/*
 * $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);
	}

	sc->sc_if.if_ipackets++;
	sc->sc_if.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_ptap(sc->sc_if.if_bpf, m, &af, sizeof(af));

	m->m_pkthdr.rcvif = &sc->sc_if;
	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;
	u_char osrc = 0;
	int msiz, hlen;

	hlen = *offp;

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

	sc->sc_if.if_ipackets++;
	sc->sc_if.if_ibytes += m->m_pkthdr.len;

	if(ntohs(mip->mh.proto) & MOB_H_SBIT) {
		osrc = 1;
		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;

	/*
	 * On FreeBSD, rip_input() supplies us with ip->ip_len
	 * already converted into host byteorder and also decreases
	 * it by the lengh of IP header, however, ip_input() expects
	 * that this field is in the original format (network byteorder
	 * and full size of IP packet), so that adjust accordingly.
	 */
	ip->ip_len = htons(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_ptap(sc->sc_if.if_bpf, m, &af, sizeof(af));

	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);
}