netdev - Re: [PATCHv2 bpf 1/2] bpf: Support sk lookup in netns with id 0

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Date:   Fri, 30 Nov 2018 10:04:21 -0800
From:   Joe Stringer <joe@...d.net.nz>
To:     Joe Stringer <joe@...d.net.nz>
Cc:     daniel@...earbox.net, ast@...nel.org,
        netdev <netdev@...r.kernel.org>, David Ahern <dsahern@...il.com>,
        Nicolas Dichtel <nicolas.dichtel@...nd.com>
Subject: Re: [PATCHv2 bpf 1/2] bpf: Support sk lookup in netns with id 0

On Thu, 29 Nov 2018 at 16:30, Joe Stringer <joe@...d.net.nz> wrote:
>
> David Ahern and Nicolas Dichtel report that the handling of the netns id
> 0 is incorrect for the BPF socket lookup helpers: rather than finding
> the netns with id 0, it is resolving to the current netns. This renders
> the netns_id 0 inaccessible.
>
> To fix this, adjust the API for the netns to treat all negative s32
> values as a lookup in the current netns, while any values with a
> positive value in the signed 32-bit integer space would result in a
> lookup for a socket in the netns corresponding to that id. As before, if
> the netns with that ID does not exist, no socket will be found.
> Furthermore, if any bits are set in the upper 32-bits, then no socket
> will be found.

This last sentence is a little misleading, it only applies if the
highest bit in the lower 32 bits is 0.