Net functions behave slightly different for IPv4 from IPv6. Why?

Question

I'm using BigQuery to truncate IPv4 & IP46 IP addresses. By that I mean I want to drop the part that might be used to identify a real person.

Here's some demo code:

select *,
        NET.IP_TO_STRING(NET.IP_TRUNC(NET.IP_FROM_STRING(v.IPv4Address), 24)),
        NET.IP_TO_STRING(NET.IP_TRUNC(NET.IP_FROM_STRING(v.IPv6Address), 64))
from (
  select struct(
     "254.34.78.20" as `IPV4Address`,
     "2a02:c7e:3f0d:e00:48e:abff:d697:9cc2" as `IPv6Address`
  ) as v
)

It returns:

v	f0_	f1_
{ "IPV4Address": "254.34.78.20", "IPv6Address": "2a02:c7e:3f0d:e00:48e:abff:d697:9cc2" }	254.34.78.0	2a02:c7e:3f0d:e00::

I'd simply like to know why these functions return a 0 for the truncated portion of the IPv4 address but nothing for the truncated portion of the IPv6 address.

I know this isn't really a BigQuery question per se as its more about networks and I suspect BigQuery is just doing what any other such library would do... but interested to know why this is nonetheless. Maybe I'll tag it with IPv6 too

Answer 1

A container image build in docker is designed to be self contained and portable. It shouldn't matter whether you run the build on your host or a CI server in the cloud. To do that, they rely on the build context and args to the build command, rather than other settings on the host, where possible.

buildah seems to have taken a different approach with their tooling, allowing you to use components from the host in your build, giving you more flexibility, but also fragility.

That's a long way of saying the "feature" doesn't exist in docker, and if it gets created, I doubt it would look like what you're describing. Instead, with buildkit, they allow you to inject secrets from the build command line, which are mounted into the steps where they are required. An example of this is available in the buildkit docs:

# syntax = docker/dockerfile:1.3
FROM python:3
RUN pip install awscli
RUN --mount=type=secret,id=aws,target=/root/.aws/credentials aws s3 cp s3://... ...

And to build that Dockerfile, you would pass the secret as a CLI arg:

$ docker build --secret id=aws,src=$HOME/.aws/credentials .