* cmd/containerboot,kube,util/linuxfw: configure kube egress proxies to route to 1+ tailnet targets
This commit is first part of the work to allow running multiple
replicas of the Kubernetes operator egress proxies per tailnet service +
to allow exposing multiple tailnet services via each proxy replica.
This expands the existing iptables/nftables-based proxy configuration
mechanism.
A proxy can now be configured to route to one or more tailnet targets
via a (mounted) config file that, for each tailnet target, specifies:
- the target's tailnet IP or FQDN
- mappings of container ports to which cluster workloads will send traffic to
tailnet target ports where the traffic should be forwarded.
Example configfile contents:
{
"some-svc": {"tailnetTarget":{"fqdn":"foo.tailnetxyz.ts.net","ports"{"tcp:4006:80":{"protocol":"tcp","matchPort":4006,"targetPort":80},"tcp:4007:443":{"protocol":"tcp","matchPort":4007,"targetPort":443}}}}
}
A proxy that is configured with this config file will configure firewall rules
to route cluster traffic to the tailnet targets. It will then watch the config file
for updates as well as monitor relevant netmap updates and reconfigure firewall
as needed.
This adds a bunch of new iptables/nftables functionality to make it easier to dynamically update
the firewall rules without needing to restart the proxy Pod as well as to make
it easier to debug/understand the rules:
- for iptables, each portmapping is a DNAT rule with a comment pointing
at the 'service',i.e:
-A PREROUTING ! -i tailscale0 -p tcp -m tcp --dport 4006 -m comment --comment "some-svc:tcp:4006 -> tcp:80" -j DNAT --to-destination 100.64.1.18:80
Additionally there is a SNAT rule for each tailnet target, to mask the source address.
- for nftables, a separate prerouting chain is created for each tailnet target
and all the portmapping rules are placed in that chain. This makes it easier
to look up rules and delete services when no longer needed.
(nftables allows hooking a custom chain to a prerouting hook, so no extra work
is needed to ensure that the rules in the service chains are evaluated).
The next steps will be to get the Kubernetes Operator to generate
the configfile and ensure it is mounted to the relevant proxy nodes.
Updates tailscale/tailscale#13406
Signed-off-by: Irbe Krumina <irbe@tailscale.com>
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