dhcpcd-discuss

Hi Matthew

On 01/09/2020 00:47, Matthew Clarkson wrote:
> Again, thanks for the quick responses.

Welcome

> I had a bit of trouble applying those patches, looks like https://roy.marples.name/cgit/dhcpcd.git/commit/?id=b336d43584f8d759acbae668690c6415ca05618f is also required (as one patch uses the dhcp_unlink added in that commit). Before chasing down more commits I have updated to version 9.1.4 and applied the 4 patches you sent.

dhcp_unlink isn't needed for dhcpcd-8 - you can just use unlink from libc in 
it's place.

> I can confirm that after the lease expires, the client sends dhcp discover requests (as broadcasts) roughly every 30 seconds. But there is a new problem. With the lastleaseextend option, the device is not binding to the previous lease's IP. It is bound to a link-local address. In 8.1.9, the interface would be using both a link local address and the address of the previous lease.
>
> In 8.1.9 the output after failing to renew is:
> br0: failed to renew DHCP, rebinding
> br0: DHCP lease expired, extending lease
> br0: pid 0 deleted IP address 192.168.10.20/24
> br0: deleting route to 192.168.10.0/24
> br0: deleting default route via 192.168.10.1
> br0: rebinding lease of 192.168.10.20
> br0: probing for an IPv4LL address
> br0: timed out contacting a DHCP server, using last lease
> br0: leased 192.168.10.20 for 600 seconds
> br0: adding route to 192.168.10.0/24
> br0: adding default route via 192.168.10.1
> br0: soliciting a DHCP lease
> br0: using IPv4LL address 169.254.18.158
> br0: adding route to 169.254.0.0/16
> br0: changing default route
> br0: deleting route to 192.168.10.0/24
> br0: pid -128819375 deleted default route
> br0: adding default route
>
> In 9.1.4 it is:
> br0: failed to renew DHCP, rebinding
> br0: DHCP lease expired, extending lease
> br0: soliciting a DHCP lease
> br0: pid 0 deleted IP address 192.168.10.20/24
> br0: deleting route to 192.168.10.0/24
> br0: deleting default route via 192.168.10.1
> br0: rebinding lease of 192.168.10.20
> br0: probing for an IPv4LL address
> br0: timed out contacting a DHCP server, using last lease
> br0: probing address 192.168.10.20/24
> br0: soliciting a DHCP lease
> br0: using IPv4LL address 169.254.18.158
> br0: adding route to 169.254.0.0/16
> br0: adding default route
>
> Any thoughts?

Well, technically you could have IPv4LL and a DHCP lease active at the same 
time. If you don't want IPv4LL, then turn it off in dhcpcd.conf with the 
noipv4ll directive.

The issue here is that we cannot apply address lifetimes (also applicable to 
IPv6) when extending the last lease otherwise the kernel will expire the address.

Rather than adding risky code to manage this, I've committed a fix just to set 
infinite lifetimes and let the existing dhcpcd code manage the lifecycle of the 
address as some OS's don't even have lifetimes for IPv6 addresses.

Patch here:
https://roy.marples.name/cgit/dhcpcd.git/commit/?id=ffb2feb302ecf3600aa905eb78bc864f6a5eb0f5

I don't have time to extensively test this right, hopefully you can!
Let me know how it works out.

Roy