A stricter ipv4 format

[Chardrazle]

The current ipv4 format type allows zero-prefixes in the octets.
When these are consumed by whatever code requires the field they can often go through API functions that treat the zero-prefix octet as an octal value. This can lead to obvious misconfiguration.

Although it's relatively trivial to provide a custom pattern, it would be nice if a stricter ipv4 formatter was available in the specification.

[handrews]

format just defers to other specifications, and dotted-quad is standard for ip4v. Code should understand to parse dotted-quad accordingly and not as octal digits.

[Chardrazle]

Sure, format/ipv4 is following a particular standard. However, because of different API implementations the code is often forced to strip out any leading prefixes from each IPv4 part.
For example, a C implementation may be throwing the input at inet_addr, which would treat leading zeros as octal.
A Python implementation may throw the input at ipaddress, which flatly rejects leading zeros (due to the octal issue).
To avoid any issue, it's often easier to simply reject the leading zeros at the data-input layer.

[handrews]

That's really a regular expression thing. We're not going to specify a format with non-standard behavior, it's just too likely to cause problems.

Of course, you can also make your own extension vocabulary with keywords that do what you want (technically you can make your own format values, too, but the support for that is pretty inconsistent)