[ovirt-devel] Firewalld migration.

[Yedidyah Bar David]

On Sun, Mar 26, 2017 at 2:12 PM, Oved Ourfali <oourfali at redhat.com> wrote:
>
>
> On Sun, Mar 26, 2017 at 2:08 PM, Leon Goldberg <lgoldber at redhat.com> wrote:
>>
>> Hey Oved,
>>
>> I don't think completely moving away from iptables is foreseeable at this
>> point, but I could be of course wrong. Either way, upgrading still needs to
>> be thought of.
>>
>
> I see.
>
>>
>> By stating that the current infrastructure is complex, I was referring to
>> the entire chain of storing rules in the database, fetching them using a
>> dedicated deployment class consisting of include/exclude logic, sending them
>> over, unpacking, deploying...
>>
>> This procedure involves a lot of code that could be made redundant if the
>> required logic is present in the host, which to me seems favorable. It of
>> course entails other potential difficulties, primarily in the form of custom
>> services.
>>
>> I don't think otopi's firewalld plugin is any more complex than the
>> potential code that will have to be written in vdsm-tool, however it
>> currently expects the data generated by aforementioned chain. The hybrid
>> approach briefly touches on simplifying Engine's involvement while retaining
>> use of otopi's plugin.
>>
>
> Okay. I think that writing a new plugin for firewalld is indeed a good
> option, whether you "refactor" the engine side or not.

otopi already has a 'firewalld' plugin. It's already in use, at least
by engine-setup, so we should be a bit careful if we want to change it.
Not preventing/objecting anything, just mentioning.

This plugin's interface currently only takes XML-content as input.
It has no place for configuring existing firewalld services presumably
already provided elsewhere (by firewalld itself or 3rd party packages,
such as vdsm). So if we go that route we probably want to extend this
interface to allow passing service names and rely on them being defined
elsewhere.

A related issue is that for engine-setup, the _input_ is currently
firewalld xml content, and if users choose to configure 'iptables',
this is parsed to generate iptables rules. This is currently an engine-setup
issue only, but will affect also host deploy flow if we decided to
allow passing service names (without their xml content) and still keep
compatibility to current state and allow configuring iptables on the
host. We'll then be there in the same situation we are at with engine-setup.
See also https://bugzilla.redhat.com/1432354 . An alternative is obviously
deciding to remove iptables support and support only firewalld, but this
is a rather radical change for users, imo.

See also this for some of the existing behavior of engine-setup:

https://bugzilla.redhat.com/show_bug.cgi?id=1024707#c9

IMO we first need to decide what we want, then how to do that. IMO the
questions we have re "what we want" are, more-or-less:

1. Do we want to support in some version X both iptables and firewalld, or
is it ok to stop support for iptables and support only firewalld without
overlap? If so, do we handle upgrades, and how?

2. Do we want to support custom firewalld xml to be configured on the
host by us? Or is it ok to only support choosing among existing services,
which will need to be added to the host using other means (packaged by
firewalld, packaged by 3rd parties, added manually by users)?

3. Opposite of (2.): Do we want to support firewalld services that are
added to the host using other means (see there)? Obviously we do, but:
If we do, do we still want to support also iptables (see (1.))? And if
so, what do we want to then happen?

(2.) and (3.) are not conflicting, each needs its own answer.

My (thoughts about) answers:

1. If done well enough, and considerably simplifies things, I think it's
ok to jump directly from "only iptables" to "only firewalld", but then
we should announce this ahead of time to give users time to plan/prepare.
If it's not too costly, I'd prefer to support both for the foreseeable
future, though.

2. Latter option here is problematic, if we need/want to allow
customizing services during deploy. E.g. suppose that one day we want
to make the vdsm port configurable. It will be nice if this can be done
by only changing things on the engine, without having to distribute
changes (conf and/or packages) to all hosts before host-deploy.
I'd say we can go a long way here by having a strict requirement from
all services that we need/want on hosts to have official IANA-registered
port numbers - then, it's imo much easier to tell users "If you want to
change the port for service X, you have to (long list of complex actions
goes here)". Currently, where services are not registered, we risk
conflicts with existing services, requiring the user to change ports -
and so we can't make this process too difficult. No idea how important
this is in practice.

3. Not sure :-( I'd say that if we want to support both iptables and
firewalld together, and support both "xml in engine" and "xml in host",
then it might be ok if the custom rules/services will not automatically
apply to both iptables and firewalld. Meaning - you can set both custom
iptables rules and firewalld services, but it's up to you to make sure
they actually do the same thing if that's important to you.

Bottom line: I think we should summarize the open questions in a way
that will make it clear to users how each answer will affect them, and
ask what they think. Leon already started doing this [1], I only saw
one reply. Perhaps this means that users do not care that much, and
expect us to just decide and tell them what we decided (and always to
keep the option to disable this feature, as is possible today, and do
this themselves, if our choice of solution does not fit their needs).

I know this is way too loooong, sorry. Feel free to ignore, but then
please ask simpler questions if you want shorter answers :-)

[1] http://lists.ovirt.org/pipermail/users/2017-March/080600.html

>
>>
>>
>>
>> On Sun, Mar 26, 2017 at 1:40 PM, Oved Ourfali <oourfali at redhat.com> wrote:
>>>
>>> top-posting:
>>> You need to also consider how upgrade will be handled, right?
>>> Or iptables will still remain supported?
>>>
>>> Also, see some comments inline.
>>>
>>> Regards,
>>> Oved
>>>
>>> On Sun, Mar 26, 2017 at 1:33 PM, Leon Goldberg <lgoldber at redhat.com>
>>> wrote:
>>>>
>>>>
>>>> Hey,
>>>>
>>>> We're looking to migrate from iptables to firewalld. We came up with a
>>>> couple of possible approaches we'd like opinions on. I'll list the options
>>>> first, and will
>>>>
>>>> 1) Replicate existing flow:
>>>>
>>>> As of date, iptable rules are inserted in the database via SQL config
>>>> files. During host deployment, VdsDeployIptablesUnit adds the required rules
>>>> (based on cluster/firewall configuration) to the deployment configuration,
>>>> en route to being deployed on the host via otopi and its iptables plugin.
>>>>
>>>> Pros:
>>>>
>>>> - Reuse of existing infrastructure.
>>>>
>>>> Cons:
>>>>
>>>> - Current infrastructure is overly complex...
>>>
>>>
>>> Can you elaborate?
>>> I'm not an otopi expert, but I think that otopi plugins shouldn't be more
>>> complex than what you describe in section #2, and the plugins were meant in
>>> order to handle such cases.
>>>
>>>> - Many of the required services are provided by firewalld. Rewriting
>>>> them is wasteful; specifying them (instead of providing actual service .xml
>>>> content) will require adaptations on both (engine/host) sides. More on that
>>>> later.
>>>>
>>>>
>>>> 2) Host side based configuration:
>>>>
>>>> Essentially, all the required logic (aforementioned cluster/firewall
>>>> configuration) to determine if/how firewalld should be deployed could be
>>>> passed on to the host via ohd. Vdsm could take on the responsibility of
>>>> examining the relevant configuration, and then creating and/or adding the
>>>> required services (using vdsm.conf and vdsm-tool).
>>>>
>>>
>>> So here you replace the otopi plugin with relevant vdsm-tool code, and
>>> the question is why is that better?
>>>
>>>>
>>>> Pros:
>>>>
>>>>  - Engine side involvement is greatly diminished.
>>>>  - Simple(r).
>>>>
>>>> Cons:
>>>>
>>>>  - Custom services/rules capabilities will have to be rethought and
>>>> re-implemented (current infrastructure supports custom iptables rules by
>>>> being specified in the SQL config file).
>>>>
>>>>
>>>> 3) Some other hybrid approach:
>>>>
>>>> If we're able to guarantee all the required firewalld services are
>>>> statically provided one way or the other, the current procedure could be
>>>> replicated and be made more simpler. Instead of providing xml content in the
>>>> form of strings, service names could be supplied. The responsibility of
>>>> actual service deployment becomes easier, and could be left to otopi (with
>>>> the appropriate modifications) or switched over to vdsm.
>>>>
>>>> --
>>>>
>>>> Regardless, usage of statically provided vs. dynamically created
>>>> services remains an open question. I think we'd like to avoid implementing
>>>> logic that ask whether some service is provided (and then write it if it
>>>> isn't...), and so choosing between the dynamic and static approaches is also
>>>> needed. Using the static approach, guaranteeing all services are provided
>>>> will be required.
>>>>
>>>> I do believe guaranteeing the presence of all required services is worth
>>>> it, however custom services aren't going to be naively compatible, and we'll
>>>> still have to use similar mechanism as described in #1 (service string ->
>>>> .xml -> addition of service name to active zone).
>>>>
>>>>
>>>> Your thoughts are welcome.
>>>>
>>>> Thanks,
>>>> Leon
>>>>
>>>
>>
>



-- 
Didi