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实验3:OpenFlow协议分析实践

时间:2022-10-06 02:33:21浏览次数:45  
标签:struct OpenFlow 实践 uint8 header ofp uint16 实验 port

基本要求(一)

拓扑文件,wireshark抓包的结果截图和对应的文字说明

拓扑文件

HELLO(控制器6633端口(我最高能支持OpenFlow 1.0) --> 交换机52950端口)

HELLO(控制器52950端口(我最高能支持OpenFlow 1.3) --> 交换机6633端口)

Features Request(控制器6633端口(我需要你的特征信息) --> 交换机52950端口)

Set Config(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52950端口)

Port_Status(控制器52950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) --> 交换机6633端口)

Features Reply(控制器52950端口(这是我的特征信息,请查收) --> 交换机6633端口)

Packet_in(控制器52950端口(有数据包进来,请指示) --> 交换机6633端口)

Flow_mod(控制器6633端口(控制器通过6633端口向交换机52950端口下发流表项,指导数据的转发处理) --> 交换机52950端口)

Packet_out(控制器6633端口(请按照我给你的action进行处理) --> 交换机52950端口)

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

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

进阶要求(二)

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_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);

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.) */
};

个人总结(三)

       这次难点主要在分析上,数据看得头大,中间查看抓包数据的时候一时没找到要点,不过即时通过问答更正,希望下次再接再厉

标签:struct,OpenFlow,实践,uint8,header,ofp,uint16,实验,port
From: https://www.cnblogs.com/kazdel/p/16756928.html

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