Re: [PATCH] tools: add xdp-forwarder

[Alyssa Ross <hi@alyssa.is>]

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Yureka Lilian <yureka@cyberchaos.dev> writes:

> The xdp-forwarder's purpose is implementing the functionality needed
> within the net-vm (a VM running the Linux drivers for any physical
> interfaces on the spectrum system).
>
> In the future, the net-vm will load the included XDP programs on the
> passed-through physical interfaces as well as the downstream virtio
> interface going into the router (recognized by its special MAC address).
>
> The net-vm needs to multiplex between the physical interfaces, as there
> might be several interfaces in the same IOMMU-group.
>
> For this, the XDP program loaded on the physical interfaces
> (`prog_physical.o`) applies a VLAN tag corresponding to the interface id
> and redirects the packets to the router interface (identified by the
> `router_iface` bpf map). In the other direction the XDP program loaded on
> the router interface (`prog_router.o`) removes one layer of VLAN tagging
> and redirects the packets to the interface read from the VLAN tag.
>
> The helper program `set_router_iface` is used to update the `router_iface`
> bpf map to point to the interface passed as argument to the program.
>
> Signed-off-by: Yureka Lilian <yureka@cyberchaos.dev>
> ---
>  pkgs/default.nix                              |   5 +
>  tools/default.nix                             |  15 +-
>  tools/meson.build                             |   5 +
>  tools/meson_options.txt                       |   4 +
>  tools/xdp-forwarder/include/parsing_helpers.h | 273 ++++++++++++++++++
>  tools/xdp-forwarder/include/rewrite_helpers.h | 145 ++++++++++
>  tools/xdp-forwarder/meson.build               |  38 +++
>  tools/xdp-forwarder/prog_physical.c           |  37 +++
>  tools/xdp-forwarder/prog_router.c             |  43 +++
>  tools/xdp-forwarder/set_router_iface.c        |  29 ++
>  10 files changed, 591 insertions(+), 3 deletions(-)
>  create mode 100644 tools/xdp-forwarder/include/parsing_helpers.h
>  create mode 100644 tools/xdp-forwarder/include/rewrite_helpers.h
>  create mode 100644 tools/xdp-forwarder/meson.build
>  create mode 100644 tools/xdp-forwarder/prog_physical.c
>  create mode 100644 tools/xdp-forwarder/prog_router.c
>  create mode 100644 tools/xdp-forwarder/set_router_iface.c
>
> diff --git a/pkgs/default.nix b/pkgs/default.nix
> index 3b81339..76b2a5c 100644
> --- a/pkgs/default.nix
> +++ b/pkgs/default.nix
> @@ -1,4 +1,5 @@
>  # SPDX-FileCopyrightText: 2023-2024 Alyssa Ross <hi@alyssa.is>
> +# SPDX-FileCopyrightText: 2025 Yureka Lilian <yureka@cyberchaos.dev>
>  # SPDX-License-Identifier: MIT
>  
>  { ... } @ args:
> @@ -42,6 +43,10 @@ let
>        guestSupport = false;
>        hostSupport = true;
>      };
> +    spectrum-driver-tools = self.callSpectrumPackage ../tools {
> +      guestSupport = false;
> +      driverSupport = true;
> +    };
>      xdg-desktop-portal-spectrum-host =
>        self.callSpectrumPackage ../tools/xdg-desktop-portal-spectrum-host {};
>  

Probably not copyrightable, since it's not really doing anything new
compared to the other entries.

> diff --git a/tools/default.nix b/tools/default.nix
> index 95d76a1..e664f47 100644
> --- a/tools/default.nix
> +++ b/tools/default.nix
> @@ -1,13 +1,16 @@
>  # SPDX-License-Identifier: MIT
>  # SPDX-FileCopyrightText: 2022-2025 Alyssa Ross <hi@alyssa.is>
> +# SPDX-FileCopyrightText: 2025 Yureka Lilian <yureka@cyberchaos.dev>
>  
>  import ../lib/call-package.nix (
>  { src, lib, stdenv, fetchCrate, fetchurl, runCommand, buildPackages
>  , meson, ninja, pkg-config, rustc
>  , clang-tools, clippy
>  , dbus
> +, clang, libbpf
>  , guestSupport ? true
>  , hostSupport ? false
> +, driverSupport ? false
>  }:
>  
>  let
> @@ -70,15 +73,18 @@ stdenv.mkDerivation (finalAttrs: {
>        ./lsvm
>        ./start-vmm
>        ./subprojects
> +    ] ++ lib.optionals driverSupport [
> +      ./xdp-forwarder
>      ]));
>    };
>    sourceRoot = "source/tools";
>  
>    depsBuildBuild = lib.optionals hostSupport [ buildPackages.stdenv.cc ];
>    nativeBuildInputs = [ meson ninja ]
> -    ++ lib.optionals guestSupport [ pkg-config ]
> -    ++ lib.optionals hostSupport [ rustc ];
> -  buildInputs = lib.optionals guestSupport [ dbus ];
> +    ++ lib.optionals (guestSupport || driverSupport) [ pkg-config ]
> +    ++ lib.optionals hostSupport [ rustc ]
> +    ++ lib.optionals driverSupport [ clang ];
> +  buildInputs = lib.optionals guestSupport [ dbus ] ++ lib.optionals driverSupport [ libbpf ];
>  
>    postPatch = lib.optionals hostSupport (lib.concatMapStringsSep "\n" (crate: ''
>      mkdir -p subprojects/packagecache
> @@ -88,12 +94,15 @@ stdenv.mkDerivation (finalAttrs: {
>    mesonFlags = [
>      (lib.mesonBool "guest" guestSupport)
>      (lib.mesonBool "host" hostSupport)
> +    (lib.mesonBool "driver" driverSupport)
>      "-Dhostfsrootdir=/run/virtiofs/virtiofs0"
>      "-Dtests=false"
>      "-Dunwind=false"
>      "-Dwerror=true"
>    ];
>  
> +  hardeningDisable = lib.optionals driverSupport [ "zerocallusedregs" ];
> +
>    passthru.tests = {
>      clang-tidy = finalAttrs.finalPackage.overrideAttrs (
>        { name, src, nativeBuildInputs ? [], ... }:
> diff --git a/tools/meson.build b/tools/meson.build
> index 9cebd03..e49f27c 100644
> --- a/tools/meson.build
> +++ b/tools/meson.build
> @@ -1,5 +1,6 @@
>  # SPDX-License-Identifier: EUPL-1.2+
>  # SPDX-FileCopyrightText: 2024 Alyssa Ross <hi@alyssa.is>
> +# SPDX-FileCopyrightText: 2025 Yureka Lilian <yureka@cyberchaos.dev>
>  
>  project('spectrum-tools', 'c',
>    default_options : {
> @@ -26,3 +27,7 @@ endif
>  if get_option('guest')
>    subdir('xdg-desktop-portal-spectrum')
>  endif
> +
> +if get_option('driver')
> +  subdir('xdp-forwarder')
> +endif

Same here.

> diff --git a/tools/meson_options.txt b/tools/meson_options.txt
> index 4af0031..887e388 100644
> --- a/tools/meson_options.txt
> +++ b/tools/meson_options.txt
> @@ -1,5 +1,6 @@
>  # SPDX-License-Identifier: EUPL-1.2+
>  # SPDX-FileCopyrightText: 2022-2024 Alyssa Ross <hi@alyssa.is>
> +# SPDX-FileCopyrightText: 2025 Yureka Lilian <yureka@cyberchaos.dev>
>  
>  option('host', type : 'boolean', value : false,
>    description : 'Build tools for the Spectrum host')
> @@ -7,6 +8,9 @@ option('host', type : 'boolean', value : false,
>  option('guest', type : 'boolean',
>    description : 'Build tools for Spectrum guests')
>  
> +option('driver', type : 'boolean',
> +  description : 'Build tools for Spectrum driver VMs')
> +
>  option('hostfsrootdir', type : 'string', value : '/run/host',
>    description : 'Path where the virtio-fs provided by the host will be mounted')
>  

Same here.

> diff --git a/tools/xdp-forwarder/include/parsing_helpers.h b/tools/xdp-forwarder/include/parsing_helpers.h
> new file mode 100644
> index 0000000..3d240cd
> --- /dev/null
> +++ b/tools/xdp-forwarder/include/parsing_helpers.h
> @@ -0,0 +1,273 @@
> +/* SPDX-License-Identifier: (GPL-2.0-or-later OR BSD-2-clause) */
> +/* Vendored from https://github.com/xdp-project/xdp-tutorial/blob/d3d3eed6ea9a63d1302bfa8b5a8e93862bfe11f0/common/parsing_helpers.h */

Here I don't see any copyright header at all.  Is
release/checks/reuse.nix happy?

> diff --git a/tools/xdp-forwarder/meson.build b/tools/xdp-forwarder/meson.build
> new file mode 100644
> index 0000000..7e60c11
> --- /dev/null
> +++ b/tools/xdp-forwarder/meson.build
> @@ -0,0 +1,38 @@
> +# SPDX-License-Identifier: EUPL-1.2+
> +# SPDX-FileCopyrightText: 2025 Yureka Lilian <yureka@cyberchaos.dev>
> +
> +libbpf = dependency('libbpf', version : '1.6.2')
> +
> +executable('set_router_iface', 'set_router_iface.c',
> +  dependencies : libbpf,
> +  install : true)

Minor thing: can we call this set-router-iface?  It's just more common
to see executables with dashes in them than underscares.

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