Re: [PATCH v4 2/5] tools: add xdp-forwarder

Alyssa Ross
2025-09-23T15:17:02Z

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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.
>
> Co-authored-by: Demi Marie Obenour <demiobenour@gmail.com>
> Signed-off-by: Yureka Lilian <yureka@cyberchaos.dev>
> ---
> pkgs/default.nix | 4 +
> release/checks/pkg-tests.nix | 1 +
> tools/default.nix | 15 +-
> tools/meson.build | 4 +
> tools/meson_options.txt | 3 +
> tools/xdp-forwarder/include/parsing_helpers.h | 274 ++++++++++++++++++
> tools/xdp-forwarder/include/rewrite_helpers.h | 146 ++++++++++
> tools/xdp-forwarder/meson.build | 48 +++
> tools/xdp-forwarder/prog_physical.c | 39 +++
> tools/xdp-forwarder/prog_router.c | 43 +++
> tools/xdp-forwarder/set_router_iface.c | 30 ++
> 11 files changed, 604 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

release/checks/pkg-tests.nix fails with this patch applied, because
clang-tidy can't find headers. I'm happy to look into why that is, but
if you feel like having a look or already know what's happening, please
let me know!

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