[Discuss] Does "fou" decapsulation work?

[worley at alum.mit.edu (Dale R. Worley)]

I've been trying to use "fou" decapsulation, i.e., "ip fou add port
...".  There are a few references on the web that suggest this feature
has been in the kernel for several years, and Fedora 26 has commands to
support it.  But it doesn't seem to actually work when I try it (with
kernel 4.13.16-202.fc26.x86_64) -- UDP packets directed to the
decapsulation port are dropped and cause ICMP "protocol 17 unreachable"
messages to be generated (according to tcpdump).

I was wondering if anyone has used this feature.

(The details of my testcase are in
https://bugzilla.redhat.com/show_bug.cgi?id=1524180 .)

Dale