d273e53b6e bench/rpc_mempool: Create ChainTestingSetup, use its CTxMemPool (Carl Dong)
020caba3df bench: Use existing CTxMemPool in TestingSetup (Carl Dong)
86e732def3 scripted-diff: test: Use CTxMemPool in TestingSetup (Carl Dong)
213457e170 test/policyestimator: Use ChainTestingSetup's CTxMemPool (Carl Dong)
319f0ceeeb rest/getutxos: Don't construct empty mempool (Carl Dong)
03574b956a tree-wide: clang-format CTxMemPool references (Carl Dong)
Pull request description:
This is part of the `libbitcoinkernel` project: #24303, https://github.com/bitcoin/bitcoin/projects/18
This PR reduces the number of call sites where we explicitly construct CTxMemPool. This is done in preparation for later PRs which decouple the mempool module from `ArgsManager`, eventually all of libbitcoinkernel will be decoupled from `ArgsManager`.
The changes in this PR:
- Allows us to have less code churn as we modify `CTxMemPool`'s constructor in later PRs
- In many cases, we can make use of existing `CTxMemPool` instances, getting rid of extraneous constructions
- In other cases, we construct a `ChainTestingSetup` and use the `CTxMemPool` there, so that we can rely on the logic in `setup_common` to set things up correctly
## Notes for Reviewers
### A note on using existing mempools
When evaluating whether or not it's appropriate to use an existing mempool in a `*TestingSetup` struct, the key is to make sure that the mempool has the same lifetime as the `*TestingSetup` struct.
Example 1: In [`src/fuzz/tx_pool.cpp`](b4f686952a/src/test/fuzz/tx_pool.cpp), the `TestingSetup` is initialized in `initialize_tx_pool` and lives as a static global, while the `CTxMemPool` is in the `tx_pool_standard` fuzz target, meaning that each time the `tx_pool_standard` fuzz target gets run, a new `CTxMemPool` is created. If we were to use the static global `TestingSetup`'s CTxMemPool we might run into problems since its `CTxMemPool` will carry state between subsequent runs. This is why we don't modify `src/fuzz/tx_pool.cpp` in this PR.
Example 2: In [`src/bench/mempool_eviction.cpp`](b4f686952a/src/bench/mempool_eviction.cpp), we see that the `TestingSetup` is in the same scope as the constructed `CTxMemPool`, so it is safe to use its `CTxMemPool`.
### A note on checking `CTxMemPool` ctor call sites
After the "tree-wide: clang-format CTxMemPool references" commit, you can find all `CTxMemPool` ctor call sites with the following command:
```sh
git grep -E -e 'make_unique<CTxMemPool>' \
-e '\bCTxMemPool\s+[^({;]+[({]' \
-e '\bCTxMemPool\s+[^;]+;' \
-e '\bnew\s+CTxMemPool\b'
```
At the end of the PR, you will find that there are still quite a few call sites that we can seemingly get rid of:
```sh
$ git grep -E -e 'make_unique<CTxMemPool>' -e '\bCTxMemPool\s+[^({;]+[({]' -e '\bCTxMemPool\s+[^;]+;' -e '\bnew\s+CTxMemPool\b'
# rearranged for easier explication
src/init.cpp: node.mempool = std::make_unique<CTxMemPool>(node.fee_estimator.get(), mempool_check_ratio);
src/test/util/setup_common.cpp: m_node.mempool = std::make_unique<CTxMemPool>(m_node.fee_estimator.get(), 1);
src/rpc/mining.cpp: CTxMemPool empty_mempool;
src/test/util/setup_common.cpp: CTxMemPool empty_pool;
src/bench/mempool_stress.cpp: CTxMemPool pool;
src/bench/mempool_stress.cpp: CTxMemPool pool;
src/test/fuzz/rbf.cpp: CTxMemPool pool;
src/test/fuzz/tx_pool.cpp: CTxMemPool tx_pool_{/*estimator=*/nullptr, /*check_ratio=*/1};
src/test/fuzz/tx_pool.cpp: CTxMemPool tx_pool_{/*estimator=*/nullptr, /*check_ratio=*/1};
src/test/fuzz/validation_load_mempool.cpp: CTxMemPool pool{};
src/txmempool.h: /** Create a new CTxMemPool.
```
Let's break them down one by one:
```
src/init.cpp: node.mempool = std::make_unique<CTxMemPool>(node.fee_estimator.get(), mempool_check_ratio);
src/test/util/setup_common.cpp: m_node.mempool = std::make_unique<CTxMemPool>(m_node.fee_estimator.get(), 1);
```
Necessary
-----
```
src/rpc/mining.cpp: CTxMemPool empty_mempool;
src/test/util/setup_common.cpp: CTxMemPool empty_pool;
```
These are fixed in #25223 where we stop requiring the `BlockAssembler` to have a `CTxMemPool` if it's not going to consult it anyway (as is the case in these two call sites)
-----
```
src/bench/mempool_stress.cpp: CTxMemPool pool;
src/bench/mempool_stress.cpp: CTxMemPool pool;
```
Fixed in #24927.
-----
```
src/test/fuzz/rbf.cpp: CTxMemPool pool;
src/test/fuzz/tx_pool.cpp: CTxMemPool tx_pool_{/*estimator=*/nullptr, /*check_ratio=*/1};
src/test/fuzz/tx_pool.cpp: CTxMemPool tx_pool_{/*estimator=*/nullptr, /*check_ratio=*/1};
src/test/fuzz/validation_load_mempool.cpp: CTxMemPool pool{};
```
These are all cases where we don't want the `CTxMemPool` state to persist between runs, see the previous section "A note on using existing mempools"
-----
```
src/txmempool.h: /** Create a new CTxMemPool.
```
It's a comment (someone link me to a grep that understands syntax plz thx)
ACKs for top commit:
laanwj:
Code review ACK d273e53b6e
Tree-SHA512: c4ff3d23217a7cc4a7145defc7b901725073ef73bcac3a252ed75f672c87e98ca0368d1d8c3f606b5b49f641e7d8387d26ef802141b650b215876f191fb6d5f9
Currently there are some confusions in net_processing:
* There is confusion between `-blocksonly mode` and `block-relay-only`,
so adjust all comments to use the same nomenclature.
* Whether to disconnect peers for providing invs/txs is implemented
differently. For example, it seems a bit confusing to disconnect
`block-relay-only` peers with `relay` permission when they send a tx
message, but not when they send an inv message. Also, keeping track of
their inv announcements seems both wasteful and confusing, as it does
nothing. This isn't possible in practice, as outbound connections do
not have permissions assigned, but sees fragile to rely on. Especially
in light of proposed changes to make that possible:
https://github.com/bitcoin/bitcoin/pull/17167
ce893c0497 doc: Update developer notes (Anthony Towns)
d2852917ee sync.h: Imply negative assertions when calling LOCK (Anthony Towns)
bba87c0553 scripted-diff: Convert global Mutexes to GlobalMutexes (Anthony Towns)
a559509a0b sync.h: Add GlobalMutex type (Anthony Towns)
be6aa72f9f qt/clientmodel: thread safety annotation for m_cached_tip_mutex (Anthony Towns)
f24bd45b37 net_processing: thread safety annotation for m_tx_relay_mutex (Anthony Towns)
Pull request description:
This changes `LOCK(mutex)` for non-global, non-recursive mutexes to be annotated with the negative capability for the mutex it refers to, to prevent . clang applies negative capabilities recursively, so this helps avoid forgetting to annotate functions.
This can't reasonably be used for globals, because clang would require every function to be annotated with `EXCLUSIVE_LOCKS_REQUIRED(!g_mutex)` for each global mutex; so this introduces a trivial `GlobalMutex` subclass of `Mutex`, and reduces the annotations for both `GlobalMutex` to `LOCKS_EXCLUDED` which only catches trivial errors (eg (`LOCK(x); LOCK(x);`).
ACKs for top commit:
MarcoFalke:
review ACK ce893c0497🐦
hebasto:
ACK ce893c0497
Tree-SHA512: 5c35e8c7677ce3d994a7e3774f4344adad496223a51b3a1d1d3b5f20684b2e1d5cff688eb3fbc8d33e1b9940dfa76e515f9434e21de6f3ce3c935e29a319f529
fa4068b4e2 Move minRelayTxFee to policy/settings (MacroFake)
Pull request description:
Seems a bit confusing to put policy stuff into validation, so fix that.
Also fix includes via `iwyu`.
ACKs for top commit:
ariard:
ACK fa4068b, the includes move compiles well locally.
ryanofsky:
Code review ACK fa4068b4e2. Make sense to move the global variable to policy/settings and the default constant to policy/policy. Ariard points out other constants that could be moved, which seems fine, but it seems like moving the global variable to be with other related global variables is more significant.
Tree-SHA512: adf9619002610d1877f3aef0a9e6115fc4c2ad64135a3e5100824c650b560c47f47ac28894c6214a50a7888355252a9f6f7cec98c23a771a1964160ef1ca77de
48262a00f5 Add functional test for block sync from inbound peers (Suhas Daftuar)
0569b5c4bb Sync chain more readily from inbound peers during IBD (Suhas Daftuar)
Pull request description:
When in IBD, if the honest chain is only known by inbound peers, then we must
eventually sync from them in order to learn it. This change allows us to
perform initial headers sync and fetch blocks from inbound peers, if we have no
blocks in flight.
The restriction on having no blocks in flight means that we will naturally
throttle our block downloads to any such inbound peers that we may be
downloading from, until we leave IBD. This is a tradeoff between preferring
outbound peers for most of our block download, versus making sure we always
eventually will get blocks we need that are only known by inbound peers even
during IBD, as otherwise we may be stuck in IBD indefinitely (which could have
cascading failure on the network, if a large fraction of the network managed to
get stuck in IBD).
Note that the test in the second commit fails on master, without the first commit.
ACKs for top commit:
ajtowns:
ACK 48262a00f5
sipa:
ACK 48262a00f5
Tree-SHA512: ffad3a05fa9a32a92226843c9128f52c275e8d51930fde7368badc340227f2ed680561c4c9f2937b4e3bd722474464849ec9b624f912f5e380ce98d71b55764d
a35f963edf Add test for getheaders behavior (Suhas Daftuar)
ef6dbe6863 Respond to getheaders if we have sufficient chainwork (Suhas Daftuar)
Pull request description:
Previously, we would check to see if we were in IBD and ignore getheaders requests accordingly. However, the IBD criteria -- an optimization mostly targeted at behavior when we have peers serving us many blocks we need to download -- is difficult to reason about in edge-case scenarios, such as if the network were to go a long time without any blocks found and nodes are getting restarted during that time.
To make things simpler to reason about, just use `nMinimumChainWork` as our anti-DoS threshold for responding to a getheaders request; as long as our chain has that much work, it should be fine to respond to a peer asking for our headers (and this should allow such a peer to request blocks from us if needed).
ACKs for top commit:
klementtan:
crACK a35f963edf
naumenkogs:
ACK a35f963edf
MarcoFalke:
review ACK a35f963edf 🗯
Tree-SHA512: 131e3872e7fe80382ea9c1ec202d6c2dc59c006355c69000aa3f4ce6bccd02a6c689c8cb8f3542b5d9bc48bfa61edcbd1a78535c0b79018971d02bed2655d284
fa1b76aeb0 Do not call global Params() when chainman is in scope (MacroFake)
fa30234be8 Do not pass CChainParams& to PeerManager::make (MacroFake)
fafe5c0ca2 Do not pass CChainParams& to BlockAssembler constructor (MacroFake)
faf012b438 Do not pass Consensus::Params& to Chainstate helpers (MacroFake)
fa4ee53dca Do not pass time getter to Chainstate helpers (MacroFake)
Pull request description:
It seems confusing to pass chain params, consensus params, or a time function around when it is not needed.
Fix this by:
* Inlining the passed time getter function. I don't see a use case why this should be mockable.
* Using `chainman.GetConsensus()` or `chainman.GetParams()`, where possible.
ACKs for top commit:
promag:
Code review ACK fa1b76aeb0.
vincenzopalazzo:
ACK fa1b76aeb0
Tree-SHA512: 1abff5cba4b4871d97f17dbcdf67bc9255ff21fa4150a79a74e39b28f0610eab3e7dee24d56872dd6e111f003b55e288958cdd467e6218368d896f191e4ec9cd
Could be verified with
$ ./configure CC=clang CXX=clang++ CXXFLAGS='-Wthread-safety -Wthread-safety-negative'
$ make clean
$ make 2>&1 | grep m_tx_relay_mutex
Could be verified with
$ ./configure CC=clang CXX=clang++ CXXFLAGS='-Wthread-safety -Wthread-safety-negative'
$ make clean
$ make 2>&1 | grep m_most_recent_block_mutex
bf6526f4a0 [test] Remove segwit argument from build_block_on_tip() (John Newbery)
c65bf50b44 Remove fUseWTXID parameter from CBlockHeaderAndShortTxIDs constructor (John Newbery)
Pull request description:
This implements two of the suggestions from code reviews of PR 20799:
- Remove fUseWTXID parameter from CBlockHeaderAndShortTxIDs constructor
- Remove segwit argument from build_block_on_tip()
ACKs for top commit:
dergoegge:
Code review ACK bf6526f4a0
naumenkogs:
ACK bf6526f4a0
Tree-SHA512: d553791d1364b9e655183755e829b195c9b47f59c62371dbae49d9c0f8d84fec58cf18f4dde89591672ef5658e18c9cf0206c2efd70606980f87e506bc3bd4e5
9db82f1bca [net processing] Don't initialize TxRelay for non-tx-relay peers. (John Newbery)
b0a4ac9c26 [net processing] Add m_tx_relay_mutex to protect m_tx_relay ptr (John Newbery)
290a8dab02 [net processing] Comment all TxRelay members (John Newbery)
42e3250497 [net processing] [refactor] Move m_next_send_feefilter and m_fee_filter_sent (John Newbery)
Pull request description:
block-relay-only connections are additional outbound connections that bitcoind makes since v0.19. They participate in block relay, but do not propagate transactions or addresses. They were introduced in #15759.
When creating an outbound block-relay-only connection, since we know that we're never going to announce transactions over that connection, we can save on memory usage by not a `TxRelay` data structure for that connection. When receiving an inbound connection, we don't know whether the connection was opened by the peer as block-relay-only or not, and therefore we always construct a `TxRelay` data structure for inbound connections.
However, it is possible to tell whether an inbound connection will ever request that we start announcing transactions to it. The `fRelay` field in the `version` message may be set to `0` to indicate that the peer does not wish to receive transaction announcements. The peer may later request that we start announcing transactions to it by sending a `filterload` or `filterclear` message, **but only if we have offered `NODE_BLOOM` services to that peer**. `NODE_BLOOM` services are disabled by default, and it has been recommended for some time that users not enable `NODE_BLOOM` services on public connections, for privacy and anti-DoS reasons.
Therefore, if we have not offered `NODE_BLOOM` to the peer _and_ it has set `fRelay` to `0`, then we know that it will never request transaction announcements, and that we can save resources by not initializing the `TxRelay` data structure.
ACKs for top commit:
MarcoFalke:
review ACK 9db82f1bca🖖
dergoegge:
Code review ACK 9db82f1bca
naumenkogs:
ACK 9db82f1bca
Tree-SHA512: 83a449a56cd6bf6ad05369f5ab91516e51b8c471c07ae38c886d51461e942d492ca34ae63d329c46e56d96d0baf59a3e34233e4289868f911db3b567072bdc41
Delay initializing the TxRelay data structure for a peer until we receive
a version message from that peer. At that point we'll know whether it
will ever relay transactions. We only initialize the m_tx_relay
data structure if:
- this isn't an outbound block-relay-only connection; AND
- fRelay=true OR we're offering NODE_BLOOM to this peer
(NODE_BLOOM means that the peer may turn on tx relay later)
This fully comments all the TxRelay members. The only significant change
is to the comment for m_relay_txs. Previously the comment stated that
one of the purposes of the field was that "We don't relay tx invs before
receiving the peer's version message". However, even without the
m_relay_txs flag, we would not send transactions to the peer before
receiving the `version` message, since SendMessages() returns
immediately if fSuccessfullyConnected is not set to true, which only
happens once a `version` and `verack` message have been received.
Move m_next_send_feefilter and m_fee_filter_sent out of the `TxRelay`
data structure. All of the other members of `TxRelay` are related to
sending transactions _to_ the peer, whereas m_fee_filter_sent and
m_next_send_feefilter are both related to receiving transactions _from_
the peer. A node's tx relay behaviour is not always symmetrical (eg a
blocksonly node will ignore incoming transactions, but may still send
out its own transactions), so it doesn't make sense to group the
feefilter sending data with the TxRelay data in a single structure.
This does not change behaviour, since IsBlockOnlyConn() is always equal
to !peer.m_tx_relay. We still don't send feefilter messages to outbound
block-relay-only peers (tested in p2p_feefilter.py).
When in IBD, if the honest chain is only known by inbound peers, then we must
eventually sync from them in order to learn it. This change allows us to
perform initial headers sync and fetch blocks from inbound peers, if we have no
blocks in flight.
The restriction on having no blocks in flight means that we will naturally
throttle our block downloads to any such inbound peers that we may be
downloading from, until we leave IBD. This is a tradeoff between preferring
outbound peers for most of our block download, versus making sure we always
eventually will get blocks we need that are only known by inbound peers even
during IBD, as otherwise we may be stuck in IBD indefinitely (which could have
cascading failure on the network, if a large fraction of the network managed to
get stuck in IBD).
All uses of CBlockHeaderAndShortTxIDs in the product code are
constructed with fUseWTXID=true, so remove the parameter.
There is one use of the CBlockHeaderAndShortTxIDs constructor with
fUseWTXID=false in the unit tests. This is used to construct a
CBlockHeaderAndShortTxIDs for a block with only the coinbase
transaction, so setting fUseWTXID to true or false makes no difference.
Suggested in https://github.com/bitcoin/bitcoin/pull/20799#pullrequestreview-963480278
In each of the critical sections, only the the guarded variables are
accessed, without any chance that within one section another one is
called. Hence, we can use an ordinary Mutex instead of RecursiveMutex.
436ce0233c sync.h: strengthen AssertLockNotHeld assertion (Anthony Towns)
7d73f58e9c Increase threadsafety annotation coverage (Anthony Towns)
Pull request description:
This changes `AssertLockNotHeld` so that it is annotated with the negative capability for the mutex it refers to. clang applies negative capabilities recursively, so this helps avoid forgetting to annotate functions.
Note that this can't reasonably be used for globals, because clang would require every function to be annotated with `EXCLUSIVE_LOCKS_REQUIRED(!g_mutex)` for each global mutex. At present, the only global mutexes that use `AssertLockNotHeld` are `RecursiveMutex` so we treat that as an exception in order to avoid having to add an excessive number of negative annotations.
ACKs for top commit:
vasild:
ACK 436ce0233c
MarcoFalke:
review ACK 436ce0233c🌺
Tree-SHA512: 5f16d098790a36b5277324d5ee89cdc87033c19b11c7943c2f630a41c2e3998eb39d356a763e857f4d8fefb6c0c02291f720bb6769bcbdf5e2cd765bf266ab8c
This introduces an early exit in PeerManagerImpl::NewPoWValidBlock() if
segwit has not been activated for the block. This means that we won't cache the
block/compact block for fast relay and won't relay the cmpctblock
immediately to peers that have requested hb compact blocks. This is fine
because any block where segwit is not yet activated is buried deep in
the chain, and so compact block relay will not be effective.
It's ok not to cache the block/compact block for fast relay for the same
reason - the block must be very deeply buried in the block chain.
ProcessBlockAvailability() also won't get called for all nodes. This is
also fine, since that function only updates hashLastUnknownBlock
and pindexBestKnownBlock, and is called early in every SendMessages()
call.
Subsequent commits will remove support for other versions of compact blocks.
Add a test that a received `sendcmpct` message with version = 1 is
ignored.
bb5c24b120 validation: move g_versionbitscache into ChainstateManager (Anthony Towns)
eca22c726a test/versionbits: make versionbitscache a parameter (Anthony Towns)
d603f1d8a7 deploymentstatus: make versionbitscache a parameter (Anthony Towns)
78adef1753 refactor: use chainman instead of chainParams for DeploymentActive* (Anthony Towns)
deffe0df6c deploymentstatus: allow chainman in place of consensusParams (Anthony Towns)
eaa2e3f25c validation: move UpdateUncommittedBlockStructures and GenerateCoinbaseCommitment into ChainstateManager (Anthony Towns)
5c67e84d37 validation: replace ::Params() calls with chainstate/chainman member (Anthony Towns)
38860f93b6 validation: remove redundant CChainParams params from ChainstateManager methods (Anthony Towns)
69675ea4e7 validation: add CChainParams to ChainstateManager (Anthony Towns)
Pull request description:
Gives `ChainstateManager` a reference to the `CChainParams` its working on, and simplifies some of the functions that would otherwise take that as a parameter. Removes the `g_versionbitscache` global by moving it into `ChainstateManager`.
ACKs for top commit:
dongcarl:
reACK bb5c24b120
MarcoFalke:
review ACK bb5c24b120📙
Tree-SHA512: 3fa74905e5df561e3e74bb0b8fce6085c5311e6633e7d74c0fb0c82a907f5bbb1fd4ebc5d11d4f0b1c019bb51eabb9f6e4bcc4652a696d36a5878c807b85f121
ab1ea29ba1 refactor: make GetRand a template, remove GetRandInt (pasta)
Pull request description:
makes GetRand a template for which any integral type can be used, where the default behavior is to return a random integral up to the max of the integral unless a max is provided.
This simplifies a lot of code from GetRand(std::numeric_limits<uint64_t>::max() -> GetRand<uint64_t>()
ACKs for top commit:
laanwj:
Code review ACK ab1ea29ba1
Tree-SHA512: db5082a0e21783389f1be898ae73e097b31ab48cab1a2c0e29348a4adeb545d4098193aa72a547c6baa6e8205699aafec38d6a27b3d65522fb3246f91b4daae9
778343a379 scripted-diff: Rename PeerManagerImpl members (dergoegge)
91c339243e [net processing] Move nHighestFastAnnounce into PeerManagerImpl (dergoegge)
10b83e2aa3 [net processing] Move block cache state into PeerManagerImpl (dergoegge)
a4c55a93ef [net processing] Inline and simplify UpdatePreferredDownload (dergoegge)
490c08f96a [net processing] Move nPreferredDownload into PeerManagerImpl (dergoegge)
a292df283a [net processing] Move mapNodeState into PeerManagerImpl (dergoegge)
37ecaf3e7a [net processing] Move CNodeState declaration above PeerManagerImpl (dergoegge)
Pull request description:
This PR moves the remaining net processing globals into `PeerManagerImpl`. This will make testing the peer manager in isolation easier and also acts as a code clean up.
ACKs for top commit:
jnewbery:
Code review ACK 778343a379
MarcoFalke:
ACK 778343a379 🗒
Tree-SHA512: 4f22105d1de37b94c3ef349f38784a30cf8d450d394a6a7849e5bd78940a71e3edbffa3d25e8efb35d7f698fd255f199de7bd4c33e23af5621a6e4e67ed43cb5
2ff8f4dd81 Add tests for addr destination rotation (Gleb Naumenko)
77ccb7fce1 Use std::chrono for salting when randomizing ADDR destination (Gleb Naumenko)
Pull request description:
We currently assign a destination peer for relaying particular addresses of nodes every 24 hours, and then rotate. This is done for rate-limiting (ultimately for privacy leak reduction I think?).
Before this change, 24 hours was defined as uint. I replaced it with std::chrono, which is mockable and type-safe.
Also added couple tests for this behavior.
ACKs for top commit:
jonatack:
ACK 2ff8f4dd81
Tree-SHA512: 16f703ef3ffee13ce3afa82ca7b4baa27308af18cd2eececdce5565badfb68656a2ad9c4594b73772e4bfa99b3fb15f8e4089c1cb4be98c0bae6730a9d2f8a25
3ae7791bca refactor: use Span in random.* (pasta)
Pull request description:
~This PR does two things~
1. use a Span<unsigned char> for GetRandBytes and GetStrongRandBytes
~2. make GetRand a template for which any integral type can be used, where the default behavior is to return a random integral up to the max of the integral unless a max is provided.
This simplifies a lot of code from `GetRand(std::numeric_limits<uint64_t>::max()` -> `GetRand<uint64_t>()`~
MarcoFalke this was inspired by your comment here: https://github.com/bitcoin/bitcoin/pull/24185#issuecomment-1025514263 about using Span, so hopefully I'll be able to get this PR done and merged 😂
~Also, if requested I could revert the `GetRand(std::numeric_limits<uint64_t>::max()` -> `GetRand<uint64_t>()` related changes if it ends up causing too many conflicts~
ACKs for top commit:
laanwj:
Thank you! Code review re-ACK 3ae7791bca
Tree-SHA512: 12375a83b68b288916ba0de81cfcab4aac14389a66a36811ae850427435eb67dd55e47df9ac3ec47db4e214f4330139e548bec815fff8a3f571484ea558dca79
We inline `UpdatePreferredDownload` because it is only used in one
location during the version handshake. We simplify it by removing the
initial subtraction of `state->fPreferredDownload` from
`nPreferredDownload`. This is ok since the version handshake is only
called once per peer and `state->fPreferredDownload` will always be
false before the newly inlined code is called, making the subtraction a
noop.
