Rewind the download window with the position on regression. - #10
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echennells wants to merge 2 commits into
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A regression below the position rewound the position but not the window (requested_/advanced_), and a regression above the position but within the window was ignored. Either way set_unassociated() then deferred new work until the gap at the replaced height was filled, which only a request can do, so a tip reorg stopped block download until restart while headers continued. Guard on the window and rewind both with the position. Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
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chaser_check::do_regressedrewinds the position and purges outstanding work but leavesrequested_andadvanced_at their pre-regression heights, and ignores a regression above the position even when it is inside the requested window. Either wayset_unassociatedthen defers all new work (position() < requested_) until the gap is filled, and the gap is the replaced block at the regression height, which only the deferred request can fill. Block download stops while headers continue; a restart clears it becausestart()re-seeds the window from the position.The guard now considers the window as well as the position, and both are rewound before the purge, as at start.
The validator has the same gap (second commit): after a regression it advances only on a checked event for the block above the branch point, which never arrives when that block is already associated, as when a reorg returns to a branch already downloaded. Validation stops, so the download window never advances either. It now resumes from the branch point as
startdoes.Reproduced on regtest against bitcoind: sync to N, invalidate N and mine two on a competing branch; master stays at N while patched follows. Issuing the same reorg while blocks below N are still downloading stalls at N-1 unless the guard is on the window. For the validator: mine A, invalidate it and mine B,C, then reconsider A and mine on it; the first commit alone stalls at C, both follow. The validator case was first observed as a 21 hour stall on a testnet3 block storm.
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