PIPE_CONNECT: promote from experimental

3 files changed, 51 insertions, 82 deletions

diff --git a/doc/doc-docbook/spec.xfpt b/doc/doc-docbook/spec.xfpt
index bfacdef81..34c4310d5 100644
--- a/doc/doc-docbook/spec.xfpt
+++ b/doc/doc-docbook/spec.xfpt
@@ -14368,6 +14368,7 @@ See also the &'Policy controls'& section above.
 .row &%ignore_fromline_hosts%&       "allow &""From ""& from these hosts"
 .row &%ignore_fromline_local%&       "allow &""From ""& from local SMTP"
 .row &%pipelining_advertise_hosts%&  "advertise pipelining to these hosts"
+.row &%pipelining_connect_advertise_hosts%& "advertise pipelining to these hosts"
 .row &%prdr_enable%&                 "advertise PRDR to all hosts"
 .row &%smtputf8_advertise_hosts%&    "advertise SMTPUTF8 to these hosts"
 .row &%tls_advertise_hosts%&         "advertise TLS to these hosts"
@@ -16373,6 +16374,19 @@ for each SMTP command and response. When PIPELINING is advertised, Exim assumes
 that clients will use it; &"out of order"& commands that are &"expected"& do
 not count as protocol errors (see &%smtp_max_synprot_errors%&).
 
+.new
+.option pipelining_connect_advertise_hosts main "host list&!!" *
+.cindex "pipelining" "early connection"
+.cindex "pipelining" PIPE_CONNECT
+If Exim is built with the SUPPORT_PIPE_CONNECT build option
+this option controls which hosts the facility is advertised to
+and from which pipeline early-connection (before MAIL) SMTP
+commands are acceptable.
+When used, the pipelining saves on roundtrip times.
+
+Currently the option name &"X_PIPE_CONNECT"& is used.
+.wen
+
 
 .option prdr_enable main boolean false
 .cindex "PRDR" "enabling on server"
@@ -24553,6 +24567,30 @@ facilities such as AUTH, PIPELINING, SIZE, and STARTTLS.
 Exim will not use the SMTP PIPELINING extension when delivering to any host
 that matches this list, even if the server host advertises PIPELINING support.
 
+.new
+.option hosts_pipe_connect smtp "host list&!!" unset
+.cindex "pipelining" "early connection"
+.cindex "pipelining" PIPE_CONNECT
+If Exim is built with the SUPPORT_PIPE_CONNECT build option
+this option controls which to hosts the facility watched for
+and recorded, and used for subsequent connections.
+
+The retry hints database is used for the record,
+and records are subject to the &%retry_data_expire%& option.
+When used, the pipelining saves on roundtrip times.
+It also turns SMTP into a client-first protocol
+so combines well with TCP Fast Open.
+
+Note:
+When the facility is used, the transport &%helo_data%& option
+will be expanded before the &$sending_ip_address$& variable
+is filled in.
+A check is made for the use of that variable, without the
+presence of a &"def:"& test on it, but suitably complex coding
+can avoid the check and produce unexpected results.
+You have been warned.
+.wen
+
 
 .option hosts_avoid_tls smtp "host list&!!" unset
 .cindex "TLS" "avoiding for certain hosts"
@@ -37380,6 +37418,15 @@ The field is a single "L".
 
 On accept lines, where PIPELINING was offered but not used by the client,
 the field has a minus appended.
+
+.new
+.cindex "pipelining" "early connection"
+If Exim is built with the SUPPORT_PIPE_CONNECT build option
+accept "L" fields have a period appended if the feature was
+offered but not used, or an asterisk appended if used.
+Delivery "L" fields have an asterisk appended if used.
+.wen
+
 .next
 .cindex "log" "queue run"
 .cindex "queue runner" "logging"
diff --git a/doc/doc-txt/ChangeLog b/doc/doc-txt/ChangeLog
index 62801740b..b4e58990e 100644
--- a/doc/doc-txt/ChangeLog
+++ b/doc/doc-txt/ChangeLog
@@ -121,9 +121,12 @@ JH/24 Fix duplicated logging of peer name/address, on a transport connection-
       reject under TFO.
 
 JH/25 The smtp transport option "hosts_try_fastopen" now enables all hosts by
-      default.  If the platfor supports and has the facility enabled, it will
+      default.  If the platform supports and has the facility enabled, it will
       be requested on all coneections.
 
+JH/26 The PIPE_CONNECT facility is promoted from experimental status and is now
+      controlled by the build-time option SUPPORT_PIPE_CONNECT.
+
 
 Exim version 4.92
 -----------------
diff --git a/doc/doc-txt/experimental-spec.txt b/doc/doc-txt/experimental-spec.txt
index 328d0940a..f748f6146 100644
--- a/doc/doc-txt/experimental-spec.txt
+++ b/doc/doc-txt/experimental-spec.txt
@@ -873,87 +873,6 @@ used via the transport in question.
 
 
 
-Early pipelining support
-------------------------
-Ref: https://datatracker.ietf.org/doc/draft-harris-early-pipe/
-
-If compiled with EXPERIMENTAL_PIPE_CONNECT support is included for this feature.
-The server advertises the feature in its EHLO response, currently using the name
-"X_PIPE_CONNECT" (this will change, some time in the future).
-A client may cache this information, along with the rest of the EHLO response,
-and use it for later connections.  Those later ones can send esmtp commands before
-a banner is received.
-
-Up to 1.5 roundtrip times can be taken out of cleartext connections, 2.5 on
-STARTTLS connections.
-
-In combination with the traditional PIPELINING feature the following example
-sequences are possible (among others):
-
-(client)                (server)
-
-EHLO,MAIL,RCPT,DATA ->
-                     <- banner,EHLO-resp,MAIL-ack,RCPT-ack,DATA-goahead
-message-data        ->
-------
-
-EHLO,MAIL,RCPT,BDAT              ->
-                                  <- banner,EHLO-resp,MAIL-ack,RCPT-ack
-message-data                     ->
-------
-
-EHLO,STARTTLS                     ->
-                                   <- banner,EHLO-resp,TLS-goahead
-TLS1.2-client-hello               ->
-                                   <- TLS-server-hello,cert,hello-done
-client-Kex,change-cipher,finished ->
-                                   <- change-cipher,finished
-EHLO,MAIL,RCPT,DATA               ->
-                                   <- EHLO-resp,MAIL-ack,RCPT-ack,DATA-goahead
-
-------
-(tls-on-connect)
-TLS1.2-client-hello               ->
-                                   <- TLS-server-hello,cert,hello-done
-client-Kex,change-cipher,finished ->
-                                   <- change-cipher,finshed
-                                   <- banner
-EHLO,MAIL,RCPT,DATA               ->
-                                   <- EHLO-resp,MAIL-ack,RCPT-ack,DATA-goahead
-
-Where the initial client packet is SMTP, it can combine with the TCP Fast Open
-feature and be sent in the TCP SYN.
-
-
-A main-section option "pipelining_connect_advertise_hosts" (default: *)
-and an smtp transport option "hosts_pipe_connect" (default: unset)
-control the feature.
-
-If the "pipelining" log_selector is enabled, the "L" field in server <=
-log lines has a period appended if the feature was advertised but not used;
-or has an asterisk appended if the feature was used.  In client => lines
-the "L" field has an asterisk appended if the feature was used.
-
-The "retry_data_expire" option controls cache invalidation.
-Entries are also rewritten (or cleared) if the adverised features
-change.
-
-
-NOTE: since the EHLO command must be constructed before the connection is
-made it cannot depend on the interface IP address that will be used.
-The string "$sending_ip_address" is checked for; if it appears in helo_data
-and "def:sending_ip_address" does not, the facility is disabled.
-
-Transport configurations should be checked for this.  An example avoidance:
-
- helo_data =	${if def:sending_ip_address \
-		   {${lookup dnsdb{>! ptr=$sending_ip_address} \
-			{${sg{$value} {^([^!]*).*\$} {\$1}}} fail}} \
-		   {$primary_hostname}}
-
-
-
-
 TLS Session Resumption
 ----------------------
 TLS Session Resumption for TLS 1.2 and TLS 1.3 connections can be used (defined