From: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
To: Petr Malat <oss@malat.biz>
Cc: linux-sctp@vger.kernel.org, vyasevich@gmail.com,
nhorman@tuxdriver.com, davem@davemloft.net, kuba@kernel.org,
netdev@vger.kernel.org
Subject: Re: [PATCH] sctp: Honour SCTP_PARTIAL_DELIVERY_POINT even under memory pressure
Date: Thu, 03 Sep 2020 17:18:47 +0000 [thread overview]
Message-ID: <20200903171847.GD2444@localhost.localdomain> (raw)
In-Reply-To: <20200903112147.GA17627@bordel.klfree.net>
Hi!
On Thu, Sep 03, 2020 at 01:21:48PM +0200, Petr Malat wrote:
> Hi!
> On Wed, Sep 02, 2020 at 11:58:35AM -0300, Marcelo Ricardo Leitner wrote:
> > On Tue, Sep 01, 2020 at 11:00:07AM +0200, Petr Malat wrote:
> > > Command SCTP_CMD_PART_DELIVER issued under memory pressure calls
> > > sctp_ulpq_partial_delivery(), which tries to fetch and partially deliver
> > > the first message it finds without checking if the message is longer than
> > > SCTP_PARTIAL_DELIVERY_POINT. According to the RFC 6458 paragraph 8.1.21.
> > > such a behavior is invalid. Fix it by returning the first message only if
> > > its part currently available is longer than SCTP_PARTIAL_DELIVERY_POINT.
> >
> > Okay but AFAICT this patch then violates the basic idea behind partial
> > delivery. It will cause such small message to just not be delivered
> > anymore, and keep using the receive buffer which it is trying to free
> > some bits at this moment.
> By default the pd_point is set to 0, so there will not be a change in the
> behavior, but if the user changes it to some other value, it should be
> respected by the stack - for example when the largest message the user
> exchanges is 1kB and the user sets it to 1kB, his application is not
> prepared to handle fragmented messages at all and it's not a good idea to
> pass such a message to the app.
Then, if it doesn't support fragmented messages at all, the app just
shouldn't be setting pd_point at all. :-) Anyhow, I see how the patch
works now.
The fix is also needed on sctp_intl_retrieve_first() and
sctp_intl_retrieve_first_uo(). Same issue is in there, but for stream
interleaving.
Thanks.
prev parent reply other threads:[~2020-09-03 17:18 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-09-01 9:00 [PATCH] sctp: Honour SCTP_PARTIAL_DELIVERY_POINT even under memory pressure Petr Malat
2020-09-02 14:58 ` Marcelo Ricardo Leitner
2020-09-03 11:21 ` Petr Malat
2020-09-03 17:18 ` Marcelo Ricardo Leitner [this message]
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