Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/sparc-2.6
[linux-2.6.git] / net / ipv6 / exthdrs_core.c
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
11 int 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
66 int 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
105 EXPORT_SYMBOL(ipv6_ext_hdr);
106 EXPORT_SYMBOL(ipv6_skip_exthdr);