Cilium operator incorrectly calculates ExcessIPs when both IPPrefixes and Secondary IPAddresses are in use.
Below is an example where I have 4 individual IP addresses and one prefix allocated. So my Available IPs are 20(16 from prefix), UsedIPs are 16 because 8 of those IPs from prefix are in use so we can consider all of them are in use per this function. We do not need any IPs and preAllocate = 8

time=2025-06-04T22:38:19Z level=info msg="Available IPs are "  !BADKEY=20
time=2025-06-04T22:38:19Z level=info msg="usedIPForExcessCalc are" !BADKEY=16
time=2025-06-04T22:38:19Z level=info msg="neededIps are"  !BADKEY=0
time=2025-06-04T22:38:19Z level=info msg="ExcessIPs from ipam " !BADKEY=0

When we calculate excesss IPs in calculateExcessIPs function,
we have the below formula

excessIPs = max(availableIPs-usedIPs-preAllocate-maxAboveWatermark, 0)

By using above values if calculate excessIPs, it's -4 instead of 4 because we are using preAllocate in this case.

excessIPs = max(20-16-8-0, 0) = max(-4, 0) =0

I think the right math will be, so the operator will be able to remove those 4 IP addresses if they're free.

excessIPs = max(availableIPs-usedIPs-maxAboveWatermark, 0)

we are using cilium 1.17.3