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实验3:OpenFlow协议分析实践

时间:2022-09-27 17:59:06浏览次数:37  
标签:struct OpenFlow 实践 uint32 header ofp uint16 实验 port

实验3:OpenFlow协议分析实践

(一)基本要求

1、 拓扑


2、 抓包

(1) hello

控制器 对交换机 发个hello 确认下

我这个openflow 1.0 交换机端口 51262 控制器端口 6663

(2)Features_Request

交换机 就对控制器 发送 这个包 获取交换机的ID、缓冲区数量、端口信息等特性,因此交换机相应的回Features Reply。

(3)Set_Config

set config是控制器用来配置交换机发送的数据包
![]

(4) 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

(5) Features_Reply

交换机会回应相应的features reply消息,features request消息的transaction ID与features reply消息的transaction ID相同

(6) Packet_in

发送Packet-In消息时OpenFlow交换机分为两种情况,一种是缓存数据包,一种是不缓存数据包。如果不通过OpenFlow交换机缓存数据包,那么Packet-In消息的buffer_id字段设置为-1,将整个数据包发送至OpenFlow控制器。

(7) Packet_out

Packet out消息是由控制器发往交换机,是包含数据包发送命令的消息。若OpenFlow交换机的缓存中已存在数据包,而OpenFlow控制器发出“发送该数据包”的命令时,该消息指定了表示相应数据包的buffer_id。使用Packet-Out消息还可将OpenFlow控制器创建的数据包发送至OpenFlow交换机。此时,buffer_id置为-1,在Packet-Out消息的最后添加数据包数据。

(8)open_flow_mod

这个经过百度得知 是对流标进行操作的包 下面详细介绍

流程图

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?


明显TCP

二、进阶要求

将抓包结果对照OpenFlow源码,了解OpenFlow主要消息类型对应的数据结构定义。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

(1) hello

点击查看代码
/* 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 和 (3)Set_Config

点击查看代码
/* 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

点击查看代码
/* 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

点击查看代码
/* 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. */
};
/* 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

点击查看代码
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

点击查看代码
/* 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)open_flow_mod

点击查看代码
/* 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. */
};

# 三、 个人总结 1 要先开 wireshark抓包 再 开拓扑 不然不会有 hello 也就是说hello就会在 开启的时候 出现一次 2 想抓mod包 就要pingall一下 ? 为啥 经过百度可知 open_flow_mod是消息包


并且 mod包 是用来 给流表做 操作的

标签:struct,OpenFlow,实践,uint32,header,ofp,uint16,实验,port
From: https://www.cnblogs.com/rationalpeople/p/16735386.html

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