Re: [PATCH 3/3] netfilter: conntrack: unify established states for SCTP paths

[Pablo Neira Ayuso <pablo@netfilter.org>]

On Tue, Jan 17, 2023 at 12:54:40PM +0100, Pablo Neira Ayuso wrote:
> On Mon, Jan 16, 2023 at 10:35:56AM +0100, Sriram Yagnaraman wrote:
> > An SCTP endpoint can start an association through a path and tear it
> > down over another one. That means the initial path will not see the
> > shutdown sequence, and the conntrack entry will remain in ESTABLISHED
> > state for 5 days.
> > 
> > By merging the HEARTBEAT_ACKED and ESTABLISHED states into one
> > ESTABLISHED state, there remains no difference between a primary or
> > secondary path. The timeout for the merged ESTABLISHED state is set to
> > 210 seconds (hb_interval * max_path_retrans + rto_max). So, even if a
> > path doesn't see the shutdown sequence, it will expire in a reasonable
> > amount of time.
> > 
> > Signed-off-by: Sriram Yagnaraman <sriram.yagnaraman@est.tech>
> > ---
> >  .../uapi/linux/netfilter/nf_conntrack_sctp.h  |  4 +-
> >  .../linux/netfilter/nfnetlink_cttimeout.h     |  4 +-
> >  net/netfilter/nf_conntrack_proto_sctp.c       | 90 ++++++++-----------
> >  net/netfilter/nf_conntrack_standalone.c       | 16 ----
> >  4 files changed, 42 insertions(+), 72 deletions(-)
> > 
> > diff --git a/include/uapi/linux/netfilter/nf_conntrack_sctp.h b/include/uapi/linux/netfilter/nf_conntrack_sctp.h
> > index c742469afe21..150fc3c056ea 100644
> > --- a/include/uapi/linux/netfilter/nf_conntrack_sctp.h
> > +++ b/include/uapi/linux/netfilter/nf_conntrack_sctp.h
> > @@ -15,8 +15,8 @@ enum sctp_conntrack {
> >  	SCTP_CONNTRACK_SHUTDOWN_RECD,
> >  	SCTP_CONNTRACK_SHUTDOWN_ACK_SENT,
> >  	SCTP_CONNTRACK_HEARTBEAT_SENT,
> > -	SCTP_CONNTRACK_HEARTBEAT_ACKED,
> > -	SCTP_CONNTRACK_DATA_SENT,
> > +	SCTP_CONNTRACK_HEARTBEAT_ACKED,	/* no longer used */
> > +	SCTP_CONNTRACK_DATA_SENT,	/* no longer used */
> 
> _DATA_SENT was added in the previous development cycle, to my
> knowledged it has been present in 6.1-rc only. Then I think you can

Actually, I mean 6.2-rc releases.

> post a patch to revert this explaining why there is no need for
> _DATA_SENT anymore. You can revert it before this patch (with my
> suggestion, your series will contain with 4 patches).
> 
> One question of mine: Did you extract the new established timeout from
> RFC, where this formula came from?
> 
> 210 seconds = hb_interval * max_path_retrans + rto_max
> 
> And thanks, if this works for you, I prefer this incremental approach
> by improving the existing SCTP tracker.