net: fix race condition in self-connect detection #1472
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tomt1664 force-pushed the fix_race_condition branch 4 times, most recently from b9376ea to e5f267e Compare 
…detection 16bd283 Reapply "test: p2p: check that connecting to ourself leads to disconnect" (Sebastian Falbesoner) 0dbcd4c net: prevent sending messages in `NetEventsInterface::InitializeNode` (Sebastian Falbesoner) 66673f1 net: fix race condition in self-connect detection (Sebastian Falbesoner) Pull request description: This PR fixes a recently discovered race condition in the self-connect detection (see #30362 and #30368). Initiating an outbound network connection currently involves the following steps after the socket connection is established (see [`CConnman::OpenNetworkConnection`](https://github.com/bitcoin/bitcoin/blob/bd5d1688b4311e21c0e0ff89a3ae02ef7d0543b8/src/net.cpp#L2923-L2930) method): 1. set up node state 2. queue VERSION message (both steps 1 and 2 happen in [`InitializeNode`](https://github.com/bitcoin/bitcoin/blob/bd5d1688b4311e21c0e0ff89a3ae02ef7d0543b8/src/net_processing.cpp#L1662-L1683)) 3. add new node to vector `m_nodes` If we connect to ourself, it can happen that the sent VERSION message (step 2) is received and processed locally *before* the node object is added to the connection manager's `m_nodes` vector (step 3). In this case, the self-connect remains undiscovered, as the detection doesn't find the outbound peer in `m_nodes` yet (see `CConnman::CheckIncomingNonce`). Fix this by swapping the order of 2. and 3., by taking the `PushNodeVersion` call out of `InitializeNode` and doing that in the `SendMessages` method instead, which is only called for `CNode` instances in `m_nodes`. The temporarily reverted test introduced in #30362 is readded. Fixes #30368. Thanks go to vasild, mzumsande and dergoegge for suggestions on how to fix this (see bitcoin/bitcoin#30368 (comment) ff. and bitcoin/bitcoin#30394 (comment)). ACKs for top commit: naiyoma: tested ACK [https://github.com/bitcoin/bitcoin/pull/30394/commits/16bd283b3ad05daa41259a062aee0fc05b463fa6](https://github.com/bitcoin/bitcoin/pull/30394/commits/16bd283b3ad05daa41259a062aee0fc05b463fa6), built and tested locally, test passes successfully. mzumsande: ACK 16bd283 tdb3: ACK 16bd283 glozow: ACK 16bd283 dergoegge: ACK 16bd283 Tree-SHA512: 5b8aced6cda8deb38d4cd3fe4980b8af505d37ffa0925afaa734c5d81efe9d490dc48a42e1d0d45dd2961c0e1172a3d5b6582ae9a2d642f2592a17fbdc184445
tomt1664 force-pushed the fix_race_condition branch from e5f267e to 8db506f Compare 
delta1 approved these changes Jul 9, 2025
delta1 pushed a commit to delta1/elements that referenced this pull request Jul 18, 2025
…detection ELEMENTS: cherry-picked before ElementsProject#1472 for ease of merge 16bd283 Reapply "test: p2p: check that connecting to ourself leads to disconnect" (Sebastian Falbesoner) 0dbcd4c net: prevent sending messages in `NetEventsInterface::InitializeNode` (Sebastian Falbesoner) 66673f1 net: fix race condition in self-connect detection (Sebastian Falbesoner) Pull request description: This PR fixes a recently discovered race condition in the self-connect detection (see #30362 and #30368). Initiating an outbound network connection currently involves the following steps after the socket connection is established (see [`CConnman::OpenNetworkConnection`](https://github.com/bitcoin/bitcoin/blob/bd5d1688b4311e21c0e0ff89a3ae02ef7d0543b8/src/net.cpp#L2923-L2930) method): 1. set up node state 2. queue VERSION message (both steps 1 and 2 happen in [`InitializeNode`](https://github.com/bitcoin/bitcoin/blob/bd5d1688b4311e21c0e0ff89a3ae02ef7d0543b8/src/net_processing.cpp#L1662-L1683)) 3. add new node to vector `m_nodes` If we connect to ourself, it can happen that the sent VERSION message (step 2) is received and processed locally *before* the node object is added to the connection manager's `m_nodes` vector (step 3). In this case, the self-connect remains undiscovered, as the detection doesn't find the outbound peer in `m_nodes` yet (see `CConnman::CheckIncomingNonce`). Fix this by swapping the order of 2. and 3., by taking the `PushNodeVersion` call out of `InitializeNode` and doing that in the `SendMessages` method instead, which is only called for `CNode` instances in `m_nodes`. The temporarily reverted test introduced in #30362 is readded. Fixes #30368. Thanks go to vasild, mzumsande and dergoegge for suggestions on how to fix this (see bitcoin/bitcoin#30368 (comment) ff. and bitcoin/bitcoin#30394 (comment)). ACKs for top commit: naiyoma: tested ACK [https://github.com/bitcoin/bitcoin/pull/30394/commits/16bd283b3ad05daa41259a062aee0fc05b463fa6](https://github.com/bitcoin/bitcoin/pull/30394/commits/16bd283b3ad05daa41259a062aee0fc05b463fa6), built and tested locally, test passes successfully. mzumsande: ACK 16bd283 tdb3: ACK 16bd283 glozow: ACK 16bd283 dergoegge: ACK 16bd283 Tree-SHA512: 5b8aced6cda8deb38d4cd3fe4980b8af505d37ffa0925afaa734c5d81efe9d490dc48a42e1d0d45dd2961c0e1172a3d5b6582ae9a2d642f2592a17fbdc184445 (cherry picked from commit 35dddbc)
delta1 added a commit to delta1/elements that referenced this pull request Jul 18, 2025
Kept all of the "current" changes for this after cherry-picking the upstream PR before this
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Cherry-pick of bitcoin/bitcoin#30394