netdev - Re: [PATCH bpf-next v4 10/12] net: Generate reuseport group ID on group creation

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Message-ID: <20200123170158.a4c3awxgyr3n7huf@kafai-mbp.dhcp.thefacebook.com>
Date:   Thu, 23 Jan 2020 17:02:02 +0000
From:   Martin Lau <kafai@...com>
To:     Jakub Sitnicki <jakub@...udflare.com>
CC:     "bpf@...r.kernel.org" <bpf@...r.kernel.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "kernel-team@...udflare.com" <kernel-team@...udflare.com>,
        John Fastabend <john.fastabend@...il.com>,
        Lorenz Bauer <lmb@...udflare.com>
Subject: Re: [PATCH bpf-next v4 10/12] net: Generate reuseport group ID on
 group creation

On Thu, Jan 23, 2020 at 04:55:32PM +0100, Jakub Sitnicki wrote:
> Commit 736b46027eb4 ("net: Add ID (if needed) to sock_reuseport and expose
> reuseport_lock") has introduced lazy generation of reuseport group IDs that
> survive group resize.
> 
> By comparing the identifier we check if BPF reuseport program is not trying
> to select a socket from a BPF map that belongs to a different reuseport
> group than the one the packet is for.
> 
> Because SOCKARRAY used to be the only BPF map type that can be used with
> reuseport BPF, it was possible to delay the generation of reuseport group
> ID until a socket from the group was inserted into BPF map for the first
> time.
> 
> Now that SOCKMAP can be used with reuseport BPF we have two options, either
> generate the reuseport ID on map update, like SOCKARRAY does, or allocate
> an ID from the start when reuseport group gets created.
> 
> This patch goes the latter approach to keep SOCKMAP free of calls into
> reuseport code. This streamlines the reuseport_id access as its lifetime
> now matches the longevity of reuseport object.
Acked-by: Martin KaFai Lau <kafai@...com>