netdev - Re: [PATCHv4 net-next 16/16] sctp: enable udp tunneling socks

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Date:   Wed, 21 Oct 2020 12:16:53 +0800
From:   Xin Long <lucien.xin@...il.com>
To:     Marcelo Ricardo Leitner <marcelo.leitner@...il.com>
Cc:     Michael Tuexen <tuexen@...muenster.de>,
        network dev <netdev@...r.kernel.org>,
        linux-sctp@...r.kernel.org, Neil Horman <nhorman@...driver.com>,
        davem <davem@...emloft.net>, Guillaume Nault <gnault@...hat.com>,
        Paolo Abeni <pabeni@...hat.com>,
        Willem de Bruijn <willemdebruijn.kernel@...il.com>
Subject: Re: [PATCHv4 net-next 16/16] sctp: enable udp tunneling socks

On Wed, Oct 21, 2020 at 5:23 AM Marcelo Ricardo Leitner
<marcelo.leitner@...il.com> wrote:
>
> On Tue, Oct 20, 2020 at 11:15:26PM +0200, Michael Tuexen wrote:
> > > On 20. Oct 2020, at 23:11, Marcelo Ricardo Leitner <marcelo.leitner@...il.com> wrote:
> > >
> > > On Tue, Oct 20, 2020 at 05:12:06PM +0800, Xin Long wrote:
> > >> On Tue, Oct 20, 2020 at 6:15 AM Marcelo Ricardo Leitner
> > >> <marcelo.leitner@...il.com> wrote:
> > >>>
> > >>> On Mon, Oct 19, 2020 at 08:25:33PM +0800, Xin Long wrote:
> > >>>> --- a/Documentation/networking/ip-sysctl.rst
> > >>>> +++ b/Documentation/networking/ip-sysctl.rst
> > >>>> @@ -2640,6 +2640,12 @@ addr_scope_policy - INTEGER
> > >>>>
> > >>>>      Default: 1
> > >>>>
> > >>>> +udp_port - INTEGER
> > >>>
> > >>> Need to be more verbose here, and also mention the RFC.
> > >>>
> > >>>> +     The listening port for the local UDP tunneling sock.
> > >>>        , shared by all applications in the same net namespace.
> > >>>> +     UDP encapsulation will be disabled when it's set to 0.
> > >>>
> > >>>        "Note, however, that setting just this is not enough to actually
> > >>>        use it. ..."
> > >> When it's a client, yes,  but when it's a server, the encap_port can
> > >> be got from the incoming packet.
> > >>
> > >>>
> > >>>> +
> > >>>> +     Default: 9899
> > >>>> +
> > >>>> encap_port - INTEGER
> > >>>>      The default remote UDP encapsalution port.
> > >>>>      When UDP tunneling is enabled, this global value is used to set
> > >>>
> > >>> When is it enabled, which conditions are needed? Maybe it can be
> > >>> explained only in the one above.
> > >> Thanks!
> > >> pls check if this one will be better:
> > >
> > > It is. Verbose enough now, thx.
> > > (one other comment below)
> > >
> > >>
> > >> udp_port - INTEGER
> > >>
> > >> The listening port for the local UDP tunneling sock.
> > >>
> > >> This UDP sock is used for processing the incoming UDP-encapsulated
> > >> SCTP packets (from RFC6951), and shared by all applications in the
> > >> same net namespace. This UDP sock will be closed when the value is
> > >> set to 0.
> > >>
> > >> The value will also be used to set the src port of the UDP header
> > >> for the outgoing UDP-encapsulated SCTP packets. For the dest port,
> > >> please refer to 'encap_port' below.
> > >>
> > >> Default: 9899
> > >
> > > I'm now wondering if this is the right default. I mean, it is the
> > > standard port for it, yes, but at the same time, it means loading SCTP
> > > module will steal/use that UDP port on all net namespaces and can lead
> > > to conflicts with other apps. A more conservative approach here is to
> > > document the standard port, but set the default to 0 and require the
> > > user to set it in if it is expected to be used.
> > >
> > > Did FreeBSD enable it by default too?
> > No. The default is 0, which means that the encapsulation is turned off.
> > Setting this sysctl variable to a non-zero value enables the UDP tunneling
> > with the given port.
>
> Thanks Michael.
> Xin, then we should change this default value (and update the
> documentation above accordingly, to still have the standard port #
> readily available in there).
OK, I misunderstood the RFC.

I will remove the call to sctp_udp_sock_start/stop() from
sctp_ctrlsock_init/exit(), and set the udp_port as 0 by default.

Thanks.