llc_circular_between
u8 llc_circular_between(u8 a, u8 b, u8 c);
if (llc_circular_between(llc_sk(sk)->vS, nr, llc_sk(sk)->X))
return !llc_circular_between(vr, ns,
rc = !llc_circular_between(nr1, nr, (nr2 + 1) % LLC_2_SEQ_NBR_MODULO);