openflow协议分析实践

实验目的

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

实验环境

Ubuntu 20.04 Desktop amd64

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。用
      抓包软件获取控制器与交换机之间的通信数据包。
    1. 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。
    1. 回答：交换机与控制器建立通信时是使用TCP协议还是UDP协议？
  • hello
    控制器6633端口（我最高能支持OpenFlow 1.0） ---> 交换机36744端口
  • 交换机36744端口（我最高能支持OpenFlow 1.3） ---> 控制器6633端口

于是双方建立连接，并使用OpenFlow 1.0

  • Features Request / Set Conig
    控制器6633端口（我需要你的特征信息） ---> 交换机36744端口

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36744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36744端口（这是我的特征信息，请查收） ---> 控制器6633端口

  • Packet_in
    有两种情况：
    • 交换机查找流表，发现没有匹配条目时
    • 有匹配条目但是对应的action是OUTPUT=CONTROLLER时
    交换机36752端口（有数据包进来，请指示）--- 控制器6633端口

  • Flow_mod
    分析抓取的flow_mod数据包，控制器通过6633端口向交换机36752端口、交换机36752端口
    下发流表项，指导数据的转发处理

Flow_mod
分析抓取的flow_mod数据包，控制器通过6633端口向交换机36752端口、交换机36752端口
下发流表项，指导数据的转发处理

  • Packet_out
    控制器6633端口（请按照我给你的action进行处理） ---> 交换机36752端口
  1. 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. */
};
/* 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;
};
  1. Features Request
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. */
};
  1. 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. */
};
  1. Port_Status
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. */
};
  1. 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. */
};
  1. Packet_in
struct ofp_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. */
};
  1. Flow_mod
struct ofp_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. */
};
  1. 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.) */
};

总结

  1. 建立拓扑前要先开启抓包工具，一开始没有开启导致hello找不到
  2. 相关数据结构可在openflow安装目录openflow/include/openflow当中的openflow.h头文件中查询到
  3. flow_mod要进行pingall才会出现，之前没有pingall找不到mod
  4. 经过本次实验，对抓包工具运用更加熟练，对openflow协议更进一步了解
posted @ 2022-10-06 11:18  smilecomzyb  阅读(22)  评论(0)  编辑  收藏  举报