网络数据包发送之dev_hard_start_xmit

本文主要是介绍网络数据包发送之dev_hard_start_xmit，希望对大家解决编程问题提供一定的参考价值，需要的开发者们随着小编来一起学习吧！

int dev_hard_start_xmit(struct sk_buff *skb, struct net_device *dev,
struct netdev_queue *txq)
{
const struct net_device_ops *ops = dev->netdev_ops;
int rc = NETDEV_TX_OK;
unsigned int skb_len;

	/* 检查上层协议是否已经完成了数据包分片的工作？ */
if (likely(!skb->next)) {
netdev_features_t features;
/*
* If device doesn't need skb->dst, release it right now while
* its hot in this cpu cache
*/
if (dev->priv_flags & IFF_XMIT_DST_RELEASE)
skb_dst_drop(skb);
features = netif_skb_features(skb);

		/* 上层协议要求驱动进行VLAN插入加速，但是当前网络设备不支持该功能时，则需要手动完成数据包的VLAN字段插入 */
if (vlan_tx_tag_present(skb) &&
!vlan_hw_offload_capable(features, skb->vlan_proto)) {
skb = __vlan_put_tag(skb, skb->vlan_proto,
vlan_tx_tag_get(skb));
if (unlikely(!skb))
goto out;

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