docs: Make ICMP rules for the Host Firewall easier to read/search

[qmonnet]

Two trivial improvements to the Host Firewall guide:

• Use the explicit name for the EchoRequest in the example policy (instead of "type: 8"), for better readability.
• Mention "ping" next to ICMP, to make it easier to search for this term in the document.

Fixes: #21986

[qmonnet]

/test

[learnitall]

Great thank you!

[Lenikas]

Hello, @qmonnet

Could you please explain why you changed icmp.fields.type to a string value in the policy example?

According to the official API of CiliumClusterwideNetworkPolicy, the type of this field is integer.

This is confusing when trying to apply this demo policy to the cluster.

Thank you!

[qmonnet]

Hi @Lenikas, thanks for the report. I changed to align this example with what we use elsewhere in some CiliumNetworkPolicy examples, and make it easier to read.

As for the API, my understanding is that since commit 37d969c (merged for v1.16), this field is no longer an integer but an “ICMP-type”, which can be either an integer or the name of an ICMP type. See the relevant version of the API.

Does it answer the question?

[Lenikas]

@qmonnet
Yes, I did not check the api version and the version used in my cluster when I asked

Thanks for the answer!