Tiny howto, so don’t need to look this up as often. In order to tcpdump your own docker traffic, you will need to identify the appropriate interface first:
# docker network ls NETWORK ID NAME DRIVER SCOPE 15a300de bridge bridge local 88d8d7d1 nextcloud_default bridge local
From that, we get the network ID. This will be included (at least partly) in the interface name, so we’ll just take the first few characters and grep:
# ip addr | grep 88d8b 9: br-88d8d7d1: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP group default
this gives us the full interface name (ok, basically this is just “br-” followed by the network ID).
We can then just use tcpdump any way we like:
tcpdump -i br-88d8d7d1