message: add description of uhyve's network interface
diff: @@ -220,10 +220,11 @@ With `HERMIT_ISLE=qemu`, the application will be started within a QEMU VM.
  Please note that the loader requires QEMU and uses per default *KVM*.
  Furthermore, it expects that the executable is called `qemu-system-x86_64`.
  -With `HERMIT_ISLE=hyve`, the application will be started within a thin
  +With `HERMIT_ISLE=uhyve`, the application will be started within a thin
  hypervisor powered by Linux's KVM API and therefore requires *KVM* support.
  -uHyve has a considerably smaller startup time than QEMU, but lacks some features
  +uhyve has a considerably smaller startup time than QEMU, but lacks some features
  such as GDB debugging.
  +In principle, it is an extension of [ukvm](https://www.usenix.org/sites/default/files/conference/protected-files/hotcloud16_slides_williams.pdf).
  In this context, the environment variable `HERMIT_CPUS` specifies the number of
  cpus (and no longer a range of core ids). Furthermore, the variable `HERMIT_MEM`
  @@ -231,6 +232,26 @@ defines the memory size of the virtual machine. The suffix of *M* or *G* can be
  used to specify a value in megabytes or gigabytes respectively. Per default, the
  loader initializes a system with one core and 2 GiB RAM.
  +To enable an ethernet device for `uhyve`, we have to setup a tap device on the
  +host system. For instance, the following command establish a tap device
  +`tap100` on Linux:
  +
  +```bash
  +$ sudo ip tuntap add tap100 mode tap
  +$ sudo ip addr add 10.0.5.1/24 dev tap100
  +$ sudo ip link set dev tap100 up
  +```
  +
  +Per default, `uhyve`'s network interface uses `10.0.5.2`as IP address.
  +The default address, could be overloaded by the environment variable `HERMIT_IP`:
  +To enable the device, `HERMIT_NETIF` has to set the name of the tap device.
  +For instance, the following command starts an HermitCore application with `uhyve`
  +and network support:
  +
  +```bash
  +$ HERMIT_ISLE=uhyve HERMIT_IP="10.0.5.2" HERMIT_NETIF=tap100 bin/proxy x86_64-hermit/extra/tests/hello
  +```
  +
  The virtual machine opens two TCP/IP ports. One is used for the communication
  between HermitCore application and its proxy. The second port is used to create
  a connection via telnet to QEMU's system monitor. With the environment variable
  