Docker - 虚拟网桥

容器的网络模式

• None --- 容器不能访问外部网络，内部存在回路地址。
• Container --- 将容器的网络栈合并到一起，可与其他容器共享网络。
• Host --- 与主机共享网络。
• Bridge --- 默认网络模式，通过主机和容器的端口映射（iptable转发）来通信。桥接是在主机上，一般叫docker0。
• 自定义网络 --- 主要是为了解决 docker 跨网络通信能力不足的问题和特殊网络需求问题。主要包括：桥接网络、插件网络和Overlay网络（原生的跨主机多子网模型）。

Docker安装后会创建自带的三种网络，可以通过docker network ls查看，通过docker network inspect查看详细信息。

[root@CentOS-7 ~]# docker network ls
NETWORK ID          NAME                DRIVER
08b080b94bcf        bridge              bridge
cff410b272fe        none                null
e818cf59d997        host                host
[root@CentOS-7 ~]#
[root@CentOS-7 ~]# docker network inspect bridge
[
    {
        "Name": "bridge",
        "Id": "08b080b94bcf5b8a651f27f6954d094eb6c41a200c969a8f80beb0b155655bd9",
        "Scope": "local",
        "Driver": "bridge",
        "IPAM": {
            "Driver": "default",
            "Options": null,
            "Config": [
                {
                    "Subnet": "172.17.0.0/16"
                }
            ]
        },
        "Containers": {},
        "Options": {
            "com.docker.network.bridge.default_bridge": "true",
            "com.docker.network.bridge.enable_icc": "true",
            "com.docker.network.bridge.enable_ip_masquerade": "true",
            "com.docker.network.bridge.host_binding_ipv4": "0.0.0.0",
            "com.docker.network.bridge.name": "docker0",
            "com.docker.network.driver.mtu": "1500"
        }
    }
]
[root@CentOS-7 ~]#

虚拟网桥

Docker启动时，自动在主机上创建虚拟网桥docker0，并随机分配一个本地空闲私有网段的一个地址给docker0接口。

虚拟网桥docker0在内核层连通了其他的物理或虚拟网卡，将所有容器和本地主机都放到同一个网络。

docker0接口的默认配置包含了IP地址、子网掩码等，可以在docker服务启动的时候进行自定义配置。

[root@CentOS-7 ~]# ip addr show docker0
5: docker0: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc noqueue state DOWN
    link/ether 02:42:41:3d:c1:6a brd ff:ff:ff:ff:ff:ff
    inet 172.17.0.1/16 scope global docker0
       valid_lft forever preferred_lft forever
    inet6 fe80::42:41ff:fe3d:c16a/64 scope link
       valid_lft forever preferred_lft forever
[root@CentOS-7 ~]#
[root@CentOS-7 ~]# brctl show docker0
bridge name	bridge id		STP enabled	interfaces
docker0		8000.0242413dc16a	no		veth06f0e1b
[root@CentOS-7 ~]#
[root@CentOS-7 ~]# docker network ls
NETWORK ID          NAME                DRIVER              SCOPE
1d732a1c4f67        bridge              bridge              local
2e217e480705        host                host                local
c31d9a1acfc0        none                null                local
[root@CentOS-7 ~]#
[root@CentOS-7 ~]# docker network inspect bridge
[
    {
        "Name": "bridge",
        "Id": "1d732a1c4f67d124eebfa1ccc19c299f9e0ed88f5f429f7bc5f4d6c263f9d599",
        "Scope": "local",
        "Driver": "bridge",
        "EnableIPv6": false,
        "IPAM": {
            "Driver": "default",
            "Options": null,
            "Config": [
                {
                    "Subnet": "172.17.0.0/16",
                    "Gateway": "172.17.0.1"
                }
            ]
        },
        "Internal": false,
        "Containers": {},
        "Options": {
            "com.docker.network.bridge.default_bridge": "true",
            "com.docker.network.bridge.enable_icc": "true",
            "com.docker.network.bridge.enable_ip_masquerade": "true",
            "com.docker.network.bridge.host_binding_ipv4": "0.0.0.0",
            "com.docker.network.bridge.name": "docker0",
            "com.docker.network.driver.mtu": "1500"
        },
        "Labels": {}
    }
]
[root@CentOS-7 ~]#

容器的默认网络

Bridge是容器启动的默认网络模式。

当创建一个Docker容器时，容器会自动获得Bridge网段的一个空闲IP地址，并使用docker0接口的IP地址作为容器的默认网关，从而建立了主机和容器之间的一个虚拟共享网络。

主机可以跟容器通信，容器之间也可以相互通信。

容器通过docker0网桥以nat方式连接外网，外网通过端口映射（-p参数）连接到容器。

[root@CentOS-7 ~]# docker run -it -d --name test-network docker.io/ubuntu /bin/bash
7fb2253c974113452a534b0b423e5d62ca45243272f68f6f36726f3b71088816
[root@CentOS-7 ~]#
[root@CentOS7 ~]# ip link show |grep docker0
3: docker0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP mode DEFAULT
7: veth6e8b8d1@if7: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue master docker0 state UP mode DEFAULT
[root@CentOS7 ~]#
[root@CentOS-7 ~]# docker network inspect bridge
[
    {
        "Name": "bridge",
        "Id": "1d732a1c4f67d124eebfa1ccc19c299f9e0ed88f5f429f7bc5f4d6c263f9d599",
        "Scope": "local",
        "Driver": "bridge",
        "EnableIPv6": false,
        "IPAM": {
            "Driver": "default",
            "Options": null,
            "Config": [
                {
                    "Subnet": "172.17.0.0/16",
                    "Gateway": "172.17.0.1"
                }
            ]
        },
        "Internal": false,
        "Containers": {
            "7fb2253c974113452a534b0b423e5d62ca45243272f68f6f36726f3b71088816": {
                "Name": "test-network",
                "EndpointID": "d434340768b76da42f9d61da848aa197111826c38eaca05886bca17c42123de3",
                "MacAddress": "02:42:ac:11:00:02",
                "IPv4Address": "172.17.0.2/16",
                "IPv6Address": ""
            }
        },
        "Options": {
            "com.docker.network.bridge.default_bridge": "true",
            "com.docker.network.bridge.enable_icc": "true",
            "com.docker.network.bridge.enable_ip_masquerade": "true",
            "com.docker.network.bridge.host_binding_ipv4": "0.0.0.0",
            "com.docker.network.bridge.name": "docker0",
            "com.docker.network.driver.mtu": "1500"
        },
        "Labels": {}
    }
]
[root@CentOS-7 ~]#
[root@CentOS-7 ~]# docker attach test-network
root@7fb2253c9741:/#
root@7fb2253c9741:/# export http_proxy="http://10.144.1.10:8080"
root@7fb2253c9741:/#
root@7fb2253c9741:/# apt-get update
root@7fb2253c9741:/# apt-get install -yqq inetutils-ping
root@7fb2253c9741:/# apt-get install -yqq iproute
root@7fb2253c9741:/# apt-get install -yqq net-tools
root@7fb2253c9741:/#
root@7fb2253c9741:/# ifconfig -a
eth0      Link encap:Ethernet  HWaddr 02:42:ac:11:00:02
          inet addr:172.17.0.2  Bcast:0.0.0.0  Mask:255.255.0.0
          inet6 addr: fe80::42:acff:fe11:2/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:10951 errors:0 dropped:0 overruns:0 frame:0
          TX packets:7358 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0
          RX bytes:26672806 (26.6 MB)  TX bytes:495091 (495.0 KB)

lo        Link encap:Local Loopback
          inet addr:127.0.0.1  Mask:255.0.0.0
          inet6 addr: ::1/128 Scope:Host
          UP LOOPBACK RUNNING  MTU:65536  Metric:1
          RX packets:0 errors:0 dropped:0 overruns:0 frame:0
          TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0
          RX bytes:0 (0.0 B)  TX bytes:0 (0.0 B)

root@7fb2253c9741:/#
root@7fb2253c9741:/# route -n
Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
0.0.0.0         172.17.0.1      0.0.0.0         UG    0      0        0 eth0
172.17.0.0      0.0.0.0         255.255.0.0     U     0      0        0 eth0
root@7fb2253c9741:/#
root@7fb2253c9741:/# ping 172.17.0.1
PING 172.17.0.1 (172.17.0.1): 56 data bytes
64 bytes from 172.17.0.1: icmp_seq=0 ttl=64 time=0.235 ms
64 bytes from 172.17.0.1: icmp_seq=1 ttl=64 time=0.254 ms
^C--- 172.17.0.1 ping statistics ---
2 packets transmitted, 2 packets received, 0% packet loss
round-trip min/avg/max/stddev = 0.235/0.244/0.254/0.000 ms
root@7fb2253c9741:/#
root@7fb2253c9741:/# ping www.bing.com
PING a-0001.a-msedge.net (204.79.197.200): 56 data bytes
64 bytes from 204.79.197.200: icmp_seq=0 ttl=108 time=205.742 ms
64 bytes from 204.79.197.200: icmp_seq=1 ttl=108 time=207.676 ms
^C--- a-0001.a-msedge.net ping statistics ---
2 packets transmitted, 2 packets received, 0% packet loss
round-trip min/avg/max/stddev = 205.742/206.709/207.676/0.967 ms
root@7fb2253c9741:/# [root@CentOS-7 ~]#
[root@CentOS-7 ~]#