（一）基础要求
1）/home/用户名/学号/lab3/目录下的拓扑文件
2）wireshark抓包的结果截图和对应的文字说明
- Hello
控制器6633端口（我最高能支持OpenFlow 1.0） ---> 交换机52084端口
交换机52084端口（我最高能支持OpenFlow 1.5） ---> 控制器6633端口
- Features Request
控制器6633端口（我需要你的特征信息） ---> 交换机52084端口
- Set Conig
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52084端口
- Port Status
从交换机52084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。
- Features Reply
交换机52084端口（这是我的特征信息，请查收） ---> 控制器6633端口
- Packet_in
交换机52084端口（有数据包进来，请指示）--- 控制器6633端口
- Flow_mod
控制器通过6633端口向交换机52084端口下发流表项，指导数据的转发处理
- Packet_out
控制器6633端口向交换机52084端口发送数据，并告知交换机输出到端口
3）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
4）交换机与控制器建立通信时是使用TCP协议还是UDP协议？
使用的是TCP协议,如下图
（二）进阶要求 - hello
/* 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);
/* 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 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. */
};
OFP_ASSERT(sizeof(struct ofp_header) == 8);
/* 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;
};
- 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. */ //flag不同的值代表不同的处理方式
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
/* 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;
};
OFP_ASSERT(sizeof(struct ofp_port_status) == 64); //发生变化，则需发送port status来告知
- 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);
- Packet_in
/* 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. */
};
OFP_ASSERT(sizeof(struct ofp_packet_in) == 20);
- 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). */ //空闲超时时间
uint16_t hard_timeout; /* Max time before discarding (seconds). */ //最大生存时间
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_*. */
//标志位，可以用来指示流表删除后是否发送flow‐removed消息，添加流表时是否检查流表重复项，添加的流表项是否为应急流表项
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
/* Send packet (controller -> datapath). */
struct ofp_packet_out {
struct ofp_header header;
uint32_t buffer_id; //交换机缓存区id，如果为-1则指定的为packet-out消息携带的data字段 /* ID assigned by datapath (-1 if none). */
uint16_t in_port; //如果buffer_id为‐1，并且action列表中指定了Output=TABLE的动作,in_port将作为data段数据包的额外匹配信息进行流表查询
/* Packet's input port (OFPP_NONE if none). */
uint16_t actions_len; //用来区分actions和data段 /* 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);
（三）个人总结
在做的过程中由于不大熟悉命令有所卡顿，这个实验主要是抓包分析OpenFlow通讯过程数据包。对wireshark工具使用更加熟练，通过抓包的结果进行观察与学习，了解OpenFlow主要消息类型对应的数据结构定义。在最开始的时候找hello包时，老是找不到（太费眼睛了），后面同学帮忙才找到，其它包就比较容易找到，然后是在进阶部分对源代码进行分析比较难，看不懂英文，就得去网上查阅。一定要做一题存稿！！！以免发生意外，就白做了，或者看看有没有自动备份。
