[Masque] Éric Vyncke's Discuss on draft-ietf-masque-connect-ip-09: (with DISCUSS and COMMENT)

[Éric Vyncke via Datatracker <[e-mail]>]

Éric Vyncke has entered the following ballot position for
draft-ietf-masque-connect-ip-09: Discuss

When responding, please keep the subject line intact and reply to all
email addresses included in the To and CC lines. (Feel free to cut this
introductory paragraph, however.)


Please refer to https://www.ietf.org/about/groups/iesg/statements/handling-ballot-positions/ 
for more information about how to handle DISCUSS and COMMENT positions.


The document, along with other ballot positions, can be found here:
https://datatracker.ietf.org/doc/draft-ietf-masque-connect-ip/



----------------------------------------------------------------------
DISCUSS:
----------------------------------------------------------------------

Thank you for the work put into this document. I *really* find the idea and the
protocol interesting and useful. The text is also easy to read and to
understand (albeit underspecified in some cases -- hence my DISCUSS).

Please find below some blocking DISCUSS points (easy to address by adding some
text), some non-blocking COMMENT points (but replies would be appreciated even
if only for my own education), and some nits.

Special thanks to Chris Wood for the shepherd's detailed write-up including the
WG consensus *but* it lacks the justification of the intended status.

Other thanks to Tim Winters, the Internet directorate reviewer (at my request):
https://datatracker.ietf.org/doc/review-ietf-masque-connect-ip-09-intdir-telechat-winters-2023-04-07/
(and I have read the email exchange, thanks to all)

I hope that this review helps to improve the document,

Regards,

-éric

# DISCUSS (blocking)

As noted in https://www.ietf.org/blog/handling-iesg-ballot-positions/, a
DISCUSS ballot is a request to have a discussion on the following topics:

## Section 8

Several parts of this section are unspecified, see below.

`Note that ICMP messages can originate from a source address different from
that of the IP proxying peer.` is of course obvious, but I think that this case
(ICMP originating from the global Internet to the proxy client) deserves a
section on its own. Notably whether this source must be within the target ?

The source address to be used by the proxy when originating an ICMP should also
be specified, even if just a reference to RFC 6724 for IPv6.

## Section 9.2

In the example where the IP proxy has an IP address in the same prefix as the
legacy client (there is no on-link / off-link state for IPv4 as opposed to
IPv6), the encapsulation behavior of section 7 requires the TTL to be
decremented before entering the tunnel, which is really wrong as it this case
it is not formally a routing to a different prefix and some protocols may
expect TTL=255, which won't be the case.

Request to add some text about this "issue".


----------------------------------------------------------------------
COMMENT:
----------------------------------------------------------------------


# COMMENTS (non blocking)

## Waiting for Last Call PR ?

May I suggest, next time, to wait until a revised I-D is submitted based on the
IETF Last Call before balloting ? E.g., the PR based on the sec-dir review is
not yet merged AFAIK.

## Section 3

`The URI Template MUST NOT contain any non-ASCII unicode characters and MUST
only contain ASCII characters in the range 0x21-0x7E inclusive` the fist part
of the sentence appears as useless as the second part is more restrictive.

## Section 4.1

In `establishes an IP tunnel` should the other side of the tunnel specified ?

## Section 4.6

Should the text also be clear that the proxy should only proxy packets *from*
the target to the client ?

## Section 4.7.1

Should the text specify what are the unused bits of the prefix when the prefix
length is not the address length ? I.e., is 2001:db8:cafe:babe:f00d::/32 a
valid prefix ?

## Section 4.7.3

In the previous sections, IP protocol could also be an IPv6 extension header.
I.e., using "0" as a wildcard value prevents using it to signal Hop-by-hop
extension header. Should 59 be used ? (even if no next header is only for IPv6)

BTW, I was about to ballot DISCUSS on this issue.

The reader (including myself and John Scudder per his ballot) would probably
welcome more explanations to understand why the usual CIDR/prefix notation for
routes is not used. I.e., some routers only use CIDR/prefix FIB entries and one
start-end range could translate in a lot of CIDR/prefix routes in the router
FIB.

## Section 7

Thanks for the text about link-local addresses and link-local multicast. But,
then it raises the question about which IP address to use when replying to a
link-local multicast ? I.e., can a global address be used in the absence of LLA
?

## Section 8

Please also add "hop-limit exceeded" in the non-exhaustive list of errors.

Should ICMP echo requests be mentioned ? (they are *not* error signaling but
are quite useful).

## Section 9.1

In `Such VPN setups can be either full-tunnel or split-tunnel` please define
(or add a reference) to full/split tunnel or simply do not mention those terms
now as they are defined later.

`using a source address in its assigned prefix` while the client has been
assigned a single /32 (i.e., the sentence is correct but could be confusing)

The legends of figures 15 and 16 use different templates ("capsule" in one
case) is it on purpose ?

Should the split-tunnel example have two routes to exclude 192.2.0.42 ?

## Section 12

RFC 5095 is probably not the best RFC about extension header security, there
have been many others notably in V6OPS by Fernando Gont et al.

Should there be an informative reference to RFC 6169 (Security Concerns with IP
Tunneling) ?

# NITS (non blocking / cosmetic)

## Section 4.1

s/via A and/or AAAA records/via A and/or AAAA resource records/ ?