1 // SPDX-License-Identifier: GPL-2.0-only
3 * IPv6 library code, needed by static components when full IPv6 support is
4 * not configured or static.
6 #include <linux/export.h>
10 * find out if nexthdr is a well-known extension header or a protocol
13 bool ipv6_ext_hdr(u8 nexthdr
)
16 * find out if nexthdr is an extension header or a protocol
18 return (nexthdr
== NEXTHDR_HOP
) ||
19 (nexthdr
== NEXTHDR_ROUTING
) ||
20 (nexthdr
== NEXTHDR_FRAGMENT
) ||
21 (nexthdr
== NEXTHDR_AUTH
) ||
22 (nexthdr
== NEXTHDR_NONE
) ||
23 (nexthdr
== NEXTHDR_DEST
);
25 EXPORT_SYMBOL(ipv6_ext_hdr
);
28 * Skip any extension headers. This is used by the ICMP module.
30 * Note that strictly speaking this conflicts with RFC 2460 4.0:
31 * ...The contents and semantics of each extension header determine whether
32 * or not to proceed to the next header. Therefore, extension headers must
33 * be processed strictly in the order they appear in the packet; a
34 * receiver must not, for example, scan through a packet looking for a
35 * particular kind of extension header and process that header prior to
36 * processing all preceding ones.
38 * We do exactly this. This is a protocol bug. We can't decide after a
39 * seeing an unknown discard-with-error flavour TLV option if it's a
40 * ICMP error message or not (errors should never be send in reply to
41 * ICMP error messages).
43 * But I see no other way to do this. This might need to be reexamined
44 * when Linux implements ESP (and maybe AUTH) headers.
47 * This function parses (probably truncated) exthdr set "hdr".
48 * "nexthdrp" initially points to some place,
49 * where type of the first header can be found.
51 * It skips all well-known exthdrs, and returns pointer to the start
52 * of unparsable area i.e. the first header with unknown type.
53 * If it is not NULL *nexthdr is updated by type/protocol of this header.
55 * NOTES: - if packet terminated with NEXTHDR_NONE it returns NULL.
56 * - it may return pointer pointing beyond end of packet,
57 * if the last recognized header is truncated in the middle.
58 * - if packet is truncated, so that all parsed headers are skipped,
60 * - First fragment header is skipped, not-first ones
61 * are considered as unparsable.
62 * - Reports the offset field of the final fragment header so it is
63 * possible to tell whether this is a first fragment, later fragment,
65 * - ESP is unparsable for now and considered like
66 * normal payload protocol.
67 * - Note also special handling of AUTH header. Thanks to IPsec wizards.
72 int ipv6_skip_exthdr(const struct sk_buff
*skb
, int start
, u8
*nexthdrp
,
75 u8 nexthdr
= *nexthdrp
;
79 while (ipv6_ext_hdr(nexthdr
)) {
80 struct ipv6_opt_hdr _hdr
, *hp
;
83 if (nexthdr
== NEXTHDR_NONE
)
85 hp
= skb_header_pointer(skb
, start
, sizeof(_hdr
), &_hdr
);
88 if (nexthdr
== NEXTHDR_FRAGMENT
) {
89 __be16 _frag_off
, *fp
;
90 fp
= skb_header_pointer(skb
,
91 start
+offsetof(struct frag_hdr
,
99 if (ntohs(*frag_offp
) & ~0x7)
102 } else if (nexthdr
== NEXTHDR_AUTH
)
103 hdrlen
= ipv6_authlen(hp
);
105 hdrlen
= ipv6_optlen(hp
);
107 nexthdr
= hp
->nexthdr
;
114 EXPORT_SYMBOL(ipv6_skip_exthdr
);
116 int ipv6_find_tlv(const struct sk_buff
*skb
, int offset
, int type
)
118 const unsigned char *nh
= skb_network_header(skb
);
119 int packet_len
= skb_tail_pointer(skb
) - skb_network_header(skb
);
120 struct ipv6_opt_hdr
*hdr
;
123 if (offset
+ 2 > packet_len
)
125 hdr
= (struct ipv6_opt_hdr
*)(nh
+ offset
);
126 len
= ((hdr
->hdrlen
+ 1) << 3);
128 if (offset
+ len
> packet_len
)
135 int opttype
= nh
[offset
];
148 optlen
= nh
[offset
+ 1] + 2;
160 EXPORT_SYMBOL_GPL(ipv6_find_tlv
);
163 * find the offset to specified header or the protocol number of last header
164 * if target < 0. "last header" is transport protocol header, ESP, or
167 * Note that *offset is used as input/output parameter, and if it is not zero,
168 * then it must be a valid offset to an inner IPv6 header. This can be used
169 * to explore inner IPv6 header, eg. ICMPv6 error messages.
171 * If target header is found, its offset is set in *offset and return protocol
172 * number. Otherwise, return -1.
174 * If the first fragment doesn't contain the final protocol header or
175 * NEXTHDR_NONE it is considered invalid.
177 * Note that non-1st fragment is special case that "the protocol number
178 * of last header" is "next header" field in Fragment header. In this case,
179 * *offset is meaningless and fragment offset is stored in *fragoff if fragoff
182 * if flags is not NULL and it's a fragment, then the frag flag
183 * IP6_FH_F_FRAG will be set. If it's an AH header, the
184 * IP6_FH_F_AUTH flag is set and target < 0, then this function will
185 * stop at the AH header. If IP6_FH_F_SKIP_RH flag was passed, then this
186 * function will skip all those routing headers, where segements_left was 0.
188 int ipv6_find_hdr(const struct sk_buff
*skb
, unsigned int *offset
,
189 int target
, unsigned short *fragoff
, int *flags
)
191 unsigned int start
= skb_network_offset(skb
) + sizeof(struct ipv6hdr
);
192 u8 nexthdr
= ipv6_hdr(skb
)->nexthdr
;
199 struct ipv6hdr _ip6
, *ip6
;
201 ip6
= skb_header_pointer(skb
, *offset
, sizeof(_ip6
), &_ip6
);
202 if (!ip6
|| (ip6
->version
!= 6))
204 start
= *offset
+ sizeof(struct ipv6hdr
);
205 nexthdr
= ip6
->nexthdr
;
209 struct ipv6_opt_hdr _hdr
, *hp
;
211 found
= (nexthdr
== target
);
213 if ((!ipv6_ext_hdr(nexthdr
)) || nexthdr
== NEXTHDR_NONE
) {
214 if (target
< 0 || found
)
219 hp
= skb_header_pointer(skb
, start
, sizeof(_hdr
), &_hdr
);
223 if (nexthdr
== NEXTHDR_ROUTING
) {
224 struct ipv6_rt_hdr _rh
, *rh
;
226 rh
= skb_header_pointer(skb
, start
, sizeof(_rh
),
231 if (flags
&& (*flags
& IP6_FH_F_SKIP_RH
) &&
232 rh
->segments_left
== 0)
236 if (nexthdr
== NEXTHDR_FRAGMENT
) {
237 unsigned short _frag_off
;
240 if (flags
) /* Indicate that this is a fragment */
241 *flags
|= IP6_FH_F_FRAG
;
242 fp
= skb_header_pointer(skb
,
243 start
+offsetof(struct frag_hdr
,
250 _frag_off
= ntohs(*fp
) & ~0x7;
253 ((!ipv6_ext_hdr(hp
->nexthdr
)) ||
254 hp
->nexthdr
== NEXTHDR_NONE
)) {
256 *fragoff
= _frag_off
;
262 *fragoff
= _frag_off
;
266 } else if (nexthdr
== NEXTHDR_AUTH
) {
267 if (flags
&& (*flags
& IP6_FH_F_AUTH
) && (target
< 0))
269 hdrlen
= ipv6_authlen(hp
);
271 hdrlen
= ipv6_optlen(hp
);
274 nexthdr
= hp
->nexthdr
;
282 EXPORT_SYMBOL(ipv6_find_hdr
);