311 lines
9.4 KiB
Rust
311 lines
9.4 KiB
Rust
use core::cell::RefCell;
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use crate::{Error, Result};
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use crate::phy::{self, DeviceCapabilities, Device};
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use crate::time::{Duration, Instant};
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// We use our own RNG to stay compatible with #![no_std].
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// The use of the RNG below has a slight bias, but it doesn't matter.
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fn xorshift32(state: &mut u32) -> u32 {
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let mut x = *state;
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x ^= x << 13;
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x ^= x >> 17;
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x ^= x << 5;
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*state = x;
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x
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}
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// This could be fixed once associated consts are stable.
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const MTU: usize = 1536;
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#[derive(Debug, Default, Clone, Copy)]
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struct Config {
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corrupt_pct: u8,
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drop_pct: u8,
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reorder_pct: u8,
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max_size: usize,
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max_tx_rate: u64,
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max_rx_rate: u64,
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interval: Duration,
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}
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#[derive(Debug, Clone)]
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struct State {
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rng_seed: u32,
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refilled_at: Instant,
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tx_bucket: u64,
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rx_bucket: u64,
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}
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impl State {
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fn maybe(&mut self, pct: u8) -> bool {
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xorshift32(&mut self.rng_seed) % 100 < pct as u32
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}
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fn corrupt<T: AsMut<[u8]>>(&mut self, mut buffer: T) {
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let buffer = buffer.as_mut();
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// We introduce a single bitflip, as the most likely, and the hardest to detect, error.
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let index = (xorshift32(&mut self.rng_seed) as usize) % buffer.len();
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let bit = 1 << (xorshift32(&mut self.rng_seed) % 8) as u8;
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buffer[index] ^= bit;
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}
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fn refill(&mut self, config: &Config, timestamp: Instant) {
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if timestamp - self.refilled_at > config.interval {
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self.tx_bucket = config.max_tx_rate;
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self.rx_bucket = config.max_rx_rate;
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self.refilled_at = timestamp;
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}
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}
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fn maybe_transmit(&mut self, config: &Config, timestamp: Instant) -> bool {
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if config.max_tx_rate == 0 { return true }
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self.refill(config, timestamp);
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if self.tx_bucket > 0 {
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self.tx_bucket -= 1;
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true
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} else {
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false
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}
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}
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fn maybe_receive(&mut self, config: &Config, timestamp: Instant) -> bool {
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if config.max_rx_rate == 0 { return true }
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self.refill(config, timestamp);
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if self.rx_bucket > 0 {
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self.rx_bucket -= 1;
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true
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} else {
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false
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}
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}
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}
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/// A fault injector device.
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///
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/// A fault injector is a device that alters packets traversing through it to simulate
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/// adverse network conditions (such as random packet loss or corruption), or software
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/// or hardware limitations (such as a limited number or size of usable network buffers).
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#[derive(Debug)]
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pub struct FaultInjector<D: for<'a> Device<'a>> {
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inner: D,
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state: RefCell<State>,
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config: Config,
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}
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impl<D: for<'a> Device<'a>> FaultInjector<D> {
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/// Create a fault injector device, using the given random number generator seed.
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pub fn new(inner: D, seed: u32) -> FaultInjector<D> {
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let state = State {
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rng_seed: seed,
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refilled_at: Instant::from_millis(0),
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tx_bucket: 0,
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rx_bucket: 0,
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};
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FaultInjector {
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inner: inner,
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state: RefCell::new(state),
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config: Config::default(),
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}
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}
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/// Return the underlying device, consuming the fault injector.
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pub fn into_inner(self) -> D {
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self.inner
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}
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/// Return the probability of corrupting a packet, in percents.
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pub fn corrupt_chance(&self) -> u8 {
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self.config.corrupt_pct
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}
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/// Return the probability of dropping a packet, in percents.
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pub fn drop_chance(&self) -> u8 {
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self.config.drop_pct
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}
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/// Return the maximum packet size, in octets.
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pub fn max_packet_size(&self) -> usize {
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self.config.max_size
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}
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/// Return the maximum packet transmission rate, in packets per second.
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pub fn max_tx_rate(&self) -> u64 {
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self.config.max_rx_rate
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}
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/// Return the maximum packet reception rate, in packets per second.
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pub fn max_rx_rate(&self) -> u64 {
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self.config.max_tx_rate
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}
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/// Return the interval for packet rate limiting, in milliseconds.
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pub fn bucket_interval(&self) -> Duration {
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self.config.interval
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}
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/// Set the probability of corrupting a packet, in percents.
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///
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/// # Panics
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/// This function panics if the probability is not between 0% and 100%.
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pub fn set_corrupt_chance(&mut self, pct: u8) {
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if pct > 100 { panic!("percentage out of range") }
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self.config.corrupt_pct = pct
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}
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/// Set the probability of dropping a packet, in percents.
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///
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/// # Panics
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/// This function panics if the probability is not between 0% and 100%.
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pub fn set_drop_chance(&mut self, pct: u8) {
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if pct > 100 { panic!("percentage out of range") }
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self.config.drop_pct = pct
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}
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/// Set the maximum packet size, in octets.
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pub fn set_max_packet_size(&mut self, size: usize) {
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self.config.max_size = size
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}
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/// Set the maximum packet transmission rate, in packets per interval.
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pub fn set_max_tx_rate(&mut self, rate: u64) {
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self.config.max_tx_rate = rate
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}
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/// Set the maximum packet reception rate, in packets per interval.
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pub fn set_max_rx_rate(&mut self, rate: u64) {
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self.config.max_rx_rate = rate
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}
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/// Set the interval for packet rate limiting, in milliseconds.
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pub fn set_bucket_interval(&mut self, interval: Duration) {
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self.state.borrow_mut().refilled_at = Instant::from_millis(0);
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self.config.interval = interval
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}
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}
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impl<'a, D> Device<'a> for FaultInjector<D>
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where D: for<'b> Device<'b>,
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{
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type RxToken = RxToken<'a, <D as Device<'a>>::RxToken>;
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type TxToken = TxToken<'a, <D as Device<'a>>::TxToken>;
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fn capabilities(&self) -> DeviceCapabilities {
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let mut caps = self.inner.capabilities();
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if caps.max_transmission_unit > MTU {
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caps.max_transmission_unit = MTU;
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}
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caps
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}
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fn receive(&'a mut self) -> Option<(Self::RxToken, Self::TxToken)> {
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let &mut Self { ref mut inner, ref state, config } = self;
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inner.receive().map(|(rx_token, tx_token)| {
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let rx = RxToken {
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state: &state,
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config: config,
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token: rx_token,
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corrupt: [0; MTU],
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};
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let tx = TxToken {
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state: &state,
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config: config,
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token: tx_token,
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junk: [0; MTU],
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};
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(rx, tx)
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})
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}
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fn transmit(&'a mut self) -> Option<Self::TxToken> {
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let &mut Self { ref mut inner, ref state, config } = self;
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inner.transmit().map(|token| TxToken {
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state: &state,
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config: config,
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token: token,
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junk: [0; MTU],
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})
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}
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}
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#[doc(hidden)]
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pub struct RxToken<'a, Rx: phy::RxToken> {
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state: &'a RefCell<State>,
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config: Config,
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token: Rx,
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corrupt: [u8; MTU],
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}
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impl<'a, Rx: phy::RxToken> phy::RxToken for RxToken<'a, Rx> {
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fn consume<R, F>(self, timestamp: Instant, f: F) -> Result<R>
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where F: FnOnce(&mut [u8]) -> Result<R>
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{
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if self.state.borrow_mut().maybe(self.config.drop_pct) {
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net_trace!("rx: randomly dropping a packet");
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return Err(Error::Exhausted)
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}
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if !self.state.borrow_mut().maybe_receive(&self.config, timestamp) {
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net_trace!("rx: dropping a packet because of rate limiting");
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return Err(Error::Exhausted)
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}
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let Self { token, config, state, mut corrupt } = self;
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token.consume(timestamp, |buffer| {
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if config.max_size > 0 && buffer.as_ref().len() > config.max_size {
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net_trace!("rx: dropping a packet that is too large");
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return Err(Error::Exhausted)
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}
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if state.borrow_mut().maybe(config.corrupt_pct) {
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net_trace!("rx: randomly corrupting a packet");
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let mut corrupt = &mut corrupt[..buffer.len()];
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corrupt.copy_from_slice(buffer);
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state.borrow_mut().corrupt(&mut corrupt);
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f(&mut corrupt)
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} else {
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f(buffer)
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}
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})
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}
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}
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#[doc(hidden)]
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pub struct TxToken<'a, Tx: phy::TxToken> {
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state: &'a RefCell<State>,
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config: Config,
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token: Tx,
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junk: [u8; MTU],
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}
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impl<'a, Tx: phy::TxToken> phy::TxToken for TxToken<'a, Tx> {
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fn consume<R, F>(mut self, timestamp: Instant, len: usize, f: F) -> Result<R>
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where F: FnOnce(&mut [u8]) -> Result<R>
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{
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let drop = if self.state.borrow_mut().maybe(self.config.drop_pct) {
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net_trace!("tx: randomly dropping a packet");
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true
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} else if self.config.max_size > 0 && len > self.config.max_size {
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net_trace!("tx: dropping a packet that is too large");
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true
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} else if !self.state.borrow_mut().maybe_transmit(&self.config, timestamp) {
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net_trace!("tx: dropping a packet because of rate limiting");
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true
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} else {
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false
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};
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if drop {
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return f(&mut self.junk);
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}
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let Self { token, state, config, .. } = self;
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token.consume(timestamp, len, |mut buf| {
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if state.borrow_mut().maybe(config.corrupt_pct) {
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net_trace!("tx: corrupting a packet");
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state.borrow_mut().corrupt(&mut buf)
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}
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f(buf)
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})
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}
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}
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