From 8ad77e72caae22a1ddcfd0c03f2884929e93b7a4 Mon Sep 17 00:00:00 2001 From: Louis DeLosSantos Date: Wed, 31 May 2023 15:38:48 -0400 Subject: bpf: Add table ID to bpf_fib_lookup BPF helper 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` and `BPF_FIB_LOOKUP_TBID` flags the `tbid` field in `struct bpf_fib_lookup` 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 Signed-off-by: Daniel Borkmann Link: https://lore.kernel.org/bpf/20230505-bpf-add-tbid-fib-lookup-v2-1-0a31c22c748c@gmail.com --- include/uapi/linux/bpf.h | 21 ++++++++++++++++++--- 1 file changed, 18 insertions(+), 3 deletions(-) (limited to 'include/uapi/linux') diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h index 9273c654743c..a7b5e91dd768 100644 --- a/include/uapi/linux/bpf.h +++ b/include/uapi/linux/bpf.h @@ -3177,6 +3177,10 @@ union bpf_attr { * **BPF_FIB_LOOKUP_DIRECT** * Do a direct table lookup vs full lookup using FIB * rules. + * **BPF_FIB_LOOKUP_TBID** + * Used with BPF_FIB_LOOKUP_DIRECT. + * Use the routing table ID present in *params*->tbid + * for the fib lookup. * **BPF_FIB_LOOKUP_OUTPUT** * Perform lookup from an egress perspective (default is * ingress). @@ -6831,6 +6835,7 @@ enum { BPF_FIB_LOOKUP_DIRECT = (1U << 0), BPF_FIB_LOOKUP_OUTPUT = (1U << 1), BPF_FIB_LOOKUP_SKIP_NEIGH = (1U << 2), + BPF_FIB_LOOKUP_TBID = (1U << 3), }; enum { @@ -6891,9 +6896,19 @@ struct bpf_fib_lookup { __u32 ipv6_dst[4]; /* in6_addr; network order */ }; - /* output */ - __be16 h_vlan_proto; - __be16 h_vlan_TCI; + union { + struct { + /* output */ + __be16 h_vlan_proto; + __be16 h_vlan_TCI; + }; + /* input: when accompanied with the + * 'BPF_FIB_LOOKUP_DIRECT | BPF_FIB_LOOKUP_TBID` flags, a + * specific routing table to use for the fib lookup. + */ + __u32 tbid; + }; + __u8 smac[6]; /* ETH_ALEN */ __u8 dmac[6]; /* ETH_ALEN */ }; -- cgit