find_veth_docker

Simple script to find out which veth interface on the host corresponds to the eth0 interface of a container

Changelog

12/11/2024

Add image info to the output as a new column

30/05/2023

Added more inspections for each container considered. Besides veth information:

• we have the IP address of the container, which can be useful when some service is running inside and we want to use it from the host (e.g., DNSproxy, pihole)
• MAC address: can be useful, for instance, when crafting packets from the host and sending them into the container
• Bridge: the docker bridge on the host the container's veth is connected virtually

New dependency: jq for parsing JSON-output of docker inspect commands. Dependency checked when running the script. If it fails, please install jq.

05/05/2023

There is no requirement anymore. The script has been refactored and rethought and now does not have any dependency from the containers. Whatever container you are running, the veth interface can be identified.

18/08/2023

When defining your own network stack, do not use dashes ('-') in the network name. Use only underscores ('_'). For instance, in your docker-compose.yml, follow this approach

networks:
  internal:
    name: adguard_proxy_network
    ipam:
      config:
        - subnet: 172.22.1.0/24

Mind the '_' in the name field.

Usage

This script finds out which vethXXXX is connected to what container!
Example: sudo ./find_veth_docker.sh -n <CONTAINER_NAME> -i <INTEFACE_IN_CONTAINER>
		-n <CONTAINER_NAME>: set here the name of the container (Default: No name specified, printing all containers' data).
		-i <INTERFACE_IN_CONTAINER>: set here the name of the interface in the container (Default: eth0).

Example

sudo ./find_veth_docker.sh
Testing dependencies (jq)...                                                                                                                                                                [DONE]
VETH@HOST	VETH_MAC		CONTAINER_IP	CONTAINER_MAC		Bridge@HOST		Bridge_IP	Bridge_MAC		CONTAINER		Image
veth760591f	3e:1c:6e:95:85:8b	172.30.1.3	02:42:ac:1e:01:03	br-d1b495712e0c		172.30.1.1/24	02:42:e6:48:e9:64	pihole		pihole/pihole:latest
veth8d60e9b	6a:29:dc:42:85:77	172.30.1.4	02:42:ac:1e:01:04	br-d1b495712e0c		172.30.1.1/24	02:42:e6:48:e9:64	dnscrypt-proxy	klutchell/dnscrypt-proxy
veth41b3b1f	16:7e:62:95:b4:b5	172.19.1.2	02:42:ac:13:01:02	br-d9a1a1f4fb28		172.19.1.1/24	02:42:83:ac:7e:dd	portainer	cr.portainer.io/portainer/portainer-ce:latest

Or, if you know the container name, you can filter on it immediately.

sudo ./find_veth_docker.sh -n pihole
Testing dependencies (jq)...                                                                                                                                                                [DONE]
VETH@HOST	VETH_MAC		CONTAINER_IP	CONTAINER_MAC		Bridge@HOST		Bridge_IP	Bridge_MAC		CONTAINER		Image
veth760591f	3e:1c:6e:95:85:8b	172.30.1.3	02:42:ac:1e:01:03	br-d1b495712e0c		172.30.1.1/24	02:42:e6:48:e9:64	pihole		pihole/pihole:latest

Using output for scripts

You might want to change some settings for a particular container's vethXXXX device. Let's take an example of ethtool that disables checksumming on the interfaces.

sudo ethtool -K $(./find_veth_docker.sh -n google |grep -v @|awk '{print $1}') tx off rx off