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::next_packet;
22use crate::packet_count;
23use async_trait::async_trait;
24use inspect::InspectMut;
25use std::collections::VecDeque;
26use std::task::Context;
27use std::task::Poll;
28
29/// A networking backend that reflects all transmitted packets back as received
30/// packets.
31#[derive(InspectMut)]
32#[inspect(skip)]
33pub struct LoopbackEndpoint(());
34
35impl LoopbackEndpoint {
36    /// Returns a new endpoint.
37    pub fn new() -> Self {
38        Self(())
39    }
40}
41
42#[async_trait]
43impl Endpoint for LoopbackEndpoint {
44    fn endpoint_type(&self) -> &'static str {
45        "loopback"
46    }
47
48    async fn get_queues(
49        &mut self,
50        config: Vec<QueueConfig>,
51        _rss: Option<&RssConfig<'_>>,
52        queues: &mut Vec<Box<dyn Queue>>,
53    ) -> anyhow::Result<()> {
54        queues.extend(config.into_iter().map(|_config| {
55            Box::new(LoopbackQueue {
56                rx_avail: VecDeque::new(),
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) rx_avail: VecDeque<RxId>,
81    pub(crate) rx_done: VecDeque<RxId>,
82}
83
84impl Queue for LoopbackQueue {
85    fn poll_ready(&mut self, _cx: &mut Context<'_>, _pool: &mut dyn BufferAccess) -> Poll<()> {
86        if self.rx_done.is_empty() {
87            Poll::Pending
88        } else {
89            Poll::Ready(())
90        }
91    }
92
93    fn rx_avail(&mut self, _pool: &mut dyn BufferAccess, done: &[RxId]) {
94        tracing::debug!(count = done.len(), "rx_avail");
95        self.rx_avail.extend(done);
96    }
97
98    fn rx_poll(
99        &mut self,
100        _pool: &mut dyn BufferAccess,
101        packets: &mut [RxId],
102    ) -> anyhow::Result<usize> {
103        let n = packets.len().min(self.rx_done.len());
104        for (d, s) in packets.iter_mut().zip(self.rx_done.drain(..n)) {
105            *d = s;
106        }
107        Ok(n)
108    }
109
110    fn tx_avail(
111        &mut self,
112        pool: &mut dyn BufferAccess,
113        mut segments: &[TxSegment],
114    ) -> anyhow::Result<(bool, usize)> {
115        tracing::debug!(count = packet_count(segments), "tx_avail");
116        let mut sent = 0;
117        while !segments.is_empty() && !self.rx_avail.is_empty() {
118            let (meta, _, _) = next_packet(segments);
119            let vlan = meta.vlan;
120            let before = segments.len();
121            let packet = linearize(pool, &mut segments)?;
122            sent += before - segments.len();
123            let rx_id = self.rx_avail.pop_front().unwrap();
124            pool.write_packet(
125                rx_id,
126                &RxMetadata {
127                    offset: 0,
128                    len: packet.len(),
129                    vlan,
130                    ..Default::default()
131                },
132                &packet,
133            );
134            self.rx_done.push_back(rx_id);
135        }
136        Ok((true, sent))
137    }
138
139    fn tx_poll(
140        &mut self,
141        _pool: &mut dyn BufferAccess,
142        _done: &mut [TxId],
143    ) -> Result<usize, TxError> {
144        Ok(0)
145    }
146}
net_backend/loopback.rs

net_backend/
loopback.rs
