（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。
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 ---> 交换机56752端口）
HELLO（交换机56752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56752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56752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56752端口（这是我的特征信息，请查收） ---> 控制器6633端口)
Packet_in
Flow_mod
Packet_out
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。
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？
TCP
（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。
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
/* 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. */
};
Port Staus
/* 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);
Features Reply
/* Description of a physical port */
struct ofp_phy_port {
uint16_t port_no;
uint8_t hw_addr[OFP_ETH_ALEN];
char name[OFP_MAX_PORT_NAME_LEN]; /* Null-terminated */
uint32_t config; /* Bitmap of OFPPC_* flags. */
uint32_t state; /* Bitmap of OFPPS_* flags. */
/* Bitmaps of OFPPF_* that describe features. All bits zeroed if
* unsupported or unavailable. */
uint32_t curr; /* Current features. */
uint32_t advertised; /* Features being advertised by the port. */
uint32_t supported; /* Features supported by the port. */
uint32_t peer; /* Features advertised by peer. */
};
OFP_ASSERT(sizeof(struct ofp_phy_port) == 48);
/* 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. */
};
Packet_in
交换机查找流表，没有匹配条目
/* 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. */
};
有匹配条目但是对应的action是OUTPUT=CONTROLLER时
/* 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
/* Fields to match against flows */
struct ofp_match {
uint32_t wildcards; /* Wildcard fields. /
uint16_t in_port; / Input switch port. /
uint8_t dl_src[OFP_ETH_ALEN]; / Ethernet source address. /
uint8_t dl_dst[OFP_ETH_ALEN]; / Ethernet destination address. /
uint16_t dl_vlan; / Input VLAN id. /
uint8_t dl_vlan_pcp; / Input VLAN priority. /
uint8_t pad1[1]; / Align to 64-bits /
uint16_t dl_type; / Ethernet frame type. /
uint8_t nw_tos; / IP ToS (actually DSCP field, 6 bits). /
uint8_t nw_proto; / IP protocol or lower 8 bits of
* ARP opcode. /
uint8_t pad2[2]; / Align to 64-bits /
uint32_t nw_src; / IP source address. /
uint32_t nw_dst; / IP destination address. /
uint16_t tp_src; / TCP/UDP source port. /
uint16_t tp_dst; / TCP/UDP destination port. /
};
/ 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. */
};
Packet_out
/* Action header that is common to all actions. The length includes the
- header and any padding used to make the action 64-bit aligned.
- NB: The length of an action must always be a multiple of eight. /
struct ofp_action_header {
uint16_t type; / One of OFPAT_*. /
uint16_t len; / Length of action, including this
header. This is the length of action,
including any padding to make it
64-bit aligned. */
uint8_t pad[4];
};
OFP_ASSERT(sizeof(struct ofp_action_header) == 8);
/* 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.) */
};
