postfix-2.3-20051228

postfix/HISTORY

@@ -11690,6 +11690,23 @@ Apologies for any names omitted.
 	(example: sockaddr_to_hostaddr: Unknown error: success).
 	File: util/myaddrinfo.c.
 
+20051228
+
+	Workaround: don't pipeline the DOT+QUIT commands in the
+	SMTP client. The 20050929 paranoia about malformed server
+	replies eliminated a rare occurrence of "lost mail" with
+	sites that mis-implement DOT+QUIT pipelining. However, we
+	now have a larger occurrence of repeated deliveries to sites
+	with different implementation errors.  
+
+	The default "smtp_pipeline_dot_quit = never" setting
+	eliminates the repeated deliveries at the cost of a small
+	performance loss with normal deliveries.  Other settings
+	are "always" (always pipeline the DOT+QUIT commands, when
+	pipelining is enabled) and "newmail" (pipeline DOT+QUIT
+	only when mail is newer than $minimal_backoff_time).
+	Files: smtp/smtp_proto.c, smtp/smtp.c.
+
 Open problems:
 
 	"postsuper -r" no longer resets the message arrival time,

postfix/RELEASE_NOTES

@@ -17,6 +17,20 @@ Incompatibility with Postfix 2.1 and earlier
 If you upgrade from Postfix 2.1 or earlier, read RELEASE_NOTES-2.2
 before proceeding.
 
+Incompatibility with snapshot 20051228
+======================================
+
+New parameter "smtp_pipeline_dot_quit" (default: "never") to work
+around broken servers and firewalls.  After one documented case of
+lost mail, as of 20050929 Postfix is more paranoid about malformed
+SMTP server replies. Unfortuately this results in repeated delivery
+attempts with other broken systems.  To avoid this, the SMTP+LMTP
+client no longer pipelines the DOT+QUIT commands by default. Instead
+of "never" you can specify "always" (self-evident) or "newmail"
+(pipeline DOT+QUIT only when mail is newer than $minimal_backoff_time,
+so that the number of duplicate deliveries is limited).  More details
+are in the postconf(5) manual.
+
 Major changes with snapshot 20051222
 ====================================
 

postfix/html/postconf.5.html

@@ -3224,7 +3224,7 @@ case insensitive lists of LHLO keywords (pipelining, starttls,
 auth, etc.) that the LMTP client will ignore in the LHLO response
 from a remote LMTP server. See <a href="postconf.5.html#lmtp_discard_lhlo_keywords">lmtp_discard_lhlo_keywords</a> for
 details. The table is not indexed by hostname for consistency with
-smtpd_discard_ehlo_keyword_address_map </p>
+<a href="postconf.5.html#smtpd_discard_ehlo_keyword_address_maps">smtpd_discard_ehlo_keyword_address_maps</a>. </p>
 
 <p> This feature is available in Postfix 2.3 and later. </p>
 
@@ -3377,6 +3377,15 @@ parameter.  See there for details. </p>
 <p> This feature is available in Postfix 2.3 and later. </p>
 
 
+</DD>
+
+<DT><b><a name="lmtp_pipeline_dot_quit">lmtp_pipeline_dot_quit</a>
+(default: never)</b></DT><DD>
+
+<p> The LMTP-specific version of the <a href="postconf.5.html#smtp_pipeline_dot_quit">smtp_pipeline_dot_quit</a>
+configuration parameter.  See there for details. </p>
+
+
 </DD>
 
 <DT><b><a name="lmtp_pix_workaround_delay_time">lmtp_pix_workaround_delay_time</a>
@@ -6892,6 +6901,45 @@ complete the EHLO and TLS handshake (Postfix version 2.3 and later).  </p>
 <a href="postconf.5.html#smtp_always_send_ehlo">smtp_always_send_ehlo</a> parameter.  </p>
 
 
+</DD>
+
+<DT><b><a name="smtp_pipeline_dot_quit">smtp_pipeline_dot_quit</a>
+(default: never)</b></DT><DD>
+
+<p> When ESMTP command pipelining is enabled, whether or not the
+SMTP client will send the QUIT command before it has received the
+server's END-OF-DATA reply. </p>
+
+<p> Specify one of the following: </p>
+
+<dl>
+
+<dt> <b>always</b> </dt> <dd> Always pipeline the END-OF-DATA and
+QUIT commands.  With servers or firewalls that mis-implement
+END-OF-DATA + QUIT pipelining, mail will be delivered repeatedly
+until it expires in the queue.  </dd>
+
+<dt> <b>never</b> </dt> <dd> Wait for the server's END-OF-DATA reply
+before sending the QUIT command. This avoids repeated delivery
+attempts with servers and firewalls that mis-implement END-OF-DATA
++ QUIT pipelining, at the cost of a small performance loss with
+sites that correctly implement SMTP. </dd>
+
+<dt> <b>newmail</b> </dt> <dd> Pipeline the END-OF-DATA and QUIT
+commands only when mail is newer than $<a href="postconf.5.html#minimal_backoff_time">minimal_backoff_time</a>.  This
+limits the number of repeated deliveries with servers and firewalls
+that mis-implement END-OF-DATA + QUIT pipelining, while avoiding
+the performance loss associated with the "never" setting for normal
+deliveries.  </dd>
+
+</dl>
+
+<p> Note: when <a href="postconf.5.html#smtp_fallback_relay">smtp_fallback_relay</a> is used, the "always" and "newmail"
+settings become identical in practice. </p>
+
+<p> This feature is available in Postfix 2.3 and later. </p>
+
+
 </DD>
 
 <DT><b><a name="smtp_pix_workaround_delay_time">smtp_pix_workaround_delay_time</a>

postfix/html/smtp.8.html

@@ -170,6 +170,12 @@ SMTP(8)                                                                SMTP(8)
               The maximal length of message header and body lines
               that Postfix will send via SMTP.
 
+       <b><a href="postconf.5.html#smtp_pipeline_dot_quit">smtp_pipeline_dot_quit</a> (never)</b>
+              When  ESMTP  command pipelining is enabled, whether
+              or not the SMTP client will send the  QUIT  command
+              before  it  has  received  the server's END-OF-DATA
+              reply.
+
        <b><a href="postconf.5.html#smtp_pix_workaround_delay_time">smtp_pix_workaround_delay_time</a> (10s)</b>
               How long the  Postfix  SMTP  client  pauses  before
               sending ".&lt;CR&gt;&lt;LF&gt;" in order to work around the PIX

postfix/man/man5/postconf.5

@@ -1729,7 +1729,7 @@ case insensitive lists of LHLO keywords (pipelining, starttls,
 auth, etc.) that the LMTP client will ignore in the LHLO response
 from a remote LMTP server. See lmtp_discard_lhlo_keywords for
 details. The table is not indexed by hostname for consistency with
-smtpd_discard_ehlo_keyword_address_map
+smtpd_discard_ehlo_keyword_address_maps.
 .PP
 This feature is available in Postfix 2.3 and later.
 .SH lmtp_discard_lhlo_keywords (default: $myhostname)
@@ -1808,6 +1808,9 @@ The LMTP-specific version of the smtp_mx_session_limit configuration
 parameter.  See there for details.
 .PP
 This feature is available in Postfix 2.3 and later.
+.SH lmtp_pipeline_dot_quit (default: never)
+The LMTP-specific version of the smtp_pipeline_dot_quit
+configuration parameter.  See there for details.
 .SH lmtp_pix_workaround_delay_time (default: 10s)
 The LMTP-specific version of the smtp_pix_workaround_delay_time
 configuration parameter.  See there for details.
@@ -3838,6 +3841,35 @@ This feature is available in Postfix 2.1 and later.
 .SH smtp_never_send_ehlo (default: no)
 Never send EHLO at the start of an SMTP session. See also the
 smtp_always_send_ehlo parameter.
+.SH smtp_pipeline_dot_quit (default: never)
+When ESMTP command pipelining is enabled, whether or not the
+SMTP client will send the QUIT command before it has received the
+server's END-OF-DATA reply.
+.PP
+Specify one of the following:
+.IP "\fBalways\fR"
+Always pipeline the END-OF-DATA and
+QUIT commands.  With servers or firewalls that mis-implement
+END-OF-DATA + QUIT pipelining, mail will be delivered repeatedly
+until it expires in the queue.
+.IP "\fBnever\fR"
+Wait for the server's END-OF-DATA reply
+before sending the QUIT command. This avoids repeated delivery
+attempts with servers and firewalls that mis-implement END-OF-DATA
++ QUIT pipelining, at the cost of a small performance loss with
+sites that correctly implement SMTP.
+.IP "\fBnewmail\fR"
+Pipeline the END-OF-DATA and QUIT
+commands only when mail is newer than $minimal_backoff_time.  This
+limits the number of repeated deliveries with servers and firewalls
+that mis-implement END-OF-DATA + QUIT pipelining, while avoiding
+the performance loss associated with the "never" setting for normal
+deliveries.
+.PP
+Note: when smtp_fallback_relay is used, the "always" and "newmail"
+settings become identical in practice.
+.PP
+This feature is available in Postfix 2.3 and later.
 .SH smtp_pix_workaround_delay_time (default: 10s)
 How long the Postfix SMTP client pauses before sending
 ".<CR><LF>" in order to work around the PIX firewall

postfix/man/man8/smtp.8

@@ -165,6 +165,10 @@ Defer mail delivery when no MX record resolves to an IP address.
 .IP "\fBsmtp_line_length_limit (990)\fR"
 The maximal length of message header and body lines that Postfix
 will send via SMTP.
+.IP "\fBsmtp_pipeline_dot_quit (never)\fR"
+When ESMTP command pipelining is enabled, whether or not the
+SMTP client will send the QUIT command before it has received the
+server's END-OF-DATA reply.
 .IP "\fBsmtp_pix_workaround_delay_time (10s)\fR"
 How long the Postfix SMTP client pauses before sending
 ".<CR><LF>" in order to work around the PIX firewall
@@ -190,9 +194,9 @@ again later).
 Available in Postfix version 2.2 and later:
 .IP "\fBsmtp_discard_ehlo_keyword_address_maps (empty)\fR"
 Lookup tables, indexed by the remote SMTP server address, with
-case insensitive lists of EHLO keywords (pipelining, starttls,
+case insensitive lists of EHLO keywords (pipelining, starttls, auth,
-auth, etc.) that the SMTP client will ignore in the EHLO response
+etc.) that the SMTP client will ignore in the EHLO response from a
-from a remote SMTP server.
+remote SMTP server.
 .IP "\fBsmtp_discard_ehlo_keywords (empty)\fR"
 A case insensitive list of EHLO keywords (pipelining, starttls,
 auth, etc.) that the SMTP client will ignore in the EHLO response

postfix/mantools/postlink

@@ -387,6 +387,7 @@ while (<>) {
     s;\bsmtp_mx_session_limit\b;<a href="postconf.5.html#smtp_mx_session_limit">$&</a>;g;
     s;\bsmtp_never_send_ehlo\b;<a href="postconf.5.html#smtp_never_send_ehlo">$&</a>;g;
     s;\bsmtp_sender_depen[-</bB>]*\n*[ <bB>]*dent_authentication\b;<a href="postconf.5.html#smtp_sender_dependent_authentication">$&</a>;g;
+    s;\bsmtp_pipeline_dot_quit\b;<a href="postconf.5.html#smtp_pipeline_dot_quit">$&</a>;g;
     s;\bsmtp_pix_workaround_delay_time\b;<a href="postconf.5.html#smtp_pix_workaround_delay_time">$&</a>;g;
     s;\bsmtp_pix_workaround_threshold_time\b;<a href="postconf.5.html#smtp_pix_workaround_threshold_time">$&</a>;g;
     s;\bsmtp_quit_timeout\b;<a href="postconf.5.html#smtp_quit_timeout">$&</a>;g;

postfix/proto/postconf.proto

@@ -8837,7 +8837,7 @@ case insensitive lists of LHLO keywords (pipelining, starttls,
 auth, etc.) that the LMTP client will ignore in the LHLO response
 from a remote LMTP server. See lmtp_discard_lhlo_keywords for
 details. The table is not indexed by hostname for consistency with
-smtpd_discard_ehlo_keyword_address_map </p>
+smtpd_discard_ehlo_keyword_address_maps. </p>
 
 <p> This feature is available in Postfix 2.3 and later. </p>
 
@@ -9125,3 +9125,43 @@ is rejected by the <b>reject_plaintext_session</b> restriction.
 rejecting the address as invalid.  </p>
 
 <p> This feature is available in Postfix 2.3 and later.
+
+%PARAM smtp_pipeline_dot_quit never
+
+<p> When ESMTP command pipelining is enabled, whether or not the
+SMTP client will send the QUIT command before it has received the
+server's END-OF-DATA reply. </p>
+
+<p> Specify one of the following: </p>
+
+<dl>
+
+<dt> <b>always</b> </dt> <dd> Always pipeline the END-OF-DATA and
+QUIT commands.  With servers or firewalls that mis-implement
+END-OF-DATA + QUIT pipelining, mail will be delivered repeatedly
+until it expires in the queue.  </dd>
+
+<dt> <b>never</b> </dt> <dd> Wait for the server's END-OF-DATA reply
+before sending the QUIT command. This avoids repeated delivery
+attempts with servers and firewalls that mis-implement END-OF-DATA
++ QUIT pipelining, at the cost of a small performance loss with
+sites that correctly implement SMTP. </dd>
+
+<dt> <b>newmail</b> </dt> <dd> Pipeline the END-OF-DATA and QUIT
+commands only when mail is newer than $minimal_backoff_time.  This
+limits the number of repeated deliveries with servers and firewalls
+that mis-implement END-OF-DATA + QUIT pipelining, while avoiding
+the performance loss associated with the "never" setting for normal
+deliveries.  </dd>
+
+</dl>
+
+<p> Note: when smtp_fallback_relay is used, the "always" and "newmail"
+settings become identical in practice. </p>
+
+<p> This feature is available in Postfix 2.3 and later. </p>
+
+%PARAM lmtp_pipeline_dot_quit never
+
+<p> The LMTP-specific version of the smtp_pipeline_dot_quit
+configuration parameter.  See there for details. </p>

postfix/src/global/mail_params.h

@@ -1006,6 +1006,16 @@ extern int var_smtp_pix_thresh;
 #define DEF_LMTP_PIX_DELAY	"10s"
 extern int var_smtp_pix_delay;
 
+#define SMTP_PIPE_DOT_QUIT_NEVER	"never"
+#define SMTP_PIPE_DOT_QUIT_NEWMAIL	"newmail"
+#define SMTP_PIPE_DOT_QUIT_ALWAYS	"always"
+
+#define VAR_SMTP_PIPE_DOT_QUIT	"smtp_pipeline_dot_quit"
+#define DEF_SMTP_PIPE_DOT_QUIT	SMTP_PIPE_DOT_QUIT_NEVER
+#define VAR_LMTP_PIPE_DOT_QUIT	"lmtp_pipeline_dot_quit"
+#define DEF_LMTP_PIPE_DOT_QUIT	SMTP_PIPE_DOT_QUIT_NEVER
+extern char *var_smtp_pipe_dot_quit;
+
 #define VAR_SMTP_DEFER_MXADDR	"smtp_defer_if_no_mx_address_found"
 #define DEF_SMTP_DEFER_MXADDR	0
 #define VAR_LMTP_DEFER_MXADDR	"lmtp_defer_if_no_mx_address_found"

postfix/src/global/mail_version.h

@@ -20,7 +20,7 @@
   * Patches change both the patchlevel and the release date. Snapshots have no
   * patchlevel; they change the release date only.
   */
-#define MAIL_RELEASE_DATE	"20051227"
+#define MAIL_RELEASE_DATE	"20051228"
 #define MAIL_VERSION_NUMBER	"2.3"
 
 #ifdef SNAPSHOT

postfix/src/smtp/lmtp_params.c

@@ -22,6 +22,7 @@
 	VAR_PROP_EXTENSION, DEF_PROP_EXTENSION, &var_prop_extension, 0, 0,
 	VAR_LMTP_GENERIC_MAPS, DEF_LMTP_GENERIC_MAPS, &var_smtp_generic_maps, 0, 0,
 	VAR_LMTP_TCP_PORT, DEF_LMTP_TCP_PORT, &var_lmtp_tcp_port, 0, 0,
+	VAR_LMTP_PIPE_DOT_QUIT, DEF_LMTP_PIPE_DOT_QUIT, &var_smtp_pipe_dot_quit, 1, 0,
 	0,
     };
     static CONFIG_TIME_TABLE lmtp_time_table[] = {
@@ -43,6 +44,7 @@
 	VAR_LMTP_STARTTLS_TMOUT, DEF_LMTP_STARTTLS_TMOUT, &var_smtp_starttls_tmout, 1, 0,
 #endif
 	VAR_SCACHE_PROTO_TMOUT, DEF_SCACHE_PROTO_TMOUT, &var_scache_proto_tmout, 1, 0,
+	VAR_MIN_BACKOFF_TIME, DEF_MIN_BACKOFF_TIME, &var_min_backoff_time, 1, 0,
 	0,
     };
     static CONFIG_INT_TABLE lmtp_int_table[] = {

postfix/src/smtp/smtp.c

@@ -143,6 +143,10 @@
 /* .IP "\fBsmtp_line_length_limit (990)\fR"
 /*	The maximal length of message header and body lines that Postfix
 /*	will send via SMTP.
+/* .IP "\fBsmtp_pipeline_dot_quit (never)\fR"
+/*	When ESMTP command pipelining is enabled, whether or not the
+/*	SMTP client will send the QUIT command before it has received the
+/*	server's END-OF-DATA reply.
 /* .IP "\fBsmtp_pix_workaround_delay_time (10s)\fR"
 /*	How long the Postfix SMTP client pauses before sending
 /*	".<CR><LF>" in order to work around the PIX firewall
@@ -168,9 +172,9 @@
 /*	Available in Postfix version 2.2 and later:
 /* .IP "\fBsmtp_discard_ehlo_keyword_address_maps (empty)\fR"
 /*	Lookup tables, indexed by the remote SMTP server address, with
-/*	case insensitive lists of EHLO keywords (pipelining, starttls,
+/*	case insensitive lists of EHLO keywords (pipelining, starttls, auth,
-/*	auth, etc.) that the SMTP client will ignore in the EHLO response
+/*	etc.) that the SMTP client will ignore in the EHLO response from a
-/*	from a remote SMTP server.
+/*	remote SMTP server.
 /* .IP "\fBsmtp_discard_ehlo_keywords (empty)\fR"
 /*	A case insensitive list of EHLO keywords (pipelining, starttls,
 /*	auth, etc.) that the SMTP client will ignore in the EHLO response
@@ -526,6 +530,7 @@
 #include <msg.h>
 #include <mymalloc.h>
 #include <name_mask.h>
+#include <name_code.h>
 
 /* Global library. */
 
@@ -617,6 +622,8 @@ char   *var_prop_extension;
 bool    var_smtp_sender_auth;
 char   *var_lmtp_tcp_port;
 int     var_scache_proto_tmout;
+char   *var_smtp_pipe_dot_quit;
+int     var_min_backoff_time;
 
  /*
   * Global variables. smtp_errno is set by the address lookup routines and by
@@ -629,6 +636,7 @@ SCACHE *smtp_scache;
 MAPS   *smtp_ehlo_dis_maps;
 MAPS   *smtp_generic_maps;
 int     smtp_ext_prop_mask;
+int     smtp_pipe_dot_quit;
 
 #ifdef USE_TLS
 
@@ -722,6 +730,12 @@ static void post_init(char *unused_name, char **unused_argv)
 	SMTP_HOST_LOOKUP_NATIVE, SMTP_HOST_FLAG_NATIVE,
 	0,
     };
+    static NAME_CODE pipe_dot_quit_codes[] = {
+	SMTP_PIPE_DOT_QUIT_NEVER, SMTP_PIPE_DOT_QUIT_CODE_NEVER,
+	SMTP_PIPE_DOT_QUIT_NEWMAIL, SMTP_PIPE_DOT_QUIT_CODE_NEWMAIL,
+	SMTP_PIPE_DOT_QUIT_ALWAYS, SMTP_PIPE_DOT_QUIT_CODE_ALWAYS,
+	0, SMTP_PIPE_DOT_QUIT_CODE_ERROR,
+    };
 
     /*
      * Select hostname lookup mechanisms.
@@ -748,6 +762,16 @@ static void post_init(char *unused_name, char **unused_argv)
 					 var_ipc_idle_limit,
 					 var_ipc_ttl_limit);
 #endif
+
+    /*
+     * Initialize dot-quit pipelining workaround.
+     */
+    smtp_pipe_dot_quit = name_code(pipe_dot_quit_codes,
+				   NAME_CODE_FLAG_NONE,
+				   var_smtp_pipe_dot_quit);
+    if (smtp_pipe_dot_quit == SMTP_PIPE_DOT_QUIT_CODE_ERROR)
+	msg_fatal("unknown %s value: %s", VAR_SMTP_PIPE_DOT_QUIT,
+		  var_smtp_pipe_dot_quit);
 }
 
 /* pre_init - pre-jail initialization */

postfix/src/smtp/smtp.h

@@ -166,6 +166,13 @@ extern SSL_CTX *smtp_tls_ctx;		/* client-side TLS engine */
 
 #endif
 
+#define SMTP_PIPE_DOT_QUIT_CODE_ERROR	0
+#define SMTP_PIPE_DOT_QUIT_CODE_NEVER	1
+#define SMTP_PIPE_DOT_QUIT_CODE_NEWMAIL	2
+#define SMTP_PIPE_DOT_QUIT_CODE_ALWAYS	3
+
+extern int smtp_pipe_dot_quit;
+
  /*
   * smtp_session.c
   */

postfix/src/smtp/smtp_chat.c

@@ -289,7 +289,7 @@ SMTP_RESP *smtp_chat_resp(SMTP_SESSION *session)
 	    msg_warn("non-%s response from %s: %s",
 		     (session->state->misc_flags &
 		      SMTP_MISC_FLAG_USE_LMTP) ? "LMTP" : "ESMTP",
-		     session->namaddr, STR(session->buffer));
+		     session->namaddrport, STR(session->buffer));
 	    vstream_longjmp(session->stream, SMTP_ERR_PROTO);
 	}
     }

postfix/src/smtp/smtp_params.c

@@ -23,6 +23,7 @@
 	VAR_PROP_EXTENSION, DEF_PROP_EXTENSION, &var_prop_extension, 0, 0,
 	VAR_SMTP_GENERIC_MAPS, DEF_SMTP_GENERIC_MAPS, &var_smtp_generic_maps, 0, 0,
 	VAR_LMTP_TCP_PORT, DEF_LMTP_TCP_PORT, &var_lmtp_tcp_port, 0, 0,
+	VAR_SMTP_PIPE_DOT_QUIT, DEF_SMTP_PIPE_DOT_QUIT, &var_smtp_pipe_dot_quit, 1, 0,
 	0,
     };
     static CONFIG_TIME_TABLE smtp_time_table[] = {
@@ -44,6 +45,7 @@
 	VAR_SMTP_STARTTLS_TMOUT, DEF_SMTP_STARTTLS_TMOUT, &var_smtp_starttls_tmout, 1, 0,
 #endif
 	VAR_SCACHE_PROTO_TMOUT, DEF_SCACHE_PROTO_TMOUT, &var_scache_proto_tmout, 1, 0,
+	VAR_MIN_BACKOFF_TIME, DEF_MIN_BACKOFF_TIME, &var_min_backoff_time, 1, 0,
 	0,
     };
     static CONFIG_INT_TABLE smtp_int_table[] = {

postfix/src/smtp/smtp_proto.c

@@ -926,8 +926,16 @@ static int smtp_loop(SMTP_STATE *state, NOCLOBBER int send_state,
 #define SENDER_IS_AHEAD \
 	(recv_state < send_state || recv_rcpt != send_rcpt)
 
+#define DONT_PIPELINE_DOT_QUIT \
+	(smtp_pipe_dot_quit == SMTP_PIPE_DOT_QUIT_CODE_NEVER \
+	 || (smtp_pipe_dot_quit == SMTP_PIPE_DOT_QUIT_CODE_NEWMAIL \
+	     && request->msg_stats.incoming_arrival.tv_sec \
+		< vstream_ftime(session->stream) - var_min_backoff_time))
+
 #define SENDER_IN_WAIT_STATE \
-	(send_state == SMTP_STATE_DOT || send_state == SMTP_STATE_LAST)
+	(send_state == SMTP_STATE_DOT || send_state == SMTP_STATE_LAST \
+	 || (recv_state == SMTP_STATE_DOT && send_state == SMTP_STATE_QUIT \
+	     && DONT_PIPELINE_DOT_QUIT))
 
 #define SENDING_MAIL \
 	(recv_state <= SMTP_STATE_DOT)
@@ -1144,7 +1152,8 @@ static int smtp_loop(SMTP_STATE *state, NOCLOBBER int send_state,
 	    break;
 
 	    /*
-	     * Build the "." command before we have seen the DATA response.
+	     * Build the "." command after we have seen the DATA response
+	     * (DATA is a protocol synchronization point).
 	     * 
 	     * Changing the connection caching state here is safe because it
 	     * affects none of the not-yet processed replies to