/*
   * IPv6 library code, needed by static components when full IPv6 support is
   * not configured or static.
   */

  #include <linux/export.h>

  #include <net/ipv6.h>

  /*

   * find out if nexthdr is a well-known extension header or a protocol
   */
  
  int ipv6_ext_hdr(u8 nexthdr)
  {

  	/*

  	 * find out if nexthdr is an extension header or a protocol
  	 */

  	return   (nexthdr == NEXTHDR_HOP)	||

  		 (nexthdr == NEXTHDR_ROUTING)	||
  		 (nexthdr == NEXTHDR_FRAGMENT)	||
  		 (nexthdr == NEXTHDR_AUTH)	||
  		 (nexthdr == NEXTHDR_NONE)	||

  		 (nexthdr == NEXTHDR_DEST);

  }
  
  /*
   * Skip any extension headers. This is used by the ICMP module.
   *
   * Note that strictly speaking this conflicts with RFC 2460 4.0:

   * ...The contents and semantics of each extension header determine whether

   * or not to proceed to the next header.  Therefore, extension headers must
   * be processed strictly in the order they appear in the packet; a
   * receiver must not, for example, scan through a packet looking for a
   * particular kind of extension header and process that header prior to
   * processing all preceding ones.

   *

   * We do exactly this. This is a protocol bug. We can't decide after a

   * seeing an unknown discard-with-error flavour TLV option if it's a

   * ICMP error message or not (errors should never be send in reply to
   * ICMP error messages).

   *

   * But I see no other way to do this. This might need to be reexamined
   * when Linux implements ESP (and maybe AUTH) headers.
   * --AK
   *

   * This function parses (probably truncated) exthdr set "hdr".
   * "nexthdrp" initially points to some place,

   * where type of the first header can be found.
   *
   * It skips all well-known exthdrs, and returns pointer to the start
   * of unparsable area i.e. the first header with unknown type.
   * If it is not NULL *nexthdr is updated by type/protocol of this header.
   *
   * NOTES: - if packet terminated with NEXTHDR_NONE it returns NULL.
   *        - it may return pointer pointing beyond end of packet,
   *	    if the last recognized header is truncated in the middle.
   *        - if packet is truncated, so that all parsed headers are skipped,
   *	    it returns NULL.
   *	  - First fragment header is skipped, not-first ones
   *	    are considered as unparsable.

   *	  - Reports the offset field of the final fragment header so it is
   *	    possible to tell whether this is a first fragment, later fragment,
   *	    or not fragmented.

   *	  - ESP is unparsable for now and considered like
   *	    normal payload protocol.
   *	  - Note also special handling of AUTH header. Thanks to IPsec wizards.
   *
   * --ANK (980726)
   */

  int ipv6_skip_exthdr(const struct sk_buff *skb, int start, u8 *nexthdrp,
  		     __be16 *frag_offp)

  {
  	u8 nexthdr = *nexthdrp;

  	*frag_offp = 0;

  	while (ipv6_ext_hdr(nexthdr)) {
  		struct ipv6_opt_hdr _hdr, *hp;
  		int hdrlen;

  		if (nexthdr == NEXTHDR_NONE)
  			return -1;
  		hp = skb_header_pointer(skb, start, sizeof(_hdr), &_hdr);
  		if (hp == NULL)

  			return -1;

  		if (nexthdr == NEXTHDR_FRAGMENT) {

  			__be16 _frag_off, *fp;

  			fp = skb_header_pointer(skb,
  						start+offsetof(struct frag_hdr,
  							       frag_off),
  						sizeof(_frag_off),
  						&_frag_off);
  			if (fp == NULL)
  				return -1;

  			*frag_offp = *fp;
  			if (ntohs(*frag_offp) & ~0x7)

  				break;
  			hdrlen = 8;
  		} else if (nexthdr == NEXTHDR_AUTH)

  			hdrlen = (hp->hdrlen+2)<<2;

  		else

  			hdrlen = ipv6_optlen(hp);

  
  		nexthdr = hp->nexthdr;

  		start += hdrlen;
  	}
  
  	*nexthdrp = nexthdr;
  	return start;
  }
  
  EXPORT_SYMBOL(ipv6_ext_hdr);
  EXPORT_SYMBOL(ipv6_skip_exthdr);