A few more things I just found. Happy to just make the fixes myself when I apply the patch if you prefer — just let me know what you think. 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> Signed-off-by: Demi Marie Obenour <demiobenour@gmail.com> --- pkgs/default.nix | 4 + release/checks/pkg-tests.nix | 1 + tools/default.nix | 21 +-
tools/shell.nix should also set driverSupport = true so libbpf is available in the development shell.
tools/meson.build | 4 + tools/meson_options.txt | 3 + tools/xdp-forwarder/meson.build | 48 +++++ tools/xdp-forwarder/parsing_helpers.h | 274 +++++++++++++++++++++++++ tools/xdp-forwarder/prog_physical.c | 39 ++++ tools/xdp-forwarder/prog_router.c | 42 ++++ tools/xdp-forwarder/rewrite_helpers.h | 146 +++++++++++++ tools/xdp-forwarder/set_router_iface.c | 30 +++ 11 files changed, 608 insertions(+), 4 deletions(-) create mode 100644 tools/xdp-forwarder/meson.build create mode 100644 tools/xdp-forwarder/parsing_helpers.h create mode 100644 tools/xdp-forwarder/prog_physical.c create mode 100644 tools/xdp-forwarder/prog_router.c create mode 100644 tools/xdp-forwarder/rewrite_helpers.h create mode 100644 tools/xdp-forwarder/set_router_iface.c
diff --git a/tools/xdp-forwarder/meson.build b/tools/xdp-forwarder/meson.build new file mode 100644 index 0000000..9b70ce3 --- /dev/null +++ b/tools/xdp-forwarder/meson.build @@ -0,0 +1,48 @@ +# SPDX-License-Identifier: EUPL-1.2+ +# SPDX-FileCopyrightText: 2025 Yureka Lilian <yureka@cyberchaos.dev> +# SPDX-FileCopyrightText: 2025 Demi Marie Obenour <demiobenour@gmail.com> + +libbpf = dependency('libbpf', version : '1.6.2')
This is an exact version match, which means we'll have to change it every time libbpf updates in Nixpkgs. Do you know what a more appropriate version constraint would be?
+ +executable('set-router-iface', 'set_router_iface.c', + dependencies : libbpf, + install : true) + +clang = find_program('clang', native: true) + +bpf_o_cmd = [ + clang.full_path(), + '-fno-stack-protector', + '-fno-strict-aliasing', + '-fwrapv', '-fwrapv-pointer', + '-Wall', + '-Wextra',
When I built in a Nix shell I got warnings from -Wcompare-distinct-pointer-types and -Wsign-compare, coming from the vendored headers. Should I just silence those? (A quick look at the kernel suggests the distinct pointer type comparison is probably fine, but that the sign comparison issue should probably be fixed upstream.)
+ '-O2', + '-target', 'bpf', + '-I', meson.current_source_dir() + '/include', + '-g', + '-c', + '-o', '@OUTPUT@', + '-MD', + '-MP', + '-MF', '@DEPFILE@', + '--', + '@INPUT@', +] + +prog_router_o = custom_target( + input : 'prog_router.c', + output : 'prog_router.o', + depfile : 'prog_router.o.dep', + command : bpf_o_cmd, + install: true, + install_dir: 'lib/xdp') + +prog_physical_o = custom_target( + input : 'prog_physical.c', + output : 'prog_physical.o', + depfile : 'prog_physical.o.dep', + command : bpf_o_cmd, + install: true, + install_dir: 'lib/xdp') +