fix(exec): set initial console size before nsenter exec

The child's slave.set_size({}) after setsid was a no-op
(/dev/tty == slave, reads 0x0 writes 0x0) so the pty stayed at
0x0 until the first SIGWINCH. Drop it and only set size when
consoleSize is given. On the parent side, after receiving the
master fd, resize it from the host terminal before attaching
(unless consoleSize was set). Accept the small race window:
the parent's single ioctl lands within the child's
send_fd→execvpe window in practice.

Signed-off-by: Yuming He <ComixHe1895@outlook.com>

Author: ComixHe

src/linyaps_box/container_ref.cpp

@@ -69,7 +69,10 @@ auto linyaps_box::container_ref::exec(exec_container_option option) -> int
             auto [master, slave] = create_pty_pair();
 
             slave.setup_stdio();
-            slave.set_size({ });
+            if (option.proc.console_size) {
+                slave.set_size({ option.proc.console_size->height,
+                                 option.proc.console_size->width, 0, 0 });
+            }
 
             option.console_socket->send_fd(std::move(master).take());
             option.console_socket.reset();
@@ -147,10 +150,8 @@ auto linyaps_box::container_ref::exec(exec_container_option option) -> int
         }
     });
 
-    [&recv_socketpair, &monitor, &in, &out, &changed]() {
-        if (!recv_socketpair) {
-            return;
-        }
+    if (recv_socketpair) {
+        monitor.acquire_host_tty(in, out);
 
         LINYAPS_BOX_DEBUG() << "Container requires a terminal";
 
@@ -159,12 +160,16 @@ auto linyaps_box::container_ref::exec(exec_container_option option) -> int
 
         recv_socketpair->release();
 
+        if (!option.proc.console_size) {
+            master.resize(monitor.host_tty_size());
+        }
+
         in.set_nonblock(true);
         out.set_nonblock(true);
         changed = true;
 
-        monitor.enable_io_forwarding(std::move(master), in, out);
-    }();
+        monitor.attach_terminal(std::move(master), in, out);
+    }
 
     return monitor.wait_container_exit();
 }