netdev - Re: [PATCH bpf v6 04/12] bpf: sockmap, handle fin correctly

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Message-ID: <87leiyguu3.fsf@cloudflare.com>
Date:   Tue, 11 Apr 2023 20:02:53 +0200
From:   Jakub Sitnicki <jakub@...udflare.com>
To:     John Fastabend <john.fastabend@...il.com>
Cc:     daniel@...earbox.net, lmb@...valent.com, edumazet@...gle.com,
        bpf@...r.kernel.org, netdev@...r.kernel.org, ast@...nel.org,
        andrii@...nel.org, will@...valent.com
Subject: Re: [PATCH bpf v6 04/12] bpf: sockmap, handle fin correctly

On Fri, Apr 07, 2023 at 10:16 AM -07, John Fastabend wrote:
> The sockmap code is returning EAGAIN after a FIN packet is received and no
> more data is on the receive queue. Correct behavior is to return 0 to the
> user and the user can then close the socket. The EAGAIN causes many apps
> to retry which masks the problem. Eventually the socket is evicted from
> the sockmap because its released from sockmap sock free handling. The
> issue creates a delay and can cause some errors on application side.
>
> To fix this check on sk_msg_recvmsg side if length is zero and FIN flag
> is set then set return to zero. A selftest will be added to check this
> condition.
>
> Fixes: 04919bed948dc ("tcp: Introduce tcp_read_skb()")
> Tested-by: William Findlay <will@...valent.com>
> Signed-off-by: John Fastabend <john.fastabend@...il.com>
> ---

Reviewed-by: Jakub Sitnicki <jakub@...udflare.com>