The initial impl didn't capture the following edge case:
- Tree has 3 (or more) layers + 1 leaf layeri
- Leaf layer last chunk IS full
- Layer 0 last chunk is NOT full
- Layer 1 last chunk is NOT full
- Layer 2 last chunk IS NOT full
In this case, when updating layer 1, we need to use layer 0's old
last hash to update layer 1's old last hash. Same for Layer 2.
The solution is to use logic that checks the *prev* layer when
updating a layer to determine if the old last hash from the prev
layer is needed.
This commit restructures the grow_tree impl to account for this
and simplifies the approach as follows:
1. Read the tree to get num leaf tuples + last hashes in each layer
2. Get the tree extension using the above values + new leaf tuples
2a. Prior to updating the leaf layer, call the function
get_update_leaf_layer_metadata. This function uses existing totals
in the leaf layer, the new total of leaf tuples, and tree params
to calculate how the layer after the leaf layer should be updated.
2b. For each subsequent layer, call the function
get_update_layer_metadata. This function uses the existing totals
in the *prev* layer, the new total of children in the *prev* layer,
and tree params to calculate how the layer should be updated.
3. Grow the tree using the tree extension.
This approach isolates update logic and actual hashing into neat
structured functions, rather than mix the two. This makes the code
easier to follow without needing to keep so much in your head at
one time.
- When retrieving last chunks, set next_start_child_chunk_index
so can know the correct start index without needing to modify
the offset
- Other smaller cleanup
- When background syncing, the wallet wipes the spend key
from memory and processes all new transactions. The wallet saves
all receives, spends, and "plausible" spends of receives the
wallet does not know key images for.
- When background sync disabled, the wallet processes all
background synced txs and then clears the background sync cache.
- Adding "plausible" spends to the background sync cache ensures
that the wallet does not need to query the daemon to see if any
received outputs were spent while background sync was enabled.
This would harm privacy especially for users of 3rd party daemons.
- To enable the feature in the CLI wallet, the user can set
background-sync to reuse-wallet-password or
custom-background-password and the wallet automatically syncs in
the background when the wallet locks, then processes all
background synced txs when the wallet is unlocked.
- The custom-background-password option enables the user to
open a distinct background wallet that only has a view key saved
and can be opened/closed/synced separately from the main wallet.
When the main wallet opens, it processes the background wallet's
cache.
- To enable the feature in the RPC wallet, there is a new
`/setup_background_sync` endpoint.
- HW, multsig and view-only wallets cannot background sync.
a46b6ba contrib: add more valgrind suppressions for spurious issues (moneromooo-monero)
7f3e31d unit_tests: fix accessing invalid memory in tree_hash test (moneromooo-monero)
