Function parse_path_validation 

pub fn parse_path_validation(
    packet: &PhantomPacket,
) -> Result<Option<ParsedPathValidation>, PathValidationParseError>

Available on crate feature std only.

Attempt to parse a PhantomPacket as a PATH_VALIDATION frame.

Returns:

• Ok(Some(...)) when the packet is a well-formed PATH_VALIDATION (correct flag + correct payload length).
• Ok(None) when the packet is a valid frame but NOT a PATH_VALIDATION frame — the caller routes it normally.
• Err(...) when the PATH_VALIDATION flag is set but the payload length is wrong.