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Date:      Thu, 9 Jul 2020 12:44:25 -0700
From:      Doug Hardie <bc979@lafn.org>
To:        Mark Johnston <markj@freebsd.org>
Cc:        freebsd-net@freebsd.org, tuexen@freebsd.org
Subject:   Re: making SCTP loadable and removing it from GENERIC
Message-ID:  <63F4446F-DECF-4DE8-99CA-EC8755A5D4A1@mail.sermon-archive.info>
In-Reply-To: <20200709151300.GC8947@raichu>
References:  <20200709151300.GC8947@raichu>

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> On 9 July 2020, at 08:13, Mark Johnston <markj@freebsd.org> wrote:
>=20
> Hi,
>=20
> I spent some time working on making it possible to load the SCTP stack
> as a kernel module, the same as we do today with IPSec.  There is one
> patch remaining to be committed before that can be done in head.  One
> caveat is that the module can't be unloaded, as some work is needed to
> make this safe.  However, this obviously isn't a regression.
>=20
> The work is based on the observations that:
> 1) the in-kernel SCTP stack is not widely used (I know that the same
>   code is used in some userland applications), and
> 2) the SCTP stack is quite large, most FreeBSD kernel developers are
>   unfamiliar with it, and bugs in it can easily lead to security =
holes.
>=20
> Michael has done a lot of work to fix issues in the SCTP code,
> particularly those found by syzkaller, but given that in-kernel SCTP =
has
> few users (almost certainly fewer than IPSec), it seems reasonable to
> require users to opt in to having an SCTP stack with a simple "kldload
> sctp".  Thus, once the last patch is committed I would like to propose
> removing "options SCTP" from GENERIC kernel configs in head, replacing
> it with "options SCTP_SUPPORT" to enable sctp.ko to be loaded.
>=20
> I am wondering if anyone has any objections to or concerns about this
> proposal.  Any feedback is appreciated.

I have a number of systems using SCTP.  It is a key part of a =
distributed application.  As a user of SCTP, I have a slight objection =
to removing it from the kernel.  It would require me to remember when =
setting up a new system to enable that.  I am not likely to remember.  =
What is going to happen if you run an application that uses SCTP and the =
module is not loaded?  What will remind me how to fix the issue?  I am =
not likely to remember about this 6 months from now.

-- Doug=



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