consume_skb 和 kfree_skb的區別

consume_skb 表示 skb是正常釋放。

kfree_skb 表示因爲某種錯誤報文被丟棄。

這隻會帶來某些網絡統計數據上的區別，例如使用drop_watch查看有多少異常丟包的時候。

通過源碼上也可以看到，兩者實現基本一致，除了調用不同的統計分析函數：

trace_consume_skb, trace_kfree_skb

/**
 *	consume_skb - free an skbuff
 *	@skb: buffer to free
 *
 *	Drop a ref to the buffer and free it if the usage count has hit zero
 *	Functions identically to kfree_skb, but kfree_skb assumes that the frame
 *	is being dropped after a failure and notes that
 */
void consume_skb(struct sk_buff *skb)
{
	if (unlikely(!skb))
		return;
	if (likely(atomic_read(&skb->users) == 1))
		smp_rmb();
	else if (likely(!atomic_dec_and_test(&skb->users)))
		return;
	trace_consume_skb(skb);
	__kfree_skb(skb);
}
EXPORT_SYMBOL(consume_skb);


/**
 *	kfree_skb - free an sk_buff
 *	@skb: buffer to free
 *
 *	Drop a reference to the buffer and free it if the usage count has
 *	hit zero.
 */
void kfree_skb(struct sk_buff *skb)
{
	if (unlikely(!skb))
		return;
	if (likely(atomic_read(&skb->users) == 1))
		smp_rmb();
	else if (likely(!atomic_dec_and_test(&skb->users)))
		return;
	trace_kfree_skb(skb, __builtin_return_address(0));
	__kfree_skb(skb);
}
EXPORT_SYMBOL(kfree_skb);