From: John Fastabend <john.fastabend@gmail.com>
To: Louis DeLosSantos <louis.delos.devel@gmail.com>,
bpf@vger.kernel.org, netdev@vger.kernel.org
Cc: Martin KaFai Lau <martin.lau@linux.dev>,
Stanislav Fomichev <sdf@google.com>,
razor@blackwall.org,
Louis DeLosSantos <louis.delos.devel@gmail.com>
Subject: RE: [PATCH 1/2] bpf: add table ID to bpf_fib_lookup BPF helper
Date: Thu, 25 May 2023 23:48:12 -0700 [thread overview]
Message-ID: <6470562cac756_2023020893@john.notmuch> (raw)
In-Reply-To: <20230505-bpf-add-tbid-fib-lookup-v1-1-fd99f7162e76@gmail.com>
Louis DeLosSantos wrote:
> Add ability to specify routing table ID to the `bpf_fib_lookup` BPF
> helper.
>
> A new field `tbid` is added to `struct bpf_fib_lookup` used as
> parameters to the `bpf_fib_lookup` BPF helper.
>
> When the helper is called with the `BPF_FIB_LOOKUP_DIRECT` flag and the
> `tbid` field in `struct bpf_fib_lookup` is greater then 0, the `tbid`
> field will be used as the table ID for the fib lookup.
>
> If the `tbid` does not exist the fib lookup will fail with
> `BPF_FIB_LKUP_RET_NOT_FWDED`.
>
> The `tbid` field becomes a union over the vlan related output fields in
> `struct bpf_fib_lookup` and will be zeroed immediately after usage.
>
> 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.
>
> Signed-off-by: Louis DeLosSantos <louis.delos.devel@gmail.com>
> ---
> include/uapi/linux/bpf.h | 17 ++++++++++++++---
> net/core/filter.c | 12 ++++++++++++
> tools/include/uapi/linux/bpf.h | 17 ++++++++++++++---
> 3 files changed, 40 insertions(+), 6 deletions(-)
>
Looks good one question. Should we hide tbid behind a flag we have
lots of room. Is there any concern a user could feed a bpf_fib_lookup
into the helper without clearing the vlan fields? Perhaps by
pulling the struct from a map or something where it had been
previously used.
Thanks,
John
next prev parent reply other threads:[~2023-05-26 6:48 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-05-25 14:27 [PATCH 0/2] bpf: utilize table ID in bpf_fib_lookup helper Louis DeLosSantos
2023-05-25 14:27 ` [PATCH 1/2] bpf: add table ID to bpf_fib_lookup BPF helper Louis DeLosSantos
2023-05-26 6:01 ` Yonghong Song
2023-05-26 14:11 ` Louis DeLosSantos
2023-05-26 6:48 ` John Fastabend [this message]
2023-05-26 14:07 ` Louis DeLosSantos
2023-05-26 16:58 ` Yonghong Song
2023-05-25 14:28 ` [PATCH 2/2] bpf: test table ID fib lookup " Louis DeLosSantos
2023-05-26 6:02 ` Yonghong Song
2023-05-26 14:23 ` Louis DeLosSantos
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