libbsd: How to add an option for switching off IPv6 (or other BSD Kernel configurations)

Fri Aug 5 11:59:33 UTC 2016

Am 02.08.2016 um 12:21 schrieb Chris Johns:
> On 2/08/2016 8:05 PM, Christian Mauderer wrote:
>> Am 02.08.2016 um 08:57 schrieb Christian Mauderer:
>>> Am 02.08.2016 um 04:09 schrieb Chris Johns:
>>>> On 02/08/2016 00:04, Christian Mauderer wrote:
>> [...]
>>>
>>>>> Are there any better ideas how to implement such an option?
>>>>
>>>> There are 2 parts that need be to changed to make this work. This
>>>> assumes you will need to control the source being built.
>>>>
>>>> The first is the module descriptions in libbsd.py and then the
>>>> generator. I suggest you look at the various module class methods used
>>>> to add source and consider adding a 'section' argument which defaults to
>>>> 'default' (always True). This would lets you move code into specific
>>>> sections, for example:
>>>>
>>>>     dhcpcd_defines='-D__FreeBSD__ -DTHERE_IS_NO_FORK ...'
>>>>     mod.addSourceFiles(
>>>>         [
>>>>             'dhcpcd/ipv6.c',
>>>>             'dhcpcd/ipv6nd.c',
>>>>         ],
>>>>         mm.generator['source'](dhcpcd_defines),
>>>>         section = 'networking.ipv6_yes'
>>>>     )
>>>>
>>>> Note, this definition generates something that is evaluated when waf
>>>> runs so the 'section' populates a dict where the 'networking.ipv6_yes'
>>>> key is tested for True or False depending what the user specifies.
>>>>
>>>> You could also change the class constructor so you have:
>>>>
>>>>  mod = builder.Module('dhcpcd', section = 'networking.dhcp')
>>>>
>>>> The dot notation would allow control of the sources at the module level
>>>> to finally get sorted out. The dhcpcd module becomes 'networking.dhcpcd'
>>>> which means build if networking and dhcpcd are True. You could work down
>>>> the dots checking at each point to make sure the module can be built.
>>>> Currently module level user control has been left hanging with commented
>>>> modules, eg '#mm.addModule(dev_usb_controller_add_on(mm)'. If the
>>>> section 'usb.dev_usb_controller_add_on' is False by default that module
>>>> is not built which is what we have now.
>>>>
>>>> The second part is in the waf script (wscript) which handles the user
>>>> interface, ie parses
>>>> --config="networking:ipv6=no,pink-frames-only,chrismac-buf-frames=64". I
>>>> would add this code in a new Python module libbsd_opts.py and imported
>>>> into libbsd_waf.py (generated) and called in the 'options' function in
>>>> libbsd_waf.py. This would parse and populate a dict the generated module
>>>> code uses.
>>>>
>>>
>>> Thanks for the detailed description. I'll need some time to understand
>>> everything but it looks like a good starting point.
>>>
>> [...]
>>>
>>
>> Hello Chris,
>>
>> I think I managed to understand most of it even if I still only have a
>> rough Idea where to start.
>>
>> If I'm right, you suggested two alternative possible methods:
>>
>> 1) Add the section-option as parameter to a addSourceFiles. This means
>> it is only valid for some sources in a module.
>>
>> 2) Alternatively add it directly to the module.
>>
> 
> I am saying have both so all modules are provide a section.
> 
> I only used the work section because it is the term used in INI files.
> 
>> Did I understand you correct. Or did you mean that the section is added
>> to both - the module and the source?
> 
> Close, but how about annotating all source and then we can control it
> better.
> 
>>
>> As far as I understand the first method, this could be also used for the
>> define that depends on the option. Something like this:
>>
>>     def dhcpcd(mm):
>>         mod = builder.Module('dhcpcd')
>>         dhcpcd_sources =
>>             [
>>                 'dhcpcd/arp.c',
>>                 'dhcpcd/auth.c',
>>                 ...
>>             ]
>>         dhcpcd_defines_base = '-D__FreeBSD__ -DTHERE_IS_NO_FORK ...'
>>         dhcpcd_defines_inet6 = dhcpcd_defines_base + ' -DINET6'
>>         mod.addSourceFiles(
>>             dhcpcd_sources,
>>             mm.generator['source'](dhcpcd_defines_base),
>>             section = 'networking.ipv6_no'
>>         )
>>         mod.addSourceFiles(
>>             dhcpcd_sources,
>>             mm.generator['source'](dhcpcd_defines_inet6),
>>             section = 'networking.ipv6_yes'
>>         )
>>         return mod
>>
> 
> It is close, however I suspect -DINET6 is need for all source when being
> built. I will take a look and see what I can sort out.
> 
>> I'm not sure how this would be possible with the second method.
> 
> Let me take a closer look.
> 
> Chris
> 

Hello Chris,

just for information: For a test I applied the necessary changes to
switch off IPv6 manually. Of course we can't add this to the libbsd
directly but it could be a reference what would be necessary.

You can find the patch appended to this mail. It should be applied on
top of 07176074bdfb53946e277e046ca3e2bc77726bf7 or later.

Kind regards

Christian

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