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 bool 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 EXPORT_SYMBOL(ipv6_ext_hdr); 25 26 /* 27 * Skip any extension headers. This is used by the ICMP module. 28 * 29 * Note that strictly speaking this conflicts with RFC 2460 4.0: 30 * ...The contents and semantics of each extension header determine whether 31 * or not to proceed to the next header. Therefore, extension headers must 32 * be processed strictly in the order they appear in the packet; a 33 * receiver must not, for example, scan through a packet looking for a 34 * particular kind of extension header and process that header prior to 35 * processing all preceding ones. 36 * 37 * We do exactly this. This is a protocol bug. We can't decide after a 38 * seeing an unknown discard-with-error flavour TLV option if it's a 39 * ICMP error message or not (errors should never be send in reply to 40 * ICMP error messages). 41 * 42 * But I see no other way to do this. This might need to be reexamined 43 * when Linux implements ESP (and maybe AUTH) headers. 44 * --AK 45 * 46 * This function parses (probably truncated) exthdr set "hdr". 47 * "nexthdrp" initially points to some place, 48 * where type of the first header can be found. 49 * 50 * It skips all well-known exthdrs, and returns pointer to the start 51 * of unparsable area i.e. the first header with unknown type. 52 * If it is not NULL *nexthdr is updated by type/protocol of this header. 53 * 54 * NOTES: - if packet terminated with NEXTHDR_NONE it returns NULL. 55 * - it may return pointer pointing beyond end of packet, 56 * if the last recognized header is truncated in the middle. 57 * - if packet is truncated, so that all parsed headers are skipped, 58 * it returns NULL. 59 * - First fragment header is skipped, not-first ones 60 * are considered as unparsable. 61 * - Reports the offset field of the final fragment header so it is 62 * possible to tell whether this is a first fragment, later fragment, 63 * or not fragmented. 64 * - ESP is unparsable for now and considered like 65 * normal payload protocol. 66 * - Note also special handling of AUTH header. Thanks to IPsec wizards. 67 * 68 * --ANK (980726) 69 */ 70 71 int ipv6_skip_exthdr(const struct sk_buff *skb, int start, u8 *nexthdrp, 72 __be16 *frag_offp) 73 { 74 u8 nexthdr = *nexthdrp; 75 76 *frag_offp = 0; 77 78 while (ipv6_ext_hdr(nexthdr)) { 79 struct ipv6_opt_hdr _hdr, *hp; 80 int hdrlen; 81 82 if (nexthdr == NEXTHDR_NONE) 83 return -1; 84 hp = skb_header_pointer(skb, start, sizeof(_hdr), &_hdr); 85 if (hp == NULL) 86 return -1; 87 if (nexthdr == NEXTHDR_FRAGMENT) { 88 __be16 _frag_off, *fp; 89 fp = skb_header_pointer(skb, 90 start+offsetof(struct frag_hdr, 91 frag_off), 92 sizeof(_frag_off), 93 &_frag_off); 94 if (fp == NULL) 95 return -1; 96 97 *frag_offp = *fp; 98 if (ntohs(*frag_offp) & ~0x7) 99 break; 100 hdrlen = 8; 101 } else if (nexthdr == NEXTHDR_AUTH) 102 hdrlen = (hp->hdrlen+2)<<2; 103 else 104 hdrlen = ipv6_optlen(hp); 105 106 nexthdr = hp->nexthdr; 107 start += hdrlen; 108 } 109 110 *nexthdrp = nexthdr; 111 return start; 112 } 113 EXPORT_SYMBOL(ipv6_skip_exthdr); 114