etcp: адаптивный keepalive — отдельная команда ETCP_KEEPALIVE с period_ms

- ETCP_KEEPALIVE=0x08, формат: [0x08][period_lo][period_hi]
- link->ka_period_ms: 200ms при трафике, ×1.05+1 в idle, потолок 10s
- keepalive_timeout = peer_period * KA_TIMEOUT_MULT(10)
- приём KA обновляет keepalive_timeout адаптивно (2000ms→100000ms)
- флаг recv_keepalive по-прежнему в flag_up для быстрого сигнала

src/etcp_connections.c

@@ -239,15 +239,16 @@ static void etcp_link_send_keepalive(struct ETCP_LINK* link) {
     }
 
     dgram->link = link;
-    dgram->data_len = 0;  // Empty packet - only timestamp in header
+    dgram->data[0] = ETCP_KEEPALIVE;
+    dgram->data[1] = link->ka_period_ms & 0xFF;
+    dgram->data[2] = link->ka_period_ms >> 8;
+    dgram->data_len = 3;
     dgram->noencrypt_len = 0;
     dgram->timestamp = get_current_timestamp();
-
-    DEBUG_DEBUG(DEBUG_CATEGORY_KEEPALIVE, "[%s] Sending keepalive on link %p (local_id=%d)",
-                link->etcp->log_name, link, link->local_link_id);
+    dgram->flag_up = link->recv_keepalive;
 
     link->keepalive_sent_count++;
-    
+
     etcp_encrypt_send(dgram);
     u_free(dgram);
 }
@@ -320,17 +321,21 @@ static void keepalive_timer_cb(void* arg) {
         }
     }
 
-    // Send keepalive only if no packets were sent since last tick
-    if (!link->pkt_sent_since_keepalive) {
-      if (link->is_server) {
-        if (link->recv_keepalive) etcp_link_send_keepalive(link);// сервер прекращает слать keepalive если линк потерян (ждём keepalive клиента)
-        }
-      else etcp_link_send_keepalive(link);
-      }
+    // Adaptive keepalive period
+    if (link->pkt_sent_since_keepalive)
+        link->ka_period_ms = KA_PERIOD_MIN_MS;   // data flowing → reset to 200ms
+    else {
+        uint32_t next = (uint32_t)link->ka_period_ms * 105 / 100 + 1;
+        link->ka_period_ms = next > KA_PERIOD_MAX_MS ? KA_PERIOD_MAX_MS : (uint16_t)next;
+    }
     link->pkt_sent_since_keepalive = 0;
 
+    // Send keepalive (server stops if link lost, client always sends)
+    if (!link->is_server || link->recv_keepalive)
+        etcp_link_send_keepalive(link);
+
 restart_timer:
-    link->keepalive_timer = uasync_set_timeout(link->etcp->instance->ua, link->keepalive_interval * 10, link, keepalive_timer_cb, "link_keepalive");
+    link->keepalive_timer = uasync_set_timeout(link->etcp->instance->ua, link->ka_period_ms * 10, link, keepalive_timer_cb, "link_keepalive");
 }
 
 static uint32_t sockaddr_hash(struct sockaddr_storage* addr) {
@@ -781,6 +786,7 @@ struct ETCP_LINK* etcp_link_new(struct ETCP_CONN* etcp, struct ETCP_SOCKET* conn
     if (link->keepalive_interval < 10) link->keepalive_interval = 10;
     link->keepalive_sent_count = 0;
     link->keepalive_recv_count = 0;
+    link->ka_period_ms = KA_PERIOD_MIN_MS;
     link->inflight_lim_bytes = link->mtu * 4;     // BBR init_cwnd (~4 packets)
     link->bandwidth = 10000;                       // начальная оценка 10 Mbps для шейпера
     link->burst_id = 0;
@@ -1589,17 +1595,20 @@ process_decrypted:
     
     // Count decrypted bytes
     link->total_decrypted += pkt->data_len;
-    
-    // Count received keepalive packets (empty packets with no payload)
-    if (pkt->data_len == 0) {
-        link->keepalive_recv_count++;
-        DEBUG_DEBUG(DEBUG_CATEGORY_KEEPALIVE, "[%s] Received keepalive on link %p (local_id=%d)",
-                    link->etcp->log_name, link, link->local_link_id);
-    }
-    
+
     size_t offset = 0;
     uint8_t code = pkt->data[offset++];
 
+    if (code == ETCP_KEEPALIVE) {
+        if (pkt->data_len >= 3) {
+            uint16_t peer_period = pkt->data[1] | ((uint16_t)pkt->data[2] << 8);
+            link->keepalive_timeout = (uint32_t)peer_period * KA_TIMEOUT_MULT;
+        }
+        link->keepalive_recv_count++;
+        memory_pool_free(e_sock->instance->pkt_pool, pkt);
+        return;  // KA handled, nothing more to process
+    }
+
     if (code == ETCP_INIT_RESPONSE || code == ETCP_INIT_RESPONSE_NOINIT) {
         if (pkt_len < 22) { errorcode = 46; DEBUG_ERROR(DEBUG_CATEGORY_ETCP, "INIT_RESPONSE too short: pkt_len=%zu", pkt_len); goto ec_fr; }
         // ETCP_INIT_RESPONSE (0x03) - reset entire ETCP_CONN

src/etcp_connections.h

@@ -26,6 +26,12 @@
 #define ETCP_INIT_RESPONSE_NOINIT   0x05
 #define ETCP_PING               0x06
 #define ETCP_PONG               0x07
+#define ETCP_KEEPALIVE          0x08
+
+/* Адаптивный keepalive */
+#define KA_PERIOD_MIN_MS   200
+#define KA_PERIOD_MAX_MS   10000
+#define KA_TIMEOUT_MULT    10       /* timeout = period * mult */
 
 
 #pragma pack(push, 1)
@@ -194,6 +200,7 @@ struct ETCP_LINK {
     // Keepalive state
     void* keepalive_timer;           // Таймер для отправки keepalive пакетов
     uint32_t keepalive_timeout;      // таймаут (ms)
+    uint16_t ka_period_ms;           // адаптивный период отправки keepalive (200→10000->200)
     uint8_t pkt_sent_since_keepalive; // Флаг: был ли отправлен пакет с последнего keepalive тика
     uint32_t keepalive_sent_count;  // Счётчик отправленных keepalive
     uint32_t keepalive_recv_count;  // Счётчик полученных keepalive