consolidate 3 SQLite connections into 1 shared handle

- utun_node.cpp: open topo_sqlite_db with FULLMUTEX + all PRAGMAs (WAL, FK, NORMAL sync, checkpoint)
- db_sync.c: reuse inst->topo_sqlite_db if available (shared_db flag)
- chat_core.c: reuse inst->topo_sqlite_db if available (shared_db flag)
- db_sync_destroy/chat_core_destroy: skip close on shared handle
- Only topo_groups_destroy closes the shared handle
- Fallback: each module opens own connection if topo_sqlite_db is NULL

src/db_sync.c

@@ -58,6 +58,7 @@ struct DB_SYNC_INSTANCE {
 struct DB_SYNC {
     struct UTUN_INSTANCE* inst;
     sqlite3*  db;
+    uint8_t   shared_db;  /* db == inst->topo_sqlite_db, do not close */
     uint64_t  last_connected_tb;
     struct DB_SYNC_INSTANCE* instances;
     int instance_count, instance_capacity;
@@ -110,7 +111,7 @@ static int db_sqlite_open(struct DB_SYNC* db, const char* path)
 static void db_sqlite_close(struct DB_SYNC* db)
 {
     DEBUG_TRACE(DEBUG_CATEGORY_DB_SYNC, "");
-    if (!db->db) return;
+    if (!db->db || db->shared_db) return;
     sqlite3_close(db->db);
     db->db = NULL;
     DEBUG_INFO(DEBUG_CATEGORY_DB_SYNC, "db_sync: SQLite closed");
@@ -1376,13 +1377,17 @@ int db_sync_init(struct UTUN_INSTANCE* inst)
     inst->db_sync = db;
 
     const char* dp = inst->config->global.db_path;
-    char sp[512];
-    if (dp[0]) snprintf(sp, sizeof(sp), "%s/chats.db", dp);
-    else       snprintf(sp, sizeof(sp), "/tmp/utun_db_sync");
-
-    if (db_sqlite_open(db, sp) != 0) {
-        DEBUG_WARN(DEBUG_CATEGORY_DB_SYNC, "SQLite open failed, sync disabled");
-        db->enabled = 0;
+    if (inst->topo_sqlite_db) {
+        db->db = inst->topo_sqlite_db; db->shared_db = 1;
+        DEBUG_INFO(DEBUG_CATEGORY_DB_SYNC, "db_sync: using shared SQLite db=%p", (void*)db->db);
+    } else {
+        char sp[512];
+        if (dp[0]) snprintf(sp, sizeof(sp), "%s/chats.db", dp);
+        else       snprintf(sp, sizeof(sp), "/tmp/utun_db_sync");
+        if (db_sqlite_open(db, sp) != 0) {
+            DEBUG_WARN(DEBUG_CATEGORY_DB_SYNC, "SQLite open failed, sync disabled");
+            db->enabled = 0;
+        }
     }
 
     etcp_bind(inst, ETCP_RT_ID_DB_SYNC, db_sync_recv_cb);

tools/chatgui/transport/chat_core.c

@@ -37,6 +37,7 @@
 static struct chat_core_ctx {
     struct UTUN_INSTANCE* inst;
     sqlite3*              db;
+    uint8_t               shared_db;  /* db == inst->topo_sqlite_db, do not close */
     uint64_t              my_node_id;
 
     /* db_sync instances per channel */
@@ -91,15 +92,20 @@ int chat_core_init(struct UTUN_INSTANCE* inst, const char* db_path) {
     if (!inst || !db_path) return -1;
     memset(&g_cc, 0, sizeof(g_cc));
 
-    int rc = sqlite3_open_v2(db_path, &g_cc.db,
-        SQLITE_OPEN_READWRITE | SQLITE_OPEN_CREATE | SQLITE_OPEN_FULLMUTEX, NULL);
-    if (rc != SQLITE_OK) {
-        DEBUG_ERROR(DEBUG_CATEGORY_CONNECTIVITY, "%s: cannot open DB %s: %s",
-                    CC_ID, db_path, sqlite3_errmsg(g_cc.db));
-        sqlite3_close(g_cc.db); g_cc.db = NULL; return -1;
+    if (inst->topo_sqlite_db) {
+        g_cc.db = inst->topo_sqlite_db; g_cc.shared_db = 1;
+        DEBUG_INFO(DEBUG_CATEGORY_CONNECTIVITY, "%s: using shared SQLite db=%p", CC_ID, (void*)g_cc.db);
+    } else {
+        int rc = sqlite3_open_v2(db_path, &g_cc.db,
+            SQLITE_OPEN_READWRITE | SQLITE_OPEN_CREATE | SQLITE_OPEN_FULLMUTEX, NULL);
+        if (rc != SQLITE_OK) {
+            DEBUG_ERROR(DEBUG_CATEGORY_CONNECTIVITY, "%s: cannot open DB %s: %s",
+                        CC_ID, db_path, sqlite3_errmsg(g_cc.db));
+            sqlite3_close(g_cc.db); g_cc.db = NULL; return -1;
+        }
+        sqlite3_exec(g_cc.db, "PRAGMA journal_mode=WAL", NULL, NULL, NULL);
+        sqlite3_exec(g_cc.db, "PRAGMA foreign_keys=ON", NULL, NULL, NULL);
     }
-    sqlite3_exec(g_cc.db, "PRAGMA journal_mode=WAL", NULL, NULL, NULL);
-    sqlite3_exec(g_cc.db, "PRAGMA foreign_keys=ON", NULL, NULL, NULL);
 
     g_cc.inst       = inst;
     g_cc.my_node_id = inst->node_id;
@@ -229,7 +235,8 @@ void chat_core_destroy(struct UTUN_INSTANCE* inst) {
     if (!g_cc.initialized) return;
     g_cc.initialized = 0;
 
-    if (g_cc.db) { sqlite3_close(g_cc.db); g_cc.db = NULL; }
+    if (g_cc.db && !g_cc.shared_db) { sqlite3_close(g_cc.db); }
+    g_cc.db = NULL;
     g_cc.inst = NULL;
     DEBUG_INFO(DEBUG_CATEGORY_CONNECTIVITY, "%s: destroyed", CC_ID);
 }

tools/chatgui/transport/utun_node.cpp

@@ -26,6 +26,7 @@ extern "C" {
 #include "chat_core.h"
 #include "db_sync.h"
 #include "gui_bridge.h"
+#include "../src/topo_node_sqlite.h"
 }
 
 #define ETCP_RT_ID_CHAT  0x11
@@ -260,6 +261,27 @@ void UtunNode::runLoop() {
         snprintf(m_instance->config->global.db_path, sizeof(m_instance->config->global.db_path),
                  "%s", m_dbPath.toUtf8().constData());
 
+    /* topo_groups_init did not open topo_sqlite_db because db_path was empty at that time.
+     * Open the single shared SQLite connection here with FULLMUTEX (GUI reads from another thread).
+     * db_sync_init and chat_core_init will reuse this handle. */
+    if (m_instance->config->global.db_path[0] && !m_instance->topo_sqlite_db) {
+        char db_file[512];
+        snprintf(db_file, sizeof(db_file), "%s/chats.db", m_instance->config->global.db_path);
+        int rc = sqlite3_open_v2(db_file, &m_instance->topo_sqlite_db,
+            SQLITE_OPEN_READWRITE | SQLITE_OPEN_CREATE | SQLITE_OPEN_FULLMUTEX, NULL);
+        if (rc == SQLITE_OK && m_instance->topo_sqlite_db) {
+            sqlite3_exec(m_instance->topo_sqlite_db, "PRAGMA journal_mode=WAL", NULL, NULL, NULL);
+            sqlite3_exec(m_instance->topo_sqlite_db, "PRAGMA foreign_keys=ON", NULL, NULL, NULL);
+            sqlite3_exec(m_instance->topo_sqlite_db, "PRAGMA synchronous=NORMAL", NULL, NULL, NULL);
+            sqlite3_exec(m_instance->topo_sqlite_db, "PRAGMA wal_autocheckpoint=10000", NULL, NULL, NULL);
+            topo_node_sqlite_init(m_instance->topo_sqlite_db);
+            DEBUG_INFO(DEBUG_CATEGORY_DEBUG, "SQLite (shared): %s db=%p", db_file, (void*)m_instance->topo_sqlite_db);
+        } else {
+            DEBUG_ERROR(DEBUG_CATEGORY_DEBUG, "SQLite open failed: %s rc=%d", db_file, rc);
+            if (m_instance->topo_sqlite_db) { sqlite3_close(m_instance->topo_sqlite_db); m_instance->topo_sqlite_db = NULL; }
+        }
+    }
+
     /* set ua for gui_bridge before init, so GUI can post */
     gui_bridge_set_uasync(ua);