(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。
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
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。
hello
控制器6633端口(我最高能支持OpenFlow 1.0) ----> 交换机53264端口
交换机53264端口(我最高能支持OpenFlow 1.5) ----> 控制器6633端口
双方建立连接,并使用 OpenFlow 1.0
Features Request / Set Config
控制器6633端口(我需要你的特征信息)----> 交换机53264端口
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53264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53264端口(这是我的特征信息,请查收) ---> 控制器6633端口
Packet_in
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53264端口(有数据包进来,请指示)--- 控制器6633端口
Packet_out(控制器收到 Packet-in 消息时的响应方式之一)
控制器6633端口(请按照我给你的action进行处理) ---> 交换机53264端口
交换机与控制器的消息交互过程
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?
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. */
};
/* 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;
};
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
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
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. */
};
5. 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. */
};
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. 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. */
};
8. 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.) */
};
个人总结
- 在一开始实验中,阅读pdf文件不够仔细,导致操作抓包和构建拓扑的顺序反了,找了好久没有发现hello包
- 这次实验总的来说,操作较为简单,在里面寻找结构的过程比较麻烦。通过这次实验,我对OpenFlow协议交换机与控制器交互过程有了更加深刻的了解。对于wireshark抓包操作使用也更为熟练。