Bug ID: 1198984
Summary: firewalld: please improve documentation on using it on
a RedHat/Fedora/CentOS router
Product: Fedora Documentation
QA Contact: docs-qa(a)lists.fedoraproject.org
Description of problem:
Even using the rich-language feature, it is still rather difficult to figure
how to use firewalld on a RedHat/Fedora/CentOS system that is used as a router
(a "transparent" system).
a. administrators will need *different* sets of rules/restrictions for access
to the router itself and to the various services that run beyond the router
(using or non using NAT).
b. It is not very clear how/where the predefined firewalld zones implement
their policies (ACCEPT or DROP) and when these policies apply to traffic
bounded *to* the router system or to traffic that *traverses* the router.
For example, an administrator needs an *easy* method to restrict VNC access
*to* the router itself (INPUT), but may want free VNC access to some server
located *behind* the router (FORWARD). In the second case, forwarding may (or
may not) imply NAT, depending if he goes on the Internet via the external
interface or simply goes in another LAN segment beyond the router.
c. It is not very clear how/where the predefined firewalld zones implement
their trafic rules ( *exceptions* to ACCEPT or DROP default policies) and when
these rules apply to traffic bounded *to* the router system or to traffic that
*traverses* the router.
Even it is not dynamic, the Shorewall application (http://shorewall.net/
as a higher-level language over iptables, offering the same concepts of "zones"
for interfaces. Much of its conceptual architecture is directly applicable
("portable") to firewalld, if accepted by developers.
Somewhat different from conceptual point of view, the "zones" are "levels
trust surrounding the router", including thr FW zone for the router itself.
(unlike firewalld, the shorewall zones have no "sources" or "services"
IPv4 and IPv6 zones are completely separated (they actually represent different
levels of trust).
Administrators may directly define policies, i.e. allow *default* actions to be
done when an packet travels from a zone to another (ACCEPT, REJECT). The most
sane policy between any two zones is REJECT (with further exceptions defined as
rules, see below).
Rules are *exceptions to policies* , explicitly defined (based on various
criteria such as source IP, destination IP, ports, etc.)
Rules may be expressed via predefined (or customised) "macros" (which are the
direct equivalent of firewalld's "services").
IPv4 and IPv6 policy and rules are completely separated (IMHO that's good,
since the use of global IPv6 addresses pose completely different security
problems than NATted & externally firewalled IPv4).
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