f - avoid exposing esoteric CLTV expiry deltas

Author: jkczyz

lightning/src/routing/router.rs

@@ -118,9 +118,18 @@ impl<G: Deref<Target = NetworkGraph<L>> + Clone, L: Deref, S: Deref, SP: Sized,
 					Some(forwarding_info) => forwarding_info.into(),
 					None => return None,
 				};
+
+				// Avoid exposing esoteric CLTV expiry deltas
+				let cltv_expiry_delta = match payment_relay.cltv_expiry_delta {
+					0..=40 => 40u32,
+					41..=80 => 80u32,
+					81..=144 => 144u32,
+					145..=216 => 216u32,
+					_ => return None,
+				};
+
 				let payment_constraints = PaymentConstraints {
-					max_cltv_expiry: tlvs.payment_constraints.max_cltv_expiry
-						+ payment_relay.cltv_expiry_delta as u32,
+					max_cltv_expiry: tlvs.payment_constraints.max_cltv_expiry + cltv_expiry_delta,
 					htlc_minimum_msat: details.inbound_htlc_minimum_msat.unwrap_or(0),
 				};
 				Some(ForwardNode {