114 lines
3.4 KiB
C
114 lines
3.4 KiB
C
/*
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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 == NULL)
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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 == NULL)
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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 = (hp->hdrlen+2)<<2;
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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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