Struct Header

pub struct Header { /* private fields */ }

The first part of the header of a DNS message.

This type represents the information contained in the first four octets of the header: the message ID, opcode, rcode, and the various flags. It keeps those four octets in wire representation, i.e., in network byte order. The data is layed out like this:

                                1  1  1  1  1  1
  0  1  2  3  4  5  6  7  8  9  0  1  2  3  4  5
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
|                      ID                       |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
|QR|   Opcode  |AA|TC|RD|RA|Z |AD|CD|   RCODE   |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+

Methods are available for accessing each of these fields. For more information on the fields, see these methods in the section Field Access below.

You can create owned values via the new method or the Default trait. However, more often the type will be used via a reference into the octets of an actual message. The functions for_message_slice and for_message_slice_mut create such references from an octets slice.

The basic structure and most of the fields re defined in RFC 1035, except for the AD and CD flags, which are defined in RFC 4035.

Implementations

impl Header

Creation and Conversion

pub fn new() -> Self

Creates a new header.

The new header has all fields as either zero or false. Thus, the opcode will be Opcode::QUERY and the response code will be Rcode::NOERROR.

pub fn for_message_slice(s: &[u8]) -> &Header

Creates a header reference from an octets slice of a message.

Panics

This function panics if the slice is less than four octets long.

pub fn for_message_slice_mut(s: &mut [u8]) -> &mut Header

Creates a mutable header reference from an octets slice of a message.

Panics

This function panics if the slice is less than four octets long.

pub fn as_slice(&self) -> &[u8]

Returns a reference to the underlying octets slice.

impl Header

Field Access

pub fn id(self) -> u16

Returns the value of the ID field.

The ID field is an identifier chosen by whoever created a query and is copied into a response by a server. It allows matching incoming responses to their queries.

When choosing an ID for an outgoing message, make sure it is random to avoid spoofing by guessing the message ID. If std support is enabled, the method set_random_id can be used for this purpose.

pub fn set_id(&mut self, value: u16)

Sets the value of the ID field.

pub fn set_random_id(&mut self)

Sets the value of the ID field to a randomly chosen number.

pub fn qr(self) -> bool

Returns whether the QR bit is set.

pub fn set_qr(&mut self, set: bool)

Sets the value of the QR bit.

pub fn opcode(self) -> Opcode

Returns the value of the Opcode field.

This field specifies the kind of query a message contains. See the Opcode type for more information on the possible values and their meaning. Normal queries have the variant Opcode::QUERY which is also the default value when creating a new header.

pub fn set_opcode(&mut self, opcode: Opcode)

Sets the value of the opcode field.

pub fn flags(self) -> Flags

Returns all flags contained in the header.

This is a virtual field composed of all the flag bits that are present in the header. The returned Flags type can be useful when you’re working with all flags, rather than a single one, which can be easily obtained from the header directly.

pub fn set_flags(&mut self, flags: Flags)

Sets all flag bits.

pub fn aa(self) -> bool

Returns whether the AA bit is set.

pub fn set_aa(&mut self, set: bool)

Sets the value of the AA bit.

pub fn tc(self) -> bool

Returns whether the TC bit is set.

pub fn set_tc(&mut self, set: bool)

Sets the value of the TC bit.

pub fn rd(self) -> bool

Returns whether the RD bit is set.

pub fn set_rd(&mut self, set: bool)

Sets the value of the RD bit.

pub fn ra(self) -> bool

Returns whether the RA bit is set.

pub fn set_ra(&mut self, set: bool)

Sets the value of the RA bit.

pub fn z(self) -> bool

Returns whether the reserved bit is set.

This bit must be false in all queries and responses.

pub fn set_z(&mut self, set: bool)

Sets the value of the reserved bit.

pub fn ad(self) -> bool

Returns whether the AD bit is set.

pub fn set_ad(&mut self, set: bool)

Sets the value of the AD bit.

pub fn cd(self) -> bool

Returns whether the CD bit is set.

pub fn set_cd(&mut self, set: bool)

Sets the value of the CD bit.

pub fn rcode(self) -> Rcode

Returns the value of the RCODE field.

The response code is used in a response to indicate what happened when processing the query. See the Rcode type for information on possible values and their meaning.

pub fn set_rcode(&mut self, rcode: Rcode)

Sets the value of the RCODE field.

Trait Implementations

impl AsMut<Header> for HeaderSection

fn as_mut(&mut self) -> &mut Header

Converts this type into a mutable reference of the (usually inferred) input type.

impl AsRef<Header> for HeaderSection

fn as_ref(&self) -> &Header

Converts this type into a shared reference of the (usually inferred) input type.

impl Clone for Header

fn clone(&self) -> Header

Returns a copy of the value.

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

Performs copy-assignment from source.

impl Debug for Header

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

Formats the value using the given formatter.

impl Default for Header

fn default() -> Header

Returns the “default value” for a type.

impl PartialEq for Header

fn eq(&self, other: &Header) -> 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 Copy for Header

impl Eq for Header

impl StructuralPartialEq for Header