2019 SDN上机第3次作业

1. 利用Mininet仿真平台构建如下图所示的网络拓扑，配置主机h1和h2的IP地址（h1:10.0.0.1，h2:10.0.0.2），测试两台主机之间的网络连通性

1、创建拓扑

2、测试连通性

2. 利用Wireshark工具，捕获拓扑中交换机与控制器之间的通信数据，对OpenFlow协议类型的各类报文进行分析，写出你的分析内容。

1、HELLO

控制器6633端口（OpenFlow 1.0） ---> 交换机56998端口

交换机56998端口（OpenFlow 1.3）--- 控制器6633端口

于是双方建立连接，并使用OpenFlow 1.0

2、Features Request

控制器6633端口（我需要你的特征信息） ---> 交换机56998端口

3、Set Config

控制器6633端口---> 交换机56998端口

4、Features Reply

交换机56998端口（这是我的特征信息，请查收）--- 控制器6633端口

Features 消息包括 OpenFlow Header 和 Features Reply Message
对照Features Reply Message结构

 struct ofp_switch_features{
    struct ofp_header header;
    uint64_t datapath_id; /*唯一标识 id 号*/
    uint32_t n_buffers; /*交缓冲区可以缓存的最大数据包个数*/
    uint8_t n_tables; /*流表数量*/
    uint8_t pad[3]; /*align to 64 bits*/
    uint32_t capabilities; /*支持的特殊功能，具体见 ofp_capabilities*/
    uint32_t actions; /*支持的动作，具体见 ofp_actions_type*/
    struct ofp_phy_port ports[0]; /*物理端口描述列表，具体见 ofp_phy_port*/
    };

对应到抓取到的报文，逐项查看报文内容

OpenFlow 1.0
    .000 0001 = Version: 1.0 (0x01)
    Type: OFPT_FEATURES_REPLY (6)
    Length: 80
    Transaction ID: 3321189544
    Datapath unique ID: 0x0000000000000003
        MAC addr: 00:00:00_00:00:00 (00:00:00:00:00:00)
        Implementers part: 0x0003
    n_buffers: 256
    n_tables: 254
    Pad: 000000
    capabilities: 0x000000c7
        .... .... .... .... .... .... .... ...1 = Flow statistics: True
        .... .... .... .... .... .... .... ..1. = Table statistics: True
        .... .... .... .... .... .... .... .1.. = Port statistics: True
        .... .... .... .... .... .... .... 0... = Group statistics: False
        .... .... .... .... .... .... ..0. .... = Can reassemble IP fragments: False
        .... .... .... .... .... .... .1.. .... = Queue statistics: True
        .... .... .... .... .... ...0 .... .... = Switch will block looping ports: False
    actions: 0x00000fff
        .... .... .... .... .... .... .... ...1 = Output to switch port: True
        .... .... .... .... .... .... .... ..1. = Set the 802.1q VLAN id: True
        .... .... .... .... .... .... .... .1.. = Set the 802.1q priority: True
        .... .... .... .... .... .... .... 1... = Strip the 802.1q header: True
        .... .... .... .... .... .... ...1 .... = Ethernet source address: True
        .... .... .... .... .... .... ..1. .... = Ethernet destination address: True
        .... .... .... .... .... .... .1.. .... = IP source address: True
        .... .... .... .... .... .... 1... .... = IP destination address: True
        .... .... .... .... .... ...1 .... .... = IP ToS (DSCP field, 6 bits): True
        .... .... .... .... .... ..1. .... .... = TCP/UDP source port: True
        .... .... .... .... .... .1.. .... .... = TCP/UDP destination port: True
        .... .... .... .... .... 1... .... .... = Output to queue: True
    Port data 1
        Port number: 65534
        HW Address: 1a:0a:8c:a7:38:42 (1a:0a:8c:a7:38:42)
        Port Name: s3
        Config flags: 0x00000001
            .... .... .... .... .... .... .... ...1 = Port is administratively down: True
            .... .... .... .... .... .... .... ..0. = Disable 802.1D spanning tree on port: False
            .... .... .... .... .... .... .... .0.. = Drop all packets except 802.1D spanning tree packets: False
            .... .... .... .... .... .... .... 0... = Drop received 802.1D STP packets: False
            .... .... .... .... .... .... ...0 .... = Do not include this port when flooding: False
            .... .... .... .... .... .... ..0. .... = Drop packets forwarded to port: False
            .... .... .... .... .... .... .0.. .... = Do not send packet-in msgs for port: False
        State flags: 0x00000001
            .... .... .... .... .... .... .... ...1 = No physical link present: True
        Current features: 0x00000000
            .... .... .... .... .... .... .... ...0 = 10 Mb half-duplex rate support: False
            .... .... .... .... .... .... .... ..0. = 10 Mb full-duplex rate support: False
            .... .... .... .... .... .... .... .0.. = 100 Mb half-duplex rate support: False
            .... .... .... .... .... .... .... 0... = 100 Mb full-duplex rate support: False
            .... .... .... .... .... .... ...0 .... = 1 Gb half-duplex rate support: False
            .... .... .... .... .... .... ..0. .... = 1 Gb full-duplex rate support: False
            .... .... .... .... .... .... .0.. .... = 10 Gb full-duplex rate support: False
            .... .... .... .... .... .... 0... .... = Copper medium: False
            .... .... .... .... .... ...0 .... .... = Fiber medium: False
            .... .... .... .... .... ..0. .... .... = Auto-negotiation: False
            .... .... .... .... .... .0.. .... .... = Pause: False
            .... .... .... .... .... 0... .... .... = Asymmetric pause: False
        Advertised features: 0x00000000
        Features supported: 0x00000000
        Features advertised by peer: 0x00000000

5、Packet_in

交换机56998端口（有数据包进来，请指示）--- 控制器6633端口

结合Packet_in的结构

struct ofp_packet_in {
    struct ofp_header header;
    uint32_t buffer_id; /*Packet-in消息所携带的数据包在交换机缓存区中的ID*/
    uint16_t total_len; /*data字段的长度*/
    uint16_t in_port; /*数据包进入交换机时的端口号*/
    uint8_t reason; /*发送Packet-in消息的原因，具体见 ofp_packet_in_reason*/
    uint8_t pad;
    uint8_t data[0]; /*携带的数据包*/
};

分析抓取的数据包，可以发现是因为交换机发现此时自己并没有匹配的流表（Reason: No matching flow (table-miss flow entry) (0)），所以要问控制器如何处理

Frame 577: 176 bytes on wire (1408 bits), 176 bytes captured (1408 bits) on interface 0
Linux cooked capture
Internet Protocol Version 4, Src: 127.0.0.1, Dst: 127.0.0.1
Transmission Control Protocol, Src Port: 57002, Dst Port: 6633, Seq: 2589, Ack: 509, Len: 108
OpenFlow 1.0
    .000 0001 = Version: 1.0 (0x01)
    Type: OFPT_PACKET_IN (10)
    Length: 108
    Transaction ID: 0
    Buffer Id: 0x00000114
    Total length: 90
    In port: 1
    Reason: No matching flow (table-miss flow entry) (0)
    Pad: 00
    Ethernet II, Src: ca:8e:28:f6:9e:15 (ca:8e:28:f6:9e:15), Dst: IPv6mcast_16 (33:33:00:00:00:16)
        Destination: IPv6mcast_16 (33:33:00:00:00:16)
            Address: IPv6mcast_16 (33:33:00:00:00:16)
            .... ..1. .... .... .... .... = LG bit: Locally administered address (this is NOT the factory default)
            .... ...1 .... .... .... .... = IG bit: Group address (multicast/broadcast)
        Source: ca:8e:28:f6:9e:15 (ca:8e:28:f6:9e:15)
            Address: ca:8e:28:f6:9e:15 (ca:8e:28:f6:9e:15)
            .... ..1. .... .... .... .... = LG bit: Locally administered address (this is NOT the factory default)
            .... ...0 .... .... .... .... = IG bit: Individual address (unicast)
        Type: IPv6 (0x86dd)
    Internet Protocol Version 6, Src: fe80::c88e:28ff:fef6:9e15, Dst: ff02::16
        0110 .... = Version: 6
        .... 0000 0000 .... .... .... .... .... = Traffic Class: 0x00 (DSCP: CS0, ECN: Not-ECT)
            .... 0000 00.. .... .... .... .... .... = Differentiated Services Codepoint: Default (0)
            .... .... ..00 .... .... .... .... .... = Explicit Congestion Notification: Not ECN-Capable Transport (0)
        .... .... .... 0000 0000 0000 0000 0000 = Flow Label: 0x00000
        Payload Length: 36
        Next Header: IPv6 Hop-by-Hop Option (0)
        Hop Limit: 1
        Source: fe80::c88e:28ff:fef6:9e15
        Destination: ff02::16
        IPv6 Hop-by-Hop Option
            Next Header: ICMPv6 (58)
            Length: 0
            [Length: 8 bytes]
            Router Alert
            PadN
    Internet Control Message Protocol v6
        Type: Multicast Listener Report Message v2 (143)
        Code: 0
        Checksum: 0x4363 [correct]
        [Checksum Status: Good]
        Reserved: 0000
        Number of Multicast Address Records: 1
        Multicast Address Record Changed to exclude: ff02::1:fff6:9e15
            Record Type: Changed to exclude (4)
            Aux Data Len: 0
            Number of Sources: 0
            Multicast Address: ff02::1:fff6:9e15

6、Packet_out

控制器6633端口（请按照我给你的action进行处理） ---> 交换机56998端口

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*/
    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*/
    uint16_t actions_len; /*action列表的长度，可以用来区分actions和data段*/
    struct ofp_action_header actions[0]; /*动作列表*/
    uint8_t data[0]; /*数据缓存区，可以存储一个以太网帧，可选*/
}

告诉输出到交换机的65531端口

Frame 561: 92 bytes on wire (736 bits), 92 bytes captured (736 bits) on interface 0
Linux cooked capture
Internet Protocol Version 4, Src: 127.0.0.1, Dst: 127.0.0.1
Transmission Control Protocol, Src Port: 6633, Dst Port: 57002, Seq: 485, Ack: 2589, Len: 24
OpenFlow 1.0
    .000 0001 = Version: 1.0 (0x01)
    Type: OFPT_PACKET_OUT (13)
    Length: 24
    Transaction ID: 0
    Buffer Id: 0x00000113
    In port: 1
    Actions length: 8
    Actions type: Output to switch port (0)
    Action length: 8
    Output port: 65531
Max length: 0

8、接下来是另一台交换机（端口54556）与控制器（端口6633）的交互过程

h1 ping h2

packet_in

flow_mod结合flow_mod结构

struct ofp_flow_mod {
    struct ofp_header header;
    struct ofp_match match; /*流表的匹配域*/ 
    uint64_t cookie; /*流表项标识符*/
    uint16_t command; /*可以是ADD,DELETE,DELETE-STRICT,MODIFY,MODIFY-STRICT*/
    uint16_t idle_timeout; /*空闲超时时间*/
    uint16_t hard_timeout; /*最大生存时间*/
    uint16_t priority; /*优先级，优先级高的流表项优先匹配*/
    uint32_t buffer_id; /*缓存区ID ,用于指定缓存区中的一个数据包按这个消息的action列表处理*/  
    uint16_t out_port; /*如果这条消息是用于删除流表则需要提供额外的匹配参数*/
    uint16_t flags; /*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]; /*action列表*/
};

Frame 1165: 156 bytes on wire (1248 bits), 156 bytes captured (1248 bits) on interface 0
Linux cooked capture
Internet Protocol Version 4, Src: 127.0.0.1, Dst: 127.0.0.1
Transmission Control Protocol, Src Port: 57002, Dst Port: 6633, Seq: 5809, Ack: 1781, Len: 88
OpenFlow 1.0
    .000 0001 = Version: 1.0 (0x01)
    Type: OFPT_PACKET_IN (10)
    Length: 88
    Transaction ID: 0
    Buffer Id: 0x00000131
    Total length: 70
    In port: 2
    Reason: No matching flow (table-miss flow entry) (0)
    Pad: 00
    Ethernet II, Src: 62:1b:62:a8:4b:13 (62:1b:62:a8:4b:13), Dst: IPv6mcast_02 (33:33:00:00:00:02)
        Destination: IPv6mcast_02 (33:33:00:00:00:02)
            Address: IPv6mcast_02 (33:33:00:00:00:02)
            .... ..1. .... .... .... .... = LG bit: Locally administered address (this is NOT the factory default)
            .... ...1 .... .... .... .... = IG bit: Group address (multicast/broadcast)
        Source: 62:1b:62:a8:4b:13 (62:1b:62:a8:4b:13)
            Address: 62:1b:62:a8:4b:13 (62:1b:62:a8:4b:13)
            .... ..1. .... .... .... .... = LG bit: Locally administered address (this is NOT the factory default)
            .... ...0 .... .... .... .... = IG bit: Individual address (unicast)
        Type: IPv6 (0x86dd)
    Internet Protocol Version 6, Src: fe80::601b:62ff:fea8:4b13, Dst: ff02::2
        0110 .... = Version: 6
        .... 0000 0000 .... .... .... .... .... = Traffic Class: 0x00 (DSCP: CS0, ECN: Not-ECT)
            .... 0000 00.. .... .... .... .... .... = Differentiated Services Codepoint: Default (0)
            .... .... ..00 .... .... .... .... .... = Explicit Congestion Notification: Not ECN-Capable Transport (0)
        .... .... .... 0000 0000 0000 0000 0000 = Flow Label: 0x00000
        Payload Length: 16
        Next Header: ICMPv6 (58)
        Hop Limit: 255
        Source: fe80::601b:62ff:fea8:4b13
        Destination: ff02::2
    Internet Control Message Protocol v6
        Type: Router Solicitation (133)
        Code: 0
        Checksum: 0x5f80 [correct]
        [Checksum Status: Good]
        Reserved: 00000000
        ICMPv6 Option (Source link-layer address : 62:1b:62:a8:4b:13)
            Type: Source link-layer address (1)
            Length: 1 (8 bytes)
            Link-layer address: 62:1b:62:a8:4b:13 (62:1b:62:a8:4b:13)

分析抓取的flow_mod数据包，控制器通过6633端口向交换机56998端口、交换机56998端口下发流表项，指导数据的转发处理

3、把控制器从openflow reference改成ovs controller

1、控制器配置

2、HELLO

控制器6633端口可支持OpenFlow 1.3协议了

3、flow_mod

双方协商使用OpenFlow 1.3进行通信