283 lines
7.5 KiB
C
283 lines
7.5 KiB
C
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// 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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if (len < 2)
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goto bad;
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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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