GetAllLocalAddressesExcept previously iterated over net.Interfaces() and
called iface.Addrs() for each interface. iface.Addrs() internally performs
a full RTM_GETADDR netlink dump for the entire node and then filters in
user space. With many interfaces and many addresses (for example tens of
thousands of ClusterIPs bound to kube-ipvs0) the cost is
O(N_interfaces * N_addresses) and dominates syncProxyRules latency.
This change replaces the per-interface loop with a single
netlink.AddrList(nil, unix.AF_UNSPEC) call that dumps all addresses on
the node in one RTM_GETADDR request, then filters by LinkIndex in user
space. This makes the call O(N_addresses) and avoids the per-interface
fan-out.
On a production node with 251 interfaces and 19757 addresses, this
reduces GetAllLocalAddressesExcept latency from 34.8s to 60ms (~705x).
This has been replaced by `//build:...` for a long time now.
Removal of the old build tag was automated with:
for i in $(git grep -l '^// +build' | grep -v -e '^vendor/'); do if ! grep -q '^// Code generated' "$i"; then sed -i -e '/^\/\/ +build/d' "$i"; fi; done
