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Linus Torvalds1da177e2005-04-16 15:20:36 -07001/*
2 * IPv6 library code, needed by static components when full IPv6 support is
3 * not configured or static.
4 */
Paul Gortmakerbc3b2d72011-07-15 11:47:34 -04005#include <linux/export.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -07006#include <net/ipv6.h>
7
YOSHIFUJI Hideaki1ab14572007-02-09 23:24:49 +09008/*
Linus Torvalds1da177e2005-04-16 15:20:36 -07009 * find out if nexthdr is a well-known extension header or a protocol
10 */
11
12int ipv6_ext_hdr(u8 nexthdr)
13{
YOSHIFUJI Hideaki1ab14572007-02-09 23:24:49 +090014 /*
Linus Torvalds1da177e2005-04-16 15:20:36 -070015 * find out if nexthdr is an extension header or a protocol
16 */
Eric Dumazeta02cec22010-09-22 20:43:57 +000017 return (nexthdr == NEXTHDR_HOP) ||
Linus Torvalds1da177e2005-04-16 15:20:36 -070018 (nexthdr == NEXTHDR_ROUTING) ||
19 (nexthdr == NEXTHDR_FRAGMENT) ||
20 (nexthdr == NEXTHDR_AUTH) ||
21 (nexthdr == NEXTHDR_NONE) ||
Eric Dumazeta02cec22010-09-22 20:43:57 +000022 (nexthdr == NEXTHDR_DEST);
Linus Torvalds1da177e2005-04-16 15:20:36 -070023}
24
25/*
26 * Skip any extension headers. This is used by the ICMP module.
27 *
28 * Note that strictly speaking this conflicts with RFC 2460 4.0:
YOSHIFUJI Hideaki1ab14572007-02-09 23:24:49 +090029 * ...The contents and semantics of each extension header determine whether
Linus Torvalds1da177e2005-04-16 15:20:36 -070030 * or not to proceed to the next header. Therefore, extension headers must
31 * be processed strictly in the order they appear in the packet; a
32 * receiver must not, for example, scan through a packet looking for a
33 * particular kind of extension header and process that header prior to
34 * processing all preceding ones.
YOSHIFUJI Hideaki1ab14572007-02-09 23:24:49 +090035 *
Linus Torvalds1da177e2005-04-16 15:20:36 -070036 * We do exactly this. This is a protocol bug. We can't decide after a
YOSHIFUJI Hideaki1ab14572007-02-09 23:24:49 +090037 * seeing an unknown discard-with-error flavour TLV option if it's a
Linus Torvalds1da177e2005-04-16 15:20:36 -070038 * ICMP error message or not (errors should never be send in reply to
39 * ICMP error messages).
YOSHIFUJI Hideaki1ab14572007-02-09 23:24:49 +090040 *
Linus Torvalds1da177e2005-04-16 15:20:36 -070041 * But I see no other way to do this. This might need to be reexamined
42 * when Linux implements ESP (and maybe AUTH) headers.
43 * --AK
44 *
Herbert Xu0d3d0772005-04-24 20:16:19 -070045 * This function parses (probably truncated) exthdr set "hdr".
46 * "nexthdrp" initially points to some place,
Linus Torvalds1da177e2005-04-16 15:20:36 -070047 * where type of the first header can be found.
48 *
49 * It skips all well-known exthdrs, and returns pointer to the start
50 * of unparsable area i.e. the first header with unknown type.
51 * If it is not NULL *nexthdr is updated by type/protocol of this header.
52 *
53 * NOTES: - if packet terminated with NEXTHDR_NONE it returns NULL.
54 * - it may return pointer pointing beyond end of packet,
55 * if the last recognized header is truncated in the middle.
56 * - if packet is truncated, so that all parsed headers are skipped,
57 * it returns NULL.
58 * - First fragment header is skipped, not-first ones
59 * are considered as unparsable.
Jesse Gross75f28112011-11-30 17:05:51 -080060 * - Reports the offset field of the final fragment header so it is
61 * possible to tell whether this is a first fragment, later fragment,
62 * or not fragmented.
Linus Torvalds1da177e2005-04-16 15:20:36 -070063 * - ESP is unparsable for now and considered like
64 * normal payload protocol.
65 * - Note also special handling of AUTH header. Thanks to IPsec wizards.
66 *
67 * --ANK (980726)
68 */
69
Jesse Gross75f28112011-11-30 17:05:51 -080070int ipv6_skip_exthdr(const struct sk_buff *skb, int start, u8 *nexthdrp,
71 __be16 *frag_offp)
Linus Torvalds1da177e2005-04-16 15:20:36 -070072{
73 u8 nexthdr = *nexthdrp;
74
Jesse Gross75f28112011-11-30 17:05:51 -080075 *frag_offp = 0;
76
Linus Torvalds1da177e2005-04-16 15:20:36 -070077 while (ipv6_ext_hdr(nexthdr)) {
78 struct ipv6_opt_hdr _hdr, *hp;
79 int hdrlen;
80
Linus Torvalds1da177e2005-04-16 15:20:36 -070081 if (nexthdr == NEXTHDR_NONE)
82 return -1;
83 hp = skb_header_pointer(skb, start, sizeof(_hdr), &_hdr);
84 if (hp == NULL)
Herbert Xu0d3d0772005-04-24 20:16:19 -070085 return -1;
Linus Torvalds1da177e2005-04-16 15:20:36 -070086 if (nexthdr == NEXTHDR_FRAGMENT) {
Al Viroe69a4ad2006-11-14 20:56:00 -080087 __be16 _frag_off, *fp;
Linus Torvalds1da177e2005-04-16 15:20:36 -070088 fp = skb_header_pointer(skb,
89 start+offsetof(struct frag_hdr,
90 frag_off),
91 sizeof(_frag_off),
92 &_frag_off);
93 if (fp == NULL)
94 return -1;
95
Jesse Gross75f28112011-11-30 17:05:51 -080096 *frag_offp = *fp;
97 if (ntohs(*frag_offp) & ~0x7)
Linus Torvalds1da177e2005-04-16 15:20:36 -070098 break;
99 hdrlen = 8;
100 } else if (nexthdr == NEXTHDR_AUTH)
YOSHIFUJI Hideaki1ab14572007-02-09 23:24:49 +0900101 hdrlen = (hp->hdrlen+2)<<2;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700102 else
YOSHIFUJI Hideaki1ab14572007-02-09 23:24:49 +0900103 hdrlen = ipv6_optlen(hp);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700104
105 nexthdr = hp->nexthdr;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700106 start += hdrlen;
107 }
108
109 *nexthdrp = nexthdr;
110 return start;
111}
112
113EXPORT_SYMBOL(ipv6_ext_hdr);
114EXPORT_SYMBOL(ipv6_skip_exthdr);