Re: [fuse-devel] Do I need to support both - libfuse2 and libfuse3 in my application in order to work on more Linux distros, in case I deploy libfuse with my application

[Antonio SJ M. <tra...@sp...>]

https://github.com/libfuse/libfuse/blob/master/include/fuse_common.h#L128

On 10/1/2019 9:17 AM, Cyril Cyrov wrote:
>> All new features are optional and established at the FUSE_INIT phase
> Which are those "all new features"? I mean, what features could be
> unsupported by the kernel?
>
> On Tue, Oct 1, 2019 at 3:58 PM Cyril Cyrov <cyr...@gm...> wrote:
>> Yes, I think I totally get your point.
>>
>> My point of view is - building libfuse3 on older systems is possible
>> and it cost me like 2-3 hours to build the necessary tools. Packing
>> fusermount3 in the installer also doesn't sound so hard - we already
>> do deploy libfuse.so, that's just one ore file. And finally, patching
>> in order to find the fusermount3 binary - this seems like a trivial
>> patch.
>> Also given the fact, that we rarely update fuse versions, this effort
>> seems to worth it.
>>
>> My two concerns, that I still have, are:
>> 1) is there any security risk in deploying fusermount3 and should I do
>> anything special, except just copy the binary into the installer?
>> 2) how will I understand that the kernel is too old for some feature,
>> that I need (I get it, that it's during the FUSE_INIT phase, I'll have
>> to read more about this).
>>
>> On Tue, Oct 1, 2019 at 3:19 PM Antonio SJ Musumeci <tra...@sp...> wrote:
>>> You can optionally deploy it or patch the build to install to a
>>> different location / filename.
>>>
>>> This is what I was getting at prior. The library is not designed to be
>>> used this way so without upstreaming some changing that make it easier
>>> to do so you'll have to maintain some part of the setup.
>>>
>>> My biggest problem with embedding libfuse3 was the build system simply
>>> not working on older platforms and getting that replaced or officially
>>> supporting multiple systems doesn't seem a reasonable ask.
>>>
>>> On 10/1/2019 7:31 AM, Cyril Cyrov wrote:
>>>> Actually, deploying `libfuse3.so` won't be enough, deploying
>>>> `fusermount3` is also necessary (+ building libfuse with `-D
>>>> FUSERMOUNT_DIR=.....`)? Isn't this some kind of a security issue
>>>> (deploying fusermount3)?
>>>>
>>>> On Tue, Oct 1, 2019 at 1:53 PM Cyril Cyrov <cyr...@gm...> wrote:
>>>>> Hi,
>>>>>
>>>>> Here's an introduction for this thread:
>>>>> https://github.com/libfuse/libfuse/issues/460
>>>>>
>>>>> Long story short:
>>>>> Q: How can I support both libfuse2 and libfuse3 in order to make my
>>>>> app work on more Linux distos?
>>>>> A: You don't need to do that.
>>>>>
>>>>> So, continuing the discussion here.
>>>>>
>>>>> ---
>>>>>
>>>>> My misunderstanding comes from the fact, that I though there are two
>>>>> different kernel modules for the two versions and that libfuse3 can
>>>>> only work on Linux distros, which do have `fuse3` package installed
>>>>> (and these distros are just a few). This misunderstanding was also
>>>>> supported by the fact, that libfuse3 needs fusermount3 in order to
>>>>> create a mountpoint.
>>>>>
>>>>> Another miscommunication occurred by the different interpretation of
>>>>> "patching the fuse implementation" and "embedding" fuse.
>>>>>
>>>>> We do deploy a libfuse shared object with our application. So, this is
>>>>> not an issue at all.
>>>>>
>>>>> My concern was - can I use and deploy libfuse3 on older Linux distros,
>>>>> like CentOS 6, for example?
>>>>>
>>>>> What confuses me further is that I cannot find any matching between
>>>>> libfuse versions and kernel versions, explaining which libfuse version
>>>>> is compatible with which kernel versions.
>>>>>
>>>>> ---
>>>>>
>>>>> @trapexit
>>>>>> Then you'll have to deal with the distro's support
>>>>> By "avoid patching the fuse implementation" I didn't mean I don't want
>>>>> to deploy fuse build, I just misunderstood you and thought that you
>>>>> suggest actually making some source patch in order to "merge" them
>>>>> somehow. Sorry for the misleading.
>>>>>
>>>>> ---
>>>>>
>>>>> @Nikratio:
>>>>>> "Why don't you ship two binaries (one for libfuse2 and one for libfuse3) together with a small wrapper that picks with version to use?"
>>>>> This will be necessary only if we don't deploy a build for libfuse, correct?
>>>>>
>>>>> ---
>>>>>
>>>>> So, I'll try to wrap things up, please correct me if I'm wrong - appreciated!
>>>>>
>>>>> We can actually use only libfuse3 and if we deploy it (or statically
>>>>> link it in our application) this should work fine all Linux distros,
>>>>> which otherwise would work fine with libfuse2. Is that correct?
>>>>> Also, is there a way to find out which libfuse3 features depend on
>>>>> which Linux kernel, in order to work fine?
>>>>>
>>>>> Thanks,
>>>>> Kiril
>>>
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