int ip6_find_1stfragopt(struct sk_buff *skb, u8 **nexthdr)
{
	unsigned int offset = sizeof(struct ipv6hdr);
	unsigned int packet_len = skb_tail_pointer(skb) -
		skb_network_header(skb);
	int found_rhdr = 0;
	*nexthdr = &ipv6_hdr(skb)->nexthdr;

	while (offset <= packet_len) {
		struct ipv6_opt_hdr *exthdr;

		switch (**nexthdr) {

		case NEXTHDR_HOP:
			break;
		case NEXTHDR_ROUTING:
			found_rhdr = 1;
			break;
		case NEXTHDR_DEST:
#if IS_ENABLED(CONFIG_IPV6_MIP6)
			if (ipv6_find_tlv(skb, offset, IPV6_TLV_HAO) >= 0)
				break;
#endif
			if (found_rhdr)
				return offset;
			break;
		default:
			return offset;
		}

		if (offset + sizeof(struct ipv6_opt_hdr) > packet_len)
			return -EINVAL;

		exthdr = (struct ipv6_opt_hdr *)(skb_network_header(skb) +
						 offset);
		offset += ipv6_optlen(exthdr);
		if (offset > IPV6_MAXPLEN)
			return -EINVAL;
		*nexthdr = &exthdr->nexthdr;
	}

	return -EINVAL;
}