Fix UDP outbound and clock sync timeouts on Azure workers

* Add "lb" outbound rule for worker TCP _and_ UDP traffic
* Fix Azure worker nodes clock synchronization being inactive
due to timeouts reaching the CoreOS / Flatcar NTP pool
* Fix Azure worker nodes not providing outbount UDP connectivity

Background:

Azure provides VMs outbound connectivity either by having a public
IP or via an SNAT masquerade feature bundled with their virtual
load balancing abstraction (in contrast with, say, a NAT gateway).

Azure worker nodes have only a private IP, but are associated with
the cluster load balancer's backend pool and ingress frontend IP.
Outbound traffic uses SNAT with this frontend IP. A subtle detail
with Azure SNAT seems to be that since both inbound lb_rule's are
TCP only, outbound UDP traffic isn't SNAT'd (highlights the reasons
Azure shouldn't have conflated inbound load balancing with outbound
SNAT concepts). However, adding a separate outbound rule and
disabling outbound SNAT on our ingress lb_rule's we can tell Azure
to continue load balancing as before, and support outbound SNAT for
worker traffic of both the TCP and UDP protocol.

Fixes clock synchronization timeouts:

```
systemd-timesyncd[786]: Timed out waiting for reply from
45.79.36.123:123 (3.flatcar.pool.ntp.org)
```

Azure controller nodes have their own public IP, so controllers (and
etcd) nodes have not had clock synchronization or outbound UDP issues

CHANGES.md

@@ -12,6 +12,8 @@ Notable changes between versions.
 * Rename Container Linux `clc_snippets` (bare-metal) to `snippets` for consistency
 * Fix bootstrap when `networking` mode `flannel` (non-default) is chosen ([#689](https://github.com/poseidon/typhoon/pull/689))
   * Regressed in v1.18.0 changes for Calico ([#675](https://github.com/poseidon/typhoon/pull/675))
+* Fix Azure worker UDP outbound connections ([#691](https://github.com/poseidon/typhoon/pull/691))
+  * Fix Azure worker clock sync timeouts
 
 ## v1.18.0
 

azure/container-linux/kubernetes/lb.tf

@@ -72,6 +72,7 @@ resource "azurerm_lb_rule" "ingress-http" {
   name                           = "ingress-http"
   loadbalancer_id                = azurerm_lb.cluster.id
   frontend_ip_configuration_name = "ingress"
+  disable_outbound_snat          = true
 
   protocol                = "Tcp"
   frontend_port           = 80
@@ -86,6 +87,7 @@ resource "azurerm_lb_rule" "ingress-https" {
   name                           = "ingress-https"
   loadbalancer_id                = azurerm_lb.cluster.id
   frontend_ip_configuration_name = "ingress"
+  disable_outbound_snat          = true
 
   protocol                = "Tcp"
   frontend_port           = 443
@@ -94,6 +96,20 @@ resource "azurerm_lb_rule" "ingress-https" {
   probe_id                = azurerm_lb_probe.ingress.id
 }
 
+# Worker outbound TCP/UDP SNAT
+resource "azurerm_lb_outbound_rule" "worker-outbound" {
+  resource_group_name = azurerm_resource_group.cluster.name
+
+  name            = "worker"
+  loadbalancer_id = azurerm_lb.cluster.id
+  frontend_ip_configuration {
+    name = "ingress"
+  }
+
+  protocol                = "All"
+  backend_address_pool_id = azurerm_lb_backend_address_pool.worker.id
+}
+
 # Address pool of controllers
 resource "azurerm_lb_backend_address_pool" "controller" {
   resource_group_name = azurerm_resource_group.cluster.name