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); 107