bpf: lb: remove extra SVC lookup when backend lookup fails #31595
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When lb*_local() finds that the selected backend no longer exists or is not active, it performs a fresh SVC lookup for the packet. This introduces uncertainty - we might no longer match the same SVC entry, and all earlier checks in eg. nodeport_lb*() become invalid. But as this additional lookup only happens in the CT_REPLY case, we have actually obtained the backend_id from the CT entry. And there is no reason to mistrust the initially matched SVC entry (we haven't even used it to derive the "bad" backend). Therefore remove this additional lookup. Signed-off-by: Julian Wiedmann <jwi@isovalent.com>
All callers pass `false`, remove the redundant parameter. Signed-off-by: Julian Wiedmann <jwi@isovalent.com>
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Apr 4, 2024
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This cleans up an additional
lb*_lookup_service()in an unlikely error path. This is fragile, as we don't return the resulting service entry to the caller, who wants to apply various checks to the entry.Historically this seems to originate from a concern that the service gets updated while the datapath is processing the entry. If the backend lookup fails, we want to go back and fetch an updated entry with the actual set of backends. But in today's code, that concern should no longer apply. See the patch description for detailed reasoning.
So let's get rid of this fragile code section.