OP25

h1. Extending Wireshark 

The !WireShark packet sniffer normally doesn't support APCO P25. If you want to sniff P25 traffic using !WireShark then you'll need to patch the sources and rebuild it.

h2. Downloading !WireShark

You first need to obtain the source code for !WireShark. The stable release of !WireShark is available from the [http://www.wireshark.org/download.html downloads section of the !WireShark web-site]. On that page you should be go to the "Get !WireShark" for the stable release (1.8.5 at the time of writing). Click on "Source Code" to download the file.

h2. Unpacking !WireShark

To unpack the source tree you need to open a shell and execute the following commands:

@

mkdir -p SourceCode

cd SourceCode

tar xjvf ~/Downloads/wireshark-1.8.5.tar.bz2

cd wireshark-1.8.5

@

(Remember your download directory may not be in ~/Downloads and the version number of !WireShark you download maybe different to that used here).

h2. Patching !WireShark

Once you've downloaded the wireshark source tree, check out p25 plugin:

@(cd plugins && svn checkout http://op25.osmocom.org/svn/trunk/wireshark/plugins/p25 p25)@

This adds the necessary code to !WireShark for it to decode APCO P25 messages. A few small changes also need to be made to the !WireShark tree outside of the plugins directory. To do this the easiest way is to apply the appropriate patch. This can be done as follows:

@

svn checkout http://op25.osmocom.org/svn/trunk/wireshark/patches

patch -p1 < patches/wireshark-1.8.5.patch

@

Of course, it is inevitable that you will download a !WireShark version for which we haven't provided a patch. Don't fret - the patches will probably work for your version but if it fails to apply you may need to download one an earlier version of !WireShark for which we have a patch or make the changes manually using the existing patch as a guide.

h2. Building + Installing !WireShark

You may need to install prerequisites beforehand. These are a minimum set for Ubuntu/Debian based systems:

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sudo apt-get install bison flex libgtk2.0-dev libpcap-dev

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The standard build for wireshark requires that ./autogen.sh be run first. To compile !WireShark run the following commands:

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./autogen.sh && ./configure && make clean && make

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If it compiles cleanly then you can install it as follows:

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sudo make install

@

h2. Using !WireShark to sniff P25

Now you've got a modified !WireShark installed it should be a simple matter to start the receiver and use !WireShark to capture its output. To do so simply sniff on your computer's network interface and use the following capture filter: "udp port 23456". At present all P25 traffic is sent to the multicast address 224.0.0.1 so it should be visible on other computers on your subnet - this allows you to sniff in one place and monitor from another.