rmnet_map_ul_csum_header
additional_header_len = sizeof(struct rmnet_map_ul_csum_header);
struct rmnet_map_ul_csum_header *ul_header,
struct rmnet_map_ul_csum_header *ul_header,
struct rmnet_map_ul_csum_header *ul_header,
struct rmnet_map_ul_csum_header *ul_header;
ul_header = (struct rmnet_map_ul_csum_header *)
skb_push(skb, sizeof(struct rmnet_map_ul_csum_header));
sizeof(struct rmnet_map_ul_csum_header);
headroom += sizeof(struct rmnet_map_ul_csum_header);
header_size += sizeof(struct rmnet_map_ul_csum_header);