Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame] | 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 | * of length "len". "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, int len) |
| 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 (len < (int)sizeof(struct ipv6_opt_hdr)) |
| 75 | return -1; |
| 76 | if (nexthdr == NEXTHDR_NONE) |
| 77 | return -1; |
| 78 | hp = skb_header_pointer(skb, start, sizeof(_hdr), &_hdr); |
| 79 | if (hp == NULL) |
| 80 | BUG(); |
| 81 | if (nexthdr == NEXTHDR_FRAGMENT) { |
| 82 | unsigned short _frag_off, *fp; |
| 83 | fp = skb_header_pointer(skb, |
| 84 | start+offsetof(struct frag_hdr, |
| 85 | frag_off), |
| 86 | sizeof(_frag_off), |
| 87 | &_frag_off); |
| 88 | if (fp == NULL) |
| 89 | return -1; |
| 90 | |
| 91 | if (ntohs(*fp) & ~0x7) |
| 92 | break; |
| 93 | hdrlen = 8; |
| 94 | } else if (nexthdr == NEXTHDR_AUTH) |
| 95 | hdrlen = (hp->hdrlen+2)<<2; |
| 96 | else |
| 97 | hdrlen = ipv6_optlen(hp); |
| 98 | |
| 99 | nexthdr = hp->nexthdr; |
| 100 | len -= hdrlen; |
| 101 | start += hdrlen; |
| 102 | } |
| 103 | |
| 104 | *nexthdrp = nexthdr; |
| 105 | return start; |
| 106 | } |
| 107 | |
| 108 | EXPORT_SYMBOL(ipv6_ext_hdr); |
| 109 | EXPORT_SYMBOL(ipv6_skip_exthdr); |