infra/common: document tap interface setup procedure

The platform FVP supports virtual ethernet interface to allow networking
support to be usable for the software executed by the FVP. If support
for networking is required, the host TAP interface has to be setup
before the FVP is launched. Document the steps required to setup the
TAP interface on this host machine.

Signed-off-by: Aditya Angadi <aditya.angadi@arm.com>
Change-Id: I7599711781fa2ca1c18ff3bdc70aaf67614d605a

docs/infra/common/download-sources.rst

@@ -155,6 +155,31 @@ workspace.
   cd ../..
 
 
+Setting up TAP interface (optional)
+-----------------------------------
+
+The platform FVP supports virtual ethernet interface to allow networking
+support to be usable for the software executed by the FVP. If support
+for networking is required, the host TAP interface has to be setup
+before the FVP is launched. To setup the TAP interface, execute the
+following commands on the host machine.
+
+- Install libvirt-bin
+
+  ::
+
+    sudo apt-get install libvirt-bin
+
+- Create a tap interface named 'tap0'
+
+  ::
+
+    sudo ip tuntap add dev tap0 mode tap user $(whoami)
+    sudo ifconfig tap0 0.0.0.0 promisc up
+    sudo brctl addif virbr0 tap0
+
+
+
 This completes the procedure to download the platform software stack, setup
 of the GCC toolchain binaries and installation of the other prerequisites.