Struct Metadata 

#[non_exhaustive]
pub struct Metadata {
    pub id: u16,
    pub message_type: MessageType,
    pub op_code: OpCode,
    pub authoritative: bool,
    pub truncation: bool,
    pub recursion_desired: bool,
    pub recursion_available: bool,
    pub authentic_data: bool,
    pub checking_disabled: bool,
    pub response_code: ResponseCode,
}

Message metadata, including the message ID, flags, response code, and op code.

Fields (Non-exhaustive)

Non-exhaustive structs could have additional fields added in future. Therefore, non-exhaustive structs cannot be constructed in external crates using the traditional Struct { .. } syntax; cannot be matched against without a wildcard ..; and struct update syntax will not work.

id: u16

ID              A 16 bit identifier assigned by the program that
                generates any kind of query.  This identifier is copied
                the corresponding reply and can be used by the requester
                to match up replies to outstanding queries.

message_type: MessageType

QR              A one bit field that specifies whether this message is a
                query (0), or a response (1).

op_code: OpCode

OPCODE          A four bit field that specifies kind of query in this
                message.  This value is set by the originator of a query
                and copied into the response.  The values are: <see super::op_code>

authoritative: bool

AA              Authoritative Answer - this bit is valid in responses,
                and specifies that the responding name server is an
                authority for the domain name in question section.

                Note that the contents of the answer section may have
                multiple owner names because of aliases.  The AA bit
                corresponds to the name which matches the query name, or
                the first owner name in the answer section.

truncation: bool

TC              TrunCation - specifies that this message was truncated
                due to length greater than that permitted on the
                transmission channel.

recursion_desired: bool

RD              Recursion Desired - this bit may be set in a query and
                is copied into the response.  If RD is set, it directs
                the name server to pursue the query recursively.
                Recursive query support is optional.

recursion_available: bool

RA              Recursion Available - this be is set or cleared in a
                response, and denotes whether recursive query support is
                available in the name server.

authentic_data: bool

RFC 4035, DNSSEC Resource Records, March 2005

3.1.6.  The AD and CD Bits in an Authoritative Response

  The CD and AD bits are designed for use in communication between
  security-aware resolvers and security-aware recursive name servers.
  These bits are for the most part not relevant to query processing by
  security-aware authoritative name servers.

  A security-aware name server does not perform signature validation
  for authoritative data during query processing, even when the CD bit
  is clear.  A security-aware name server SHOULD clear the CD bit when
  composing an authoritative response.

  A security-aware name server MUST NOT set the AD bit in a response
  unless the name server considers all RRsets in the Answer and
  Authority sections of the response to be authentic.  A security-aware
  name server's local policy MAY consider data from an authoritative
  zone to be authentic without further validation.  However, the name
  server MUST NOT do so unless the name server obtained the
  authoritative zone via secure means (such as a secure zone transfer
  mechanism) and MUST NOT do so unless this behavior has been
  configured explicitly.

  A security-aware name server that supports recursion MUST follow the
  rules for the CD and AD bits given in Section 3.2 when generating a
  response that involves data obtained via recursion.

checking_disabled: bool

See Metadata::authentic_data for more information on the CD bit.

response_code: ResponseCode

RCODE           Response code - this 4 bit field is set as part of
                responses.  The values have the following
                interpretation: <see super::response_code>

Implementations

impl Metadata

pub const fn new(id: u16, message_type: MessageType, op_code: OpCode) -> Self

Construct a new Metadata with the given id, message_type, and op_code.

pub fn response_from_request(req: &Self) -> Self

Construct new metadata based off the request metadata.

This copies over the RD (recursion-desired) and CD (checking-disabled), as well as the op_code and id of the request.

See https://datatracker.ietf.org/doc/html/rfc6895#section-2

The AA, TC, RD, RA, and CD bits are each theoretically meaningful
   only in queries or only in responses, depending on the bit.  The AD
   bit was only meaningful in responses but is expected to have a
   separate but related meaning in queries (see Section 5.7 of
   [RFC6840]).  Only the RD and CD bits are expected to be copied from
   the query to the response; however, some DNS implementations copy all
   the query header as the initial value of the response header.  Thus,
   any attempt to use a "query" bit with a different meaning in a
   response or to define a query meaning for a "response" bit may be
   dangerous, given the existing implementation.  Meanings for these
   bits may only be assigned by a Standards Action.

pub fn flags(&self) -> Flags

A method to get all header flags (useful for Display purposes)

Trait Implementations

impl Clone for Metadata

fn clone(&self) -> Metadata

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for Metadata

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Display for Metadata

fn fmt(&self, f: &mut Formatter<'_>) -> Result<(), Error>

Formats the value using the given formatter.

impl Hash for Metadata

fn hash<__H: Hasher>(&self, state: &mut __H)

Feeds this value into the given Hasher.

fn hash_slice<H>(data: &[Self], state: &mut H)

where H: Hasher, Self: Sized,

Feeds a slice of this type into the given Hasher.

impl PartialEq for Metadata

fn eq(&self, other: &Metadata) -> bool

Tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl PartialOrd for Metadata

fn partial_cmp(&self, other: &Metadata) -> Option<Ordering>

This method returns an ordering between self and other values if one exists.

fn lt(&self, other: &Rhs) -> bool

Tests less than (for self and other) and is used by the < operator.

fn le(&self, other: &Rhs) -> bool

Tests less than or equal to (for self and other) and is used by the <= operator.

fn gt(&self, other: &Rhs) -> bool

Tests greater than (for self and other) and is used by the > operator.

fn ge(&self, other: &Rhs) -> bool

Tests greater than or equal to (for self and other) and is used by the >= operator.

impl Copy for Metadata

impl Eq for Metadata

impl StructuralPartialEq for Metadata