实验3：OpenFlow协议分析实践

实验3：OpenFlow协议分析实践

一、实验目的

1. 能够运用 wireshark 对 OpenFlow 协议数据交互过程进行抓包；
2. 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

1、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。

主机	IP地址
h1	192.168.0.101/24
h2	192.168.0.102/24
h3	192.168.0.103/24
h4	192.168.0.104/24

ip和拓扑

2、查看抓包结果，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。

HELLO

控制器6633端口（我最高能支持OpenFlow 1.0） ---> 交换机34108端口

 

 

 

 

 

 

交换机34108端口（我最高能支持OpenFlow 1.5） ---> 控制器6633端口

 

 

 

 

 

 

 

 于是双方建立连接，并使用OpenFlow 1.0

FEATURES_REQUEST

控制器6633端口（我需要你的特征信息） ---> 交换机34108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34108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34108端口（这是我的特征信息，请查收） ---> 控制器6633端口

 

 

 

PACKET_IN

交换机34108端口（有数据包进来，请指示）--->控制器6633端口 

 

 

 

PACKET_OUT

控制器6633端口--->交换机34108端口（请按照我给你的action进行处理） 

 

 

 

FLOW_MOD

分析抓取的flow_mod数据包，控制器通过6633端口向交换机34108端口下发流表项，指导数据的转发处理  

 

 

 

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？
使用TCP协议

进阶要求：

• OFPT_HELLO
  • 

  •         /* OFPT_HELLO.  This message has an empty body, but implementations must
             * ignore any data included in the body, to allow for future extensions. */
            struct ofp_hello {
                struct ofp_header header;
            };
    

• OFPT_FEATURES_REQUEST

  •       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;
      };
    

• OFPT_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. */
      };
    

• OFPT_PORT_STATUS
  • 

  •   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;
      };
    

• OFPT_FEATURES_REPLY
  • 

  •         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. */
        };
    
        /* Switch features. */
        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. */
        };
    

• OFPT_PACKET_IN
  • 

  •   struct ofp_header header;
      uint32_t buffer_id;     /* ID assigned by datapath. */
      uint16_t total_len;     /* Full length of frame. */
      uint16_t in_port;       /* Port on which frame was received. */
      uint8_t reason;         /* Reason packet is being sent (one of OFPR_*) */
      uint8_t pad;
      uint8_t data[0];        /* Ethernet frame, halfway through 32-bit word,
                                 so the IP header is 32-bit aligned.  The
                                 amount of data is inferred from the length
                                 field in the header.  Because of padding,
                                 offsetof(struct ofp_packet_in, data) ==
                                 sizeof(struct ofp_packet_in) - 2. */
    };
    

• OFPT_PACKET_OUT
  • 

  •     struct ofp_packet_out {
            struct ofp_header header;
            uint32_t buffer_id;           /* ID assigned by datapath (-1 if none). */
            uint16_t in_port;             /* Packet's input port (OFPP_NONE if none). */
            uint16_t actions_len;         /* Size of action array in bytes. */
            struct ofp_action_header actions[0]; /* Actions. */
            /* uint8_t data[0]; */        /* Packet data.  The length is inferred
                                             from the length field in the header.
                                             (Only meaningful if buffer_id == -1.) */
        };
    

• OFPT_FLOW_MOD
  • 

  •       struct ofp_header header;
          struct ofp_match match;      /* Fields to match */
          uint64_t cookie;             /* Opaque controller-issued identifier. */
    
          /* Flow actions. */
          uint16_t command;             /* One of OFPFC_*. */
          uint16_t idle_timeout;        /* Idle time before discarding (seconds). */
          uint16_t hard_timeout;        /* Max time before discarding (seconds). */
          uint16_t priority;            /* Priority level of flow entry. */
          uint32_t buffer_id;           /* Buffered packet to apply to (or -1).
                                           Not meaningful for OFPFC_DELETE*. */
          uint16_t out_port;            /* For OFPFC_DELETE* commands, require
                                           matching entries to include this as an
                                           output port.  A value of OFPP_NONE
                                           indicates no restriction. */
          uint16_t flags;               /* One of OFPFF_*. */
          struct ofp_action_header actions[0]; /* The action length is inferred
                                                  from the length field in the
                                                  header. */
      };
      struct ofp_action_header {
          uint16_t type;                  /* One of OFPAT_*. */
          uint16_t len;                   /* Length of action, including this
                                             header.  This is the length of action,
                                             including any padding to make it
                                             64-bit aligned. */
          uint8_t pad[4];
      };
    
    

心得体会

本次实验难度虽说不大，但仍令我受益匪浅，通过抓包，我进一步了解了在tcp协议下，两个端口通信间的交流方式。
在一开始抓包的时候，我只用openflow_v1时找不到34108对6633端口发送的hello，后来根据提示，我改用openflow_v6成功获取了信息。
在查找FLOW_MOD的时候，由于我一开始没有pingall，故没有找到相应抓包，后来通过询问同学了解了问题的所在
在查找对应源码时，根据对源码的解读让我更加深刻的了解了其深层原理，给我幼小的心灵产生了巨大的冲击。