文章目录
前言
本文介绍dpdk flow api的简单使用。
dpdk flow 的使用过程和 iptables 差不多。即，数据包匹配上指定的规则后，执行对应的动作。
本文示例代码来自Basic RTE Flow Filtering Sample Application。
这篇内容还是"水"了点。随手笔记吧。
基本概念
总的来说：dpdk flow 可以对数据包的协议头等进行匹配。可能执行的动作是丢弃流量，将流量转移到指定队列等。
dpdk flow 有这些基本概念：
Attributes: 数据流规则的属性，如其方向（入口或出口）和优先级。(这里面还有个group属性。 group 0是默认必经过的。如果想到其他group，需要执行JUMP操作。其他group中有不同的action。这些group可能被物理设备支持，或者以虚拟的方式支持。示例代码中没有显示使用group，可以暂时不管)Pattern item: 描述匹配的样式。即，什么样的包会命中样式。Actions: 当数据包与样式匹配时，执行的操作。
示例代码说明
下面这个示例代码来自"前言"中的链接。含义是，当port_id端口进入的数据包，满足src_ip/mask -> dst_ip/mask的pattern时，将其转移到rx_q队列上。
代码还是比较简单的。我简单介绍下。
Attributes在dpdk中的结构体是rte_flow_attr。attr.ingress = 1;表示 Pattern 将应用在入站流量上。Pattern在dpdk中的结构是rte_flow_item。代码中填充了一个src_ip/mask -> dst_ip/mask样式。Actions在dpdk中的结构是rte_flow_action。代码中填充了一个将流量转移到指定队列的动作。- 相关函数：
rte_flow_create则是在指定端口上,创建一个flow rule。
c
/**
* create a flow rule that sends packets with matching src and dest ip
* to selected queue.
*
* @param port_id
* The selected port.
* @param rx_q
* The selected target queue.
* @param src_ip
* The src ip value to match the input packet.
* @param src_mask
* The mask to apply to the src ip.
* @param dest_ip
* The dest ip value to match the input packet.
* @param dest_mask
* The mask to apply to the dest ip.
* @param[out] error
* Perform verbose error reporting if not NULL.
*
* @return
* A flow if the rule could be created else return NULL.
*/
/* Function responsible for creating the flow rule. 8< */
struct rte_flow *generate_ipv4_flow(uint16_t port_id, uint16_t rx_q,
uint32_t src_ip, uint32_t src_mask,
uint32_t dest_ip, uint32_t dest_mask,
struct rte_flow_error *error) {
/* Declaring structs being used. 8< */
struct rte_flow_attr attr;
struct rte_flow_item pattern[MAX_PATTERN_NUM];
struct rte_flow_action action[MAX_ACTION_NUM];
struct rte_flow *flow = NULL;
struct rte_flow_action_queue queue = {.index = rx_q};
struct rte_flow_item_ipv4 ip_spec;
struct rte_flow_item_ipv4 ip_mask;
/* >8 End of declaring structs being used. */
int res;
memset(pattern, 0, sizeof(pattern));
memset(action, 0, sizeof(action));
/* Set the rule attribute, only ingress packets will be checked. 8< */
memset(&attr, 0, sizeof(struct rte_flow_attr));
attr.ingress = 1;
/* >8 End of setting the rule attribute. */
/*
* create the action sequence.
* one action only, move packet to queue
*/
action[0].type = RTE_FLOW_ACTION_TYPE_QUEUE;
action[0].conf = &queue;
action[1].type = RTE_FLOW_ACTION_TYPE_END;
/*
* set the first level of the pattern (ETH).
* since in this example we just want to get the
* ipv4 we set this level to allow all.
*/
/* Set this level to allow all. 8< */
pattern[0].type = RTE_FLOW_ITEM_TYPE_ETH;
/* >8 End of setting the first level of the pattern. */
/*
* setting the second level of the pattern (IP).
* in this example this is the level we care about
* so we set it according to the parameters.
*/
/* Setting the second level of the pattern. 8< */
memset(&ip_spec, 0, sizeof(struct rte_flow_item_ipv4));
memset(&ip_mask, 0, sizeof(struct rte_flow_item_ipv4));
ip_spec.hdr.dst_addr = htonl(dest_ip);
ip_mask.hdr.dst_addr = dest_mask;
ip_spec.hdr.src_addr = htonl(src_ip);
ip_mask.hdr.src_addr = src_mask;
pattern[1].type = RTE_FLOW_ITEM_TYPE_IPV4;
pattern[1].spec = &ip_spec;
pattern[1].mask = &ip_mask;
/* >8 End of setting the second level of the pattern. */
/* The final level must be always type end. 8< */
pattern[2].type = RTE_FLOW_ITEM_TYPE_END;
/* >8 End of final level must be always type end. */
/* Validate the rule and create it. 8< */
res = rte_flow_validate(port_id, &attr, pattern, action, error);
if (!res)
flow = rte_flow_create(port_id, &attr, pattern, action, error);
/* >8 End of validation the rule and create it. */
return flow;
}
/* >8 End of function responsible for creating the flow rule. */最后
我们现在已经了解了 dpdk flow 最简单的使用了。难度大概是 "1+1=2"。
如果想要在日常工作中使用dpdk flow, 难度大概是解二元一次方程，需要看更多的示例代码。