实验3：OpenFlow协议分析实践

目录

• 一、基本要求
  • 1.搭建拓扑
  • 2.抓包结果
    • HELLO
    • FEATURES_REQUEST
    • SET_CONFIG
    • PORT_STATUS
    • FEATURES_REPLY
    • PACKET_IN
    • Flow_mod
    • PACKET_OUT
    • 交互图
  • 3.回答问题：
• 二、进阶要求
  • OpenFlow源码数据结构
    • Hello
    • Features Request
    • Set Config
    • Port_Status
    • Features Reply
    • Packet_In
    • Flow_Mod
    • Packet_Out
• 三、个人总结

一、基本要求

1.搭建拓扑

2.抓包结果

HELLO

控制器6633端口---> 交换机48280端口

交换机48280端口---> 控制器6633端口

双方建立连接，并使用OpenFlow 1.0

FEATURES_REQUEST

控制器6633端口---> 交换机48280端口

SET_CONFIG

控制器6633端口 ---> 交换机48280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

FEATURES_REPLY

交换机48280端口 ---> 控制器6633端口

PACKET_IN

交换机48280端口--->控制器6633端口

Flow_mod

分析抓取的flow_mod数据包，控制器通过6633端口向交换机48280端口下发流表项，指导数据的转发处理

PACKET_OUT

控制器6633端口--->交换机48280端口

交互图

3.回答问题：

交换机与控制器建立通信时是使用TCP协议

二、进阶要求

OpenFlow源码数据结构

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. */
};

struct ofp_hello {
struct ofp_header header;
};

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. */
};

struct ofp_hello {
struct ofp_header header;
};

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. */
};

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;
};

Features Reply

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. /
};
/ 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. */
};

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. */
};

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. /
};
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];
};

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.) */
};

三、个人总结

先抓包再建立拓扑，找不到OFPT_FLOW_MOD数据包，要先进行CLI中pingall。通过本次实验，我复习了使用wireshark抓取OpenFlow协议的数据包，对数据包交互也有了更深地理解。在进阶要求中，比对openflow.h源码与抓取到的数据包的结构，对OpenFlow主要消息类型对应的数据结构定义有了更为深刻的理解