From b70c8ee258d89c0ce850d49bea26e0a5c3fdcceb Mon Sep 17 00:00:00 2001
From: Daniel Barlow <dan@telent.net>
Date: Tue, 9 May 2023 22:58:56 +0100
Subject: [PATCH] support USB ethernet in bordervm

---
 bordervm-configuration.nix | 47 ++++++++++++++++++++++++++------------
 bordervm.conf-example.nix  |  3 ++-
 doc/developer.rst          |  6 +++--
 3 files changed, 39 insertions(+), 17 deletions(-)

diff --git a/bordervm-configuration.nix b/bordervm-configuration.nix
index 6803dea..29b74d7 100644
--- a/bordervm-configuration.nix
+++ b/bordervm-configuration.nix
@@ -1,7 +1,7 @@
 { config, pkgs, lib, ... }:
 let
   cfg = config.bordervm;
-  inherit (lib) mkOption mdDoc types;
+  inherit (lib) mkOption mkEnableOption mdDoc types optional optionals;
 in {
   options.bordervm = {
     l2tp = {
@@ -22,14 +22,28 @@ in {
       };
     };
     ethernet = {
-      pciId = mkOption {
-        description = ''
-          Host PCI ID (as shown by `lspci`) of the ethernet adaptor
-          to be used by the VM. This uses VFIO and requires setup
-          on the emulation host before it will work!
-        '';
-        type = types.str;
-        example = "04:00.0";
+      pci = {
+        enable = mkEnableOption "passthru PCI ethernet";
+        id = mkOption {
+          description = ''
+            Host PCI ID (as shown by `lspci`) of the ethernet adaptor
+            to be used by the VM. This uses VFIO and requires setup
+            on the emulation host before it will work!
+          '';
+          type = types.str;
+          example = "04:00.0";
+        };
+      };
+      usb = {
+        enable = mkEnableOption "passthru USB ethernet";
+        vendor = mkOption {
+          type = types.str;
+          example = "0x0bda";
+        };
+        product = mkOption {
+          type = types.str;
+          example = "0x8153";
+        };
       };
     };
   };
@@ -66,11 +80,16 @@ in {
     virtualisation = {
       qemu = {
         networkingOptions = [];
-        options = [
-          "-device vfio-pci,host=${cfg.ethernet.pciId}"
-          "-nographic"
-          "-serial mon:stdio"
-        ];
+        options = [] ++
+          optional cfg.ethernet.pci.enable
+            "-device vfio-pci,host=${cfg.ethernet.pci.id}" ++
+          optionals cfg.ethernet.usb.enable [
+            "-device usb-ehci,id=ehci"
+            "-device usb-host,bus=ehci.0,vendorid=${cfg.ethernet.usb.vendor},productid=${cfg.ethernet.usb.product}"
+          ] ++ [
+            "-nographic"
+            "-serial mon:stdio"
+          ];
       };
       sharedDirectories = {
         liminix = {
diff --git a/bordervm.conf-example.nix b/bordervm.conf-example.nix
index 0df7434..a27b045 100644
--- a/bordervm.conf-example.nix
+++ b/bordervm.conf-example.nix
@@ -1,7 +1,8 @@
 {...}:
 {
   bordervm = {
-    ethernet.pciId = "01:00.0";
+    # ethernet.pci = { id = "01:00.0"; enable = true; };
+    ethernet.usb = { vendor = "0x0bda"; product = "0x8153"; enable = true; };
     l2tp = {
       host = "l2tp.aa.net.uk";
     };
diff --git a/doc/developer.rst b/doc/developer.rst
index bc18e2f..4666c09 100644
--- a/doc/developer.rst
+++ b/doc/developer.rst
@@ -139,11 +139,13 @@ router from the internet so you can borrow the cable/fibre/DSL.
 
 ``bordervm`` is included for this purpose. You will need
 
-* a Linux machine with a spare PCI ethernet card which you can dedicate to Liminix
+* a Linux machine with a spare (PCI or USB) ethernet device which you can dedicate to Liminix
 
 * an L2TP service such as https://www.aa.net.uk/broadband/l2tp-service/
 
-You need to configure the Ethernet card for VFIO passthru, then
+You need to "hide" the Ethernet device from the host - for PCI this
+means configuring it for VFIO passthru; for USB you need to
+unload the module(s) it uses. Then
 you can execute :command:`run-border-vm` in a ``buildEnv`` shell,
 which starts up QEMU using the NixOS configuration in
 :file:`bordervm-configuration.nix`.