diff --git a/src/nat_transport.c b/src/nat_transport.c
index 5157b04c..7d0fc3cf 100644
--- a/src/nat_transport.c
+++ b/src/nat_transport.c
@@ -47,11 +47,11 @@ static void nat_transport_client_tun_out_cb(struct ll_queue* q, void* arg) {
     queue_dgram_free(pkt); queue_entry_free(pkt);
     queue_resume_callback(q);
 
+    // Роутер принимает владение new_entry и dgram при любом результате, включая ошибку.
     int ret = etcp_route_send(inst, TOPO_GROUP_UTUN, tr->nat_via_node_id, new_entry, 0, 0);
     if (ret != 0) {
-        DEBUG_WARN(DEBUG_CATEGORY_NAT, "NAT client: etcp_route_send to provider %016llx failed",
-                   (unsigned long long)tr->nat_via_node_id);
-        queue_dgram_free(new_entry); queue_entry_free(new_entry);
+        DEBUG_WARN(DEBUG_CATEGORY_NAT, "NAT client: etcp_route_send to provider %016llx failed: error=%d ip_bytes=%zu",
+                   (unsigned long long)tr->nat_via_node_id, ret, ip_len);
     }
 }
 
@@ -89,11 +89,11 @@ static void nat_transport_provider_tun_out_cb(struct ll_queue* q, void* arg) {
     queue_dgram_free(pkt); queue_entry_free(pkt);
     queue_resume_callback(q);
 
+    // После передачи роутеру new_entry и dgram больше не принадлежат NAT, даже при ошибке.
     int send_ret = etcp_route_send(inst, TOPO_GROUP_UTUN, entry->src_node_id, new_entry, 0, 0);
     if (send_ret != 0) {
-        DEBUG_WARN(DEBUG_CATEGORY_NAT, "NAT provider: etcp_route_send back to node %016llx failed",
-                   (unsigned long long)entry->src_node_id);
-        queue_dgram_free(new_entry); queue_entry_free(new_entry);
+        DEBUG_WARN(DEBUG_CATEGORY_NAT, "NAT provider: etcp_route_send back to node %016llx failed: error=%d ip_bytes=%zu",
+                   (unsigned long long)entry->src_node_id, send_ret, ip_len);
     }
 }
 
diff --git a/tests/Makefile.am b/tests/Makefile.am
index 722c1ba0..9c7037d1 100644
--- a/tests/Makefile.am
+++ b/tests/Makefile.am
@@ -524,6 +524,9 @@ test_nat_engine_LDADD = $(LIBUTUN) $(COMMON_LIBS)
 test_nat_transport_SOURCES = test_nat_transport.c
 test_nat_transport_CFLAGS = -I$(top_srcdir)/src -I$(top_srcdir)/lib
 test_nat_transport_LDADD = $(LIBUTUN) $(CRYPTO_LIBS) $(COMMON_LIBS)
+if OS_LINUX
+test_nat_transport_LDFLAGS = -Wl,--wrap=etcp_route_send
+endif
 
 test_nat_stress_SOURCES = test_nat_stress.c
 test_nat_stress_CFLAGS = -I$(top_srcdir)/src -I$(top_srcdir)/lib
diff --git a/tests/test_nat_transport.c b/tests/test_nat_transport.c
index 72b79925..d914f095 100644
--- a/tests/test_nat_transport.c
+++ b/tests/test_nat_transport.c
@@ -43,6 +43,34 @@ static struct UASYNC* ua = NULL;
 static int test_timed_out = 0;
 static void* test_timeout_id = NULL;
 
+#ifdef __linux__
+/* Отказ с реальным освобождением в router API и успешный приём с тем же контрактом владения. */
+static int send_test_mode, send_test_calls, send_test_valid;
+static struct UTUN_INSTANCE* send_test_instance;
+static uint64_t send_test_destination;
+static size_t send_test_ip_len;
+
+int __real_etcp_route_send(struct UTUN_INSTANCE*, uint64_t, uint64_t, struct ll_entry*, int, int);
+int __wrap_etcp_route_send(struct UTUN_INSTANCE* inst, uint64_t group, uint64_t destination,
+                           struct ll_entry* entry, int force, int mode) {
+    if (!send_test_mode) return __real_etcp_route_send(inst, group, destination, entry, force, mode);
+    send_test_calls++;
+    if (inst != send_test_instance || group != TOPO_GROUP_UTUN || destination != send_test_destination ||
+        !entry || !entry->dgram || entry->len != send_test_ip_len + 1 || entry->dgram[0] != ETCP_RT_ID_NAT || force || mode) {
+        DEBUG_ERROR(DEBUG_CATEGORY_NAT, "Unexpected NAT send in ownership test: destination=%016llx call=%d",
+                    (unsigned long long)destination, send_test_calls);
+        send_test_valid = 0;
+    }
+    if (send_test_mode == 1) {
+        DEBUG_INFO(DEBUG_CATEGORY_NAT, "Inject NAT router refusal: packet ownership transfers on error");
+        // NULL instance вызывает отказ в реальном router API; переданный entry он освобождает сам.
+        return __real_etcp_route_send(NULL, group, destination, entry, force, mode);
+    }
+    queue_dgram_free(entry); queue_entry_free(entry);
+    return 0;
+}
+#endif
+
 static char temp_dir[] = "/tmp/utun_nat_transport_XXXXXX";
 static char config_provider[256];
 static char config_client[256];
@@ -431,6 +459,45 @@ static int test_provider_ingress_response(void) {
     return 1;
 }
 
+#ifdef __linux__
+static int test_send_failure_ownership(int provider) {
+    struct UTUN_INSTANCE* sender = provider ? inst_provider : inst_client;
+    struct tun_if* tun = sender->nat_tr.nat_tun;
+    struct eim_nat_entry saved = {0};
+    uint16_t external_port = inst_provider->nat.port_start;
+    if (provider) {
+        saved = inst_provider->nat.table[external_port];
+        inst_provider->nat.table[external_port] = (struct eim_nat_entry){.internal_ip = 0x0a0000cd,
+            .internal_port = htobe16(44444), .proto = IPPROTO_UDP_UINT8,
+            .state = EIM_NAT_ENTRY_ACTIVE, .src_node_id = g_client_node_id};
+    }
+    size_t ip_len;
+    uint8_t* ip = provider ? build_udp_pkt(0x08080808, 80, inst_provider->nat.gateway_ip, external_port, &ip_len) :
+        build_udp_pkt(0x0a0000cd, 44444, 0x08080808, 80, &ip_len);
+    send_test_instance = sender;
+    send_test_destination = provider ? g_client_node_id : g_provider_node_id;
+    send_test_ip_len = ip_len;
+    send_test_calls = 0; send_test_valid = 1;
+    send_test_mode = 2;
+    // Прогреть пул entry до измерения живых блоков; исходный IP остаётся у вызывающего.
+    int ok = tun_inject_packet(tun, ip, ip_len) == 0 && send_test_calls == 1;
+    size_t baseline = u_get_allocated_count();
+    send_test_mode = 1;
+    if (tun_inject_packet(tun, ip, ip_len) != 0 || send_test_calls != 2 || u_get_allocated_count() != baseline) ok = 0;
+    send_test_mode = 2;
+    if (tun_inject_packet(tun, ip, ip_len) != 0 || send_test_calls != 3 || u_get_allocated_count() != baseline) ok = 0;
+    if (!send_test_valid || queue_entry_count(tun->output_queue)) ok = 0;
+    send_test_mode = 0; send_test_instance = NULL;
+    free(ip);
+    if (provider) inst_provider->nat.table[external_port] = saved;
+    if (ok) DEBUG_INFO(DEBUG_CATEGORY_NAT, "PASS NAT %s send failure: no double free/leak, next packet accepted",
+                       provider ? "provider" : "client");
+    else DEBUG_ERROR(DEBUG_CATEGORY_NAT, "FAIL NAT %s send failure: calls=%d valid=%d live_blocks=%zu baseline=%zu",
+                     provider ? "provider" : "client", send_test_calls, send_test_valid, u_get_allocated_count(), baseline);
+    return ok;
+}
+#endif
+
 static int test_full_roundtrip(void) {
     /* Полный путь через client socketpair → ETCP → provider TUN и обратно. */
     DEBUG_INFO(DEBUG_CATEGORY_NAT, "=== test_full_roundtrip ===");
@@ -563,6 +630,11 @@ int main(void) {
     total++; if (test_init_destroy()) passed++; else DEBUG_ERROR(DEBUG_CATEGORY_NAT, "FAIL: init_destroy");
     total++; if (test_provider_egress()) passed++; else DEBUG_ERROR(DEBUG_CATEGORY_NAT, "FAIL: provider_egress");
     total++; if (test_provider_ingress_response()) passed++; else DEBUG_ERROR(DEBUG_CATEGORY_NAT, "FAIL: provider_ingress");
+#ifdef __linux__
+    total++; if (test_send_failure_ownership(0)) passed++; else DEBUG_ERROR(DEBUG_CATEGORY_NAT, "FAIL: client send ownership");
+    total++; if (test_send_failure_ownership(1)) passed++; else DEBUG_ERROR(DEBUG_CATEGORY_NAT, "FAIL: provider send ownership");
+#endif
+    // Реальная доставка после инъекций проверяет восстановление обеих веток без перезапуска NAT.
     total++; if (test_full_roundtrip()) passed++; else DEBUG_ERROR(DEBUG_CATEGORY_NAT, "FAIL: full_roundtrip");
 
     printf("\n=== NAT Transport Tests: %d/%d passed ===\n", passed, total);