;

        ip6 = mtod(m, struct ip6_hdr *);
        ip6->ip6_flow   = 0;
        ip6->ip6_vfc    &= ~IPV6_VERSION_MASK;
        ip6->ip6_vfc    |= IPV6_VERSION;
#if 0   /* ip6->ip6_plen will be filled by ip6_output */
        ip6->ip6_plen   = htons((u_int16_t)m->m_pkthdr.len);
#endif
        ip6->ip6_nxt    = proto;
        ip6->ip6_hlim   = ip6_gif_hlim;
        ip6->ip6_src    = sin6_src->sin6_addr;
        /* bidirectional configured tunnel mode */
        if (!IN6_IS_ADDR_UNSPECIFIED(&sin6_dst->sin6_addr))
                ip6->ip6_dst = sin6_dst->sin6_addr;
        else  {
                m_freem(m);
                return ENETUNREACH;
        }
        if (ifp->if_flags & IFF_LINK1)
                ip_ecn_ingress(ECN_ALLOWED, &otos, &itos);
        else
                ip_ecn_ingress(ECN_NOCARE, &otos, &itos);
        ip6->ip6_flow &= ~ntohl(0xff00000);
        ip6->ip6_flow |= htonl((u_int32_t)otos << 20);

        sc = ifp->if_softc;
        if_tunnel_get_ro(sc->gif_ro_percpu, &ro_pc, &lock_pc);
        rt = rtcache_lookup(ro_pc, var->gv_pdst);
        if (rt == NULL) {
                if_tunnel_put_ro(sc->gif_ro_percpu, lock_pc);
                m_freem(m);
                return ENETUNREACH;
        }

        /* If the route constitutes infinite encapsulation, punt. */
        if (rt->rt_ifp == ifp) {
                rtcache_unref(rt, ro_pc);
                rtcache_free(ro_pc);
                if_tunnel_put_ro(sc->gif_ro_percpu, lock_pc);
                m_freem(m);
                return ENETUNREACH;     /* XXX */
        }
        rtcache_unref(rt, ro_pc);

#ifdef IPV6_MINMTU
        int flags;

        /*
         * - GIF_PMTU_MINMTU
         *   Force fragmentation to minimum MTU to avoid path MTU discovery
         * - GIF_PMTU_OUTERMTU
         *   Trust outer MTU is large enough to send all packets
         *
         * It is too painful to ask for resend of inner packet, to achieve
         * path MTU discovery for encapsulated packets.
         *
         * See RFC4459.
         */
        if (sc->gif_pmtu == GIF_PMTU_SYSDEFAULT) {
                switch (ip6_gif_pmtu) {
                case GIF_PMTU_MINMTU:
                        flags = IPV6_MINMTU;
                        break;
                case GIF_PMTU_OUTERMTU:
                        flags = 0;
                        break;
                default:
#ifdef DEBUG
                        log(LOG_DEBUG, "%s: ignore unexpected ip6_gif_pmtu %d\n",
                            __func__, ip6_gif_pmtu);
#endif
                        flags = IPV6_MINMTU;
                        break;
                }
        } else {
                switch (sc->gif_pmtu) {
                case GIF_PMTU_MINMTU:
                        flags = IPV6_MINMTU;
                        break;
                case GIF_PMTU_OUTERMTU:
                        flags = 0;
                        break;
                default:
#ifdef DEBUG
                        log(LOG_DEBUG, "%s: ignore unexpected gif_pmtu of %s %d\n",
                            __func__, ifp->if_xname, sc->gif_pmtu);
#endif
                        flags = IPV6_MINMTU;
                        break;
                }
        }

        error = ip6_output(m, 0, ro_pc, flags, NULL, NULL, NULL);
#else
        error = ip6_output(m, 0, ro_pc, 0, NULL, NULL, NULL);
#endif
        if_tunnel_put_ro(sc->gif_ro_percpu, lock_pc);
        return (error);
}

int
in6_gif_input(struct mbuf **mp, int *offp, int proto, void *eparg)
{
        struct mbuf *m = *mp;
        struct gif_softc *sc = eparg;
        struct ifnet *gifp;
        struct ip6_hdr *ip6;
        int af = 0;
        u_int32_t otos;

        KASSERT(sc != NULL);

        ip6 = mtod(m, struct ip6_hdr *);

        gifp = &sc->gif_if;
        if ((gifp->if_flags & IFF_UP) == 0) {
                m_freem(m);
                IP6_STATINC(IP6_STAT_NOGIF);
                return IPPROTO_DONE;
        }
#ifndef GIF_ENCAPCHECK
        struct psref psref_var;
        struct gif_variant *var = gif_getref_variant(sc, &psref_var);
        /* other CPU do delete_tunnel */
        if (var->gv_psrc == NULL || var->gv_pdst == NULL) {
                gif_putref_variant(var, &psref_var);
                m_freem(m);
                IP6_STATINC(IP6_STAT_NOGIF);
                return IPPROTO_DONE;
        }

        struct psref psref;
        struct ifnet *rcvif = m_get_rcvif_psref(m, &psref);
        if (rcvif == NULL || !gif_validate6(ip6, var, rcvif)) {
                m_put_rcvif_psref(rcvif, &psref);
                gif_putref_variant(var, &psref_var);
                m_freem(m);
                IP6_STATINC(IP6_STAT_NOGIF);
                return IPPROTO_DONE;
        }
        m_put_rcvif_psref(rcvif, &psref);
        gif_putref_variant(var, &psref_var);
#endif

        otos = ip6->ip6_flow;
        m_adj(m, *offp);

        switch (proto) {
#ifdef INET
        case IPPROTO_IPV4:
            {
                struct ip *ip;
                u_int8_t otos8;
                af = AF_INET;
                otos8 = (ntohl(otos) >> 20) & 0xff;
                if (m->m_len < sizeof(*ip)) {
                        m = m_pullup(m, sizeof(*ip));
                        if (!m)
                                return IPPROTO_DONE;
                }
                ip = mtod(m, struct ip *);
                if (gifp->if_flags & IFF_LINK1)
                        ip_ecn_egress(ECN_ALLOWED, &otos8, &ip->ip_tos);
                else
                        ip_ecn_egress(ECN_NOCARE, &otos8, &ip->ip_tos);
                break;
            }
#endif /* INET */
#ifdef INET6
        case IPPROTO_IPV6:
            {
                struct ip6_hdr *ip6x;
                af = AF_INET6;
                if (m->m_len < sizeof(*ip6x)) {
                        m = m_pullup(m, sizeof(*ip6x));
                        if (!m)
                                return IPPROTO_DONE;
                }
                ip6x = mtod(m, struct ip6_hdr *);
                if (gifp->if_flags & IFF_LINK1)
                        ip6_ecn_egress(ECN_ALLOWED, &otos, &ip6x->ip6_flow);
                else
                        ip6_ecn_egress(ECN_NOCARE, &otos, &ip6x->ip6_flow);
                break;
            }
#endif
        default:
                IP6_STATINC(IP6_STAT_NOGIF);
                m_freem(m);
                return IPPROTO_DONE;
        }

        gif_input(m, af, gifp);
        return IPPROTO_DONE;
}

/*
 * validate outer address.
 */
static int
gif_validate6(const struct ip6_hdr *ip6, struct gif_variant *var, 
        struct ifnet *ifp)
{
        const struct sockaddr_in6 *src, *dst;
        int ret;

        src = satosin6(var->gv_psrc);
        dst = satosin6(var->gv_pdst);

        ret = in6_tunnel_validate(ip6, &src->sin6_addr, &dst->sin6_addr);
        if (ret == 0)
                return 0;

        /* ingress filters on outer source */
        if ((var->gv_softc->gif_if.if_flags & IFF_LINK2) == 0 && ifp) {
                union {
                        struct sockaddr sa;
                        struct sockaddr_in6 sin6;
                } u;
                struct rtentry *rt;

                /* XXX scopeid */
                sockaddr_in6_init(&u.sin6, &ip6->ip6_src, 0, 0, 0);
                rt = rtalloc1(&u.sa, 0);
                if (rt == NULL || rt->rt_ifp != ifp) {
#if 0
                        char ip6buf[INET6_ADDRSTRLEN];
                        log(LOG_WARNING, "%s: packet from %s dropped "
                            "due to ingress filter\n",
                            if_name(&var->gv_softc->gif_if),
                            IN6_PRINT(ip6buf, &u.sin6.sin6_addr));
#endif
                        if (rt != NULL)
                                rt_unref(rt);
                        return 0;
                }
                rt_unref(rt);
        }

        return ret;
}

#ifdef GIF_ENCAPCHECK
/*
 * we know that we are in IFF_UP, outer address available, and outer family
 * matched the physical addr family.  see gif_encapcheck().
 */
int
gif_encapcheck6(struct mbuf *m, int off, int proto, struct gif_variant *var)
{
        struct ip6_hdr ip6;
        struct ifnet *ifp = NULL;
        int r;
        struct psref psref;

        m_copydata(m, 0, sizeof(ip6), (void *)&ip6);
        if ((m->m_flags & M_PKTHDR) != 0)
                ifp = m_get_rcvif_psref(m, &psref);

        r = gif_validate6(&ip6, var, ifp);

        m_put_rcvif_psref(ifp, &psref);
        return r;
}
#endif

int
in6_gif_attach(struct gif_variant *var)
{
#ifndef GIF_ENCAPCHECK
        struct sockaddr_in6 mask6;

        memset(&mask6, 0, sizeof(mask6));
        mask6.sin6_len = sizeof(struct sockaddr_in6);
        mask6.sin6_addr.s6_addr32[0] = mask6.sin6_addr.s6_addr32[1] =
            mask6.sin6_addr.s6_addr32[2] = mask6.sin6_addr.s6_addr32[3] = ~0;

        if (!var->gv_psrc || !var->gv_pdst)
                return EINVAL;

        var->gv_encap_cookie6 = encap_attach_addr(AF_INET6, -1, var->gv_psrc,
            var->gv_pdst, NULL, &in6_gif_encapsw, var->gv_softc);
#else
        var->gv_encap_cookie6 = encap_attach_addr(AF_INET6, -1, var->gv_psrc,
            var->gv_pdst, gif_encapcheck, &in6_gif_encapsw, var->gv_softc);
#endif
        if (var->gv_encap_cookie6 == NULL)
                return EEXIST;

        var->gv_output = in6_gif_output;
        return 0;
}

int
in6_gif_detach(struct gif_variant *var)
{
        int error;
        struct gif_softc *sc = var->gv_softc;

        error = encap_detach(var->gv_encap_cookie6);
        if (error == 0)
                var->gv_encap_cookie6 = NULL;

        if_tunnel_ro_percpu_rtcache_free(sc->gif_ro_percpu);

        return error;
}

void *
in6_gif_ctlinput(int cmd, const struct sockaddr *sa, void *d, void *eparg)
{
        struct gif_softc *sc = eparg;
        struct gif_variant *var;
        struct ip6ctlparam *ip6cp = NULL;
        struct ip6_hdr *ip6;
        const struct sockaddr_in6 *dst6;
        struct route *ro_pc;
        kmutex_t *lock_pc;
        struct psref psref;

        if (sa->sa_family != AF_INET6 ||
            sa->sa_len != sizeof(struct sockaddr_in6))
                return NULL;

        if ((unsigned)cmd >= PRC_NCMDS)
                return NULL;
        if (cmd == PRC_HOSTDEAD)
                d = NULL;
        else if (inet6ctlerrmap[cmd] == 0)
                return NULL;

        /* if the parameter is from icmp6, decode it. */
        if (d != NULL) {
                ip6cp = (struct ip6ctlparam *)d;
                ip6 = ip6cp->ip6c_ip6;
        } else {
                ip6 = NULL;
        }

        if (!ip6)
                return NULL;

        var = gif_getref_variant(sc, &psref);
        if (var->gv_psrc == NULL || var->gv_pdst == NULL) {
                gif_putref_variant(var, &psref);
                return NULL;
        }
        if (var->gv_psrc->sa_family != AF_INET6) {
                gif_putref_variant(var, &psref);
                return NULL;
        }
        gif_putref_variant(var, &psref);

        if_tunnel_get_ro(sc->gif_ro_percpu, &ro_pc, &lock_pc);
        dst6 = satocsin6(rtcache_getdst(ro_pc));
        /* XXX scope */
        if (dst6 == NULL)
                ;
        else if (IN6_ARE_ADDR_EQUAL(&ip6->ip6_dst, &dst6->sin6_addr))
                rtcache_free(ro_pc);

        if_tunnel_put_ro(sc->gif_ro_percpu, lock_pc);
        return NULL;
}

ENCAP_PR_WRAP_CTLINPUT(in6_gif_ctlinput)
#define in6_gif_ctlinput        in6_gif_ctlinput_wrapper

static const struct encapsw in6_gif_encapsw = {
        .encapsw6 = {
                .pr_input       = in6_gif_input,
                .pr_ctlinput    = in6_gif_ctlinput,
        }
};