gh-128319: Add missing server class attributes to socketserver docs

[stephen-hansen]

Just doing some cleanup of the socketserver docs regarding class attributes as mentioned in the linked issue.

• Move address_family attribute from instance attributes to class attributes.
• Document allow_reuse_port.
• Document max_packet_size (note UDP only).
• Add note to request_queue_size to denote TCP only.

• Issue: Some server class attributes are missing in socketserver docs #128319

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📚 Documentation preview 📚: https://cpython-previews--128320.org.readthedocs.build/

[ZeroIntensity]

Thanks for doing this :)

[reactive-firewall]

👍🏻 LGTM! With conditions (see knit-picky inline comment)

🙇 Thanks @stephen-hansen; These document drafts have already been useful to me.

[reactive-firewall]

LGTM! With conditions:

Please consider clarifying if the term "data" here, means without IP/UDP headers with something like:

Suggested change

	The maximum amount of data (in bytes) to receive at once. If a packet is
	too large for the buffer, then the excess bytes beyond :attr:`max_packet_size`
	are discarded. The default value is usually ``8192``, but this can be
	overridden by subclasses.
	The maximum amount of data (in bytes) to receive at once. If a packet's
	payload (excluding headers) is too large for the buffer, then the excess
	bytes beyond :attr:`max_packet_size` are discarded. The default value
	is usually ``8192``, but this can be overridden by subclasses.

or if this really is the literal maximum packet size:

Suggested change

	The maximum amount of data (in bytes) to receive at once. If a packet is
	too large for the buffer, then the excess bytes beyond :attr:`max_packet_size`
	are discarded. The default value is usually ``8192``, but this can be
	overridden by subclasses.
	The maximum amount of data (in bytes) to receive at once. If a packet's
	payload (including headers) is too large for the buffer, then the excess
	bytes beyond :attr:`max_packet_size` are discarded. The default value
	is usually ``8192``, but this can be overridden by subclasses.

Rational:
Omission of any mention of header when talking about a "packet" being "too large" is somewhat misleading to the reader.
not sure if going further is relevant to the python side, but for convenience sake I'll mention, the typical 20-byte IPV4 header (RFC-791 gives 20-byte base header, 40-byte maximum options) and the required 8-byte header assuming UDP (RFC-768).

Hopefully this helps.

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Additional considerations (TL;DR):

• MTU, and fragmentation boundaries are possible reasons to want to change the default (eg. expected max burst count * max packet size (including headers) on network path with values of 5 * (1500 - 20 - 40 - 8) = 7160 so the default is somewhat larger than the similar stream sockets' request_queue_size default)
• UDP max packet size (after headers) is a possible (albeit unlikely) reason for increasing the size well beyond the default of 8192