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实验3:OpenFlow协议分析实践

时间:2022-09-28 09:23:28浏览次数:48  
标签:struct OpenFlow 端口 实践 header ofp uint16 实验

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。

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。用抓包软件获取控制器与交换机之间的通信数据。

搭建拓扑、完成相关配置并实现主机与主机之间的 IP 通信
image
image

2.查看抓包结果
HELLO
控制器6633端口(我最高能支持OpenFlow 1.0) ---> 交换机53450端口
image

交换机53450端口(我最高能支持OpenFlow 1.5) ---> 控制器6633端口
image

FEATURES_REQUEST
控制器6633端口(我需要你的特征信息) ---> 交换机53450端口
image

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53450端口
image

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
image

FEATURES_REPLY
交换机53450端口(这是我的特征信息,请查收) ---> 控制器6633端口
image

PACKET_IN
交换机53450端口(有数据包进来,请指示)--->控制器6633端口
image

PACKET_OUT
控制器6633端口--->交换机53450端口(请按照我给你的action进行处理)
image

FLOW_MOD
分析抓取的flow_mod数据包,控制器通过6633端口向交换机53112端口、交换机53128端口下发流表项,指导数据的转发处理
image

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
image

3.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?
答:(Transmission Control Protocol)TCP协议
image

(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。

1.HELLO
image

/* Header on all OpenFlow packets. */
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. */
};

2.FEATURES_REQUEST
image

/* Header on all OpenFlow packets. */
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. */
};

3.SET_CONFIG
image

/* Header on all OpenFlow packets. */
/* Switch configuration. */
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. */
};

4.PORT_STATUS
image

/* 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;
};

5.FEATURES_REPLY
image

/* 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. */
};

6.PACKET_IN
image

/* Why is this packet being sent to the controller? */
enum ofp_packet_in_reason {
    OFPR_NO_MATCH,          /* No matching flow. */
    OFPR_ACTION             /* Action explicitly output to controller. */
};
 
/* Packet received on port (datapath -> controller). */
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. */
};

7.PACKET_OUT
image

/* Send packet (controller -> datapath). */
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.) */
};

8.FLOW_MOD
image

/* Flow setup and teardown (controller -> datapath). */
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. */
};

个人总结

1.在实验过程中,在打开wireshark后执行python文件,抓包过程中并没有找到FLOW_MOD,最后才发现不仅要执行python文件,还要执行pingall指令。
2.习到了运用 wireshark 对 OpenFlow 协议数据交互过程进行抓包的方法。熟悉了抓包、过滤数据包、查看包解析数据的操作。这次的实验更注重细心,难度不难。

标签:struct,OpenFlow,端口,实践,header,ofp,uint16,实验
From: https://www.cnblogs.com/031902208kqh/p/16736821.html

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