实验3:OpenFlow协议分析实践
一.实验目的
1.能够运用 wireshark 对 OpenFlow 协议数据交互过程进行抓包;
2.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 Linux操作系统
三.实验要求
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.命令行拓扑完整性测试
3.查看抓包结果
HELLO
控制器 “6633” 端口到交换机 “37852” 端口(使用OpenFlow 1.0协议)
从控制器6633端口到交换机37852端口(使用openflow1.5协议)
OFPT_HELLO后,双方协商使用openflow1.0协议
FEATURES_REQUEST 控制器6633向交换机37852请求特征
SET_CONFIG
控制器6633端口到交换机37852端口
PORT_STATUS
从交换机39462端口到控制器6633端口当交换机端口发生变化时,告知控制器相应的端口状态
FEATURES_REPLY
交换机37852端口到控制器6633端口,回复特征信息
PACKET_IN
作用:分析抓取的数据包,可以发现是因为交换机发现此时自己并没有匹配的流表 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是OUTPUT=CONTROLLER时交换机37852端口到控制器6633端口(有数据包进来,请指示)
PACKET_OUT
控制器6633端口到交换机37852端口(请按照我给你的action进行处理)
FLOW_MOD
分析抓取的flow_mod数据包,控制器通过6633端口向交换机37852端口下发流表
192.168.0.102 到 192.168.0.101
192.168.0.101 到 192.168.0.102
交互图:
交换机与控制器建立通信时是使用TCP协议。
(二)进阶要求
将抓包基础要求第2步的抓包结果对照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. */
};
2、FEATURES_REQUEST
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. */
};
3、SET_CONFIG
/* 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
/* 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
/* 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
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
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、FLOW_MOD
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. */
};
实验总结
1、通过本次实验,我能更加熟练的使用wireshark进行抓包,并且学习到了使用过滤器来过滤出想要的包
2、我学到了使用包解析工具来分析与解释openflow协议的数据包交易过程和机制
3、本次实验并不难以操作,只是更加考虑抓包、找包分析时的耐心