1. 當(dāng)前環(huán)境

[root@vm1 ~]# ovs-vsctl show
c152c245-2f6c-478c-9c07-2e4a3c7a2403
[root@vm1 ~]# cat /proc/sys/net/ipv4/ip_forward
0
[root@vm1 ~]# iptables -t nat -F
[root@vm1 ~]# route -n
Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
0.0.0.0         172.19.0.1      0.0.0.0         UG    0      0        0 eth0
169.254.0.0     0.0.0.0         255.255.0.0     U     1002   0        0 eth0
172.19.0.0      0.0.0.0         255.255.240.0   U     0      0        0 eth0

安裝ovs可以參考 在 Centos 上安裝 ovs

2. 用ovs模擬docker

添加一個(gè)ovs 網(wǎng)橋br0 并且配置ip為192.168.1.250/24

[root@vm1 ~]# ovs-vsctl add-br br0 
[root@vm1 ~]# ovs-vsctl show
c152c245-2f6c-478c-9c07-2e4a3c7a2403
    Bridge "br0"
        Port "br0"
            Interface "br0"
                type: internal
    ovs_version: "2.5.1"
[root@vm1 ~]# ifconfig br0 192.168.1.250/24 
[root@vm1 ~]# ifconfig br0
br0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        inet 192.168.1.250  netmask 255.255.255.0  broadcast 192.168.1.255
        inet6 fe80::c0b6:92ff:fe4d:7649  prefixlen 64  scopeid 0x20<link>
        ether c2:b6:92:4d:76:49  txqueuelen 1000  (Ethernet)
        RX packets 0  bytes 0 (0.0 B)
        RX errors 0  dropped 8  overruns 0  frame 0
        TX packets 6  bytes 508 (508.0 B)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

創(chuàng)建一個(gè)network namespace ns1, 創(chuàng)建一對(duì)veth為veth0和veth1, 將veth0加入到br0中, 將veth1加入到ns1中, 并且給ns1配置ip為192.168.1.1/24.

// 創(chuàng)建一個(gè)network namespace ns1
[root@vm1 ~]# ip netns add ns1
// 創(chuàng)建一對(duì)veth pair (veth0 和 veth1)
[root@vm1 ~]# ip link add veth0 type veth peer name veth1
// 將veth0加入到br0中
[root@vm1 ~]# ip link set veth0 up
[root@vm1 ~]# ovs-vsctl add-port br0 veth0
[root@vm1 ~]# ovs-vsctl show
c152c245-2f6c-478c-9c07-2e4a3c7a2403
    Bridge "br0"
        Port "veth0"
            Interface "veth0"
        Port "br0"
            Interface "br0"
                type: internal
    ovs_version: "2.5.1"
[root@vm1 ~]# 
// 將veth1加入到ns1中
[root@vm1 ~]# ip link set veth1 netns ns1
// 設(shè)置veth1 ip 與br0是同一個(gè)網(wǎng)絡(luò)
[root@vm1 ~]# ip netns exec ns1 ip addr add 192.168.1.1/24 dev veth1
[root@vm1 ~]# ip netns exec ns1 ip link set veth1 up
[root@vm1 ~]# ip netns exec ns1 ip link set lo up
// 在ns1中ping br0成功
[root@vm1 ~]# ip netns exec ns1 ping -c 1 192.168.1.250
PING 192.168.1.250 (192.168.1.250) 56(84) bytes of data.
64 bytes from 192.168.1.250: icmp_seq=1 ttl=64 time=0.392 ms

--- 192.168.1.250 ping statistics ---
1 packets transmitted, 1 received, 0% packet loss, time 0ms
rtt min/avg/max/mdev = 0.392/0.392/0.392/0.000 ms

給ns1增加路由

[root@vm1 ~]# ip netns exec ns1 route add default gw 192.168.1.250
[root@vm1 ~]# ip netns exec ns1 ping -c 1 172.19.0.12
PING 172.19.0.12 (172.19.0.12) 56(84) bytes of data.
64 bytes from 172.19.0.12: icmp_seq=1 ttl=64 time=0.224 ms

--- 172.19.0.12 ping statistics ---
1 packets transmitted, 1 received, 0% packet loss, time 0ms
rtt min/avg/max/mdev = 0.224/0.224/0.224/0.000 ms

打開ip_forward功能和加iptables規(guī)則

[root@vm1 ~]# echo 1 > /proc/sys/net/ipv4/ip_forward
[root@vm1 ~]# iptables -t nat -A POSTROUTING -s 192.168.1.0/24 -o eth0 -j MASQUERADE
[root@vm1 ~]# ip netns exec ns1 ping -c 1 www.baidu.com
PING www.wshifen.com (103.235.46.39) 56(84) bytes of data.
64 bytes from 103.235.46.39 (103.235.46.39): icmp_seq=1 ttl=55 time=1.77 ms

--- www.wshifen.com ping statistics ---
1 packets transmitted, 1 received, 0% packet loss, time 0ms
rtt min/avg/max/mdev = 1.772/1.772/1.772/0.000 ms
[root@vm1 ~]# 

3. ovs-docker

3.1 配置

[root@vm1 ~]# docker version
Client:
 Version:           18.09.6
[root@vm1 ~]# docker run -d --name con1 --net=none busybox top
[root@vm1 ~]# docker exec -it con1 ifconfig
lo        Link encap:Local Loopback  
          inet addr:127.0.0.1  Mask:255.0.0.0
          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:1000 
          RX bytes:0 (0.0 B)  TX bytes:0 (0.0 B)
// 此時(shí)利用ovs-docker 設(shè)置此容器ip地址為192.168.1.2/24  網(wǎng)關(guān)為192.168.1.250
[root@vm1 ~]# ovs-docker add-port br0 eth0 con1 --ipaddress=192.168.1.2/24 --gateway=192.168.1.250
[root@vm1 ~]# docker exec -it con1 ifconfig
eth0      Link encap:Ethernet  HWaddr 56:39:36:6A:B0:61  
          inet addr:192.168.1.2  Bcast:0.0.0.0  Mask:255.255.255.0
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:7 errors:0 dropped:0 overruns:0 frame:0
          TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:578 (578.0 B)  TX bytes:0 (0.0 B)

lo        Link encap:Local Loopback  
          inet addr:127.0.0.1  Mask:255.0.0.0
          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:1000 
          RX bytes:0 (0.0 B)  TX bytes:0 (0.0 B)

[root@vm1 ~]# docker exec -it con1 route -n
Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
0.0.0.0         192.168.1.250   0.0.0.0         UG    0      0        0 eth0
192.168.1.0     0.0.0.0         255.255.255.0   U     0      0        0 eth0
[root@vm1 ~]# ovs-vsctl show
c152c245-2f6c-478c-9c07-2e4a3c7a2403
    Bridge "br0"
        Port "veth0"
            Interface "veth0"
        Port "7506959a37594_l"
            Interface "7506959a37594_l"
        Port "br0"
            Interface "br0"
                type: internal
    ovs_version: "2.5.1"
[root@vm1 ~]# 

從上面結(jié)果可以知道ovs-docker所做的操作的就是2. 用ovs模擬docker中所做的內(nèi)容,說(shuō)白了就是一些shell命令的集合.

3.2 測(cè)試

// 訪問(wèn)br0
[root@vm1 ~]# docker exec -it con1 ping -c 1 192.168.1.250
PING 192.168.1.250 (192.168.1.250): 56 data bytes
64 bytes from 192.168.1.250: seq=0 ttl=64 time=3.972 ms

--- 192.168.1.250 ping statistics ---
1 packets transmitted, 1 packets received, 0% packet loss
round-trip min/avg/max = 3.972/3.972/3.972 ms
// 訪問(wèn)ns1
[root@vm1 ~]# docker exec -it con1 ping -c 1 192.168.1.1
PING 192.168.1.1 (192.168.1.1): 56 data bytes
64 bytes from 192.168.1.1: seq=0 ttl=64 time=3.751 ms

--- 192.168.1.1 ping statistics ---
1 packets transmitted, 1 packets received, 0% packet loss
round-trip min/avg/max = 3.751/3.751/3.751 ms
// 訪問(wèn)本機(jī)ip
[root@vm1 ~]# docker exec -it con1 ping -c 1 172.19.0.12
PING 172.19.0.12 (172.19.0.12): 56 data bytes
64 bytes from 172.19.0.12: seq=0 ttl=64 time=4.743 ms

--- 172.19.0.12 ping statistics ---
1 packets transmitted, 1 packets received, 0% packet loss
round-trip min/avg/max = 4.743/4.743/4.743 ms
// 訪問(wèn)另外一臺(tái)機(jī)器vm2
[root@vm1 ~]# docker exec -it con1 ping -c 1 172.19.0.8
PING 172.19.0.8 (172.19.0.8): 56 data bytes
64 bytes from 172.19.0.8: seq=0 ttl=63 time=3.829 ms

--- 172.19.0.8 ping statistics ---
1 packets transmitted, 1 packets received, 0% packet loss
round-trip min/avg/max = 3.829/3.829/3.829 ms
// 訪問(wèn)互聯(lián)網(wǎng)
[root@vm1 ~]# docker exec -it con1 ping -c 1 www.baidu.com
PING www.baidu.com (119.63.197.151): 56 data bytes
64 bytes from 119.63.197.151: seq=0 ttl=49 time=50.983 ms

--- www.baidu.com ping statistics ---
1 packets transmitted, 1 packets received, 0% packet loss
round-trip min/avg/max = 50.983/50.983/50.983 ms

從ns1中訪問(wèn)con1

[root@vm1 ~]# ip netns exec ns1 ping -c 1 192.168.1.2
PING 192.168.1.2 (192.168.1.2) 56(84) bytes of data.
64 bytes from 192.168.1.2: icmp_seq=1 ttl=64 time=0.230 ms

--- 192.168.1.2 ping statistics ---
1 packets transmitted, 1 received, 0% packet loss, time 0ms
rtt min/avg/max/mdev = 0.230/0.230/0.230/0.000 ms
[root@vm1 ~]# 

如果ovs-docker 配置不成功, 可以在創(chuàng)建容器的時(shí)候加上--privileged=true.

3.3 ovs-docker 原理

源碼訪問(wèn) http://github.com/openvswitch/ovs/raw/master/utilities/ovs-docker

...

add_port () {
    BRIDGE="$1"
    INTERFACE="$2"
    CONTAINER="$3"

    if [ -z "$BRIDGE" ] || [ -z "$INTERFACE" ] || [ -z "$CONTAINER" ]; then
        echo >&2 "$UTIL add-port: not enough arguments (use --help for help)"
        exit 1
    fi

    shift 3
    while [ $# -ne 0 ]; do
        case $1 in
            --ipaddress=*)
                ADDRESS=`expr X"$1" : 'X[^=]*=\(.*\)'`
                shift
                ;;
            --macaddress=*)
                MACADDRESS=`expr X"$1" : 'X[^=]*=\(.*\)'`
                shift
                ;;
            --gateway=*)
                GATEWAY=`expr X"$1" : 'X[^=]*=\(.*\)'`
                shift
                ;;
            --mtu=*)
                MTU=`expr X"$1" : 'X[^=]*=\(.*\)'`
                shift
                ;;
            *)
                echo >&2 "$UTIL add-port: unknown option \"$1\""
                exit 1
                ;;
        esac
    done

    # Check if a port is already attached for the given container and interface
    PORT=`get_port_for_container_interface "$CONTAINER" "$INTERFACE" \
            2>/dev/null`
    if [ -n "$PORT" ]; then
        echo >&2 "$UTIL: Port already attached" \
                 "for CONTAINER=$CONTAINER and INTERFACE=$INTERFACE"
        exit 1
    fi

    if ovs_vsctl br-exists "$BRIDGE" || \
        ovs_vsctl add-br "$BRIDGE"; then :; else
        echo >&2 "$UTIL: Failed to create bridge $BRIDGE"
        exit 1
    fi

    if PID=`docker inspect -f '{{.State.Pid}}' "$CONTAINER"`; then :; else
        echo >&2 "$UTIL: Failed to get the PID of the container"
        exit 1
    fi

    create_netns_link

    # Create a veth pair.
    ID=`uuidgen | sed 's/-//g'`
    PORTNAME="${ID:0:13}"
    ip link add "${PORTNAME}_l" type veth peer name "${PORTNAME}_c"

    # Add one end of veth to OVS bridge.
    if ovs_vsctl --may-exist add-port "$BRIDGE" "${PORTNAME}_l" \
       -- set interface "${PORTNAME}_l" \
       external_ids:container_id="$CONTAINER" \
       external_ids:container_iface="$INTERFACE"; then :; else
        echo >&2 "$UTIL: Failed to add "${PORTNAME}_l" port to bridge $BRIDGE"
        ip link delete "${PORTNAME}_l"
        exit 1
    fi

    ip link set "${PORTNAME}_l" up

    # Move "${PORTNAME}_c" inside the container and changes its name.
    ip link set "${PORTNAME}_c" netns "$PID"
    ip netns exec "$PID" ip link set dev "${PORTNAME}_c" name "$INTERFACE"
    ip netns exec "$PID" ip link set "$INTERFACE" up

    if [ -n "$MTU" ]; then
        ip netns exec "$PID" ip link set dev "$INTERFACE" mtu "$MTU"
    fi

    if [ -n "$ADDRESS" ]; then
        ip netns exec "$PID" ip addr add "$ADDRESS" dev "$INTERFACE"
    fi

    if [ -n "$MACADDRESS" ]; then
        ip netns exec "$PID" ip link set dev "$INTERFACE" address "$MACADDRESS"
    fi

    if [ -n "$GATEWAY" ]; then
        ip netns exec "$PID" ip route add default via "$GATEWAY"
    fi
}
...

很簡(jiǎn)單就看到這個(gè)方法就是ovs-docker剛才的操作過(guò)程, 基本上也就是2. 用ovs模擬docker的基礎(chǔ)上加入了一些判斷.

4. 參考

1. https://blog.csdn.net/silvester123/article/details/80867168
2. https://blog.csdn.net/yeya24/article/details/79829240