+ /// Send a payment that is probing the given route for liquidity. We calculate the
+ /// [`PaymentHash`] of probes based on a static secret and a random [`PaymentId`], which allows
+ /// us to easily discern them from real payments.
+ pub fn send_probe(&self, hops: Vec<RouteHop>) -> Result<(PaymentHash, PaymentId), PaymentSendFailure> {
+ let payment_id = PaymentId(self.keys_manager.get_secure_random_bytes());
+
+ let payment_hash = self.probing_cookie_from_id(&payment_id);
+
+ if hops.len() < 2 {
+ return Err(PaymentSendFailure::ParameterError(APIError::APIMisuseError {
+ err: "No need probing a path with less than two hops".to_string()
+ }))
+ }
+
+ let route = Route { paths: vec![hops], payment_params: None };
+
+ match self.send_payment_internal(&route, payment_hash, &None, None, Some(payment_id), None) {
+ Ok(payment_id) => Ok((payment_hash, payment_id)),
+ Err(e) => Err(e)
+ }
+ }
+
+ /// Returns whether a payment with the given [`PaymentHash`] and [`PaymentId`] is, in fact, a
+ /// payment probe.
+ pub(crate) fn payment_is_probe(&self, payment_hash: &PaymentHash, payment_id: &PaymentId) -> bool {
+ let target_payment_hash = self.probing_cookie_from_id(payment_id);
+ target_payment_hash == *payment_hash
+ }
+
+ /// Returns the 'probing cookie' for the given [`PaymentId`].
+ fn probing_cookie_from_id(&self, payment_id: &PaymentId) -> PaymentHash {
+ let mut preimage = [0u8; 64];
+ preimage[..32].copy_from_slice(&self.probing_cookie_secret);
+ preimage[32..].copy_from_slice(&payment_id.0);
+ PaymentHash(Sha256::hash(&preimage).into_inner())
+ }
+