domain/base/opt/nsid.rs
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//! ENDS option to provide a Name Server Identifer.
//!
//! The option in this module – [`Nsid<Octs>`] – allows a resolver to query
//! for and a server to provide an identifier for the particular server that
//! answered the query. This can be helpful when debugging a scenario where
//! multiple servers serve a common address.
//!
//! The option is defined in [RFC 5001](https://tools.ietf.org/html/rfc5001).
use super::super::iana::OptionCode;
use super::super::message_builder::OptBuilder;
use super::super::wire::{Composer, ParseError};
use super::{
BuildDataError, LongOptData, Opt, OptData, ComposeOptData, ParseOptData
};
use octseq::builder::OctetsBuilder;
use octseq::octets::{Octets, OctetsFrom};
use octseq::parse::Parser;
use core::{borrow, fmt, hash, mem, str};
use core::cmp::Ordering;
//------------ Nsid ---------------------------------------------------------/
/// Option data for the Name Server Identifier (NSID) Option.
///
/// This option allows identifying a particular name server that has answered
/// a query. If a client is interested in this information, it includes an
/// empty NSID option in its query. If the server supports the option, it
/// includes it in its response with byte string identifying the server.
///
/// The option and details about its use are defined in
/// [RFC 5001](https://tools.ietf.org/html/rfc5001).
#[derive(Clone, Copy)]
#[repr(transparent)]
pub struct Nsid<Octs: ?Sized> {
/// The octets of the identifier.
octets: Octs,
}
impl Nsid<()> {
/// The option code for this option.
pub(super) const CODE: OptionCode = OptionCode::NSID;
}
#[cfg(feature = "serde")]
impl<Octs: octseq::serde::SerializeOctets> serde::Serialize for Nsid<Octs> {
fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
where
S: serde::Serializer {
self.octets.serialize_octets(serializer)
}
}
impl<Octs> Nsid<Octs> {
/// Creates a value from the ocets of the name server identifier.
///
/// The function returns an error if `octets` is longer than 65,535
/// octets.
pub fn from_octets(octets: Octs) -> Result<Self, LongOptData>
where Octs: AsRef<[u8]> {
LongOptData::check_len(octets.as_ref().len())?;
Ok(unsafe { Self::from_octets_unchecked(octets) })
}
/// Creates a value from the name server identifier without checking.
///
/// # Safety
///
/// The caller has to make sure that `octets` is no longer than 65,535
/// octets.
pub unsafe fn from_octets_unchecked(octets: Octs) -> Self {
Nsid { octets }
}
/// Parses a value from its wire format.
pub fn parse<'a, Src: Octets<Range<'a> = Octs> + ?Sized>(
parser: &mut Parser<'a, Src>
) -> Result<Self, ParseError> {
let len = parser.remaining();
LongOptData::check_len(len)?;
Ok(unsafe { Self::from_octets_unchecked(
parser.parse_octets(len)?
)})
}
}
impl Nsid<[u8]> {
/// Creates a value for a slice of the name server identifer.
///
/// The function returns an error if `slice` is longer than 65,535
/// octets.
pub fn from_slice(slice: &[u8]) -> Result<&Self, LongOptData> {
LongOptData::check_len(slice.len())?;
Ok(unsafe { Self::from_slice_unchecked(slice) })
}
/// Creates a value for a slice without checking.
///
/// # Safety
///
/// The caller has to make sure that `octets` is no longer than 65,535
/// octets.
#[must_use]
pub unsafe fn from_slice_unchecked(slice: &[u8]) -> &Self {
// SAFETY: Nsid has repr(transparent)
mem::transmute(slice)
}
/// Creates an empty NSID option value.
#[must_use]
pub fn empty() -> &'static Self {
unsafe { Self::from_slice_unchecked(b"") }
}
}
impl<Octs: ?Sized> Nsid<Octs> {
/// Returns a reference to the octets with the server identifier.
pub fn as_octets(&self) -> &Octs {
&self.octets
}
/// Converts the value into the octets with the server identifier.
pub fn into_octets(self) -> Octs
where
Octs: Sized,
{
self.octets
}
/// Returns a slice of the server identifier.
pub fn as_slice(&self) -> &[u8]
where
Octs: AsRef<[u8]>,
{
self.octets.as_ref()
}
/// Returns a value over an octets slice.
pub fn for_slice(&self) -> &Nsid<[u8]>
where
Octs: AsRef<[u8]>
{
unsafe { Nsid::from_slice_unchecked(self.octets.as_ref()) }
}
}
//--- OctetsFrom
impl<Octs, SrcOcts> OctetsFrom<Nsid<SrcOcts>> for Nsid<Octs>
where Octs: OctetsFrom<SrcOcts> {
type Error = Octs::Error;
fn try_octets_from(src: Nsid<SrcOcts>) -> Result<Self, Self::Error> {
Octs::try_octets_from(src.octets).map(|octets| unsafe {
Self::from_octets_unchecked(octets)
})
}
}
//--- AsRef and Borrow
impl<Octs: AsRef<[u8]> + ?Sized> AsRef<[u8]> for Nsid<Octs> {
fn as_ref(&self) -> &[u8] {
self.as_slice()
}
}
impl<Octs: AsRef<[u8]> + ?Sized> borrow::Borrow<[u8]> for Nsid<Octs> {
fn borrow(&self) -> &[u8] {
self.as_slice()
}
}
//--- OptData etc.
impl<Octs: ?Sized> OptData for Nsid<Octs> {
fn code(&self) -> OptionCode {
OptionCode::NSID
}
}
impl<'a, Octs: Octets> ParseOptData<'a, Octs> for Nsid<Octs::Range<'a>> {
fn parse_option(
code: OptionCode,
parser: &mut Parser<'a, Octs>,
) -> Result<Option<Self>, ParseError> {
if code == OptionCode::NSID {
Self::parse(parser).map(Some)
}
else {
Ok(None)
}
}
}
impl<Octs: AsRef<[u8]> + ?Sized> ComposeOptData for Nsid<Octs> {
fn compose_len(&self) -> u16 {
self.octets.as_ref().len().try_into().expect("long option data")
}
fn compose_option<Target: OctetsBuilder + ?Sized>(
&self, target: &mut Target
) -> Result<(), Target::AppendError> {
target.append_slice(self.octets.as_ref())
}
}
//--- Display and Debug
impl<Octs: AsRef<[u8]> + ?Sized> fmt::Display for Nsid<Octs> {
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
// RFC 5001 § 2.4:
// | User interfaces MUST read and write the contents of the NSID
// | option as a sequence of hexadecimal digits, two digits per
// | payload octet.
for v in self.octets.as_ref() {
write!(f, "{:X} ", *v)?;
}
if let Ok(s) = str::from_utf8(self.octets.as_ref()) {
write!(f, "({})", s)?;
}
Ok(())
}
}
impl<Octs: AsRef<[u8]> + ?Sized> fmt::Debug for Nsid<Octs> {
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
write!(f, "Nsid({})", self)
}
}
//--- PartialEq and Eq
impl<Octs, Other> PartialEq<Other> for Nsid<Octs>
where
Octs: AsRef<[u8]> + ?Sized,
Other: AsRef<[u8]> + ?Sized,
{
fn eq(&self, other: &Other) -> bool {
self.as_slice().eq(other.as_ref())
}
}
impl<Octs: AsRef<[u8]> + ?Sized> Eq for Nsid<Octs> { }
//--- PartialOrd and Ord
impl<Octs, Other> PartialOrd<Other> for Nsid<Octs>
where
Octs: AsRef<[u8]> + ?Sized,
Other: AsRef<[u8]> + ?Sized,
{
fn partial_cmp(&self, other: &Other) -> Option<Ordering> {
self.as_slice().partial_cmp(other.as_ref())
}
}
impl<Octs: AsRef<[u8]> + ?Sized> Ord for Nsid<Octs> {
fn cmp(&self, other: &Self) -> Ordering {
self.as_slice().cmp(other.as_slice())
}
}
//--- Hash
impl<Octs: AsRef<[u8]> + ?Sized> hash::Hash for Nsid<Octs> {
fn hash<H: hash::Hasher>(&self, state: &mut H) {
self.as_slice().hash(state)
}
}
//--- Extended Opt and OptBuilder
impl<Octs: Octets> Opt<Octs> {
/// Returns the first NSID option present.
///
/// In a response, the NSID option contains an identifier of the name
/// server that answered the query. In a query, the option is empty and
/// signals a request for inclusion in a response.
pub fn nsid(&self) -> Option<Nsid<Octs::Range<'_>>> {
self.first()
}
}
impl<'a, Target: Composer> OptBuilder<'a, Target> {
/// Appends an NSID option with the given server identifier.
///
/// The NSID option contains an identifier for the name server that
/// processed a query.
///
/// In a request, the option can be included to request the server to
/// include its server identifier. In this case, the data should be
/// empty. You can use [`client_nsid`][Self::client_nsid] to easily
/// append this version of the option.
pub fn nsid(
&mut self, data: &(impl AsRef<[u8]> + ?Sized)
) -> Result<(), BuildDataError> {
Ok(self.push(Nsid::from_slice(data.as_ref())?)?)
}
/// Appends the client version of an NSID option.
///
/// If included by a client, the NSID option requests that the server
/// returns its name server identifier via the NSID option in a response.
/// In this case, the option must be empty. This method creates such an
/// empty NSID option.
pub fn client_nsid(&mut self) -> Result<(), Target::AppendError> {
self.push(Nsid::empty())
}
}
//============ Testing ======================================================
#[cfg(test)]
#[cfg(all(feature = "std", feature = "bytes"))]
mod test {
use super::*;
use super::super::test::test_option_compose_parse;
#[test]
#[allow(clippy::redundant_closure)] // lifetimes ...
fn nsid_compose_parse() {
test_option_compose_parse(
&Nsid::from_octets("foo").unwrap(),
|parser| Nsid::parse(parser)
);
}
}