FakeIPTables barely implemented any of the iptables interface, and the
main part that it did implement, it implemented incorrectly. Fix it:
- Implement EnsureChain, DeleteChain, EnsureRule, and DeleteRule, not
just SaveInto/Restore/RestoreAll.
- Restore/RestoreAll now correctly merge the provided state with the
existing state, rather than simply overwriting it.
- SaveInto now returns the table that was requested, rather than just
echoing back the Restore/RestoreAll.
There were previously some strange iptables-rule-parsing functions
that were only used by two unit tests in pkg/proxy/ipvs. Get rid of
them and replace them with some much better iptables-rule-parsing
functions.
1. For iptables mode, add KUBE-NODEPORTS chain in filter table. Add
rules to allow healthcheck node port traffic.
2. For ipvs mode, add KUBE-NODE-PORT chain in filter table. Add
KUBE-HEALTH-CHECK-NODE-PORT ipset to allow traffic to healthcheck
node port.
Kubelet and kube-proxy both had loops to ensure that their iptables
rules didn't get deleted, by repeatedly recreating them. But on
systems with lots of iptables rules (ie, thousands of services), this
can be very slow (and thus might end up holding the iptables lock for
several seconds, blocking other operations, etc).
The specific threat that they need to worry about is
firewall-management commands that flush *all* dynamic iptables rules.
So add a new iptables.Monitor() function that handles this by creating
iptables-flush canaries and only triggering a full rule reload after
noticing that someone has deleted those chains.
The firewalld monitoring code was not well tested (and not easily
testable), would never be triggered on most platforms, and was only
being taken advantage of from one place (kube-proxy), which didn't
need it anyway since it already has its own resync loop.
Since the firewalld monitoring was the only consumer of pkg/util/dbus,
we can also now delete that.
Work around Linux kernel bug that sometimes causes multiple flows to
get mapped to the same IP:PORT and consequently some suffer packet
drops.
Also made the same update in kubelet.
Also added cross-pointers between the two bodies of code, in comments.
Some day we should eliminate the duplicate code. But today is not
that day.
