Add a general-purpose packet cache (#8341)

* Add general-purpose packet cache This commit adds a caching system that will save packet data in a much more compact form than the regular MeshPacket protobuf. It cannot be worked with directly to the same degree (although the packet header is available), but consumes *much* less memory, and as a result can be used to temporarily store large numbers of packets. Cached packets can be retrieved either by their (from, id) tuple, or by their hash. This cache is a pre-requisite for the upcoming packet replay feature. * Remove debug initialiser Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com> * Fix ordering Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com> * Add missing size assignment Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com> * Add comments for hash & bucket macros * Make it clear that this field stores a map of the original data --------- Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com> Co-authored-by: Ben Meadors <benmmeadors@gmail.com>
2025-12-16 07:42:37 +00:00 · 2025-10-15 13:22:45 +13:00
parent e8f4d07e9f
commit 9a8aeb25ab
2 changed files with 328 additions and 0 deletions
--- a/src/mesh/PacketCache.h
+++ b/src/mesh/PacketCache.h
@@ -0,0 +1,75 @@
+#pragma once
+#include "RadioInterface.h"
+
+#define PACKET_HASH(a, b) ((((a ^ b) >> 16) ^ (a ^ b)) & 0xFFFF) // 16 bit fold of packet (from, id) tuple
+typedef uint16_t PacketHash;
+
+#define PACKET_CACHE_BUCKETS 64                                    // Number of hash table buckets
+#define PACKET_CACHE_BUCKET(h) (((h >> 12) ^ (h >> 6) ^ h) & 0x3F) // Fold hash down to 6-bit bucket index
+
+typedef struct PacketCacheEntry {
+    PacketCacheEntry *next;
+    PacketHeader header;
+    uint16_t payload_len = 0;
+    union {
+        uint16_t bitfield;
+        struct {
+            uint8_t encrypted : 1;    // Payload is encrypted
+            uint8_t has_metadata : 1; // Payload includes PacketCacheMetadata
+            uint8_t : 6;              // Reserved for future use
+            uint16_t : 8;             // Reserved for future use
+        };
+    };
+} PacketCacheEntry;
+
+typedef struct PacketCacheMetadata {
+    PacketCacheMetadata() : _bitfield(0), reply_id(0), _bitfield2(0) {}
+    union {
+        uint32_t _bitfield;
+        struct {
+            uint16_t portnum : 9;       // meshtastic_MeshPacket::decoded::portnum
+            uint16_t want_response : 1; // meshtastic_MeshPacket::decoded::want_response
+            uint16_t emoji : 1;         // meshtastic_MeshPacket::decoded::emoji
+            uint16_t bitfield : 5;      // meshtastic_MeshPacket::decoded::bitfield (truncated)
+            uint8_t rx_rssi : 8;        // meshtastic_MeshPacket::rx_rssi (map via actual RSSI + 200)
+            uint8_t rx_snr : 8;         // meshtastic_MeshPacket::rx_snr (map via (p->rx_snr + 30.0f) / 0.25f)
+        };
+    };
+    union {
+        uint32_t reply_id;   // meshtastic_MeshPacket::decoded.reply_id
+        uint32_t request_id; // meshtastic_MeshPacket::decoded.request_id
+    };
+    uint32_t rx_time = 0;            // meshtastic_MeshPacket::rx_time
+    uint8_t transport_mechanism = 0; // meshtastic_MeshPacket::transport_mechanism
+    struct {
+        uint8_t _bitfield2;
+        union {
+            uint8_t priority : 7; // meshtastic_MeshPacket::priority
+            uint8_t reserved : 1; // Reserved for future use
+        };
+    };
+} PacketCacheMetadata;
+
+class PacketCache
+{
+  public:
+    PacketCacheEntry *cache(const meshtastic_MeshPacket *p, bool preserveMetadata);
+    static void dump(void *dest, const PacketCacheEntry **entries, size_t num_entries);
+    size_t dumpSize(const PacketCacheEntry **entries, size_t num_entries);
+    PacketCacheEntry *find(NodeNum from, PacketId id);
+    PacketCacheEntry *find(PacketHash h);
+    bool load(void *src, PacketCacheEntry **entries, size_t num_entries);
+    size_t getNumEntries() { return num_entries; }
+    size_t getSize() { return size; }
+    void rehydrate(const PacketCacheEntry *e, meshtastic_MeshPacket *p);
+    void release(PacketCacheEntry *e);
+
+  private:
+    PacketCacheEntry *buckets[PACKET_CACHE_BUCKETS]{};
+    size_t num_entries = 0;
+    size_t size = 0;
+    void insert(PacketCacheEntry *e);
+    void remove(PacketCacheEntry *e);
+};
+
+extern PacketCache packetCache;