Use shared informers instead of creating local controllers/reflectors
for the proxy's endpoints and service configs. This allows downstream
integrators to pass in preexisting shared informers to save on memory &
cpu usage.
This also enables the cache mutation detector for kube-proxy for those
presubmit jobs that already turn it on.
Automatic merge from submit-queue
Extensible Userspace Proxy
This PR refactors the userspace proxy to allow for custom proxy socket implementations.
It changes the the ProxySocket interface to ensure that other packages can properly implement it (making sure all arguments are publicly exposed types, etc), and adds in a mechanism for an implementation to create an instance of the userspace proxy with a non-standard ProxySocket.
Custom ProxySockets are useful to inject additional logic into the actual proxying. For example, our idling proxier uses a custom proxy socket to hold connections and notify the cluster that idled scalable resources need to be woken up.
Also-Authored-By: Ben Bennett bbennett@redhat.com
Automatic merge from submit-queue (batch tested with PRs 42200, 39535, 41708, 41487, 41335)
Update kube-proxy support for Windows
**What this PR does / why we need it**:
The kube-proxy is built upon the sophisticated iptables NAT rules. Windows does not have an equivalent capability. This introduces a change to the architecture of the user space mode of the Windows version of kube-proxy to match the capabilities of Windows.
The proxy is organized around service ports and portals. For each service a service port is created and then a portal, or iptables NAT rule, is opened for each service ip, external ip, node port, and ingress ip. This PR merges the service port and portal into a single concept of a "ServicePortPortal" where there is one connection opened for each of service IP, external ip, node port, and ingress IP.
This PR only affects the Windows kube-proxy. It is important for the Windows kube-proxy because it removes the limited portproxy rule and RRAS service and enables full tcp/udp capability to services.
**Special notes for your reviewer**:
**Release note**:
```
Add tcp/udp userspace proxy support for Windows.
```
This changes the userspace proxy so that it cleans up its conntrack
settings when a service is removed (as the iptables proxy already
does). This could theoretically cause problems when a UDP service
as deleted and recreated quickly (with the same IP address). As
long as packets from the same UDP source IP and port were going to
the same destination IP and port, the the conntrack would apply and
the packets would be sent to the old destination.
This is astronomically unlikely if you did not specify the IP address
to use in the service, and even then, only happens with an "established"
UDP connection. However, in cases where a service could be "switched"
between using the iptables proxy and the userspace proxy, this case
becomes much more frequent.
