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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。
1.下载虚拟机软件oracle VisualBox; 2.在虚拟机中安装Ubuntu 20.04 Desktop amd64,并完整安装Mininet;
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包。 |
主机 | IP地址 |
---|---|
h1 | 192.168.0.101/24 |
h2 | 192.168.0.102/24 |
h3 | 192.168.0.103/24 |
h4 | 192.168.0.104/24 |
#!/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 controllern' )
c0=net.addController(name='c0',
controller=Controller,
protocol='tcp',
port=6633)
info( '*** Add switchesn')
s1 = net.addSwitch('s1', cls=OVSKernelSwitch)
s2 = net.addSwitch('s2', cls=OVSKernelSwitch)
info( '*** Add hostsn')
h1 = net.addHost('h1', cls=Host, ip=' 192.168.0.101/24', defaultRoute=None)
h2 = net.addHost('h2', cls=Host, ip='192.168.0.102/24', defaultRoute=None)
h3 = net.addHost('h3', cls=Host, ip='192.168.0.103/24', defaultRoute=None)
h4 = net.addHost('h4', cls=Host, ip='192.168.0.104/24', defaultRoute=None)
info( '*** Add linksn')
net.addLink(h1, s1)
net.addLink(h3, s1)
net.addLink(s1, s2)
net.addLink(h2, s2)
net.addLink(s2, h4)
info( '*** Starting networkn')
net.build()
info( '*** Starting controllersn')
for controller in net.controllers:
controller.start()
info( '*** Starting switchesn')
net.get('s1').start([c0])
net.get('s2').start([c0])
info( '*** Post configure switches and hostsn')
CLI(net)
net.stop()
if __name__ == '__main__':
setLogLevel( 'info' )
myNetwork()
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。 |
首先控制器与交换机互相发送HELLO消息,可以看到控制器OpenFlow版本为1.0,交换机OpenFlow版本为1.5,依据向下兼容,使用OpenFlow1.0。
告诉输出到交换机的65531端口
流程图
3.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? |
1.将抓包结果对照OpenFlow源码,了解OpenFlow主要消息类型对应的数据结构定义。 |
OpenFlow源码:
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;
};
OpenFlow源码:
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. */
};
OpenFlow源码:
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;
};
OpenFlow源码:
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. */
};
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. */
};
OpenFlow源码:
enum ofp_packet_in_reason {
OFPR_NO_MATCH, /* No matching flow. */
OFPR_ACTION /* Action explicitly output to 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. */
};
OpenFlow源码:
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];
};
struct ofp_match {
uint32_t wildcards; /* Wildcard fields. */
uint16_t in_port; /* Input switch port. */
uint8_t dl_src[OFP_ETH_ALEN]; /* Ethernet source address. */
uint8_t dl_dst[OFP_ETH_ALEN]; /* Ethernet destination address. */
uint16_t dl_vlan; /* Input VLAN id. */
uint8_t dl_vlan_pcp; /* Input VLAN priority. */
uint8_t pad1[1]; /* Align to 64-bits */
uint16_t dl_type; /* Ethernet frame type. */
uint8_t nw_tos; /* IP ToS (actually DSCP field, 6 bits). */
uint8_t nw_proto; /* IP protocol or lower 8 bits of
* ARP opcode. */
uint8_t pad2[2]; /* Align to 64-bits */
uint32_t nw_src; /* IP source address. */
uint32_t nw_dst; /* IP destination address. */
uint16_t tp_src; /* TCP/UDP source port. */
uint16_t tp_dst; /* TCP/UDP destination port. */
};
OpenFlow源码:
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];
};
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.) */
};
实验难度:适中
遇到困难及解决办法:
个人感想:
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