Find out which network interface belongs to docker container
Docker creates these virtual ethernet interfaces veth[UNIQUE ID] listed in ifconfig. How can I find out which interface belongs to a specific docker container?
I want to listen to the tcp traffic.
Answer
To locate interface
In my case getting value from container was like (check eth0 to):
$ docker exec -it my-container cat /sys/class/net/eth1/iflink
123
And then:
$ ip ad | grep 123
123: vethd3234u4@if122: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue master docker_gwbridge state UP group default
Check with tcpdump -i vethd3234u4
Reference about mysterious iflink from http://lxr.free-electrons.com/source/Documentation/ABI/testing/sysfs-class-net:
150 What: /sys/class/net/<iface>/iflink
151 Date: April 2005
152 KernelVersion: 2.6.12
153 Contact: [email protected]
154 Description:
155 Indicates the system-wide interface unique index identifier a
156 the interface is linked to. Format is decimal. This attribute is
157 used to resolve interfaces chaining, linking and stacking.
158 Physical interfaces have the same 'ifindex' and 'iflink' values.