(in my case it as a switch set to "monitor" mode):
If we see an NS request for the address we are just probing for, for
three times the number of DAD packets we are supposed to send (the
"ip6.dad_count" sysctl variable), assume that these are our own packets
and let DAD succeed.
The code for this was mostly there, commented out. Just needed some fixes.
The "three times" is heuristic of course.
Being here, reset the "dad_ns_tcount" variable on a successful send;
otherwise we get strange interdependencies with user-settable variables
(ever tried to set ip6.dad_count to something >15?).
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