linuxdebug/net/ipv6/exthdrs_core.c

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2024-07-16 15:50:57 +02:00
// SPDX-License-Identifier: GPL-2.0-only
/*
* IPv6 library code, needed by static components when full IPv6 support is
* not configured or static.
*/
#include <linux/export.h>
#include <net/ipv6.h>
/*
* find out if nexthdr is a well-known extension header or a protocol
*/
bool 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);
}
EXPORT_SYMBOL(ipv6_ext_hdr);
/*
* 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.
* - Reports the offset field of the final fragment header so it is
* possible to tell whether this is a first fragment, later fragment,
* or not fragmented.
* - 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,
__be16 *frag_offp)
{
u8 nexthdr = *nexthdrp;
*frag_offp = 0;
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)
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)
return -1;
*frag_offp = *fp;
if (ntohs(*frag_offp) & ~0x7)
break;
hdrlen = 8;
} else if (nexthdr == NEXTHDR_AUTH)
hdrlen = ipv6_authlen(hp);
else
hdrlen = ipv6_optlen(hp);
nexthdr = hp->nexthdr;
start += hdrlen;
}
*nexthdrp = nexthdr;
return start;
}
EXPORT_SYMBOL(ipv6_skip_exthdr);
int ipv6_find_tlv(const struct sk_buff *skb, int offset, int type)
{
const unsigned char *nh = skb_network_header(skb);
int packet_len = skb_tail_pointer(skb) - skb_network_header(skb);
struct ipv6_opt_hdr *hdr;
int len;
if (offset + 2 > packet_len)
goto bad;
hdr = (struct ipv6_opt_hdr *)(nh + offset);
len = ((hdr->hdrlen + 1) << 3);
if (offset + len > packet_len)
goto bad;
offset += 2;
len -= 2;
while (len > 0) {
int opttype = nh[offset];
int optlen;
if (opttype == type)
return offset;
switch (opttype) {
case IPV6_TLV_PAD1:
optlen = 1;
break;
default:
if (len < 2)
goto bad;
optlen = nh[offset + 1] + 2;
if (optlen > len)
goto bad;
break;
}
offset += optlen;
len -= optlen;
}
/* not_found */
bad:
return -1;
}
EXPORT_SYMBOL_GPL(ipv6_find_tlv);
/*
* find the offset to specified header or the protocol number of last header
* if target < 0. "last header" is transport protocol header, ESP, or
* "No next header".
*
* Note that *offset is used as input/output parameter, and if it is not zero,
* then it must be a valid offset to an inner IPv6 header. This can be used
* to explore inner IPv6 header, eg. ICMPv6 error messages.
*
* If target header is found, its offset is set in *offset and return protocol
* number. Otherwise, return -1.
*
* If the first fragment doesn't contain the final protocol header or
* NEXTHDR_NONE it is considered invalid.
*
* Note that non-1st fragment is special case that "the protocol number
* of last header" is "next header" field in Fragment header. In this case,
* *offset is meaningless and fragment offset is stored in *fragoff if fragoff
* isn't NULL.
*
* if flags is not NULL and it's a fragment, then the frag flag
* IP6_FH_F_FRAG will be set. If it's an AH header, the
* IP6_FH_F_AUTH flag is set and target < 0, then this function will
* stop at the AH header. If IP6_FH_F_SKIP_RH flag was passed, then this
* function will skip all those routing headers, where segements_left was 0.
*/
int ipv6_find_hdr(const struct sk_buff *skb, unsigned int *offset,
int target, unsigned short *fragoff, int *flags)
{
unsigned int start = skb_network_offset(skb) + sizeof(struct ipv6hdr);
u8 nexthdr = ipv6_hdr(skb)->nexthdr;
bool found;
if (fragoff)
*fragoff = 0;
if (*offset) {
struct ipv6hdr _ip6, *ip6;
ip6 = skb_header_pointer(skb, *offset, sizeof(_ip6), &_ip6);
if (!ip6 || (ip6->version != 6))
return -EBADMSG;
start = *offset + sizeof(struct ipv6hdr);
nexthdr = ip6->nexthdr;
}
do {
struct ipv6_opt_hdr _hdr, *hp;
unsigned int hdrlen;
found = (nexthdr == target);
if ((!ipv6_ext_hdr(nexthdr)) || nexthdr == NEXTHDR_NONE) {
if (target < 0 || found)
break;
return -ENOENT;
}
hp = skb_header_pointer(skb, start, sizeof(_hdr), &_hdr);
if (!hp)
return -EBADMSG;
if (nexthdr == NEXTHDR_ROUTING) {
struct ipv6_rt_hdr _rh, *rh;
rh = skb_header_pointer(skb, start, sizeof(_rh),
&_rh);
if (!rh)
return -EBADMSG;
if (flags && (*flags & IP6_FH_F_SKIP_RH) &&
rh->segments_left == 0)
found = false;
}
if (nexthdr == NEXTHDR_FRAGMENT) {
unsigned short _frag_off;
__be16 *fp;
if (flags) /* Indicate that this is a fragment */
*flags |= IP6_FH_F_FRAG;
fp = skb_header_pointer(skb,
start+offsetof(struct frag_hdr,
frag_off),
sizeof(_frag_off),
&_frag_off);
if (!fp)
return -EBADMSG;
_frag_off = ntohs(*fp) & ~0x7;
if (_frag_off) {
if (target < 0 &&
((!ipv6_ext_hdr(hp->nexthdr)) ||
hp->nexthdr == NEXTHDR_NONE)) {
if (fragoff)
*fragoff = _frag_off;
return hp->nexthdr;
}
if (!found)
return -ENOENT;
if (fragoff)
*fragoff = _frag_off;
break;
}
hdrlen = 8;
} else if (nexthdr == NEXTHDR_AUTH) {
if (flags && (*flags & IP6_FH_F_AUTH) && (target < 0))
break;
hdrlen = ipv6_authlen(hp);
} else
hdrlen = ipv6_optlen(hp);
if (!found) {
nexthdr = hp->nexthdr;
start += hdrlen;
}
} while (!found);
*offset = start;
return nexthdr;
}
EXPORT_SYMBOL(ipv6_find_hdr);