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Add packet shaping to the fault injector.

v0.7.x
whitequark 2017-05-29 10:53:30 +00:00
parent 73bb4b8593
commit 91ef5c60c3
4 changed files with 178 additions and 42 deletions
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22
README.md
View File

@ -137,6 +137,23 @@ sudo ip link set tap0 up
sudo ip addr add 192.168.69.100/24 dev tap0
```
### Fault injection
In order to demonstrate the response of _smoltcp_ to adverse network conditions, all examples
implement fault injection, available through command-line options:
* The `--drop-chance` option randomly drops packets, with given probability in percents.
* The `--corrupt-chance` option randomly mutates one octet in a packet, with given
probability in percents.
* The `--size-limit` option drops packets larger than specified size.
* The `--tx-rate-limit` and `--rx-rate-limit` options set the amount of tokens for
a token bucket rate limiter, in packets per bucket.
* The `--shaping-interval` option sets the refill interval of a token bucket rate limiter,
in milliseconds.
A good starting value for `--drop-chance` and `--corrupt-chance` is 15%. A good starting
value for `--?x-rate-limit` is 4 and `--shaping-interval` is 50 ms.
### examples/tcpdump.rs
_examples/tcpdump.rs_ is a tiny clone of the _tcpdump_ utility.
@ -175,9 +192,6 @@ It responds to:
The buffers are only 64 bytes long, for convenience of testing resource exhaustion conditions.
Fault injection is available through the `--drop-chance` and `--corrupt-chance` options,
with values in percents. A good starting value is 15%.
### examples/client.rs
_examples/client.rs_ emulates a network host that can initiate requests.
@ -193,8 +207,6 @@ cargo run --example client -- tap0 ADDRESS PORT
It connects to the given address (not a hostname) and port (e.g. `socat stdio tcp4-listen 1234`),
and will respond with reversed chunks of the input indefinitely.
Fault injection is available, as described above.
License
-------

20
examples/utils.rs
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@ -1,6 +1,6 @@
use std::str::{self, FromStr};
use std::env;
use std::time::{Instant, SystemTime, UNIX_EPOCH};
use std::time::{Instant, Duration, SystemTime, UNIX_EPOCH};
use std::process;
use log::{LogLevelFilter, LogRecord};
use env_logger::{LogBuilder};
@ -36,6 +36,12 @@ pub fn setup_device(more_args: &[&str])
let mut opts = getopts::Options::new();
opts.optopt("", "drop-chance", "Chance of dropping a packet (%)", "CHANCE");
opts.optopt("", "corrupt-chance", "Chance of corrupting a packet (%)", "CHANCE");
opts.optopt("", "size-limit", "Drop packets larger than given size (octets)", "SIZE");
opts.optopt("", "tx-rate-limit", "Drop packets after transmit rate exceeds given limit \
(packets per interval)", "RATE");
opts.optopt("", "rx-rate-limit", "Drop packets after transmit rate exceeds given limit \
(packets per interval)", "RATE");
opts.optopt("", "shaping-interval", "Sets the interval for rate limiting (ms)", "RATE");
opts.optflag("h", "help", "print this help menu");
let matches = opts.parse(env::args().skip(1)).unwrap();
@ -50,6 +56,14 @@ pub fn setup_device(more_args: &[&str])
.unwrap_or("0".to_string())).unwrap();
let corrupt_chance = u8::from_str(&matches.opt_str("corrupt-chance")
.unwrap_or("0".to_string())).unwrap();
let size_limit = usize::from_str(&matches.opt_str("size-limit")
.unwrap_or("0".to_string())).unwrap();
let tx_rate_limit = u64::from_str(&matches.opt_str("tx-rate-limit")
.unwrap_or("0".to_string())).unwrap();
let rx_rate_limit = u64::from_str(&matches.opt_str("rx-rate-limit")
.unwrap_or("0".to_string())).unwrap();
let shaping_interval = u32::from_str(&matches.opt_str("shaping-interval")
.unwrap_or("0".to_string())).unwrap();
let seed = SystemTime::now().duration_since(UNIX_EPOCH).unwrap().subsec_nanos();
@ -61,6 +75,10 @@ pub fn setup_device(more_args: &[&str])
let mut device = FaultInjector::new(device, seed);
device.set_drop_chance(drop_chance);
device.set_corrupt_chance(corrupt_chance);
device.set_max_packet_size(size_limit);
device.set_max_tx_rate(tx_rate_limit);
device.set_max_rx_rate(rx_rate_limit);
device.set_bucket_interval(Duration::from_millis(shaping_interval as u64));
let device = Tracer::<_, EthernetFrame<&'static [u8]>>::new(device, trace_writer);
(device, matches.free[1..].to_owned())

177
src/phy/fault_injector.rs
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@ -1,3 +1,5 @@
use std::time::{Instant, Duration};
use Error;
use super::{DeviceLimits, Device};
@ -12,54 +14,102 @@ fn xorshift32(state: &mut u32) -> u32 {
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();
// We introduce a single bitflip, as the most likely, and the hardest to detect, error.
let index = (xorshift32(state) as usize) % buffer.len();
let bit = 1 << (xorshift32(state) % 8) as u8;
buffer[index] ^= bit;
}
// This could be fixed once associated consts are stable.
const MTU: usize = 1536;
#[derive(Debug, Clone, Copy)]
#[derive(Debug, Clone, Copy, Default)]
struct Config {
corrupt_pct: u8,
drop_pct: u8,
reorder_pct: u8
reorder_pct: u8,
max_size: usize,
max_tx_rate: u64,
max_rx_rate: u64,
interval: Duration,
}
#[derive(Debug, Clone, Copy)]
struct State {
rng_seed: u32,
refilled_at: Instant,
tx_bucket: u64,
rx_bucket: u64,
}
impl State {
fn maybe(&mut self, pct: u8) -> bool {
xorshift32(&mut self.rng_seed) % 100 < pct as u32
}
fn corrupt<T: AsMut<[u8]>>(&mut self, mut buffer: T) {
let mut buffer = buffer.as_mut();
// We introduce a single bitflip, as the most likely, and the hardest to detect, error.
let index = (xorshift32(&mut self.rng_seed) as usize) % buffer.len();
let bit = 1 << (xorshift32(&mut self.rng_seed) % 8) as u8;
buffer[index] ^= bit;
}
fn refill(&mut self, config: &Config) {
if self.refilled_at.elapsed() > config.interval {
self.tx_bucket = config.max_tx_rate;
self.rx_bucket = config.max_rx_rate;
self.refilled_at = Instant::now();
}
}
fn maybe_transmit(&mut self, config: &Config) -> bool {
if config.max_tx_rate == 0 { return true }
self.refill(config);
if self.tx_bucket > 0 {
self.tx_bucket -= 1;
true
} else {
false
}
}
fn maybe_receive(&mut self, config: &Config) -> bool {
if config.max_rx_rate == 0 { return true }
self.refill(config);
if self.rx_bucket > 0 {
self.rx_bucket -= 1;
true
} else {
false
}
}
}
/// A fault injector device.
///
/// A fault injector is a device that randomly drops or corrupts packets traversing it,
/// according to preset probabilities.
/// A fault injector is a device that alters packets traversing through it to simulate
/// adverse network conditions (such as random packet loss or corruption), or software
/// or hardware limitations (such as a limited number or size of usable network buffers).
#[derive(Debug)]
pub struct FaultInjector<T: Device> {
lower: T,
state: u32,
state: State,
config: Config
}
impl<T: Device> FaultInjector<T> {
/// Create a tracer device, using the given random number generator seed.
/// Create a fault injector device, using the given random number generator seed.
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
}
state: State {
rng_seed: seed,
refilled_at: Instant::now(),
tx_bucket: 0,
rx_bucket: 0,
},
config: Config::default()
}
}
/// Return the underlying device, consuming the tracer.
/// Return the underlying device, consuming the fault injector.
pub fn into_lower(self) -> T {
self.lower
}
@ -74,6 +124,26 @@ impl<T: Device> FaultInjector<T> {
self.config.drop_pct
}
/// Return the maximum packet size, in octets.
pub fn max_packet_size(&self) -> usize {
self.config.max_size
}
/// Return the maximum packet transmission rate, in packets per second.
pub fn max_tx_rate(&self) -> u64 {
self.config.max_rx_rate
}
/// Return the maximum packet reception rate, in packets per second.
pub fn max_rx_rate(&self) -> u64 {
self.config.max_tx_rate
}
/// Return the interval for packet rate limiting, in milliseconds.
pub fn bucket_interval(&self) -> Duration {
self.config.interval
}
/// Set the probability of corrupting a packet, in percents.
///
/// # Panics
@ -91,6 +161,27 @@ impl<T: Device> FaultInjector<T> {
if pct > 100 { panic!("percentage out of range") }
self.config.drop_pct = pct
}
/// Set the maximum packet size, in octets.
pub fn set_max_packet_size(&mut self, size: usize) {
self.config.max_size = size
}
/// Set the maximum packet transmission rate, in packets per interval.
pub fn set_max_tx_rate(&mut self, rate: u64) {
self.config.max_tx_rate = rate
}
/// Set the maximum packet reception rate, in packets per interval.
pub fn set_max_rx_rate(&mut self, rate: u64) {
self.config.max_rx_rate = rate
}
/// Set the interval for packet rate limiting, in milliseconds.
pub fn set_bucket_interval(&mut self, interval: Duration) {
self.state.refilled_at = Instant::now() - self.config.interval;
self.config.interval = interval
}
}
impl<T: Device> Device for FaultInjector<T>
@ -108,28 +199,42 @@ impl<T: Device> Device for FaultInjector<T>
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");
if self.state.maybe(self.config.drop_pct) {
net_trace!("rx: randomly 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)
if self.state.maybe(self.config.corrupt_pct) {
net_trace!("rx: randomly corrupting a packet");
self.state.corrupt(&mut buffer)
}
if self.config.max_size > 0 && buffer.as_ref().len() > self.config.max_size {
net_trace!("rx: dropping a packet that is too large");
return Err(Error::Exhausted)
}
if !self.state.maybe_receive(&self.config) {
net_trace!("rx: dropping a packet because of rate limiting");
return Err(Error::Exhausted)
}
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");
if self.state.maybe(self.config.drop_pct) {
net_trace!("tx: randomly dropping a packet");
buffer = None;
} else if self.config.max_size > 0 && length > self.config.max_size {
net_trace!("tx: dropping a packet that is too large");
buffer = None;
} else if !self.state.maybe_transmit(&self.config) {
net_trace!("tx: dropping a packet because of rate limiting");
buffer = None;
} else {
buffer = Some(try!(self.lower.transmit(length)));
}
Ok(TxBuffer {
buffer: buffer,
state: xorshift32(&mut self.state),
state: self.state.clone(),
config: self.config,
junk: [0; MTU],
length: length
@ -139,7 +244,7 @@ impl<T: Device> Device for FaultInjector<T>
#[doc(hidden)]
pub struct TxBuffer<T: AsRef<[u8]> + AsMut<[u8]>> {
state: u32,
state: State,
config: Config,
buffer: Option<T>,
junk: [u8; MTU],
@ -170,9 +275,9 @@ 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) {
if self.state.maybe(self.config.corrupt_pct) {
net_trace!("tx: corrupting a packet");
corrupt(&mut self.state, buf)
self.state.corrupt(buf)
}
},
None => ()

1
src/socket/tcp.rs
View File

@ -717,6 +717,7 @@ impl<'a> TcpSocket<'a> {
(_, TcpRepr { seq_number, .. }) => {
let next_remote_seq = self.remote_seq_no + self.rx_buffer.len();
if seq_number > next_remote_seq {
self.retransmit.reset();
net_trace!("[{}]{}:{}: unacceptable SEQ ({} not in {}..)",
self.debug_id, self.local_endpoint, self.remote_endpoint,
seq_number, next_remote_seq);