Squashed commit of PIPE_CONNECT

4 files changed, 86 insertions, 2 deletions

diff --git a/doc/doc-docbook/spec.xfpt b/doc/doc-docbook/spec.xfpt
index c84c9b4d1..4e99e6c0d 100644
--- a/doc/doc-docbook/spec.xfpt
+++ b/doc/doc-docbook/spec.xfpt
@@ -36965,6 +36965,7 @@ immediately after the time and date.
 &%pipelining%&: A field is added to delivery and accept
 log lines when the ESMTP PIPELINING extension was used.
 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.
 .next
diff --git a/doc/doc-txt/NewStuff b/doc/doc-txt/NewStuff
index cc9721ada..fb336b8af 100644
--- a/doc/doc-txt/NewStuff
+++ b/doc/doc-txt/NewStuff
@@ -17,7 +17,8 @@ Version 4.92
  2. The ${readsocket } expansion item now takes a "tls" option, doing the
     obvious thing.
 
- 3. EXPERIMENTAL_REQUIRETLS.  See the experimental.spec file.
+ 3. EXPERIMENTAL_REQUIRETLS and EXPERIMENTAL_PIPE_CONNECT optional build
+    features.  See the experimental.spec file.
 
  4. If built with SUPPORT_I18N a "utf8_downconvert" option on the smtp transport.
 
diff --git a/doc/doc-txt/OptionLists.txt b/doc/doc-txt/OptionLists.txt
index 8d20f6fe2..fec47946a 100644
--- a/doc/doc-txt/OptionLists.txt
+++ b/doc/doc-txt/OptionLists.txt
@@ -54,7 +54,7 @@ acl_not_smtp_mime                    string*         unset         main
 acl_smtp_auth                        string*         unset         main              4.00
 acl_smtp_connect                     string*         unset         main              4.11
 acl_smtp_data                        string*         unset         main              4.00
-acl_smtp_data_prdr                   string*         unset         main              4.82 with experimental_prdr
+acl_smtp_data_prdr                   string*         unset         main              4.82 with experimental_prdr, 4.83 unless disable_prdr
 acl_smtp_dkim                        string*         unset         main              4.70 unless disable_dkim
 acl_smtp_etrn                        string*         unset         main              4.00
 acl_smtp_expn                        string*         unset         main              4.00
@@ -300,6 +300,7 @@ hosts_max_try_hardlimit              integer         50            smtp
 hosts_nopass_tls                     host list       unset         smtp              4.00
 hosts_noproxy_tls                    host list       "*"           smtp              4.90
 hosts_override                       boolean         false         smtp              2.11
+hosts_pipe_connect		     host_list	     unset	   smtp		     4.93 if experimental_pipe_connect
 hosts_randomize                      boolean         false         manualroute       4.00
                                                      false         smtp              3.14
 hosts_require_auth                   host list       unset         smtp              4.00
@@ -412,6 +413,7 @@ pid_file_path                        string          ++            main
 pipe_as_creator                      boolean         false         pipe
 pipe_transport                       string*         unset         redirect          4.00
 pipelining_advertise_hosts           host list       "*"           main              4.14
+pipelining__connect_advertise_hosts  host list       "*"           main              4.92 if experimental_pipe_connect
 port                                 integer         0             iplookup          4.00
                                      string          "smtp"        smtp
 preserve_message_logs                boolean         false         main
diff --git a/doc/doc-txt/experimental-spec.txt b/doc/doc-txt/experimental-spec.txt
index 49935fb40..d5a75f5b3 100644
--- a/doc/doc-txt/experimental-spec.txt
+++ b/doc/doc-txt/experimental-spec.txt
@@ -904,6 +904,86 @@ Note that REQUIRETLS is only advertised once a TLS connection is achieved
 like "swaks -s 127.0.0.1 -tls -q HELO".
 
 
+
+
+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,finshed
+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.
+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}}
+
+
+
+
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