/*
 * $NetBSD: ip_gre.c,v 1.21 2002/08/14 00:23:30 itojun Exp $
 *
 * Copyright (c) 1998 The NetBSD Foundation, Inc.
 * All rights reserved.
 *
 * This code is derived from software contributed to The NetBSD Foundation
 * by Heiko W.Rupp <hwr@pilhuhn.de>
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *        This product includes software developed by the NetBSD
 *        Foundation, Inc. and its contributors.
 * 4. Neither the name of The NetBSD Foundation 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 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.
 */

/*
 * deencapsulate tunneled packets and send them on
 * output half is in net/if_gre.[ch]
 * This currently handles IPPROTO_GRE, IPPROTO_MOBILE
 */

#include "opt_inet.h"

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/mbuf.h>
#include <sys/socket.h>
#include <sys/socketvar.h>
#include <sys/protosw.h>
#include <sys/errno.h>
#include <sys/time.h>
#include <sys/kernel.h>
#include <sys/syslog.h>
#include <sys/in_cksum.h>
#include <net/bpf.h>
#include <net/ethernet.h>
#include <net/if.h>
#include <net/netisr.h>
#include <net/route.h>
#include <net/raw_cb.h>

#ifdef INET
#include <netinet/in.h>
#include <netinet/in_var.h>
#include <netinet/in_systm.h>
#include <netinet/ip.h>
#include <netinet/ip_var.h>
#include <netinet/ip_gre.h>
#else
#error ip_gre input without IP?
#endif

/* Needs IP headers. */
#include <net/gre/if_gre.h>

#include <machine/stdarg.h>

#if 1
void gre_inet_ntoa(struct in_addr in);  /* XXX */
#endif

static struct gre_softc *gre_lookup(struct mbuf *, u_int8_t);

static int      gre_input2(struct mbuf *, int, u_char);

/*
 * De-encapsulate a packet and feed it back through ip input (this
 * routine is called whenever IP gets a packet with proto type
 * IPPROTO_GRE and a local destination address).
 * This really is simple
 */
int
gre_input(struct mbuf **mp, int *offp, int proto)
{
        struct mbuf *m;
        int ret, off;

        off = *offp;
        m = *mp;
        *mp = NULL;

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

        ret = gre_input2(m, off, proto);
        /*
         * ret == 0 : packet not processed, meaning that
         * no matching tunnel that is up is found.
         * we inject it to raw ip socket to see if anyone picks it up.
         */
        if (ret == 0) {
                *mp = m;
                rip_input(mp, offp, proto);
        }
        return(IPPROTO_DONE);
}

/*
 * decapsulate.
 * Does the real work and is called from gre_input() (above)
 * returns 0 if packet is not yet processed
 * and 1 if it needs no further processing
 * proto is the protocol number of the "calling" foo_input()
 * routine.
 */

static int
gre_input2(struct mbuf *m ,int hlen, u_char proto)
{
        static const uint32_t af = AF_INET;
        struct greip *gip = mtod(m, struct greip *);
        int isr;
        struct gre_softc *sc;
        u_short flags;

        if ((sc = gre_lookup(m, proto)) == NULL) {
                /* No matching tunnel or tunnel is down. */
                return (0);
        }

        IFNET_STAT_INC(&sc->sc_if, ipackets, 1);
        IFNET_STAT_INC(&sc->sc_if, ibytes, m->m_pkthdr.len);

        switch (proto) {
        case IPPROTO_GRE:
                hlen += sizeof (struct gre_h);

                /* process GRE flags as packet can be of variable len */
                flags = ntohs(gip->gi_flags);

                /* Checksum & Offset are present */
                if ((flags & GRE_CP) | (flags & GRE_RP))
                        hlen += 4;
                /* We don't support routing fields (variable length) */
                if (flags & GRE_RP)
                        return(0);
                if (flags & GRE_KP)
                        hlen += 4;
                if (flags & GRE_SP)
                        hlen +=4;

                switch (ntohs(gip->gi_ptype)) { /* ethertypes */
                case ETHERTYPE_IP:
                case WCCP_PROTOCOL_TYPE:
                        isr = NETISR_IP;
                        break;
                case ETHERTYPE_IPV6:
                        /* FALLTHROUGH */
                default:           /* others not yet supported */
                        return(0);
                }
                break;
        default:
                /* others not yet supported */
                return(0);
        }

        m->m_data += hlen;
        m->m_len -= hlen;
        m->m_pkthdr.len -= hlen;

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

        m->m_pkthdr.rcvif = &sc->sc_if;
        m->m_flags &= ~M_HASH;
        netisr_queue(isr, m);
        return(1);      /* packet is done, no further processing needed */
}

/*
 * input routine for IPPRPOTO_MOBILE
 * This is a little bit diffrent from the other modes, as the
 * encapsulating header was not prepended, but instead inserted
 * between IP header and payload
 */

int
gre_mobile_input(struct mbuf **mp, int *offp, int proto)
{
        static const uint32_t af = AF_INET;
        struct mbuf *m = *mp;
        struct ip *ip = mtod(m, struct ip *);
        struct mobip_h *mip = mtod(m, struct mobip_h *);
        struct gre_softc *sc;
        int msiz;

        if ((sc = gre_lookup(m, IPPROTO_MOBILE)) == NULL) {
                /* No matching tunnel or tunnel is down. */
                m_freem(m);
                return(IPPROTO_DONE);
        }

        IFNET_STAT_INC(&sc->sc_if, ipackets, 1);
        IFNET_STAT_INC(&sc->sc_if, ibytes, m->m_pkthdr.len);

        if(ntohs(mip->mh.proto) & MOB_H_SBIT) {
                msiz = MOB_H_SIZ_L;
                mip->mi.ip_src.s_addr = mip->mh.osrc;
        } else {
                msiz = MOB_H_SIZ_S;
        }
        mip->mi.ip_dst.s_addr = mip->mh.odst;
        mip->mi.ip_p = (ntohs(mip->mh.proto) >> 8);

        if (gre_in_cksum((u_short*)&mip->mh,msiz) != 0) {
                m_freem(m);
                return(IPPROTO_DONE);
        }

        bcopy((caddr_t)(ip) + (ip->ip_hl << 2) + msiz, (caddr_t)(ip) +
            (ip->ip_hl << 2), m->m_len - msiz - (ip->ip_hl << 2));
        m->m_len -= msiz;
        m->m_pkthdr.len -= msiz;

        /*
         * ip_len is left in network byte order throughout, now.
         * rip_input already decreased ip_len byt the length of the
         * IP header.
         */
        ip->ip_len = htons(ntohs(ip->ip_len) + sizeof(struct ip) - msiz);
        
        ip->ip_sum = 0;
        ip->ip_sum = in_cksum(m, (ip->ip_hl << 2));

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

        m->m_pkthdr.rcvif = &sc->sc_if;

        netisr_queue(NETISR_IP, m);
        return(IPPROTO_DONE);
}

/*
 * Find the gre interface associated with our src/dst/proto set.
 */
static struct gre_softc *
gre_lookup(struct mbuf *m, u_int8_t proto)
{
        struct ip *ip = mtod(m, struct ip *);
        struct gre_softc *sc;

        for (sc = LIST_FIRST(&gre_softc_list); sc != NULL;
             sc = LIST_NEXT(sc, sc_list)) {
                if ((sc->g_dst.s_addr == ip->ip_src.s_addr) &&
                    (sc->g_src.s_addr == ip->ip_dst.s_addr) &&
                    (sc->g_proto == proto) &&
                    ((sc->sc_if.if_flags & IFF_UP) != 0))
                        return (sc);
        }

        return (NULL);
}