Merge pull request #1065 from c-cube/simon/lwt-io-socket-options-doc

add doc for set_tcp_nodelay in Lwt_io

Author: raphael-proust

CHANGES

@@ -1,3 +1,11 @@
+===== 5.10.0 =====
+
+====== Misc
+
+  * In `Lwt_io`, functions that create sockets gain new options `?set_tcp_nodelay` and `?prepare_fd`. (#1061, Simon Cruanes)
+
+  * Breaking change: `?set_tcp_nodelay` is set to `true` by default which means TCP_NODELAY is now set by default for such functions. (#1061, Simon Cruanes)
+
 ===== 5.9.2 =====
 
 ====== Packaging ======

src/unix/lwt_io.mli

@@ -573,9 +573,12 @@ val open_connection :
       @raise Unix.Unix_error on error.
 
       @param set_tcp_nodelay if true, [TCP_NODELAY] is set on the socket FD. This
-        avoids a surprising 40ms delay in some situations.
+        avoids a surprising 40ms delay in some situations. It disables
+        Nagle's algorithm (https://en.wikipedia.org/wiki/Nagle%27s_algorithm).
         See for example https://brooker.co.za/blog/2024/05/09/nagle.html for why.
 
+        The default value is [true].
+
       @param prepare_fd is a custom callback that can be used to modify the socket FD
       before it is turned into high level channels.