Re: Adding libxml2 as optional Wireshark dependency

[Graham Bloice <graham.bloice () trihedral com>]

On 5 April 2017 at 14:48, Pascal Quantin <pascal.quantin () gmail com> wrote:

> Hi Ahmad and Graham,
>
> 2017-04-05 15:38 GMT+02:00 Graham Bloice <graham.bloice () trihedral com>:
>
> > On 5 April 2017 at 14:11, Ahmad Fatoum <ahmad () a3f at> wrote:
> >
> > > Hello everyone,
> > >
> > > I was advised on Gerrit to post this issue here as to garner wider input.
> > >
> > > This concerns proposed Change-Id I13c0a2f408fb5c21bad7ab3d7971e
> > > 0fa8ed7d783 [1] intending to add libxml2 as optional dependency to
> > > Wireshark.
> > >
> > > I am currently preparing to submit upstream, changes I did to the EPL v2
> > > dissector (packet-epl.c).
> > >
> > > A significant change is the ability to optionally read in user-supplied
> > > XML device descriptions and to extract type/description/mapping information
> > > for aiding the dissection. See this previous submission of mine to the
> > > mailing list: https://www.wireshark.org/lists/wireshark-dev/201701/m
> > > sg00154.html
> > >
> > >
> > > Seeing as there also has been interest for libxml2 support in dissectors
> > > in the past:
> > >
> > > https://www.wireshark.org/lists/wireshark-dev/201005/msg00108.html
> > >
> > > https://ask.wireshark.org/questions/36063/using-libxml2-in-m
> > > y-own-dissector
> > >
> > >
> > > I think, it would be a good idea to have this as optional dependency as
> > > Glib's GMarkup may be inadequate or inconvenient for parsing actual XML.
> > >
> > >
> > > Looking forward to your feedback.
> > >
> > > Best regards,
> > > Ahmad Fatoum
> > >
> > > [1] https://code.wireshark.org/review/#/c/20912/
> > Thanks for the post,
> >
> > 1.  Where will the Windows binaries come from and are these supported
> > long term?  The  libXml2 downloads page indicates another site provides
> > Windows binaries [1].  The binaries at that site in the 64 bit directory
> > seem to be the most recent and are labelled as libXml2-2.9.3 [2].  The
> > current release of libXml2 is 2.9.4 which has a number of security fixes
> > among other bug fixes and enhancements [3] so it would appear that the
> > Windows binaries are not being maintained.
>
> I suggest to use the binaries provided by openSUSE: they provide win32 and
> win64 variants for libxml2 2.9.0 and we are already using their packages
> for several third party libraries. If it is really required to take the
> latest version, I can probbly give it a try (I already did this in the past
> to package a newer version than the one from openSUSE).

That sounds good, I think for a new package we should use the latest
available to ensure we pick up all known security issues. LibXml2 2.9.4 was
released in May last year and 2.9.0 in Sep 2012.  I realise I'm attempting
to volunteer you for this task Pacal ;-)


> > 2.  According to the diagram at [1], libXml2 depends on iconv and zlib.
> > We currently build our own zlib, will that be suitable for the libXml2
> > dependency?  What will be the source of the iconv binary (iconv-1.14 is
> > available in the same download area as libXml2 [2])?
>
> Same thing: we can use the ones provided by openSUSE (we already have
> those dependencies for other packages).

iconv doesn't seem to be in the latest Wireshark builds (2.3.x). I think
iconv was required for GTK, regardless it seems that libXml2 requires it.
We will need to check that the OpenSUSE libXml2 is happy with our
built-from-source zlib.


> > 3. The readme.txt in the download area ([2]) has some "interesting" text:
> >
> > These are experimental 64bit binaries. For completeness, 32bit binaries
> > built using the same method are also included.
> >
> > The libraries in these packages are made using GCC (MinGW) toolchain. It is
> > presently not possible to use these libraries with any recent version of the
> > Microsoft Visual C compiler because of conflicting C-runtimes. To help you
> > resist the temptation, the import libraries (.LIB) are not provided at all.
> > If you need these libraries in an environment which mandates the use of the
> > Microsoft toolchain, you will have to build them from source yourself.
> >
> > and inspection of the download shows this is true, so it appears that
> > we'll need to rebuild to obtain the import .lib file.
>
> As part of the process of integrating openSUSE libraries, we are
> generating the .lib file and adding it in the package we upload on our
> server, so it should be OK.
>
>
> > 4. Microsoft have a Visual Studio porting effort underway called vcpkg
> > [4], that does include libXml2, but unfortunately is only for VS2015 or
> > later.  If we move to VS2015 for main releases (post 2.4 release) then this
> > may be a viable source for libXml2 and other packages we use.  It might be
> > possible to use this to build VS2013 libXml2.
> >
> > 5.  Are there any manufacturers or tools that produce XML device
> > description files for the EPL dissector such that choosing XML as the input
> > format is the most sensible choice, or would another format be just as
> > applicable?
>
> I agree XML can be painful, so this is a good question ;)
>
>
> > [1]: https://www.zlatkovic.com/libxml.en.html
> > [2]: ftp://ftp.zlatkovic.com/libxml/64bit/
> > [3]: http://xmlsoft.org/news.html
> > [4]: https://github.com/Microsoft/vcpkg
> >
> > --
> > Graham Bloice

-- 
Graham Bloice

___________________________________________________________________________
Sent via:    Wireshark-dev mailing list <wireshark-dev () wireshark org>
Archives:    https://www.wireshark.org/lists/wireshark-dev
Unsubscribe: https://www.wireshark.org/mailman/options/wireshark-dev
             mailto:wireshark-dev-request () wireshark org?subject=unsubscribe