实验3：OpenFlow协议分析实践
实验目的
- 能够运用 wireshark 对 OpenFlow 协议数据交互过程进行抓包；
- 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。
实验环境
Ubuntu 20.04 Desktop amd64
实验要求
（一）基本要求
- 搭建如下拓扑
命令行拓扑完整性测试
- 查看抓包结果
OFPT_HELLO:
从控制器6633端口到交换机53956端口，使用OpenFlow1.0协议：
从控制器53956端口到交换机6633端口，使用OpenFlow1.5协议：
OFPT_HELLO后，双方协商使用openflow1.0协议
OFPT_FEATURES_REQUEST:
从控制器6633端口到交换机53956端口，请求特征信息
OFPT_SET_CONFIG：
OFPT_PORT_STATUS：
从交换机53956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
OFPT_FEATURES_REPLY：
交换机53956端口到控制器6633端口，回复特征信息
OFPT_PACKET_IN：
分析抓取的数据包（交换机53956端口（有数据包进来，请指示）--->控制器6633端口）
OFPT_PACKET_OUT：
请按照我给你的action进行处理（控制器6633端口--->交换机53956端口）
OFPT_FLOW_MOD
分析抓取的flow_mod数据包，控制器通过6633端口向交换机53954端口、交换机53956端口下发流表项，指导数据的转发处理
-
相关交互图或流程图。
-
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？
所以（Transmission Control Protocol)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。
- OFPT_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_FEATURES_REQUEST
/* Header on all OpenFlow packets. */
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_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. */
};
- OFPT_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;
};
- OFPT_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. */
};
- OFPT_PACKET_IN
两种情况：- 交换机查找流表，发现没有匹配条目,但是这种包没有抓到过
enum ofp_packet_in_reason {
OFPR_NO_MATCH, /* No matching flow. */
OFPR_ACTION /* Action explicitly output to controller. */
};
2. 有匹配条目,对应的action是OUTPUT=CONTROLLER,固定收到向控制器发送包
/* 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.OFPT_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.) */
};
- OFPT_FLOW_MOD
/* Flow setup and teardown (controller -> datapath). */
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. */
};
（三）个人总结
1.本次实验刚开始时，建立拓扑输入命令时，没加上sudo，所以出现了报错，通过查找上一次实验的报告改了过来
2.本次实验还学会了行用过滤器进行过滤，因为版本的不同，在过滤openflow_v4时找不到结果，通过查询发现可以用openflow_v6进行过滤
3.因为未详细阅读需要注意的事项，所以先建立拓扑再抓包了，所以出现的抓包结果一直找不到，再重复阅读实验手册才发现要先开启抓包再构建拓扑。还有就是在抓包之前要先pingall一次，才能找到FLOW_MOD
4.总体来说本次实验不是很难，但是要非常的仔细，不然一不小心就会出现一些不必要错误