// 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) { … } EXPORT_SYMBOL(…); /* * 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) { … } EXPORT_SYMBOL(…); int ipv6_find_tlv(const struct sk_buff *skb, int offset, int type) { … } EXPORT_SYMBOL_GPL(…); /* * 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) { … } EXPORT_SYMBOL(…);
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