Re: Cannot get external capture (extcap) interface to work with my new plugin.

[Dario Lombardo <lomato () gmail com>]

You cannot trace your code using prints because they're handled by the
caller (dumpcap). Have a look at the other extcaps for --debug and
--debug-file options to see how it's solved there.

On Wed, Jan 2, 2019, 17:40 hdv <henri.de.veer () gmail com wrote:

> I actually found the issue(s), there were multiple issues stacked on top
> of each other:
>
> 1) When using parameters and you fill in the default value in the dialog
> before you start the capture, these parameters are not passed to the extcap
> plugin. My assumption was that the parameters would always be passed.
>
> This resulted in my plugin in a null pointer for the hostname (one of the
> parameters called "host" in my case) that needed to be resolved.
> Unfortunately no program crash occurs or any trap was generated. So it was
> not seen. I fixed this by copying the default hostname/ip-number before
> parsing all the command line options in my final parameter structure.
>
> So probably the program was just hanging in some loop/deadlock.
>
> => This was the main reason that tshark did work because I supplied the
> --host=192.168.2.51 argument so all went well.
>
> 2) The function gethostbyname() does not work on the W8.1 system I have
> for some strange reason. Even when I fixed the issue with the null hostname
> I still did not get any resolved hostname (gethostbyname returned an empty
> list: no error). I had to rewrite the code to use getaddrinfo(), that does
> the job.
>
> PS: Roland, the flush is already present in the code.
> This brings me to some other question: How can I trace my code flow from
> within the wireshark gui?
> I would expect that it will end up in the window that I can open in the
> left lower corner of wireshark.
>
> It is not clear to me how to do this. I tried some of the
> g_debug/g_message/g_info calls but it does not end up anywhere or displays
> a popup or crashes the program with a debugger trap call.
> So it took me quite some time to figure out what went wrong because I
> could not "peek" into the system in a simple way.
>
> Henri
> On 30-12-2018 18:18, Roland Knall wrote:
>
> Hi
>
> Have you properly closed the pipe after sending the packets? It looks more
> like an issue in flushing the pipe, then a code error. tshark handles this
> a little bit different then wireshark, so that might be the reason, why it
> did work on the CLI.
>
> Try flushing the pipe immediately after every packet. Otherwise, without
> the code nothing much can be said.
>
> kind regards
> Roland
>
> Am So., 30. Dez. 2018 um 17:39 Uhr schrieb hdv <henri.de.veer () gmail com>:
>
> > Hello,
> >
> > I'm developing a new extcap interface as described in chapter 8.2.1 of
> > the developers guide. The goal is to implement a plugin so I can directly
> > attach it to a CAN bus sniffing device called "AnaGate CAN" (see
> > http://www.anagate.de/)
> >
> > Until now all went well, I can see my new interface in the main wireshark
> > window, select it, all choose all options etc.
> >
> > I just implemented 2 dummy packets in my plugin before I continue to
> > access the real target hardware (to avoid the hassle of setting up a
> > working CAN network). The intention is to check if the interface is correct
> > between my program and the main wireshark code.
> >
> > When running my capture interface as follow:
> >
> > extcap\anagate.exe  --host=192.168.2.51 --port=5001 --fifo=myfifo
> > --capture
> >
> > I nicely get a file (in libpcap format)  "myfifo" with a header and 2 CAN
> > bus packets, which I can open in wireshark and show me the correct
> > content.  (See attached file)
> >
> > But when I start the capture from wireshark itself no packets are shown
> > and no errors at all. The status bar says "Life capture in progress" and at
> > the right "No Packets".
> >
> > When running it via tshark with: tshark -i 4   It does return the 2
> > packets. So that is weird.
> >
> > P.S. The random packet generator plugin does work, so the core wireshark
> > code does not look broken.
> >
> > So what is going on here? Any pointers on how to debug this in the core
> > wireshark code.
> >
> > Can anyone give me an advice how to proceed?
> >
> > Thanks,
> >
> > Henri
> >
> >
> > Wireshark version build:
> >
> > Version 2.9.0 (v2.9.0rc0-990-g27a1906c)
> >
> > Copyright 1998-2018 Gerald Combs <gerald () wireshark org>
> > <gerald () wireshark org> and contributors. License GPLv2+: GNU GPL version
> > 2 or later <http://www.gnu.org/licenses/old-licenses/gpl-2.0.html>
> > <http://www.gnu.org/licenses/old-licenses/gpl-2.0.html> This is free
> > software; see the source for copying conditions. There is NO warranty; not
> > even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
> >
> > Compiled (64-bit) with Qt 5.11.1, with WinPcap (4_1_3), with GLib 2.52.2,
> > with zlib 1.2.11, with SMI 0.4.8, with c-ares 1.14.0, with Lua 5.2.4, with
> > GnuTLS 3.4.11, with Gcrypt 1.7.6, with MIT Kerberos, with MaxMind DB
> > resolver, with nghttp2 1.14.0, with LZ4, with Snappy, with libxml2 2.9.4,
> > with QtMultimedia, with AirPcap, with SBC, with SpanDSP, with bcg729.
> >
> > Running on 64-bit Windows 8.1, build 9600, with Intel(R) Core(TM)
> > i7-3632QM CPU @ 2.20GHz (with SSE4.2), with 8084 MB of physical memory,
> > with locale Dutch_Netherlands.1252, with WinPcap version 4.1.3 (packet.dll
> > version 4.1.0.2980), based on libpcap version 1.0 branch 1_0_rel0b
> > (20091008), with GnuTLS 3.4.11, with Gcrypt 1.7.6, with AirPcap 4.1.0 build
> > 1622, binary plugins supported (14 loaded). Built using Microsoft Visual
> > C++ 14.0 build 24215
> >
> >
> > <#m_-890730549634902410_m_9187531828630989062_DAB4FAD8-2DD7-40BB-A1B8-4E2AA1F9FDF2>
> >
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