（一）基本要求
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。
HELLO：互相发送Hello消息互相协商Openflow协议版本
交换机48452端口 ---> 控制器6633端口
于是双方建立连接
Features Request：控制器向将交换机发送Featrues Request消息，获取交换机特征信息
控制器6633端口---> 交换机48452端口
Set Conig：控制器告诉交换机如何配置
控制器6633端口---> 交换机48452端口
ort_Status：当交换机端口发生变化时，告知控制器相应的端口状态。
交换机48452端口---> 控制器6633端口
Features Reply：Featrues Request的回复的交换机的特征信息
交换机48452端口---> 控制器6633端口
Packet_in：交换机收到数据包后问控制器如何处理
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是控制器时
交换机48452端口---> 控制器6633端口
Flow_mod：分析抓取的flow_mod数据包，控制器向交换机下发流表项，指导数据的转发
控制器通过6633端口向交换机48452端口下发流表项，指导数据的转发处理
Packet_out：告诉交换机将数据输出到交换机的哪个端口
控制器6633端口---> 交换机48452端口
TCP协议
（二）进阶 OpenFlow主要消息类型对应的数据结构定义
OpenFlow的数据包头通用字段
/* 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. */ }; OFP_ASSERT(sizeof(struct ofp_header) == 8);
消息类型
`enum ofp_type {
/* Immutable messages. /
OFPT_HELLO, / Symmetric message /
OFPT_ERROR, / Symmetric message /
OFPT_ECHO_REQUEST, / Symmetric message /
OFPT_ECHO_REPLY, / Symmetric message /
OFPT_VENDOR, / Symmetric message */
/* Switch configuration messages. */
OFPT_FEATURES_REQUEST, /* Controller/switch message */
OFPT_FEATURES_REPLY, /* Controller/switch message */
OFPT_GET_CONFIG_REQUEST, /* Controller/switch message */
OFPT_GET_CONFIG_REPLY, /* Controller/switch message */
OFPT_SET_CONFIG, /* Controller/switch message */
/* Asynchronous messages. */
OFPT_PACKET_IN, /* Async message */
OFPT_FLOW_REMOVED, /* Async message */
OFPT_PORT_STATUS, /* Async message */
/* Controller command messages. */
OFPT_PACKET_OUT, /* Controller/switch message */
OFPT_FLOW_MOD, /* Controller/switch message */
OFPT_PORT_MOD, /* Controller/switch message */
/* Statistics messages. */
OFPT_STATS_REQUEST, /* Controller/switch message */
OFPT_STATS_REPLY, /* Controller/switch message */
/* Barrier messages. */
OFPT_BARRIER_REQUEST, /* Controller/switch message */
OFPT_BARRIER_REPLY, /* Controller/switch message */
/* Queue Configuration messages. */
OFPT_QUEUE_GET_CONFIG_REQUEST, /* Controller/switch message */
OFPT_QUEUE_GET_CONFIG_REPLY /* Controller/switch message */
};
**hello和features request**
/* 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;
};
**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. /
};
OFP_ASSERT(sizeof(struct ofp_switch_features) == 32);
**set config**enum ofp_config_flags {
/ Handling of IP fragments. /
OFPC_FRAG_NORMAL = 0, / No special handling for fragments. /
OFPC_FRAG_DROP = 1, / Drop fragments. /
OFPC_FRAG_REASM = 2, / Reassemble (only if OFPC_IP_REASM set). */
OFPC_FRAG_MASK = 3
};
/* 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. /
};
OFP_ASSERT(sizeof(struct ofp_switch_config) == 12);
**port_status**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;
};
OFP_ASSERT(sizeof(struct ofp_port_status) == 64);
**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**enum ofp_flow_mod_flags {
OFPFF_SEND_FLOW_REM = 1 << 0, / Send flow removed message when flow
* expires or is deleted. /
OFPFF_CHECK_OVERLAP = 1 << 1, / Check for overlapping entries first. /
OFPFF_EMERG = 1 << 2 / Remark this is for emergency. */
};
/* 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. */
};
OFP_ASSERT(sizeof(struct ofp_flow_mod) == 72);
**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.) */
};
OFP_ASSERT(sizeof(struct ofp_packet_out) == 16);
`
个人总结
一定要先抓包再运行python文件生成拓扑不然没有hello这个包
通过过滤器输入openflow_v1过滤数据报文
Flow_mod是通过pingall出现的
理解了OpenFlow协议中交换机与控制器的消息交互过程，了解了wireshark 抓包后的内容好具体信息