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[policy] lower default minrelaytxfee and incrementalrelayfee to 100sat/kvB

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Let's say an attacker wants to use/exhaust the network's bandwidth, and
has the choice between renting resources from a commercial provider and
getting the network to "spam" itself it by sending unconfirmed
transactions. We'd like the latter to be more expensive than the former.

The bandwidth for relaying a transaction across the network is roughly
its serialized size (plus relay overhead) x number of nodes. A 1000vB
transaction is 1000-4000B serialized. With 100k nodes, that's 0.1-0.4GB
If the going rate for commercial services is 10c/GB, that's like 1-4c per kvB
of transaction data, so a 1000vB transaction should pay at least $0.04.

At a price of 120k USD/BTC, 100sat is about $0.12. This price allows us
to tolerate a large decrease in the conversion rate or increase in the
number of nodes.

Github-Pull: #33106
Rebased-From: 6da5de58ca
This commit is contained in:
glozow
2025-07-29 14:37:16 -04:00
parent bbdab3ef7b
commit 9dd7efc8c3
12 changed files with 54 additions and 52 deletions
Download Patch File Download Diff File Expand all files Collapse all files

24
src/test/mempool_tests.cpp
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@@ -443,7 +443,7 @@ BOOST_AUTO_TEST_CASE(MempoolSizeLimitTest)
tx1.vout.resize(1);
tx1.vout[0].scriptPubKey = CScript() << OP_1 << OP_EQUAL;
tx1.vout[0].nValue = 10 * COIN;
AddToMempool(pool, entry.Fee(10000LL).FromTx(tx1));
AddToMempool(pool, entry.Fee(1000LL).FromTx(tx1));
CMutableTransaction tx2 = CMutableTransaction();
tx2.vin.resize(1);
@@ -451,7 +451,7 @@ BOOST_AUTO_TEST_CASE(MempoolSizeLimitTest)
tx2.vout.resize(1);
tx2.vout[0].scriptPubKey = CScript() << OP_2 << OP_EQUAL;
tx2.vout[0].nValue = 10 * COIN;
AddToMempool(pool, entry.Fee(5000LL).FromTx(tx2));
AddToMempool(pool, entry.Fee(500LL).FromTx(tx2));
pool.TrimToSize(pool.DynamicMemoryUsage()); // should do nothing
BOOST_CHECK(pool.exists(GenTxid::Txid(tx1.GetHash())));
@@ -469,7 +469,7 @@ BOOST_AUTO_TEST_CASE(MempoolSizeLimitTest)
tx3.vout.resize(1);
tx3.vout[0].scriptPubKey = CScript() << OP_3 << OP_EQUAL;
tx3.vout[0].nValue = 10 * COIN;
AddToMempool(pool, entry.Fee(20000LL).FromTx(tx3));
AddToMempool(pool, entry.Fee(2000LL).FromTx(tx3));
pool.TrimToSize(pool.DynamicMemoryUsage() * 3 / 4); // tx3 should pay for tx2 (CPFP)
BOOST_CHECK(!pool.exists(GenTxid::Txid(tx1.GetHash())));
@@ -481,7 +481,7 @@ BOOST_AUTO_TEST_CASE(MempoolSizeLimitTest)
BOOST_CHECK(!pool.exists(GenTxid::Txid(tx2.GetHash())));
BOOST_CHECK(!pool.exists(GenTxid::Txid(tx3.GetHash())));
CFeeRate maxFeeRateRemoved(25000, GetVirtualTransactionSize(CTransaction(tx3)) + GetVirtualTransactionSize(CTransaction(tx2)));
CFeeRate maxFeeRateRemoved(2500, GetVirtualTransactionSize(CTransaction(tx3)) + GetVirtualTransactionSize(CTransaction(tx2)));
BOOST_CHECK_EQUAL(pool.GetMinFee(1).GetFeePerK(), maxFeeRateRemoved.GetFeePerK() + DEFAULT_INCREMENTAL_RELAY_FEE);
CMutableTransaction tx4 = CMutableTransaction();
@@ -532,10 +532,10 @@ BOOST_AUTO_TEST_CASE(MempoolSizeLimitTest)
tx7.vout[1].scriptPubKey = CScript() << OP_7 << OP_EQUAL;
tx7.vout[1].nValue = 10 * COIN;
AddToMempool(pool, entry.Fee(7000LL).FromTx(tx4));
AddToMempool(pool, entry.Fee(1000LL).FromTx(tx5));
AddToMempool(pool, entry.Fee(1100LL).FromTx(tx6));
AddToMempool(pool, entry.Fee(9000LL).FromTx(tx7));
AddToMempool(pool, entry.Fee(700LL).FromTx(tx4));
AddToMempool(pool, entry.Fee(100LL).FromTx(tx5));
AddToMempool(pool, entry.Fee(110LL).FromTx(tx6));
AddToMempool(pool, entry.Fee(900LL).FromTx(tx7));
// we only require this to remove, at max, 2 txn, because it's not clear what we're really optimizing for aside from that
pool.TrimToSize(pool.DynamicMemoryUsage() - 1);
@@ -544,8 +544,8 @@ BOOST_AUTO_TEST_CASE(MempoolSizeLimitTest)
BOOST_CHECK(!pool.exists(GenTxid::Txid(tx7.GetHash())));
if (!pool.exists(GenTxid::Txid(tx5.GetHash())))
AddToMempool(pool, entry.Fee(1000LL).FromTx(tx5));
AddToMempool(pool, entry.Fee(9000LL).FromTx(tx7));
AddToMempool(pool, entry.Fee(100LL).FromTx(tx5));
AddToMempool(pool, entry.Fee(900LL).FromTx(tx7));
pool.TrimToSize(pool.DynamicMemoryUsage() / 2); // should maximize mempool size by only removing 5/7
BOOST_CHECK(pool.exists(GenTxid::Txid(tx4.GetHash())));
@@ -553,8 +553,8 @@ BOOST_AUTO_TEST_CASE(MempoolSizeLimitTest)
BOOST_CHECK(pool.exists(GenTxid::Txid(tx6.GetHash())));
BOOST_CHECK(!pool.exists(GenTxid::Txid(tx7.GetHash())));
AddToMempool(pool, entry.Fee(1000LL).FromTx(tx5));
AddToMempool(pool, entry.Fee(9000LL).FromTx(tx7));
AddToMempool(pool, entry.Fee(100LL).FromTx(tx5));
AddToMempool(pool, entry.Fee(900LL).FromTx(tx7));
std::vector<CTransactionRef> vtx;
SetMockTime(42);