Make simulated WFP flow-context removal atomic and idempotent

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4/5
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42/100
Issue 类型
缺陷
描述清晰度
描述清楚
活跃度
活跃
技术栈
cpp
领域
networking

调研方向

Start with fwp_engine_t::test_remove_flow_context and delete_flow_context, where the shared-lock lookup of fwpm_flow_contexts is released before the exclusive-lock erase. Make find-and-erase one exclusive-lock section, copy the callback inputs, then call flowDeleteFn after unlocking. Done means concurrent removers invoke it at most once, absent entries return a defined status, and a concurrency test covers FwpsFlowRemoveContext0 against simulated deletion.

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描述

Problem

fwp_engine_t::test_remove_flow_context checks fwpm_flow_contexts under a shared lock, releases the lock, and then calls delete_flow_context, which reacquires an exclusive lock. Two concurrent removers can both observe the association. The winner erases it; the loser then finds no entry, asserts that the callout is non-null, and can invoke flowDeleteFn through a null pointer.

This occurs when simulated external flow deletion races with FwpsFlowRemoveContext during callout cleanup.

Originating review: https://github.com/microsoft/ebpf-for-windows/pull/5623#discussion_r4458625427

Desired behavior

Finding and claiming a flow-context association must be one atomic operation. Exactly one remover should own the association and invoke flowDeleteFn; later removers should receive a safe already-removed/not-found result.

The callback must still run after releasing the engine lock.

Acceptance criteria

  • Find-and-erase of fwpm_flow_contexts occurs under one exclusive lock.
  • The winning remover copies all callback inputs before releasing the lock.
  • flowDeleteFn is invoked outside the engine lock and at most once per association.
  • Missing or already-removed associations return a defined status/no-op without assertions or null dereferences.
  • FwpsFlowRemoveContext0 reports an appropriate status for an absent association.
  • A concurrency test runs cleanup removal and simulated flow deletion against the same flow.
主要语言
C++
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