Merge bitcoin/bitcoin#21786: wallet: ensure sat/vB feerates are in range (mantissa of 3)

847288df07b45ca535c849e518b22818ab492896 test: fee rate values that cannot be represented as sat/vB (Jon Atack)
06a90fa0381c790f7bde2ab9bf47d2b22acef4a5 rpc: for sat/vB fee rates, limit ParseFixedPoint decimals to 3 (Jon Atack)
0742c7840f03505597fd2de87db97f12597ef667 rpc: enable passing decimals to AmountFromValue, add doxygen (Jon Atack)
8ce3ef57a3e9ad13c0aaa4648e8584241d53592d test: ParseFixedPoint with 3 decimals for sat/vB fee rates (Jon Atack)
b5033275979a2a495b02b25f70cadbdcc8b6eb6a test: type error and out of range fee rates where missing (Jon Atack)
c5fd4344f7fcc257062a610c8ff26ffcc9b53953 test: explicit fee rates with invalid amounts (Jon Atack)
ea6f76b66ecc52360719053489e0ec9f9a673eab test: improve zero-value explicit fee rate coverage (Jon Atack)

Pull request description:

  - Improve/close gaps in existing test coverage before making the change
  - Enable passing `decimals` to `ParseFixedPoint()` when calling `AmountFromValue()`
  - Limit explicit fee rates in sat/vB passed in by users to 3 decimals, and raise otherwise
  - Add regression test coverage

  Closes #20534.

ACKs for top commit:
  MarcoFalke:
    review ACK 847288df07b45ca535c849e518b22818ab492896 🔷

Tree-SHA512: c539d07ae9b21c0d6c8ea460beb9c8dad5559445518aace560abc3c05c588907bae189b6fd7602b3b397de4a42356136c3ec6f960d3dcf2d5d16377aef4ab5a2

1 files changed, 2 insertions, 1 deletions

diff --git a/src/wallet/rpcwallet.cpp b/src/wallet/rpcwallet.cpp
index ae337055e2..7777543ece 100644
--- a/src/wallet/rpcwallet.cpp
+++ b/src/wallet/rpcwallet.cpp
@@ -216,7 +216,8 @@ static void SetFeeEstimateMode(const CWallet& wallet, CCoinControl& cc, const Un
         if (!estimate_mode.isNull() && estimate_mode.get_str() != "unset") {
             throw JSONRPCError(RPC_INVALID_PARAMETER, "Cannot specify both estimate_mode and fee_rate");
         }
-        cc.m_feerate = CFeeRate(AmountFromValue(fee_rate), COIN);
+        // Fee rates in sat/vB cannot represent more than 3 significant digits.
+        cc.m_feerate = CFeeRate{AmountFromValue(fee_rate, /* decimals */ 3)};
         if (override_min_fee) cc.fOverrideFeeRate = true;
         // Default RBF to true for explicit fee_rate, if unset.
         if (!cc.m_signal_bip125_rbf) cc.m_signal_bip125_rbf = true;