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|
use byteorder::{BigEndian, ByteOrder};
use {Error, ResponseCode, Opcode};
mod flag {
pub const QUERY: u16 = 0b1000_0000_0000_0000;
pub const OPCODE_MASK: u16 = 0b0111_1000_0000_0000;
pub const AUTHORITATIVE: u16 = 0b0000_0100_0000_0000;
pub const TRUNCATED: u16 = 0b0000_0010_0000_0000;
pub const RECURSION_DESIRED: u16 = 0b0000_0001_0000_0000;
pub const RECURSION_AVAILABLE: u16 = 0b0000_0000_1000_0000;
pub const AUTHENTICATED_DATA: u16 = 0b0000_0000_0010_0000;
pub const CHECKING_DISABLED: u16 = 0b0000_0000_0001_0000;
pub const RESERVED_MASK: u16 = 0b0000_0000_0100_0000;
pub const RESPONSE_CODE_MASK: u16 = 0b0000_0000_0000_1111;
}
/// Represents parsed header of the packet
#[derive(Debug, PartialEq, Eq, Clone, Copy)]
#[allow(missing_docs)] // fields are from the spec I think
pub struct Header {
pub id: u16,
pub query: bool,
pub opcode: Opcode,
pub authoritative: bool,
pub truncated: bool,
pub recursion_desired: bool,
pub recursion_available: bool,
pub authenticated_data: bool,
pub checking_disabled: bool,
pub response_code: ResponseCode,
pub questions: u16,
pub answers: u16,
pub nameservers: u16,
pub additional: u16,
}
impl Header {
/// Parse the header into a header structure
pub fn parse(data: &[u8]) -> Result<Header, Error> {
if data.len() < 12 {
return Err(Error::HeaderTooShort);
}
let flags = BigEndian::read_u16(&data[2..4]);
if flags & flag::RESERVED_MASK != 0 {
return Err(Error::ReservedBitsAreNonZero);
}
let header = Header {
id: BigEndian::read_u16(&data[..2]),
query: flags & flag::QUERY == 0,
opcode: ((flags & flag::OPCODE_MASK)
>> flag::OPCODE_MASK.trailing_zeros()).into(),
authoritative: flags & flag::AUTHORITATIVE != 0,
truncated: flags & flag::TRUNCATED != 0,
recursion_desired: flags & flag::RECURSION_DESIRED != 0,
recursion_available: flags & flag::RECURSION_AVAILABLE != 0,
authenticated_data: flags & flag::AUTHENTICATED_DATA != 0,
checking_disabled: flags & flag::CHECKING_DISABLED != 0,
response_code: From::from((flags&flag::RESPONSE_CODE_MASK) as u8),
questions: BigEndian::read_u16(&data[4..6]),
answers: BigEndian::read_u16(&data[6..8]),
nameservers: BigEndian::read_u16(&data[8..10]),
additional: BigEndian::read_u16(&data[10..12]),
};
Ok(header)
}
/// Write a header to a buffer slice
///
/// # Panics
///
/// When buffer size is not exactly 12 bytes
pub fn write(&self, data: &mut [u8]) {
if data.len() != 12 {
panic!("Header size is exactly 12 bytes");
}
let mut flags = 0u16;
flags |= Into::<u16>::into(self.opcode)
<< flag::OPCODE_MASK.trailing_zeros();
flags |= Into::<u8>::into(self.response_code) as u16;
if !self.query { flags |= flag::QUERY; }
if self.authoritative { flags |= flag::AUTHORITATIVE; }
if self.recursion_desired { flags |= flag::RECURSION_DESIRED; }
if self.recursion_available { flags |= flag::RECURSION_AVAILABLE; }
if self.truncated { flags |= flag::TRUNCATED; }
BigEndian::write_u16(&mut data[..2], self.id);
BigEndian::write_u16(&mut data[2..4], flags);
BigEndian::write_u16(&mut data[4..6], self.questions);
BigEndian::write_u16(&mut data[6..8], self.answers);
BigEndian::write_u16(&mut data[8..10], self.nameservers);
BigEndian::write_u16(&mut data[10..12], self.additional);
}
/// Set "truncated flag" in the raw data
// shouldn't this method be non-public?
pub fn set_truncated(data: &mut [u8]) {
let oldflags = BigEndian::read_u16(&data[2..4]);
BigEndian::write_u16(&mut data[2..4], oldflags & flag::TRUNCATED);
}
/// Returns a size of the header (always 12 bytes)
pub fn size() -> usize { 12 }
}
#[cfg(test)]
mod test {
use {Header};
use Opcode::*;
use ResponseCode::NoError;
#[test]
fn parse_example_query() {
let query = b"\x06%\x01\x00\x00\x01\x00\x00\x00\x00\x00\x00\
\x07example\x03com\x00\x00\x01\x00\x01";
let header = Header::parse(query).unwrap();
assert_eq!(header, Header {
id: 1573,
query: true,
opcode: StandardQuery,
authoritative: false,
truncated: false,
recursion_desired: true,
recursion_available: false,
authenticated_data: false,
checking_disabled: false,
response_code: NoError,
questions: 1,
answers: 0,
nameservers: 0,
additional: 0,
});
}
#[test]
fn parse_example_response() {
let response = b"\x06%\x81\x80\x00\x01\x00\x01\x00\x00\x00\x00\
\x07example\x03com\x00\x00\x01\x00\x01\
\xc0\x0c\x00\x01\x00\x01\x00\x00\x04\xf8\
\x00\x04]\xb8\xd8\"";
let header = Header::parse(response).unwrap();
assert_eq!(header, Header {
id: 1573,
query: false,
opcode: StandardQuery,
authoritative: false,
truncated: false,
recursion_desired: true,
recursion_available: true,
authenticated_data: false,
checking_disabled: false,
response_code: NoError,
questions: 1,
answers: 1,
nameservers: 0,
additional: 0,
});
}
#[test]
fn parse_query_with_ad_set() {
let query = b"\x06%\x01\x20\x00\x01\x00\x00\x00\x00\x00\x00\
\x07example\x03com\x00\x00\x01\x00\x01";
let header = Header::parse(query).unwrap();
assert_eq!(header, Header {
id: 1573,
query: true,
opcode: StandardQuery,
authoritative: false,
truncated: false,
recursion_desired: true,
recursion_available: false,
authenticated_data: true,
checking_disabled: false,
response_code: NoError,
questions: 1,
answers: 0,
nameservers: 0,
additional: 0,
});
}
#[test]
fn parse_query_with_cd_set() {
let query = b"\x06%\x01\x10\x00\x01\x00\x00\x00\x00\x00\x00\
\x07example\x03com\x00\x00\x01\x00\x01";
let header = Header::parse(query).unwrap();
assert_eq!(header, Header {
id: 1573,
query: true,
opcode: StandardQuery,
authoritative: false,
truncated: false,
recursion_desired: true,
recursion_available: false,
authenticated_data: false,
checking_disabled: true,
response_code: NoError,
questions: 1,
answers: 0,
nameservers: 0,
additional: 0,
});
}
}
|
