Add MAX_FUNDING_SATOSHIS constant.

This constants defines the maximum value of `open_channel.funding_satoshis`,
currently it's defined to be 2^24 according to the BOLT lightningdevkit#2 specification.
Also a test was added to check that the constant is never over 2,1x10^15
(maximum satoshis in bitcoin) if modified.

Signed-off-by: Jean Pierre Dudey <[email protected]>

Author: jeandudey

src/ln/channel.rs

@@ -316,6 +316,9 @@ const COMMITMENT_TX_BASE_WEIGHT: u64 = 724;
 const COMMITMENT_TX_WEIGHT_PER_HTLC: u64 = 172;
 const SPENDING_INPUT_FOR_A_OUTPUT_WEIGHT: u64 = 79; // prevout: 36, nSequence: 4, script len: 1, witness lengths: (3+1)/4, sig: 73/4, if-selector: 1, redeemScript: (6 ops + 2*33 pubkeys + 1*2 delay)/4
 const B_OUTPUT_PLUS_SPENDING_INPUT_WEIGHT: u64 = 104; // prevout: 40, nSequence: 4, script len: 1, witness lengths: 3/4, sig: 73/4, pubkey: 33/4, output: 31 (TODO: Wrong? Useless?)
+/// Maximmum `funding_satoshis` value, according to the BOLT #2 specification
+/// it's 2^24.
+pub const MAX_FUNDING_SATOSHIS: u64 = (1 << 24);
 
 macro_rules! secp_call {
 	( $res: expr, $err: expr ) => {
@@ -353,9 +356,9 @@ impl Channel {
 
 	// Constructors:
 
-	/// panics if channel_value_satoshis is >= (1 << 24)
+	/// panics if channel_value_satoshis is >= `MAX_FUNDING_SATOSHIS`
 	pub fn new_outbound(fee_estimator: &FeeEstimator, chan_keys: ChannelKeys, their_node_id: PublicKey, channel_value_satoshis: u64, announce_publicly: bool, user_id: u64) -> Channel {
-		if channel_value_satoshis >= (1 << 24) {
+		if channel_value_satoshis >= MAX_FUNDING_SATOSHIS {
 			panic!("funding value > 2^24");
 		}
 
@@ -441,12 +444,9 @@ impl Channel {
 	/// that we're rejecting the new channel.
 	pub fn new_from_req(fee_estimator: &FeeEstimator, chan_keys: ChannelKeys, their_node_id: PublicKey, msg: &msgs::OpenChannel, user_id: u64, announce_publicly: bool) -> Result<Channel, HandleError> {
 		// Check sanity of message fields:
-		if msg.funding_satoshis >= (1 << 24) {
+		if msg.funding_satoshis >= MAX_FUNDING_SATOSHIS {
 			return Err(HandleError{err: "funding value > 2^24", msg: Some(msgs::ErrorAction::DisconnectPeer{})});
 		}
-		if msg.funding_satoshis > 21000000 * 100000000 {
-			return Err(HandleError{err: "More funding_satoshis than there are satoshis!", msg: Some(msgs::ErrorAction::DisconnectPeer{})});
-		}
 		if msg.channel_reserve_satoshis > msg.funding_satoshis {
 			return Err(HandleError{err: "Bogus channel_reserve_satoshis", msg: Some(msgs::ErrorAction::DisconnectPeer{})});
 		}
@@ -2328,6 +2328,7 @@ mod tests {
 	use bitcoin::network::serialize::serialize;
 	use bitcoin::blockdata::transaction::Transaction;
 	use ln::channel::{Channel,ChannelKeys,HTLCOutput,HTLCState,HTLCOutputInCommitment,TxCreationKeys};
+	use ln::channel::MAX_FUNDING_SATOSHIS;
 	use ln::chan_utils;
 	use chain::chaininterface::{FeeEstimator,ConfirmationTarget};
 	use chain::transaction::OutPoint;
@@ -2345,6 +2346,12 @@ mod tests {
 		}
 	}
 
+	#[test]
+	fn test_max_funding_satoshis() {
+		assert!(MAX_FUNDING_SATOSHIS <= 21_000_000 * 100_000_000,
+		        "MAX_FUNDING_SATOSHIS is greater than all satoshis on existence");
+	}
+
 	#[test]
 	fn outbound_commitment_test() {
 		// Test vectors from BOLT 3 Appendix C:

src/ln/channelmanager.rs

@@ -202,7 +202,7 @@ impl ChannelManager {
 	/// the main "logic hub" for all channel-related actions, and implements ChannelMessageHandler.
 	/// fee_proportional_millionths is an optional fee to charge any payments routed through us.
 	/// Non-proportional fees are fixed according to our risk using the provided fee estimator.
-	/// panics if channel_value_satoshis is >= (1 << 24)!
+	/// panics if channel_value_satoshis is >= `MAX_FUNDING_SATOSHIS`!
 	pub fn new(our_network_key: SecretKey, fee_proportional_millionths: u32, announce_channels_publicly: bool, network: Network, feeest: Arc<FeeEstimator>, monitor: Arc<ManyChannelMonitor>, chain_monitor: Arc<ChainWatchInterface>, tx_broadcaster: Arc<BroadcasterInterface>) -> Result<Arc<ChannelManager>, secp256k1::Error> {
 		let secp_ctx = Secp256k1::new();