Writing a Pattern-Based Rule in RoLex


RoLex provides FSM machinery, so rules are simple. (41 LOC for next-hop test from previous slide)

Rules specify "nodes" and "transitions".

$no_nh_self_ebgp = sub {
    print STDERR 
        $fsm->substitute_def_bindings("ebgp: no next-hop-self _r1 (_n2)\n");
    $fsm->transition('_r1: router bgp _a1 [[ network _n3 mask _m3 
                      <contains(_n3/_m3, _n2)>]]',1)->($OK);
    &$ERROR('_n2 not in iBGP/IGP (eBGP session)');
};

Network-wide checking is automatic!