ARP Address Conflict Detection and dhcpcd arping

[rudolf <netbsd%eq.cz@localhost>]

Hi,

I have a NetBSD 8.1_STABLE (july 2019) host with a static IP address and 
another machine (Linux) with dhcpcd "arping" configuration for this IP 
address. With the default value of sysctl net.inet.ip.dad_count (=3), I 
see no ARP reply ("ARP, Reply <IP addr> is-at <MAC>") messages from the 
NetBSD host on the arping queries ("ARP, Request who-has <IP addr> tell 
0.0.0.0") and eventually the NetBSD host marks its IP address as 
duplicated (and the "arping" dhcpcd configuration of the second host fails).

This seems contradictory to what I read in "man 4 arp":
``ARP will defend the host's active address when a conflicting message 
is received.''

With "sysctl -w net.inet.ip.dad_count=0", the NetBSD host sends the ARP 
reply and the "arping" configuration of the second host works.

Is this expected behavior?

Thanks,

r.