@@ -888,6 +888,13 @@ do_ifconfig (struct tuntap *tt,

 #elif defined(TARGET_NETBSD)

+/* whether or not NetBSD can do IPv6 can be seen by the availability of

+ * the TUNSIFHEAD ioctl() - see next TARGET_NETBSD block for more details

+ */

+#ifdef TUNSIFHEAD

+# define NETBSD_MULTI_AF

+#endif

+

       /* as on OpenBSD and Darwin, destroy and re-create tun0 interface

        */

       argv_printf (&argv, "%s %s destroy", IFCONFIG_PATH, actual );

@@ -922,6 +929,7 @@ do_ifconfig (struct tuntap *tt,

       if ( do_ipv6 )

 	{

+#ifdef NETBSD_MULTI_AF

 	  struct route_ipv6 r6;

 	  argv_printf (&argv,

 			  "%s %s inet6 %s/%d",

@@ -939,6 +947,10 @@ do_ifconfig (struct tuntap *tt,

 	  r6.netbits = tt->netbits_ipv6;

 	  r6.gateway = tt->local_ipv6;

 	  add_route_ipv6 (&r6, tt, 0, es);

+#else

+	  msg( M_INFO, "no IPv6 support for tun interfaces on NetBSD before 4.0 (if your system is newer, recompile openvpn)" );

+	  tt->ipv6 = false;

+#endif

 	}

       tt->did_ifconfig = true;

@@ -1951,46 +1963,39 @@ read_tun (struct tuntap* tt, uint8_t *buf, int len)

  * NetBSD before 4.0 does not support IPv6 on tun out of the box,

  * but there exists a patch (sys/net/if_tun.c, 1.79->1.80, see PR 32944).

  *

- * When this patch is applied, only two things are left to openvpn:

- * 1. Activate multicasting (this has already been done

- *    before by the kernel, but we make sure that nobody

- *    has deactivated multicasting inbetween.

- * 2. Deactivate "link layer mode" (otherwise NetBSD 

- *    prepends the address family to the packet, and we

- *    would run into the same trouble as with OpenBSD.

+ * NetBSD 4.0 and up do, but we need to put the tun interface into

+ * "multi_af" mode, which will prepend the address family to all packets

+ * (same as OpenBSD and FreeBSD).  If this is not enabled, the kernel

+ * silently drops all IPv6 packets on output and gets confused on input.

  *

- * ... unfortunately, it doesn't work that way.  If TUN_IFHEAD is disabled

- * ("no prepending of the AF"), then the kernel code just drops IPv6 packets

- * on output, and gets confused on input.

+ * On earlier versions, multi_af is not available at all, so we have

+ * two different NetBSD code variants here :-(

  *

- * So we have to do it the same way as FreeBSD and OpenBSD do it 

- * (and we really should merge FreeBSD, NetBSD and OpenBSD together)

  */

-static inline int

-netbsd_modify_read_write_return (int len)

-{

-  if (len > 0)

-    return len > sizeof (u_int32_t) ? len - sizeof (u_int32_t) : 0;

-  else

-    return len;

-}

-

 void

 open_tun (const char *dev, const char *dev_type, const char *dev_node, bool ipv6, struct tuntap *tt)

 {

+#ifdef NETBSD_MULTI_AF

     open_tun_generic (dev, dev_type, dev_node, ipv6, true, true, tt);

+#else

+    open_tun_generic (dev, dev_type, dev_node, ipv6, false, true, tt);

+#endif

+

     if (tt->fd >= 0)

       {

         int i = IFF_POINTOPOINT|IFF_MULTICAST;

         ioctl (tt->fd, TUNSIFMODE, &i);  /* multicast on */

         i = 0;

         ioctl (tt->fd, TUNSLMODE, &i);   /* link layer mode off */

+

+#ifdef NETBSD_MULTI_AF

         i = 1;

         if (ioctl (tt->fd, TUNSIFHEAD, &i) < 0) 	/* multi-af mode on */

 	  {

 	    msg (M_WARN | M_ERRNO, "ioctl(TUNSIFHEAD): %s", strerror(errno));

 	  }

+#endif

       }

 }

@@ -2007,6 +2012,17 @@ close_tun (struct tuntap *tt)

     }

 }

+#ifdef NETBSD_MULTI_AF

+

+static inline int

+netbsd_modify_read_write_return (int len)

+{

+  if (len > 0)

+    return len > sizeof (u_int32_t) ? len - sizeof (u_int32_t) : 0;

+  else

+    return len;

+}

+

 int

 write_tun (struct tuntap* tt, uint8_t *buf, int len)

 {

@@ -2053,6 +2069,21 @@ read_tun (struct tuntap* tt, uint8_t *buf, int len)

     return read (tt->fd, buf, len);

 }

+#else	/* not NETBSD_MULTI_AF -> older code, IPv4 only */

+

+int

+write_tun (struct tuntap* tt, uint8_t *buf, int len)

+{

+    return write (tt->fd, buf, len);

+}

+

+int

+read_tun (struct tuntap* tt, uint8_t *buf, int len)

+{

+    return read (tt->fd, buf, len);

+}

+#endif	/* NETBSD_MULTI_AF */

+

 #elif defined(TARGET_FREEBSD)

 static inline int