udp: remove thingbuf in favor of crossbeam channel

thingbuf didn't have obvious performance advantages and is a lot less
mature. Furthermore, it doesn't support anything like crossbeam
Receiver::try_iter, which is prefereable now that announce responses
can be sent to any socket worker.

CHANGELOG.md

@@ -26,7 +26,6 @@
 * Remove support for unbounded worker channels
 * Add backpressure in socket workers. They will postpone reading from the
   socket if sending a request to a swarm worker failed
-* Reuse allocations in swarm response channel
 * Remove config key `network.poll_event_capacity`
 * Harden ConnectionValidator to make IP spoofing even more costly
 * Distribute announce responses from swarm workers over socket workers to

Cargo.lock

@@ -320,7 +320,6 @@ dependencies = [
  "slab",
  "socket2 0.5.5",
  "tempfile",
- "thingbuf",
  "time",
  "tinytemplate",
 ]
@@ -2079,29 +2078,6 @@ version = "2.2.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "bb813b8af86854136c6922af0598d719255ecb2179515e6e7730d468f05c9cae"
 
-[[package]]
-name = "parking_lot"
-version = "0.12.1"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "3742b2c103b9f06bc9fff0a37ff4912935851bee6d36f3c02bcc755bcfec228f"
-dependencies = [
- "lock_api",
- "parking_lot_core",
-]
-
-[[package]]
-name = "parking_lot_core"
-version = "0.9.9"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "4c42a9226546d68acdd9c0a280d17ce19bfe27a46bf68784e4066115788d008e"
-dependencies = [
- "cfg-if",
- "libc",
- "redox_syscall",
- "smallvec",
- "windows-targets 0.48.5",
-]
-
 [[package]]
 name = "percent-encoding"
 version = "2.3.1"
@@ -2849,16 +2825,6 @@ version = "0.16.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "222a222a5bfe1bba4a77b45ec488a741b3cb8872e5e499451fd7d0129c9c7c3d"
 
-[[package]]
-name = "thingbuf"
-version = "0.1.4"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "4706f1bfb859af03f099ada2de3cea3e515843c2d3e93b7893f16d94a37f9415"
-dependencies = [
- "parking_lot",
- "pin-project",
-]
-
 [[package]]
 name = "thiserror"
 version = "1.0.56"

crates/udp/Cargo.toml

@@ -52,7 +52,6 @@ serde = { version = "1", features = ["derive"] }
 signal-hook = { version = "0.3" }
 slab = "0.4"
 socket2 = { version = "0.5", features = ["all"] }
-thingbuf = "0.1"
 time = { version = "0.3", features = ["formatting"] }
 tinytemplate = "1"
 

crates/udp/src/common.rs

@@ -1,68 +1,19 @@
-use std::borrow::Cow;
 use std::collections::BTreeMap;
 use std::hash::Hash;
-use std::io::Write;
-use std::mem::size_of;
-use std::net::{SocketAddr, SocketAddrV4};
 use std::sync::atomic::AtomicUsize;
 use std::sync::Arc;
 
-use crossbeam_channel::{Sender, TrySendError};
+use crossbeam_channel::{Receiver, SendError, Sender, TrySendError};
 
 use aquatic_common::access_list::AccessListArcSwap;
 use aquatic_common::CanonicalSocketAddr;
 use aquatic_udp_protocol::*;
 use hdrhistogram::Histogram;
-use thingbuf::mpsc::blocking::SendRef;
 
 use crate::config::Config;
 
 pub const BUFFER_SIZE: usize = 8192;
 
-#[derive(PartialEq, Eq, Clone, Debug)]
-pub enum CowResponse<'a> {
-    Connect(Cow<'a, ConnectResponse>),
-    AnnounceIpv4(Cow<'a, AnnounceResponse<Ipv4AddrBytes>>),
-    AnnounceIpv6(Cow<'a, AnnounceResponse<Ipv6AddrBytes>>),
-    Scrape(Cow<'a, ScrapeResponse>),
-    Error(Cow<'a, ErrorResponse>),
-}
-
-impl From<Response> for CowResponse<'_> {
-    fn from(value: Response) -> Self {
-        match value {
-            Response::AnnounceIpv4(r) => Self::AnnounceIpv4(Cow::Owned(r)),
-            Response::AnnounceIpv6(r) => Self::AnnounceIpv6(Cow::Owned(r)),
-            Response::Connect(r) => Self::Connect(Cow::Owned(r)),
-            Response::Scrape(r) => Self::Scrape(Cow::Owned(r)),
-            Response::Error(r) => Self::Error(Cow::Owned(r)),
-        }
-    }
-}
-
-impl<'a> CowResponse<'a> {
-    pub fn into_owned(self) -> Response {
-        match self {
-            CowResponse::Connect(r) => Response::Connect(r.into_owned()),
-            CowResponse::AnnounceIpv4(r) => Response::AnnounceIpv4(r.into_owned()),
-            CowResponse::AnnounceIpv6(r) => Response::AnnounceIpv6(r.into_owned()),
-            CowResponse::Scrape(r) => Response::Scrape(r.into_owned()),
-            CowResponse::Error(r) => Response::Error(r.into_owned()),
-        }
-    }
-
-    #[inline]
-    pub fn write(&self, bytes: &mut impl Write) -> Result<(), ::std::io::Error> {
-        match self {
-            Self::Connect(r) => r.write(bytes),
-            Self::AnnounceIpv4(r) => r.write(bytes),
-            Self::AnnounceIpv6(r) => r.write(bytes),
-            Self::Scrape(r) => r.write(bytes),
-            Self::Error(r) => r.write(bytes),
-        }
-    }
-}
-
 #[derive(Debug)]
 pub struct PendingScrapeRequest {
     pub slab_key: usize,
@@ -88,52 +39,6 @@ pub enum ConnectedResponse {
     Scrape(PendingScrapeResponse),
 }
 
-pub enum ConnectedResponseKind {
-    AnnounceIpv4,
-    AnnounceIpv6,
-    Scrape,
-}
-
-pub struct ConnectedResponseWithAddr {
-    pub kind: ConnectedResponseKind,
-    pub announce_ipv4: AnnounceResponse<Ipv4AddrBytes>,
-    pub announce_ipv6: AnnounceResponse<Ipv6AddrBytes>,
-    pub scrape: PendingScrapeResponse,
-    pub addr: CanonicalSocketAddr,
-}
-
-impl ConnectedResponseWithAddr {
-    pub fn estimated_max_size(config: &Config) -> usize {
-        size_of::<Self>()
-            + config.protocol.max_response_peers
-                * (size_of::<ResponsePeer<Ipv4AddrBytes>>()
-                    + size_of::<ResponsePeer<Ipv6AddrBytes>>())
-    }
-}
-
-pub struct Recycler;
-
-impl thingbuf::Recycle<ConnectedResponseWithAddr> for Recycler {
-    fn new_element(&self) -> ConnectedResponseWithAddr {
-        ConnectedResponseWithAddr {
-            kind: ConnectedResponseKind::AnnounceIpv4,
-            announce_ipv4: AnnounceResponse::empty(),
-            announce_ipv6: AnnounceResponse::empty(),
-            scrape: PendingScrapeResponse {
-                slab_key: 0,
-                torrent_stats: Default::default(),
-            },
-            addr: CanonicalSocketAddr::new(SocketAddr::V4(SocketAddrV4::new(0.into(), 0))),
-        }
-    }
-    fn recycle(&self, element: &mut ConnectedResponseWithAddr) {
-        element.announce_ipv4.peers.clear();
-        element.announce_ipv6.peers.clear();
-        element.scrape.torrent_stats.clear();
-        element.addr = CanonicalSocketAddr::new(SocketAddr::V4(SocketAddrV4::new(0.into(), 0)));
-    }
-}
-
 #[derive(Clone, Copy, Debug)]
 pub struct SocketWorkerIndex(pub usize);
 
@@ -180,54 +85,73 @@ impl ConnectedRequestSender {
 }
 
 pub struct ConnectedResponseSender {
-    senders: Vec<thingbuf::mpsc::blocking::Sender<ConnectedResponseWithAddr, Recycler>>,
+    senders: Vec<Sender<(CanonicalSocketAddr, ConnectedResponse)>>,
     to_any_last_index_picked: usize,
 }
 
 impl ConnectedResponseSender {
-    pub fn new(
-        senders: Vec<thingbuf::mpsc::blocking::Sender<ConnectedResponseWithAddr, Recycler>>,
-    ) -> Self {
+    pub fn new(senders: Vec<Sender<(CanonicalSocketAddr, ConnectedResponse)>>) -> Self {
         Self {
             senders,
             to_any_last_index_picked: 0,
         }
     }
 
-    pub fn try_send_ref_to(
+    pub fn try_send_to(
         &self,
         index: SocketWorkerIndex,
-    ) -> Result<SendRef<ConnectedResponseWithAddr>, thingbuf::mpsc::errors::TrySendError> {
-        self.senders[index.0].try_send_ref()
+        addr: CanonicalSocketAddr,
+        response: ConnectedResponse,
+    ) -> Result<(), TrySendError<(CanonicalSocketAddr, ConnectedResponse)>> {
+        self.senders[index.0].try_send((addr, response))
     }
 
-    pub fn send_ref_to(
+    pub fn send_to(
         &self,
         index: SocketWorkerIndex,
-    ) -> Result<SendRef<ConnectedResponseWithAddr>, thingbuf::mpsc::errors::Closed> {
-        self.senders[index.0].send_ref()
+        addr: CanonicalSocketAddr,
+        response: ConnectedResponse,
+    ) -> Result<(), SendError<(CanonicalSocketAddr, ConnectedResponse)>> {
+        self.senders[index.0].send((addr, response))
     }
 
-    pub fn send_ref_to_any(
+    pub fn send_to_any(
         &mut self,
-    ) -> Result<SendRef<ConnectedResponseWithAddr>, thingbuf::mpsc::errors::Closed> {
+        addr: CanonicalSocketAddr,
+        response: ConnectedResponse,
+    ) -> Result<(), SendError<(CanonicalSocketAddr, ConnectedResponse)>> {
         let start = self.to_any_last_index_picked + 1;
 
-        for i in (start..start + self.senders.len()).map(|i| i % self.senders.len()) {
-            if let Ok(sender) = self.senders[i].try_send_ref() {
-                self.to_any_last_index_picked = i;
+        let mut message = Some((addr, response));
 
-                return Ok(sender);
+        for i in (start..start + self.senders.len()).map(|i| i % self.senders.len()) {
+            match self.senders[i].try_send(message.take().unwrap()) {
+                Ok(()) => {
+                    self.to_any_last_index_picked = i;
+
+                    return Ok(());
+                }
+                Err(TrySendError::Full(msg)) => {
+                    message = Some(msg);
+                }
+                Err(TrySendError::Disconnected(_)) => {
+                    panic!("ConnectedResponseReceiver disconnected");
+                }
             }
         }
 
+        let (addr, response) = message.unwrap();
+
         self.to_any_last_index_picked = start % self.senders.len();
-        self.send_ref_to(SocketWorkerIndex(self.to_any_last_index_picked))
+        self.send_to(
+            SocketWorkerIndex(self.to_any_last_index_picked),
+            addr,
+            response,
+        )
     }
 }
 
-pub type ConnectedResponseReceiver =
-    thingbuf::mpsc::blocking::Receiver<ConnectedResponseWithAddr, Recycler>;
+pub type ConnectedResponseReceiver = Receiver<(CanonicalSocketAddr, ConnectedResponse)>;
 
 #[derive(PartialEq, Eq, Hash, Clone, Copy, Debug)]
 pub enum PeerStatus {

crates/udp/src/lib.rs

@@ -3,7 +3,6 @@ pub mod config;
 pub mod workers;
 
 use std::collections::BTreeMap;
-use std::mem::size_of;
 use std::thread::Builder;
 use std::time::Duration;
 
@@ -16,28 +15,20 @@ use aquatic_common::access_list::update_access_list;
 #[cfg(feature = "cpu-pinning")]
 use aquatic_common::cpu_pinning::{pin_current_if_configured_to, WorkerIndex};
 use aquatic_common::privileges::PrivilegeDropper;
-use aquatic_common::{CanonicalSocketAddr, PanicSentinelWatcher, ServerStartInstant};
+use aquatic_common::{PanicSentinelWatcher, ServerStartInstant};
 
 use common::{
-    ConnectedRequestSender, ConnectedResponseSender, Recycler, SocketWorkerIndex, State,
-    SwarmWorkerIndex,
+    ConnectedRequestSender, ConnectedResponseSender, SocketWorkerIndex, State, SwarmWorkerIndex,
 };
 use config::Config;
 use workers::socket::ConnectionValidator;
 
-use crate::common::{ConnectedRequest, ConnectedResponseWithAddr};
-
 pub const APP_NAME: &str = "aquatic_udp: UDP BitTorrent tracker";
 pub const APP_VERSION: &str = env!("CARGO_PKG_VERSION");
 
 pub fn run(config: Config) -> ::anyhow::Result<()> {
     let mut signals = Signals::new([SIGUSR1, SIGTERM])?;
 
-    ::log::info!(
-        "Estimated max channel memory use: {:.02} MB",
-        est_max_total_channel_memory(&config)
-    );
-
     let state = State::new(config.swarm_workers);
     let connection_validator = ConnectionValidator::new(&config)?;
     let (sentinel_watcher, sentinel) = PanicSentinelWatcher::create_with_sentinel();
@@ -56,19 +47,14 @@ pub fn run(config: Config) -> ::anyhow::Result<()> {
     let server_start_instant = ServerStartInstant::new();
 
     for i in 0..config.swarm_workers {
-        let (request_sender, request_receiver) = if config.worker_channel_size == 0 {
-            unbounded()
-        } else {
-            bounded(config.worker_channel_size)
-        };
+        let (request_sender, request_receiver) = bounded(config.worker_channel_size);
 
         request_senders.push(request_sender);
         request_receivers.insert(i, request_receiver);
     }
 
     for i in 0..config.socket_workers {
-        let (response_sender, response_receiver) =
-            thingbuf::mpsc::blocking::with_recycle(config.worker_channel_size, Recycler);
+        let (response_sender, response_receiver) = bounded(config.worker_channel_size);
 
         response_senders.push(response_sender);
         response_receivers.insert(i, response_receiver);
@@ -214,16 +200,3 @@ pub fn run(config: Config) -> ::anyhow::Result<()> {
 
     Ok(())
 }
-
-fn est_max_total_channel_memory(config: &Config) -> f64 {
-    let request_channel_max_size = config.swarm_workers
-        * config.worker_channel_size
-        * (size_of::<SocketWorkerIndex>()
-            + size_of::<ConnectedRequest>()
-            + size_of::<CanonicalSocketAddr>());
-    let response_channel_max_size = config.socket_workers
-        * config.worker_channel_size
-        * ConnectedResponseWithAddr::estimated_max_size(&config);
-
-    (request_channel_max_size as u64 + response_channel_max_size as u64) as f64 / (1024.0 * 1024.0)
-}

crates/udp/src/workers/socket/mio.rs

@@ -1,4 +1,3 @@
-use std::borrow::Cow;
 use std::io::{Cursor, ErrorKind};
 use std::sync::atomic::Ordering;
 use std::time::{Duration, Instant};
@@ -42,7 +41,7 @@ pub struct SocketWorker {
     server_start_instant: ServerStartInstant,
     pending_scrape_responses: PendingScrapeResponseSlab,
     socket: UdpSocket,
-    opt_resend_buffer: Option<Vec<(Response, CanonicalSocketAddr)>>,
+    opt_resend_buffer: Option<Vec<(CanonicalSocketAddr, Response)>>,
     buffer: [u8; BUFFER_SIZE],
     polling_mode: PollMode,
     /// Storage for requests that couldn't be sent to swarm worker because channel was full
@@ -133,14 +132,14 @@ impl SocketWorker {
 
             // If resend buffer is enabled, send any responses in it
             if let Some(resend_buffer) = self.opt_resend_buffer.as_mut() {
-                for (response, addr) in resend_buffer.drain(..) {
+                for (addr, response) in resend_buffer.drain(..) {
                     Self::send_response(
                         &self.config,
                         &self.shared_state,
                         &mut self.socket,
                         &mut self.buffer,
                         &mut None,
-                        response.into(),
+                        response,
                         addr,
                     );
                 }
@@ -235,7 +234,7 @@ impl SocketWorker {
                                         &mut self.socket,
                                         &mut self.buffer,
                                         &mut self.opt_resend_buffer,
-                                        CowResponse::Error(Cow::Owned(response)),
+                                        Response::Error(response),
                                         src,
                                     );
                                 }
@@ -310,7 +309,7 @@ impl SocketWorker {
                     &mut self.socket,
                     &mut self.buffer,
                     &mut self.opt_resend_buffer,
-                    CowResponse::Connect(Cow::Owned(response)),
+                    Response::Connect(response),
                     src,
                 );
 
@@ -346,7 +345,7 @@ impl SocketWorker {
                             &mut self.socket,
                             &mut self.buffer,
                             &mut self.opt_resend_buffer,
-                            CowResponse::Error(Cow::Owned(response)),
+                            Response::Error(response),
                             src,
                         );
 
@@ -392,30 +391,20 @@ impl SocketWorker {
     }
 
     fn handle_swarm_worker_responses(&mut self) {
-        loop {
-            let recv_ref = if let Ok(recv_ref) = self.response_receiver.try_recv_ref() {
-                recv_ref
-            } else {
-                break;
-            };
-
-            let response = match recv_ref.kind {
-                ConnectedResponseKind::Scrape => {
+        for (addr, response) in self.response_receiver.try_iter() {
+            let response = match response {
+                ConnectedResponse::Scrape(response) => {
                     if let Some(r) = self
                         .pending_scrape_responses
-                        .add_and_get_finished(&recv_ref.scrape)
+                        .add_and_get_finished(&response)
                     {
-                        CowResponse::Scrape(Cow::Owned(r))
+                        Response::Scrape(r)
                     } else {
                         continue;
                     }
                 }
-                ConnectedResponseKind::AnnounceIpv4 => {
-                    CowResponse::AnnounceIpv4(Cow::Borrowed(&recv_ref.announce_ipv4))
-                }
-                ConnectedResponseKind::AnnounceIpv6 => {
-                    CowResponse::AnnounceIpv6(Cow::Borrowed(&recv_ref.announce_ipv6))
-                }
+                ConnectedResponse::AnnounceIpv4(r) => Response::AnnounceIpv4(r),
+                ConnectedResponse::AnnounceIpv6(r) => Response::AnnounceIpv6(r),
             };
 
             Self::send_response(
@@ -425,7 +414,7 @@ impl SocketWorker {
                 &mut self.buffer,
                 &mut self.opt_resend_buffer,
                 response,
-                recv_ref.addr,
+                addr,
             );
         }
     }
@@ -435,8 +424,8 @@ impl SocketWorker {
         shared_state: &State,
         socket: &mut UdpSocket,
         buffer: &mut [u8],
-        opt_resend_buffer: &mut Option<Vec<(Response, CanonicalSocketAddr)>>,
-        response: CowResponse,
+        opt_resend_buffer: &mut Option<Vec<(CanonicalSocketAddr, Response)>>,
+        response: Response,
         canonical_addr: CanonicalSocketAddr,
     ) {
         let mut buffer = Cursor::new(&mut buffer[..]);
@@ -478,18 +467,18 @@ impl SocketWorker {
                 };
 
                 match response {
-                    CowResponse::Connect(_) => {
+                    Response::Connect(_) => {
                         stats.responses_sent_connect.fetch_add(1, Ordering::Relaxed);
                     }
-                    CowResponse::AnnounceIpv4(_) | CowResponse::AnnounceIpv6(_) => {
+                    Response::AnnounceIpv4(_) | Response::AnnounceIpv6(_) => {
                         stats
                             .responses_sent_announce
                             .fetch_add(1, Ordering::Relaxed);
                     }
-                    CowResponse::Scrape(_) => {
+                    Response::Scrape(_) => {
                         stats.responses_sent_scrape.fetch_add(1, Ordering::Relaxed);
                     }
-                    CowResponse::Error(_) => {
+                    Response::Error(_) => {
                         stats.responses_sent_error.fetch_add(1, Ordering::Relaxed);
                     }
                 }
@@ -503,7 +492,7 @@ impl SocketWorker {
                     if resend_buffer.len() < config.network.resend_buffer_max_len {
                         ::log::debug!("Adding response to resend queue, since sending it to {} failed with: {:#}", addr, err);
 
-                        resend_buffer.push((response.into_owned(), canonical_addr));
+                        resend_buffer.push((canonical_addr, response));
                     } else {
                         ::log::warn!("Response resend buffer full, dropping response");
                     }

crates/udp/src/workers/socket/uring/mod.rs

@@ -2,7 +2,6 @@ mod buf_ring;
 mod recv_helper;
 mod send_buffers;
 
-use std::borrow::Cow;
 use std::cell::RefCell;
 use std::collections::VecDeque;
 use std::net::UdpSocket;
@@ -217,8 +216,7 @@ impl SocketWorker {
                             num_send_added += 1;
                         }
                         Err(send_buffers::Error::NoBuffers(response)) => {
-                            self.local_responses
-                                .push_front((response.into_owned(), addr));
+                            self.local_responses.push_front((response, addr));
 
                             break;
                         }
@@ -233,40 +231,32 @@ impl SocketWorker {
 
             // Enqueue swarm worker responses
             for _ in 0..(sq_space - num_send_added) {
-                let recv_ref = if let Ok(recv_ref) = self.response_receiver.try_recv_ref() {
-                    recv_ref
+                let (addr, response) = if let Ok(r) = self.response_receiver.try_recv() {
+                    r
                 } else {
                     break;
                 };
 
-                let response = match recv_ref.kind {
-                    ConnectedResponseKind::AnnounceIpv4 => {
-                        CowResponse::AnnounceIpv4(Cow::Borrowed(&recv_ref.announce_ipv4))
-                    }
-                    ConnectedResponseKind::AnnounceIpv6 => {
-                        CowResponse::AnnounceIpv6(Cow::Borrowed(&recv_ref.announce_ipv6))
-                    }
-                    ConnectedResponseKind::Scrape => {
-                        if let Some(response) = self
-                            .pending_scrape_responses
-                            .add_and_get_finished(&recv_ref.scrape)
-                        {
-                            CowResponse::Scrape(Cow::Owned(response))
+                let response = match response {
+                    ConnectedResponse::AnnounceIpv4(r) => Response::AnnounceIpv4(r),
+                    ConnectedResponse::AnnounceIpv6(r) => Response::AnnounceIpv6(r),
+                    ConnectedResponse::Scrape(r) => {
+                        if let Some(r) = self.pending_scrape_responses.add_and_get_finished(&r) {
+                            Response::Scrape(r)
                         } else {
                             continue;
                         }
                     }
                 };
 
-                match self.send_buffers.prepare_entry(response, recv_ref.addr) {
+                match self.send_buffers.prepare_entry(response, addr) {
                     Ok(entry) => {
                         unsafe { ring.submission().push(&entry).unwrap() };
 
                         num_send_added += 1;
                     }
                     Err(send_buffers::Error::NoBuffers(response)) => {
-                        self.local_responses
-                            .push_back((response.into_owned(), recv_ref.addr));
+                        self.local_responses.push_back((response, addr));
 
                         break;
                     }

crates/udp/src/workers/socket/uring/send_buffers.rs

@@ -6,14 +6,15 @@ use std::{
 };
 
 use aquatic_common::CanonicalSocketAddr;
+use aquatic_udp_protocol::Response;
 use io_uring::opcode::SendMsg;
 
-use crate::{common::CowResponse, config::Config};
+use crate::config::Config;
 
 use super::{RESPONSE_BUF_LEN, SOCKET_IDENTIFIER};
 
-pub enum Error<'a> {
-    NoBuffers(CowResponse<'a>),
+pub enum Error {
+    NoBuffers(Response),
     SerializationFailed(std::io::Error),
 }
 
@@ -59,9 +60,9 @@ impl SendBuffers {
 
     pub fn prepare_entry<'a>(
         &mut self,
-        response: CowResponse<'a>,
+        response: Response,
         addr: CanonicalSocketAddr,
-    ) -> Result<io_uring::squeue::Entry, Error<'a>> {
+    ) -> Result<io_uring::squeue::Entry, Error> {
         let index = if let Some(index) = self.next_free_index() {
             index
         } else {
@@ -163,7 +164,7 @@ impl SendBuffer {
 
     fn prepare_entry(
         &mut self,
-        response: CowResponse,
+        response: Response,
         addr: CanonicalSocketAddr,
         socket_is_ipv4: bool,
         metadata: &mut SendBufferMetadata,
@@ -237,12 +238,12 @@ pub enum ResponseType {
 }
 
 impl ResponseType {
-    fn from_response(response: &CowResponse) -> Self {
+    fn from_response(response: &Response) -> Self {
         match response {
-            CowResponse::Connect(_) => Self::Connect,
-            CowResponse::AnnounceIpv4(_) | CowResponse::AnnounceIpv6(_) => Self::Announce,
-            CowResponse::Scrape(_) => Self::Scrape,
-            CowResponse::Error(_) => Self::Error,
+            Response::Connect(_) => Self::Connect,
+            Response::AnnounceIpv4(_) | Response::AnnounceIpv6(_) => Self::Announce,
+            Response::Scrape(_) => Self::Scrape,
+            Response::Error(_) => Self::Error,
         }
     }
 }

crates/udp/src/workers/swarm/mod.rs

@@ -47,15 +47,7 @@ pub fn run_swarm_worker(
             // sends in socket workers (doing both could cause a deadlock)
             match (request, src.get().ip()) {
                 (ConnectedRequest::Announce(request), IpAddr::V4(ip)) => {
-                    // It doesn't matter which socket worker receives announce responses
-                    let mut send_ref = response_sender
-                        .send_ref_to_any()
-                        .expect("swarm response channel is closed");
-
-                    send_ref.addr = src;
-                    send_ref.kind = ConnectedResponseKind::AnnounceIpv4;
-
-                    torrents
+                    let response = torrents
                         .ipv4
                         .0
                         .entry(request.info_hash)
@@ -67,19 +59,15 @@ pub fn run_swarm_worker(
                             &request,
                             ip.into(),
                             peer_valid_until,
-                            &mut send_ref.announce_ipv4,
                         );
+
+                    // It doesn't matter which socket worker receives announce responses
+                    response_sender
+                        .send_to_any(src, ConnectedResponse::AnnounceIpv4(response))
+                        .expect("swarm response channel is closed");
                 }
                 (ConnectedRequest::Announce(request), IpAddr::V6(ip)) => {
-                    // It doesn't matter which socket worker receives announce responses
-                    let mut send_ref = response_sender
-                        .send_ref_to_any()
-                        .expect("swarm response channel is closed");
-
-                    send_ref.addr = src;
-                    send_ref.kind = ConnectedResponseKind::AnnounceIpv6;
-
-                    torrents
+                    let response = torrents
                         .ipv6
                         .0
                         .entry(request.info_hash)
@@ -91,28 +79,26 @@ pub fn run_swarm_worker(
                             &request,
                             ip.into(),
                             peer_valid_until,
-                            &mut send_ref.announce_ipv6,
                         );
+
+                    // It doesn't matter which socket worker receives announce responses
+                    response_sender
+                        .send_to_any(src, ConnectedResponse::AnnounceIpv6(response))
+                        .expect("swarm response channel is closed");
                 }
                 (ConnectedRequest::Scrape(request), IpAddr::V4(_)) => {
-                    let mut send_ref = response_sender
-                        .send_ref_to(sender_index)
+                    let response = torrents.ipv4.scrape(request);
+
+                    response_sender
+                        .send_to(sender_index, src, ConnectedResponse::Scrape(response))
                         .expect("swarm response channel is closed");
-
-                    send_ref.addr = src;
-                    send_ref.kind = ConnectedResponseKind::Scrape;
-
-                    torrents.ipv4.scrape(request, &mut send_ref.scrape);
                 }
                 (ConnectedRequest::Scrape(request), IpAddr::V6(_)) => {
-                    let mut send_ref = response_sender
-                        .send_ref_to(sender_index)
+                    let response = torrents.ipv6.scrape(request);
+
+                    response_sender
+                        .send_to(sender_index, src, ConnectedResponse::Scrape(response))
                         .expect("swarm response channel is closed");
-
-                    send_ref.addr = src;
-                    send_ref.kind = ConnectedResponseKind::Scrape;
-
-                    torrents.ipv6.scrape(request, &mut send_ref.scrape);
                 }
             };
         }

crates/udp/src/workers/swarm/storage.rs

@@ -79,24 +79,29 @@ impl TorrentMaps {
 pub struct TorrentMap<I: Ip>(pub IndexMap<InfoHash, TorrentData<I>>);
 
 impl<I: Ip> TorrentMap<I> {
-    pub fn scrape(&mut self, request: PendingScrapeRequest, response: &mut PendingScrapeResponse) {
-        response.slab_key = request.slab_key;
+    pub fn scrape(&mut self, request: PendingScrapeRequest) -> PendingScrapeResponse {
+        let torrent_stats = request
+            .info_hashes
+            .into_iter()
+            .map(|(i, info_hash)| {
+                let stats = self
+                    .0
+                    .get(&info_hash)
+                    .map(|torrent_data| torrent_data.scrape_statistics())
+                    .unwrap_or_else(|| TorrentScrapeStatistics {
+                        seeders: NumberOfPeers::new(0),
+                        leechers: NumberOfPeers::new(0),
+                        completed: NumberOfDownloads::new(0),
+                    });
 
-        let torrent_stats = request.info_hashes.into_iter().map(|(i, info_hash)| {
-            let stats = self
-                .0
-                .get(&info_hash)
-                .map(|torrent_data| torrent_data.scrape_statistics())
-                .unwrap_or_else(|| TorrentScrapeStatistics {
-                    seeders: NumberOfPeers::new(0),
-                    leechers: NumberOfPeers::new(0),
-                    completed: NumberOfDownloads::new(0),
-                });
+                (i, stats)
+            })
+            .collect();
 
-            (i, stats)
-        });
-
-        response.torrent_stats.extend(torrent_stats);
+        PendingScrapeResponse {
+            slab_key: request.slab_key,
+            torrent_stats,
+        }
     }
     /// Remove forbidden or inactive torrents, reclaim space and return number of remaining peers
     fn clean_and_get_statistics(
@@ -187,8 +192,7 @@ impl<I: Ip> TorrentData<I> {
         request: &AnnounceRequest,
         ip_address: I,
         valid_until: ValidUntil,
-        response: &mut AnnounceResponse<I>,
-    ) {
+    ) -> AnnounceResponse<I> {
         let max_num_peers_to_take: usize = if request.peers_wanted.0.get() <= 0 {
             config.protocol.max_response_peers
         } else {
@@ -209,23 +213,24 @@ impl<I: Ip> TorrentData<I> {
         // Create the response before inserting the peer. This means that we
         // don't have to filter it out from the response peers, and that the
         // reported number of seeders/leechers will not include it
-        let opt_removed_peer = match self {
+        let (response, opt_removed_peer) = match self {
             Self::Small(peer_map) => {
                 let opt_removed_peer = peer_map.remove(&peer_map_key);
 
                 let (seeders, leechers) = peer_map.num_seeders_leechers();
 
-                response.fixed = AnnounceResponseFixedData {
-                    transaction_id: request.transaction_id,
-                    announce_interval: AnnounceInterval::new(
-                        config.protocol.peer_announce_interval,
-                    ),
-                    leechers: NumberOfPeers::new(leechers.try_into().unwrap_or(i32::MAX)),
-                    seeders: NumberOfPeers::new(seeders.try_into().unwrap_or(i32::MAX)),
+                let response = AnnounceResponse {
+                    fixed: AnnounceResponseFixedData {
+                        transaction_id: request.transaction_id,
+                        announce_interval: AnnounceInterval::new(
+                            config.protocol.peer_announce_interval,
+                        ),
+                        leechers: NumberOfPeers::new(leechers.try_into().unwrap_or(i32::MAX)),
+                        seeders: NumberOfPeers::new(seeders.try_into().unwrap_or(i32::MAX)),
+                    },
+                    peers: peer_map.extract_response_peers(max_num_peers_to_take),
                 };
 
-                peer_map.extract_response_peers(max_num_peers_to_take, &mut response.peers);
-
                 // Convert peer map to large variant if it is full and
                 // announcing peer is not stopped and will therefore be
                 // inserted
@@ -233,24 +238,25 @@ impl<I: Ip> TorrentData<I> {
                     *self = Self::Large(peer_map.to_large());
                 }
 
-                opt_removed_peer
+                (response, opt_removed_peer)
             }
             Self::Large(peer_map) => {
                 let opt_removed_peer = peer_map.remove_peer(&peer_map_key);
 
                 let (seeders, leechers) = peer_map.num_seeders_leechers();
 
-                response.fixed = AnnounceResponseFixedData {
-                    transaction_id: request.transaction_id,
-                    announce_interval: AnnounceInterval::new(
-                        config.protocol.peer_announce_interval,
-                    ),
-                    leechers: NumberOfPeers::new(leechers.try_into().unwrap_or(i32::MAX)),
-                    seeders: NumberOfPeers::new(seeders.try_into().unwrap_or(i32::MAX)),
+                let response = AnnounceResponse {
+                    fixed: AnnounceResponseFixedData {
+                        transaction_id: request.transaction_id,
+                        announce_interval: AnnounceInterval::new(
+                            config.protocol.peer_announce_interval,
+                        ),
+                        leechers: NumberOfPeers::new(leechers.try_into().unwrap_or(i32::MAX)),
+                        seeders: NumberOfPeers::new(seeders.try_into().unwrap_or(i32::MAX)),
+                    },
+                    peers: peer_map.extract_response_peers(rng, max_num_peers_to_take),
                 };
 
-                peer_map.extract_response_peers(rng, max_num_peers_to_take, &mut response.peers);
-
                 // Try shrinking the map if announcing peer is stopped and
                 // will therefore not be inserted
                 if status == PeerStatus::Stopped {
@@ -259,7 +265,7 @@ impl<I: Ip> TorrentData<I> {
                     }
                 }
 
-                opt_removed_peer
+                (response, opt_removed_peer)
             }
         };
 
@@ -290,6 +296,8 @@ impl<I: Ip> TorrentData<I> {
                 }
             }
         };
+
+        response
     }
 
     pub fn scrape_statistics(&self) -> TorrentScrapeStatistics {
@@ -313,7 +321,7 @@ impl<I: Ip> Default for TorrentData<I> {
 }
 
 /// Store torrents with up to two peers without an extra heap allocation
-/// 
+///
 /// On public open trackers, this is likely to be the majority of torrents.
 #[derive(Default, Debug)]
 pub struct SmallPeerMap<I: Ip>(ArrayVec<(ResponsePeer<I>, Peer), SMALL_PEER_MAP_CAPACITY>);
@@ -344,12 +352,8 @@ impl<I: Ip> SmallPeerMap<I> {
         None
     }
 
-    fn extract_response_peers(
-        &self,
-        max_num_peers_to_take: usize,
-        peers: &mut Vec<ResponsePeer<I>>,
-    ) {
-        peers.extend(self.0.iter().take(max_num_peers_to_take).map(|(k, _)| k))
+    fn extract_response_peers(&self, max_num_peers_to_take: usize) -> Vec<ResponsePeer<I>> {
+        Vec::from_iter(self.0.iter().take(max_num_peers_to_take).map(|(k, _)| *k))
     }
 
     fn clean_and_get_num_peers(
@@ -427,10 +431,9 @@ impl<I: Ip> LargePeerMap<I> {
         &self,
         rng: &mut impl Rng,
         max_num_peers_to_take: usize,
-        peers: &mut Vec<ResponsePeer<I>>,
-    ) {
+    ) -> Vec<ResponsePeer<I>> {
         if self.peers.len() <= max_num_peers_to_take {
-            peers.extend(self.peers.keys());
+            self.peers.keys().copied().collect()
         } else {
             let middle_index = self.peers.len() / 2;
             let num_to_take_per_half = max_num_peers_to_take / 2;
@@ -451,12 +454,16 @@ impl<I: Ip> LargePeerMap<I> {
             let end_half_one = offset_half_one + num_to_take_per_half;
             let end_half_two = offset_half_two + num_to_take_per_half;
 
+            let mut peers = Vec::with_capacity(max_num_peers_to_take);
+
             if let Some(slice) = self.peers.get_range(offset_half_one..end_half_one) {
                 peers.extend(slice.keys());
             }
             if let Some(slice) = self.peers.get_range(offset_half_two..end_half_two) {
                 peers.extend(slice.keys());
             }
+
+            peers
         }
     }