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

@@ -355,7 +355,7 @@ impl Channel {
 
 	/// panics if channel_value_satoshis is >= (1 << 24)
 	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 >= msgs::MAX_FUNDING_SATOSHIS {
 			panic!("funding value > 2^24");
 		}
 
@@ -441,12 +441,9 @@ 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 >= msgs::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{})});
 		}

src/ln/msgs.rs

@@ -148,6 +148,16 @@ pub struct Pong {
 	pub byteslen: u16,
 }
 
+/// Maximmum `funding_satoshis` value, according to the BOLT #2 specification
+/// it's 2^24.
+pub const MAX_FUNDING_SATOSHIS: u64 = (1 << 24);
+
+#[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");
+}
+
 pub struct OpenChannel {
 	pub chain_hash: Sha256dHash,
 	pub temporary_channel_id: Uint256,