FreeBSD/Linux Kernel Cross Reference
sys/netinet6/in6_ifattach.c

     /*      $NetBSD: in6_ifattach.c,v 1.121 2022/12/22 02:52:35 msaitoh Exp $       */
     /*      $KAME: in6_ifattach.c,v 1.124 2001/07/18 08:32:51 jinmei 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_ifattach.c,v 1.121 2022/12/22 02:52:35 msaitoh Exp $");
    
    #include <sys/param.h>
    #include <sys/systm.h>
    #include <sys/kmem.h>
    #include <sys/socket.h>
    #include <sys/sockio.h>
    #include <sys/kernel.h>
    #include <sys/syslog.h>
    #include <sys/md5.h>
    #include <sys/socketvar.h>
    #include <sys/cprng.h>
    
    #include <net/if.h>
    #include <net/if_dl.h>
    #include <net/if_types.h>
    #include <net/route.h>
    
    #include <netinet/in.h>
    #include <netinet/in_var.h>
    
    #include <netinet/ip6.h>
    #include <netinet6/in6_ifattach.h>
    #include <netinet6/ip6_var.h>
    #include <netinet6/nd6.h>
    #include <netinet6/ip6_mroute.h>
    #include <netinet6/scope6_var.h>
    
    int ip6_auto_linklocal = 1;     /* enable by default */
    
    #if 0
    static int get_hostid_ifid(struct ifnet *, struct in6_addr *);
    #endif
    static int get_ifid(struct ifnet *, struct ifnet *, struct in6_addr *);
    static int in6_ifattach_linklocal(struct ifnet *, struct ifnet *);
    static int in6_ifattach_loopback(struct ifnet *);
    
    #define EUI64_GBIT      0x01
    #define EUI64_UBIT      0x02
    #define EUI64_TO_IFID(in6)      do {(in6)->s6_addr[8] ^= EUI64_UBIT; } while (/*CONSTCOND*/ 0)
    #define EUI64_GROUP(in6)        ((in6)->s6_addr[8] & EUI64_GBIT)
    #define EUI64_INDIVIDUAL(in6)   (!EUI64_GROUP(in6))
    #define EUI64_LOCAL(in6)        ((in6)->s6_addr[8] & EUI64_UBIT)
    #define EUI64_UNIVERSAL(in6)    (!EUI64_LOCAL(in6))
    
    #define IFID_LOCAL(in6)         (!EUI64_LOCAL(in6))
    #define IFID_UNIVERSAL(in6)     (!EUI64_UNIVERSAL(in6))
    
    #if 0
    /*
     * Generate a last-resort interface identifier from hostid.
     * works only for certain architectures (like sparc).
     * also, using hostid itself may constitute a privacy threat, much worse
     * than MAC addresses (hostids are used for software licensing).
     * maybe we should use MD5(hostid) instead.
     *
     * in6 - upper 64bits are preserved
     */
    static int
    get_hostid_ifid(struct ifnet *ifp, struct in6_addr *in6)
    {
            int off, len;
            static const uint8_t allzero[8] = { 0, 0, 0, 0, 0, 0, 0, 0 };
            static const uint8_t allone[8] =
                { 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff };
    
           if (!hostid)
                   return -1;
   
           /* get up to 8 bytes from the hostid field - should we get */
           len = (sizeof(hostid) > 8) ? 8 : sizeof(hostid);
           off = sizeof(*in6) - len;
           memcpy(&in6->s6_addr[off], &hostid, len);
   
           /* make sure we do not return anything bogus */
           if (memcmp(&in6->s6_addr[8], allzero, sizeof(allzero)))
                   return -1;
           if (memcmp(&in6->s6_addr[8], allone, sizeof(allone)))
                   return -1;
   
           /* make sure to set "u" bit to local, and "g" bit to individual. */
           in6->s6_addr[8] &= ~EUI64_GBIT; /* g bit to "individual" */
           in6->s6_addr[8] |= EUI64_UBIT;  /* u bit to "local" */
   
           /* convert EUI64 into IPv6 interface identifier */
           EUI64_TO_IFID(in6);
   
           return 0;
   }
   #endif
   
   /*
    * Generate a last-resort interface identifier, when the machine has no
    * IEEE802/EUI64 address sources.
    * The goal here is to get an interface identifier that is
    * (1) random enough and (2) does not change across reboot.
    * We currently use MD5(hostname) for it.
    */
   static int
   get_rand_ifid(struct in6_addr *in6)     /* upper 64bits are preserved */
   {
           MD5_CTX ctxt;
           u_int8_t digest[16];
   
   #if 0
           /* we need at least several letters as seed for ifid */
           if (hostnamelen < 3)
                   return -1;
   #endif
   
           /* generate 8 bytes of pseudo-random value. */
           memset(&ctxt, 0, sizeof(ctxt));
           MD5Init(&ctxt);
           MD5Update(&ctxt, (u_char *)hostname, hostnamelen);
           MD5Final(digest, &ctxt);
   
           /* assumes sizeof(digest) > sizeof(ifid) */
           memcpy(&in6->s6_addr[8], digest, 8);
   
           /* make sure to set "u" bit to local, and "g" bit to individual. */
           in6->s6_addr[8] &= ~EUI64_GBIT; /* g bit to "individual" */
           in6->s6_addr[8] |= EUI64_UBIT;  /* u bit to "local" */
   
           /* convert EUI64 into IPv6 interface identifier */
           EUI64_TO_IFID(in6);
   
           return 0;
   }
   
   /*
    * Get interface identifier for the specified interface.
    *
    * in6 - upper 64bits are preserved
    */
   int
   in6_get_hw_ifid(struct ifnet *ifp, struct in6_addr *in6)
   {
           struct ifaddr *ifa;
           const struct sockaddr_dl *sdl = NULL;
           const char *addr = NULL; /* XXX gcc 4.8 -Werror=maybe-uninitialized */
           size_t addrlen = 0; /* XXX gcc 4.8 -Werror=maybe-uninitialized */
           static u_int8_t allzero[8] = { 0, 0, 0, 0, 0, 0, 0, 0 };
           static u_int8_t allone[8] =
                   { 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff };
           int s;
   
           s = pserialize_read_enter();
           IFADDR_READER_FOREACH(ifa, ifp) {
                   const struct sockaddr_dl *tsdl;
                   if (ifa->ifa_addr->sa_family != AF_LINK)
                           continue;
                   tsdl = satocsdl(ifa->ifa_addr);
                   if (tsdl == NULL || tsdl->sdl_alen == 0)
                           continue;
                   if (sdl == NULL || ifa == ifp->if_dl || ifa == ifp->if_hwdl) {
                           sdl = tsdl;
                           addr = CLLADDR(sdl);
                           addrlen = sdl->sdl_alen;
                   }
                   if (ifa == ifp->if_hwdl)
                           break;
           }
           pserialize_read_exit(s);
   
           if (sdl == NULL)
                   return -1;
   
           switch (ifp->if_type) {
           case IFT_IEEE1394:
           case IFT_IEEE80211:
                   /* IEEE1394 uses 16byte length address starting with EUI64 */
                   if (addrlen > 8)
                           addrlen = 8;
                   break;
           default:
                   break;
           }
   
           /* get EUI64 */
           switch (ifp->if_type) {
           /* IEEE802/EUI64 cases - what others? */
           case IFT_ETHER:
           case IFT_ATM:
           case IFT_IEEE1394:
           case IFT_IEEE80211:
                   /* look at IEEE802/EUI64 only */
                   if (addrlen != 8 && addrlen != 6)
                           return -1;
   
                   /*
                    * check for invalid MAC address - on bsdi, we see it a lot
                    * since wildboar configures all-zero MAC on pccard before
                    * card insertion.
                    */
                   if (memcmp(addr, allzero, addrlen) == 0)
                           return -1;
                   if (memcmp(addr, allone, addrlen) == 0)
                           return -1;
   
                   /* make EUI64 address */
                   if (addrlen == 8)
                           memcpy(&in6->s6_addr[8], addr, 8);
                   else if (addrlen == 6) {
                           in6->s6_addr[8] = addr[0];
                           in6->s6_addr[9] = addr[1];
                           in6->s6_addr[10] = addr[2];
                           in6->s6_addr[11] = 0xff;
                           in6->s6_addr[12] = 0xfe;
                           in6->s6_addr[13] = addr[3];
                           in6->s6_addr[14] = addr[4];
                           in6->s6_addr[15] = addr[5];
                   }
                   break;
   
           case IFT_ARCNET:
                   if (addrlen != 1)
                           return -1;
                   if (!addr[0])
                           return -1;
   
                   memset(&in6->s6_addr[8], 0, 8);
                   in6->s6_addr[15] = addr[0];
   
                   /*
                    * due to insufficient bitwidth, we mark it local.
                    */
                   in6->s6_addr[8] &= ~EUI64_GBIT; /* g bit to "individual" */
                   in6->s6_addr[8] |= EUI64_UBIT;  /* u bit to "local" */
                   break;
   
           case IFT_GIF:
   #ifdef IFT_STF
           case IFT_STF:
   #endif
                   /*
                    * RFC2893 says: "SHOULD use IPv4 address as ifid source".
                    * however, IPv4 address is not very suitable as unique
                    * identifier source (can be renumbered).
                    * we don't do this.
                    */
                   return -1;
   
           default:
                   return -1;
           }
   
           /* sanity check: g bit must not indicate "group" */
           if (EUI64_GROUP(in6))
                   return -1;
   
           /* convert EUI64 into IPv6 interface identifier */
           EUI64_TO_IFID(in6);
   
           /*
            * sanity check: ifid must not be all zero, avoid conflict with
            * subnet router anycast
            */
           if ((in6->s6_addr[8] & ~(EUI64_GBIT | EUI64_UBIT)) == 0x00 &&
               memcmp(&in6->s6_addr[9], allzero, 7) == 0) {
                   return -1;
           }
   
           return 0;
   }
   
   /*
    * Get interface identifier for the specified interface.  If it is not
    * available on ifp0, borrow interface identifier from other information
    * sources.
    *
    * altifp - secondary EUI64 source
    */
   static int
   get_ifid(struct ifnet *ifp0, struct ifnet *altifp, 
           struct in6_addr *in6)
   {
           struct ifnet *ifp;
           int s;
   
           /* first, try to get it from the interface itself */
           if (in6_get_hw_ifid(ifp0, in6) == 0) {
                   nd6log(LOG_DEBUG, "%s: got interface identifier from itself\n",
                       if_name(ifp0));
                   goto success;
           }
   
           /* try secondary EUI64 source. this basically is for ATM PVC */
           if (altifp && in6_get_hw_ifid(altifp, in6) == 0) {
                   nd6log(LOG_DEBUG, "%s: got interface identifier from %s\n",
                       if_name(ifp0), if_name(altifp));
                   goto success;
           }
   
           /* next, try to get it from some other hardware interface */
           s = pserialize_read_enter();
           IFNET_READER_FOREACH(ifp) {
                   if (ifp == ifp0)
                           continue;
                   if (in6_get_hw_ifid(ifp, in6) != 0)
                           continue;
   
                   /*
                    * to borrow ifid from other interface, ifid needs to be
                    * globally unique
                    */
                   if (IFID_UNIVERSAL(in6)) {
                           nd6log(LOG_DEBUG,
                               "%s: borrow interface identifier from %s\n",
                               if_name(ifp0), if_name(ifp));
                           pserialize_read_exit(s);
                           goto success;
                   }
           }
           pserialize_read_exit(s);
   
   #if 0
           /* get from hostid - only for certain architectures */
           if (get_hostid_ifid(ifp, in6) == 0) {
                   nd6log(LOG_DEBUG,
                       "%s: interface identifier generated by hostid\n",
                       if_name(ifp0));
                   goto success;
           }
   #endif
   
           /* last resort: get from random number source */
           if (get_rand_ifid(in6) == 0) {
                   nd6log(LOG_DEBUG,
                       "%s: interface identifier generated by random number\n",
                       if_name(ifp0));
                   goto success;
           }
   
           printf("%s: failed to get interface identifier\n", if_name(ifp0));
           return -1;
   
   success:
           nd6log(LOG_INFO, "%s: ifid: %02x:%02x:%02x:%02x:%02x:%02x:%02x:%02x\n",
               if_name(ifp0), in6->s6_addr[8], in6->s6_addr[9], in6->s6_addr[10],
               in6->s6_addr[11], in6->s6_addr[12], in6->s6_addr[13],
               in6->s6_addr[14], in6->s6_addr[15]);
           return 0;
   }
   
   /*
    * altifp - secondary EUI64 source
    */
   
   static int
   in6_ifattach_linklocal(struct ifnet *ifp, struct ifnet *altifp)
   {
           struct in6_aliasreq ifra;
           int error;
   
           /*
            * configure link-local address.
            */
           memset(&ifra, 0, sizeof(ifra));
   
           /*
            * in6_update_ifa() does not use ifra_name, but we accurately set it
            * for safety.
            */
           strncpy(ifra.ifra_name, if_name(ifp), sizeof(ifra.ifra_name));
   
           ifra.ifra_addr.sin6_family = AF_INET6;
           ifra.ifra_addr.sin6_len = sizeof(struct sockaddr_in6);
           ifra.ifra_addr.sin6_addr.s6_addr32[0] = htonl(0xfe800000);
           ifra.ifra_addr.sin6_addr.s6_addr32[1] = 0;
           if ((ifp->if_flags & IFF_LOOPBACK) != 0) {
                   ifra.ifra_addr.sin6_addr.s6_addr32[2] = 0;
                   ifra.ifra_addr.sin6_addr.s6_addr32[3] = htonl(1);
           } else {
                   if (get_ifid(ifp, altifp, &ifra.ifra_addr.sin6_addr) != 0) {
                           nd6log(LOG_ERR,
                               "%s: no ifid available\n", if_name(ifp));
                           return -1;
                   }
           }
           if (in6_setscope(&ifra.ifra_addr.sin6_addr, ifp, NULL))
                   return -1;
   
           sockaddr_in6_init(&ifra.ifra_prefixmask, &in6mask64, 0, 0, 0);
           /* link-local addresses should NEVER expire. */
           ifra.ifra_lifetime.ia6t_vltime = ND6_INFINITE_LIFETIME;
           ifra.ifra_lifetime.ia6t_pltime = ND6_INFINITE_LIFETIME;
   
           /*
            * Now call in6_update_ifa() to do a bunch of procedures to configure
            * a link-local address. We can set the 3rd argument to NULL, because
            * we know there's no other link-local address on the interface
            * and therefore we are adding one (instead of updating one).
            */
           if ((error = in6_update_ifa(ifp, &ifra, IN6_IFAUPDATE_DADDELAY)) != 0) {
                   /*
                    * XXX: When the interface does not support IPv6, this call
                    * would fail in the SIOCINITIFADDR ioctl.  I believe the
                    * notification is rather confusing in this case, so just
                    * suppress it.  (jinmei@kame.net 20010130)
                    */
                   if (error != EAFNOSUPPORT)
                           nd6log(LOG_NOTICE,
                               "failed to configure a link-local address on %s "
                               "(errno=%d)\n",
                               if_name(ifp), error);
                   return -1;
           }
   
           return 0;
   }
   
   /*
    * ifp - must be IFT_LOOP
    */
   
   static int
   in6_ifattach_loopback(struct ifnet *ifp)
   {
           struct in6_aliasreq ifra;
           int error;
   
           memset(&ifra, 0, sizeof(ifra));
   
           /*
            * in6_update_ifa() does not use ifra_name, but we accurately set it
            * for safety.
            */
           strncpy(ifra.ifra_name, if_name(ifp), sizeof(ifra.ifra_name));
   
           sockaddr_in6_init(&ifra.ifra_prefixmask, &in6mask128, 0, 0, 0);
   
           /*
            * Always initialize ia_dstaddr (= broadcast address) to loopback
            * address.  Follows IPv4 practice - see in_ifinit().
            */
           sockaddr_in6_init(&ifra.ifra_dstaddr, &in6addr_loopback, 0, 0, 0);
   
           sockaddr_in6_init(&ifra.ifra_addr, &in6addr_loopback, 0, 0, 0);
   
           /* the loopback  address should NEVER expire. */
           ifra.ifra_lifetime.ia6t_vltime = ND6_INFINITE_LIFETIME;
           ifra.ifra_lifetime.ia6t_pltime = ND6_INFINITE_LIFETIME;
   
           /* we don't need to perform DAD on loopback interfaces. */
           ifra.ifra_flags |= IN6_IFF_NODAD;
   
           /*
            * We are sure that this is a newly assigned address, so we can set
            * NULL to the 3rd arg.
            */
           if ((error = in6_update_ifa(ifp, &ifra, 0)) != 0) {
                   nd6log(LOG_ERR, "failed to configure "
                       "the loopback address on %s (errno=%d)\n",
                       if_name(ifp), error);
                   return -1;
           }
   
           return 0;
   }
   
   /*
    * compute NI group address, based on the current hostname setting.
    * see draft-ietf-ipngwg-icmp-name-lookup-* (04 and later).
    *
    * when ifp == NULL, the caller is responsible for filling scopeid.
    */
   int
   in6_nigroup(struct ifnet *ifp, const char *name, int namelen, 
           struct sockaddr_in6 *sa6)
   {
           const char *p;
           u_int8_t *q;
           MD5_CTX ctxt;
           u_int8_t digest[16];
           u_int8_t l;
           u_int8_t n[64]; /* a single label must not exceed 63 chars */
   
           if (!namelen || !name)
                   return -1;
   
           p = name;
           while (p && *p && *p != '.' && p - name < namelen)
                   p++;
           if (p - name > sizeof(n) - 1)
                   return -1;      /* label too long */
           l = p - name;
           strncpy((char *)n, name, l);
           n[(int)l] = '\0';
           for (q = n; *q; q++) {
                   if ('A' <= *q && *q <= 'Z')
                           *q = *q - 'A' + 'a';
           }
   
           /* generate 8 bytes of pseudo-random value. */
           memset(&ctxt, 0, sizeof(ctxt));
           MD5Init(&ctxt);
           MD5Update(&ctxt, &l, sizeof(l));
           MD5Update(&ctxt, n, l);
           MD5Final(digest, &ctxt);
   
           memset(sa6, 0, sizeof(*sa6));
           sa6->sin6_family = AF_INET6;
           sa6->sin6_len = sizeof(*sa6);
           sa6->sin6_addr.s6_addr16[0] = htons(0xff02);
           sa6->sin6_addr.s6_addr8[11] = 2;
           memcpy(&sa6->sin6_addr.s6_addr32[3], digest,
               sizeof(sa6->sin6_addr.s6_addr32[3]));
           if (in6_setscope(&sa6->sin6_addr, ifp, NULL))
                   return -1; /* XXX: should not fail */
   
           return 0;
   }
   
   /*
    * XXX multiple loopback interface needs more care.  for instance,
    * nodelocal address needs to be configured onto only one of them.
    * XXX multiple link-local address case
    *
    * altifp - secondary EUI64 source
    */
   void
   in6_ifattach(struct ifnet *ifp, struct ifnet *altifp)
   {
           struct in6_ifaddr *ia;
           struct in6_addr in6;
   
           KASSERT(IFNET_LOCKED(ifp));
   
           /* some of the interfaces are inherently not IPv6 capable */
           switch (ifp->if_type) {
           case IFT_BRIDGE:
           case IFT_L2TP:
           case IFT_IEEE8023ADLAG:
   #ifdef IFT_PFLOG
           case IFT_PFLOG:
   #endif
   #ifdef IFT_PFSYNC
           case IFT_PFSYNC:
   #endif
                   ND_IFINFO(ifp)->flags &= ~ND6_IFF_AUTO_LINKLOCAL;
                   ND_IFINFO(ifp)->flags |= ND6_IFF_IFDISABLED;
                   return;
           }
   
           /*
            * if link mtu is too small, don't try to configure IPv6.
            * remember there could be some link-layer that has special
            * fragmentation logic.
            */
           if (ifp->if_mtu < IPV6_MMTU) {
                   nd6log(LOG_INFO, "%s has too small MTU, IPv6 not enabled\n",
                       if_name(ifp));
                   return;
           }
   
           /*
            * quirks based on interface type
            */
           switch (ifp->if_type) {
   #ifdef IFT_STF
           case IFT_STF:
                   /*
                    * 6to4 interface is a very special kind of beast.
                    * no multicast, no linklocal.  RFC2529 specifies how to make
                    * linklocals for 6to4 interface, but there's no use and
                    * it is rather harmful to have one.
                    */
                   ND_IFINFO(ifp)->flags &= ~ND6_IFF_AUTO_LINKLOCAL;
                   return;
   #endif
           case IFT_CARP:
                   return;
           default:
                   break;
           }
   
           /*
            * usually, we require multicast capability to the interface
            */
           if ((ifp->if_flags & IFF_MULTICAST) == 0) {
                   nd6log(LOG_INFO,
                       "%s is not multicast capable, IPv6 not enabled\n",
                       if_name(ifp));
                   return;
           }
   
           /*
            * assign loopback address for loopback interface.
            * XXX multiple loopback interface case.
            */
           if ((ifp->if_flags & IFF_LOOPBACK) != 0) {
                   in6 = in6addr_loopback;
                   /* These are safe and atomic thanks to IFNET_LOCK */
                   if (in6ifa_ifpwithaddr(ifp, &in6) == NULL) {
                           if (in6_ifattach_loopback(ifp) != 0)
                                   return;
                   }
           }
   
           /*
            * assign a link-local address, if there's none.
            */
           if (!(ND_IFINFO(ifp)->flags & ND6_IFF_IFDISABLED) &&
               ND_IFINFO(ifp)->flags & ND6_IFF_AUTO_LINKLOCAL) {
                   int bound = curlwp_bind();
                   struct psref psref;
                   ia = in6ifa_ifpforlinklocal_psref(ifp, 0, &psref);
                   if (ia == NULL && in6_ifattach_linklocal(ifp, altifp) != 0) {
                           printf("%s: cannot assign link-local address\n",
                               ifp->if_xname);
                   }
                   ia6_release(ia, &psref);
                   curlwp_bindx(bound);
           }
   }
   
   /*
    * NOTE: in6_ifdetach() does not support loopback if at this moment.
    * We don't need this function in bsdi, because interfaces are never removed
    * from the ifnet list in bsdi.
    */
   void
   in6_ifdetach(struct ifnet *ifp)
   {
   
           /* nuke any of IPv6 addresses we have */
           if_purgeaddrs(ifp, AF_INET6, in6_purgeaddr);
   
           in6_purge_multi(ifp);
   
           /* remove ip6_mrouter stuff */
           ip6_mrouter_detach(ifp);
   
           /* remove neighbor management table */
           nd6_purge(ifp, NULL);
   }

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