Update docs concerning Calico

README.md

@@ -39,7 +39,7 @@ The demo will start a test cluster, deploy Virtlet on it and then boot a [CirrOS
 examples/vmssh.sh cirros@cirros-vm [command...]
 ```
 
-By default, CNI bridge plugin is used for cluster networking. It's also possible to override this with `flannel` or `weave` plugin, e.g.:
+By default, CNI bridge plugin is used for cluster networking. It's also possible to override this with `calico`, `flannel` or `weave` plugin, e.g.:
 ```
 CNI_PLUGIN=flannel ./demo.sh
 ```

docs/networking.md

@@ -81,5 +81,11 @@ socket makes it possible to have all the network related code outside
 `vmwrapper` and have `vmwrapper` just `exec` the emulator instead of
 spawning it as a child process.
 
+[Calico](https://www.projectcalico.org/) CNI plugin needs special treatment
+as it tries to pass a routing configuration that cannot be passed
+over DHCP. For it to work Virtlet patches Calico-provided CNI result,
+replacing Calico's unreachable fake gateway with another fake gateway
+with an IP address acquired from Calico IPAM.
+
 **NOTE:** Virtlet doesn't support `hostNetwork` pod setting because it
 cannot be impelemnted for VM in a meaningful way.