Re: [tcpm] Paul Wouters's Discuss on draft-ietf-tcpm-yang-tcp-07: (with DISCUSS and COMMENT)

Reminder to clear!

On Mon, Sep 5, 2022 at 12:53 PM Paul Wouters <paul.wouters=
40aiven.io@dmarc.ietf.org> wrote:

> Thanks for the feedback. It addresses my discuss points. Thanks for
> providing the information. I will clear my discuss shortly
>
> Sent using a virtual keyboard on a phone
>
> > On Sep 5, 2022, at 04:52, Scharf, Michael <
> Michael.Scharf@hs-esslingen.de> wrote:
> >
> > Hi Paul,
> >
> > Sorry, apparently I have not received an e-mail regarding this DISCUSS.
> >
> > I have copied the text from datatracker and replied inline.
> >
> > The complete diff for version -08 can be found at:
> https://www.ietf.org/rfcdiff?url2=draft-ietf-tcpm-yang-tcp-08
> >
> >> Discuss (2022-06-28 for -07)
> >> [ballot text incomplete as cloudflare triggers a weird refusal if I
> include a certain sentence, see Cloudflare Ray ID: 722aa6477e01a1db]
> >>
> >> Thanks for the -07 changes in response to the various area reviews!
> >>
> >> I still have two small discuss questions left which might be caused by
> a limited
> >> understanding of the underlying yang model inclusions.
> >>
> >>
> >>             1. For an application willing to accept both IPv4 and
> >>               IPv6 datagrams, the value of this object must be
> >>                ''h (a zero-length octet-string), with the value
> >>                of the corresponding 'type' object being
> >>                unknown (0).
> >>
> >>             2. For an application willing to accept only IPv4 or
> >>                IPv6 datagrams, the value of this object must be
> >>                '0.0.0.0' or '::' respectively, with
> >>                'type' representing the appropriate address type.
> >>
> >> #D1
> >>
> >> To me, it seems very counter-intuitive that '' means (0.0.0.0 or ::).
> For
> >> LISTEN, I find it concerning because it means that '' as a default
> means to
> >> listen to any IP, rather than the more secure default of '' meaning
> 'none'.
> >
> > This syntax is identical to the TCP MIB. We have not created this
> definition on our own. At least to me it is not obvious why this specific
> detail of the TCP MIB would be broken. Also, I don't understand why "none"
> would be required at all in this context (see below).
> >
> >> Is it possible to have some kind of "None" default? (or is that
> achieved by
> >> omission of this option?
> >
> > As far as I understand, this entry is about the list "tcp-listeners".
> >
> > By definition, a TCP endpoint in state "listen" is willing to accept
> (some) TCP connections. This is the connection acceptor, i.e., typically
> the server side of an application. An application that is not willing to
> accept any connections (e.g., a client) is not in "listen" state and
> therefore not included in this list "tcp-listeners".
> >
> > As this list "tcp-listener" only includes endpoints that indeed listen
> on at least one IP address, I am not aware of a case in which a value
> "none" would be used.
> >
> > In -08, we have slightly changed this description to address some other
> comments and to avoid "MIB speak", but we have not added a way to encode
> "none".
> >
> > Please get back to us if we should have missed something.
> >
> >> #D2
> >>
> >> Is it intended that this cannot be specified using names
> >
> > Again, I assume that this refers to the list "tcp-listeners".
> >
> > This is a read-only list, i.e., a TCP listener will never be created by
> configuring the YANG model. Instead, an application will use the usual ways
> to create a TCP endpoint (e.g., the socket API, which may understand names
> depending on the used socket calls).
> >
> > Once a TCP listener exists, the TCP stack must know the port number
> internally, and it internally operates using the port number. So, the port
> number can always be listed.
> >
> > It may be possible to list names for port numbers if the mapping is
> known, but it is not exactly clear if all TCP stacks are able to do so.
> >
> > The TCP MIB just uses the port number in the corresponding list. As a
> result, in version -08 we just kept this as in the TCP MIB.
> >
> > If there is really a strong reason to model more than the TCP MIB,
> please let us know.
> >
> >> Comment (2022-06-28 for -07)
> >> #C1
> >>
> >> It is unclear to me if '0.0.0.0' denotes the type inet:ip-address or
> >> the type string with text value "0.0.0.0". I also worry that if this is
> >> represented in C with a struct with union, that than it is unclear what
> >> a zero'ed out struct is set to? The string or the v4 ANY or the v6 ANY ?
> >> (I personally like enums to start from value 1 for that reason)
> >>
> >> #C2
> >>
> >> How is this option set when fully disabled (eg not listening on
> anything, only
> >> willing to make an outgoing TCP connection). Is it by being omitted?
> >
> > Yes. A connection initiator (i.e., a client making only outgoing
> connections) is not a tcp listener and thus just omitted. See also the
> previous comments.
> >
> >> NITS:
> >>
> >> listner -> listener
> >>
> >> for TCP connection that -> for a TCP connection that
> >
> > Thanks, this has been fixed in -08.
> >
> > Michael
>
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