Log clearer error on startup if NPC cannot be started

Servers should always be upgraded before agents, but generally this isn't required because things are compatible between versions. In this case we're OK with failing closed if the user upgrades out of order, but we should give a clearer message about what steps are required to fix the issue. Signed-off-by: Brad Davidson <brad.davidson@rancher.com> (cherry picked from commit 31bbae1eb1f0372752a0479f19a3ce49ac30a24d)

Log clearer error on startup if NPC cannot be started
01fc0249 · Brad Davidson · Brad Davidson · 4efbdf33 · 01fc0249
Commit 01fc0249 authored Mar 01, 2021 by Brad Davidson Committed by Brad Davidson Mar 11, 2021
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config.go pkg/agent/config/config.go +7 -0

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--- a/pkg/agent/config/config.go
+++ b/pkg/agent/config/config.go
@@ -498,6 +498,13 @@ func get(envInfo *cmds.Agent, proxy proxy.Proxy) (*config.Node, error) {
 		nodeConfig.AgentConfig.ServiceNodePortRange = *controlConfig.ServiceNodePortRange
 	}

+	// Old versions of the server do not send enough information to correctly start the NPC. Users
+	// need to upgrade the server to at least the same version as the agent, or disable the NPC
+	// cluster-wide.
+	if controlConfig.DisableNPC == false && (controlConfig.ServiceIPRange == nil || controlConfig.ServiceNodePortRange == nil) {
+		return nil, fmt.Errorf("incompatible down-level server detected; servers must be upgraded to at least %s, or restarted with --disable-network-policy", version.Version)
+	}
+
 	nodeConfig.AgentConfig.ExtraKubeletArgs = envInfo.ExtraKubeletArgs
 	nodeConfig.AgentConfig.ExtraKubeProxyArgs = envInfo.ExtraKubeProxyArgs