exthdrs_core.c
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/*
* IPv6 library code, needed by static components when full IPv6 support is
* not configured or static.
*/
#include <net/ipv6.h>
/*
* find out if nexthdr is a well-known extension header or a protocol
*/
int ipv6_ext_hdr(u8 nexthdr)
{
/*
* find out if nexthdr is an extension header or a protocol
*/
return (nexthdr == NEXTHDR_HOP) ||
(nexthdr == NEXTHDR_ROUTING) ||
(nexthdr == NEXTHDR_FRAGMENT) ||
(nexthdr == NEXTHDR_AUTH) ||
(nexthdr == NEXTHDR_NONE) ||
(nexthdr == NEXTHDR_DEST);
}
/*
* Skip any extension headers. This is used by the ICMP module.
*
* Note that strictly speaking this conflicts with RFC 2460 4.0:
* ...The contents and semantics of each extension header determine whether
* or not to proceed to the next header. Therefore, extension headers must
* be processed strictly in the order they appear in the packet; a
* receiver must not, for example, scan through a packet looking for a
* particular kind of extension header and process that header prior to
* processing all preceding ones.
*
* We do exactly this. This is a protocol bug. We can't decide after a
* seeing an unknown discard-with-error flavour TLV option if it's a
* ICMP error message or not (errors should never be send in reply to
* ICMP error messages).
*
* But I see no other way to do this. This might need to be reexamined
* when Linux implements ESP (and maybe AUTH) headers.
* --AK
*
* This function parses (probably truncated) exthdr set "hdr".
* "nexthdrp" initially points to some place,
* where type of the first header can be found.
*
* It skips all well-known exthdrs, and returns pointer to the start
* of unparsable area i.e. the first header with unknown type.
* If it is not NULL *nexthdr is updated by type/protocol of this header.
*
* NOTES: - if packet terminated with NEXTHDR_NONE it returns NULL.
* - it may return pointer pointing beyond end of packet,
* if the last recognized header is truncated in the middle.
* - if packet is truncated, so that all parsed headers are skipped,
* it returns NULL.
* - First fragment header is skipped, not-first ones
* are considered as unparsable.
* - ESP is unparsable for now and considered like
* normal payload protocol.
* - Note also special handling of AUTH header. Thanks to IPsec wizards.
*
* --ANK (980726)
*/
int ipv6_skip_exthdr(const struct sk_buff *skb, int start, u8 *nexthdrp)
{
u8 nexthdr = *nexthdrp;
while (ipv6_ext_hdr(nexthdr)) {
struct ipv6_opt_hdr _hdr, *hp;
int hdrlen;
if (nexthdr == NEXTHDR_NONE)
return -1;
hp = skb_header_pointer(skb, start, sizeof(_hdr), &_hdr);
if (hp == NULL)
return -1;
if (nexthdr == NEXTHDR_FRAGMENT) {
__be16 _frag_off, *fp;
fp = skb_header_pointer(skb,
start+offsetof(struct frag_hdr,
frag_off),
sizeof(_frag_off),
&_frag_off);
if (fp == NULL)
return -1;
if (ntohs(*fp) & ~0x7)
break;
hdrlen = 8;
} else if (nexthdr == NEXTHDR_AUTH)
hdrlen = (hp->hdrlen+2)<<2;
else
hdrlen = ipv6_optlen(hp);
nexthdr = hp->nexthdr;
start += hdrlen;
}
*nexthdrp = nexthdr;
return start;
}
EXPORT_SYMBOL(ipv6_ext_hdr);
EXPORT_SYMBOL(ipv6_skip_exthdr);