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 * - ESP is unparsable for now and considered like 61 * normal payload protocol. 62 * - Note also special handling of AUTH header. Thanks to IPsec wizards. 63 * 64 * --ANK (980726) 65 */ 66 67 int ipv6_skip_exthdr(const struct sk_buff *skb, int start, u8 *nexthdrp) 68 { 69 u8 nexthdr = *nexthdrp; 70 71 while (ipv6_ext_hdr(nexthdr)) { 72 struct ipv6_opt_hdr _hdr, *hp; 73 int hdrlen; 74 75 if (nexthdr == NEXTHDR_NONE) 76 return -1; 77 hp = skb_header_pointer(skb, start, sizeof(_hdr), &_hdr); 78 if (hp == NULL) 79 return -1; 80 if (nexthdr == NEXTHDR_FRAGMENT) { 81 __be16 _frag_off, *fp; 82 fp = skb_header_pointer(skb, 83 start+offsetof(struct frag_hdr, 84 frag_off), 85 sizeof(_frag_off), 86 &_frag_off); 87 if (fp == NULL) 88 return -1; 89 90 if (ntohs(*fp) & ~0x7) 91 break; 92 hdrlen = 8; 93 } else if (nexthdr == NEXTHDR_AUTH) 94 hdrlen = (hp->hdrlen+2)<<2; 95 else 96 hdrlen = ipv6_optlen(hp); 97 98 nexthdr = hp->nexthdr; 99 start += hdrlen; 100 } 101 102 *nexthdrp = nexthdr; 103 return start; 104 } 105 106 EXPORT_SYMBOL(ipv6_ext_hdr); 107 EXPORT_SYMBOL(ipv6_skip_exthdr); 108