Network access control list parsing library.

This is being forked from the ACL lib that is bundled with Trigger. The goal is to pull this out of Trigger and have it be a stand-alone project. Once it becomes stable, it will be pulled out of Trigger core and converted into an optional feature.

Let's start with a simple Cisco ACL:

>>> from acl import parse
>>> aclobj = parse("access-list 123 permit tcp any host 10.20.30.40 eq 80")
>>> aclobj.terms
[<Term: None>]
>>> t = aclobj.terms[0]
>>> t.match
<Matches: destination-port [80], destination-address [IP('10.20.30.40')],
          protocol [<Protocol: tcp>]>

And convert it to Juniper format:

>>> aclobj.name_terms() # Juniper policy terms must have names
>>> aclobj.terms
[<Term: T1>]
>>> print '\n'.join(aclobj.output(format='junos'))
filter 123 {
    term T1 {
        from {
            destination-address {
                10.20.30.40/32;
            }
            protocol tcp;
            destination-port 80;
        }
        then {
            accept;
        }
    }
}

Coming Soon(TM).

DSCP: Juniper does not allow the inclusion of 'dscp' and 'dscp-except' in the same term. The latter will override any others.

Observe:

me@router# load merge terminal
[Type ^D at a new line to end input]
firewall filter asdf {
    term DSCP_term {
        /* Project:"non-zero TOS value DCSP" */
        from {
            dscp-except [ af11 cs0 ];
            dscp [ af11 be cs0 cs7 ];
        }
        then {
            count match_non_zero_DCSP;
            port-mirror;
            next term;
        }
    }
}
load complete

[edit]
me@router# show firewall filter asdf
term DSCP_term {
    /* Project:"non-zero TOS value DCSP" */
    from {
        dscp [ af11 be cs0 cs7 ];
    }
    then {
        count match_non_zero_DCSP;
        port-mirror;
        next term;
    }
}

[edit]
me@router#