更改docker容器中的默认路由

Question

我有一个连接到两个网络的docker容器,默认桥和自定义桥.通过默认设置,它仅链接到默认网络中的另一个容器,并通过自定义网桥,在本地网络中获取IP地址.

LAN -- [homenet] -- container1 -- [bridge] -- container2

sudo docker network inspect homenet
[{  "Name": "homenet",
    "Scope": "local",
    "Driver": "bridge",
    "EnableIPv6": false,
    "IPAM": {
        "Driver": "default",
        "Options": {},
        "Config": [{ "Subnet": "192.168.130.0/24",
                     "Gateway": "192.168.130.8",
                     "AuxiliaryAddresses": { "DefaultGatewayIPv4": "192.168.130.3" }}]
    },
    "Internal": false,
    "Containers": {
        "$cid1": { "Name": "container",
                   "EndpointID": "$eid1_1",
                   "MacAddress": "$mac1_1",
                   "IPv4Address": "192.168.130.38/24", }
    },
    "Options": { "com.docker.network.bridge.name": "br-homenet" },
    "Labels": {}}]

和桥:

sudo docker network inspect bridge

[{
    "Name": "bridge",
    "Scope": "local",
    "Driver": "bridge",
    "EnableIPv6": false,
    "IPAM": {
        "Driver": "default",
        "Options": null,
        "Config": [{ "Subnet": "172.17.0.0/16" }]
    },
    "Internal": false,
    "Containers": { 
      "$cid2": {
            "Name": "container2",
            "EndpointID": "$eid2",
            "MacAddress": "$mac2",
            "IPv4Address": "172.17.0.2/16",
            "IPv6Address": "" }, 
      "$cid1": {
            "Name": "container1",
            "EndpointID": "$eid1_2",
            "MacAddress": "$mac1_2",
            "IPv4Address": "172.17.0.3/16",
            "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": {}
}]

这在内部网络中运行良好,但是,我有一个路由问题:

sudo  docker exec -it container1 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
192.168.130.0   0.0.0.0         255.255.255.0   U     0      0        0 eth1

如何将默认路由更改为192.169.130.3以使其持续重启？

我可以在container1运行时更改它

 pid=$(sudo docker inspect -f '{{.State.Pid}}' container1)
 sudo mkdir -p /var/run/netns
 sudo ln -s /proc/$pid/ns/net /var/run/netns/$pid
 sudo ip netns exec $pid ip route del default 
 sudo ip netns exec $pid ip route add default via 192.168.130.3

但是重新启动后它就消失了.我怎么能改变呢？

更新:显然,网络的字典顺序也可能是问题的一部分.我有机会的时候会测试它.

Answer 1

如果我理解了这个问题,问题是:当重新启动连接到多个网桥的容器时,如何选择一个网桥用于默认路由？

我搜索了可用的选项并进行了一些测试,我没有找到任何docker命令行选项来指定默认路由,或者在容器连接到多个网桥时更喜欢桥接器.当我重新启动连接到默认网桥(bridge)和自定义网桥(您的homenet)的容器时,默认路由会自动设置为使用默认网桥(网关172.17.0.1).这与您描述的行为相对应.

解决方案1:在运行命令中指定一个启动脚本,用于更改默认路由并启动容器必须运行的服务:

docker run \
  --cap-add NET_ADMIN \ # to allow changing net settings inside the container 
  --name container1 \
  --restart always \ # restart policy
  your_image \
  /path/to/your_start_script.sh

的your_start_script.sh:

ip route del default 
ip route add default via 192.168.130.3

# here goes instructions/services your container is supposed to run

此脚本必须在容器内可用,它可以位于共享文件夹(-v选项)上,也可以在带有Dockerfile的映像构建中加载.

注意:在将容器连接到自定义网桥(docker network connect homenet container1)之前,your_start_script.sh由于默认路由与任何可用网络都不对应,因此会崩溃.

我测试了记录ip route内部container1运行的输出--restart always,在将其连接到自定义网桥后,它具有所需的默认路由.

解决方案2:在容器启动事件上设置容器默认路由来自主机

docker events --filter "container=container1" |\
  awk '/container start/ { system("/path/to/route_setting.sh") }'

其中route_setting.sh包含更改容器默认路由的说明:

pid=$(sudo docker inspect -f '{{.State.Pid}}' container1)
sudo mkdir -p /var/run/netns
sudo ln -s /proc/$pid/ns/net /var/run/netns/$pid
sudo ip netns exec $pid ip route del default 
sudo ip netns exec $pid ip route add default via 192.168.130.3

此解决方案避免为容器提供特殊权限,并将路由更改责任转移给主机.

Answer 2

可以使用nsenter命令进入容器的命名空间，然后在其中执行命令。大约这样：

nsenter -n -t $(docker inspect --format {{.State.Pid}} $dockername) ip route add something.
nsenter -n -t $(docker inspect --format {{.State.Pid}} $dockername) ip route del something.