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280 lines
7.5 KiB
280 lines
7.5 KiB
// SPDX-License-Identifier: GPL-2.0-only |
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/* |
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* IPv6 library code, needed by static components when full IPv6 support is |
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* not configured or static. |
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*/ |
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#include <linux/export.h> |
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#include <net/ipv6.h> |
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/* |
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* find out if nexthdr is a well-known extension header or a protocol |
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*/ |
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bool ipv6_ext_hdr(u8 nexthdr) |
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{ |
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/* |
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* find out if nexthdr is an extension header or a protocol |
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*/ |
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return (nexthdr == NEXTHDR_HOP) || |
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(nexthdr == NEXTHDR_ROUTING) || |
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(nexthdr == NEXTHDR_FRAGMENT) || |
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(nexthdr == NEXTHDR_AUTH) || |
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(nexthdr == NEXTHDR_NONE) || |
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(nexthdr == NEXTHDR_DEST); |
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} |
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EXPORT_SYMBOL(ipv6_ext_hdr); |
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/* |
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* Skip any extension headers. This is used by the ICMP module. |
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* |
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* Note that strictly speaking this conflicts with RFC 2460 4.0: |
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* ...The contents and semantics of each extension header determine whether |
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* or not to proceed to the next header. Therefore, extension headers must |
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* be processed strictly in the order they appear in the packet; a |
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* receiver must not, for example, scan through a packet looking for a |
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* particular kind of extension header and process that header prior to |
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* processing all preceding ones. |
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* |
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* We do exactly this. This is a protocol bug. We can't decide after a |
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* seeing an unknown discard-with-error flavour TLV option if it's a |
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* ICMP error message or not (errors should never be send in reply to |
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* ICMP error messages). |
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* |
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* But I see no other way to do this. This might need to be reexamined |
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* when Linux implements ESP (and maybe AUTH) headers. |
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* --AK |
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* |
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* This function parses (probably truncated) exthdr set "hdr". |
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* "nexthdrp" initially points to some place, |
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* where type of the first header can be found. |
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* |
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* It skips all well-known exthdrs, and returns pointer to the start |
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* of unparsable area i.e. the first header with unknown type. |
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* If it is not NULL *nexthdr is updated by type/protocol of this header. |
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* |
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* NOTES: - if packet terminated with NEXTHDR_NONE it returns NULL. |
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* - it may return pointer pointing beyond end of packet, |
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* if the last recognized header is truncated in the middle. |
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* - if packet is truncated, so that all parsed headers are skipped, |
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* it returns NULL. |
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* - First fragment header is skipped, not-first ones |
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* are considered as unparsable. |
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* - Reports the offset field of the final fragment header so it is |
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* possible to tell whether this is a first fragment, later fragment, |
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* or not fragmented. |
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* - ESP is unparsable for now and considered like |
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* normal payload protocol. |
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* - Note also special handling of AUTH header. Thanks to IPsec wizards. |
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* |
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* --ANK (980726) |
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*/ |
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int ipv6_skip_exthdr(const struct sk_buff *skb, int start, u8 *nexthdrp, |
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__be16 *frag_offp) |
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{ |
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u8 nexthdr = *nexthdrp; |
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*frag_offp = 0; |
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while (ipv6_ext_hdr(nexthdr)) { |
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struct ipv6_opt_hdr _hdr, *hp; |
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int hdrlen; |
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if (nexthdr == NEXTHDR_NONE) |
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return -1; |
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hp = skb_header_pointer(skb, start, sizeof(_hdr), &_hdr); |
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if (!hp) |
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return -1; |
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if (nexthdr == NEXTHDR_FRAGMENT) { |
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__be16 _frag_off, *fp; |
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fp = skb_header_pointer(skb, |
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start+offsetof(struct frag_hdr, |
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frag_off), |
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sizeof(_frag_off), |
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&_frag_off); |
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if (!fp) |
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return -1; |
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*frag_offp = *fp; |
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if (ntohs(*frag_offp) & ~0x7) |
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break; |
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hdrlen = 8; |
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} else if (nexthdr == NEXTHDR_AUTH) |
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hdrlen = ipv6_authlen(hp); |
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else |
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hdrlen = ipv6_optlen(hp); |
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nexthdr = hp->nexthdr; |
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start += hdrlen; |
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} |
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*nexthdrp = nexthdr; |
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return start; |
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} |
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EXPORT_SYMBOL(ipv6_skip_exthdr); |
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int ipv6_find_tlv(const struct sk_buff *skb, int offset, int type) |
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{ |
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const unsigned char *nh = skb_network_header(skb); |
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int packet_len = skb_tail_pointer(skb) - skb_network_header(skb); |
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struct ipv6_opt_hdr *hdr; |
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int len; |
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if (offset + 2 > packet_len) |
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goto bad; |
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hdr = (struct ipv6_opt_hdr *)(nh + offset); |
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len = ((hdr->hdrlen + 1) << 3); |
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if (offset + len > packet_len) |
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goto bad; |
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offset += 2; |
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len -= 2; |
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while (len > 0) { |
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int opttype = nh[offset]; |
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int optlen; |
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if (opttype == type) |
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return offset; |
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switch (opttype) { |
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case IPV6_TLV_PAD1: |
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optlen = 1; |
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break; |
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default: |
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optlen = nh[offset + 1] + 2; |
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if (optlen > len) |
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goto bad; |
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break; |
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} |
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offset += optlen; |
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len -= optlen; |
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} |
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/* not_found */ |
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bad: |
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return -1; |
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} |
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EXPORT_SYMBOL_GPL(ipv6_find_tlv); |
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/* |
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* find the offset to specified header or the protocol number of last header |
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* if target < 0. "last header" is transport protocol header, ESP, or |
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* "No next header". |
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* |
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* Note that *offset is used as input/output parameter, and if it is not zero, |
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* then it must be a valid offset to an inner IPv6 header. This can be used |
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* to explore inner IPv6 header, eg. ICMPv6 error messages. |
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* |
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* If target header is found, its offset is set in *offset and return protocol |
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* number. Otherwise, return -1. |
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* |
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* If the first fragment doesn't contain the final protocol header or |
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* NEXTHDR_NONE it is considered invalid. |
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* |
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* Note that non-1st fragment is special case that "the protocol number |
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* of last header" is "next header" field in Fragment header. In this case, |
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* *offset is meaningless and fragment offset is stored in *fragoff if fragoff |
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* isn't NULL. |
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* |
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* if flags is not NULL and it's a fragment, then the frag flag |
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* IP6_FH_F_FRAG will be set. If it's an AH header, the |
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* IP6_FH_F_AUTH flag is set and target < 0, then this function will |
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* stop at the AH header. If IP6_FH_F_SKIP_RH flag was passed, then this |
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* function will skip all those routing headers, where segements_left was 0. |
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*/ |
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int ipv6_find_hdr(const struct sk_buff *skb, unsigned int *offset, |
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int target, unsigned short *fragoff, int *flags) |
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{ |
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unsigned int start = skb_network_offset(skb) + sizeof(struct ipv6hdr); |
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u8 nexthdr = ipv6_hdr(skb)->nexthdr; |
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bool found; |
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if (fragoff) |
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*fragoff = 0; |
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if (*offset) { |
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struct ipv6hdr _ip6, *ip6; |
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ip6 = skb_header_pointer(skb, *offset, sizeof(_ip6), &_ip6); |
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if (!ip6 || (ip6->version != 6)) |
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return -EBADMSG; |
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start = *offset + sizeof(struct ipv6hdr); |
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nexthdr = ip6->nexthdr; |
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} |
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do { |
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struct ipv6_opt_hdr _hdr, *hp; |
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unsigned int hdrlen; |
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found = (nexthdr == target); |
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if ((!ipv6_ext_hdr(nexthdr)) || nexthdr == NEXTHDR_NONE) { |
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if (target < 0 || found) |
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break; |
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return -ENOENT; |
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} |
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hp = skb_header_pointer(skb, start, sizeof(_hdr), &_hdr); |
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if (!hp) |
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return -EBADMSG; |
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if (nexthdr == NEXTHDR_ROUTING) { |
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struct ipv6_rt_hdr _rh, *rh; |
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rh = skb_header_pointer(skb, start, sizeof(_rh), |
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&_rh); |
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if (!rh) |
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return -EBADMSG; |
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if (flags && (*flags & IP6_FH_F_SKIP_RH) && |
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rh->segments_left == 0) |
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found = false; |
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} |
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if (nexthdr == NEXTHDR_FRAGMENT) { |
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unsigned short _frag_off; |
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__be16 *fp; |
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if (flags) /* Indicate that this is a fragment */ |
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*flags |= IP6_FH_F_FRAG; |
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fp = skb_header_pointer(skb, |
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start+offsetof(struct frag_hdr, |
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frag_off), |
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sizeof(_frag_off), |
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&_frag_off); |
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if (!fp) |
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return -EBADMSG; |
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_frag_off = ntohs(*fp) & ~0x7; |
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if (_frag_off) { |
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if (target < 0 && |
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((!ipv6_ext_hdr(hp->nexthdr)) || |
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hp->nexthdr == NEXTHDR_NONE)) { |
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if (fragoff) |
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*fragoff = _frag_off; |
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return hp->nexthdr; |
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} |
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if (!found) |
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return -ENOENT; |
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if (fragoff) |
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*fragoff = _frag_off; |
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break; |
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} |
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hdrlen = 8; |
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} else if (nexthdr == NEXTHDR_AUTH) { |
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if (flags && (*flags & IP6_FH_F_AUTH) && (target < 0)) |
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break; |
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hdrlen = ipv6_authlen(hp); |
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} else |
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hdrlen = ipv6_optlen(hp); |
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if (!found) { |
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nexthdr = hp->nexthdr; |
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start += hdrlen; |
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} |
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} while (!found); |
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*offset = start; |
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return nexthdr; |
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} |
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EXPORT_SYMBOL(ipv6_find_hdr);
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