krunkit: Support --fd

Latest krunkit can use a file descriptor instead of unix socket. Update
the krunkit command to support this. Since krunkit behaves like vfkit
and qemu, we can remove the special "auto" connection.

Depends on:
- libkrun/krunkit#63
- containers/libkrun#402

Author: nirs

example

@@ -14,12 +14,6 @@ import sys
 
 import vmnet
 
-CONNECTION_AUTO = {
-    "vfkit": "fd",
-    "krunkit": "socket",
-    "qemu": "fd",
-}
-
 VMNET_OFFLOAD_AUTO = {
     "vfkit": "off",
     "krunkit": "off",
@@ -36,9 +30,9 @@ def main():
     p.add_argument("vm_name", help="VM name")
     p.add_argument(
         "--connection",
-        choices=["auto", "fd", "socket", "client"],
-        default="auto",
-        help="How to connect the helper and vm (auto)",
+        choices=["fd", "socket", "client"],
+        default="fd",
+        help="How to connect the helper and vm (fd)",
     )
 
     # Helper arguments
@@ -118,9 +112,6 @@ def main():
 
     args = p.parse_args()
 
-    if args.connection == "auto":
-        args.connection = CONNECTION_AUTO[args.driver]
-
     if args.operation_mode == "bridged" and not args.shared_interface:
         p.error("--shared-interface required for --operation-mode=bridged")
 

vmnet/vm.py

@@ -171,21 +171,27 @@ def vfkit_command(self):
         return cmd
 
     def krunkit_command(self):
-        if self.fd is not None:
-            raise ValueError("fd connection not supported for krunkit driver")
-        if self.socket is None:
-            raise ValueError("socket connection required")
-        return [
+        cmd = [
             self.driver_command or "krunkit",
             f"--memory={self.memory}",
             f"--cpus={self.cpus}",
             f"--restful-uri=none://",
             f"--device=virtio-blk,path={self.disk['image']}",
             f"--device=virtio-blk,path={self.cidata}",
-            f"--device=virtio-net,type=unixgram,path={self.socket},mac={self.mac_address},offloading={self.vmnet_offload}",
             f"--device=virtio-serial,logFilePath={self.serial}",
             "--krun-log-level=3",
         ]
+        if self.fd is not None:
+            cmd.append(
+                f"--device=virtio-net,type=unixgram,fd={self.fd},mac={self.mac_address},offloading={self.vmnet_offload}",
+            )
+        elif self.socket is not None:
+            cmd.append(
+                f"--device=virtio-net,type=unixgram,path={self.socket},mac={self.mac_address},offloading={self.vmnet_offload}",
+            )
+        else:
+            raise ValueError("fd or socket required")
+        return cmd
 
     def qemu_command(self):
         if self.fd is not None: