Add option to use slirp for usermode (#827)

Signed-off-by: Jose Castillo Lema <[email protected]>

Author: josecastillolema

docs/index.md

@@ -836,6 +836,14 @@ kcli create vm -i centos9stream -P nets=['{"name": "default", "type": "e1000"}']
 
 Again, both syntaxes can be combined
 
+It is also possible to leverage user mode networking with a couple of plugins, `slirp` and `passt`, and you can ssh into them
+
+```Shell
+kcli create vm -i centos9stream -P usermode=true vm-passt
+```
+
+By default, passt is used as backend unless not available, in which case we fail back to slirp
+
 ### Injecting files
 
 You can inject a list of `files` in your vms. For instance, to inject a file named myfile.txt, use

docs/index.rst

@@ -862,6 +862,14 @@ Or change the nic driver
 
 Again, both syntaxes can be combined
 
+It is also possible to leverage user mode networking with a couple of plugins, ``slirp`` and ``passt``, and you can ssh into them
+
+.. code:: shell
+
+   kcli create vm -i centos9stream -P usermode=true vm-passt
+
+By default, passt is used as backend unless not available, in which case we fail back to slirp
+
 Injecting files
 ~~~~~~~~~~~~~~~
 

kvirt/keywords.yaml

@@ -139,6 +139,9 @@ tunneldir: Specific directory on the tunnel host where to store ignition files
 tunnelhost: Specific host to use for tunneling console, ssh and scp commands
 tunnelport: Specific port to use for tunneling console, ssh and scp commands
 tunneluser: Specific user to use for tunneling console, ssh and scp commands
+usermode: |
+  Enable user mode networking for the VM. When enabled, the VM will use user mode networking instead of bridged or NAT networking.
+  Automatically sets up port forwarding for SSH (port 22) to a random host port.
 virttype: |
   Only used for libvirt where it evaluates to kvm if acceleration shows in capabilities, or qemu emulation otherwise.
   If a value is provided, it must be either kvm, qemu, xen or lxc

kvirt/providers/kvm/__init__.py

@@ -233,6 +233,7 @@ def create(self, name, virttype=None, profile='kvirt', flavor=None, plan='kvirt'
             self.url = 'qemu:///session'
             userport = common.get_free_port()
             metadata['userport'] = userport
+            metadata['usermode_backend'] = 'passt' if which('passt') is not None else 'slirp'
             usermode = True
         if self.exists(name):
             return {'result': 'failure', 'reason': f"VM {name} already exists"}
@@ -736,9 +737,15 @@ def create(self, name, virttype=None, profile='kvirt', flavor=None, plan='kvirt'
             if netname in ovsnetworks:
                 ovs = True
             if usermode:
-                iftype = 'user'
-                sourcexml = "<backend type='passt'/>"
-                sourcexml += f"<portForward proto='tcp'><range start='{userport}' to='22'/></portForward>"
+                usermode_backend = 'passt' if which('passt') is not None else 'slirp'
+                if usermode_backend == 'slirp':
+                    # Skip libvirt interface for slirp - handled via QEMU command line
+                    continue
+                else:
+                    # Default to passt
+                    iftype = 'user'
+                    sourcexml = "<backend type='passt'/>"
+                    sourcexml += f"<portForward proto='tcp'><range start='{userport}' to='22'/></portForward>"
             elif netname in networks:
                 iftype = 'network'
                 sourcexml = f"<source network='{netname}'/>"
@@ -1097,7 +1104,8 @@ def create(self, name, virttype=None, profile='kvirt', flavor=None, plan='kvirt'
             vcpuxml = f"<vcpu>{numcpus}</vcpu>"
         clockxml = "<clock offset='utc'/>"
         qemuextraxml = ''
-        if ignition or macosx or tpm or qemuextra is not None or nvmedisks:
+        slirp = usermode and which('passt') is None
+        if ignition or macosx or tpm or qemuextra is not None or nvmedisks or slirp:
             namespace = "xmlns:qemu='http://libvirt.org/schemas/domain/qemu/1.0'"
             ignitionxml = ""
             if ignition:
@@ -1139,12 +1147,19 @@ def create(self, name, virttype=None, profile='kvirt', flavor=None, plan='kvirt'
 <qemu:arg value='file={diskpath},format=qcow2,if=none,id=NVME{index}'/>
 <qemu:arg value='-device'/>
 <qemu:arg value='nvme,drive=NVME{index},serial=nvme-{index}'/>""".format(index=index, diskpath=diskpath)
+            slirpxml = ""
+            if slirp:
+                slirpxml = f"""<qemu:arg value='-netdev'/>
+<qemu:arg value='user,id=net0,hostfwd=tcp::{userport}-:22'/>
+<qemu:arg value='-device'/>
+<qemu:arg value='virtio-net-pci,netdev=net0,addr=0x10'/>"""
             qemuextraxml = """<qemu:commandline>
 {ignitionxml}
 {macosxml}
 {freeformxml}
 {nvmexml}
-</qemu:commandline>""".format(ignitionxml=ignitionxml, macosxml=macosxml, freeformxml=freeformxml, nvmexml=nvmexml)
+{slirpxml}
+</qemu:commandline>""".format(ignitionxml=ignitionxml, macosxml=macosxml, freeformxml=freeformxml, nvmexml=nvmexml, slirpxml=slirpxml)
         sharedxml = ""
         if sharedfolders:
             for folder in sharedfolders: