mlx5ehdr
udph->len = htons(sizeof(struct mlx5ehdr) + sizeof(struct udphdr));
sizeof(struct mlx5ehdr);
struct mlx5ehdr *mlxh;
mlxh = (struct mlx5ehdr *)((char *)udph + sizeof(*udph));
sizeof(struct udphdr) + sizeof(struct mlx5ehdr))
struct mlx5ehdr *mlxh;