Update Manual.md

Manual.md

@@ -3,7 +3,7 @@
 In manual part we are going to see two base example of using ```QEMU``` in order to virtualize
 our system.
 
-## VM Creation
+## 1. VM Creation
 
 In first example we are going to create a virtual machine on our system using ```QEMU```.
 
@@ -46,7 +46,59 @@ After installing Ubuntu, make sure you remove the -cdrom flag from the qemu comm
 qemu-system-x86_64 -enable-kvm -boot menu=on -drive file=Image.img -m 4G -cpu host -vga virtio -display sdl,gl=on
 ```
 
-## CPU Hotplugin
+## 2. Hosting QEMU VMs with Public IP Addresses using TAP Interfaces
+
+To allow VMs to have their own IP addresses while using the same physical link, we need to introduce a bridge into this setup.
+Both the VM’s network interface as well as the host’s interface will be connected to the bridge.
+
+### create bridge
+
+```shell
+ip link add br0 type bridge
+ip link set br0 up
+```
+
+Next, we want to connect the eth0 interface to the bridge and re-assign the IP address from eth0 to br0. Please note that these commands
+will drop internet connectivity of your machine, so either only run them on a local PC or ensure that in case of disaster
+you can reboot the machine somehow.
+```192.168.0.10``` is just an example IP address, you need to use your own of course.
+
+### add ip to bridge
+
+```shell
+ip link set eth0 up
+ip link set eth0 master br0
+
+ip addr flush dev eth0
+
+ip addr add 192.168.0.10/24 brd + dev br0
+ip route add default via 192.168.0.1 dev br0
+```
+
+### tap interface
+
+Next, we can create the TAP interface to be used by the VMs. ```$YOUR_USER``` is used to allow an unprivileged user to connect to the TAP device.
+This is important for QEMU, since QEMU VMs should be started as non-root users.
+
+```shell
+ip tuntap add dev tap0 mode tap user $YOUR_USER
+ip link set dev tap0 up
+ip link set tap0 master br0
+```
+
+### start
+
+And now we can start a VM. The MAC address could e.g. be generated randomly:
+
+```shell
+RAND_MAC=$(printf 'DE:AD:BE:EF:%02X:%02X\n' $((RANDOM%256)) $((RANDOM%256)))
+
+qemu-system-x86_64 -m 1024 -cdrom archlinux-2020.05.01-x86_64.iso \
+   -device virtio-net-pci,netdev=network0,mac=$RAND_MAC \
+   -netdev tap,id=network0,ifname=tap0,script=no,downscript=no
+```
+
+## 3. CPU Hotplugin
 
 Run ```qmp-shell``` (located in the source tree, under ‍‍‍‍```/scripts/qmp/```) to connect to the just-launched **QEMU**:
 
@@ -63,7 +115,7 @@ query-hotpluggable-cpus
 The ```query-hotpluggable-cpus``` command returns an object for CPUs that are present
 (containing a ```qom-path``` member).
 
-## Adding a new vCPU
+### adding a new vCPU
 
 From its output, we can see that **IvyBridge-IBRS-x86_64-cpu** is present in socket 1,
 while hot-plugging a CPU into socket 1 requires passing the listed properties to QMP device_add:
@@ -72,7 +124,7 @@ while hot-plugging a CPU into socket 1 requires passing the listed properties to
 device_add id=cpu-2 driver=IvyBridge-IBRS-x86_64-cpu socket-id=0 core-id=1 thread-id=0
 ```
 
-### Question 1
+#### Question 1
 
 <details>
 
@@ -95,10 +147,14 @@ Optionally, run QMP ```query-cpus-fast``` for some details about the vCPUs:
 query-cpus-fast
 ```
 
-### Removing vCPU
+### removing vCPU
 
 From the ```qmp-shell```, invoke the QMP ```device_del``` command:
 
 ```shell
 device_del id=cpu-2
 ```
+
+## Resources
+
+- [blog.stefan-koch.name](https://blog.stefan-koch.name/2020/10/25/qemu-public-ip-vm-with-tap)