net/tun: Support changing carrier state of TUN/TAP

Add TUNSETCARRIER ioctl, then we may change the carrier state of TUN dynamically. Note that we don't need an ioctl for getting carrier, it can be done by SIOCGIFFLAGS already.

Ref: https://github.com/torvalds/linux/blob/v6.10/drivers/net/tun.c#L3374-L3380

Signed-off-by: Zhe Weng <wengzhe@xiaomi.com>

drivers/net/tun.c

@@ -1268,6 +1268,24 @@ static int tun_ioctl(FAR struct file *filep, int cmd, unsigned long arg)
 
       return OK;
     }
+  else if (cmd == TUNSETCARRIER)
+    {
+      if (priv == NULL || arg == 0)
+        {
+          return -EINVAL;
+        }
+
+      if (*(FAR int *)((uintptr_t)arg))
+        {
+          netdev_carrier_on(&priv->dev);
+        }
+      else
+        {
+          netdev_carrier_off(&priv->dev);
+        }
+
+      return OK;
+    }
 
   return -ENOTTY;
 }

include/nuttx/net/ioctl.h

@@ -107,6 +107,7 @@
 
 #define TUNSETIFF        _SIOC(0x0028)  /* Set TUN/TAP interface */
 #define TUNGETIFF        _SIOC(0x0035)  /* Get TUN/TAP interface */
+#define TUNSETCARRIER    _SIOC(0x0040)  /* Set TUN/TAP carrier state */
 
 /* Telnet driver ************************************************************/