1 /* 2 * IPv6 library code, needed by static components when full IPv6 support is 3 * not configured or static. 4 */ 5 #include <linux/export.h> 6 #include <net/ipv6.h> 7 8 /* 9 * find out if nexthdr is a well-known extension header or a protocol 10 */ 11 12 int ipv6_ext_hdr(u8 nexthdr) 13 { 14 /* 15 * find out if nexthdr is an extension header or a protocol 16 */ 17 return (nexthdr == NEXTHDR_HOP) || 18 (nexthdr == NEXTHDR_ROUTING) || 19 (nexthdr == NEXTHDR_FRAGMENT) || 20 (nexthdr == NEXTHDR_AUTH) || 21 (nexthdr == NEXTHDR_NONE) || 22 (nexthdr == NEXTHDR_DEST); 23 } 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: 29 * ...The contents and semantics of each extension header determine whether 30 * 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. 35 * 36 * We do exactly this. This is a protocol bug. We can't decide after a 37 * seeing an unknown discard-with-error flavour TLV option if it's a 38 * ICMP error message or not (errors should never be send in reply to 39 * ICMP error messages). 40 * 41 * 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 * 45 * This function parses (probably truncated) exthdr set "hdr". 46 * "nexthdrp" initially points to some place, 47 * 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. 60 * - 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. 63 * - 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 70 int ipv6_skip_exthdr(const struct sk_buff *skb, int start, u8 *nexthdrp, 71 __be16 *frag_offp) 72 { 73 u8 nexthdr = *nexthdrp; 74 75 *frag_offp = 0; 76 77 while (ipv6_ext_hdr(nexthdr)) { 78 struct ipv6_opt_hdr _hdr, *hp; 79 int hdrlen; 80 81 if (nexthdr == NEXTHDR_NONE) 82 return -1; 83 hp = skb_header_pointer(skb, start, sizeof(_hdr), &_hdr); 84 if (hp == NULL) 85 return -1; 86 if (nexthdr == NEXTHDR_FRAGMENT) { 87 __be16 _frag_off, *fp; 88 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 96 *frag_offp = *fp; 97 if (ntohs(*frag_offp) & ~0x7) 98 break; 99 hdrlen = 8; 100 } else if (nexthdr == NEXTHDR_AUTH) 101 hdrlen = (hp->hdrlen+2)<<2; 102 else 103 hdrlen = ipv6_optlen(hp); 104 105 nexthdr = hp->nexthdr; 106 start += hdrlen; 107 } 108 109 *nexthdrp = nexthdr; 110 return start; 111 } 112 113 EXPORT_SYMBOL(ipv6_ext_hdr); 114 EXPORT_SYMBOL(ipv6_skip_exthdr); 115