一、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
控制器6633端口（我最高能支持OpenFlow 1.0） ---> 交换机40498端口
交换机40498端口（我最高能支持OpenFlow 1.0） ---> 控制器6633端口
2.Features Request
控制器6633端口（我需要你的特征信息） ---> 交换机40498端口
3.Set Conig
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40498端口
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
Features Reply消息包括Openflow Header 和Features Reply Message
交换机40498端口（这是我的特征信息，请查收） ---> 控制器6633端口
6.Packet in
交换机40498端口（有数据包进来，请指示）--- 控制器6633端口
7.Flow mod
控制器通过6633端口向交换机40498端口下发流表项，指导数据的转发处理
8.Packet_out
控制器6633端口向交换机40498端口发送数据，并告知交换机输出到65531端口。
9.流程图：
10.交换机与控制器建立通信时是使用TCP协议还是UDP协议？
交换机与控制器建立通信时使用的是TCP协议，如下图：
二、进阶要求
消息类型：
点击查看代码
enum ofp_type {
/* Immutable messages. */
OFPT_HELLO, /* Symmetric message */
OFPT_ERROR, /* Symmetric message */
OFPT_ECHO_REQUEST, /* Symmetric message */
OFPT_ECHO_REPLY, /* Symmetric message */
OFPT_VENDOR, /* Symmetric message */
/* Switch configuration messages. */
OFPT_FEATURES_REQUEST, /* Controller/switch message */
OFPT_FEATURES_REPLY, /* Controller/switch message */
OFPT_GET_CONFIG_REQUEST, /* Controller/switch message */
OFPT_GET_CONFIG_REPLY, /* Controller/switch message */
OFPT_SET_CONFIG, /* Controller/switch message */
/* Asynchronous messages. */
OFPT_PACKET_IN, /* Async message */
OFPT_FLOW_REMOVED, /* Async message */
OFPT_PORT_STATUS, /* Async message */
/* Controller command messages. */
OFPT_PACKET_OUT, /* Controller/switch message */
OFPT_FLOW_MOD, /* Controller/switch message */
OFPT_PORT_MOD, /* Controller/switch message */
/* Statistics messages. */
OFPT_STATS_REQUEST, /* Controller/switch message */
OFPT_STATS_REPLY, /* Controller/switch message */
/* Barrier messages. */
OFPT_BARRIER_REQUEST, /* Controller/switch message */
OFPT_BARRIER_REPLY, /* Controller/switch message */
/* Queue Configuration messages. */
OFPT_QUEUE_GET_CONFIG_REQUEST, /* Controller/switch message */
OFPT_QUEUE_GET_CONFIG_REPLY /* Controller/switch message */
};
Hello：
点击查看代码
/* Header on all OpenFlow packets. */
struct ofp_header {
uint8_t version; /* OFP_VERSION. */ //协议的版本号
uint8_t type; /* One of the OFPT_ constants. */ //消息类型
uint16_t length; /* Length including this ofp_header. */ //消息长度
uint32_t xid; /* Transaction id associated with this packet.
Replies use the same id as was in the request
to facilitate pairing. */ //关联id
};
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;
};
Features Request：
点击查看代码
struct ofp_header {
uint8_t version; /* OFP_VERSION. */ //协议的版本号
uint8_t type; /* One of the OFPT_ constants. */ //消息类型
uint16_t length; /* Length including this ofp_header. */ //消息长度
uint32_t xid; /* Transaction id associated with this packet.
Replies use the same id as was in the request
to facilitate pairing. */ //关联id
};
//该参数与hello报文结构相同
Set Conig：
点击查看代码
enum ofp_config_flags {
/* Handling of IP fragments. */
OFPC_FRAG_NORMAL = 0, /* No special handling for fragments. */
OFPC_FRAG_DROP = 1, /* Drop fragments. */
OFPC_FRAG_REASM = 2, /* Reassemble (only if OFPC_IP_REASM set). */
OFPC_FRAG_MASK = 3
};
/* Switch configuration. */
struct ofp_switch_config {
struct ofp_header header;
uint16_t flags; /* OFPC_* flags. */ //flag指示交换机如何处理 IP 分片数据包，不同的flag值对应不同的处理方式
uint16_t miss_send_len; /* Max bytes of new flow that datapath should
send to the controller. */ //数据包发给控制器的最大字节数
};
OFP_ASSERT(sizeof(struct ofp_switch_config) == 12);
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;
};
OFP_ASSERT(sizeof(struct ofp_port_status) == 64);
Features Reply：
点击查看代码
/* 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. */ //标识id
uint32_t n_buffers; /* Max packets buffered at once. */ //缓冲区缓冲的最大数据包个数
uint8_t n_tables; /* Number of tables supported by datapath. */ //流表数量
uint8_t pad[3]; /* Align to 64-bits. */
/* Features. */
uint32_t capabilities; /* Bitmap of support "ofp_capabilities". */ //支持的特殊功能
uint32_t actions; /* Bitmap of supported "ofp_action_type"s. */ //支持的动作
/* Port info.*/
struct ofp_phy_port ports[0]; /* Port definitions. The number of ports
is inferred from the length field in
the header. */ //物理端口描述列表
};
OFP_ASSERT(sizeof(struct ofp_switch_features) == 32);
Packet-in：
点击查看代码
/* Why is this packet being sent to the controller? */
enum ofp_packet_in_reason {
OFPR_NO_MATCH, /* No matching flow. */ //没有匹配的项目
OFPR_ACTION /* Action explicitly output to controller. */ //action列表中包含转发给控制器的动作
};
/* 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. */ //data字段的长度
uint16_t in_port; /* Port on which frame was received. */ //进入交换机的端口号
uint8_t reason; /* Reason packet is being sent (one of OFPR_*) */ //发送的原因
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. */
};
OFP_ASSERT(sizeof(struct ofp_packet_in) == 20);
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). */ //空闲超时时间
uint16_t hard_timeout; /* Max time before discarding (seconds). */ //最大生存时间
uint16_t priority; /* Priority level of flow entry. */ //优先级
uint32_t buffer_id; /* Buffered packet to apply to (or -1). //缓存区ID
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_*. */ //标志位
struct ofp_action_header actions[0]; /* The action length is inferred
from the length field in the
header. */ //action列表
};
OFP_ASSERT(sizeof(struct ofp_flow_mod) == 72);
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). */ //交换机缓存区id
uint16_t in_port;
/* Packet's input port (OFPP_NONE if none). */
uint16_t actions_len; /* Size of action array in bytes. */ //action列表的长度
struct ofp_action_header actions[0]; /* Actions. */ //动作列表
/* uint8_t data[0]; */ /* Packet data. The length is inferred
from the length field in the header.
(Only meaningful if buffer_id == -1.) */ // 数据缓存区
};
OFP_ASSERT(sizeof(struct ofp_packet_out) == 16);
三、总结：
本次实验操作较少较简单，较难的地方在如何理解与分析交换机与控制器交互的过程。在实验建立拓扑之前一定要先启动wireshark抓包后在开启openflow建立拓扑，回到wireshark运用过滤器寻找，不然会找不到Hello报文。通过这次实验加深了对wireshark的使用熟练度，了解了openflow 交换机和控制器的交互过程和主要的消息类型与对应的信息。