NMSettingLoopback
NMSetting * nm_setting_loopback_new (void);
void
guint32 nm_setting_loopback_get_mtu (NMSettingLoopback *setting);
NMSettingLoopback *setting
#define NM_SETTING_LOOPBACK_SETTING_NAME "loopback"
#define NM_SETTING_LOOPBACK_MTU "mtu"