On Thu, Jan 4, 2018 at 6:59 AM, Marcelo Ricardo Leitner
<marcelo.leitner@xxxxxxxxx> wrote:
> Currently, if PMTU discovery is disabled on a given transport, but the
> configured value is higher than the actual PMTU, it is likely that we
> will get some icmp Frag Needed. The issue is, if PMTU discovery is
> disabled, we won't update the information and will issue a
> retransmission immediately, which may very well trigger another ICMP,
> and another retransmission, leading to a loop.
>
> The fix is to simply not trigger immediate retransmissions if PMTU
> discovery is disabled on the given transport.
>
> Signed-off-by: Marcelo Ricardo Leitner <marcelo.leitner@xxxxxxxxx>
> ---
> net/sctp/input.c | 17 +++++++++++------
> 1 file changed, 11 insertions(+), 6 deletions(-)
>
> diff --git a/net/sctp/input.c b/net/sctp/input.c
> index 621b5ca3fd1c17c3d7ef7bb1c7677ab98cebbe77..4a8e76f4834c90de9398455862423e598b8354a7 100644
> --- a/net/sctp/input.c
> +++ b/net/sctp/input.c
> @@ -399,13 +399,18 @@ void sctp_icmp_frag_needed(struct sock *sk, struct sctp_association *asoc,
> return;
> }
>
> - if (t->param_flags & SPP_PMTUD_ENABLE) {
> - /* Update transports view of the MTU */
> - sctp_transport_update_pmtu(t, pmtu);
> + if (!(t->param_flags & SPP_PMTUD_ENABLE))
> + /* We can't allow retransmitting in such case, as the
> + * retransmission would be sized just as before, and thus we
> + * would get another icmp, and retransmit again.
> + */
> + return;
>
> - /* Update association pmtu. */
> - sctp_assoc_sync_pmtu(asoc);
> - }
> + /* Update transports view of the MTU */
> + sctp_transport_update_pmtu(t, pmtu);
> +
> + /* Update association pmtu. */
> + sctp_assoc_sync_pmtu(asoc);
>
> /* Retransmit with the new pmtu setting.
> * Normally, if PMTU discovery is disabled, an ICMP Fragmentation
> --
> 2.14.3
>
commit 52ccb8e90c0ace233b8b740f2fc5de0dbd706b27
Author: Frank Filz <ffilz@xxxxxxxxxx>
Date: Thu Dec 22 11:36:46 2005 -0800
[SCTP]: Update SCTP_PEER_ADDR_PARAMS socket option to the latest api draft.
It seemed intended to move sctp_retransmit out of 'if (SPP_PMTUD_ENABLE) {}'
on the above commit with some notes:
/* Retransmit with the new pmtu setting.
* Normally, if PMTU discovery is disabled, an ICMP Fragmentation
* Needed will never be sent, but if a message was sent before
* PMTU discovery was disabled that was larger than the PMTU, it
* would not be fragmented, so it must be re-transmitted fragmented.
*/
But this patch is equivalent to move it back into 'if (SPP_PMTUD_ENABLE) {}'.
will there be no regression caused?
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