TCP Fast Open

[exim.git] / doc / doc-txt / NewStuff

diff --git a/doc/doc-txt/NewStuff b/doc/doc-txt/NewStuff
index b9ed8a00dd330235bd73e3ea0065e6d38e973651..83ee4c3afe86b075721d3e5ecf0c556d1f90900e 100644 (file)
--- a/doc/doc-txt/NewStuff
+++ b/doc/doc-txt/NewStuff
@@ -38,8 +38,30 @@ Version 4.88
  9. Expansion operator escape8bit, like escape but not touching newline etc..
 
 10. Feature macros, generated from compile options.  All start with "_HAVE_"
-    and go on with some roughly recognisable name.  Use the "-bP macros"
-    command-line option to see what is present.
+    and go on with some roughly recognisable name.  Driver macros, for
+    router, transport and authentication drivers; names starting with "_DRVR_".
+    Option macros, for each configuration-file option; all start with "_OPT_".
+    Use the "-bP macros" command-line option to see what is present.
+
+11. Integer values for options can take a "G" multiplier.
+
+12. defer=pass option for the ACL control cutthrough_delivery, to reflect 4xx
+    returns from the target back to the initiator, rather than spooling the
+    message.
+
+13. New built-in constants available for tls_dhparam and default changed.
+
+14. If built with EXPERIMENTAL_QUEUEFILE, a queuefile transport, for writing
+    out copies of the message spool files for use by 3rd-party scanners.
+
+15. A new option on the smtp transport, hosts_try_fastopen.  If the system
+    supports it (on Linux it must be enabled in the kernel by the sysadmin)
+    try to use RFC 7413 "TCP Fast Open".  No data is sent on the SYN segment
+    but it permits a peer that also supports the facility to send its SMTP
+    banner immediately after the SYN,ACK segment rather then waiting for
+    another ACK - so saving up to one roundtrip time.  Because it requires
+    previous communication with the peer (we save a cookie from it) this
+    will only become active on frequently-contected destinations.
 
 
 Version 4.87