netdev - Re: send/sendmsg ENOMEM errors WAS(Re: [PATCH net 6/6] sctp: not return ENOMEM err back in sctp_packet

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Message-ID: <7aa1de3e-19c4-91bd-c0d6-a61f32fa6876@mojatatu.com>
Date:   Tue, 25 Oct 2016 07:04:02 -0400
From:   Jamal Hadi Salim <jhs@...atatu.com>
To:     Marcelo Ricardo Leitner <marcelo.leitner@...il.com>
Cc:     Xin Long <lucien.xin@...il.com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        Vlad Yasevich <vyasevic@...hat.com>,
        Daniel Borkmann <daniel@...earbox.net>,
        David Miller <davem@...emloft.net>,
        "linux-sctp@...r.kernel.org" <linux-sctp@...r.kernel.org>,
        Michael Tuexen <Michael.Tuexen@...chi.franken.de>,
        Eric Dumazet <edumazet@...gle.com>,
        Brenda Butler <bjb@...atatu.com>, gabor@...atatu.com
Subject: Re: send/sendmsg ENOMEM errors WAS(Re: [PATCH net 6/6] sctp: not
 return ENOMEM err back in sctp_packet_transmit

On 16-10-25 06:34 AM, Marcelo Ricardo Leitner wrote:
> On Tue, Oct 25, 2016 at 05:05:41PM +0800, Xin Long wrote:
>>>> in case [1], user can't see the ENOMEM, ENOMEM is more like

>
> Thing is, it may lead to duplicate messages in Application layer, as the
> msg that was errored out may have been actually queued and later
> retransmitted.
>
> That's why I said the recovery steps from this depends on the
> application on top of SCTP, if it can handle such duplicate messages or
> not.

Yes, I was worried about duplicate messages.
Which is a bug on SCTP implementation on Linux, unfortunately. IOW,
transport should take care of duplicates - not the app.
i.e any app change is a workaround which will be  unnecessary in newer
kernels.

cheers,
jamal