deps(udp): make tracing optional

This commit makes the `tracing` dependency in `quinn-udp` optional, but enabled
by default. If disabled, `log` is used.

Cargo.toml

@@ -18,6 +18,7 @@ futures-io = "0.3.19"
 hdrhistogram = { version = "7.2", default-features = false }
 hex-literal = "0.4"
 lazy_static = "1"
+log = "0.4"
 once_cell = "1.19"
 pin-project-lite = "0.2"
 rand = "0.8"

quinn-udp/Cargo.toml

@@ -14,14 +14,13 @@ workspace = ".."
 all-features = true
 
 [features]
-default = ["log"]
-# Write logs via the `log` crate when no `tracing` subscriber exists
-log = ["tracing/log"]
+default = ["tracing"]
 
 [dependencies]
 libc = "0.2.113"
 socket2 = { workspace = true }
-tracing = { workspace = true }
+tracing = { workspace = true, optional = true }
+log = { workspace = true }
 
 [target.'cfg(windows)'.dependencies]
 once_cell = { workspace = true }

quinn-udp/src/lib.rs

@@ -37,6 +37,9 @@ use std::{
     time::{Duration, Instant},
 };
 
+#[cfg(not(feature = "tracing"))]
+use log::warn;
+#[cfg(feature = "tracing")]
 use tracing::warn;
 
 #[cfg(any(unix, windows))]

quinn-udp/src/unix.rs

@@ -14,6 +14,11 @@ use std::{
 
 use socket2::SockRef;
 
+#[cfg(not(feature = "tracing"))]
+use log::{debug, error};
+#[cfg(feature = "tracing")]
+use tracing::{debug, error};
+
 use super::{
     cmsg, log_sendmsg_error, EcnCodepoint, RecvMeta, Transmit, UdpSockRef, IO_ERROR_LOG_INTERVAL,
 };
@@ -87,7 +92,7 @@ impl UdpSocketState {
         if is_ipv4 || !io.only_v6()? {
             if let Err(err) = set_socket_option(&*io, libc::IPPROTO_IP, libc::IP_RECVTOS, OPTION_ON)
             {
-                tracing::debug!("Ignoring error setting IP_RECVTOS on socket: {err:?}",);
+                debug!("Ignoring error setting IP_RECVTOS on socket: {err:?}",);
             }
         }
 
@@ -283,7 +288,7 @@ fn send(
                         // Prevent new transmits from being scheduled using GSO. Existing GSO transmits
                         // may already be in the pipeline, so we need to tolerate additional failures.
                         if state.max_gso_segments() > 1 {
-                            tracing::error!("got transmit error, halting segmentation offload");
+                            error!("got transmit error, halting segmentation offload");
                             state
                                 .max_gso_segments
                                 .store(1, std::sync::atomic::Ordering::Relaxed);

quinn/Cargo.toml

@@ -28,7 +28,7 @@ runtime-async-std = ["async-io", "async-std"]
 runtime-smol = ["async-io", "smol"]
 
 # Write logs via the `log` crate when no `tracing` subscriber exists
-log = ["tracing/log", "proto/log", "udp/log"]
+log = ["tracing/log", "proto/log"]
 
 [dependencies]
 async-io = { workspace = true, optional = true }
@@ -45,7 +45,7 @@ socket2 = { workspace = true }
 thiserror = { workspace = true }
 tracing =  { workspace = true }
 tokio = { workspace = true }
-udp = { package = "quinn-udp", path = "../quinn-udp", version = "0.5", default-features = false }
+udp = { package = "quinn-udp", path = "../quinn-udp", version = "0.5", default-features = false, features = ["tracing"] }
 
 [dev-dependencies]
 anyhow = { workspace = true }