/src/neqo/test-fixture/src/sim/drop.rs
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1 | | // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or |
2 | | // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license |
3 | | // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your |
4 | | // option. This file may not be copied, modified, or distributed |
5 | | // except according to those terms. |
6 | | |
7 | | #![expect(clippy::unwrap_used, reason = "This is test code.")] |
8 | | |
9 | | use std::{ |
10 | | fmt::{self, Debug}, |
11 | | time::Instant, |
12 | | }; |
13 | | |
14 | | use neqo_common::{Datagram, qtrace}; |
15 | | use neqo_transport::Output; |
16 | | |
17 | | use super::{Node, Rng}; |
18 | | |
19 | | /// A random dropper. |
20 | | pub struct Drop { |
21 | | threshold: u64, |
22 | | max: u64, |
23 | | rng: Option<Rng>, |
24 | | } |
25 | | |
26 | | impl Drop { |
27 | | /// Make a new random drop generator. Each `drop` is called, this generates a |
28 | | /// random value between 0 and `max` (exclusive). If this value is less than |
29 | | /// `threshold` a value of `true` is returned. |
30 | | #[must_use] |
31 | 0 | pub const fn new(threshold: u64, max: u64) -> Self { |
32 | 0 | Self { |
33 | 0 | threshold, |
34 | 0 | max, |
35 | 0 | rng: None, |
36 | 0 | } |
37 | 0 | } |
38 | | |
39 | | /// Generate random drops with the given percentage. |
40 | | #[must_use] |
41 | 0 | pub fn percentage(pct: u8) -> Self { |
42 | | // Multiply by 10 so that the random number generator works more efficiently. |
43 | 0 | Self::new(u64::from(pct) * 10, 1000) |
44 | 0 | } |
45 | | |
46 | | /// Determine whether or not to drop a packet. |
47 | | /// # Panics |
48 | | /// When this is invoked after test configuration has been torn down, |
49 | | /// such that the RNG is no longer available. |
50 | | #[must_use] |
51 | 0 | pub fn drop(&self) -> bool { |
52 | 0 | let mut rng = self.rng.as_ref().unwrap().borrow_mut(); |
53 | 0 | let r = rng.random_from(0..self.max); |
54 | 0 | r < self.threshold |
55 | 0 | } |
56 | | } |
57 | | |
58 | | impl Node for Drop { |
59 | 0 | fn init(&mut self, rng: Rng, _now: Instant) { |
60 | 0 | self.rng = Some(rng); |
61 | 0 | } |
62 | | |
63 | | // Pass any datagram provided directly out, but drop some of them. |
64 | 0 | fn process(&mut self, d: Option<Datagram>, _now: Instant) -> Output { |
65 | 0 | d.map_or(Output::None, |dgram| { |
66 | 0 | if self.drop() { |
67 | 0 | qtrace!("drop {}", dgram.len()); |
68 | 0 | Output::None |
69 | | } else { |
70 | 0 | Output::Datagram(dgram) |
71 | | } |
72 | 0 | }) |
73 | 0 | } |
74 | | } |
75 | | |
76 | | impl Debug for Drop { |
77 | 0 | fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result { |
78 | 0 | f.write_str("drop") |
79 | 0 | } |
80 | | } |