1/*
2 * IPv6 library code, needed by static components when full IPv6 support is
3 * not configured or static.
4 */
5#include <net/ipv6.h>
6
7/*
8 * find out if nexthdr is a well-known extension header or a protocol
9 */
10
11int ipv6_ext_hdr(u8 nexthdr)
12{
13	/*
14	 * find out if nexthdr is an extension header or a protocol
15	 */
16	return ( (nexthdr == NEXTHDR_HOP)	||
17		 (nexthdr == NEXTHDR_ROUTING)	||
18		 (nexthdr == NEXTHDR_FRAGMENT)	||
19		 (nexthdr == NEXTHDR_AUTH)	||
20		 (nexthdr == NEXTHDR_NONE)	||
21		 (nexthdr == NEXTHDR_DEST) );
22}
23
24/*
25 * Skip any extension headers. This is used by the ICMP module.
26 *
27 * Note that strictly speaking this conflicts with RFC 2460 4.0:
28 * ...The contents and semantics of each extension header determine whether
29 * or not to proceed to the next header.  Therefore, extension headers must
30 * be processed strictly in the order they appear in the packet; a
31 * receiver must not, for example, scan through a packet looking for a
32 * particular kind of extension header and process that header prior to
33 * processing all preceding ones.
34 *
35 * We do exactly this. This is a protocol bug. We can't decide after a
36 * seeing an unknown discard-with-error flavour TLV option if it's a
37 * ICMP error message or not (errors should never be send in reply to
38 * ICMP error messages).
39 *
40 * But I see no other way to do this. This might need to be reexamined
41 * when Linux implements ESP (and maybe AUTH) headers.
42 * --AK
43 *
44 * This function parses (probably truncated) exthdr set "hdr".
45 * "nexthdrp" initially points to some place,
46 * where type of the first header can be found.
47 *
48 * It skips all well-known exthdrs, and returns pointer to the start
49 * of unparsable area i.e. the first header with unknown type.
50 * If it is not NULL *nexthdr is updated by type/protocol of this header.
51 *
52 * NOTES: - if packet terminated with NEXTHDR_NONE it returns NULL.
53 *        - it may return pointer pointing beyond end of packet,
54 *	    if the last recognized header is truncated in the middle.
55 *        - if packet is truncated, so that all parsed headers are skipped,
56 *	    it returns NULL.
57 *	  - First fragment header is skipped, not-first ones
58 *	    are considered as unparsable.
59 *	  - ESP is unparsable for now and considered like
60 *	    normal payload protocol.
61 *	  - Note also special handling of AUTH header. Thanks to IPsec wizards.
62 *
63 * --ANK (980726)
64 */
65
66int ipv6_skip_exthdr(const struct sk_buff *skb, int start, u8 *nexthdrp)
67{
68	u8 nexthdr = *nexthdrp;
69
70	while (ipv6_ext_hdr(nexthdr)) {
71		struct ipv6_opt_hdr _hdr, *hp;
72		int hdrlen;
73
74		if (nexthdr == NEXTHDR_NONE)
75			return -1;
76		hp = skb_header_pointer(skb, start, sizeof(_hdr), &_hdr);
77		if (hp == NULL)
78			return -1;
79		if (nexthdr == NEXTHDR_FRAGMENT) {
80			__be16 _frag_off, *fp;
81			fp = skb_header_pointer(skb,
82						start+offsetof(struct frag_hdr,
83							       frag_off),
84						sizeof(_frag_off),
85						&_frag_off);
86			if (fp == NULL)
87				return -1;
88
89			if (ntohs(*fp) & ~0x7)
90				break;
91			hdrlen = 8;
92		} else if (nexthdr == NEXTHDR_AUTH)
93			hdrlen = (hp->hdrlen+2)<<2;
94		else
95			hdrlen = ipv6_optlen(hp);
96
97		nexthdr = hp->nexthdr;
98		start += hdrlen;
99	}
100
101	*nexthdrp = nexthdr;
102	return start;
103}
104
105EXPORT_SYMBOL(ipv6_ext_hdr);
106EXPORT_SYMBOL(ipv6_skip_exthdr);
107