net_backend/
loopback.rs

1// Copyright (c) Microsoft Corporation.
2// Licensed under the MIT License.
3
4//! Loopback endpoint implementation, which reflects all transmits back as
5//! receives.
6//!
7//! This is useful for testing.
8
9use crate::BufferAccess;
10use crate::Endpoint;
11use crate::MultiQueueSupport;
12use crate::Queue;
13use crate::QueueConfig;
14use crate::RssConfig;
15use crate::RxId;
16use crate::RxMetadata;
17use crate::TxError;
18use crate::TxId;
19use crate::TxSegment;
20use crate::linearize;
21use crate::packet_count;
22use async_trait::async_trait;
23use inspect::InspectMut;
24use std::collections::VecDeque;
25use std::task::Context;
26use std::task::Poll;
27
28/// A networking backend that reflects all transmitted packets back as received
29/// packets.
30#[derive(InspectMut)]
31#[inspect(skip)]
32pub struct LoopbackEndpoint(());
33
34impl LoopbackEndpoint {
35    /// Returns a new endpoint.
36    pub fn new() -> Self {
37        Self(())
38    }
39}
40
41#[async_trait]
42impl Endpoint for LoopbackEndpoint {
43    fn endpoint_type(&self) -> &'static str {
44        "loopback"
45    }
46
47    async fn get_queues(
48        &mut self,
49        config: Vec<QueueConfig<'_>>,
50        _rss: Option<&RssConfig<'_>>,
51        queues: &mut Vec<Box<dyn Queue>>,
52    ) -> anyhow::Result<()> {
53        queues.extend(config.into_iter().map(|config| {
54            Box::new(LoopbackQueue {
55                pool: config.pool,
56                rx_avail: config.initial_rx.to_vec().into(),
57                rx_done: VecDeque::new(),
58            }) as _
59        }));
60        Ok(())
61    }
62
63    async fn stop(&mut self) {}
64
65    fn is_ordered(&self) -> bool {
66        true
67    }
68
69    fn multiqueue_support(&self) -> MultiQueueSupport {
70        MultiQueueSupport {
71            max_queues: u16::MAX,
72            indirection_table_size: 64,
73        }
74    }
75}
76
77#[derive(InspectMut)]
78#[inspect(skip)]
79pub struct LoopbackQueue {
80    pub(crate) pool: Box<dyn BufferAccess>,
81    pub(crate) rx_avail: VecDeque<RxId>,
82    pub(crate) rx_done: VecDeque<RxId>,
83}
84
85impl Queue for LoopbackQueue {
86    fn poll_ready(&mut self, _cx: &mut Context<'_>) -> Poll<()> {
87        if self.rx_done.is_empty() {
88            Poll::Pending
89        } else {
90            Poll::Ready(())
91        }
92    }
93
94    fn rx_avail(&mut self, done: &[RxId]) {
95        tracing::debug!(count = done.len(), "rx_avail");
96        self.rx_avail.extend(done);
97    }
98
99    fn rx_poll(&mut self, packets: &mut [RxId]) -> anyhow::Result<usize> {
100        let n = packets.len().min(self.rx_done.len());
101        for (d, s) in packets.iter_mut().zip(self.rx_done.drain(..n)) {
102            *d = s;
103        }
104        Ok(n)
105    }
106
107    fn tx_avail(&mut self, mut segments: &[TxSegment]) -> anyhow::Result<(bool, usize)> {
108        tracing::debug!(count = packet_count(segments), "tx_avail");
109        let mut sent = 0;
110        while !segments.is_empty() && !self.rx_avail.is_empty() {
111            let before = segments.len();
112            let packet = linearize(self.pool.as_ref(), &mut segments)?;
113            sent += before - segments.len();
114            let rx_id = self.rx_avail.pop_front().unwrap();
115            self.pool.write_packet(
116                rx_id,
117                &RxMetadata {
118                    offset: 0,
119                    len: packet.len(),
120                    ..Default::default()
121                },
122                &packet,
123            );
124            self.rx_done.push_back(rx_id);
125        }
126        Ok((true, sent))
127    }
128
129    fn tx_poll(&mut self, _done: &mut [TxId]) -> Result<usize, TxError> {
130        Ok(0)
131    }
132
133    fn buffer_access(&mut self) -> Option<&mut dyn BufferAccess> {
134        Some(self.pool.as_mut())
135    }
136}
net_backend/loopback.rs

net_backend/
loopback.rs
