aa_allow: /* innermost frame allows a */
aa_block: /* innermost frame denies a */
ab_allow: /* innermost frame allows a */
ab_block: /* innermost frame denies a */
aba_allow: /* innermost frame allows b,a */
aba_block: /* innermost frame denies b */
aba2_block: /* innermost frame denies a */
abb_allow: /* innermost frame allows b,a */
abb_block: /* innermost frame denies b */
abb2_block: /* innermost frame denies a */