/*      $NetBSD: mpls_ttl.c,v 1.15 2018/12/27 14:03:55 maxv Exp $ */

/*
* Copyright (c) 2010 The NetBSD Foundation, Inc.
* All rights reserved.
*
* This code is derived from software contributed to The NetBSD Foundation
* by Public Access Networks Corporation ("Panix").  It was developed under
* contract to Panix by Eric Haszlakiewicz and Thor Lancelot Simon.
*
* This code is derived from software contributed to The NetBSD Foundation
* by Jason R. Thorpe of Zembu Labs, Inc.
*
* This code is derived from software contributed to The NetBSD Foundation
* by Mihai Chelaru <[email protected]>
*
* 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.
*
* 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.
*/

/*
* 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.
*/

/*
* Copyright (c) 1982, 1986, 1988, 1993
*      The Regents of the University of California.  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 University 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 REGENTS 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 REGENTS 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.
*
*      @(#)ip_icmp.c   8.2 (Berkeley) 1/4/94
*/

#include <sys/cdefs.h>
__KERNEL_RCSID(0, "$NetBSD: mpls_ttl.c,v 1.15 2018/12/27 14:03:55 maxv Exp $");

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

#include <sys/param.h>
#include <sys/malloc.h>
#include <sys/mbuf.h>
#include <sys/errno.h>
#include <sys/socket.h>
#include <sys/systm.h>

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

#include <netinet/in.h>
#include <netinet/in_systm.h>
#include <netinet/ip.h>
#include <netinet/ip_icmp.h>
#include <netinet/icmp_private.h>
#include <netinet/icmp_var.h>

#include <netmpls/mpls.h>
#include <netmpls/mpls_var.h>

#ifdef INET

/* in netinet/ip_icmp.c */
extern int icmpreturndatabytes;

/* ICMP Extensions */
#define MPLS_STACK_ENTRY_CLASS 1
#define MPLS_STACK_ENTRY_C_TYPE 1

struct mpls_extension {
       struct icmp_ext_hdr cmn_hdr;
       struct icmp_ext_obj_hdr obj_hdr;
       union mpls_shim ms;
} __packed;

static void mpls_icmp_error(struct mbuf *, int, int, n_long, int,
   union mpls_shim *);
static struct mbuf *ip4_check(struct mbuf *);

/*
* Send an ICMP Extended error message. References: RFC4884 and RFC4950.
*
* XXX: This code is inspired from icmp_error(), and should really be merged
* into it. icmp_error() should handle ICMP Extended error messages.
*
* XXX: It is called only for ICMP_TIMXCEED_INTRANS but code is too general.
*
* XXX: We're not setting the 'length' field of the Extended ICMP header.
* According to RFC4884, we are in 'non-compliant' mode. Moreover, we're
* not computing the checksum of the Extended ICMP header.
*/
static void
mpls_icmp_error(struct mbuf *n, int type, int code, n_long dest,
   int destmtu, union mpls_shim *shim)
{
       struct ip *oip = mtod(n, struct ip *), *nip;
       unsigned oiplen = oip->ip_hl << 2;
       struct icmp *icp;
       struct mbuf *m;
       unsigned icmplen, mblen, packetlen;
       struct mpls_extension mpls_icmp_ext;

       memset(&mpls_icmp_ext, 0, sizeof(mpls_icmp_ext));
       mpls_icmp_ext.cmn_hdr.version = ICMP_EXT_VERSION;
       mpls_icmp_ext.cmn_hdr.checksum = 0; /* XXX */

       mpls_icmp_ext.obj_hdr.length = htons(sizeof(union mpls_shim) +
           sizeof(struct icmp_ext_obj_hdr));
       mpls_icmp_ext.obj_hdr.class_num = MPLS_STACK_ENTRY_CLASS;
       mpls_icmp_ext.obj_hdr.c_type = MPLS_STACK_ENTRY_C_TYPE;

       mpls_icmp_ext.ms.s_addr = shim->s_addr;

       if (type != ICMP_REDIRECT)
               ICMP_STATINC(ICMP_STAT_ERROR);

       /*
        * Don't send error if the original packet was encrypted.
        * Don't send error if not the first fragment of message.
        * Don't error if the old packet protocol was ICMP
        * error message, only known informational types.
        */
       if (n->m_flags & M_DECRYPTED)
               goto freeit;
       if (oip->ip_off &~ htons(IP_MF|IP_DF))
               goto freeit;
       if (oip->ip_p == IPPROTO_ICMP && type != ICMP_REDIRECT &&
           n->m_len >= oiplen + ICMP_MINLEN &&
           !ICMP_INFOTYPE(((struct icmp *)((char *)oip + oiplen))->icmp_type))
       {
               ICMP_STATINC(ICMP_STAT_OLDICMP);
               goto freeit;
       }

       /* Don't send error in response to a multicast or broadcast packet */
       if (n->m_flags & (M_BCAST|M_MCAST))
               goto freeit;

       /*
        * First, do a rate limitation check.
        */
       if (icmp_ratelimit(&oip->ip_src, type, code))
               /* XXX stats */
               goto freeit;

       /*
        * Now, formulate icmp message
        */
       icmplen = uimin(ICMP_EXT_OFFSET, ntohs(oip->ip_len));

       /*
        * Defend against mbuf chains shorter than oip->ip_len - oiplen:
        */
       mblen = 0;
       for (m = n; m && (mblen < icmplen); m = m->m_next)
               mblen += m->m_len;
       icmplen = uimin(mblen, icmplen);

       packetlen = sizeof(struct ip) + offsetof(struct icmp, icmp_ip) +
           ICMP_EXT_OFFSET + sizeof(mpls_icmp_ext);

       /*
        * As we are not required to return everything we have,
        * we return whatever we can return at ease.
        *
        * Note that ICMP datagrams longer than 576 octets are out of spec
        * according to RFC1812; the limit on icmpreturndatabytes below in
        * icmp_sysctl will keep things below that limit.
        */

       KASSERT(packetlen <= MCLBYTES);

       m = m_gethdr(M_DONTWAIT, MT_HEADER);
       if (m && (packetlen > MHLEN)) {
               MCLGET(m, M_DONTWAIT);
               if ((m->m_flags & M_EXT) == 0) {
                       m_freem(m);
                       m = NULL;
               }
       }
       if (m == NULL)
               goto freeit;

       MCLAIM(m, n->m_owner);
       m->m_len = packetlen;
       if ((m->m_flags & M_EXT) == 0)
               m_align(m, m->m_len);
       m->m_data += sizeof(struct ip);
       m->m_len -= sizeof(struct ip);

       icp = mtod(m, struct icmp *);
       if ((u_int)type > ICMP_MAXTYPE)
               panic("icmp error (mpls_ttl)");
       ICMP_STATINC(ICMP_STAT_OUTHIST + type);
       icp->icmp_type = type;
       if (type == ICMP_REDIRECT)
               icp->icmp_gwaddr.s_addr = dest;
       else {
               icp->icmp_void = 0;
               /*
                * The following assignments assume an overlay with the
                * zeroed icmp_void field.
                */
               if (type == ICMP_PARAMPROB) {
                       icp->icmp_pptr = code;
                       code = 0;
               } else if (type == ICMP_UNREACH &&
                   code == ICMP_UNREACH_NEEDFRAG && destmtu)
                       icp->icmp_nextmtu = htons(destmtu);
       }

       icp->icmp_code = code;

       memset(&icp->icmp_ip, 0, ICMP_EXT_OFFSET);
       m_copydata(n, 0, icmplen, (char *)&icp->icmp_ip);

       /* Append the extension structure */
       memcpy(((char*)&icp->icmp_ip) + ICMP_EXT_OFFSET,
           &mpls_icmp_ext, sizeof(mpls_icmp_ext));

       /*
        * Now, copy old ip header (without options)
        * in front of icmp message.
        */
       if ((m->m_flags & M_EXT) == 0 &&
           m->m_data - sizeof(struct ip) < m->m_pktdat)
               panic("icmp len");
       m->m_data -= sizeof(struct ip);
       m->m_len += sizeof(struct ip);
       m->m_pkthdr.len = m->m_len;
       m_copy_rcvif(m, n);
       nip = mtod(m, struct ip *);
       /* ip_v set in ip_output */
       nip->ip_hl = sizeof(struct ip) >> 2;
       nip->ip_tos = 0;
       nip->ip_len = htons(m->m_len);
       /* ip_id set in ip_output */
       nip->ip_off = htons(0);
       /* ip_ttl set in icmp_reflect */
       nip->ip_p = IPPROTO_ICMP;
       nip->ip_src = oip->ip_src;
       nip->ip_dst = oip->ip_dst;
       icmp_reflect(m);

freeit:
       m_freem(n);
}

static struct mbuf *
ip4_check(struct mbuf *m)
{
       struct ip *iph;
       int hlen, len;

       if (m->m_len < sizeof(struct ip) &&
           (m = m_pullup(m, sizeof(struct ip))) == NULL)
               return NULL;

       iph = mtod(m, struct ip *);

       if (iph->ip_v != IPVERSION)
               goto freeit;
       hlen = iph->ip_hl << 2;
       if (hlen < sizeof(struct ip))
               goto freeit;
       if (hlen > m->m_len) {
               if ((m = m_pullup(m, hlen)) == NULL)
                       return NULL;
               iph = mtod(m, struct ip *);
       }

       /*
        * RFC1122: packets with a multicast source address are
        * not allowed.
        * RFC1122: 127/8 must not appear on wire.
        */
       if (IN_MULTICAST(iph->ip_src.s_addr) ||
           (ntohl(iph->ip_dst.s_addr) >> IN_CLASSA_NSHIFT) == IN_LOOPBACKNET ||
           (ntohl(iph->ip_src.s_addr) >> IN_CLASSA_NSHIFT) == IN_LOOPBACKNET ||
           in_cksum(m, hlen) != 0)
               goto freeit;

       len = ntohs(iph->ip_len);
       if (len < hlen || m->m_pkthdr.len < len)
               goto freeit;

       return m;

freeit:
       m_freem(m);
       return NULL;
}
#endif  /* INET */

struct mbuf *
mpls_ttl_dec(struct mbuf *m)
{
       union mpls_shim *mshim;
#ifdef INET
       union mpls_shim top_shim, bos_shim;
#endif

       if (__predict_false(m->m_len < sizeof(union mpls_shim) &&
           (m = m_pullup(m, sizeof(union mpls_shim))) == NULL))
               return NULL;
       mshim = mtod(m, union mpls_shim *);
       mshim->s_addr = ntohl(mshim->s_addr);
       mshim->shim.ttl--;

       if (mshim->shim.ttl == 0) {
               if (!mpls_icmp_respond) {
                       m_freem(m);
                       return NULL;
               }

#ifdef INET
               /*
                * Shim ttl exceeded. Send back ICMP type 11 code 0.
                */
               bos_shim.s_addr = mshim->s_addr;
               top_shim.s_addr = htonl(mshim->s_addr);
               m_adj(m, sizeof(union mpls_shim));

               /* Goto BOS */
               while (bos_shim.shim.bos == 0) {
                       if (m->m_len < sizeof(union mpls_shim) &&
                           (m = m_pullup(m, sizeof(union mpls_shim))) == NULL) {
                               m_freem(m);
                               return NULL;
                       }
                       bos_shim.s_addr = ntohl(mtod(m, union mpls_shim *)->s_addr);
                       m_adj(m, sizeof(union mpls_shim));
               }

               if ((m = ip4_check(m)) != NULL)
                       mpls_icmp_error(m, ICMP_TIMXCEED, ICMP_TIMXCEED_INTRANS,
                           0, 0, &top_shim);
#else
               m_freem(m);
#endif
               return NULL;
       }

       mshim->s_addr = htonl(mshim->s_addr);

       return m;
}

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