constantify key rotation index for conduit

Author: arik-so

lightning/src/ln/peers/conduit.rs

@@ -4,9 +4,12 @@ use ln::peers::{chacha, hkdf};
 use util::byte_utils;
 
 pub(super) type SymmetricKey = [u8; 32];
+
 const MESSAGE_LENGTH_HEADER_SIZE: usize = 2;
 const TAGGED_MESSAGE_LENGTH_HEADER_SIZE: usize = MESSAGE_LENGTH_HEADER_SIZE + chacha::TAG_SIZE;
 
+const KEY_ROTATION_INDEX: u32 = 1000;
+
 /// Returned after a successful handshake to encrypt and decrypt communication with peer nodes.
 /// It should not normally be manually instantiated.
 /// Automatically handles key rotation.
@@ -109,7 +112,7 @@ impl Conduit {
 
 	fn increment_nonce(nonce: &mut u32, chaining_key: &mut SymmetricKey, key: &mut SymmetricKey) {
 		*nonce += 1;
-		if *nonce == 1000 {
+		if *nonce == KEY_ROTATION_INDEX {
 			Self::rotate_key(chaining_key, key);
 			*nonce = 0;
 		}