u8 buffer[100] = {0};
u8 *l6_header = 0;
ip6_ext_header_t *ext_head;

ip6_header_t *ip6 = (ip6_header_t *)buffer;
/* Fill in ip6 header fields */
ip6->ip_version_traffic_class_and_flow_label =
clib_host_to_net_u32 (0x6 << 28);
ip6->payload_length = clib_host_to_net_u16 (100);
ip6->protocol = IP_PROTOCOL_TCP;
ip6->hop_limit = 255;
/below is data section ,some bytes(red) just like a ext head/
l6_header = (u8*)(ip6+1);
ext_head = (ip6_ext_header_t *)l6_header;
ext_head->next_hdr = IP_PROTOCOL_IPV6_FRAGMENTATION;
ext_head->n_data_u64s = 2;
ext_head = ip6_ext_authhdr_header((ext_head));
ext_head->next_hdr = 59;/no next head/

------------------------------------------------

ip6_frag_hdr_t *frag_hdr = NULL;
ip6_ext_header_t * prev0 = NULL;
ip6_ext_header_find_t (ip6, prev0, frag_hdr, IP_PROTOCOL_IPV6_FRAGMENTATION);
if(frag_hdr)

{ clib_warning(" ERROR find frag head in tcp pkg !\n"); assert(0); }