| 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 |
首先，控制器与交互及互相发送 Hello 消息
其次，OpenFlow 连接建立之后,控制器向交换机发送 Features Request 消息查询交换机特性
交换机在收到控制器发出的 Features Request 消息后，将自己的特性告诉给控制器，返回 Features Request 消息
知道了交换机的特性之后就要配置交换机了
当控制器收到 Packet-in 消息时有两种响应的方式:
1.Flow-Mod：控制器收到 Packet‐in 消息后，可以发送 Flow‐Mod 消息向交换机下发一个流表项
2.Packet-out：与Flow-Mod不同的是，控制器不会下发流表，而是直接告诉交换机该如何做
Hello包定义了一个header
header数据结构：
如果连接失败，会发送一个error包
error类型：
enum ofp_error_type {
OFPET_HELLO_FAILED, /* Hello protocol failed. */
OFPET_BAD_REQUEST, /* Request was not understood. */
OFPET_BAD_ACTION, /* Error in action description. */
OFPET_FLOW_MOD_FAILED, /* Problem modifying flow entry. */
OFPET_PORT_MOD_FAILED, /* Port mod request failed. */
OFPET_QUEUE_OP_FAILED /* Queue operation failed. */
};
OFPT_FEATURES 主要是请求交换机的特性
交换机的特性数据结构定义:
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产生的原因有两种，一种是没匹配到流表，另一种是匹配到了，动作是转发的控制器
代码
:enum ofp_packet_in_reason {
OFPR_NO_MATCH, /* No matching flow. */
OFPR_ACTION /* Action explicitly output to controller. */
};数据格式
：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. */
packet_in事件之后，一般会触发两类事件，packet_out和flow_mod。两者都是指导交换机如何处理数据包，区别是是否下发流表项
数据结构
: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.) */
};
控制器收到 Packet‐in 消息后，可以发送 Flow‐Mod 消息向交换机下发一个流表项,指导交换机转发数据包
数据格式：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);
/* Why was this flow removed? */
enum ofp_flow_removed_reason {
OFPRR_IDLE_TIMEOUT, /* Flow idle time exceeded idle_timeout. */
OFPRR_HARD_TIMEOUT, /* Time exceeded hard_timeout. */
OFPRR_DELETE /* Evicted by a DELETE flow mod. */
};
原文：https://www.cnblogs.com/chenqing123/p/15309053.html