【OVS2.5.0源码分析】datapath之action分析（8）

one_clouder

于 2016-09-06 22:01:40 发布

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分类专栏： OVS2.5.0源码分析文章标签： OVS openvswitch 网络 sample

本文链接：https://blog.youkuaiyun.com/one_clouder/article/details/52453931

本文聚焦于OpenvSwitch 2.5.0的源码分析，详细探讨了datapath模块中action的sample处理函数，揭示了OVS ACTION_ATTR_SAMPLE的工作原理。

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本篇分析OVS_ACTION_ATTR_SAMPLE action的处理函数sample。

1、sample函数

static int sample(struct datapath *dp, struct sk_buff *skb,
		  struct sw_flow_key *key, const struct nlattr *attr,
		  const struct nlattr *actions, int actions_len)
{
	const struct nlattr *acts_list = NULL;
	const struct nlattr *a;
	int rem;

	for (a = nla_data(attr), rem = nla_len(attr); rem > 0;
		 a = nla_next(a, &rem)) {
		u32 probability;

		switch (nla_type(a)) {
		case OVS_SAMPLE_ATTR_PROBABILITY:		//提供概率设置
			probability = nla_get_u32(a);
			if (!probability || prandom_u32() > probability)
				return 0;
			break;

		case OVS_SAMPLE_ATTR_ACTIONS:		//提供对采样报文的处理
			acts_list = a;
			break;
		}
	}

	rem = nla_len(acts_list);
	a = nla_data(acts_list);

	/* Actions list is empty, do nothing */
	if (unlikely(!rem))
		return 0;

	/* The only known usage of sample action is having a single user-space
	 * action. Treat this usage as

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