Alexei Starovoitov
2022-Jan-25 05:09 UTC
[Bridge] [RFC bpf-next 1/2] net: bridge: add unstable br_fdb_find_port_from_ifindex helper
On Mon, Jan 24, 2022 at 10:32 AM Nikolay Aleksandrov <nikolay at nvidia.com> wrote:> > > > +int br_fdb_find_port_from_ifindex(struct xdp_md *xdp_ctx, > > + struct bpf_fdb_lookup *opt, > > + u32 opt__sz) > > +{ > > + struct xdp_buff *ctx = (struct xdp_buff *)xdp_ctx; > > + struct net_bridge_port *port; > > + struct net_device *dev; > > + int ret = -ENODEV; > > + > > + BUILD_BUG_ON(sizeof(struct bpf_fdb_lookup) != NF_BPF_FDB_OPTS_SZ); > > + if (!opt || opt__sz != sizeof(struct bpf_fdb_lookup)) > > + return -ENODEV; > > + > > + rcu_read_lock(); > > + > > + dev = dev_get_by_index_rcu(dev_net(ctx->rxq->dev), opt->ifindex); > > + if (!dev) > > + goto out;imo that is way too much wrapping for an unstable helper. The dev lookup is not cheap. With all the extra checks the XDP acceleration gets reduced. I think it would be better to use kprobe/fentry on bridge functions that operate on fdb and replicate necessary data into bpf map. Then xdp prog would do a single cheap lookup from that map to figure out 'port'.
Lorenzo Bianconi
2022-Jan-26 11:09 UTC
[Bridge] [RFC bpf-next 1/2] net: bridge: add unstable br_fdb_find_port_from_ifindex helper
> On Mon, Jan 24, 2022 at 10:32 AM Nikolay Aleksandrov <nikolay at nvidia.com> wrote: > > > > > > +int br_fdb_find_port_from_ifindex(struct xdp_md *xdp_ctx, > > > + struct bpf_fdb_lookup *opt, > > > + u32 opt__sz) > > > +{ > > > + struct xdp_buff *ctx = (struct xdp_buff *)xdp_ctx; > > > + struct net_bridge_port *port; > > > + struct net_device *dev; > > > + int ret = -ENODEV; > > > + > > > + BUILD_BUG_ON(sizeof(struct bpf_fdb_lookup) != NF_BPF_FDB_OPTS_SZ); > > > + if (!opt || opt__sz != sizeof(struct bpf_fdb_lookup)) > > > + return -ENODEV; > > > + > > > + rcu_read_lock(); > > > + > > > + dev = dev_get_by_index_rcu(dev_net(ctx->rxq->dev), opt->ifindex); > > > + if (!dev) > > > + goto out; > > imo that is way too much wrapping for an unstable helper. > The dev lookup is not cheap. > > With all the extra checks the XDP acceleration gets reduced. > I think it would be better to use kprobe/fentry on bridge > functions that operate on fdb and replicate necessary > data into bpf map. > Then xdp prog would do a single cheap lookup from that map > to figure out 'port'.ack, right. This is a very interesting approach. I will investigate it. Thanks. Regards, Lorenzo -------------- next part -------------- A non-text attachment was scrubbed... Name: signature.asc Type: application/pgp-signature Size: 228 bytes Desc: not available URL: <http://lists.linuxfoundation.org/pipermail/bridge/attachments/20220126/5c6ec898/attachment-0001.sig>