netdev - Re: [PATCHv2 net] sctp: update frag_point when stream

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Date:   Fri, 30 Nov 2018 13:13:47 -0800 (PST)
From:   David Miller <davem@...emloft.net>
To:     lucien.xin@...il.com
Cc:     netdev@...r.kernel.org, linux-sctp@...r.kernel.org,
        marcelo.leitner@...il.com, nhorman@...driver.com,
        jakub.audykowicz@...il.com
Subject: Re: [PATCHv2 net] sctp: update frag_point when stream_interleave
 is set

From: Xin Long <lucien.xin@...il.com>
Date: Tue, 27 Nov 2018 19:11:50 +0800

> sctp_assoc_update_frag_point() should be called whenever asoc->pathmtu
> changes, but we missed one place in sctp_association_init(). It would
> cause frag_point is zero when sending data.
> 
> As says in Jakub's reproducer, if sp->pathmtu is set by socketopt, the
> new asoc->pathmtu inherits it in sctp_association_init(). Later when
> transports are added and their pmtu >= asoc->pathmtu, it will never
> call sctp_assoc_update_frag_point() to set frag_point.
> 
> This patch is to fix it by updating frag_point after asoc->pathmtu is
> set as sp->pathmtu in sctp_association_init(). Note that it moved them
> after sctp_stream_init(), as stream->si needs to be set first.
> 
> Frag_point's calculation is also related with datachunk's type, so it
> needs to update frag_point when stream->si may be changed in
> sctp_process_init().
> 
> v1->v2:
>   - call sctp_assoc_update_frag_point() separately in sctp_process_init
>     and sctp_association_init, per Marcelo's suggestion.
> 
> Fixes: 2f5e3c9df693 ("sctp: introduce sctp_assoc_update_frag_point")
> Reported-by: Jakub Audykowicz <jakub.audykowicz@...il.com>
> Signed-off-by: Xin Long <lucien.xin@...il.com>

Applied and queued up for -stable back to v4.18