🐛 Do not overwrite global http.DefaultClient TLSConfig - #9
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The current TLS configuration was overriding the TLSConfig for the global `http.DefaultClient`. This call is being used by controllers such as the `ExtensionConfig` controller which calls this function from multiple concurrent workers. This leads to a race where the TLS `ServerName` is configured differently to that of the URL it is trying to call and X509 validation fails. An example can be seen from the CAPI logs below: ``` E1126 12:43:22.449064 1 controller.go:347] "Reconciler error" err="failed to discover ExtensionConfig extension-config-a: failed to discover extension \"extension-config-a\": http call failed: Post \"https://extension-config-a-runtimehooks.extension-config-a-system.svc:443/hooks.runtime.cluster.x-k8s.io/v1alpha1/discovery?timeout=10s\": tls: failed to verify certificate: x509: certificate is valid for extension-config-a-runtimehooks.extension-config-a-system.svc, extension-config-a-runtimehooks.extension-config-a-system.svc.cluster.local, not extension-config-b.extension-config-b-system.svc" controller="extensionconfig" controllerGroup="runtime.cluster.x-k8s.io" controllerKind="ExtensionConfig" ExtensionConfig="extension-config-a" namespace="" name="extension-config-a" reconcileID="dfd00b69-3666-4818-b4a0-52eb1c391848" E1126 12:53:42.919995 1 controller.go:347] "Reconciler error" err="failed to discover ExtensionConfig extension-config-b: failed to discover extension \"extension-config-b\": http call failed: Post \"https://extension-config-b.extension-config-b-system.svc:443/hooks.runtime.cluster.x-k8s.io/v1alpha1/discovery?timeout=10s\": tls: failed to verify certificate: x509: certificate is valid for extension-config-b.extension-config-b-system.svc, extension-config-b.extension-config-b-system.svc.cluster.local, not extension-config-a-runtimehooks.extension-config-a-system.svc" controller="extensionconfig" controllerGroup="runtime.cluster.x-k8s.io" controllerKind="ExtensionConfig" ExtensionConfig="extension-config-b" namespace="" name="extension-config-b" reconcileID="4cc93a96-cfcf-49f8-8276-b3725fc8e1b8" ``` Notice how the URL and the expected hostname are swapped in each log indicating a race (TLSConfig being reconfigured in the middle of the call by different worker threads.
jimmidyson
requested review from
dkoshkin,
dlipovetsky,
faiq and
thunderboltsid
November 26, 2025 14:42
thunderboltsid
approved these changes
Nov 26, 2025
dkoshkin
approved these changes
Nov 26, 2025
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Cherry-pick of upstream PR kubernetes-sigs#13058.
The current TLS configuration was overriding the TLSConfig for the global
http.DefaultClient. This call is being used by controllers such as theExtensionConfigcontroller which calls this function from multiple concurrent workers. This leads to a race where the TLSServerNameis configured differently to that of the URL it is trying to call and X509 validation fails. An example can be seen from the CAPI logs below:Notice how the URL and the expected hostname are swapped in each log indicating a race (TLSConfig being reconfigured in the middle of the call by different worker threads.
What this PR does / why we need it:
Which issue(s) this PR fixes (optional, in
fixes #<issue number>(, fixes #<issue_number>, ...)format, will close the issue(s) when PR gets merged):Fixes #