1.请用Markdown排版；
2.基础要求只需要提交导入到/home/用户名/学号/lab3/目录下的拓扑文件，wireshark抓包的结果截图和对应的文字说明；
1)hello
交换机52298端口（最高支持OpenFlow 1.5）-->控制器6633端口
控制器6633端口（最高支持OpenFlow 1.0）-->交换机52298端口
于是双方建立连接，并使用OpenFlow1.0
2）Feature Request
控制器6633端口（需要你的特征信息）-->交换机52298端口
3)set conig
控制器52298端口（请按照我给你的flag和max bytes of packet进行配置）-->控制器52298端口
3）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
4）Features Reply
5)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口是OUTPUT=CONTROLLER时
交换机52298端口（有数据包进来，请指示）-->控制器6633端口
6)Flow_mod
分析抓取的flow_mod数据包，控制器通过6633端口向交换机52298端口，交换机35536端口下发流表项，指导数据的转发处理
7)Packet_out
控制器6633端口（请按照我给你的action进行处理）-->交换机552298duankou
·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。
·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？
TCP
答：是TCP协议
3.进阶要求为选做，有完成的同学请提交相关截图对应的OpenFlow代码，加以注释说明，有完成比未完成的上机分数更高。
1）Hello
/* 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. */
};
OFP_ASSERT(sizeof(struct ofp_header) == 8);
/* 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;
};
2)Features Request
/* 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. */
};
OFP_ASSERT(sizeof(struct ofp_header) == 8);
/* 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;
};
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. */
};
4)Port Staus
/* 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;
};
OFP_ASSERT(sizeof(struct ofp_port_status) == 64);
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. */
};
OFP_ASSERT(sizeof(struct ofp_phy_port) == 48);
/* 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
·交换机查找流表，没有匹配条目
/* 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. */
};
·交换机查找流表，有匹配条目，对应action是OUTPUT=CONTROLLER，固定收到向控制器发送包
/* 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
/* 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. */
};
8)Packet_out
/* 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.) */
};
OFP_ASSERT(sizeof(struct ofp_packet_out) == 16);
4.个人总结，包括但不限于实验难度、实验过程遇到的困难及解决办法，个人感想，不少于200字。
这次实验的基础实验的难度不是很大，主要是针对wireshark的运用。本次实验主要是对控制器和交换机协议报文的交互进行一个掌握和了解和学习能够运用 wireshark 对 OpenFlow 协议数据交互过程进行抓包和wireshark的一些基础功能的运用，通过本次实验对SDN学习的内容的方向有了一定的了解，和SDN对交换机的优化和实现有了基础的认识。在这次实验我学会了运用wireshark对OpenFlow协议数据交互过程进行抓包，并且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。进一步理解了网络拓扑结构的构建过程。