From c1e8c281288a19ce2b621fcdb4ebdac02edec736 Mon Sep 17 00:00:00 2001
From: Ben Meadors <benmmeadors@gmail.com>
Date: Sat, 27 Sep 2025 16:25:40 -0500
Subject: [PATCH] Revert "Revert cross-preset UDP bridging"

This reverts commit 359a4dbd680e28c39dd0944a9b3f5f0fb83bd91e.
---
 src/mesh/Router.cpp | 29 +++++++++++++++++++++++++++++
 1 file changed, 29 insertions(+)

diff --git a/src/mesh/Router.cpp b/src/mesh/Router.cpp
index ad3366002..828f70018 100644
--- a/src/mesh/Router.cpp
+++ b/src/mesh/Router.cpp
@@ -491,6 +491,35 @@ DecodeState perhapsDecode(meshtastic_MeshPacket *p)
         }
     }
 
+#if HAS_UDP_MULTICAST
+    // Fallback: for UDP multicast, try default preset names with default PSK if normal channel match failed
+    if (!decrypted && p->transport_mechanism == meshtastic_MeshPacket_TransportMechanism_TRANSPORT_MULTICAST_UDP) {
+        if (channels.setDefaultPresetCryptoForHash(p->channel)) {
+            memcpy(bytes, p->encrypted.bytes, rawSize);
+            crypto->decrypt(p->from, p->id, rawSize, bytes);
+
+            meshtastic_Data decodedtmp;
+            memset(&decodedtmp, 0, sizeof(decodedtmp));
+            if (pb_decode_from_bytes(bytes, rawSize, &meshtastic_Data_msg, &decodedtmp) &&
+                decodedtmp.portnum != meshtastic_PortNum_UNKNOWN_APP) {
+                p->decoded = decodedtmp;
+                p->which_payload_variant = meshtastic_MeshPacket_decoded_tag;
+                // Map to our local default channel index (name+PSK default), not necessarily primary
+                ChannelIndex defaultIndex = channels.getPrimaryIndex();
+                for (ChannelIndex i = 0; i < channels.getNumChannels(); ++i) {
+                    if (channels.isDefaultChannel(i)) {
+                        defaultIndex = i;
+                        break;
+                    }
+                }
+                chIndex = defaultIndex;
+                decrypted = true;
+            } else {
+                LOG_WARN("UDP fallback decode attempted but failed for hash 0x%x", p->channel);
+            }
+        }
+    }
+#endif
     if (decrypted) {
         // parsing was successful
         p->channel = chIndex; // change to store the index instead of the hash