Merge #19204: p2p: Reduce inv traffic during IBD

fa525e4d1cfda8c1924d2c69f43bd7ae3b98fb72 net: Avoid wasting inv traffic during IBD (MarcoFalke)
fa06d7e93489e61078cfb95ab767c001536a6e10 refactor: block import implies IsInitialBlockDownload (MarcoFalke)
faba65e696a88e5626e587f4e63fa15500cbe4d0 Add ChainstateManager::ActiveChainstate (MarcoFalke)
fabf3d64ff2bd14f762810316144bb9fd69c517c test: Add FeeFilterRounder test (MarcoFalke)

Pull request description:

  Tx-inv messages are ignored during IBD, so it would be nice if we told peers to not send them in the first place. Do that by sending two `feefilter` messages: One when the connection is made (and the node is in IBD), and another one when the node leaves IBD.

ACKs for top commit:
  jamesob:
    ACK fa525e4d1cfda8c1924d2c69f43bd7ae3b98fb72 ([`jamesob/ackr/19204.1.MarcoFalke.p2p_reduce_inv_traffic_d`](https://github.com/jamesob/bitcoin/tree/ackr/19204.1.MarcoFalke.p2p_reduce_inv_traffic_d))
  naumenkogs:
    utACK fa525e4
  gzhao408:
    ACK https://github.com/bitcoin/bitcoin/commit/fa525e4d1cfda8c1924d2c69f43bd7ae3b98fb72
  jonatack:
    re-ACK fa525e4 checked diff `git range-diff 19612ca fa8a66c fa525e4`, re-reviewed, ran tests, ran a custom p2p IBD behavior test at https://github.com/jonatack/bitcoin/commit/9321e0f223ea87d21f6fa42b61bcc8d40a0943de.
  hebasto:
    re-ACK fa525e4d1cfda8c1924d2c69f43bd7ae3b98fb72, only rebased since the [previous](https://github.com/bitcoin/bitcoin/pull/19204#pullrequestreview-429519667) review (verified with `git range-diff`).

Tree-SHA512: 2c22a5def9822396fca45d808b165b636f1143c4bdb2eaa5c7e977f1f18e8b10c86d4c180da488def38416cf3076a26de15014dfd4d86b2a7e5af88c74afb8eb

1 files changed, 15 insertions, 4 deletions

diff --git a/src/net_processing.cpp b/src/net_processing.cpp
index b5912e18a7..80e58a6dba 100644
--- a/src/net_processing.cpp
+++ b/src/net_processing.cpp
@@ -2576,7 +2576,7 @@ void ProcessMessage(
                     LogPrint(BCLog::NET, "transaction (%s) inv sent in violation of protocol, disconnecting peer=%d\n", inv.hash.ToString(), pfrom.GetId());
                     pfrom.fDisconnect = true;
                     return;
-                } else if (!fAlreadyHave && !fImporting && !fReindex && !::ChainstateActive().IsInitialBlockDownload()) {
+                } else if (!fAlreadyHave && !chainman.ActiveChainstate().IsInitialBlockDownload()) {
                     RequestTx(State(pfrom.GetId()), inv.hash, current_time);
                 }
             }
@@ -4392,10 +4392,21 @@ bool PeerLogicValidation::SendMessages(CNode* pto)
         ) {
             CAmount currentFilter = m_mempool.GetMinFee(gArgs.GetArg("-maxmempool", DEFAULT_MAX_MEMPOOL_SIZE) * 1000000).GetFeePerK();
             int64_t timeNow = GetTimeMicros();
+            static FeeFilterRounder g_filter_rounder{CFeeRate{DEFAULT_MIN_RELAY_TX_FEE}};
+            if (m_chainman.ActiveChainstate().IsInitialBlockDownload()) {
+                // Received tx-inv messages are discarded when the active
+                // chainstate is in IBD, so tell the peer to not send them.
+                currentFilter = MAX_MONEY;
+            } else {
+                static const CAmount MAX_FILTER{g_filter_rounder.round(MAX_MONEY)};
+                if (pto->m_tx_relay->lastSentFeeFilter == MAX_FILTER) {
+                    // Send the current filter if we sent MAX_FILTER previously
+                    // and made it out of IBD.
+                    pto->m_tx_relay->nextSendTimeFeeFilter = timeNow - 1;
+                }
+            }
             if (timeNow > pto->m_tx_relay->nextSendTimeFeeFilter) {
-                static CFeeRate default_feerate(DEFAULT_MIN_RELAY_TX_FEE);
-                static FeeFilterRounder filterRounder(default_feerate);
-                CAmount filterToSend = filterRounder.round(currentFilter);
+                CAmount filterToSend = g_filter_rounder.round(currentFilter);
                 // We always have a fee filter of at least minRelayTxFee
                 filterToSend = std::max(filterToSend, ::minRelayTxFee.GetFeePerK());
                 if (filterToSend != pto->m_tx_relay->lastSentFeeFilter) {