Fix cmp::max execution in ChannelContext::get_dust_buffer_feerate

  The current `cmp::max` doesnt align with the function comment, ie its
  comparing 2530 and `feerate_plus_quarter` instead of `feerate_per_kw
  + 2530` and `feerate_plus_quarter` which is fixed in this commit

lightning/src/ln/channel.rs

@@ -2699,7 +2699,7 @@ impl<SP: Deref> ChannelContext<SP> where SP::Target: SignerProvider  {
 			feerate_per_kw = cmp::max(feerate_per_kw, feerate);
 		}
 		let feerate_plus_quarter = feerate_per_kw.checked_mul(1250).map(|v| v / 1000);
-		cmp::max(2530, feerate_plus_quarter.unwrap_or(u32::max_value()))
+		cmp::max(feerate_per_kw + 2530, feerate_plus_quarter.unwrap_or(u32::max_value()))
 	}
 
 	/// Get forwarding information for the counterparty.

lightning/src/ln/functional_tests.rs

@@ -9891,8 +9891,8 @@ fn do_test_max_dust_htlc_exposure(dust_outbound_balance: bool, exposure_breach_e
 		// Default test fee estimator rate is 253 sat/kw, so we set the multiplier to 5_000_000 / 253
 		// to get roughly the same initial value as the default setting when this test was
 		// originally written.
-		MaxDustHTLCExposure::FeeRateMultiplier(5_000_000 / 253)
-	} else { MaxDustHTLCExposure::FixedLimitMsat(5_000_000) }; // initial default setting value
+		MaxDustHTLCExposure::FeeRateMultiplier(6_000_000 / 253)
+	} else { MaxDustHTLCExposure::FixedLimitMsat(6_000_000) }; // initial default setting value
 	let node_cfgs = create_node_cfgs(2, &chanmon_cfgs);
 	let node_chanmgrs = create_node_chanmgrs(2, &node_cfgs, &[Some(config), None]);
 	let mut nodes = create_network(2, &node_cfgs, &node_chanmgrs);
@@ -10032,7 +10032,7 @@ fn do_test_max_dust_htlc_exposure(dust_outbound_balance: bool, exposure_breach_e
 		// For the multiplier dust exposure limit, since it scales with feerate,
 		// we need to add a lot of HTLCs that will become dust at the new feerate
 		// to cross the threshold.
-		for _ in 0..20 {
+		for _ in 0..30 {
 			let (_, payment_hash, payment_secret) = get_payment_preimage_hash(&nodes[1], Some(1_000), None);
 			nodes[0].node.send_payment_with_route(&route, payment_hash,
 				RecipientOnionFields::secret_only(payment_secret), PaymentId(payment_hash.0)).unwrap();
@@ -10054,12 +10054,12 @@ fn do_test_max_dust_htlc_exposure(dust_outbound_balance: bool, exposure_breach_e
 fn do_test_max_dust_htlc_exposure_by_threshold_type(multiplier_dust_limit: bool) {
 	do_test_max_dust_htlc_exposure(true, ExposureEvent::AtHTLCForward, true, multiplier_dust_limit);
 	do_test_max_dust_htlc_exposure(false, ExposureEvent::AtHTLCForward, true, multiplier_dust_limit);
+	do_test_max_dust_htlc_exposure(false, ExposureEvent::AtHTLCForward, false, multiplier_dust_limit);
+	do_test_max_dust_htlc_exposure(true, ExposureEvent::AtHTLCForward, false, multiplier_dust_limit);
 	do_test_max_dust_htlc_exposure(false, ExposureEvent::AtHTLCReception, true, multiplier_dust_limit);
 	do_test_max_dust_htlc_exposure(false, ExposureEvent::AtHTLCReception, false, multiplier_dust_limit);
-	do_test_max_dust_htlc_exposure(true, ExposureEvent::AtHTLCForward, false, multiplier_dust_limit);
 	do_test_max_dust_htlc_exposure(true, ExposureEvent::AtHTLCReception, false, multiplier_dust_limit);
 	do_test_max_dust_htlc_exposure(true, ExposureEvent::AtHTLCReception, true, multiplier_dust_limit);
-	do_test_max_dust_htlc_exposure(false, ExposureEvent::AtHTLCForward, false, multiplier_dust_limit);
 	do_test_max_dust_htlc_exposure(true, ExposureEvent::AtUpdateFeeOutbound, true, multiplier_dust_limit);
 	do_test_max_dust_htlc_exposure(true, ExposureEvent::AtUpdateFeeOutbound, false, multiplier_dust_limit);
 	do_test_max_dust_htlc_exposure(false, ExposureEvent::AtUpdateFeeOutbound, false, multiplier_dust_limit);