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use Error;
use super::Device;
fn xorshift32(state: &mut u32) -> u32 {
let mut x = *state;
x ^= x << 13;
x ^= x >> 17;
x ^= x << 5;
*state = x;
x
}
fn check_rng(state: &mut u32, pct: u8) -> bool {
xorshift32(state) % 100 < pct as u32
}
fn corrupt<T: AsMut<[u8]>>(state: &mut u32, mut buffer: T) {
let mut buffer = buffer.as_mut();
let index = (xorshift32(state) as usize) % buffer.len();
let bit = 1 << (xorshift32(state) % 8) as u8;
buffer[index] ^= bit;
}
const MTU: usize = 1536;
#[derive(Debug, Clone, Copy)]
struct Config {
corrupt_pct: u8,
drop_pct: u8,
reorder_pct: u8
}
#[derive(Debug)]
pub struct FaultInjector<T: Device> {
lower: T,
state: u32,
config: Config
}
impl<T: Device> FaultInjector<T> {
pub fn new(lower: T, seed: u32) -> FaultInjector<T> {
FaultInjector {
lower: lower,
state: seed,
config: Config {
corrupt_pct: 0,
drop_pct: 0,
reorder_pct: 0
}
}
}
pub fn into_lower(self) -> T {
self.lower
}
pub fn corrupt_chance(&self) -> u8 {
self.config.corrupt_pct
}
pub fn drop_chance(&self) -> u8 {
self.config.drop_pct
}
pub fn set_corrupt_chance(&mut self, pct: u8) {
if pct > 100 { panic!("percentage out of range") }
self.config.corrupt_pct = pct
}
pub fn set_drop_chance(&mut self, pct: u8) {
if pct > 100 { panic!("percentage out of range") }
self.config.drop_pct = pct
}
}
impl<T: Device> Device for FaultInjector<T>
where T::RxBuffer: AsMut<[u8]> {
type RxBuffer = T::RxBuffer;
type TxBuffer = TxBuffer<T::TxBuffer>;
fn mtu(&self) -> usize {
if self.lower.mtu() < MTU {
self.lower.mtu()
} else {
MTU
}
}
fn receive(&mut self) -> Result<Self::RxBuffer, Error> {
let mut buffer = try!(self.lower.receive());
if check_rng(&mut self.state, self.config.drop_pct) {
net_trace!("rx: dropping a packet");
return Err(Error::Exhausted)
}
if check_rng(&mut self.state, self.config.corrupt_pct) {
net_trace!("rx: corrupting a packet");
corrupt(&mut self.state, &mut buffer)
}
Ok(buffer)
}
fn transmit(&mut self, length: usize) -> Result<Self::TxBuffer, Error> {
let buffer;
if check_rng(&mut self.state, self.config.drop_pct) {
net_trace!("tx: dropping a packet");
buffer = None;
} else {
buffer = Some(try!(self.lower.transmit(length)));
}
Ok(TxBuffer {
buffer: buffer,
state: xorshift32(&mut self.state),
config: self.config,
junk: [0; MTU],
length: length
})
}
}
#[doc(hidden)]
pub struct TxBuffer<T: AsRef<[u8]> + AsMut<[u8]>> {
state: u32,
config: Config,
buffer: Option<T>,
junk: [u8; MTU],
length: usize
}
impl<T: AsRef<[u8]> + AsMut<[u8]>> AsRef<[u8]>
for TxBuffer<T> {
fn as_ref(&self) -> &[u8] {
match self.buffer {
Some(ref buf) => buf.as_ref(),
None => &self.junk[..self.length]
}
}
}
impl<T: AsRef<[u8]> + AsMut<[u8]>> AsMut<[u8]>
for TxBuffer<T> {
fn as_mut(&mut self) -> &mut [u8] {
match self.buffer {
Some(ref mut buf) => buf.as_mut(),
None => &mut self.junk[..self.length]
}
}
}
impl<T: AsRef<[u8]> + AsMut<[u8]>> Drop for TxBuffer<T> {
fn drop(&mut self) {
match self.buffer {
Some(ref mut buf) => {
if check_rng(&mut self.state, self.config.corrupt_pct) {
net_trace!("tx: corrupting a packet");
corrupt(&mut self.state, buf)
}
},
None => ()
}
}
}