Merge pull request #10445 from lightningnetwork/backport-10439-to-v0.20.x-branch

[v0.20.x-branch] Backport #10439: Always add the payment address when probing an invoice

Author: ziggie1984

docs/release-notes/release-notes-0.20.1.md

@@ -64,6 +64,11 @@
   due to validation checks in the graph Builder that were resurfaced after the
   graph refactor work.
 
+* [Add missing payment address/secret when probing an 
+  invoice](https://github.com/lightningnetwork/lnd/pull/10439). This makes sure
+  the EstimateRouteFee API can probe Eclair and LDK nodes which enforce the
+  payment address/secret.
+
 # New Features
 
 ## Functional Enhancements

lnrpc/routerrpc/router_server.go

@@ -557,6 +557,7 @@ func (s *Server) probePaymentRequest(ctx context.Context, paymentRequest string,
 	// If the payment addresses is specified, then we'll also populate that
 	// now as well.
 	payReq.PaymentAddr.WhenSome(func(addr [32]byte) {
+		probeRequest.PaymentAddr = make([]byte, lntypes.HashSize)
 		copy(probeRequest.PaymentAddr, addr[:])
 	})
 
@@ -624,6 +625,10 @@ func (s *Server) probePaymentRequest(ctx context.Context, paymentRequest string,
 
 		// Copy the payment address if present.
 		if len(probeRequest.PaymentAddr) > 0 {
+			lspProbeRequest.PaymentAddr = make(
+				[]byte, lntypes.HashSize,
+			)
+
 			copy(
 				lspProbeRequest.PaymentAddr,
 				probeRequest.PaymentAddr,