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ovs概览

1 简介

之前的工作对ovs应用层比较熟悉，但没有看过ovs的源码，所以这里大概瞄了一眼，宏观的一些记录。

2 基本数据结构

2.1 端口结构体

struct vport {
  struct net_device *dev;
  struct datapath *dp;
  struct vport_portids __rcu *upcall_portids;
  u16 port_no;

  struct hlist_node hash_node;
  struct hlist_node dp_hash_node;
  const struct vport_ops *ops;

  struct list_head detach_list;
  struct rcu_head rcu;
};

2.2 数据面：datapath

struct datapath {
  struct rcu_head rcu;
  struct list_head list_node;

  /* Flow table. */
  struct flow_table table;

  /* Switch ports. */
  struct hlist_head *ports;

  /* Stats. */
  struct dp_stats_percpu __percpu *stats_percpu;

  /* Network namespace ref. */
  possible_net_t net;

  u32 user_features;

  u32 max_headroom;
};

2.3 flow table

struct flow_table {
  struct table_instance __rcu *ti;
  struct table_instance __rcu *ufid_ti;
  struct mask_cache_entry __percpu *mask_cache;
  struct mask_array __rcu *mask_array;
  unsigned long last_rehash;
  unsigned int count;
  unsigned int ufid_count;
};

2.4 flow key

参见ovs-2.8.1/datapath/flow.h:68

2.5 规则

参见ovs-2.8.1/ofproto/ofproto-provider.h:351

2.6 action

struct rule_actions {
    /* Flags.
     *
     * 'has_meter' is true if 'ofpacts' contains an OFPACT_METER action.
     *
     * 'has_learn_with_delete' is true if 'ofpacts' contains an OFPACT_LEARN
     * action whose flags include NX_LEARN_F_DELETE_LEARNED. */
    bool has_meter;
    bool has_learn_with_delete;
    bool has_groups;

    /* Actions. */
    uint32_t ofpacts_len;         /* Size of 'ofpacts', in bytes. */
    struct ofpact ofpacts[];      /* Sequence of "struct ofpacts". */
};

3 收发流程

挂到kernel上，注册对应函数，来一个报文时ovs的入口函数为： int ovs_vport_receive(struct vport *vport, struct sk_buff *skb, const struct ip_tunnel_info *tun_info) 后续会继续调用=void ovs_dp_process_packet(struct sk_buff *skb, struct sw_flow_key *key)= 这里会看到生成flow表的key，查表，send等所有细节。

对应的发送函数为： void ovs_vport_send(struct vport *vport, struct sk_buff *skb, u8 mac_proto)

3.1 flow action process

static int do_execute_actions(struct datapath *dp, struct sk_buff *skb,
            struct sw_flow_key *key,
            const struct nlattr *attr, int len)

最常见的output action

static void do_output(struct datapath *dp, struct sk_buff *skb, int out_port,
          struct sw_flow_key *key)

action的drop是作为默认处理的，在定义的如下enum中没有drop！如果这些都没有，程序跳入最后一行free skbbuff那里。

enum ovs_action_attr {
  OVS_ACTION_ATTR_UNSPEC,
  OVS_ACTION_ATTR_OUTPUT,       /* u32 port number. */
  OVS_ACTION_ATTR_USERSPACE,    /* Nested OVS_USERSPACE_ATTR_*. */
...

4 flow消失

有三种方式：

  1. 通过Remote Controller直接发送移除Flow Entry的消息，通过Openflow来做，这个没得说
  2. 通过OpenFlow Switch的过期机制， hard_timeout, idle_timeout在flow里看见过的，
  3. OpenFlow Switch的逐出机制，当OpenFlow Switch需要回收资源时，会行使这一权限，这个倒是很少见。

5 保留端口信息

//ovs-2.8.1/include/openflow/openflow-1.0.h:29
/* Port number(s)   meaning
 * ---------------  --------------------------------------
 * 0x0000           not assigned a meaning by OpenFlow 1.0
 * 0x0001...0xfeff  "physical" ports
 * 0xff00...0xfff6  "reserved" but not assigned a meaning by OpenFlow 1.x
 * 0xfff7...0xffff  "reserved" OFPP_* ports with assigned meanings
 */

/* Ranges. */
#define OFPP_MAX        OFP_PORT_C(0xff00) /* Max # of switch ports. */
#define OFPP_FIRST_RESV OFP_PORT_C(0xfff7) /* First assigned reserved port. */
#define OFPP_LAST_RESV  OFP_PORT_C(0xffff) /* Last assigned reserved port. */

/* Reserved output "ports". */
#define OFPP_UNSET      OFP_PORT_C(0xfff7) /* For OXM_OF_ACTSET_OUTPUT only. */
#define OFPP_IN_PORT    OFP_PORT_C(0xfff8) /* Where the packet came in. */
#define OFPP_TABLE      OFP_PORT_C(0xfff9) /* Perform actions in flow table. */
#define OFPP_NORMAL     OFP_PORT_C(0xfffa) /* Process with normal L2/L3. */
#define OFPP_FLOOD      OFP_PORT_C(0xfffb) /* All ports except input port and
                                            * ports disabled by STP. */
#define OFPP_ALL        OFP_PORT_C(0xfffc) /* All ports except input port. */
#define OFPP_CONTROLLER OFP_PORT_C(0xfffd) /* Send to controller. */
#define OFPP_LOCAL      OFP_PORT_C(0xfffe) /* Local openflow "port". */
#define OFPP_NONE       OFP_PORT_C(0xffff) /* Not associated with any port. */

6 参考

  1. http://blog.csdn.net/yuzhihui_no1/article/details/39298321
  2. http://www.cnblogs.com/CasonChan/p/4613812.html