Re:A Docker Abstraction That Handles Container Security
by contingencies on Wednesday July 26, 2017 @09:55AM
(#14856183)
You don't need to rigidly and purely enforce rules only from test results but rather also embedded wisdom, defaults and recommendations.
ICMP is a well known gotcha and the only such protocol in its class.
I've personally never seen a fallback to TCP requirement in the wild but you could easily say "if DNS then enable both protocols" as a general rule, and add <received wisdom>.
These are easy to add as policies and will result in better rules than manually configured systems in many cases, if documented. Everyone's happy.
(re DNS: the DNS protocol uses both TCP and UDP interchangeably, it switches to TCP when the message size crosses a threshold. Many kinds of DNS messages can be over the limit. See eg https://github.com/moby/moby/issues/24344)