I am running Chilli 1.1.0 on OpenWRT Kamikaze r13624 at present.
It works fine for Windows users but not Macintosh.  Mac users cannot
even get the login page.  If I test from Mac it shows DUP packets
on every ping.  I connected laptops via wired LAN ports to eliminate
WiFi issues and the problem persists.

When I run tcpdump on WRT I can clearly see the dups:

23:27:15.723230 IP 10.69.2.1 > 10.69.2.2: ICMP echo reply, id 512, seq 1536, length 40
23:27:15.820406 IP 10.69.2.2 > 10.69.2.1: ICMP echo request, id 512, seq 1536, length 40
23:27:15.821217 IP 10.69.2.1 > 10.69.2.2: ICMP echo reply, id 512, seq 1536, length 40

Perhaps Windows is forgiving of these duplicates & Mac is not?
How can I separate where these dups are introduced?
My prime suspects would be kmod-tun or chilli, others?