fix: block redundant conn reinit on cross-connect INIT (reset_done flag)

Problem: when two peers connect simultaneously, each incoming
INIT_REQUEST(0x02) or INIT_RESPONSE(0x03) triggers etcp_conn_reinit
unconditionally, causing endless UP/DOWN flapping loop.

Fix: add reset_done flag to ETCP_CONN:
- 0 at creation and after explicit reinit (reinit allowed)
- set to 1 in etcp_conn_ready (connection stable, block reinit)

Three call sites guarded with !conn->reset_done:
- client: handle_init_response_client (INIT_RESPONSE 0x03)
- server: existing link INIT_REQUEST processing
- server: new link INIT_REQUEST processing

send_reset logic preserved unconditionally — only etcp_conn_reinit
itself is blocked when already stable.

src/etcp.c

@@ -215,6 +215,7 @@ struct ETCP_CONN* etcp_connection_create(struct UTUN_INSTANCE* instance, char* n
     etcp->optimal_inflight=100000;
     etcp->initialized=0;
     etcp->links_up=0;
+    etcp->reset_done=0;
     etcp->last_rr_link=NULL;
     etcp->name = u_strdup(name);
     // Initialize log_name with local node_id (peer will be updated later when known)
@@ -503,7 +504,7 @@ void etcp_conn_reinit(struct ETCP_CONN* etcp) {// Если сбой в обме
                etcp->log_name, etcp->initialized, etcp->links_up, etcp->reinit_count, etcp->tx_state);
 
     etcp->reinit_count++;
-
+    etcp->reset_done = 0;
     etcp->initialized = 0;// еще раз придёт conn_ready_callback
 
     // Отменяем висящие NAT-ping'и для этого соединения
@@ -530,6 +531,7 @@ void etcp_conn_ready(struct ETCP_CONN* conn) {
     if (!conn) return;
 
     conn->initialized = 1;
+    conn->reset_done = 1;
     // Если tx_state не установлен (первое подключение без reinit), установим его
     if (conn->tx_state == 0) {
         conn->tx_state = ETCP_TX_STATE_DATA_WAIT;

src/etcp.h

@@ -225,6 +225,7 @@ struct ETCP_CONN {
     uint32_t session_id;             // случайный ID сессии (генерируется клиентом) для защиты от ложного reinit
     uint8_t tx_state;                // 0 - n/a, 1 - data_wait (queues empty), 2 - link_wait (link busy)
     uint8_t links_up;                // 0 - канал не готов для передачи, 1 - канал готов для передачи (хотя бы один линк не down)
+    uint8_t reset_done;              // 0 - рукопожатие не завершено (реинит разрешён), 1 - соединение стабильно (реинит заблокирован)
 
     // Callback chains for ready/up/down notifications
     struct etcp_cbk_entry* ready_cbks;   // цепочка callback'ов при готовности соединения

src/etcp_connections.c

@@ -1473,7 +1473,7 @@ static int handle_init_response_client(struct ETCP_SOCKET* e_sock, struct ETCP_D
         link->init_timer = NULL;
     }
 
-    if (pkt_code == ETCP_INIT_RESPONSE) {
+    if (pkt_code == ETCP_INIT_RESPONSE && !link->etcp->reset_done) {
         DEBUG_INFO(DEBUG_CATEGORY_DEBUG, "[%s] REINIT from client: INIT_RESPONSE(0x03) received, reinit conn=%p",
                    link->etcp->log_name, link->etcp);
         etcp_conn_reinit(link->etcp);
@@ -1748,10 +1748,11 @@ void etcp_connections_read_callback_socket(socket_t sock, void* arg) {
         // Check session_id: if same - no reinit, if different - client restarted, do reinit
         if (code == ETCP_INIT_REQUEST || conn->session_id != session_id || !conn->got_initial_pkt) {
             send_reset = 1;  // Client explicitly requested reset, or new session, or server waiting for first packet
-            DEBUG_INFO(DEBUG_CATEGORY_DEBUG, "[%s] REINIT existing link: code=0x%02x sess=%08x→%08x got_init=%d initialized=%d links_up=%d",
-                       conn->log_name, code, conn->session_id, session_id, conn->got_initial_pkt, conn->initialized, conn->links_up);
+            DEBUG_INFO(DEBUG_CATEGORY_DEBUG, "[%s] REINIT existing link: code=0x%02x sess=%08x→%08x got_init=%d initialized=%d links_up=%d reset_done=%d",
+                       conn->log_name, code, conn->session_id, session_id, conn->got_initial_pkt, conn->initialized, conn->links_up, conn->reset_done);
             conn->session_id = session_id;
-            etcp_conn_reinit(conn);
+            if (!conn->reset_done) etcp_conn_reinit(conn);
+            else DEBUG_INFO(DEBUG_CATEGORY_DEBUG, "[%s] REINIT skipped — reset_done=1", conn->log_name);
         } else {
             send_reset = 0;  // Same session, no reinit needed
             DEBUG_TRACE(DEBUG_CATEGORY_CONNECTION, "same session_id, skip reinit");
@@ -1775,10 +1776,11 @@ void etcp_connections_read_callback_socket(socket_t sock, void* arg) {
         // For new links: reset if client requested or session changed
         if (code == ETCP_INIT_REQUEST || conn->session_id != session_id || !conn->got_initial_pkt) {
             send_reset = 1;
-            DEBUG_INFO(DEBUG_CATEGORY_DEBUG, "[%s] REINIT new link: code=0x%02x sess=%08x→%08x got_init=%d initialized=%d links_up=%d",
-                       conn->log_name, code, conn->session_id, session_id, conn->got_initial_pkt, conn->initialized, conn->links_up);
+            DEBUG_INFO(DEBUG_CATEGORY_DEBUG, "[%s] REINIT new link: code=0x%02x sess=%08x→%08x got_init=%d initialized=%d links_up=%d reset_done=%d",
+                       conn->log_name, code, conn->session_id, session_id, conn->got_initial_pkt, conn->initialized, conn->links_up, conn->reset_done);
             conn->session_id = session_id;
-            etcp_conn_reinit(conn);
+            if (!conn->reset_done) etcp_conn_reinit(conn);
+            else DEBUG_INFO(DEBUG_CATEGORY_DEBUG, "[%s] REINIT skipped — reset_done=1", conn->log_name);
         }
         link->keepalive_interval=(req->keepalive[0]<<8) | req->keepalive[1];
         link->recovery_interval=((req->recovery[0]<<8) | req->recovery[1])*100;// timebase в link, timebase/100 в кодограмме