一、实验目的
能够运用 wireshark 对 OpenFlow 协议数据交互过程进行抓包；
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。
二、实验环境
Ubuntu 20.04 Desktop amd64
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。
2.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
控制器6633端口（我最高能支持OpenFlow 1.0） ---> 交换机50846端口
交换机50846端口（我最高能支持OpenFlow 1.5） ---> 控制器6633端口
双方建立连接，使用OpenFlow1.0
Features Request：控制器向将交换机发送Featrues Request消息，获取交换机特征信息
控制器6633端口---> 交换机50846端口
Set Conig：控制器告诉交换机如何配置
控制器6633端口---> 交换机50846端口
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
交换机50846端口--->控制器6633端口
第一次抓包未出现port，做完之后重新抓了一次，所以端口号发生了变化
Features Reply：Featrues Request的回复的交换机的特征信息
交换机50846端口---> 控制器6633端口
Packet_in：交换机收到数据包后问控制器如何处理
有两种情况会触发交换机向控制器发送 Packet-in 消息：
1.当交换机收到一个数据包后，查找流表。如果流表中有匹配条目，则交换机按照流表所指示的 action 列表处理数据包。如果没有，则交换机将数据包封装在 Packet-in 消息中发送给控制器处理，注意这时候数据包仍然会被放进缓冲区等待处理而不是被丢弃。
2.数据包在流表中有匹配的条目，但是其中所指示的 action 列表中包含转发给控制器的动作（Output = CONTROLLER），注意这时候数据包不会被放进缓冲区。
Flow_mod：分析抓取的flow_mod数据包，控制器向交换机下发流表项，指导数据的转发
因为第一遍的时候并没有执行PINGALL所以没有mod的信息，从新抓了一次所以端口号发生了变化。
Packet_out：告诉交换机将数据输出到交换机的哪个端口
控制器6633端口---> 交换机50846端口
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
是TCP协议
流程图
二（进阶要求）
OpenFlow的数据包头通用字段
/* 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);
消息类型
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和features request
/* 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 reply
/* 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. */
};
OFP_ASSERT(sizeof(struct ofp_switch_features) == 32);
set config
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. */
uint16_t miss_send_len; /* Max bytes of new flow that datapath should
send to the controller. */
};
OFP_ASSERT(sizeof(struct ofp_switch_config) == 12);
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. */
};
packet_out
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);
flow_mod
enum ofp_flow_mod_flags {
OFPFF_SEND_FLOW_REM = 1 << 0, /* Send flow removed message when flow
* expires or is deleted. */
OFPFF_CHECK_OVERLAP = 1 << 1, /* Check for overlapping entries first. */
OFPFF_EMERG = 1 << 2 /* Remark this is for emergency. */
};
/* 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. */
};
OFP_ASSERT(sizeof(struct ofp_flow_mod) == 72);
port_status
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);