fix: Use 1MB socket RX buffers

Cargo.toml

@@ -34,7 +34,7 @@ enumset = { version = "1.1", default-features = false }
 hex = { version = "0.4", default-features = false }
 log = { version = "0.4", default-features = false }
 qlog = { version = "0.15", default-features = false }
-quinn-udp = { version = "0.5.10", default-features = false, features = ["direct-log", "fast-apple-datapath"] }
+quinn-udp = { version = "0.5.11", default-features = false, features = ["direct-log", "fast-apple-datapath"] }
 regex = { version = "1.9", default-features = false }
 static_assertions = { version = "1.1", default-features = false }
 strum = { version = "0.26", default-features = false, features = ["derive"] }

neqo-bin/src/udp.rs

@@ -8,7 +8,7 @@
 
 use std::{io, net::SocketAddr};
 
-use neqo_common::Datagram;
+use neqo_common::{qdebug, Datagram};
 use neqo_udp::{DatagramIter, RecvBuf};
 
 /// Ideally this would live in [`neqo-udp`]. [`neqo-udp`] is used in Firefox.
@@ -26,10 +26,36 @@ pub struct Socket {
 impl Socket {
     /// Create a new [`Socket`] bound to the provided address, not managed externally.
     pub fn bind<A: std::net::ToSocketAddrs>(addr: A) -> Result<Self, io::Error> {
+        const ONE_MB: usize = 1 << 20;
         let socket = std::net::UdpSocket::bind(addr)?;
+        let state = quinn_udp::UdpSocketState::new((&socket).into())?;
+
+        let send_buf_before = state.send_buffer_size((&socket).into())?;
+        // FIXME: We need to experiment if increasing this actually improves performance.
+        // Also, on BSD and Apple targets, this seems to increase the `net.inet.udp.maxdgram`
+        // sysctl, which is not the same as the socket buffer.
+        // if send_buf_before < ONE_MB {
+        //     state.set_send_buffer_size((&socket).into(), ONE_MB)?;
+        //     let send_buf_after = state.send_buffer_size((&socket).into())?;
+        //     qdebug!("Increasing socket send buffer size from {send_buf_before} to {ONE_MB}, now:
+        // {send_buf_after}"); } else {
+        //     qdebug!("Default socket send buffer size is {send_buf_before}, not changing");
+        // }
+        qdebug!("Default socket send buffer size is {send_buf_before}");
+
+        let recv_buf_before = state.recv_buffer_size((&socket).into())?;
+        if recv_buf_before < ONE_MB {
+            // Same as Firefox.
+            // <https://searchfox.org/mozilla-central/source/modules/libpref/init/StaticPrefList.yaml#13474-13478>
+            state.set_recv_buffer_size((&socket).into(), ONE_MB)?;
+            let recv_buf_after = state.recv_buffer_size((&socket).into())?;
+            qdebug!("Increasing socket recv buffer size from {recv_buf_before} to {ONE_MB}, now: {recv_buf_after}");
+        } else {
+            qdebug!("Default socket receive buffer size is {recv_buf_before}, not changing");
+        }
 
         Ok(Self {
-            state: quinn_udp::UdpSocketState::new((&socket).into())?,
+            state,
             inner: tokio::net::UdpSocket::from_std(socket)?,
         })
     }