Return channel_updates when failing a HTLC for fee/CLTV reasons

[rust-lightning] / src / ln / chan_utils.rs

diff --git a/src/ln/chan_utils.rs b/src/ln/chan_utils.rs
index 81fa29f554113a5cb156205ab5be351ceb3290fb..0cace11c1cb0dd601474229d738a23526ed6029d 100644 (file)
--- a/src/ln/chan_utils.rs
+++ b/src/ln/chan_utils.rs
@@ -1,6 +1,7 @@
 use bitcoin::blockdata::script::{Script,Builder};
 use bitcoin::blockdata::opcodes;
-use bitcoin::util::hash::Hash160;
+use bitcoin::blockdata::transaction::{TxIn,TxOut,Transaction};
+use bitcoin::util::hash::{Hash160,Sha256dHash};
 
 use secp256k1::key::{PublicKey,SecretKey};
 use secp256k1::Secp256k1;
@@ -11,6 +12,9 @@ use crypto::ripemd160::Ripemd160;
 
 use util::sha2::Sha256;
 
+pub const HTLC_SUCCESS_TX_WEIGHT: u64 = 703;
+pub const HTLC_TIMEOUT_TX_WEIGHT: u64 = 663;
+
 // Various functions for key derivation and transaction creation for use within channels. Primarily
 // used in Channel and ChannelMonitor.
 
@@ -136,18 +140,18 @@ impl TxCreationKeys {
 /// the revocation key
 pub fn get_revokeable_redeemscript(revocation_key: &PublicKey, to_self_delay: u16, delayed_payment_key: &PublicKey) -> Script {
        Builder::new().push_opcode(opcodes::All::OP_IF)
-                                    .push_slice(&revocation_key.serialize())
-                                    .push_opcode(opcodes::All::OP_ELSE)
-                                    .push_int(to_self_delay as i64)
-                                    .push_opcode(opcodes::OP_CSV)
-                                    .push_opcode(opcodes::All::OP_DROP)
-                                    .push_slice(&delayed_payment_key.serialize())
-                                    .push_opcode(opcodes::All::OP_ENDIF)
-                                    .push_opcode(opcodes::All::OP_CHECKSIG)
-                                    .into_script()
+                     .push_slice(&revocation_key.serialize())
+                     .push_opcode(opcodes::All::OP_ELSE)
+                     .push_int(to_self_delay as i64)
+                     .push_opcode(opcodes::OP_CSV)
+                     .push_opcode(opcodes::All::OP_DROP)
+                     .push_slice(&delayed_payment_key.serialize())
+                     .push_opcode(opcodes::All::OP_ENDIF)
+                     .push_opcode(opcodes::All::OP_CHECKSIG)
+                     .into_script()
 }
 
-#[derive(Clone)]
+#[derive(Clone, PartialEq)]
 pub struct HTLCOutputInCommitment {
        pub offered: bool,
        pub amount_msat: u64,
@@ -233,3 +237,33 @@ pub fn get_htlc_redeemscript_with_explicit_keys(htlc: &HTLCOutputInCommitment, a
 pub fn get_htlc_redeemscript(htlc: &HTLCOutputInCommitment, keys: &TxCreationKeys) -> Script {
        get_htlc_redeemscript_with_explicit_keys(htlc, &keys.a_htlc_key, &keys.b_htlc_key, &keys.revocation_key)
 }
+
+pub fn build_htlc_transaction(prev_hash: &Sha256dHash, feerate_per_kw: u64, to_self_delay: u16, htlc: &HTLCOutputInCommitment, a_delayed_payment_key: &PublicKey, revocation_key: &PublicKey) -> Transaction {
+       let mut txins: Vec<TxIn> = Vec::new();
+       txins.push(TxIn {
+               prev_hash: prev_hash.clone(),
+               prev_index: htlc.transaction_output_index,
+               script_sig: Script::new(),
+               sequence: 0,
+               witness: Vec::new(),
+       });
+
+       let total_fee = if htlc.offered {
+                       feerate_per_kw * HTLC_TIMEOUT_TX_WEIGHT / 1000
+               } else {
+                       feerate_per_kw * HTLC_SUCCESS_TX_WEIGHT / 1000
+               };
+
+       let mut txouts: Vec<TxOut> = Vec::new();
+       txouts.push(TxOut {
+               script_pubkey: get_revokeable_redeemscript(revocation_key, to_self_delay, a_delayed_payment_key).to_v0_p2wsh(),
+               value: htlc.amount_msat / 1000 - total_fee //TODO: BOLT 3 does not specify if we should add amount_msat before dividing or if we should divide by 1000 before subtracting (as we do here)
+       });
+
+       Transaction {
+               version: 2,
+               lock_time: if htlc.offered { htlc.cltv_expiry } else { 0 },
+               input: txins,
+               output: txouts,
+       }
+}