openflow协议

​编辑

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

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• (二)进阶要求

1.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。

(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;

};

• 对应​编辑
• (2)Features Request
• 与Hello中的数据格式相同​编辑
• (3)Set Conig

/* 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. */

};

• 对应​编辑
• (4)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;

};

• 对应​编辑
• (5)Features Reply

/* 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

/* 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)Flow_mod

/* Fields to match against flows */struct ofp_match {

    uint32_t wildcards;        /* Wildcard fields. */

    uint16_t in_port;          /* Input switch port. */

    uint8_t dl_src[OFP_ETH_ALEN]; /* Ethernet source address. */

    uint8_t dl_dst[OFP_ETH_ALEN]; /* Ethernet destination address. */

    uint16_t dl_vlan;          /* Input VLAN id. */

    uint8_t dl_vlan_pcp;       /* Input VLAN priority. */

    uint8_t pad1[1];           /* Align to 64-bits */

    uint16_t dl_type;          /* Ethernet frame type. */

    uint8_t nw_tos;            /* IP ToS (actually DSCP field, 6 bits). */

    uint8_t nw_proto;          /* IP protocol or lower 8 bits of

                                * ARP opcode. */

    uint8_t pad2[2];           /* Align to 64-bits */

    uint32_t nw_src;           /* IP source address. */

    uint32_t nw_dst;           /* IP destination address. */

    uint16_t tp_src;           /* TCP/UDP source port. */

    uint16_t tp_dst;           /* TCP/UDP destination port. */

};/* 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. */

};

​编辑

• (8)Packet_out

/* Action header that is common to all actions.  The length includes the

 * header and any padding used to make the action 64-bit aligned.

 * NB: The length of an action *must* always be a multiple of eight. */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];

};OFP_ASSERT(sizeof(struct ofp_action_header) == 8);

/* 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.) */

};

• 四、个人总结
• 实验难度：适中
• 实验过程遇到的困难及解决办法： 
  • 打开wireshark后创建拓扑，过滤出Openflow数据包，发现一些数据包没有找到，重新看了文件，并上网查阅资料后发现要先打开wireshark再执行Python文件，进行pingall即可找到。
• 个人感想：

本次实验是结课实验，实验难度相对于平常练习会有难度一些，需要建立拓扑后在wireshark中操作，首先要能够熟练使用wireshark，其次就是找包的时候数据很多，容易错过，需要很细心。通过阅读openflow的源码，能理清楚其中的数据结构，并和实际抓到的包的详细信息对应起来，从而理解openflow协议的数据包交互过程。除此之外，对wireshark中过滤器的使用也有了更深刻的了解，对openflow协议有了更深刻的认识，整理实验报告的过程中能够加深对整个交互过程的理解，截图较多，整理起来需要足够的耐心。实验中遇到的问题都得到了解决，对mininet的一些命令行操作也更加的熟练。