This patchset adds the ability to specify a table ID to the `bpf_fib_lookup` BPF helper. A new `tbid` field is added to `struct fib_bpf_lookup`. When the `fib_bpf_lookup` helper is called with the `BPF_FIB_LOOKUP_DIRECT` and `BPF_FIB_LOOKUP_TBID' flag the `tbid` field will be interpreted as the table ID to use for the fib lookup. If the `tbid` specifies a table that does not exist the lookup fails with `BPF_FIB_LKUP_RET_NOT_FWDED` This functionality is useful in containerized environments. For instance, if a CNI wants to dictate the next-hop for traffic leaving a container it can create a container-specific routing table and perform a fib lookup against this table in a "host-net-namespace-side" TC program. This functionality also allows `ip rule` like functionality at the TC layer, allowing an eBPF program to pick a routing table based on some aspect of the sk_buff. As a concrete use case, this feature will be used in Cilium's SRv6 L3VPN datapath. When egress traffic leaves a Pod an eBPF program attached by Cilium will determine which VRF the egress traffic should target, and then perform a FIB lookup in a specific table representing this VRF's FIB. The existing `fib_lookup.c` bpf selftest was appended several test cases to ensure this feature works as expected. ``` $ sudo ./test_progs -a "*fib*" Summary: 1/0 PASSED, 0 SKIPPED, 0 FAILED ``` Signed-off-by: Louis DeLosSantos <louis.delos.devel@xxxxxxxxx> --- Changes in v2: - Utilize a new flag `BPF_FIB_LOOKUP_TBID` for performing table ID fib lookups. - Update fib lookup selftest to reflect new flag usage. - Change second commit message subject to `selftests/bpf`. - Link to v1: https://lore.kernel.org/r/20230505-bpf-add-tbid-fib-lookup-v1-0-fd99f7162e76@xxxxxxxxx --- Louis DeLosSantos (2): bpf: add table ID to bpf_fib_lookup BPF helper selftests/bpf: test table ID fib lookup BPF helper include/uapi/linux/bpf.h | 21 ++++++-- net/core/filter.c | 14 ++++- tools/include/uapi/linux/bpf.h | 21 ++++++-- .../testing/selftests/bpf/prog_tests/fib_lookup.c | 61 +++++++++++++++++++--- 4 files changed, 102 insertions(+), 15 deletions(-) --- base-commit: fbc0b0253001c397a481d258a88ce5f08996574f change-id: 20230505-bpf-add-tbid-fib-lookup-aa46fa098603 Best regards, -- Louis DeLosSantos <louis.delos.devel@xxxxxxxxx>
