Code change:
<!-- Please use this template while reporting a bug and provide as much info as possible. Not doing so may result in your bug not being addressed in a timely manner. Thanks! If the matter is security related, please disclose it privately via --What happened: , from whatever combination of inputs we stuck into it, segfaulted. The segfault, which originates from a slightly modified fork of v1.17, looks as such: Translated to master, where the problem appears to be present, the segfault originates from this call: And that is called from here: This seems odd, because The only pointer involved in the segfaulting call is itself The caller nil-checks before calling a method on . I did some digging and found , which is a fix for this problem. However, this fix appears to be undone in . There doesn't seem to be a reason for this to have been changed in the latter PR. What you expected to happen: should not segfault from any bizarre combination of user input. If the situation is invalid, it should fail gracefully. How to reproduce it (as minimally and precisely as possible): Honestly, I'm not 100% sure what combination of inputs we crammed into , but I can locate them and post them if necessary. Anything else we need to know?: I don't feel confident opening a PR to fix this myself, but in addition to recreating the fix from , a comment should be explaining why there is this weird, seemingly pointless layer of indirection when assigning to the interface, so that this doesn't get un-fixed again.
Maybe decompose the above statement into multiple lines which should give us more idea which field was nil.
/sig network These SIGs are my best guesses for this issue. Please comment if I am incorrect about one. I am a bot run by vllry. ‍
can't be nil, as it is of type , which is not an interface or pointer is an interface. However, when built from the exported constructor, , it is set to a literal , which is likewise not a pointer Therefore, the only remaining field is itself. Plus, I don't quite recall my go segfault stack trace syntax, but I'm relatively sure that indicates that the first argument to the method is , nil, and that the first argument to methods is the object being called on.
/triage unresolved Comment when the issue is assessed and confirmed. I am a bot run by vllry. ‍
When config.HealthzBindAddress is empty, we would encounter the scenario depicted in the stack trace. I have proposed a fix.
/assign
That commit, , is part of the PR that I believe introduced the problem. I strongly believe the problem to be one of a non-nil interface with a nil receiver. This is the only way that could be nil in the snippet of code from . Before PR (the changes from which are present in the version I ran), there was this odd looking set of code: The variable healthzServer, which is a pointer of type , was assigned to the variable , which is an interface of type . Then, later on, the variable was passed to , as an argument of type . This looks unexpected, and it appears that the variable is extraneous. After the changes in PR , the variable was removed, and was passed directly to as the argument for interface type . The former set of changes, with the intermediate variable, are meant to avoid the situation of a non-nil interface with a nil value. If the variable is never set in the conditional statement, then it is a nil interface. If is passed directly, then the result is the argument to is an an interface who's value is and who's concrete type is . This means that is called with as the receiver. I strongly believe this to be the root cause of the issue, but I do not know enough about kubernetes to open a PR with the correct fix, which would be to reinstate the variable (after the renaming in , this would be a variable of type ) to use as a go-between, to once again avoid this situation of a non-nil interface with a nil receiver. I believe that the removal of the variable was out of a misunderstanding of its purpose. If my assessment of the problem is incorrect, please let me know so I can understand where my logic is wrong. It is very possible that I am misunderstanding the phenomenon of a non-nil interface with a nil receiver. I would open a PR myself, but I do not know enough about Kubernetes to be confident in my ability to correctly fix and test this problem.
/remove-triage unresolved

Related discussion:
text: } // NewProxierHealthServer returns a proxier health http server. <del> func NewProxierHealthServer(addr string, healthTimeout time.Duration, recorder record.EventRecorder, nodeRef *v1.ObjectReference) *ProxierHealthServer { </del> <ins> func NewProxierHealthServer(addr string, healthTimeout time.Duration, recorder record.EventRecorder, nodeRef *v1.ObjectReference) ProxierHealthUpdater { </ins> return newProxierHealthServer(stdNetListener{}, stdHTTPServerFactory{}, clock.RealClock{}, addr, healthTimeout, recorder, nodeRef) } <del> func newProxierHealthServer(listener listener, httpServerFactory httpServerFactory, c clock.Clock, addr string, healthTimeout time.Duration, recorder record.EventRecorder, nodeRef *v1.ObjectReference) *ProxierHealthServer { return &ProxierHealthServer{ </del> <ins> func newProxierHealthServer(listener listener, httpServerFactory httpServerFactory, c clock.Clock, addr string, healthTimeout time.Duration, recorder record.EventRecorder, nodeRef *v1.ObjectReference) *proxierHealthServer { return &proxierHealthServer{ </ins> listener:      listener, httpFactory:   httpServerFactory, clock:         c,