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Date:      Tue, 15 Oct 2024 16:07:17 +0000
From:      bugzilla-noreply@freebsd.org
To:        net@FreeBSD.org
Subject:   [Bug 219918] LibAlias: implement RFC 4787 REQ 1 and 3 (full cone NAT)
Message-ID:  <bug-219918-7501-wr1R0wG4pk@https.bugs.freebsd.org/bugzilla/>
In-Reply-To: <bug-219918-7501@https.bugs.freebsd.org/bugzilla/>
References:  <bug-219918-7501@https.bugs.freebsd.org/bugzilla/>

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https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=3D219918

--- Comment #12 from Damjan Jovanovic <damjan.jov@gmail.com> ---
(In reply to Kurt Jaeger from comment #10)

EIM =3D endpoint-independent mapping, same abbreviation that is also used i=
n RFC
6887 (if not more RFCs). They also used EDM =3D endpoint-dependent mapping
(address and port-dependent mapping in RFC 4787).

There are several problems with "full cone":
- The RFC that invented the term, RFC 3489, is now obsolete, and the new
version of it, RFC 5389, no longer uses that term.
- All the NAT types described in RFC 3489 confused 2 different concepts:
mapping (how packets change going out) and filtering (what can come back in=
).
See the table below for a comparison of RFC 3489 and RFC 4787 terms under
different settings.
- When EIM and PKT_ALIAS_DENY_INCOMING are both set, it is no longer a "full
cone" NAT, it would be a "port restricted cone" NAT instead.

           |               |                                               =
 |
PKT_ALIAS_ | PKT_ALIAS_    |                                               =
 |
EIM        | DENY_INCOMING | NAT type, by RFC                              =
 |
Comment
-----------+---------------+-----------------------------------------------=
-+-----------
     unset |        unset  | RFC 4787: address and port-dependent mapping  =
 |
These are
           |               |           address and port-dependent filtering=
 |
the only
           |               | RFC 3489: "symmetric" NAT                     =
 |
ways that
-----------+---------------+-----------------------------------------------=
-|
libalias
     unset |          set  | RFC 4787: address and port-dependent mapping  =
 |
works
           |               |           address and port-dependent filtering=
 |
at
           |               | RFC 3489: "symmetric" NAT                     =
 |
present.
-----------+---------------+-----------------------------------------------=
-+-----------
       set |        unset  | RFC 4787: endpoint-independent mapping        =
 |
My patch
           |               |           endpoint-independent filtering      =
 |
adds
           |               | RFC 3489: "full cone" NAT                     =
 |
these
-----------+---------------+-----------------------------------------------=
-|
bottom
       set |          set  | RFC 4787: endpoint-independent mapping        =
 | 2
rows
           |               |           address and port-dependent filtering=
 |
as
           |               | RFC 3489: "port restricted cone" NAT          =
 |
options.

--=20
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