Clean up channel error handling a ton
[rust-lightning] / src / ln / channel.rs
index a3b3289eb65505f5194b54bae6d0ae0224a23374..5446dd914353c23bd034f61e54e59e084461a939 100644 (file)
@@ -13,7 +13,6 @@ use secp256k1;
 
 use crypto::digest::Digest;
 use crypto::hkdf::{hkdf_extract,hkdf_expand};
-use crypto::sha2::Sha256;
 
 use ln::msgs;
 use ln::msgs::{HandleError, MsgEncodable};
@@ -22,9 +21,8 @@ use ln::channelmanager::PendingForwardHTLCInfo;
 use ln::chan_utils::{TxCreationKeys,HTLCOutputInCommitment};
 use ln::chan_utils;
 use chain::chaininterface::{FeeEstimator,ConfirmationTarget};
-use util::transaction_utils;
-
-use rand::{thread_rng,Rng};
+use util::{transaction_utils,rng};
+use util::sha2::Sha256;
 
 use std::default::Default;
 use std::cmp;
@@ -43,34 +41,33 @@ pub struct ChannelKeys {
 
 impl ChannelKeys {
        pub fn new_from_seed(seed: &[u8; 32]) -> Result<ChannelKeys, secp256k1::Error> {
-               let sha = Sha256::new();
                let mut prk = [0; 32];
-               hkdf_extract(sha, b"rust-lightning key gen salt", seed, &mut prk);
+               hkdf_extract(Sha256::new(), b"rust-lightning key gen salt", seed, &mut prk);
                let secp_ctx = Secp256k1::new();
 
                let mut okm = [0; 32];
-               hkdf_expand(sha, &prk, b"rust-lightning funding key info", &mut okm);
-               let funding_key = try!(SecretKey::from_slice(&secp_ctx, &okm));
+               hkdf_expand(Sha256::new(), &prk, b"rust-lightning funding key info", &mut okm);
+               let funding_key = SecretKey::from_slice(&secp_ctx, &okm)?;
 
-               hkdf_expand(sha, &prk, b"rust-lightning revocation base key info", &mut okm);
-               let revocation_base_key = try!(SecretKey::from_slice(&secp_ctx, &okm));
+               hkdf_expand(Sha256::new(), &prk, b"rust-lightning revocation base key info", &mut okm);
+               let revocation_base_key = SecretKey::from_slice(&secp_ctx, &okm)?;
 
-               hkdf_expand(sha, &prk, b"rust-lightning payment base key info", &mut okm);
-               let payment_base_key = try!(SecretKey::from_slice(&secp_ctx, &okm));
+               hkdf_expand(Sha256::new(), &prk, b"rust-lightning payment base key info", &mut okm);
+               let payment_base_key = SecretKey::from_slice(&secp_ctx, &okm)?;
 
-               hkdf_expand(sha, &prk, b"rust-lightning delayed payment base key info", &mut okm);
-               let delayed_payment_base_key = try!(SecretKey::from_slice(&secp_ctx, &okm));
+               hkdf_expand(Sha256::new(), &prk, b"rust-lightning delayed payment base key info", &mut okm);
+               let delayed_payment_base_key = SecretKey::from_slice(&secp_ctx, &okm)?;
 
-               hkdf_expand(sha, &prk, b"rust-lightning htlc base key info", &mut okm);
-               let htlc_base_key = try!(SecretKey::from_slice(&secp_ctx, &okm));
+               hkdf_expand(Sha256::new(), &prk, b"rust-lightning htlc base key info", &mut okm);
+               let htlc_base_key = SecretKey::from_slice(&secp_ctx, &okm)?;
 
-               hkdf_expand(sha, &prk, b"rust-lightning channel close key info", &mut okm);
-               let channel_close_key = try!(SecretKey::from_slice(&secp_ctx, &okm));
+               hkdf_expand(Sha256::new(), &prk, b"rust-lightning channel close key info", &mut okm);
+               let channel_close_key = SecretKey::from_slice(&secp_ctx, &okm)?;
 
-               hkdf_expand(sha, &prk, b"rust-lightning channel monitor claim key info", &mut okm);
-               let channel_monitor_claim_key = try!(SecretKey::from_slice(&secp_ctx, &okm));
+               hkdf_expand(Sha256::new(), &prk, b"rust-lightning channel monitor claim key info", &mut okm);
+               let channel_monitor_claim_key = SecretKey::from_slice(&secp_ctx, &okm)?;
 
-               hkdf_expand(sha, &prk, b"rust-lightning local commitment seed info", &mut okm);
+               hkdf_expand(Sha256::new(), &prk, b"rust-lightning local commitment seed info", &mut okm);
 
                Ok(ChannelKeys {
                        funding_key: funding_key,
@@ -152,7 +149,20 @@ enum ChannelState {
        /// later.
        /// Flag is set on ChannelFunded.
        AwaitingRemoteRevoke = (1 << 7),
+       /// Flag which is set on ChannelFunded or FundingSent after receiving a shutdown message from
+       /// the remote end. If set, they may not add any new HTLCs to the channel, and we are expected
+       /// to respond with our own shutdown message when possible.
+       RemoteShutdownSent = (1 << 8),
+       /// Flag which is set on ChannelFunded or FundingSent after sending a shutdown message. At this
+       /// point, we may not add any new HTLCs to the channel.
+       /// TODO: Investigate some kind of timeout mechanism by which point the remote end must provide
+       /// us their shutdown.
+       LocalShutdownSent = (1 << 9),
+       /// We've successfully negotiated a closing_signed dance. At this point ChannelManager is about
+       /// to drop us, but we store this anyway.
+       ShutdownComplete = (1 << 10),
 }
+const BOTH_SIDES_SHUTDOWN_MASK: u32 = (ChannelState::LocalShutdownSent as u32 | ChannelState::RemoteShutdownSent as u32);
 
 // TODO: We should refactor this to be an Inbound/OutboundChannel until initial setup handshaking
 // has been completed, and then turn into a Channel to get compiler-time enforcement of things like
@@ -180,6 +190,8 @@ pub struct Channel {
        channel_update_count: u32,
        feerate_per_kw: u64,
 
+       last_sent_closing_fee: Option<(u64, u64)>, // (feerate, fee)
+
        /// The hash of the block in which the funding transaction reached our CONF_TARGET. We use this
        /// to detect unconfirmation after a serialize-unserialize roudtrip where we may not see a full
        /// series of block_connected/block_disconnected calls. Obviously this is not a guarantee as we
@@ -211,10 +223,12 @@ pub struct Channel {
        their_cur_commitment_point: PublicKey,
        their_node_id: PublicKey,
 
+       their_shutdown_scriptpubkey: Option<Script>,
+
        channel_monitor: ChannelMonitor,
 }
 
-const OUR_MAX_HTLCS: u16 = 1; //TODO
+const OUR_MAX_HTLCS: u16 = 5; //TODO
 const CONF_TARGET: u32 = 12; //TODO: Should be much higher
 /// Confirmation count threshold at which we close a channel. Ideally we'd keep the channel around
 /// on ice until the funding transaction gets more confirmations, but the LN protocol doesn't
@@ -233,21 +247,20 @@ const SPENDING_INPUT_FOR_A_OUTPUT_WEIGHT: u64 = 79; // prevout: 36, nSequence: 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?)
 
 macro_rules! secp_call {
-       ( $res : expr ) => {
+       ( $res: expr, $err: expr ) => {
                match $res {
                        Ok(key) => key,
                        //TODO: make the error a parameter
-                       Err(_) => return Err(HandleError{err: "Secp call failed - probably bad signature or evil data generated a bad pubkey/privkey", msg: None})
+                       Err(_) => return Err(HandleError{err: $err, msg: Some(msgs::ErrorAction::DisconnectPeer{})})
                }
        };
 }
 
-macro_rules! get_key {
-       ( $ctx : expr, $slice : expr ) => {
-               secp_call! (SecretKey::from_slice($ctx, $slice))
-       };
+macro_rules! secp_derived_key {
+       ( $res: expr ) => {
+               secp_call!($res, "Derived invalid key, peer is maliciously selecting parameters")
+       }
 }
-
 impl Channel {
        // Convert constants + channel value to limits:
        fn get_our_max_htlc_value_in_flight_msat(channel_value_satoshis: u64) -> u64 {
@@ -275,12 +288,11 @@ impl Channel {
                        panic!("funding value > 2^24");
                }
 
-               let mut rng = thread_rng();
                let feerate = fee_estimator.get_est_sat_per_vbyte(ConfirmationTarget::Normal);
                let background_feerate = fee_estimator.get_est_sat_per_vbyte(ConfirmationTarget::Background);
 
                let mut key_seed = [0u8; 32];
-               rng.fill_bytes(&mut key_seed);
+               rng::fill_bytes(&mut key_seed);
                let chan_keys = match ChannelKeys::new_from_seed(&key_seed) {
                        Ok(key) => key,
                        Err(_) => panic!("RNG is busted!")
@@ -297,7 +309,7 @@ impl Channel {
                Channel {
                        user_id: user_id,
 
-                       channel_id: Uint256([rng.gen(), rng.gen(), rng.gen(), rng.gen()]),
+                       channel_id: rng::rand_uint256(),
                        channel_state: ChannelState::OurInitSent as u32,
                        channel_outbound: true,
                        secp_ctx: secp_ctx,
@@ -314,6 +326,8 @@ impl Channel {
                        next_remote_htlc_id: 0,
                        channel_update_count: 0,
 
+                       last_sent_closing_fee: None,
+
                        funding_tx_confirmed_in: Default::default(),
                        short_channel_id: None,
                        last_block_connected: Default::default(),
@@ -337,52 +351,58 @@ impl Channel {
                        their_cur_commitment_point: PublicKey::new(),
                        their_node_id: their_node_id,
 
+                       their_shutdown_scriptpubkey: None,
+
                        channel_monitor: channel_monitor,
                }
        }
 
        fn check_remote_fee(fee_estimator: &FeeEstimator, feerate_per_kw: u32) -> Result<(), HandleError> {
                if (feerate_per_kw as u64) < fee_estimator.get_est_sat_per_vbyte(ConfirmationTarget::Background) * 250 {
-                       return Err(HandleError{err: "Peer's feerate much too low", msg: None});
+                       return Err(HandleError{err: "Peer's feerate much too low", msg: Some(msgs::ErrorAction::DisconnectPeer{})});
                }
                if (feerate_per_kw as u64) > fee_estimator.get_est_sat_per_vbyte(ConfirmationTarget::HighPriority) * 375 { // 375 = 250 * 1.5x
-                       return Err(HandleError{err: "Peer's feerate much too high", msg: None});
+                       return Err(HandleError{err: "Peer's feerate much too high", msg: Some(msgs::ErrorAction::DisconnectPeer{})});
                }
                Ok(())
        }
 
        /// Creates a new channel from a remote sides' request for one.
        /// Assumes chain_hash has already been checked and corresponds with what we expect!
+       /// Generally prefers to take the DisconnectPeer action on failure, as a notice to the sender
+       /// that we're rejecting the new channel.
        pub fn new_from_req(fee_estimator: &FeeEstimator, 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) {
-                       return Err(HandleError{err: "funding value > 2^24", msg: None});
+                       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: None});
+                       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: None});
+                       return Err(HandleError{err: "Bogus channel_reserve_satoshis", msg: Some(msgs::ErrorAction::DisconnectPeer{})});
                }
                if msg.push_msat > (msg.funding_satoshis - msg.channel_reserve_satoshis) * 1000 {
-                       return Err(HandleError{err: "push_msat more than highest possible value", msg: None});
+                       return Err(HandleError{err: "push_msat more than highest possible value", msg: Some(msgs::ErrorAction::DisconnectPeer{})});
+               }
+               if msg.dust_limit_satoshis > msg.funding_satoshis {
+                       return Err(HandleError{err: "Peer never wants payout outputs?", msg: Some(msgs::ErrorAction::DisconnectPeer{})});
                }
-               //TODO Check if dust_limit is sane?
                if msg.max_htlc_value_in_flight_msat > msg.funding_satoshis * 1000 {
-                       return Err(HandleError{err: "Bogus max_htlc_value_in_flight_satoshis", msg: None});
+                       return Err(HandleError{err: "Bogus max_htlc_value_in_flight_satoshis", msg: Some(msgs::ErrorAction::DisconnectPeer{})});
                }
                if msg.htlc_minimum_msat >= (msg.funding_satoshis - msg.channel_reserve_satoshis) * 1000 {
-                       return Err(HandleError{err: "Minimum htlc value is full channel value", msg: None});
+                       return Err(HandleError{err: "Minimum htlc value is full channel value", msg: Some(msgs::ErrorAction::DisconnectPeer{})});
                }
-               Channel::check_remote_fee(fee_estimator, msg.feerate_per_kw).unwrap();
+               Channel::check_remote_fee(fee_estimator, msg.feerate_per_kw)?;
                if msg.to_self_delay > MAX_LOCAL_BREAKDOWN_TIMEOUT {
-                       return Err(HandleError{err: "They wanted our payments to be delayed by a needlessly long period", msg: None});
+                       return Err(HandleError{err: "They wanted our payments to be delayed by a needlessly long period", msg: Some(msgs::ErrorAction::DisconnectPeer{})});
                }
                if msg.max_accepted_htlcs < 1 {
-                       return Err(HandleError{err: "0 max_accpted_htlcs makes for a useless channel", msg: None});
+                       return Err(HandleError{err: "0 max_accpted_htlcs makes for a useless channel", msg: Some(msgs::ErrorAction::DisconnectPeer{})});
                }
                if (msg.channel_flags & 254) != 0 {
-                       return Err(HandleError{err: "unknown channel_flags", msg: None});
+                       return Err(HandleError{err: "unknown channel_flags", msg: Some(msgs::ErrorAction::DisconnectPeer{})});
                }
 
                // Convert things into internal flags and prep our state:
@@ -391,9 +411,8 @@ impl Channel {
 
                let background_feerate = fee_estimator.get_est_sat_per_vbyte(ConfirmationTarget::Background);
 
-               let mut rng = thread_rng();
                let mut key_seed = [0u8; 32];
-               rng.fill_bytes(&mut key_seed);
+               rng::fill_bytes(&mut key_seed);
                let chan_keys = match ChannelKeys::new_from_seed(&key_seed) {
                        Ok(key) => key,
                        Err(_) => panic!("RNG is busted!")
@@ -427,6 +446,8 @@ impl Channel {
                        next_remote_htlc_id: 0,
                        channel_update_count: 0,
 
+                       last_sent_closing_fee: None,
+
                        funding_tx_confirmed_in: Default::default(),
                        short_channel_id: None,
                        last_block_connected: Default::default(),
@@ -451,6 +472,8 @@ impl Channel {
                        their_cur_commitment_point: msg.first_per_commitment_point,
                        their_node_id: their_node_id,
 
+                       their_shutdown_scriptpubkey: None,
+
                        channel_monitor: channel_monitor,
                };
 
@@ -462,9 +485,9 @@ impl Channel {
 
        // Utilities to derive keys:
 
-       fn build_local_commitment_secret(&self, idx: u64) -> Result<SecretKey, HandleError> {
+       fn build_local_commitment_secret(&self, idx: u64) -> SecretKey {
                let res = chan_utils::build_commitment_secret(self.local_keys.commitment_seed, idx);
-               Ok(get_key!(&self.secp_ctx, &res))
+               SecretKey::from_slice(&self.secp_ctx, &res).unwrap()
        }
 
        // Utilities to build transactions:
@@ -505,7 +528,7 @@ impl Channel {
        /// generated by the peer which proposed adding the HTLCs, and thus we need to understand both
        /// which peer generated this transaction and "to whom" this transaction flows.
        #[inline]
-       fn build_commitment_transaction(&self, commitment_number: u64, keys: &TxCreationKeys, local: bool, generated_by_local: bool) -> Result<(Transaction, Vec<HTLCOutputInCommitment>), HandleError> {
+       fn build_commitment_transaction(&self, commitment_number: u64, keys: &TxCreationKeys, local: bool, generated_by_local: bool) -> (Transaction, Vec<HTLCOutputInCommitment>) {
                let obscured_commitment_transaction_number = self.get_commitment_transaction_number_obscure_factor() ^ commitment_number;
 
                let txins = {
@@ -514,12 +537,11 @@ impl Channel {
                                prev_hash: self.channel_monitor.get_funding_txo().unwrap().0,
                                prev_index: self.channel_monitor.get_funding_txo().unwrap().1 as u32,
                                script_sig: Script::new(),
-                               sequence: ((0x80 as u32) << 8*3) | ((obscured_commitment_transaction_number >> 3*8) as u32)
+                               sequence: ((0x80 as u32) << 8*3) | ((obscured_commitment_transaction_number >> 3*8) as u32),
+                               witness: Vec::new(),
                        });
                        ins
                };
-               let mut witness: Vec<Vec<Vec<u8>>> = Vec::new();
-               witness.push(Vec::new());
 
                let mut txouts: Vec<(TxOut, Option<HTLCOutputInCommitment>)> = Vec::new();
 
@@ -594,13 +616,81 @@ impl Channel {
                        }
                }
 
-               Ok((Transaction {
+               (Transaction {
                        version: 2,
                        lock_time: ((0x20 as u32) << 8*3) | ((obscured_commitment_transaction_number & 0xffffffu64) as u32),
                        input: txins,
                        output: outputs,
-                       witness: witness
-               }, htlcs_used))
+               }, htlcs_used)
+       }
+
+       #[inline]
+       fn get_closing_scriptpubkey(&self) -> Script {
+               let our_channel_close_key_hash = Hash160::from_data(&PublicKey::from_secret_key(&self.secp_ctx, &self.local_keys.channel_close_key).unwrap().serialize());
+               Builder::new().push_opcode(opcodes::All::OP_PUSHBYTES_0).push_slice(&our_channel_close_key_hash[..]).into_script()
+       }
+
+       #[inline]
+       fn get_closing_transaction_weight(a_scriptpubkey: &Script, b_scriptpubkey: &Script) -> u64 {
+               (4 + 1 + 36 + 4 + 1 + 1 + 2*(8+1) + 4 + a_scriptpubkey.len() as u64 + b_scriptpubkey.len() as u64)*4 + 2 + 1 + 1 + 2*(1 + 72)
+       }
+
+       #[inline]
+       fn build_closing_transaction(&self, proposed_total_fee_satoshis: u64, skip_remote_output: bool) -> (Transaction, u64) {
+               let txins = {
+                       let mut ins: Vec<TxIn> = Vec::new();
+                       ins.push(TxIn {
+                               prev_hash: self.channel_monitor.get_funding_txo().unwrap().0,
+                               prev_index: self.channel_monitor.get_funding_txo().unwrap().1 as u32,
+                               script_sig: Script::new(),
+                               sequence: 0xffffffff,
+                               witness: Vec::new(),
+                       });
+                       ins
+               };
+
+               assert!(self.pending_htlcs.is_empty());
+               let mut txouts: Vec<(TxOut, ())> = Vec::new();
+
+               let mut total_fee_satoshis = proposed_total_fee_satoshis;
+               let value_to_self: i64 = (self.value_to_self_msat as i64) / 1000 - if self.channel_outbound { total_fee_satoshis as i64 } else { 0 };
+               let value_to_remote: i64 = ((self.channel_value_satoshis * 1000 - self.value_to_self_msat) as i64 / 1000) - if self.channel_outbound { 0 } else { total_fee_satoshis as i64 };
+
+               if value_to_self < 0 {
+                       assert!(self.channel_outbound);
+                       total_fee_satoshis += (-value_to_self) as u64;
+               } else if value_to_remote < 0 {
+                       assert!(!self.channel_outbound);
+                       total_fee_satoshis += (-value_to_remote) as u64;
+               }
+
+               if !skip_remote_output && value_to_remote as u64 > self.our_dust_limit_satoshis {
+                       txouts.push((TxOut {
+                               script_pubkey: self.their_shutdown_scriptpubkey.clone().unwrap(),
+                               value: value_to_remote as u64
+                       }, ()));
+               }
+
+               if value_to_self as u64 > self.our_dust_limit_satoshis {
+                       txouts.push((TxOut {
+                               script_pubkey: self.get_closing_scriptpubkey(),
+                               value: value_to_self as u64
+                       }, ()));
+               }
+
+               transaction_utils::sort_outputs(&mut txouts);
+
+               let mut outputs: Vec<TxOut> = Vec::new();
+               for out in txouts.drain(..) {
+                       outputs.push(out.0);
+               }
+
+               (Transaction {
+                       version: 2,
+                       lock_time: 0,
+                       input: txins,
+                       output: outputs,
+               }, total_fee_satoshis)
        }
 
        #[inline]
@@ -610,11 +700,11 @@ impl Channel {
        /// The result is a transaction which we can revoke ownership of (ie a "local" transaction)
        /// TODO Some magic rust shit to compile-time check this?
        fn build_local_transaction_keys(&self, commitment_number: u64) -> Result<TxCreationKeys, HandleError> {
-               let per_commitment_point = PublicKey::from_secret_key(&self.secp_ctx, &try!(self.build_local_commitment_secret(commitment_number))).unwrap();
+               let per_commitment_point = PublicKey::from_secret_key(&self.secp_ctx, &self.build_local_commitment_secret(commitment_number)).unwrap();
                let delayed_payment_base = PublicKey::from_secret_key(&self.secp_ctx, &self.local_keys.delayed_payment_base_key).unwrap();
                let htlc_basepoint = PublicKey::from_secret_key(&self.secp_ctx, &self.local_keys.htlc_base_key).unwrap();
 
-               Ok(secp_call!(TxCreationKeys::new(&self.secp_ctx, &per_commitment_point, &delayed_payment_base, &htlc_basepoint, &self.their_revocation_basepoint, &self.their_payment_basepoint, &self.their_htlc_basepoint)))
+               Ok(secp_derived_key!(TxCreationKeys::new(&self.secp_ctx, &per_commitment_point, &delayed_payment_base, &htlc_basepoint, &self.their_revocation_basepoint, &self.their_payment_basepoint, &self.their_htlc_basepoint)))
        }
 
        #[inline]
@@ -627,7 +717,7 @@ impl Channel {
                let revocation_basepoint = PublicKey::from_secret_key(&self.secp_ctx, &self.local_keys.revocation_base_key).unwrap();
                let htlc_basepoint = PublicKey::from_secret_key(&self.secp_ctx, &self.local_keys.htlc_base_key).unwrap();
 
-               Ok(secp_call!(TxCreationKeys::new(&self.secp_ctx, &self.their_cur_commitment_point, &self.their_delayed_payment_basepoint, &self.their_htlc_basepoint, &revocation_basepoint, &payment_basepoint, &htlc_basepoint)))
+               Ok(secp_derived_key!(TxCreationKeys::new(&self.secp_ctx, &self.their_cur_commitment_point, &self.their_delayed_payment_basepoint, &self.their_htlc_basepoint, &revocation_basepoint, &payment_basepoint, &htlc_basepoint)))
        }
 
        /// Gets the redeemscript for the funding transaction output (ie the funding transaction output
@@ -645,36 +735,36 @@ impl Channel {
                }.push_opcode(opcodes::All::OP_PUSHNUM_2).push_opcode(opcodes::All::OP_CHECKMULTISIG).into_script()
        }
 
-       fn sign_commitment_transaction(&self, tx: &mut Transaction, their_sig: &Signature) -> Result<(), HandleError> {
+       fn sign_commitment_transaction(&self, tx: &mut Transaction, their_sig: &Signature) -> Signature {
                if tx.input.len() != 1 {
                        panic!("Tried to sign commitment transaction that had input count != 1!");
                }
-               if tx.witness.len() != 1 || tx.witness[0].len() != 0 {
+               if tx.input[0].witness.len() != 0 {
                        panic!("Tried to re-sign commitment transaction");
                }
 
                let funding_redeemscript = self.get_funding_redeemscript();
 
-               let sighash = secp_call!(Message::from_slice(&bip143::SighashComponents::new(&tx).sighash_all(&tx, 0, &funding_redeemscript, self.channel_value_satoshis)[..]));
-               let our_sig = secp_call!(self.secp_ctx.sign(&sighash, &self.local_keys.funding_key));
+               let sighash = Message::from_slice(&bip143::SighashComponents::new(&tx).sighash_all(&tx.input[0], &funding_redeemscript, self.channel_value_satoshis)[..]).unwrap();
+               let our_sig = self.secp_ctx.sign(&sighash, &self.local_keys.funding_key).unwrap();
 
-               tx.witness[0].push(Vec::new()); // First is the multisig dummy
+               tx.input[0].witness.push(Vec::new()); // First is the multisig dummy
 
                let our_funding_key = PublicKey::from_secret_key(&self.secp_ctx, &self.local_keys.funding_key).unwrap().serialize();
                let their_funding_key = self.their_funding_pubkey.serialize();
                if our_funding_key[..] < their_funding_key[..] {
-                       tx.witness[0].push(our_sig.serialize_der(&self.secp_ctx).to_vec());
-                       tx.witness[0].push(their_sig.serialize_der(&self.secp_ctx).to_vec());
+                       tx.input[0].witness.push(our_sig.serialize_der(&self.secp_ctx).to_vec());
+                       tx.input[0].witness.push(their_sig.serialize_der(&self.secp_ctx).to_vec());
                } else {
-                       tx.witness[0].push(their_sig.serialize_der(&self.secp_ctx).to_vec());
-                       tx.witness[0].push(our_sig.serialize_der(&self.secp_ctx).to_vec());
+                       tx.input[0].witness.push(their_sig.serialize_der(&self.secp_ctx).to_vec());
+                       tx.input[0].witness.push(our_sig.serialize_der(&self.secp_ctx).to_vec());
                }
-               tx.witness[0][1].push(SigHashType::All as u8);
-               tx.witness[0][2].push(SigHashType::All as u8);
+               tx.input[0].witness[1].push(SigHashType::All as u8);
+               tx.input[0].witness[2].push(SigHashType::All as u8);
 
-               tx.witness[0].push(funding_redeemscript.into_vec());
+               tx.input[0].witness.push(funding_redeemscript.into_vec());
 
-               Ok(())
+               our_sig
        }
 
        /// Builds the htlc-success or htlc-timeout transaction which spends a given HTLC output
@@ -686,12 +776,10 @@ impl Channel {
                        prev_hash: prev_hash.clone(),
                        prev_index: htlc.transaction_output_index,
                        script_sig: Script::new(),
-                       sequence: 0
+                       sequence: 0,
+                       witness: Vec::new(),
                });
 
-               let mut witnesses: Vec<Vec<Vec<u8>>> = Vec::new();
-               witnesses.push(Vec::new());
-
                let total_fee = if htlc.offered {
                                self.feerate_per_kw * HTLC_TIMEOUT_TX_WEIGHT / 1000
                        } else {
@@ -711,7 +799,6 @@ impl Channel {
                        lock_time: if htlc.offered { htlc.cltv_expiry } else { 0 },
                        input: txins,
                        output: txouts,
-                       witness: witnesses
                })
        }
 
@@ -721,45 +808,50 @@ impl Channel {
                if tx.input.len() != 1 {
                        panic!("Tried to sign HTLC transaction that had input count != 1!");
                }
-               if tx.witness.len() != 1 || tx.witness[0].len() != 0 {
+               if tx.input[0].witness.len() != 0 {
                        panic!("Tried to re-sign HTLC transaction");
                }
 
                let htlc_redeemscript = chan_utils::get_htlc_redeemscript(&htlc, &keys, htlc.offered);
 
-               let our_htlc_key = secp_call!(chan_utils::derive_private_key(&self.secp_ctx, &keys.per_commitment_point, &self.local_keys.htlc_base_key));
-               let sighash = secp_call!(Message::from_slice(&bip143::SighashComponents::new(&tx).sighash_all(&tx, 0, &htlc_redeemscript, htlc.amount_msat / 1000)[..]));
-               let our_sig = secp_call!(self.secp_ctx.sign(&sighash, &our_htlc_key));
+               let our_htlc_key = secp_derived_key!(chan_utils::derive_private_key(&self.secp_ctx, &keys.per_commitment_point, &self.local_keys.htlc_base_key));
+               let sighash = Message::from_slice(&bip143::SighashComponents::new(&tx).sighash_all(&tx.input[0], &htlc_redeemscript, htlc.amount_msat / 1000)[..]).unwrap();
+               let our_sig = self.secp_ctx.sign(&sighash, &our_htlc_key).unwrap();
 
                let local_tx = PublicKey::from_secret_key(&self.secp_ctx, &our_htlc_key).unwrap() == keys.a_htlc_key;
 
-               tx.witness[0].push(Vec::new()); // First is the multisig dummy
+               tx.input[0].witness.push(Vec::new()); // First is the multisig dummy
 
                if local_tx { // b, then a
-                       tx.witness[0].push(their_sig.serialize_der(&self.secp_ctx).to_vec());
-                       tx.witness[0].push(our_sig.serialize_der(&self.secp_ctx).to_vec());
+                       tx.input[0].witness.push(their_sig.serialize_der(&self.secp_ctx).to_vec());
+                       tx.input[0].witness.push(our_sig.serialize_der(&self.secp_ctx).to_vec());
                } else {
-                       tx.witness[0].push(our_sig.serialize_der(&self.secp_ctx).to_vec());
-                       tx.witness[0].push(their_sig.serialize_der(&self.secp_ctx).to_vec());
+                       tx.input[0].witness.push(our_sig.serialize_der(&self.secp_ctx).to_vec());
+                       tx.input[0].witness.push(their_sig.serialize_der(&self.secp_ctx).to_vec());
                }
-               tx.witness[0][1].push(SigHashType::All as u8);
-               tx.witness[0][2].push(SigHashType::All as u8);
+               tx.input[0].witness[1].push(SigHashType::All as u8);
+               tx.input[0].witness[2].push(SigHashType::All as u8);
 
                if htlc.offered {
-                       tx.witness[0].push(Vec::new());
+                       tx.input[0].witness.push(Vec::new());
                } else {
-                       tx.witness[0].push(preimage.unwrap().to_vec());
+                       tx.input[0].witness.push(preimage.unwrap().to_vec());
                }
 
-               tx.witness[0].push(htlc_redeemscript.into_vec());
+               tx.input[0].witness.push(htlc_redeemscript.into_vec());
 
                Ok(())
        }
 
        pub fn get_update_fulfill_htlc(&mut self, payment_preimage: [u8; 32]) -> Result<msgs::UpdateFulfillHTLC, HandleError> {
+               // Either ChannelFunded got set (which means it wont bet unset) or there is no way any
+               // caller thought we could have something claimed (cause we wouldn't have accepted in an
+               // incoming HTLC anyway). If we got to ShutdownComplete, callers aren't allowed to call us,
+               // either.
                if (self.channel_state & (ChannelState::ChannelFunded as u32)) != (ChannelState::ChannelFunded as u32) {
-                       return Err(HandleError{err: "Was asked to fulfill an HTLC when channel was not in an operational state", msg: None});
+                       panic!("Was asked to fulfill an HTLC when channel was not in an operational state");
                }
+               assert_eq!(self.channel_state & ChannelState::ShutdownComplete as u32, 0);
 
                let mut sha = Sha256::new();
                sha.input(&payment_preimage);
@@ -768,6 +860,7 @@ impl Channel {
 
                let mut htlc_id = 0;
                let mut htlc_amount_msat = 0;
+               //TODO: swap_remove since we dont need to maintain ordering here
                self.pending_htlcs.retain(|ref htlc| {
                        if !htlc.outbound && htlc.payment_hash == payment_hash {
                                if htlc_id != 0 {
@@ -782,8 +875,9 @@ impl Channel {
                        return Err(HandleError{err: "Unable to find a pending HTLC which matched the given payment preimage", msg: None});
                }
 
+               //TODO: This is racy af, they may have pending messages in flight to us that will not have
+               //received this yet!
                self.value_to_self_msat += htlc_amount_msat;
-
                Ok(msgs::UpdateFulfillHTLC {
                        channel_id: self.channel_id(),
                        htlc_id: htlc_id,
@@ -791,17 +885,52 @@ impl Channel {
                })
        }
 
+       pub fn get_update_fail_htlc(&mut self, payment_hash: &[u8; 32], err_packet: msgs::OnionErrorPacket) -> Result<msgs::UpdateFailHTLC, HandleError> {
+               if (self.channel_state & (ChannelState::ChannelFunded as u32)) != (ChannelState::ChannelFunded as u32) {
+                       return Err(HandleError{err: "Was asked to fail an HTLC when channel was not in an operational state", msg: None});
+               }
+               assert_eq!(self.channel_state & ChannelState::ShutdownComplete as u32, 0);
+
+               let mut htlc_id = 0;
+               let mut htlc_amount_msat = 0;
+               //TODO: swap_remove since we dont need to maintain ordering here
+               self.pending_htlcs.retain(|ref htlc| {
+                       if !htlc.outbound && htlc.payment_hash == *payment_hash {
+                               if htlc_id != 0 {
+                                       panic!("Duplicate HTLC payment_hash, you probably re-used payment preimages, NEVER DO THIS!");
+                               }
+                               htlc_id = htlc.htlc_id;
+                               htlc_amount_msat += htlc.amount_msat;
+                               false
+                       } else { true }
+               });
+               if htlc_amount_msat == 0 {
+                       return Err(HandleError{err: "Unable to find a pending HTLC which matched the given payment preimage", msg: None});
+               }
+
+               //TODO: This is racy af, they may have pending messages in flight to us that will not have
+               //received this yet!
+
+               Ok(msgs::UpdateFailHTLC {
+                       channel_id: self.channel_id(),
+                       htlc_id,
+                       reason: err_packet
+               })
+       }
+
        // Message handlers:
 
        pub fn accept_channel(&mut self, msg: &msgs::AcceptChannel) -> Result<(), HandleError> {
                // Check sanity of message fields:
-               //TODO Check if dust_limit is sane?
                if !self.channel_outbound {
                        return Err(HandleError{err: "Got an accept_channel message from an inbound peer", msg: None});
                }
                if self.channel_state != ChannelState::OurInitSent as u32 {
                        return Err(HandleError{err: "Got an accept_channel message at a strange time", msg: None});
                }
+               if msg.dust_limit_satoshis > 21000000 * 100000000 {
+                       return Err(HandleError{err: "Peer never wants payout outputs?", msg: None});
+               }
                if msg.max_htlc_value_in_flight_msat > self.channel_value_satoshis * 1000 {
                        return Err(HandleError{err: "Bogus max_htlc_value_in_flight_satoshis", msg: None});
                }
@@ -845,19 +974,19 @@ impl Channel {
        fn funding_created_signature(&mut self, sig: &Signature) -> Result<(Transaction, Signature), HandleError> {
                let funding_script = self.get_funding_redeemscript();
 
-               let remote_keys = try!(self.build_remote_transaction_keys());
-               let remote_initial_commitment_tx = try!(self.build_commitment_transaction(self.cur_remote_commitment_transaction_number, &remote_keys, false, false)).0;
-               let remote_sighash = secp_call!(Message::from_slice(&bip143::SighashComponents::new(&remote_initial_commitment_tx).sighash_all(&remote_initial_commitment_tx, 0, &funding_script, self.channel_value_satoshis)[..]));
+               let remote_keys = self.build_remote_transaction_keys()?;
+               let remote_initial_commitment_tx = self.build_commitment_transaction(self.cur_remote_commitment_transaction_number, &remote_keys, false, false).0;
+               let remote_sighash = Message::from_slice(&bip143::SighashComponents::new(&remote_initial_commitment_tx).sighash_all(&remote_initial_commitment_tx.input[0], &funding_script, self.channel_value_satoshis)[..]).unwrap();
 
-               let local_keys = try!(self.build_local_transaction_keys(self.cur_local_commitment_transaction_number));
-               let local_initial_commitment_tx = try!(self.build_commitment_transaction(self.cur_local_commitment_transaction_number, &local_keys, true, false)).0;
-               let local_sighash = secp_call!(Message::from_slice(&bip143::SighashComponents::new(&local_initial_commitment_tx).sighash_all(&local_initial_commitment_tx, 0, &funding_script, self.channel_value_satoshis)[..]));
+               let local_keys = self.build_local_transaction_keys(self.cur_local_commitment_transaction_number)?;
+               let local_initial_commitment_tx = self.build_commitment_transaction(self.cur_local_commitment_transaction_number, &local_keys, true, false).0;
+               let local_sighash = Message::from_slice(&bip143::SighashComponents::new(&local_initial_commitment_tx).sighash_all(&local_initial_commitment_tx.input[0], &funding_script, self.channel_value_satoshis)[..]).unwrap();
 
                // They sign the "local" commitment transaction, allowing us to broadcast the tx if we wish.
-               secp_call!(self.secp_ctx.verify(&local_sighash, &sig, &self.their_funding_pubkey));
+               secp_call!(self.secp_ctx.verify(&local_sighash, &sig, &self.their_funding_pubkey), "Invalid funding_created signature from peer");
 
                // We sign the "remote" commitment transaction, allowing them to broadcast the tx if they wish.
-               Ok((remote_initial_commitment_tx, secp_call!(self.secp_ctx.sign(&remote_sighash, &self.local_keys.funding_key))))
+               Ok((remote_initial_commitment_tx, self.secp_ctx.sign(&remote_sighash, &self.local_keys.funding_key).unwrap()))
        }
 
        pub fn funding_created(&mut self, msg: &msgs::FundingCreated) -> Result<msgs::FundingSigned, HandleError> {
@@ -911,12 +1040,12 @@ impl Channel {
 
                let funding_script = self.get_funding_redeemscript();
 
-               let local_keys = try!(self.build_local_transaction_keys(self.cur_local_commitment_transaction_number));
-               let local_initial_commitment_tx = try!(self.build_commitment_transaction(self.cur_local_commitment_transaction_number, &local_keys, true, false)).0;
-               let local_sighash = secp_call!(Message::from_slice(&bip143::SighashComponents::new(&local_initial_commitment_tx).sighash_all(&local_initial_commitment_tx, 0, &funding_script, self.channel_value_satoshis)[..]));
+               let local_keys = self.build_local_transaction_keys(self.cur_local_commitment_transaction_number)?;
+               let local_initial_commitment_tx = self.build_commitment_transaction(self.cur_local_commitment_transaction_number, &local_keys, true, false).0;
+               let local_sighash = Message::from_slice(&bip143::SighashComponents::new(&local_initial_commitment_tx).sighash_all(&local_initial_commitment_tx.input[0], &funding_script, self.channel_value_satoshis)[..]).unwrap();
 
                // They sign the "local" commitment transaction, allowing us to broadcast the tx if we wish.
-               secp_call!(self.secp_ctx.verify(&local_sighash, &msg.signature, &self.their_funding_pubkey));
+               secp_call!(self.secp_ctx.verify(&local_sighash, &msg.signature, &self.their_funding_pubkey), "Invalid funding_signed signature from peer");
 
                self.channel_state = ChannelState::FundingSent as u32;
 
@@ -924,12 +1053,13 @@ impl Channel {
        }
 
        pub fn funding_locked(&mut self, msg: &msgs::FundingLocked) -> Result<(), HandleError> {
-               if self.channel_state == ChannelState::FundingSent as u32 {
+               let non_shutdown_state = self.channel_state & (!BOTH_SIDES_SHUTDOWN_MASK);
+               if non_shutdown_state == ChannelState::FundingSent as u32 {
                        self.channel_state |= ChannelState::TheirFundingLocked as u32;
-               } else if self.channel_state == (ChannelState::FundingSent as u32 | ChannelState::OurFundingLocked as u32) {
-                       self.channel_state = ChannelState::ChannelFunded as u32;
-               } else if self.channel_state < ChannelState::FundingSent as u32 {
-                       return Err(HandleError{err: "Peer sent a funding_locked before we'd even been told the funding txid", msg: None});
+               } else if non_shutdown_state == (ChannelState::FundingSent as u32 | ChannelState::OurFundingLocked as u32) {
+                       self.channel_state = ChannelState::ChannelFunded as u32 | (self.channel_state & BOTH_SIDES_SHUTDOWN_MASK);
+               } else {
+                       return Err(HandleError{err: "Peer sent a funding_locked at a strange time", msg: None});
                }
 
                //TODO: Note that this must be a duplicate of the previous commitment point they sent us,
@@ -962,7 +1092,7 @@ impl Channel {
        }
 
        pub fn update_add_htlc(&mut self, msg: &msgs::UpdateAddHTLC, pending_forward_state: PendingForwardHTLCInfo) -> Result<(), HandleError> {
-               if (self.channel_state & (ChannelState::ChannelFunded as u32)) != (ChannelState::ChannelFunded as u32) {
+               if (self.channel_state & (ChannelState::ChannelFunded as u32 | ChannelState::RemoteShutdownSent as u32)) != (ChannelState::ChannelFunded as u32) {
                        return Err(HandleError{err: "Got add HTLC message when channel was not in an operational state", msg: None});
                }
                if msg.amount_msat > self.channel_value_satoshis * 1000 {
@@ -981,8 +1111,10 @@ impl Channel {
                if htlc_inbound_value_msat + msg.amount_msat > Channel::get_our_max_htlc_value_in_flight_msat(self.channel_value_satoshis) {
                        return Err(HandleError{err: "Remote HTLC add would put them over their max HTLC value in flight", msg: None});
                }
-               // Check our_channel_reserve_satoshis:
-               if htlc_inbound_value_msat + htlc_outbound_value_msat + msg.amount_msat > (self.channel_value_satoshis - Channel::get_our_channel_reserve_satoshis(self.channel_value_satoshis)) * 1000 {
+               // Check our_channel_reserve_satoshis (we're getting paid, so they have to at least meet
+               // the reserve_satoshis we told them to always have as direct payment so that they lose
+               // something if we punish them for broadcasting an old state).
+               if htlc_inbound_value_msat + htlc_outbound_value_msat + msg.amount_msat + self.value_to_self_msat > (self.channel_value_satoshis - Channel::get_our_channel_reserve_satoshis(self.channel_value_satoshis)) * 1000 {
                        return Err(HandleError{err: "Remote HTLC add would put them over their reserve value", msg: None});
                }
                if self.next_remote_htlc_id != msg.htlc_id {
@@ -1010,7 +1142,7 @@ impl Channel {
        }
 
        /// Removes an outbound HTLC which has been commitment_signed by the remote end
-       fn remove_htlc(&mut self, htlc_id: u64, check_preimage: Option<[u8; 32]>) -> Result<HTLCOutput, HandleError> {
+       fn remove_outbound_htlc(&mut self, htlc_id: u64, check_preimage: Option<[u8; 32]>) -> Result<HTLCOutput, HandleError> {
                let mut found_idx = None;
                for (idx, ref htlc) in self.pending_htlcs.iter().enumerate() {
                        if htlc.outbound && htlc.htlc_id == htlc_id {
@@ -1026,7 +1158,7 @@ impl Channel {
                        }
                }
                match found_idx {
-                       None => Err(HandleError{err: "Remote tried to fulfill an HTLC we couldn't find", msg: None}),
+                       None => Err(HandleError{err: "Remote tried to fulfill/fail an HTLC we couldn't find", msg: None}),
                        Some(idx) => {
                                Ok(self.pending_htlcs.swap_remove(idx))
                        }
@@ -1061,7 +1193,7 @@ impl Channel {
                        //TODO: Need to examine the type of err - if its a fee issue or similar we may want to
                        //fail it back the route, if its a temporary issue we can ignore it...
                        if update_add_msgs.len() > 0 {
-                               Ok(Some((update_add_msgs, try!(self.send_commitment()))))
+                               Ok(Some((update_add_msgs, self.send_commitment()?)))
                        } else {
                                Err(err.unwrap())
                        }
@@ -1070,23 +1202,7 @@ impl Channel {
                }
        }
 
-       /// Checks if there are any LocalAnnounced HTLCs remaining and sets
-       /// ChannelState::AwaitingRemoteRevoke accordingly, possibly calling free_holding_cell_htlcs.
-       fn check_and_free_holding_cell_htlcs(&mut self) -> Result<Option<(Vec<msgs::UpdateAddHTLC>, msgs::CommitmentSigned)>, HandleError> {
-               if (self.channel_state & (ChannelState::AwaitingRemoteRevoke as u32)) == (ChannelState::AwaitingRemoteRevoke as u32) {
-                       for htlc in self.pending_htlcs.iter() {
-                               if htlc.state == HTLCState::LocalAnnounced {
-                                       return Ok(None);
-                               }
-                       }
-                       self.channel_state &= !(ChannelState::AwaitingRemoteRevoke as u32);
-                       self.free_holding_cell_htlcs()
-               } else {
-                       Ok(None)
-               }
-       }
-
-       pub fn update_fulfill_htlc(&mut self, msg: &msgs::UpdateFulfillHTLC) -> Result<Option<(Vec<msgs::UpdateAddHTLC>, msgs::CommitmentSigned)>, HandleError> {
+       pub fn update_fulfill_htlc(&mut self, msg: &msgs::UpdateFulfillHTLC) -> Result<(), HandleError> {
                if (self.channel_state & (ChannelState::ChannelFunded as u32)) != (ChannelState::ChannelFunded as u32) {
                        return Err(HandleError{err: "Got add HTLC message when channel was not in an operational state", msg: None});
                }
@@ -1096,9 +1212,7 @@ impl Channel {
                let mut payment_hash = [0; 32];
                sha.result(&mut payment_hash);
 
-               //TODO: Tell channel_monitor about the payment_preimage
-
-               match self.remove_htlc(msg.htlc_id, Some(payment_hash)) {
+               match self.remove_outbound_htlc(msg.htlc_id, Some(payment_hash)) {
                        Err(e) => return Err(e),
                        Ok(htlc) => {
                                //TODO: Double-check that we didn't exceed some limits (or value_to_self went
@@ -1106,47 +1220,39 @@ impl Channel {
                                self.value_to_self_msat -= htlc.amount_msat;
                        }
                }
-
-               self.check_and_free_holding_cell_htlcs()
+               Ok(())
        }
 
-
-       pub fn update_fail_htlc(&mut self, msg: &msgs::UpdateFailHTLC) -> Result<Option<(Vec<msgs::UpdateAddHTLC>, msgs::CommitmentSigned)>, HandleError> {
+       pub fn update_fail_htlc(&mut self, msg: &msgs::UpdateFailHTLC) -> Result<[u8; 32], HandleError> {
                if (self.channel_state & (ChannelState::ChannelFunded as u32)) != (ChannelState::ChannelFunded as u32) {
                        return Err(HandleError{err: "Got add HTLC message when channel was not in an operational state", msg: None});
                }
 
-               //TODO: Lots of checks here (and implementation after the remove?)
-
-               match self.remove_htlc(msg.htlc_id, None) {
+               let payment_hash = match self.remove_outbound_htlc(msg.htlc_id, None) {
                        Err(e) => return Err(e),
-                       Ok(_htlc) => {
+                       Ok(htlc) => {
                                //TODO: Double-check that we didn't exceed some limits (or value_to_self went
                                //negative here?)
-                               ////TODO: Something?
+                               htlc.payment_hash
                        }
-               }
-
-               self.check_and_free_holding_cell_htlcs()
+               };
+               Ok(payment_hash)
        }
 
-       pub fn update_fail_malformed_htlc(&mut self, msg: &msgs::UpdateFailMalformedHTLC) -> Result<Option<(Vec<msgs::UpdateAddHTLC>, msgs::CommitmentSigned)>, HandleError> {
+       pub fn update_fail_malformed_htlc(&mut self, msg: &msgs::UpdateFailMalformedHTLC) -> Result<[u8; 32], HandleError> {
                if (self.channel_state & (ChannelState::ChannelFunded as u32)) != (ChannelState::ChannelFunded as u32) {
                        return Err(HandleError{err: "Got add HTLC message when channel was not in an operational state", msg: None});
                }
 
-               //TODO: Lots of checks here (and implementation after the remove?)
-
-               match self.remove_htlc(msg.htlc_id, None) {
+               let payment_hash = match self.remove_outbound_htlc(msg.htlc_id, None) {
                        Err(e) => return Err(e),
-                       Ok(_htlc) => {
+                       Ok(htlc) => {
                                //TODO: Double-check that we didn't exceed some limits (or value_to_self went
                                //negative here?)
-                               ////TODO: Something?
+                               htlc.payment_hash
                        }
-               }
-
-               self.check_and_free_holding_cell_htlcs()
+               };
+               Ok(payment_hash)
        }
 
        pub fn commitment_signed(&mut self, msg: &msgs::CommitmentSigned) -> Result<(msgs::RevokeAndACK, Vec<PendingForwardHTLCInfo>), HandleError> {
@@ -1156,23 +1262,24 @@ impl Channel {
 
                let funding_script = self.get_funding_redeemscript();
 
-               let local_keys = try!(self.build_local_transaction_keys(self.cur_local_commitment_transaction_number));
-               let local_commitment_tx = try!(self.build_commitment_transaction(self.cur_local_commitment_transaction_number, &local_keys, true, false));
-               let local_sighash = secp_call!(Message::from_slice(&bip143::SighashComponents::new(&local_commitment_tx.0).sighash_all(&local_commitment_tx.0, 0, &funding_script, self.channel_value_satoshis)[..]));
-               secp_call!(self.secp_ctx.verify(&local_sighash, &msg.signature, &self.their_funding_pubkey));
+               let local_keys = self.build_local_transaction_keys(self.cur_local_commitment_transaction_number)?;
+               let local_commitment_tx = self.build_commitment_transaction(self.cur_local_commitment_transaction_number, &local_keys, true, false);
+               let local_commitment_txid = local_commitment_tx.0.txid();
+               let local_sighash = Message::from_slice(&bip143::SighashComponents::new(&local_commitment_tx.0).sighash_all(&local_commitment_tx.0.input[0], &funding_script, self.channel_value_satoshis)[..]).unwrap();
+               secp_call!(self.secp_ctx.verify(&local_sighash, &msg.signature, &self.their_funding_pubkey), "Invalid commitment tx signature from peer");
 
                if msg.htlc_signatures.len() != local_commitment_tx.1.len() {
                        return Err(HandleError{err: "Got wrong number of HTLC signatures from remote", msg: None});
                }
 
                for (idx, ref htlc) in local_commitment_tx.1.iter().enumerate() {
-                       let htlc_tx = try!(self.build_htlc_transaction(&local_commitment_tx.0.txid(), htlc, true, &local_keys));
+                       let htlc_tx = self.build_htlc_transaction(&local_commitment_txid, htlc, true, &local_keys)?;
                        let htlc_redeemscript = chan_utils::get_htlc_redeemscript(&htlc, &local_keys, htlc.offered);
-                       let htlc_sighash = secp_call!(Message::from_slice(&bip143::SighashComponents::new(&htlc_tx).sighash_all(&htlc_tx, 0, &htlc_redeemscript, htlc.amount_msat / 1000)[..]));
-                       secp_call!(self.secp_ctx.verify(&htlc_sighash, &msg.htlc_signatures[idx], &local_keys.b_htlc_key));
+                       let htlc_sighash = Message::from_slice(&bip143::SighashComponents::new(&htlc_tx).sighash_all(&htlc_tx.input[0], &htlc_redeemscript, htlc.amount_msat / 1000)[..]).unwrap();
+                       secp_call!(self.secp_ctx.verify(&htlc_sighash, &msg.htlc_signatures[idx], &local_keys.b_htlc_key), "Invalid HTLC tx siganture from peer");
                }
 
-               let next_per_commitment_point = PublicKey::from_secret_key(&self.secp_ctx, &try!(self.build_local_commitment_secret(self.cur_local_commitment_transaction_number - 1))).unwrap();
+               let next_per_commitment_point = PublicKey::from_secret_key(&self.secp_ctx, &self.build_local_commitment_secret(self.cur_local_commitment_transaction_number - 1)).unwrap();
                let per_commitment_secret = chan_utils::build_commitment_secret(self.local_keys.commitment_seed, self.cur_local_commitment_transaction_number);
 
                //TODO: Store htlc keys in our channel_watcher
@@ -1205,10 +1312,10 @@ impl Channel {
                if (self.channel_state & (ChannelState::ChannelFunded as u32)) != (ChannelState::ChannelFunded as u32) {
                        return Err(HandleError{err: "Got revoke/ACK message when channel was not in an operational state", msg: None});
                }
-               if PublicKey::from_secret_key(&self.secp_ctx, &get_key!(&self.secp_ctx, &msg.per_commitment_secret)).unwrap() != self.their_cur_commitment_point {
+               if PublicKey::from_secret_key(&self.secp_ctx, &secp_call!(SecretKey::from_slice(&self.secp_ctx, &msg.per_commitment_secret), "Peer provided an invalid per_commitment_secret")).unwrap() != self.their_cur_commitment_point {
                        return Err(HandleError{err: "Got a revoke commitment secret which didn't correspond to their current pubkey", msg: None});
                }
-               try!(self.channel_monitor.provide_secret(self.cur_remote_commitment_transaction_number, msg.per_commitment_secret));
+               self.channel_monitor.provide_secret(self.cur_remote_commitment_transaction_number, msg.per_commitment_secret)?;
 
                // Update state now that we've passed all the can-fail calls...
                // (note that we may still fail to generate the new commitment_signed message, but that's
@@ -1230,11 +1337,184 @@ impl Channel {
         if self.channel_outbound {
                        return Err(HandleError{err: "Non-funding remote tried to update channel fee", msg: None});
         }
-               Channel::check_remote_fee(fee_estimator, msg.feerate_per_kw).unwrap();
+               Channel::check_remote_fee(fee_estimator, msg.feerate_per_kw)?;
                self.feerate_per_kw = msg.feerate_per_kw as u64;
                Ok(())
        }
 
+       pub fn shutdown(&mut self, fee_estimator: &FeeEstimator, msg: &msgs::Shutdown) -> Result<(Option<msgs::Shutdown>, Option<msgs::ClosingSigned>, Vec<[u8; 32]>), HandleError> {
+               if self.channel_state < ChannelState::FundingSent as u32 {
+                       self.channel_state = ChannelState::ShutdownComplete as u32;
+                       return Ok((None, None, Vec::new()));
+               }
+               for htlc in self.pending_htlcs.iter() {
+                       if htlc.state == HTLCState::RemoteAnnounced {
+                               return Err(HandleError{err: "Got shutdown with remote pending HTLCs", msg: None});
+                       }
+               }
+               if (self.channel_state & ChannelState::RemoteShutdownSent as u32) == ChannelState::RemoteShutdownSent as u32 {
+                       return Err(HandleError{err: "Remote peer sent duplicate shutdown message", msg: None});
+               }
+               assert_eq!(self.channel_state & ChannelState::ShutdownComplete as u32, 0);
+
+               // BOLT 2 says we must only send a scriptpubkey of certain standard forms, which are up to
+               // 34 bytes in length, so dont let the remote peer feed us some super fee-heavy script.
+               if self.channel_outbound && msg.scriptpubkey.len() > 34 {
+                       return Err(HandleError{err: "Got shutdown_scriptpubkey of absurd length from remote peer", msg: None});
+               }
+               //TODO: Check shutdown_scriptpubkey form as BOLT says we must? WHYYY
+
+               if self.their_shutdown_scriptpubkey.is_some() {
+                       if Some(&msg.scriptpubkey) != self.their_shutdown_scriptpubkey.as_ref() {
+                               return Err(HandleError{err: "Got shutdown request with a scriptpubkey which did not match their previous scriptpubkey", msg: None});
+                       }
+               } else {
+                       self.their_shutdown_scriptpubkey = Some(msg.scriptpubkey.clone());
+               }
+
+               let our_closing_script = self.get_closing_scriptpubkey();
+
+               let (proposed_feerate, proposed_fee, our_sig) = if self.channel_outbound && self.pending_htlcs.is_empty() {
+                       let mut proposed_feerate = fee_estimator.get_est_sat_per_vbyte(ConfirmationTarget::Background);
+                       if self.feerate_per_kw > proposed_feerate * 250 {
+                               proposed_feerate = self.feerate_per_kw / 250;
+                       }
+                       let tx_weight = Self::get_closing_transaction_weight(&our_closing_script, &msg.scriptpubkey);
+                       let proposed_total_fee_satoshis = proposed_feerate * tx_weight / 4;
+
+                       let (closing_tx, total_fee_satoshis) = self.build_closing_transaction(proposed_total_fee_satoshis, false);
+                       let funding_redeemscript = self.get_funding_redeemscript();
+                       let sighash = Message::from_slice(&bip143::SighashComponents::new(&closing_tx).sighash_all(&closing_tx.input[0], &funding_redeemscript, self.channel_value_satoshis)[..]).unwrap();
+
+                       (Some(proposed_feerate), Some(total_fee_satoshis), Some(self.secp_ctx.sign(&sighash, &self.local_keys.funding_key).unwrap()))
+               } else { (None, None, None) };
+
+               // From here on out, we may not fail!
+
+               self.channel_state |= ChannelState::RemoteShutdownSent as u32;
+
+               // We can't send our shutdown until we've committed all of our pending HTLCs, but the
+               // remote side is unlikely to accept any new HTLCs, so we go ahead and "free" any holding
+               // cell HTLCs and return them to fail the payment.
+               let mut dropped_outbound_htlcs = Vec::with_capacity(self.holding_cell_htlcs.len());
+               for htlc in self.holding_cell_htlcs.drain(..) {
+                       dropped_outbound_htlcs.push(htlc.payment_hash);
+               }
+               for htlc in self.pending_htlcs.iter() {
+                       if htlc.state == HTLCState::LocalAnnounced {
+                               return Ok((None, None, dropped_outbound_htlcs));
+                       }
+               }
+
+               let our_shutdown = if (self.channel_state & ChannelState::LocalShutdownSent as u32) == ChannelState::LocalShutdownSent as u32 {
+                       None
+               } else {
+                       Some(msgs::Shutdown {
+                               channel_id: self.channel_id,
+                               scriptpubkey: our_closing_script,
+                       })
+               };
+
+               self.channel_state |= ChannelState::LocalShutdownSent as u32;
+               if self.pending_htlcs.is_empty() && self.channel_outbound {
+                       // There are no more HTLCs and we're the funder, this means we start the closing_signed
+                       // dance with an initial fee proposal!
+                       self.last_sent_closing_fee = Some((proposed_feerate.unwrap(), proposed_fee.unwrap()));
+                       Ok((our_shutdown, Some(msgs::ClosingSigned {
+                               channel_id: self.channel_id,
+                               fee_satoshis: proposed_fee.unwrap(),
+                               signature: our_sig.unwrap(),
+                       }), dropped_outbound_htlcs))
+               } else {
+                       Ok((our_shutdown, None, dropped_outbound_htlcs))
+               }
+       }
+
+       pub fn closing_signed(&mut self, fee_estimator: &FeeEstimator, msg: &msgs::ClosingSigned) -> Result<(Option<msgs::ClosingSigned>, Option<Transaction>), HandleError> {
+               if self.channel_state & BOTH_SIDES_SHUTDOWN_MASK != BOTH_SIDES_SHUTDOWN_MASK {
+                       return Err(HandleError{err: "Remote end sent us a closing_signed before both sides provided a shutdown", msg: None});
+               }
+               if !self.pending_htlcs.is_empty() {
+                       return Err(HandleError{err: "Remote end sent us a closing_signed while there were still pending HTLCs", msg: None});
+               }
+               if msg.fee_satoshis > 21000000 * 10000000 {
+                       return Err(HandleError{err: "Remote tried to send us a closing tx with > 21 million BTC fee", msg: None});
+               }
+
+               let funding_redeemscript = self.get_funding_redeemscript();
+               let (mut closing_tx, used_total_fee) = self.build_closing_transaction(msg.fee_satoshis, false);
+               if used_total_fee != msg.fee_satoshis {
+                       return Err(HandleError{err: "Remote sent us a closing_signed with a fee greater than the value they can claim", msg: None});
+               }
+               let mut sighash = Message::from_slice(&bip143::SighashComponents::new(&closing_tx).sighash_all(&closing_tx.input[0], &funding_redeemscript, self.channel_value_satoshis)[..]).unwrap();
+
+               match self.secp_ctx.verify(&sighash, &msg.signature, &self.their_funding_pubkey) {
+                       Ok(_) => {},
+                       Err(_) => {
+                               // The remote end may have decided to revoke their output due to inconsistent dust
+                               // limits, so check for that case by re-checking the signature here.
+                               closing_tx = self.build_closing_transaction(msg.fee_satoshis, true).0;
+                               sighash = Message::from_slice(&bip143::SighashComponents::new(&closing_tx).sighash_all(&closing_tx.input[0], &funding_redeemscript, self.channel_value_satoshis)[..]).unwrap();
+                               secp_call!(self.secp_ctx.verify(&sighash, &msg.signature, &self.their_funding_pubkey), "Invalid closing tx signature from peer");
+                       },
+               };
+
+               if let Some((_, last_fee)) = self.last_sent_closing_fee {
+                       if last_fee == msg.fee_satoshis {
+                               self.sign_commitment_transaction(&mut closing_tx, &msg.signature);
+                               self.channel_state = ChannelState::ShutdownComplete as u32;
+                               return Ok((None, Some(closing_tx)));
+                       }
+               }
+
+               macro_rules! propose_new_feerate {
+                       ($new_feerate: expr) => {
+                               let closing_tx_max_weight = Self::get_closing_transaction_weight(&self.get_closing_scriptpubkey(), self.their_shutdown_scriptpubkey.as_ref().unwrap());
+                               let (closing_tx, used_total_fee) = self.build_closing_transaction($new_feerate * closing_tx_max_weight / 4, false);
+                               sighash = Message::from_slice(&bip143::SighashComponents::new(&closing_tx).sighash_all(&closing_tx.input[0], &funding_redeemscript, self.channel_value_satoshis)[..]).unwrap();
+                               let our_sig = self.secp_ctx.sign(&sighash, &self.local_keys.funding_key).unwrap();
+                               self.last_sent_closing_fee = Some(($new_feerate, used_total_fee));
+                               return Ok((Some(msgs::ClosingSigned {
+                                       channel_id: self.channel_id,
+                                       fee_satoshis: used_total_fee,
+                                       signature: our_sig,
+                               }), None))
+                       }
+               }
+
+               let proposed_sat_per_vbyte = msg.fee_satoshis * 4 / closing_tx.get_weight();
+               if self.channel_outbound {
+                       let our_max_feerate = fee_estimator.get_est_sat_per_vbyte(ConfirmationTarget::Normal);
+                       if proposed_sat_per_vbyte > our_max_feerate {
+                               if let Some((last_feerate, _)) = self.last_sent_closing_fee {
+                                       if our_max_feerate <= last_feerate {
+                                               return Err(HandleError{err: "Unable to come to consensus about closing feerate, remote wanted something higher than our Normal feerate", msg: None});
+                                       }
+                               }
+                               propose_new_feerate!(our_max_feerate);
+                       }
+               } else {
+                       let our_min_feerate = fee_estimator.get_est_sat_per_vbyte(ConfirmationTarget::Background);
+                       if proposed_sat_per_vbyte < our_min_feerate {
+                               if let Some((last_feerate, _)) = self.last_sent_closing_fee {
+                                       if our_min_feerate >= last_feerate {
+                                               return Err(HandleError{err: "Unable to come to consensus about closing feerate, remote wanted something lower than our Background feerate", msg: None});
+                                       }
+                               }
+                               propose_new_feerate!(our_min_feerate);
+                       }
+               }
+
+               let our_sig = self.sign_commitment_transaction(&mut closing_tx, &msg.signature);
+               self.channel_state = ChannelState::ShutdownComplete as u32;
+
+               Ok((Some(msgs::ClosingSigned {
+                       channel_id: self.channel_id,
+                       fee_satoshis: msg.fee_satoshis,
+                       signature: our_sig,
+               }), Some(closing_tx)))
+       }
+
        // Public utilities:
 
        pub fn channel_id(&self) -> Uint256 {
@@ -1304,7 +1584,8 @@ impl Channel {
 
        /// Returns true if this channel is fully established and not known to be closing.
        pub fn is_usable(&self) -> bool {
-               (self.channel_state & (ChannelState::ChannelFunded as u32)) == (ChannelState::ChannelFunded as u32)
+               let mask = ChannelState::ChannelFunded as u32 | BOTH_SIDES_SHUTDOWN_MASK;
+               (self.channel_state & mask) == (ChannelState::ChannelFunded as u32)
        }
 
        /// Returns true if this channel is currently available for use. This is a superset of
@@ -1313,19 +1594,30 @@ impl Channel {
                self.is_usable()
        }
 
+       /// Returns true if this channel is fully shut down. True here implies that no further actions
+       /// may/will be taken on this channel, and thus this object should be freed. Any future changes
+       /// will be handled appropriately by the chain monitor.
+       pub fn is_shutdown(&self) -> bool {
+               if (self.channel_state & ChannelState::ShutdownComplete as u32) == ChannelState::ShutdownComplete as u32  {
+                       assert!(self.channel_state == ChannelState::ShutdownComplete as u32);
+                       true
+               } else { false }
+       }
+
        /// Called by channelmanager based on chain blocks being connected.
        /// Note that we only need to use this to detect funding_signed, anything else is handled by
        /// the channel_monitor.
        pub fn block_connected(&mut self, header: &BlockHeader, height: u32, txn_matched: &[&Transaction], indexes_of_txn_matched: &[u32]) -> Option<msgs::FundingLocked> {
+               let non_shutdown_state = self.channel_state & (!BOTH_SIDES_SHUTDOWN_MASK);
                if self.funding_tx_confirmations > 0 {
                        if header.bitcoin_hash() != self.last_block_connected {
                                self.last_block_connected = header.bitcoin_hash();
                                self.funding_tx_confirmations += 1;
                                if self.funding_tx_confirmations == CONF_TARGET as u64 {
-                                       if self.channel_state == ChannelState::FundingSent as u32 {
+                                       if non_shutdown_state == ChannelState::FundingSent as u32 {
                                                self.channel_state |= ChannelState::OurFundingLocked as u32;
-                                       } else if self.channel_state == (ChannelState::FundingSent as u32 | ChannelState::TheirFundingLocked as u32) {
-                                               self.channel_state = ChannelState::ChannelFunded as u32;
+                                       } else if non_shutdown_state == (ChannelState::FundingSent as u32 | ChannelState::TheirFundingLocked as u32) {
+                                               self.channel_state = ChannelState::ChannelFunded as u32 | (self.channel_state & BOTH_SIDES_SHUTDOWN_MASK);
                                                //TODO: Something about a state where we "lost confirmation"
                                        } else if self.channel_state < ChannelState::ChannelFunded as u32 {
                                                panic!("Started confirming a channel in a state pre-FundingSent?");
@@ -1336,11 +1628,7 @@ impl Channel {
                                        //as otherwise we will have a commitment transaction that they can't revoke (well, kinda,
                                        //they can by sending two revoke_and_acks back-to-back, but not really). This appears to be
                                        //a protocol oversight, but I assume I'm just missing something.
-                                       let next_per_commitment_secret = match self.build_local_commitment_secret(self.cur_local_commitment_transaction_number) {
-                                               Ok(secret) => secret,
-                                               Err(_) => return None
-                                       };
-
+                                       let next_per_commitment_secret = self.build_local_commitment_secret(self.cur_local_commitment_transaction_number);
                                        let next_per_commitment_point = PublicKey::from_secret_key(&self.secp_ctx, &next_per_commitment_secret).unwrap();
                                        return Some(msgs::FundingLocked {
                                                channel_id: self.channel_id,
@@ -1349,13 +1637,19 @@ impl Channel {
                                }
                        }
                }
-               if self.channel_state & !(ChannelState::TheirFundingLocked as u32) == ChannelState::FundingSent as u32 {
+               if non_shutdown_state & !(ChannelState::TheirFundingLocked as u32) == ChannelState::FundingSent as u32 {
                        for (ref tx, index_in_block) in txn_matched.iter().zip(indexes_of_txn_matched) {
                                if tx.txid() == self.channel_monitor.get_funding_txo().unwrap().0 {
-                                       self.funding_tx_confirmations = 1;
-                                       self.short_channel_id = Some(((height as u64)          << (5*8)) |
-                                                                    ((*index_in_block as u64) << (2*8)) |
-                                                                    ((self.channel_monitor.get_funding_txo().unwrap().1 as u64) << (2*8)));
+                                       let txo_idx = self.channel_monitor.get_funding_txo().unwrap().1 as usize;
+                                       if txo_idx >= tx.output.len() || tx.output[txo_idx].script_pubkey != self.get_funding_redeemscript().to_v0_p2wsh() ||
+                                               tx.output[txo_idx].value != self.channel_value_satoshis {
+                                               self.channel_state = ChannelState::ShutdownComplete as u32;
+                                       } else {
+                                               self.funding_tx_confirmations = 1;
+                                               self.short_channel_id = Some(((height as u64)          << (5*8)) |
+                                                                            ((*index_in_block as u64) << (2*8)) |
+                                                                            ((self.channel_monitor.get_funding_txo().unwrap().1 as u64) << (2*8)));
+                                       }
                                }
                        }
                }
@@ -1393,7 +1687,7 @@ impl Channel {
                        panic!("Tried to send an open_channel for a channel that has already advanced");
                }
 
-               let local_commitment_secret = try!(self.build_local_commitment_secret(self.cur_local_commitment_transaction_number));
+               let local_commitment_secret = self.build_local_commitment_secret(self.cur_local_commitment_transaction_number);
 
                Ok(msgs::OpenChannel {
                        chain_hash: chain_hash,
@@ -1429,7 +1723,7 @@ impl Channel {
                        panic!("Tried to send an accept_channel for a channel that has already advanced");
                }
 
-               let local_commitment_secret = try!(self.build_local_commitment_secret(self.cur_local_commitment_transaction_number));
+               let local_commitment_secret = self.build_local_commitment_secret(self.cur_local_commitment_transaction_number);
 
                Ok(msgs::AcceptChannel {
                        temporary_channel_id: self.channel_id,
@@ -1453,12 +1747,12 @@ impl Channel {
        fn get_outbound_funding_created_signature(&mut self) -> Result<Signature, HandleError> {
                let funding_script = self.get_funding_redeemscript();
 
-               let remote_keys = try!(self.build_remote_transaction_keys());
-               let remote_initial_commitment_tx = try!(self.build_commitment_transaction(self.cur_remote_commitment_transaction_number, &remote_keys, false, false)).0;
-               let remote_sighash = secp_call!(Message::from_slice(&bip143::SighashComponents::new(&remote_initial_commitment_tx).sighash_all(&remote_initial_commitment_tx, 0, &funding_script, self.channel_value_satoshis)[..]));
+               let remote_keys = self.build_remote_transaction_keys()?;
+               let remote_initial_commitment_tx = self.build_commitment_transaction(self.cur_remote_commitment_transaction_number, &remote_keys, false, false).0;
+               let remote_sighash = Message::from_slice(&bip143::SighashComponents::new(&remote_initial_commitment_tx).sighash_all(&remote_initial_commitment_tx.input[0], &funding_script, self.channel_value_satoshis)[..]).unwrap();
 
                // We sign the "remote" commitment transaction, allowing them to broadcast the tx if they wish.
-               Ok(secp_call!(self.secp_ctx.sign(&remote_sighash, &self.local_keys.funding_key)))
+               Ok(self.secp_ctx.sign(&remote_sighash, &self.local_keys.funding_key).unwrap())
        }
 
        /// Updates channel state with knowledge of the funding transaction's txid/index, and generates
@@ -1508,11 +1802,14 @@ impl Channel {
        /// bitcoin_key, if available, for this channel. The channel must be publicly announceable and
        /// available for use (have exchanged FundingLocked messages in both directions. Should be used
        /// for both loose and in response to an AnnouncementSignatures message from the remote peer.
+       /// Note that you can get an announcement for a channel which is closing, though you should
+       /// likely not announce such a thing. In case its already been announced, a channel_update
+       /// message can mark the channel disabled.
        pub fn get_channel_announcement(&self, our_node_id: PublicKey, chain_hash: Sha256dHash) -> Result<(msgs::UnsignedChannelAnnouncement, Signature), HandleError> {
                if !self.announce_publicly {
                        return Err(HandleError{err: "Channel is not available for public announcements", msg: None});
                }
-               if self.channel_state < ChannelState::ChannelFunded as u32 {
+               if self.channel_state & (ChannelState::ChannelFunded as u32) != (ChannelState::ChannelFunded as u32) {
                        return Err(HandleError{err: "Cannot get a ChannelAnnouncement until the channel funding has been locked", msg: None});
                }
 
@@ -1530,7 +1827,7 @@ impl Channel {
                };
 
                let msghash = Message::from_slice(&Sha256dHash::from_data(&msg.encode()[..])[..]).unwrap();
-               let sig = secp_call!(self.secp_ctx.sign(&msghash, &self.local_keys.funding_key));
+               let sig = self.secp_ctx.sign(&msghash, &self.local_keys.funding_key).unwrap();
 
                Ok((msg, sig))
        }
@@ -1544,8 +1841,8 @@ impl Channel {
        /// waiting on the remote peer to send us a revoke_and_ack during which time we cannot add new
        /// HTLCs on the wire or we wouldn't be able to determine what they actually ACK'ed.
        pub fn send_htlc(&mut self, amount_msat: u64, payment_hash: [u8; 32], cltv_expiry: u32, onion_routing_packet: msgs::OnionPacket) -> Result<Option<msgs::UpdateAddHTLC>, HandleError> {
-               if (self.channel_state & (ChannelState::ChannelFunded as u32)) != (ChannelState::ChannelFunded as u32) {
-                       return Err(HandleError{err: "Cannot send HTLC until channel is fully established", msg: None});
+               if (self.channel_state & (ChannelState::ChannelFunded as u32 | BOTH_SIDES_SHUTDOWN_MASK)) != (ChannelState::ChannelFunded as u32) {
+                       return Err(HandleError{err: "Cannot send HTLC until channel is fully established and we haven't started shutting down", msg: None});
                }
 
                if amount_msat > self.channel_value_satoshis * 1000 {
@@ -1565,7 +1862,7 @@ impl Channel {
                        return Err(HandleError{err: "Cannot send value that would put us over our max HTLC value in flight", msg: None});
                }
                // Check their_channel_reserve_satoshis:
-               if htlc_outbound_value_msat + amount_msat > (self.channel_value_satoshis - self.their_channel_reserve_satoshis) * 1000 - htlc_inbound_value_msat {
+               if htlc_inbound_value_msat + htlc_outbound_value_msat + amount_msat + (self.channel_value_satoshis * 1000 - self.value_to_self_msat) > (self.channel_value_satoshis - self.their_channel_reserve_satoshis) * 1000 {
                        return Err(HandleError{err: "Cannot send value that would put us over our reserve value", msg: None});
                }
 
@@ -1612,22 +1909,36 @@ impl Channel {
                if (self.channel_state & (ChannelState::ChannelFunded as u32)) != (ChannelState::ChannelFunded as u32) {
                        return Err(HandleError{err: "Cannot create commitment tx until channel is fully established", msg: None});
                }
+               if (self.channel_state & (ChannelState::AwaitingRemoteRevoke as u32)) == (ChannelState::AwaitingRemoteRevoke as u32) {
+                       return Err(HandleError{err: "Cannot create commitment tx until remote revokes their previous commitment", msg: None});
+               }
+               let mut have_updates = false; // TODO initialize with "have we sent a fee update?"
+               for htlc in self.pending_htlcs.iter() {
+                       if htlc.state == HTLCState::LocalAnnounced {
+                               have_updates = true;
+                       }
+                       if have_updates { break; }
+               }
+               if !have_updates {
+                       return Err(HandleError{err: "Cannot create commitment tx until we have some updates to send", msg: None});
+               }
 
                let funding_script = self.get_funding_redeemscript();
 
-               let remote_keys = try!(self.build_remote_transaction_keys());
-               let remote_commitment_tx = try!(self.build_commitment_transaction(self.cur_remote_commitment_transaction_number, &remote_keys, false, true));
-               let remote_sighash = secp_call!(Message::from_slice(&bip143::SighashComponents::new(&remote_commitment_tx.0).sighash_all(&remote_commitment_tx.0, 0, &funding_script, self.channel_value_satoshis)[..]));
-               let our_sig = secp_call!(self.secp_ctx.sign(&remote_sighash, &self.local_keys.funding_key));
+               let remote_keys = self.build_remote_transaction_keys()?;
+               let remote_commitment_tx = self.build_commitment_transaction(self.cur_remote_commitment_transaction_number, &remote_keys, false, true);
+               let remote_commitment_txid = remote_commitment_tx.0.txid();
+               let remote_sighash = Message::from_slice(&bip143::SighashComponents::new(&remote_commitment_tx.0).sighash_all(&remote_commitment_tx.0.input[0], &funding_script, self.channel_value_satoshis)[..]).unwrap();
+               let our_sig = self.secp_ctx.sign(&remote_sighash, &self.local_keys.funding_key).unwrap();
 
                let mut htlc_sigs = Vec::new();
 
                for ref htlc in remote_commitment_tx.1.iter() {
-                       let htlc_tx = try!(self.build_htlc_transaction(&remote_commitment_tx.0.txid(), htlc, false, &remote_keys));
+                       let htlc_tx = self.build_htlc_transaction(&remote_commitment_txid, htlc, false, &remote_keys)?;
                        let htlc_redeemscript = chan_utils::get_htlc_redeemscript(&htlc, &remote_keys, htlc.offered);
-                       let htlc_sighash = secp_call!(Message::from_slice(&bip143::SighashComponents::new(&htlc_tx).sighash_all(&htlc_tx, 0, &htlc_redeemscript, htlc.amount_msat / 1000)[..]));
-                       let our_htlc_key = secp_call!(chan_utils::derive_private_key(&self.secp_ctx, &remote_keys.per_commitment_point, &self.local_keys.htlc_base_key));
-                       htlc_sigs.push(secp_call!(self.secp_ctx.sign(&htlc_sighash, &our_htlc_key)));
+                       let htlc_sighash = Message::from_slice(&bip143::SighashComponents::new(&htlc_tx).sighash_all(&htlc_tx.input[0], &htlc_redeemscript, htlc.amount_msat / 1000)[..]).unwrap();
+                       let our_htlc_key = secp_derived_key!(chan_utils::derive_private_key(&self.secp_ctx, &remote_keys.per_commitment_point, &self.local_keys.htlc_base_key));
+                       htlc_sigs.push(self.secp_ctx.sign(&htlc_sighash, &our_htlc_key).unwrap());
                }
 
                // Update state now that we've passed all the can-fail calls...
@@ -1645,12 +1956,48 @@ impl Channel {
        /// Shorthand for calling send_htlc() followed by send_commitment(), see docs on those for
        /// more info.
        pub fn send_htlc_and_commit(&mut self, amount_msat: u64, payment_hash: [u8; 32], cltv_expiry: u32, onion_routing_packet: msgs::OnionPacket) -> Result<Option<(msgs::UpdateAddHTLC, msgs::CommitmentSigned)>, HandleError> {
-               match try!(self.send_htlc(amount_msat, payment_hash, cltv_expiry, onion_routing_packet)) {
+               match self.send_htlc(amount_msat, payment_hash, cltv_expiry, onion_routing_packet)? {
                        Some(update_add_htlc) =>
-                               Ok(Some((update_add_htlc, try!(self.send_commitment())))),
+                               Ok(Some((update_add_htlc, self.send_commitment()?))),
                        None => Ok(None)
                }
        }
+
+       /// Begins the shutdown process, getting a message for the remote peer and returning all
+       /// holding cell HTLCs for payment failure.
+       pub fn get_shutdown(&mut self) -> Result<(msgs::Shutdown, Vec<[u8; 32]>), HandleError> {
+               for htlc in self.pending_htlcs.iter() {
+                       if htlc.state == HTLCState::LocalAnnounced {
+                               return Err(HandleError{err: "Cannot begin shutdown with pending HTLCs, call send_commitment first", msg: None});
+                       }
+               }
+               if self.channel_state & BOTH_SIDES_SHUTDOWN_MASK != 0 {
+                       return Err(HandleError{err: "Shutdown already in progress", msg: None});
+               }
+               assert_eq!(self.channel_state & ChannelState::ShutdownComplete as u32, 0);
+
+               let our_closing_script = self.get_closing_scriptpubkey();
+
+               // From here on out, we may not fail!
+               if self.channel_state < ChannelState::FundingSent as u32 {
+                       self.channel_state = ChannelState::ShutdownComplete as u32;
+               } else {
+                       self.channel_state |= ChannelState::LocalShutdownSent as u32;
+               }
+
+               // We can't send our shutdown until we've committed all of our pending HTLCs, but the
+               // remote side is unlikely to accept any new HTLCs, so we go ahead and "free" any holding
+               // cell HTLCs and return them to fail the payment.
+               let mut dropped_outbound_htlcs = Vec::with_capacity(self.holding_cell_htlcs.len());
+               for htlc in self.holding_cell_htlcs.drain(..) {
+                       dropped_outbound_htlcs.push(htlc.payment_hash);
+               }
+
+               Ok((msgs::Shutdown {
+                       channel_id: self.channel_id,
+                       scriptpubkey: our_closing_script,
+               }, dropped_outbound_htlcs))
+       }
 }
 
 #[cfg(test)]
@@ -1725,12 +2072,12 @@ mod tests {
 
                macro_rules! test_commitment {
                        ( $their_sig_hex: expr, $our_sig_hex: expr, $tx_hex: expr) => {
-                               unsigned_tx = chan.build_commitment_transaction(42, &keys, true, false).unwrap();
+                               unsigned_tx = chan.build_commitment_transaction(42, &keys, true, false);
                                let their_signature = Signature::from_der(&secp_ctx, &hex_bytes($their_sig_hex).unwrap()[..]).unwrap();
-                               let sighash = Message::from_slice(&bip143::SighashComponents::new(&unsigned_tx.0).sighash_all(&unsigned_tx.0, 0, &chan.get_funding_redeemscript(), chan.channel_value_satoshis)[..]).unwrap();
+                               let sighash = Message::from_slice(&bip143::SighashComponents::new(&unsigned_tx.0).sighash_all(&unsigned_tx.0.input[0], &chan.get_funding_redeemscript(), chan.channel_value_satoshis)[..]).unwrap();
                                secp_ctx.verify(&sighash, &their_signature, &chan.their_funding_pubkey).unwrap();
 
-                               chan.sign_commitment_transaction(&mut unsigned_tx.0, &their_signature).unwrap();
+                               chan.sign_commitment_transaction(&mut unsigned_tx.0, &their_signature);
 
                                assert_eq!(serialize(&unsigned_tx.0).unwrap()[..],
                                                hex_bytes($tx_hex).unwrap()[..]);
@@ -1744,7 +2091,7 @@ mod tests {
                                let ref htlc = unsigned_tx.1[$htlc_idx];
                                let mut htlc_tx = chan.build_htlc_transaction(&unsigned_tx.0.txid(), &htlc, true, &keys).unwrap();
                                let htlc_redeemscript = chan_utils::get_htlc_redeemscript(&htlc, &keys, htlc.offered);
-                               let htlc_sighash = Message::from_slice(&bip143::SighashComponents::new(&htlc_tx).sighash_all(&htlc_tx, 0, &htlc_redeemscript, htlc.amount_msat / 1000)[..]).unwrap();
+                               let htlc_sighash = Message::from_slice(&bip143::SighashComponents::new(&htlc_tx).sighash_all(&htlc_tx.input[0], &htlc_redeemscript, htlc.amount_msat / 1000)[..]).unwrap();
                                secp_ctx.verify(&htlc_sighash, &remote_signature, &keys.b_htlc_key).unwrap();
 
                                let mut preimage: Option<[u8; 32]> = None;