Triggering RPC error for all handlers on port close.

This is required to avoid crashes and memory leaks on Unit exit.

src/nxt_port_rpc.c

@@ -461,3 +461,41 @@ nxt_port_rpc_cancel(nxt_task_t *task, nxt_port_t *port, uint32_t stream)
 
     nxt_port_use(task, port, -1);
 }
+
+static nxt_buf_t  nxt_port_close_dummy_buf;
+
+void
+nxt_port_rpc_close(nxt_task_t *task, nxt_port_t *port)
+{
+    nxt_lvlhsh_each_t    lhe;
+    nxt_port_rpc_reg_t   *reg;
+    nxt_port_recv_msg_t  msg;
+
+    for ( ;; ) {
+        nxt_memzero(&lhe, sizeof(nxt_lvlhsh_each_t));
+
+        lhe.proto = &lvlhsh_rpc_reg_proto;
+
+        reg = nxt_lvlhsh_each(&port->rpc_streams, &lhe);
+        if (reg == NULL) {
+            return;
+        }
+
+        msg.fd = -1;
+        msg.buf = &nxt_port_close_dummy_buf;
+        msg.port = port;
+        msg.port_msg.stream = reg->stream;
+        msg.port_msg.pid = nxt_pid;
+        msg.port_msg.type = _NXT_PORT_MSG_RPC_ERROR;
+        msg.port_msg.last = 1;
+        msg.port_msg.mmap = 0;
+        msg.port_msg.nf = 0;
+        msg.port_msg.mf = 0;
+        msg.port_msg.tracking = 0;
+        msg.size = sizeof(msg.port_msg);
+        msg.cancelled = 0;
+        msg.u.data = NULL;
+
+        nxt_port_rpc_handler(task, &msg);
+    }
+}