在bond初始化的时候，我们可以看到如下属性：
/* don‘t acquire bond device‘s netif_tx_lock when transmitting */
bond_dev->features |= NETIF_F_LLTX;
在lo口设置的时候，也可以看到这个属性：
static void loopback_setup(struct net_device *dev){ ???dev->mtu ???????= 64 * 1024; ???dev->hard_header_len ???= ETH_HLEN; ???/* 14 ???*/ ???dev->addr_len ???????= ETH_ALEN; ???/* 6 ???*/ ???dev->type ???????= ARPHRD_LOOPBACK; ???/* 0x0001*/ ???dev->flags ???????= IFF_LOOPBACK; ???dev->priv_flags ???????|= IFF_LIVE_ADDR_CHANGE | IFF_NO_QUEUE; ???netif_keep_dst(dev); ???dev->hw_features ???= NETIF_F_GSO_SOFTWARE; ???dev->features ????????= NETIF_F_SG | NETIF_F_FRAGLIST ???????| NETIF_F_GSO_SOFTWARE ???????| NETIF_F_HW_CSUM ???????| NETIF_F_RXCSUM ???????| NETIF_F_SCTP_CRC ???????| NETIF_F_HIGHDMA ???????| NETIF_F_LLTX ???????| NETIF_F_NETNS_LOCAL ???????| NETIF_F_VLAN_CHALLENGED ???????| NETIF_F_LOOPBACK; ???dev->ethtool_ops ???= &loopback_ethtool_ops; ???dev->header_ops ???????= ð_header_ops; ???dev->netdev_ops ???????= &loopback_ops; ???dev->destructor ???????= loopback_dev_free;}NETIF_F_LLTX 属性代表的是，我们在发包的时候，不需要获取锁。
而对于非虚拟设备，如实际网卡，则这个属性一般是不设置的，也就是需要获取TX的锁。
不过，也有注释说后面的驱动最好不要用这个特性：
* LLTX driver (deprecated for hardware drivers)NETIF_F_LLTX should be set in drivers that implement their own locking intransmit path or don‘t need locking at all (e.g. software tunnels).In ndo_start_xmit, it is recommended to use a try_lock and returnNETDEV_TX_LOCKED when the spin lock fails. ?The locking should also properlyprotect against other callbacks (the rules you need to find out).Don‘t use it for new drivers.
NETIF_F_LLTX 的属性
原文地址：https://www.cnblogs.com/10087622blog/p/9571055.html