UMEM_SIZE
munmap(xsk->umem_area, UMEM_SIZE);
xsk->umem_area = mmap(NULL, UMEM_SIZE, PROT_READ | PROT_WRITE, mmap_flags, -1, 0);
xsk->umem_area, UMEM_SIZE,
xsk->umem_area = mmap(NULL, UMEM_SIZE, PROT_READ | PROT_WRITE, mmap_flags, -1, 0);
xsk->umem_area, UMEM_SIZE,
munmap(xsk->umem_area, UMEM_SIZE);