基础要求
一、拓扑文件
#!/usr/bin/env python
from mininet.net import Mininet
from mininet.node import Controller, RemoteController, OVSController
from mininet.node import CPULimitedHost, Host, Node
from mininet.node import OVSKernelSwitch, UserSwitch
from mininet.node import IVSSwitch
from mininet.cli import CLI
from mininet.log import setLogLevel, info
from mininet.link import TCLink, Intf
from subprocess import call
def myNetwork():
net = Mininet( topo=None,
build=False,
ipBase='192.168.0.0/24')
info( '*** Adding controller\n' )
c0=net.addController(name='c0',
controller=Controller,
protocol='tcp',
port=6633)
info( '*** Add switches\n')
s2 = net.addSwitch('s2', cls=OVSKernelSwitch)
s1 = net.addSwitch('s1', cls=OVSKernelSwitch)
info( '*** Add hosts\n')
h2 = net.addHost('h2', cls=Host, ip='192.168.0.102/24', defaultRoute=None)
h4 = net.addHost('h4', cls=Host, ip='192.168.0.104/24', defaultRoute=None)
h3 = net.addHost('h3', cls=Host, ip='192.168.0.103/24', defaultRoute=None)
h1 = net.addHost('h1', cls=Host, ip='192.168.0.101/24', defaultRoute=None)
info( '*** Add links\n')
net.addLink(h1, s1)
net.addLink(s1, h3)
net.addLink(s1, s2)
net.addLink(s2, h2)
net.addLink(s2, h4)
info( '*** Starting network\n')
net.build()
info( '*** Starting controllers\n')
for controller in net.controllers:
controller.start()
info( '*** Starting switches\n')
net.get('s2').start([c0])
net.get('s1').start([c0])
info( '*** Post configure switches and hosts\n')
CLI(net)
net.stop()
if __name__ == '__main__':
setLogLevel( 'info' )
myNetwork()
二、Wireshark抓包结果
1、Hello
控制器6633端口 ——> 交换机45834端口 OpenFlow 1.0 协议
交换机45834端口 ——> 控制器6633端口 OpenFlow 1.5 协议
2、Features Request
控制器6633端口（我需要你的特征信息） ——> 交换机45834端口
3、Set Config
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45834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
交换机端口45834（这是我的特征信息，请查收） ——> 控制器6633端口
6、Packet_In
交换机45834端口（有数据包进来，请指示） ——> 控制器6633端口
7、PACKET_OUT
控制器6633端口（请按照我给你的action进行处理） ---> 交换机50980端口:
8、Flow_Mod
分析抓取的flow_mod数据包，控制器通过6633端口向交换机45834端口、交换机45834端口下发流表项，指导数据的转发处理
三、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
四、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？
由图可知，交换机与控制器建立通信时是使用TCP协议
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
/* 141 */
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;
};
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. */
};
struct ofp_hello {
struct ofp_header header;
};
3、Set Config
/* 168 */
/* 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
/* 286 */
/* 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
/* 256 */
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
/* 320*/
/* 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. */
};
7、Packet_Out
/* 445 */
/* 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.) */
};
8、Flow_Mod
/* 560 */
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];
};
个人总结
遇到的问题：
- 抓包时找不到包
- 找不到45834端口发给6633的hello报文
解决方法：
- 先抓包再构建拓扑
- 通过将过滤条件设置为openflow_v6筛选出结果
实验收获：
本次实验需要查看源码，需要通过不断比对源码中定义的结构体和抓到的包的报文结构，学习到了如何进行数据包过滤、怎么查看并分析数据包的的流动过程，并且可以了解在pingall的过程中有哪些包产生并且如何传递，学习到openflow协议在代码上是如何体现的，更加深入得学习了OpenFlow协议TCP协议，并更熟练得掌握Wireshark的使用方法。总体来说本次实验不难，但是需要认真仔细，不然容易出现一些不必要错误。
标签：struct,OpenFlow,端口,实践,header,ofp,uint16,实验,net From： https://www.cnblogs.com/codesheepXK/p/16736415.html