Extract send free function for fallback implementation

This allows us to have it follow the exact same implementation as the
unix and windows one.

quinn-udp/src/fallback.rs

@@ -25,31 +25,25 @@ impl UdpSocketState {
     }
 
     pub fn send(&self, socket: UdpSockRef<'_>, transmit: &Transmit<'_>) -> io::Result<()> {
-        let Err(e) = socket.0.send_to(
-            transmit.contents,
-            &socket2::SockAddr::from(transmit.destination),
-        ) else {
-            return Ok(());
-        };
-        if e.kind() == io::ErrorKind::WouldBlock {
-            return Err(e);
-        }
+        match send(socket, transmit) {
+            Ok(()) => Ok(()),
+            Err(e) if e.kind() == io::ErrorKind::WouldBlock => Err(e),
+            Err(e) => {
+                // Other errors are ignored, since they will usually be handled
+                // by higher level retransmits and timeouts.
+                // - PermissionDenied errors have been observed due to iptable rules.
+                //   Those are not fatal errors, since the
+                //   configuration can be dynamically changed.
+                // - Destination unreachable errors have been observed for other
+                log_sendmsg_error(&self.last_send_error, e, transmit);
 
-        // Other errors are ignored, since they will usually be handled
-        // by higher level retransmits and timeouts.
-        // - PermissionDenied errors have been observed due to iptable rules.
-        //   Those are not fatal errors, since the
-        //   configuration can be dynamically changed.
-        // - Destination unreachable errors have been observed for other
-        log_sendmsg_error(&self.last_send_error, e, transmit);
-        Ok(())
+                Ok(())
+            }
+        }
     }
 
     pub fn try_send(&self, socket: UdpSockRef<'_>, transmit: &Transmit<'_>) -> io::Result<()> {
-        socket.0.send_to(
-            transmit.contents,
-            &socket2::SockAddr::from(transmit.destination),
-        )
+        send(socket, transmit)
     }
 
     pub fn recv(
@@ -92,4 +86,11 @@ impl UdpSocketState {
     }
 }
 
+fn send(socket: UdpSockRef<'_>, transmit: &Transmit<'_>) -> io::Result<()> {
+    socket.0.send_to(
+        transmit.contents,
+        &socket2::SockAddr::from(transmit.destination),
+    )
+}
+
 pub(crate) const BATCH_SIZE: usize = 1;