FWIW, this document includes text that somewhat defeats the previous
recommendations of TCPM regarding RFC5927.
RFC5927 includes specific text indicating that the techniques described
are being documented, but that the TCP standard was NOT being changed to
include those ICMP validation checks.
This document states that:
Many implementations fail to perform validation checks on the
received ICMPv6 error messages, as recommended in Section 5.2 of
[RFC4443] and [RFC5927].
I.e., the second RFC does NOT recommend changes; it documents them. This
document should be VERY carefully reviewed to ensure that it does not
undo the previous TCPM concerns about these techniques.
Joe