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Message-ID: <20201106084634.GA3556@localhost.localdomain>
Date: Fri, 6 Nov 2020 05:46:34 -0300
From: Marcelo Ricardo Leitner <marcelo.leitner@...il.com>
To: Petr Malat <oss@...at.biz>
Cc: linux-sctp@...r.kernel.org, Vlad Yasevich <vyasevich@...il.com>,
Neil Horman <nhorman@...driver.com>,
"David S. Miller" <davem@...emloft.net>,
Jakub Kicinski <kuba@...nel.org>, netdev@...r.kernel.org,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH] sctp: Fix sending when PMTU is less than
SCTP_DEFAULT_MINSEGMENT
On Thu, Nov 05, 2020 at 11:39:47AM +0100, Petr Malat wrote:
> Function sctp_dst_mtu() never returns lower MTU than
> SCTP_TRUNC4(SCTP_DEFAULT_MINSEGMENT) even when the actual MTU is less,
> in which case we rely on the IP fragmentation and must enable it.
This should be being handled at sctp_packet_will_fit():
psize = packet->size;
if (packet->transport->asoc)
pmtu = packet->transport->asoc->pathmtu;
else
pmtu = packet->transport->pathmtu;
/* Decide if we need to fragment or resubmit later. */
if (psize + chunk_len > pmtu) {
/* It's OK to fragment at IP level if any one of the following
* is true:
* 1. The packet is empty (meaning this chunk is greater
* the MTU)
* 2. The packet doesn't have any data in it yet and data
* requires authentication.
*/
if (sctp_packet_empty(packet) ||
(!packet->has_data && chunk->auth)) {
/* We no longer do re-fragmentation.
* Just fragment at the IP layer, if we
* actually hit this condition
*/
packet->ipfragok = 1;
goto out;
}
Why the above doesn't handle it already?
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