netdev - Re: [PATCH net-next] sock: reset sk_err for ICMP packets read from error queue

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Date:   Wed, 30 Nov 2016 21:49:38 +0100
From:   Maciej Żenczykowski <zenczykowski@...il.com>
To:     Soheil Hassas Yeganeh <soheil.kdev@...il.com>
Cc:     David Miller <davem@...emloft.net>,
        Linux NetDev <netdev@...r.kernel.org>,
        Eric Dumazet <edumazet@...gle.com>,
        Willem de Bruijn <willemb@...gle.com>,
        Hannes Frederic Sowa <hannes@...essinduktion.org>,
        Soheil Hassas Yeganeh <soheil@...gle.com>
Subject: Re: [PATCH net-next] sock: reset sk_err for ICMP packets read from
 error queue

On Wed, Nov 30, 2016 at 8:01 PM, Soheil Hassas Yeganeh
<soheil.kdev@...il.com> wrote:
> From: Soheil Hassas Yeganeh <soheil@...gle.com>
>
> Only when ICMP packets are enqueued onto the error queue,
> sk_err is also set. Before f5f99309fa74 (sock: do not set sk_err
> in sock_dequeue_err_skb), a subsequent error queue read
> would set sk_err to the next error on the queue, or 0 if empty.
> As no error types other than ICMP set this field, sk_err should
> not be modified upon dequeuing them.
>
> Only for ICMP errors, reset the (racy) sk_err. Some applications,
> like traceroute, rely on it and go into a futile busy POLLERR
> loop otherwise.
>
> In principle, sk_err has to be set while an ICMP error is queued.
> Testing is_icmp_err_skb(skb_next) approximates this without
> requiring a full queue walk. Applications that receive both ICMP
> and other errors cannot rely on this legacy behavior, as other
> errors do not set sk_err in the first place.
>
> Fixes: f5f99309fa74 (sock: do not set sk_err in sock_dequeue_err_skb)
> Signed-off-by: Soheil Hassas Yeganeh <soheil@...gle.com>
> Signed-off-by: Willem de Bruijn <willemb@...gle.com>

Acked-by: Maciej Żenczykowski <maze@...gle.com>