From: Daniel Borkmann <daniel@iogearbox•net>
To: Xin Long <lucien.xin@gmail•com>,
network dev <netdev@vger•kernel.org>,
linux-sctp@vger•kernel.org
Cc: davem@davemloft•net,
Marcelo Ricardo Leitner <marcelo.leitner@gmail•com>,
Vlad Yasevich <vyasevich@gmail•com>
Subject: Re: [PATCH net] sctp: fix the transports round robin issue when init is retransmitted
Date: Thu, 10 Mar 2016 10:48:45 +0100 [thread overview]
Message-ID: <56E142FD.3070105@iogearbox.net> (raw)
In-Reply-To: <8d3cd163c84b30797f1123a7fc8a56f768801a87.1457595117.git.lucien.xin@gmail.com>
On 03/10/2016 08:31 AM, Xin Long wrote:
> prior to this patch, at the beginning if we have two paths in one assoc,
> they may have the same params other than the last_time_heard, it will try
> the paths like this:
>
> 1st cycle
> try trans1 fail.
> then trans2 is selected.(cause it's last_time_heard is after trans1).
>
> 2nd cycle:
> try trans2 fail
> then trans2 is selected.(cause it's last_time_heard is after trans1).
>
> 3rd cycle:
> try trans2 fail
> then trans2 is selected.(cause it's last_time_heard is after trans1).
>
> ....
>
> trans1 will never have change to be selected, which is not what we expect.
> we should keeping round robin all the paths if they are just added at the
> beginning.
>
> So at first every tranport's last_time_heard should be initialized 0, so
> that we ensure they have the same value at the beginning, only by this,
> all the transports could get equal chance to be selected.
>
> Then for sctp_trans_elect_best, it should return the trans_next one when
> *trans == *trans_next, so that we can try next if it fails, but now it
> always return trans. so we can fix it by exchanging these two params when
> we calls sctp_trans_elect_tie().
>
> Fixes: 4c47af4d5eb2 ('net: sctp: rework multihoming retransmission path selection to rfc4960')
> Signed-off-by: Xin Long <lucien.xin@gmail•com>
Seems okay to me. I presume these paths were either all in PF or INACTIVE
state, if not even HBs get through that would actually raise some scores,
so that a good path will be selected again in such case.
Acked-by: Daniel Borkmann <daniel@iogearbox•net>
next prev parent reply other threads:[~2016-03-10 9:48 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-03-10 7:31 [PATCH net] sctp: fix the transports round robin issue when init is retransmitted Xin Long
2016-03-10 9:48 ` Daniel Borkmann [this message]
2016-03-10 15:01 ` Marcelo Ricardo Leitner
2016-03-14 1:53 ` David Miller
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