标签：struct OpenFlow 实践 uint32 header ofp uint16 实验 port

实验3：OpenFlow协议分析实践

一、实验目的

能够运用 wireshark 对 OpenFlow 协议数据交互过程进行抓包；
能够借助包解析工具，分析与解释 OpenFlow协议的数据包交互过程与机制。

二、实验环境

Ubuntu 20.04 Desktop amd64

三、实验要求

（一）基本要求

搭建下图所示拓扑，完成相关 IP 配置，并实现主机与主机之间的 IP 通信。用抓包软件获取控制器与交换机之间的通信数据。

查看抓包结果。

hello
控制器6633端口->交换机42206端口

交换机42206端口->控制器6633端口

Feature Request
控制器6633端口（我需要你的特征信息） ---> 交换机42206端口

Set Config
控制器6633端口（请按照我给你的flag和max bytes of packet进行配置） ---> 交换机42206端口

Port_Status
当交换机端口发生变化时，告知控制器相应的端口状态。

Features Reply
交换机端口42206（这是我的特征信息，请查收） ---> 控制器6633端口

Packet_In

Flow_Mod

Packet_Out

分析OpenFlow协议中交换机与控制器的消息交互过程，画出相关交互图或流程图。

回答问题：交换机与控制器建立通信时是使用TCP协议还是UDP协议？

TCP

（二）进阶要求

将抓包基础要求第2步的抓包结果对照OpenFlow源码，了解OpenFlow主要消息类型对应的数据结构定义。
hello

struct ofp_header {    
  uint8_t version;    /* OFP_VERSION. */    
  uint8_t type;       /* One of the OFPT_ constants. */    
  uint16_t length;    /* Length including this ofp_header. */    
  uint32_t xid;       
/* Transaction id associated with this packet.                             
Replies use the same id as was in the request to facilitate pairing. 
*/}; 
struct ofp_hello {    
  struct ofp_header header;
};

Features Request

Set Config

struct ofp_switch_config
{
    struct ofp_header header;
    uint16_t flags;             /* OFPC_* flags. */
    uint16_t miss_send_len;     /* Max bytes of new flow that datapath should
                                   send to the controller. */
};

Port_Status

/* A physical port has changed in the datapath */
  struct ofp_port_status {    
  struct ofp_header header;    
  uint8_t reason;          /* One of OFPPR_*. */    
  uint8_t pad[7];          /* Align to 64-bits. */    
  struct ofp_phy_port desc;
};

Features Reply

struct ofp_switch_features {   
  struct ofp_header header;    
  uint64_t datapath_id;   
/* Datapath unique ID.  The lower 48-bits are for a MAC address, while the upper 16-bits are implementer-defined. */     
  uint32_t n_buffers;     /* Max packets buffered at once. */     
  uint8_t n_tables;       /* Number of tables supported by datapath. */    
  uint8_t pad[3];         /* Align to 64-bits. */     /* Features. */    
  uint32_t capabilities;  /* Bitmap of support "ofp_capabilities". */    
  uint32_t actions;       /* Bitmap of supported "ofp_action_type"s. */     /* Port info.*/    

struct ofp_phy_port ports[0];  /* Port definitions.  The number of ports                                      is inferred from the length field in the header. */};
/* Description of a physical port */
struct ofp_phy_port { 
  uint16_t port_no;    
  uint8_t hw_addr[OFP_ETH_ALEN];    
  char name[OFP_MAX_PORT_NAME_LEN]; /* Null-terminated */     
  uint32_t config;        /* Bitmap of OFPPC_* flags. */    
  uint32_t state;         /* Bitmap of OFPPS_* flags. */     
/* Bitmaps of OFPPF_* that describe features.  All bits zeroed if  * unsupported or unavailable. */    
  uint32_t curr;          /* Current features. */    
  uint32_t advertised;    /* Features being advertised by the port. */    
  uint32_t supported;     /* Features supported by the port. */    
  uint32_t peer;          /* Features advertised by peer. */
 };