net listen backlog update, follow-up from rust-lang#97963.

FreeBSD and using system limit instead for others.

Author: devnexen

library/std/src/os/unix/net/listener.rs

@@ -73,10 +73,11 @@ impl UnixListener {
         unsafe {
             let inner = Socket::new_raw(libc::AF_UNIX, libc::SOCK_STREAM)?;
             let (addr, len) = sockaddr_un(path.as_ref())?;
-            #[cfg(target_os = "linux")]
-            const backlog: libc::c_int = -1;
-            #[cfg(not(target_os = "linux"))]
-            const backlog: libc::c_int = 128;
+            const backlog: libc::c_int = if cfg!(any(target_os = "linux", target_os = "freebsd")) {
+                -1
+            } else {
+                libc::SOMAXCONN
+            };
 
             cvt(libc::bind(inner.as_inner().as_raw_fd(), &addr as *const _ as *const _, len as _))?;
             cvt(libc::listen(inner.as_inner().as_raw_fd(), backlog))?;