Merge bitcoin/bitcoin#23683: bug fix: valid but different LockPoints after a reorg

b4adc5ad6769e4a5a6179dfff271cd4c9dc47a5b [bugfix] update lockpoints correctly during reorg (glozow)
b6002b07a36f0d58dc6becd04bfcf78599056b7c MOVEONLY: update_lock_points to txmempool.h (glozow)

Pull request description:

  I introduced a bug in #22677 (sorry! :sweat_smile:)

  Mempool entries cache `LockPoints`, containing the first height/blockhash/`CBlockIndex*` at which the transaction becomes valid. During a reorg, we re-check timelocks on all mempool entries using `CheckSequenceLocks(useExistingLockPoints=false)` and remove any now-invalid entries. `CheckSequenceLocks()` also mutates the `LockPoints` passed in, and we update valid entries' `LockPoints` using `update_lock_points`. Thus, `update_lock_points(lp)` needs to be called right after `CheckSequenceLocks(lp)`, otherwise we lose the data in `lp`. I incorrectly assumed they could be called in separate loops.

  The incorrect behavior introduced is: if we have a reorg in which a timelocked mempool transaction is still valid but becomes valid at a different block, the cached `LockPoints` will be incorrect.

  This PR fixes the bug, adds a test, and adds an assertion at the end of `removeForReorg()` to check that all mempool entries' lockpoints are valid. You can reproduce the bug by running the test added in the [test] commit on the code before the [bugfix] commit.

ACKs for top commit:
  jnewbery:
    ACK b4adc5ad6769e4a5a6179dfff271cd4c9dc47a5b
  vasild:
    ACK b4adc5ad6769e4a5a6179dfff271cd4c9dc47a5b
  mzumsande:
    Code Review ACK b4adc5ad6769e4a5a6179dfff271cd4c9dc47a5b
  hebasto:
    ACK b4adc5ad6769e4a5a6179dfff271cd4c9dc47a5b
  MarcoFalke:
    re-ACK b4adc5ad6769e4a5a6179dfff271cd4c9dc47a5b 🏁

Tree-SHA512: 16b59f6ff8140d0229079ca1c6b04f2f4a00a2e49931275150e4f3fe5ac4ec109698b083fa6b223ba9511f328271cc1ab081263669d5da020af7fee83c13e401

1 files changed, 10 insertions, 0 deletions

diff --git a/src/txmempool.h b/src/txmempool.h
index df578d5111..b8c508fd90 100644
--- a/src/txmempool.h
+++ b/src/txmempool.h
@@ -312,6 +312,16 @@ public:
     }
 };
 
+struct update_lock_points
+{
+    explicit update_lock_points(const LockPoints& _lp) : lp(_lp) { }
+
+    void operator() (CTxMemPoolEntry &e) { e.UpdateLockPoints(lp); }
+
+private:
+    const LockPoints& lp;
+};
+
 // Multi_index tag names
 struct descendant_score {};
 struct entry_time {};