netdev - Re: [PATCH bpf-next v2 4/4] devmap: Exclude XDP broadcast to master device

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Date:   Mon, 5 Jul 2021 14:44:16 +0300
From:   Jussi Maki <joamaki@...il.com>
To:     Jay Vosburgh <jay.vosburgh@...onical.com>
Cc:     bpf <bpf@...r.kernel.org>,
        Network Development <netdev@...r.kernel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andy Gospodarek <andy@...yhouse.net>, vfalico@...il.com,
        Andrii Nakryiko <andrii@...nel.org>,
        Maciej Fijalkowski <maciej.fijalkowski@...el.com>,
        "Karlsson, Magnus" <magnus.karlsson@...el.com>
Subject: Re: [PATCH bpf-next v2 4/4] devmap: Exclude XDP broadcast to master device

On Thu, Jul 1, 2021 at 9:12 PM Jay Vosburgh <jay.vosburgh@...onical.com> wrote:
> >+      if (static_branch_unlikely(&bpf_master_redirect_enabled_key)) {
> >+              struct net_device *master = netdev_master_upper_dev_get_rcu(dev_rx);
> >+
> >+              exclude_ifindex_master = (master && exclude_ingress) ? master->ifindex : 0;
> >+      }
> >+
>
>         Will the above logic do what is intended if the device stacking
> isn't a simple bond -> ethX arrangement?  I.e., bond -> VLAN.?? -> ethX
> or perhaps even bondA -> VLAN.?? -> bondB -> ethX ?

Good point. "bond -> VLAN -> eth" isn't an issue currently as vlan
devices do not support XDP. "bondA -> bondB -> ethX" however would be
supported, so I think it makes sense to change the code to collect all
upper devices and exclude them. I'll try to follow up with an updated
patch for this soon.