Having `spot_price` and `execution_setup` as separate protocols did not bring any advantages, but was problematic because we had to ensure that `execution_setup` would be triggered after `spot_price`. Because of this dependency it is better to combine the protocols into one.
Combining the protocols also allows a refactoring to get rid of the `libp2p-async-await` dependency.
Alice always listens for the `swap_setup` protocol. When Bob opens a substream on that protocol the spot price is communicated, and then all execution setup messages (swap-id and signature exchange).
Alice chooses the fee for TxPunish because she is the one that cares.
Bob chooses the fee for TxRefund because he is the one that cares.
Note must be taken here because if the fee is too low (e.g. < min tx fee) then she might not be able to publish TxRedeem at all.
Alice chooses the fee for TxRedeem because she is the one that cares. Note must be taken here because if the fee is too low (e.g. < min tx fee) then she might not be able to publish TxRedeem at all.
- Swap-id is exchanged during execution setup. CLI (Bob) sends the swap-id to be used in his first message.
- Transfer poof and encryption signature messages include the swap-id so it can be properly associated with the correct swap.
- ASB: Encryption signatures are associated with swaps by swap-id, not peer-id.
- ASB: Transfer proofs are still associated to peer-ids (because they have to be sent to the respective peer), but the ASB can buffer multiple
- CLI: Incoming transfer proofs are checked for matching swap-id. If a transfer proof with a different swap-id than the current executing swap is received it will be ignored. We can change this to saving into the database.
Includes concurrent swap tests with the same Bob.
- One test that pauses and starts an additional swap after the transfer proof was received. Results in both swaps being redeemed after resuming the first swap.
- One test that pauses and starts an additional swap before the transfer proof is sent (just after BTC locked). Results in the second swap redeeming and the first swap being refunded (because the transfer proof on Bob's side is lost). Once we store transfer proofs that we receive during executing a different swap into the database both swaps should redeem.
Note that the monero harness was adapted to allow creating wallets with multiple outputs, which is needed for Alice.
In order for the re-construction of TxLock to be meaningful, we limit
`Message2` to the PSBT instead of the full struct. This is a breaking
change in the network layer.
The PSBT is valid if:
- It has at most two outputs (we allow a change output)
- One of the outputs pays the agreed upon amount to a shared output script
Resolves#260.
This allows us to remove all visibility modifiers from the message
fields because child modules (in this case {alice,bob}::state) can
always access private fields of structs.
It also moves the messages into a more natural place. Previously,
they were defined within the network layer even though they are
independent of the libp2p implementation.
Instead of watching for status changes directly on bitcoin::Wallet,
we return a Subscription object back to the caller. This subscription
object can be re-used multiple times.
Among other things, this now allows callers of `broadcast` to decide
on what to wait for given the returned Subscription object.
The new API is also more concise which allows us to remove some of
the functions on the actor states in favor of simple inline calls.
Co-authored-by: rishflab <rishflab@hotmail.com>
To achieve this, we decompose `watch_for_locked_xmr` into two parts:
1. A non-self-consuming function to construct a `WatchRequest`
2. A state transition that can now consume `self` again because
it is only called once within the whole select! expression.
Ideally, we would move more logic onto this state transition (like
comparing the actual amounts and fail the transition if it is not
valid). Doing so would have an unfortunate side-effect: We would
always wait for the full confirmations before checking whether or
not we actually receive enough XMR.
This allows us to have state transitions that consume self.
We have a repeated pattern where we construct one of our
Tx{Cancel,Redeem,Punish,Refund,Lock} transactions and wait until
the status of this transaction changes. We can make this more
ergonomic by creating and implementing a `Watchable` trait that
gives access to the TxId and relevant script for this transaction.
This allows us to remove a parameter from the `watch_until_status`
function.
Additionally, there is a 2nd pattern: "Completing" one of these
transaction and waiting until they are confirmed with the configured
number of blocks for finality. We can make this more ergonomic by
returning a future from `broadcast` that callers can await in case
they want to wait for the broadcasted transaction to reach finality.
The execution params don't change throughout the lifetime of the
program. They can be set in the wallet at the very beginning.
This simplifies the interface of the wallet functions.
We achieve our optimizations in three ways:
1. Batching calls instead of making them individually.
To get access to the batch calls, we replace all our
calls to the HTTP interface with RPC calls.
2. Never directly make network calls based on function
calls on the wallet.
Instead, inquiring about the status of a script always
just returns information based on local data. With every
call, we check when we last refreshed the local data and
do so if the data is considered to be too old. This
interval is configurable.
3. Use electrum's notification feature to get updated
with the latest blockheight.
Co-authored-by: Thomas Eizinger <thomas@eizinger.io>
Co-authored-by: Rishab Sharma <rishflab@hotmail.com>
This reduces the overall amount of LoC that imports take up in our
codebase by almost 100.
It also makes merge-conflicts less likely because there is less
grouping together of imports that may lead to layout changes which
in turn can cause merge conflicts.
1. We can generalize the signing interface by passing a PSBT in
instead of the `TxLock` transaction.
2. Knowing the transaction ID of a transaction that we are about
to sign is not very useful. Instead, it is much more useful to know
what failed. Hence we add a `.context` to the call of `sign_and_finalize`.
3. In case the signing succeeds, we will immediately broadcast it
afterwards. The new broadcasting interface will tell us that we broadcasted
the "lock" transaction.
We eliminate unnecessary layers of indirection for broadcasting logic
and force our callers to provide us with the `kind` of transaction
that we are publishing.
Eventually, we can replace this string with some type-system magic
we can derive the name from the actual transaction. For now, we just
require the caller to duplicate this information because it is faster
and good enough TM.
This struct is a wallet. The only thing it can meaningfully broadcast
are transactions. The fact that they have to be signed for that is
implied. You cannot broadcast unsigned transactions.
Abstracting over the individual bits of functionality of the wallet
does have its place, especially if one wants to keep a separation
of an abstract protocol library that other people can use with their
own wallets.
However, at the moment, the traits only cause unnecessary friction.
We can always add such abstraction layers again once we need them.
These traits were only used once within the `TxLock` constructor.
Looking at the rest of the codebase, we don't really seem to follow
any abstractions here where the protocol shouldn't know about the
exact types that is being passed in.
As such, these types are just noise and might as well be removed in
favor of simplicity.
The only reason we need this argument is because we need to access
the output descriptor. We can save that one ahead of time at when
we construct the type.
For transitioning to state4 we either go into a redeem or a cancellation scenario.
The function name state4 is misleading, because it is only used for cancellation scenarios.
To achieve this we also:
- upgrade rust-bitcoin to 0.26
- upgrade bitcoin-harness to latest version (which also depends bitcoin 0.26)
- upgrade to latest edcsa-fun
- replace cross_curve_dleq proof with sigma_fun (to avoid an upgrade dance over there)
