Firefox probing changes.

Author: larseggert

quinn-udp/Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "quinn-udp"
-version = "0.6.0"
+version = "0.5.13" # FIXME: Temporary Firefox vendoring hack. Revert.
 edition.workspace = true
 rust-version.workspace = true
 license.workspace = true
@@ -19,6 +19,7 @@ tracing-log = ["tracing/log"]
 log = ["dep:log"]
 # Use private Apple APIs to send multiple packets in a single syscall.
 fast-apple-datapath = []
+direct-log = [] # FIXME: Temporary Firefox vendoring hack. Revert.
 
 [dependencies]
 libc = "0.2.175"

quinn-udp/src/lib.rs

@@ -258,6 +258,31 @@ impl EcnCodepoint {
     }
 }
 
+/// Pre-sets Apple fast path availability from external code.
+///
+/// This allows embedders (e.g., Firefox) to perform the `sendmsg_x`/`recvmsg_x`
+/// probe in C++ and pass the result to quinn-udp, avoiding socket creation and
+/// forking in Rust code.
+///
+/// Must be called before any socket operations that would trigger the internal
+/// probe. Returns the effective value after the set attempt: if already
+/// initialized, returns the existing value; otherwise returns the newly set value.
+///
+/// # Example
+///
+/// ```c
+/// // In C++ code:
+/// extern "C" bool quinn_udp_set_apple_fast_path_available(bool available);
+///
+/// bool probeResult = PerformAppleFastDatapathProbe();
+/// bool effective = quinn_udp_set_apple_fast_path_available(probeResult);
+/// ```
+#[cfg(apple_fast)]
+#[no_mangle]
+pub extern "C" fn quinn_udp_set_apple_fast_path_available(available: bool) -> bool {
+    imp::set_apple_fast_path_available(available)
+}
+
 #[cfg(test)]
 mod tests {
     use std::net::Ipv4Addr;

quinn-udp/src/unix.rs

@@ -1228,6 +1228,19 @@ mod probe {
         *FAST_PATH_AVAILABLE.get_or_init(run_probe)
     }
 
+    /// Pre-sets the fast path availability from external code.
+    ///
+    /// This allows embedders to perform the probe externally (e.g., in C++ code)
+    /// and pass the result to quinn-udp. Useful when the Rust code is not allowed
+    /// to create sockets or fork processes.
+    ///
+    /// Returns the effective value after the set attempt. If the value was already
+    /// initialized, returns the existing value; otherwise returns the newly set value.
+    pub(super) fn set_fast_path_available(available: bool) -> bool {
+        let _ = FAST_PATH_AVAILABLE.set(available);
+        is_fast_path_available()
+    }
+
     /// Runs the probe by forking a child process to test the private APIs.
     fn run_probe() -> bool {
         match probe(fast_path_available) {
@@ -1371,3 +1384,11 @@ mod probe {
         }
     }
 }
+
+/// Pre-sets Apple fast path availability from external code.
+///
+/// See [`probe::set_fast_path_available`] for details.
+#[cfg(apple_fast)]
+pub(crate) fn set_apple_fast_path_available(available: bool) -> bool {
+    probe::set_fast_path_available(available)
+}