dhcpcd-discuss

On 26/03/2019 20:10, Marcin Cieslak wrote:
> (Reviving old thread for the archives)
>
> On Thu, 15 Jun 2017, RJ Ascani wrote:
>
> > I'm running into an issue whereby dhcpcd declines a valid IP address from the dhcp server because of a well timed ARP probe from our Cisco switch with a source IP of INADDR_ANY. Our Cisco switch has IP Device Tracking<http://www.cisco.com/c/en/us/support/docs/ip/address-resolution-protocol-arp/118630-technote-ipdt-00.html> enabled, which is sending ARP probes with a SIP of 0.0.0.0 to all devices every 30 seconds. In the below log, you can see that after dhcpcd gets the offer and starts probing, it encounters a conflict with hardware address ac:7e:8a:18:ef:90 (the Cisco switch).
>
> > Jun 15 15:32:52 eth0: hardware address ac:7e:8a:18:ef:90 claims 172.18.1.127
>
> We have observed dhcpcd (6.11.5-1rpt7 for Raspberry PI) reporting ARP conflicts
> when the Cisco IP Device Tracking is used even with a fully static dhcpcd configuration.
>
>  From a little sniffing we have done it seem that although Cisco IP Device Tracking
> ARP probes are being sent with the source IP of 0.0.0.0, they are sent via Ethernet
> unicast to our device's MAC address and not broadcast, so maybe we can ignore them this
> way?
>
> Neither static ifconfig on Linux nor static IP configuration on FreeBSD generates
> false positive ARP warnings in this case, maybe dhcpcd is a bit overzealous here?

This should now be resolved with these changes:
https://roy.marples.name/git/dhcpcd.git/commit/?id=1e78fa81dc3e06ffac539d051636c45d61394748
https://roy.marples.name/git/dhcpcd.git/commit/?id=f6c81bc59d932b558543c941ec6da3a58939e53f
https://roy.marples.name/git/dhcpcd.git/commit/?id=1232de73e3f7ec11d1c2c3c644d8f044d1613645

Roy