Re: Adding libxml2 as optional Wireshark dependency

[Ahmad Fatoum <ahmad.fatoum () gmail com>]

No, I am using libxml2 for parsing the XML (xdd.c in the linked Github
repository).
Giving the user the option to toggle XSD validation would be a nice thing
to have in a future version though.

On Wed, Apr 5, 2017 at 4:36 PM, Graham Bloice <graham.bloice () trihedral com>
wrote:

> On 5 April 2017 at 15:30, Ahmad Fatoum <ahmad () a3f at> wrote:
>
> > I can't comment on the Windows binary distribution issue but Pascal's
> > suggestion of using SUSE's sounds promising. I will attempt building on
> > Windows and comment on the Gerrit issue later today.
> >
> > Ethernet POWERLINK specifies XML Device Description (XDD) as its sole
> > format [1].
>
> I see the format specifies an xsd, are you using LibXml2 in "validation"
> mode to ensure the device XML files are well-formed?
>
>
> > EDS (Windows .ini-like format) files are used occasionally, owing to its
> > CANopen roots, but are much less common in usage. Commercial tools as well
> > as openPOWERLINK generate XML files.
> >
> > The revised dissector [2] also supports EDS via Glib's GKeyFile
> > unconditionally.
> >
> > [1] http://www.ethernet-powerlink.org/en/downloads/technical-doc
> > uments/action/open-download/download/epsg-311-v110-ds-xml-
> > device-description/?no_cache=1
> > [2] https://github.com/epl-viz/dissector (Needs to be converted back to
> > a static dissector)
> >
> > On Wed, Apr 5, 2017 at 3:38 PM, Graham Bloice <
> > graham.bloice () trihedral com> wrote:
> >
> > > 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.
> > >
> > > 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])?
> > >
> > > 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.
> > >
> > > 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?
> > >
> > >
> > > [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
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