netdev - Re: [PATCH net] tipc: not enable tipc when ipv6 works as a module

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Message-ID: <98214acb-5e9f-0477-bc97-1f3b2c690f14@infradead.org>
Date:   Mon, 17 Aug 2020 12:55:24 -0700
From:   Randy Dunlap <rdunlap@...radead.org>
To:     Cong Wang <xiyou.wangcong@...il.com>
Cc:     Xin Long <lucien.xin@...il.com>,
        network dev <netdev@...r.kernel.org>,
        David Miller <davem@...emloft.net>,
        Jon Maloy <jmaloy@...hat.com>,
        Ying Xue <ying.xue@...driver.com>,
        tipc-discussion@...ts.sourceforge.net
Subject: Re: [PATCH net] tipc: not enable tipc when ipv6 works as a module

On 8/17/20 12:26 PM, Cong Wang wrote:
> On Mon, Aug 17, 2020 at 12:00 PM Randy Dunlap <rdunlap@...radead.org> wrote:
>>
>> On 8/17/20 11:55 AM, Cong Wang wrote:
>>> On Mon, Aug 17, 2020 at 11:49 AM Randy Dunlap <rdunlap@...radead.org> wrote:
>>>>
>>>> On 8/17/20 11:31 AM, Cong Wang wrote:
>>>>> On Sun, Aug 16, 2020 at 11:37 PM Xin Long <lucien.xin@...il.com> wrote:
>>>>>>
>>>>>> On Mon, Aug 17, 2020 at 2:29 AM Cong Wang <xiyou.wangcong@...il.com> wrote:
>>>>>>>
>>>>>>> Or put it into struct ipv6_stub?
>>>>>> Hi Cong,
>>>>>>
>>>>>> That could be one way. We may do it when this new function becomes more common.
>>>>>> By now, I think it's okay to make TIPC depend on IPV6 || IPV6=n.
>>>>>
>>>>> I am not a fan of IPV6=m, but disallowing it for one symbol seems
>>>>> too harsh.
>>>>
>>>> Hi,
>>>>
>>>> Maybe I'm not following you, but this doesn't disallow IPV6=m.
>>>
>>> Well, by "disallowing IPV6=m" I meant "disallowing IPV6=m when
>>> enabling TIPC" for sure... Sorry that it misleads you to believe
>>> completely disallowing IPV6=m globally.
>>>
>>>>
>>>> It just restricts how TIPC can be built, so that
>>>> TIPC=y and IPV6=m cannot happen together, which causes
>>>> a build error.
>>>
>>> It also disallows TIPC=m and IPV6=m, right? In short, it disalows
>>> IPV6=m when TIPC is enabled. And this is exactly what I complain,
>>> as it looks too harsh.
>>
>> I haven't tested that specifically, but that should work.
>> This patch won't prevent that from working.
> 
> Please give it a try. I do not see how it allows IPV6=m and TIPC=m
> but disallows IPV6=m and TIPC=y.

TIPC=m and IPV6=m builds just fine.

Having tipc autoload ipv6 is a different problem. (IMO)


This Kconfig entry:
 menuconfig TIPC
 	tristate "The TIPC Protocol"
 	depends on INET
+	depends on IPV6 || IPV6=n

says:
If IPV6=n, TIPC can be y/m/n.
If IPV6=y/m, TIPC is limited to whatever IPV6 is set to.
TIPC cannot be =y unless IPV6=y.


>> We have loadable modules calling other loadable modules
>> all over the kernel.
> 
> True, we rely on request_module(). But I do not see TIPC calls
> request_module() to request IPV6 module to load "ipv6_dev_find".


-- 
~Randy