PIPE_CONNECT: fix feature-cache refresh

[exim.git] / src / src / transports / smtp.c

/*************************************************
*     Exim - an Internet mail transport agent    *
*************************************************/

/* Copyright (c) University of Cambridge 1995 - 2018 */
/* See the file NOTICE for conditions of use and distribution. */

#include "../exim.h"
#include "smtp.h"


/* Options specific to the smtp transport. This transport also supports LMTP
over TCP/IP. The options must be in alphabetic order (note that "_" comes
before the lower case letters). Some live in the transport_instance block so as
to be publicly visible; these are flagged with opt_public. */

optionlist smtp_transport_options[] = {
  { "*expand_multi_domain",             opt_stringptr | opt_hidden | opt_public,
      (void *)offsetof(transport_instance, expand_multi_domain) },
  { "*expand_retry_include_ip_address", opt_stringptr | opt_hidden,
       (void *)(offsetof(smtp_transport_options_block, expand_retry_include_ip_address)) },

  { "address_retry_include_sender", opt_bool,
      (void *)offsetof(smtp_transport_options_block, address_retry_include_sender) },
  { "allow_localhost",      opt_bool,
      (void *)offsetof(smtp_transport_options_block, allow_localhost) },
#ifdef EXPERIMENTAL_ARC
  { "arc_sign", opt_stringptr,
      (void *)offsetof(smtp_transport_options_block, arc_sign) },
#endif
  { "authenticated_sender", opt_stringptr,
      (void *)offsetof(smtp_transport_options_block, authenticated_sender) },
  { "authenticated_sender_force", opt_bool,
      (void *)offsetof(smtp_transport_options_block, authenticated_sender_force) },
  { "command_timeout",      opt_time,
      (void *)offsetof(smtp_transport_options_block, command_timeout) },
  { "connect_timeout",      opt_time,
      (void *)offsetof(smtp_transport_options_block, connect_timeout) },
  { "connection_max_messages", opt_int | opt_public,
      (void *)offsetof(transport_instance, connection_max_messages) },
# ifdef SUPPORT_DANE
  { "dane_require_tls_ciphers", opt_stringptr,
      (void *)offsetof(smtp_transport_options_block, dane_require_tls_ciphers) },
# endif
  { "data_timeout",         opt_time,
      (void *)offsetof(smtp_transport_options_block, data_timeout) },
  { "delay_after_cutoff", opt_bool,
      (void *)offsetof(smtp_transport_options_block, delay_after_cutoff) },
#ifndef DISABLE_DKIM
  { "dkim_canon", opt_stringptr,
      (void *)offsetof(smtp_transport_options_block, dkim.dkim_canon) },
  { "dkim_domain", opt_stringptr,
      (void *)offsetof(smtp_transport_options_block, dkim.dkim_domain) },
  { "dkim_hash", opt_stringptr,
      (void *)offsetof(smtp_transport_options_block, dkim.dkim_hash) },
  { "dkim_identity", opt_stringptr,
      (void *)offsetof(smtp_transport_options_block, dkim.dkim_identity) },
  { "dkim_private_key", opt_stringptr,
      (void *)offsetof(smtp_transport_options_block, dkim.dkim_private_key) },
  { "dkim_selector", opt_stringptr,
      (void *)offsetof(smtp_transport_options_block, dkim.dkim_selector) },
  { "dkim_sign_headers", opt_stringptr,
      (void *)offsetof(smtp_transport_options_block, dkim.dkim_sign_headers) },
  { "dkim_strict", opt_stringptr,
      (void *)offsetof(smtp_transport_options_block, dkim.dkim_strict) },
  { "dkim_timestamps", opt_stringptr,
      (void *)offsetof(smtp_transport_options_block, dkim.dkim_timestamps) },
#endif
  { "dns_qualify_single",   opt_bool,
      (void *)offsetof(smtp_transport_options_block, dns_qualify_single) },
  { "dns_search_parents",   opt_bool,
      (void *)offsetof(smtp_transport_options_block, dns_search_parents) },
  { "dnssec_request_domains", opt_stringptr,
      (void *)offsetof(smtp_transport_options_block, dnssec.request) },
  { "dnssec_require_domains", opt_stringptr,
      (void *)offsetof(smtp_transport_options_block, dnssec.require) },
  { "dscp",                 opt_stringptr,
      (void *)offsetof(smtp_transport_options_block, dscp) },
  { "fallback_hosts",       opt_stringptr,
      (void *)offsetof(smtp_transport_options_block, fallback_hosts) },
  { "final_timeout",        opt_time,
      (void *)offsetof(smtp_transport_options_block, final_timeout) },
  { "gethostbyname",        opt_bool,
      (void *)offsetof(smtp_transport_options_block, gethostbyname) },
  { "helo_data",            opt_stringptr,
      (void *)offsetof(smtp_transport_options_block, helo_data) },
  { "hosts",                opt_stringptr,
      (void *)offsetof(smtp_transport_options_block, hosts) },
  { "hosts_avoid_esmtp",    opt_stringptr,
      (void *)offsetof(smtp_transport_options_block, hosts_avoid_esmtp) },
  { "hosts_avoid_pipelining", opt_stringptr,
      (void *)offsetof(smtp_transport_options_block, hosts_avoid_pipelining) },
#ifdef SUPPORT_TLS
  { "hosts_avoid_tls",      opt_stringptr,
      (void *)offsetof(smtp_transport_options_block, hosts_avoid_tls) },
#endif
  { "hosts_max_try",        opt_int,
      (void *)offsetof(smtp_transport_options_block, hosts_max_try) },
  { "hosts_max_try_hardlimit", opt_int,
      (void *)offsetof(smtp_transport_options_block, hosts_max_try_hardlimit) },
#ifdef SUPPORT_TLS
  { "hosts_nopass_tls",     opt_stringptr,
      (void *)offsetof(smtp_transport_options_block, hosts_nopass_tls) },
  { "hosts_noproxy_tls",    opt_stringptr,
      (void *)offsetof(smtp_transport_options_block, hosts_noproxy_tls) },
#endif
  { "hosts_override",       opt_bool,
      (void *)offsetof(smtp_transport_options_block, hosts_override) },
#ifdef EXPERIMENTAL_PIPE_CONNECT
  { "hosts_pipe_connect",   opt_stringptr,
      (void *)offsetof(smtp_transport_options_block, hosts_pipe_connect) },
#endif
  { "hosts_randomize",      opt_bool,
      (void *)offsetof(smtp_transport_options_block, hosts_randomize) },
#if defined(SUPPORT_TLS) && !defined(DISABLE_OCSP)
  { "hosts_request_ocsp",   opt_stringptr,
      (void *)offsetof(smtp_transport_options_block, hosts_request_ocsp) },
#endif
  { "hosts_require_auth",   opt_stringptr,
      (void *)offsetof(smtp_transport_options_block, hosts_require_auth) },
#ifdef SUPPORT_TLS
# ifdef SUPPORT_DANE
  { "hosts_require_dane",   opt_stringptr,
      (void *)offsetof(smtp_transport_options_block, hosts_require_dane) },
# endif
# ifndef DISABLE_OCSP
  { "hosts_require_ocsp",   opt_stringptr,
      (void *)offsetof(smtp_transport_options_block, hosts_require_ocsp) },
# endif
  { "hosts_require_tls",    opt_stringptr,
      (void *)offsetof(smtp_transport_options_block, hosts_require_tls) },
#endif
  { "hosts_try_auth",       opt_stringptr,
      (void *)offsetof(smtp_transport_options_block, hosts_try_auth) },
  { "hosts_try_chunking",   opt_stringptr,
      (void *)offsetof(smtp_transport_options_block, hosts_try_chunking) },
#if defined(SUPPORT_TLS) && defined(SUPPORT_DANE)
  { "hosts_try_dane",       opt_stringptr,
      (void *)offsetof(smtp_transport_options_block, hosts_try_dane) },
#endif
  { "hosts_try_fastopen",   opt_stringptr,
      (void *)offsetof(smtp_transport_options_block, hosts_try_fastopen) },
#ifndef DISABLE_PRDR
  { "hosts_try_prdr",       opt_stringptr,
      (void *)offsetof(smtp_transport_options_block, hosts_try_prdr) },
#endif
#ifdef SUPPORT_TLS
  { "hosts_verify_avoid_tls", opt_stringptr,
      (void *)offsetof(smtp_transport_options_block, hosts_verify_avoid_tls) },
#endif
  { "interface",            opt_stringptr,
      (void *)offsetof(smtp_transport_options_block, interface) },
  { "keepalive",            opt_bool,
      (void *)offsetof(smtp_transport_options_block, keepalive) },
  { "lmtp_ignore_quota",    opt_bool,
      (void *)offsetof(smtp_transport_options_block, lmtp_ignore_quota) },
  { "max_rcpt",             opt_int | opt_public,
      (void *)offsetof(transport_instance, max_addresses) },
  { "multi_domain",         opt_expand_bool | opt_public,
      (void *)offsetof(transport_instance, multi_domain) },
  { "port",                 opt_stringptr,
      (void *)offsetof(smtp_transport_options_block, port) },
  { "protocol",             opt_stringptr,
      (void *)offsetof(smtp_transport_options_block, protocol) },
  { "retry_include_ip_address", opt_expand_bool,
      (void *)offsetof(smtp_transport_options_block, retry_include_ip_address) },
  { "serialize_hosts",      opt_stringptr,
      (void *)offsetof(smtp_transport_options_block, serialize_hosts) },
  { "size_addition",        opt_int,
      (void *)offsetof(smtp_transport_options_block, size_addition) },
#ifdef SUPPORT_SOCKS
  { "socks_proxy",          opt_stringptr,
      (void *)offsetof(smtp_transport_options_block, socks_proxy) },
#endif
#ifdef SUPPORT_TLS
  { "tls_certificate",      opt_stringptr,
      (void *)offsetof(smtp_transport_options_block, tls_certificate) },
  { "tls_crl",              opt_stringptr,
      (void *)offsetof(smtp_transport_options_block, tls_crl) },
  { "tls_dh_min_bits",      opt_int,
      (void *)offsetof(smtp_transport_options_block, tls_dh_min_bits) },
  { "tls_privatekey",       opt_stringptr,
      (void *)offsetof(smtp_transport_options_block, tls_privatekey) },
  { "tls_require_ciphers",  opt_stringptr,
      (void *)offsetof(smtp_transport_options_block, tls_require_ciphers) },
  { "tls_sni",              opt_stringptr,
      (void *)offsetof(smtp_transport_options_block, tls_sni) },
  { "tls_tempfail_tryclear", opt_bool,
      (void *)offsetof(smtp_transport_options_block, tls_tempfail_tryclear) },
  { "tls_try_verify_hosts", opt_stringptr,
      (void *)offsetof(smtp_transport_options_block, tls_try_verify_hosts) },
  { "tls_verify_cert_hostnames", opt_stringptr,
      (void *)offsetof(smtp_transport_options_block,tls_verify_cert_hostnames)},
  { "tls_verify_certificates", opt_stringptr,
      (void *)offsetof(smtp_transport_options_block, tls_verify_certificates) },
  { "tls_verify_hosts",     opt_stringptr,
      (void *)offsetof(smtp_transport_options_block, tls_verify_hosts) },
#endif
#ifdef SUPPORT_I18N
  { "utf8_downconvert",	    opt_stringptr,
      (void *)offsetof(smtp_transport_options_block, utf8_downconvert) },
#endif
};

/* Size of the options list. An extern variable has to be used so that its
address can appear in the tables drtables.c. */

int smtp_transport_options_count = nelem(smtp_transport_options);


#ifdef MACRO_PREDEF

/* Dummy values */
smtp_transport_options_block smtp_transport_option_defaults = {0};
void smtp_transport_init(transport_instance *tblock) {}
BOOL smtp_transport_entry(transport_instance *tblock, address_item *addr) {return FALSE;}
void smtp_transport_closedown(transport_instance *tblock) {}

#else   /*!MACRO_PREDEF*/


/* Default private options block for the smtp transport. */

smtp_transport_options_block smtp_transport_option_defaults = {
  .hosts =			NULL,
  .fallback_hosts =		NULL,
  .hostlist =			NULL,
  .fallback_hostlist =		NULL,
  .helo_data =			US"$primary_hostname",
  .interface =			NULL,
  .port =			NULL,
  .protocol =			US"smtp",
  .dscp =			NULL,
  .serialize_hosts =		NULL,
  .hosts_try_auth =		NULL,
  .hosts_require_auth =		NULL,
  .hosts_try_chunking =		US"*",
#ifdef SUPPORT_DANE
  .hosts_try_dane =		NULL,
  .hosts_require_dane =		NULL,
  .dane_require_tls_ciphers =	NULL,
#endif
  .hosts_try_fastopen =		NULL,
#ifndef DISABLE_PRDR
  .hosts_try_prdr =		US"*",
#endif
#ifndef DISABLE_OCSP
  .hosts_request_ocsp =		US"*",               /* hosts_request_ocsp (except under DANE; tls_client_start()) */
  .hosts_require_ocsp =		NULL,
#endif
  .hosts_require_tls =		NULL,
  .hosts_avoid_tls =		NULL,
  .hosts_verify_avoid_tls =	NULL,
  .hosts_avoid_pipelining =	NULL,
#ifdef EXPERIMENTAL_PIPE_CONNECT
  .hosts_pipe_connect =		NULL,
#endif
  .hosts_avoid_esmtp =		NULL,
#ifdef SUPPORT_TLS
  .hosts_nopass_tls =		NULL,
  .hosts_noproxy_tls =		US"*",
#endif
  .command_timeout =		5*60,
  .connect_timeout =		5*60,
  .data_timeout =		5*60,
  .final_timeout =		10*60,
  .size_addition =		1024,
  .hosts_max_try =		5,
  .hosts_max_try_hardlimit =	50,
  .address_retry_include_sender = TRUE,
  .allow_localhost =		FALSE,
  .authenticated_sender_force =	FALSE,
  .gethostbyname =		FALSE,
  .dns_qualify_single =		TRUE,
  .dns_search_parents =		FALSE,
  .dnssec = { .request=NULL, .require=NULL },
  .delay_after_cutoff =		TRUE,
  .hosts_override =		FALSE,
  .hosts_randomize =		FALSE,
  .keepalive =			TRUE,
  .lmtp_ignore_quota =		FALSE,
  .expand_retry_include_ip_address =	NULL,
  .retry_include_ip_address =	TRUE,
#ifdef SUPPORT_SOCKS
  .socks_proxy =		NULL,
#endif
#ifdef SUPPORT_TLS
  .tls_certificate =		NULL,
  .tls_crl =			NULL,
  .tls_privatekey =		NULL,
  .tls_require_ciphers =	NULL,
  .tls_sni =			NULL,
  .tls_verify_certificates =	US"system",
  .tls_dh_min_bits =		EXIM_CLIENT_DH_DEFAULT_MIN_BITS,
  .tls_tempfail_tryclear =	TRUE,
  .tls_verify_hosts =		NULL,
  .tls_try_verify_hosts =	US"*",
  .tls_verify_cert_hostnames =	US"*",
#endif
#ifdef SUPPORT_I18N
  .utf8_downconvert =		NULL,
#endif
#ifndef DISABLE_DKIM
 .dkim =
   {.dkim_domain =		NULL,
    .dkim_identity =		NULL,
    .dkim_private_key =		NULL,
    .dkim_selector =		NULL,
    .dkim_canon =		NULL,
    .dkim_sign_headers =	NULL,
    .dkim_strict =		NULL,
    .dkim_hash =		US"sha256",
    .dkim_timestamps =		NULL,
    .dot_stuffed =		FALSE,
    .force_bodyhash =		FALSE,
# ifdef EXPERIMENTAL_ARC
    .arc_signspec =		NULL,
# endif
    },
# ifdef EXPERIMENTAL_ARC
  .arc_sign =			NULL,
# endif
#endif
};

/* some DSN flags for use later */

static int     rf_list[] = {rf_notify_never, rf_notify_success,
                            rf_notify_failure, rf_notify_delay };

static uschar *rf_names[] = { US"NEVER", US"SUCCESS", US"FAILURE", US"DELAY" };



/* Local statics */

static uschar *smtp_command;		/* Points to last cmd for error messages */
static uschar *mail_command;		/* Points to MAIL cmd for error messages */
static uschar *data_command = US"";	/* Points to DATA cmd for error messages */
static BOOL    update_waiting;		/* TRUE to update the "wait" database */

/*XXX move to smtp_context */
static BOOL    pipelining_active;	/* current transaction is in pipe mode */


static unsigned ehlo_response(uschar * buf, unsigned checks);


/*************************************************
*             Setup entry point                  *
*************************************************/

/* This function is called when the transport is about to be used,
but before running it in a sub-process. It is used for two things:

  (1) To set the fallback host list in addresses, when delivering.
  (2) To pass back the interface, port, protocol, and other options, for use
      during callout verification.

Arguments:
  tblock    pointer to the transport instance block
  addrlist  list of addresses about to be transported
  tf        if not NULL, pointer to block in which to return options
  uid       the uid that will be set (not used)
  gid       the gid that will be set (not used)
  errmsg    place for error message (not used)

Returns:  OK always (FAIL, DEFER not used)
*/

static int
smtp_transport_setup(transport_instance *tblock, address_item *addrlist,
  transport_feedback *tf, uid_t uid, gid_t gid, uschar **errmsg)
{
smtp_transport_options_block *ob = SOB tblock->options_block;

errmsg = errmsg;    /* Keep picky compilers happy */
uid = uid;
gid = gid;

/* Pass back options if required. This interface is getting very messy. */

if (tf)
  {
  tf->interface = ob->interface;
  tf->port = ob->port;
  tf->protocol = ob->protocol;
  tf->hosts = ob->hosts;
  tf->hosts_override = ob->hosts_override;
  tf->hosts_randomize = ob->hosts_randomize;
  tf->gethostbyname = ob->gethostbyname;
  tf->qualify_single = ob->dns_qualify_single;
  tf->search_parents = ob->dns_search_parents;
  tf->helo_data = ob->helo_data;
  }

/* Set the fallback host list for all the addresses that don't have fallback
host lists, provided that the local host wasn't present in the original host
list. */

if (!testflag(addrlist, af_local_host_removed))
  for (; addrlist; addrlist = addrlist->next)
    if (!addrlist->fallback_hosts) addrlist->fallback_hosts = ob->fallback_hostlist;

return OK;
}



/*************************************************
*          Initialization entry point            *
*************************************************/

/* Called for each instance, after its options have been read, to
enable consistency checks to be done, or anything else that needs
to be set up.

Argument:   pointer to the transport instance block
Returns:    nothing
*/

void
smtp_transport_init(transport_instance *tblock)
{
smtp_transport_options_block *ob = SOB tblock->options_block;

/* Retry_use_local_part defaults FALSE if unset */

if (tblock->retry_use_local_part == TRUE_UNSET)
  tblock->retry_use_local_part = FALSE;

/* Set the default port according to the protocol */

if (!ob->port)
  ob->port = strcmpic(ob->protocol, US"lmtp") == 0
  ? US"lmtp"
  : strcmpic(ob->protocol, US"smtps") == 0
  ? US"smtps" : US"smtp";

/* Set up the setup entry point, to be called before subprocesses for this
transport. */

tblock->setup = smtp_transport_setup;

/* Complain if any of the timeouts are zero. */

if (ob->command_timeout <= 0 || ob->data_timeout <= 0 ||
    ob->final_timeout <= 0)
  log_write(0, LOG_PANIC_DIE|LOG_CONFIG,
    "command, data, or final timeout value is zero for %s transport",
      tblock->name);

/* If hosts_override is set and there are local hosts, set the global
flag that stops verify from showing router hosts. */

if (ob->hosts_override && ob->hosts != NULL) tblock->overrides_hosts = TRUE;

/* If there are any fallback hosts listed, build a chain of host items
for them, but do not do any lookups at this time. */

host_build_hostlist(&(ob->fallback_hostlist), ob->fallback_hosts, FALSE);
}





/*************************************************
*   Set delivery info into all active addresses  *
*************************************************/

/* Only addresses whose status is >= PENDING are relevant. A lesser
status means that an address is not currently being processed.

Arguments:
  addrlist       points to a chain of addresses
  errno_value    to put in each address's errno field
  msg            to put in each address's message field
  rc             to put in each address's transport_return field
  pass_message   if TRUE, set the "pass message" flag in the address
  host           if set, mark addrs as having used this host
  smtp_greeting  from peer
  helo_response  from peer

If errno_value has the special value ERRNO_CONNECTTIMEOUT, ETIMEDOUT is put in
the errno field, and RTEF_CTOUT is ORed into the more_errno field, to indicate
this particular type of timeout.

Returns:       nothing
*/

static void
set_errno(address_item *addrlist, int errno_value, uschar *msg, int rc,
  BOOL pass_message, host_item * host
#ifdef EXPERIMENTAL_DSN_INFO
  , const uschar * smtp_greeting, const uschar * helo_response
#endif
  )
{
address_item *addr;
int orvalue = 0;
if (errno_value == ERRNO_CONNECTTIMEOUT)
  {
  errno_value = ETIMEDOUT;
  orvalue = RTEF_CTOUT;
  }
for (addr = addrlist; addr; addr = addr->next)
  if (addr->transport_return >= PENDING)
    {
    addr->basic_errno = errno_value;
    addr->more_errno |= orvalue;
    if (msg)
      {
      addr->message = msg;
      if (pass_message) setflag(addr, af_pass_message);
      }
    addr->transport_return = rc;
    if (host)
      {
      addr->host_used = host;
#ifdef EXPERIMENTAL_DSN_INFO
      if (smtp_greeting)
	{uschar * s = Ustrchr(smtp_greeting, '\n'); if (s) *s = '\0';}
      addr->smtp_greeting = smtp_greeting;

      if (helo_response)
	{uschar * s = Ustrchr(helo_response, '\n'); if (s) *s = '\0';}
      addr->helo_response = helo_response;
#endif
      }
    }
}

static void
set_errno_nohost(address_item *addrlist, int errno_value, uschar *msg, int rc,
  BOOL pass_message)
{
set_errno(addrlist, errno_value, msg, rc, pass_message, NULL
#ifdef EXPERIMENTAL_DSN_INFO
	  , NULL, NULL
#endif
	  );
}


/*************************************************
*          Check an SMTP response                *
*************************************************/

/* This function is given an errno code and the SMTP response buffer
to analyse, together with the host identification for generating messages. It
sets an appropriate message and puts the first digit of the response code into
the yield variable. If no response was actually read, a suitable digit is
chosen.

Arguments:
  host           the current host, to get its name for messages
  errno_value    pointer to the errno value
  more_errno     from the top address for use with ERRNO_FILTER_FAIL
  buffer         the SMTP response buffer
  yield          where to put a one-digit SMTP response code
  message        where to put an error message
  pass_message   set TRUE if message is an SMTP response

Returns:         TRUE if an SMTP "QUIT" command should be sent, else FALSE
*/

static BOOL
check_response(host_item *host, int *errno_value, int more_errno,
  uschar *buffer, int *yield, uschar **message, BOOL *pass_message)
{
uschar * pl = pipelining_active ? US"pipelined " : US"";
const uschar * s;

*yield = '4';    /* Default setting is to give a temporary error */

switch(*errno_value)
  {
  case ETIMEDOUT:		/* Handle response timeout */
    *message = US string_sprintf("SMTP timeout after %s%s",
	pl, smtp_command);
    if (transport_count > 0)
      *message = US string_sprintf("%s (%d bytes written)", *message,
	transport_count);
    return FALSE;

  case ERRNO_SMTPFORMAT:	/* Handle malformed SMTP response */
    s = string_printing(buffer);
    while (isspace(*s)) s++;
    *message = *s == 0
      ? string_sprintf("Malformed SMTP reply (an empty line) "
	  "in response to %s%s", pl, smtp_command)
      : string_sprintf("Malformed SMTP reply in response to %s%s: %s",
	  pl, smtp_command, s);
    return FALSE;

  case ERRNO_FILTER_FAIL:	/* Handle a failed filter process error;
			  can't send QUIT as we mustn't end the DATA. */
    *message = string_sprintf("transport filter process failed (%d)%s",
      more_errno,
      more_errno == EX_EXECFAILED ? ": unable to execute command" : "");
    return FALSE;

  case ERRNO_CHHEADER_FAIL:	/* Handle a failed add_headers expansion;
			    can't send QUIT as we mustn't end the DATA. */
    *message =
      string_sprintf("failed to expand headers_add or headers_remove: %s",
	expand_string_message);
    return FALSE;

  case ERRNO_WRITEINCOMPLETE:	/* failure to write a complete data block */
    *message = string_sprintf("failed to write a data block");
    return FALSE;

#ifdef SUPPORT_I18N
  case ERRNO_UTF8_FWD: /* no advertised SMTPUTF8, for international message */
    *message = US"utf8 support required but not offered for forwarding";
    DEBUG(D_deliver|D_transport) debug_printf("%s\n", *message);
    return TRUE;
#endif
  }

/* Handle error responses from the remote mailer. */

if (buffer[0] != 0)
  {
  *message = string_sprintf("SMTP error from remote mail server after %s%s: "
    "%s", pl, smtp_command, s = string_printing(buffer));
  *pass_message = TRUE;
  *yield = buffer[0];
  return TRUE;
  }

/* No data was read. If there is no errno, this must be the EOF (i.e.
connection closed) case, which causes deferral. An explicit connection reset
error has the same effect. Otherwise, put the host's identity in the message,
leaving the errno value to be interpreted as well. In all cases, we have to
assume the connection is now dead. */

if (*errno_value == 0 || *errno_value == ECONNRESET)
  {
  *errno_value = ERRNO_SMTPCLOSED;
  *message = US string_sprintf("Remote host closed connection "
    "in response to %s%s", pl, smtp_command);
  }
else
  *message = US string_sprintf("%s [%s]", host->name, host->address);

return FALSE;
}



/*************************************************
*          Write error message to logs           *
*************************************************/

/* This writes to the main log and to the message log.

Arguments:
  host     the current host
  detail  the current message (addr_item->message)
  basic_errno the errno (addr_item->basic_errno)

Returns:   nothing
*/

static void
write_logs(const host_item *host, const uschar *suffix, int basic_errno)
{
gstring * message = LOGGING(outgoing_port)
  ? string_fmt_append(NULL, "H=%s [%s]:%d", host->name, host->address,
		    host->port == PORT_NONE ? 25 : host->port)
  : string_fmt_append(NULL, "H=%s [%s]", host->name, host->address);

if (suffix)
  {
  message = string_fmt_append(message, ": %s", suffix);
  if (basic_errno > 0)
    message = string_fmt_append(message, ": %s", strerror(basic_errno));
  }
else
  message = string_fmt_append(message, " %s", exim_errstr(basic_errno));

log_write(0, LOG_MAIN, "%s", string_from_gstring(message));
deliver_msglog("%s %s\n", tod_stamp(tod_log), message->s);
}

static void
msglog_line(host_item * host, uschar * message)
{
deliver_msglog("%s H=%s [%s] %s\n", tod_stamp(tod_log),
  host->name, host->address, message);
}



#ifndef DISABLE_EVENT
/*************************************************
*   Post-defer action                            *
*************************************************/

/* This expands an arbitrary per-transport string.
   It might, for example, be used to write to the database log.

Arguments:
  addr                  the address item containing error information
  host                  the current host

Returns:   nothing
*/

static void
deferred_event_raise(address_item *addr, host_item *host)
{
uschar * action = addr->transport->event_action;
const uschar * save_domain;
uschar * save_local;

if (!action)
  return;

save_domain = deliver_domain;
save_local = deliver_localpart;

/*XXX would ip & port already be set up? */
deliver_host_address = string_copy(host->address);
deliver_host_port =    host->port == PORT_NONE ? 25 : host->port;
event_defer_errno =    addr->basic_errno;

router_name =    addr->router->name;
transport_name = addr->transport->name;
deliver_domain = addr->domain;
deliver_localpart = addr->local_part;

(void) event_raise(action, US"msg:host:defer",
    addr->message
      ? addr->basic_errno > 0
	? string_sprintf("%s: %s", addr->message, strerror(addr->basic_errno))
	: string_copy(addr->message)
      : addr->basic_errno > 0
	? string_copy(US strerror(addr->basic_errno))
	: NULL);

deliver_localpart = save_local;
deliver_domain =    save_domain;
router_name = transport_name = NULL;
}
#endif

/*************************************************
*           Reap SMTP specific responses         *
*************************************************/
static int
smtp_discard_responses(smtp_context * sx, smtp_transport_options_block * ob,
  int count)
{
uschar flushbuffer[4096];

while (count-- > 0)
  {
  if (!smtp_read_response(sx, flushbuffer, sizeof(flushbuffer),
	     '2', ob->command_timeout)
      && (errno != 0 || flushbuffer[0] == 0))
    break;
  }
return count;
}


/* Return boolean success */

static BOOL
smtp_reap_banner(smtp_context * sx)
{
BOOL good_response = smtp_read_response(sx, sx->buffer, sizeof(sx->buffer),
  '2', (SOB sx->conn_args.ob)->command_timeout);
#ifdef EXPERIMENTAL_DSN_INFO
sx->smtp_greeting = string_copy(sx->buffer);
#endif
return good_response;
}

static BOOL
smtp_reap_ehlo(smtp_context * sx)
{
if (!smtp_read_response(sx, sx->buffer, sizeof(sx->buffer), '2',
       (SOB sx->conn_args.ob)->command_timeout))
  {
  if (errno != 0 || sx->buffer[0] == 0 || sx->lmtp)
    {
#ifdef EXPERIMENTAL_DSN_INFO
    sx->helo_response = string_copy(sx->buffer);
#endif
    return FALSE;
    }
  sx->esmtp = FALSE;
  }
#ifdef EXPERIMENTAL_DSN_INFO
sx->helo_response = string_copy(sx->buffer);
#endif
return TRUE;
}



#ifdef EXPERIMENTAL_PIPE_CONNECT
static uschar *
ehlo_cache_key(const smtp_context * sx)
{
host_item * host = sx->conn_args.host;
return Ustrchr(host->address, ':')
  ? string_sprintf("[%s]:%d.EHLO", host->address,
    host->port == PORT_NONE ? sx->port : host->port)
  : string_sprintf("%s:%d.EHLO", host->address,
    host->port == PORT_NONE ? sx->port : host->port);
}

static void
write_ehlo_cache_entry(const smtp_context * sx)
{
open_db dbblock, * dbm_file;

if ((dbm_file = dbfn_open(US"misc", O_RDWR, &dbblock, TRUE)))
  {
  uschar * ehlo_resp_key = ehlo_cache_key(sx);
  dbdata_ehlo_resp er = { .data = sx->ehlo_resp };

  HDEBUG(D_transport) debug_printf("writing clr %04x/%04x cry %04x/%04x\n",
    sx->ehlo_resp.cleartext_features, sx->ehlo_resp.cleartext_auths,
    sx->ehlo_resp.crypted_features, sx->ehlo_resp.crypted_auths);

  dbfn_write(dbm_file, ehlo_resp_key, &er, (int)sizeof(er));
  dbfn_close(dbm_file);
  }
}

static void
invalidate_ehlo_cache_entry(smtp_context * sx)
{
open_db dbblock, * dbm_file;

if (  sx->early_pipe_active
   && (dbm_file = dbfn_open(US"misc", O_RDWR, &dbblock, TRUE)))
  {
  uschar * ehlo_resp_key = ehlo_cache_key(sx);
  dbfn_delete(dbm_file, ehlo_resp_key);
  dbfn_close(dbm_file);
  }
}

static BOOL
read_ehlo_cache_entry(smtp_context * sx)
{
open_db dbblock;
open_db * dbm_file;

if (!(dbm_file = dbfn_open(US"misc", O_RDONLY, &dbblock, FALSE)))
  { DEBUG(D_transport) debug_printf("ehlo-cache: no misc DB\n"); }
else
  {
  uschar * ehlo_resp_key = ehlo_cache_key(sx);
  dbdata_ehlo_resp * er;

  if (!(er = dbfn_read(dbm_file, ehlo_resp_key)))
    { DEBUG(D_transport) debug_printf("no ehlo-resp record\n"); }
  else if (time(NULL) - er->time_stamp > retry_data_expire)
    {
    DEBUG(D_transport) debug_printf("ehlo-resp record too old\n");
    dbfn_close(dbm_file);
    if ((dbm_file = dbfn_open(US"misc", O_RDWR, &dbblock, TRUE)))
      dbfn_delete(dbm_file, ehlo_resp_key);
    }
  else
    {
    sx->ehlo_resp = er->data;
    dbfn_close(dbm_file);
    DEBUG(D_transport) debug_printf(
	"EHLO response bits from cache: cleartext 0x%04x crypted 0x%04x\n",
	er->data.cleartext_features, er->data.crypted_features);
    return TRUE;
    }
  dbfn_close(dbm_file);
  }
return FALSE;
}



/* Return an auths bitmap for the set of AUTH methods offered by the server
which match our authenticators. */

static unsigned short
study_ehlo_auths(smtp_context * sx)
{
uschar * names;
auth_instance * au;
uschar authnum;
unsigned short authbits = 0;

if (!sx->esmtp) return 0;
if (!regex_AUTH) regex_AUTH = regex_must_compile(AUTHS_REGEX, FALSE, TRUE);
if (!regex_match_and_setup(regex_AUTH, sx->buffer, 0, -1)) return 0;
expand_nmax = -1;						/* reset */
names = string_copyn(expand_nstring[1], expand_nlength[1]);

for (au = auths, authnum = 0; au; au = au->next, authnum++) if (au->client)
  {
  const uschar * list = names;
  int sep = ' ';
  uschar name[32];

  while (string_nextinlist(&list, &sep, name, sizeof(name)))
    if (strcmpic(au->public_name, name) == 0)
      { authbits |= BIT(authnum); break; }
  }

DEBUG(D_transport)
  debug_printf("server offers %s AUTH, methods '%s', bitmap 0x%04x\n",
    tls_out.active.sock >= 0 ? "crypted" : "plaintext", names, authbits);

if (tls_out.active.sock >= 0)
  sx->ehlo_resp.crypted_auths = authbits;
else
  sx->ehlo_resp.cleartext_auths = authbits;
return authbits;
}




/* Wait for and check responses for early-pipelining.

Called from the lower-level smtp_read_response() function
used for general code that assume synchronisation, if context
flags indicate outstanding early-pipelining commands.  Also
called fom sync_responses() which handles pipelined commands.

Arguments:
 sx	smtp connection context
 countp	number of outstanding responses, adjusted on return

Return:
 OK	all well
 FAIL	SMTP error in response
*/
int
smtp_reap_early_pipe(smtp_context * sx, int * countp)
{
BOOL pending_BANNER = sx->pending_BANNER;
BOOL pending_EHLO = sx->pending_EHLO;

sx->pending_BANNER = FALSE;	/* clear early to avoid recursion */
sx->pending_EHLO = FALSE;

if (pending_BANNER)
  {
  DEBUG(D_transport) debug_printf("%s expect banner\n", __FUNCTION__);
  (*countp)--;
  if (!smtp_reap_banner(sx))
    {
    DEBUG(D_transport) debug_printf("bad banner\n");
    goto fail;
    }
  }

if (pending_EHLO)
  {
  unsigned peer_offered;
  unsigned short authbits = 0, * ap;

  DEBUG(D_transport) debug_printf("%s expect ehlo\n", __FUNCTION__);
  (*countp)--;
  if (!smtp_reap_ehlo(sx))
    {
    DEBUG(D_transport) debug_printf("bad response for EHLO\n");
    goto fail;
    }

  /* Compare the actual EHLO response to the cached value we assumed;
  on difference, dump or rewrite the cache and arrange for a retry. */

  ap = tls_out.active.sock < 0
      ? &sx->ehlo_resp.cleartext_auths : &sx->ehlo_resp.crypted_auths;

  peer_offered = ehlo_response(sx->buffer,
	  (tls_out.active.sock < 0 ?  OPTION_TLS : OPTION_REQUIRETLS)
	| OPTION_CHUNKING | OPTION_PRDR | OPTION_DSN | OPTION_PIPE | OPTION_SIZE
	| OPTION_UTF8 | OPTION_EARLY_PIPE
	);
  if (  peer_offered != sx->peer_offered
     || (authbits = study_ehlo_auths(sx)) != *ap)
    {
    HDEBUG(D_transport)
      debug_printf("EHLO %s extensions changed, 0x%04x/0x%04x -> 0x%04x/0x%04x\n",
		    tls_out.active.sock < 0 ? "cleartext" : "crypted",
		    sx->peer_offered, *ap, peer_offered, authbits);
    *(tls_out.active.sock < 0
      ? &sx->ehlo_resp.cleartext_features : &sx->ehlo_resp.crypted_features) = peer_offered;
    *ap = authbits;
    if (peer_offered & OPTION_EARLY_PIPE)
      write_ehlo_cache_entry(sx);
    else
      invalidate_ehlo_cache_entry(sx);

    return OK;		/* just carry on */
    }
  }
return OK;

fail:
  invalidate_ehlo_cache_entry(sx);
  (void) smtp_discard_responses(sx, sx->conn_args.ob, *countp);
  return FAIL;
}
#endif


/*************************************************
*           Synchronize SMTP responses           *
*************************************************/

/* This function is called from smtp_deliver() to receive SMTP responses from
the server, and match them up with the commands to which they relate. When
PIPELINING is not in use, this function is called after every command, and is
therefore somewhat over-engineered, but it is simpler to use a single scheme
that works both with and without PIPELINING instead of having two separate sets
of code.

The set of commands that are buffered up with pipelining may start with MAIL
and may end with DATA; in between are RCPT commands that correspond to the
addresses whose status is PENDING_DEFER. All other commands (STARTTLS, AUTH,
etc.) are never buffered.

Errors after MAIL or DATA abort the whole process leaving the response in the
buffer. After MAIL, pending responses are flushed, and the original command is
re-instated in big_buffer for error messages. For RCPT commands, the remote is
permitted to reject some recipient addresses while accepting others. However
certain errors clearly abort the whole process. Set the value in
transport_return to PENDING_OK if the address is accepted. If there is a
subsequent general error, it will get reset accordingly. If not, it will get
converted to OK at the end.

Arguments:
  sx		    smtp connection context
  count             the number of responses to read
  pending_DATA      0 if last command sent was not DATA
                   +1 if previously had a good recipient
                   -1 if not previously had a good recipient

Returns:      3 if at least one address had 2xx and one had 5xx
              2 if at least one address had 5xx but none had 2xx
              1 if at least one host had a 2xx response, but none had 5xx
              0 no address had 2xx or 5xx but no errors (all 4xx, or just DATA)
             -1 timeout while reading RCPT response
             -2 I/O or other non-response error for RCPT
             -3 DATA or MAIL failed - errno and buffer set
	     -4 banner or EHLO failed (early-pipelining)
*/

static int
sync_responses(smtp_context * sx, int count, int pending_DATA)
{
address_item * addr = sx->sync_addr;
smtp_transport_options_block * ob = sx->conn_args.ob;
int yield = 0;

#ifdef EXPERIMENTAL_PIPE_CONNECT
if (smtp_reap_early_pipe(sx, &count) != OK)
  return -4;
#endif

/* Handle the response for a MAIL command. On error, reinstate the original
command in big_buffer for error message use, and flush any further pending
responses before returning, except after I/O errors and timeouts. */

if (sx->pending_MAIL)
  {
  DEBUG(D_transport) debug_printf("%s expect mail\n", __FUNCTION__);
  count--;
  if (!smtp_read_response(sx, sx->buffer, sizeof(sx->buffer),
			  '2', ob->command_timeout))
    {
    DEBUG(D_transport) debug_printf("bad response for MAIL\n");
    Ustrcpy(big_buffer, mail_command);  /* Fits, because it came from there! */
    if (errno == 0 && sx->buffer[0] != 0)
      {
      int save_errno = 0;
      if (sx->buffer[0] == '4')
        {
        save_errno = ERRNO_MAIL4XX;
        addr->more_errno |= ((sx->buffer[1] - '0')*10 + sx->buffer[2] - '0') << 8;
        }
      count = smtp_discard_responses(sx, ob, count);
      errno = save_errno;
      }

    if (pending_DATA) count--;  /* Number of RCPT responses to come */
    while (count-- > 0)		/* Mark any pending addrs with the host used */
      {
      while (addr->transport_return != PENDING_DEFER) addr = addr->next;
      addr->host_used = sx->conn_args.host;
      addr = addr->next;
      }
    return -3;
    }
  }

if (pending_DATA) count--;  /* Number of RCPT responses to come */

/* Read and handle the required number of RCPT responses, matching each one up
with an address by scanning for the next address whose status is PENDING_DEFER.
*/

while (count-- > 0)
  {
  while (addr->transport_return != PENDING_DEFER)
    if (!(addr = addr->next))
      return -2;

  /* The address was accepted */
  addr->host_used = sx->conn_args.host;

  DEBUG(D_transport) debug_printf("%s expect rcpt\n", __FUNCTION__);
  if (smtp_read_response(sx, sx->buffer, sizeof(sx->buffer),
			  '2', ob->command_timeout))
    {
    yield |= 1;
    addr->transport_return = PENDING_OK;

    /* If af_dr_retry_exists is set, there was a routing delay on this address;
    ensure that any address-specific retry record is expunged. We do this both
    for the basic key and for the version that also includes the sender. */

    if (testflag(addr, af_dr_retry_exists))
      {
      uschar *altkey = string_sprintf("%s:<%s>", addr->address_retry_key,
        sender_address);
      retry_add_item(addr, altkey, rf_delete);
      retry_add_item(addr, addr->address_retry_key, rf_delete);
      }
    }

  /* Timeout while reading the response */

  else if (errno == ETIMEDOUT)
    {
    uschar *message = string_sprintf("SMTP timeout after RCPT TO:<%s>",
		transport_rcpt_address(addr, sx->conn_args.tblock->rcpt_include_affixes));
    set_errno_nohost(sx->first_addr, ETIMEDOUT, message, DEFER, FALSE);
    retry_add_item(addr, addr->address_retry_key, 0);
    update_waiting = FALSE;
    return -1;
    }

  /* Handle other errors in obtaining an SMTP response by returning -1. This
  will cause all the addresses to be deferred. Restore the SMTP command in
  big_buffer for which we are checking the response, so the error message
  makes sense. */

  else if (errno != 0 || sx->buffer[0] == 0)
    {
    string_format(big_buffer, big_buffer_size, "RCPT TO:<%s>",
      transport_rcpt_address(addr, sx->conn_args.tblock->rcpt_include_affixes));
    return -2;
    }

  /* Handle SMTP permanent and temporary response codes. */

  else
    {
    addr->message =
      string_sprintf("SMTP error from remote mail server after RCPT TO:<%s>: "
	"%s", transport_rcpt_address(addr, sx->conn_args.tblock->rcpt_include_affixes),
	string_printing(sx->buffer));
    setflag(addr, af_pass_message);
    if (!sx->verify)
      msglog_line(sx->conn_args.host, addr->message);

    /* The response was 5xx */

    if (sx->buffer[0] == '5')
      {
      addr->transport_return = FAIL;
      yield |= 2;
      }

    /* The response was 4xx */

    else
      {
      addr->transport_return = DEFER;
      addr->basic_errno = ERRNO_RCPT4XX;
      addr->more_errno |= ((sx->buffer[1] - '0')*10 + sx->buffer[2] - '0') << 8;

      if (!sx->verify)
	{
#ifndef DISABLE_EVENT
	event_defer_errno = addr->more_errno;
	msg_event_raise(US"msg:rcpt:host:defer", addr);
#endif

	/* Log temporary errors if there are more hosts to be tried.
	If not, log this last one in the == line. */

	if (sx->conn_args.host->next)
	  if (LOGGING(outgoing_port))
	    log_write(0, LOG_MAIN, "H=%s [%s]:%d %s", sx->conn_args.host->name,
	      sx->conn_args.host->address,
	      sx->port == PORT_NONE ? 25 : sx->port, addr->message);
	  else
	    log_write(0, LOG_MAIN, "H=%s [%s]: %s", sx->conn_args.host->name,
	      sx->conn_args.host->address, addr->message);

#ifndef DISABLE_EVENT
	else
	  msg_event_raise(US"msg:rcpt:defer", addr);
#endif

	/* Do not put this message on the list of those waiting for specific
	hosts, as otherwise it is likely to be tried too often. */

	update_waiting = FALSE;

	/* Add a retry item for the address so that it doesn't get tried again
	too soon. If address_retry_include_sender is true, add the sender address
	to the retry key. */

	retry_add_item(addr,
	  ob->address_retry_include_sender
	    ? string_sprintf("%s:<%s>", addr->address_retry_key, sender_address)
	    : addr->address_retry_key,
	  0);
	}
      }
    }
  }       /* Loop for next RCPT response */

/* Update where to start at for the next block of responses, unless we
have already handled all the addresses. */

if (addr) sx->sync_addr = addr->next;

/* Handle a response to DATA. If we have not had any good recipients, either
previously or in this block, the response is ignored. */

if (pending_DATA != 0)
  {
  DEBUG(D_transport) debug_printf("%s expect data\n", __FUNCTION__);
  if (!smtp_read_response(sx, sx->buffer, sizeof(sx->buffer),
			'3', ob->command_timeout))
    {
    int code;
    uschar *msg;
    BOOL pass_message;
    if (pending_DATA > 0 || (yield & 1) != 0)
      {
      if (errno == 0 && sx->buffer[0] == '4')
	{
	errno = ERRNO_DATA4XX;
	sx->first_addr->more_errno |= ((sx->buffer[1] - '0')*10 + sx->buffer[2] - '0') << 8;
	}
      return -3;
      }
    (void)check_response(sx->conn_args.host, &errno, 0, sx->buffer, &code, &msg, &pass_message);
    DEBUG(D_transport) debug_printf("%s\nerror for DATA ignored: pipelining "
      "is in use and there were no good recipients\n", msg);
    }
  }

/* All responses read and handled; MAIL (if present) received 2xx and DATA (if
present) received 3xx. If any RCPTs were handled and yielded anything other
than 4xx, yield will be set non-zero. */

return yield;
}





/* Try an authenticator's client entry */

static int
try_authenticator(smtp_context * sx, auth_instance * au)
{
smtp_transport_options_block * ob = sx->conn_args.ob;	/* transport options */
host_item * host = sx->conn_args.host;			/* host to deliver to */
int rc;

sx->outblock.authenticating = TRUE;
rc = (au->info->clientcode)(au, sx, ob->command_timeout,
			    sx->buffer, sizeof(sx->buffer));
sx->outblock.authenticating = FALSE;
DEBUG(D_transport) debug_printf("%s authenticator yielded %d\n", au->name, rc);

/* A temporary authentication failure must hold up delivery to
this host. After a permanent authentication failure, we carry on
to try other authentication methods. If all fail hard, try to
deliver the message unauthenticated unless require_auth was set. */

switch(rc)
  {
  case OK:
    f.smtp_authenticated = TRUE;   /* stops the outer loop */
    client_authenticator = au->name;
    if (au->set_client_id)
      client_authenticated_id = expand_string(au->set_client_id);
    break;

  /* Failure after writing a command */

  case FAIL_SEND:
    return FAIL_SEND;

  /* Failure after reading a response */

  case FAIL:
    if (errno != 0 || sx->buffer[0] != '5') return FAIL;
    log_write(0, LOG_MAIN, "%s authenticator failed H=%s [%s] %s",
      au->name, host->name, host->address, sx->buffer);
    break;

  /* Failure by some other means. In effect, the authenticator
  decided it wasn't prepared to handle this case. Typically this
  is the result of "fail" in an expansion string. Do we need to
  log anything here? Feb 2006: a message is now put in the buffer
  if logging is required. */

  case CANCELLED:
    if (*sx->buffer != 0)
      log_write(0, LOG_MAIN, "%s authenticator cancelled "
	"authentication H=%s [%s] %s", au->name, host->name,
	host->address, sx->buffer);
    break;

  /* Internal problem, message in buffer. */

  case ERROR:
    set_errno_nohost(sx->addrlist, ERRNO_AUTHPROB, string_copy(sx->buffer),
	      DEFER, FALSE);
    return ERROR;
  }
return OK;
}




/* Do the client side of smtp-level authentication.

Arguments:
  sx		smtp connection context

sx->buffer should have the EHLO response from server (gets overwritten)

Returns:
  OK			Success, or failed (but not required): global "smtp_authenticated" set
  DEFER			Failed authentication (and was required)
  ERROR			Internal problem

  FAIL_SEND		Failed communications - transmit
  FAIL			- response
*/

static int
smtp_auth(smtp_context * sx)
{
host_item * host = sx->conn_args.host;			/* host to deliver to */
smtp_transport_options_block * ob = sx->conn_args.ob;	/* transport options */
int require_auth = verify_check_given_host(CUSS &ob->hosts_require_auth, host);
#ifdef EXPERIMENTAL_PIPE_CONNECT
unsigned short authbits = tls_out.active.sock >= 0
      ? sx->ehlo_resp.crypted_auths : sx->ehlo_resp.cleartext_auths;
#endif
uschar * fail_reason = US"server did not advertise AUTH support";

f.smtp_authenticated = FALSE;
client_authenticator = client_authenticated_id = client_authenticated_sender = NULL;

if (!regex_AUTH)
  regex_AUTH = regex_must_compile(AUTHS_REGEX, FALSE, TRUE);

/* Is the server offering AUTH? */

if (  sx->esmtp
   &&
#ifdef EXPERIMENTAL_PIPE_CONNECT
      sx->early_pipe_active ? authbits
      :
#endif
	regex_match_and_setup(regex_AUTH, sx->buffer, 0, -1)
   )
  {
  uschar * names = NULL;
  expand_nmax = -1;                          /* reset */

#ifdef EXPERIMENTAL_PIPE_CONNECT
  if (!sx->early_pipe_active)
#endif
    names = string_copyn(expand_nstring[1], expand_nlength[1]);

  /* Must not do this check until after we have saved the result of the
  regex match above as the check could be another RE. */

  if (  require_auth == OK
     || verify_check_given_host(CUSS &ob->hosts_try_auth, host) == OK)
    {
    auth_instance * au;

    DEBUG(D_transport) debug_printf("scanning authentication mechanisms\n");
    fail_reason = US"no common mechanisms were found";

#ifdef EXPERIMENTAL_PIPE_CONNECT
    if (sx->early_pipe_active)
      {
      /* Scan our authenticators (which support use by a client and were offered
      by the server (checked at cache-write time)), not suppressed by
      client_condition.  If one is found, attempt to authenticate by calling its
      client function.  We are limited to supporting up to 16 authenticator
      public-names by the number of bits in a short. */

      uschar bitnum;
      int rc;

      for (bitnum = 0, au = auths;
	   !f.smtp_authenticated && au && bitnum < 16;
	   bitnum++, au = au->next) if (authbits & BIT(bitnum))
	{
	if (  au->client_condition
	   && !expand_check_condition(au->client_condition, au->name,
                   US"client authenticator"))
	  {
	  DEBUG(D_transport) debug_printf("skipping %s authenticator: %s\n",
	    au->name, "client_condition is false");
	  continue;
	  }

	/* Found data for a listed mechanism. Call its client entry. Set
	a flag in the outblock so that data is overwritten after sending so
	that reflections don't show it. */

	fail_reason = US"authentication attempt(s) failed";

	if ((rc = try_authenticator(sx, au)) != OK)
	  return rc;
	}
      }
    else
#endif

    /* Scan the configured authenticators looking for one which is configured
    for use as a client, which is not suppressed by client_condition, and
    whose name matches an authentication mechanism supported by the server.
    If one is found, attempt to authenticate by calling its client function.
    */

    for (au = auths; !f.smtp_authenticated && au; au = au->next)
      {
      uschar *p = names;

      if (  !au->client
         || (   au->client_condition
	    &&  !expand_check_condition(au->client_condition, au->name,
		   US"client authenticator")))
	{
	DEBUG(D_transport) debug_printf("skipping %s authenticator: %s\n",
	  au->name,
	  (au->client)? "client_condition is false" :
			"not configured as a client");
	continue;
	}

      /* Loop to scan supported server mechanisms */

      while (*p)
	{
	int len = Ustrlen(au->public_name);
	int rc;

	while (isspace(*p)) p++;

	if (strncmpic(au->public_name, p, len) != 0 ||
	    (p[len] != 0 && !isspace(p[len])))
	  {
	  while (*p != 0 && !isspace(*p)) p++;
	  continue;
	  }

	/* Found data for a listed mechanism. Call its client entry. Set
	a flag in the outblock so that data is overwritten after sending so
	that reflections don't show it. */

	fail_reason = US"authentication attempt(s) failed";

	if ((rc = try_authenticator(sx, au)) != OK)
	  return rc;

	break;  /* If not authenticated, try next authenticator */
	}       /* Loop for scanning supported server mechanisms */
      }         /* Loop for further authenticators */
    }
  }

/* If we haven't authenticated, but are required to, give up. */

if (require_auth == OK && !f.smtp_authenticated)
  {
  set_errno_nohost(sx->addrlist, ERRNO_AUTHFAIL,
    string_sprintf("authentication required but %s", fail_reason), DEFER,
    FALSE);
  return DEFER;
  }

return OK;
}


/* Construct AUTH appendix string for MAIL TO */
/*
Arguments
  buffer	to build string
  addrlist      chain of potential addresses to deliver
  ob		transport options

Globals		f.smtp_authenticated
		client_authenticated_sender
Return	True on error, otherwise buffer has (possibly empty) terminated string
*/

BOOL
smtp_mail_auth_str(uschar *buffer, unsigned bufsize, address_item *addrlist,
		    smtp_transport_options_block *ob)
{
uschar *local_authenticated_sender = authenticated_sender;

#ifdef notdef
  debug_printf("smtp_mail_auth_str: as<%s> os<%s> SA<%s>\n", authenticated_sender, ob->authenticated_sender, f.smtp_authenticated?"Y":"N");
#endif

if (ob->authenticated_sender != NULL)
  {
  uschar *new = expand_string(ob->authenticated_sender);
  if (new == NULL)
    {
    if (!f.expand_string_forcedfail)
      {
      uschar *message = string_sprintf("failed to expand "
        "authenticated_sender: %s", expand_string_message);
      set_errno_nohost(addrlist, ERRNO_EXPANDFAIL, message, DEFER, FALSE);
      return TRUE;
      }
    }
  else if (new[0] != 0) local_authenticated_sender = new;
  }

/* Add the authenticated sender address if present */

if ((f.smtp_authenticated || ob->authenticated_sender_force) &&
    local_authenticated_sender != NULL)
  {
  string_format(buffer, bufsize, " AUTH=%s",
    auth_xtextencode(local_authenticated_sender,
    Ustrlen(local_authenticated_sender)));
  client_authenticated_sender = string_copy(local_authenticated_sender);
  }
else
  *buffer= 0;

return FALSE;
}



#ifdef SUPPORT_DANE
/* Lookup TLSA record for host/port.
Return:  OK		success with dnssec; DANE mode
         DEFER		Do not use this host now, may retry later
	 FAIL_FORCED	No TLSA record; DANE not usable
	 FAIL		Do not use this connection
*/

int
tlsa_lookup(const host_item * host, dns_answer * dnsa, BOOL dane_required)
{
/* move this out to host.c given the similarity to dns_lookup() ? */
uschar buffer[300];
const uschar * fullname = buffer;
int rc;
BOOL sec;

/* TLSA lookup string */
(void)sprintf(CS buffer, "_%d._tcp.%.256s", host->port, host->name);

rc = dns_lookup(dnsa, buffer, T_TLSA, &fullname);
sec = dns_is_secure(dnsa);
DEBUG(D_transport)
  debug_printf("TLSA lookup ret %d %sDNSSEC\n", rc, sec ? "" : "not ");

switch (rc)
  {
  case DNS_AGAIN:
    return DEFER; /* just defer this TLS'd conn */

  case DNS_SUCCEED:
    if (sec)
      {
      DEBUG(D_transport)
	{
	dns_scan dnss;
	dns_record * rr;
	for (rr = dns_next_rr(dnsa, &dnss, RESET_ANSWERS); rr;
	     rr = dns_next_rr(dnsa, &dnss, RESET_NEXT))
	  if (rr->type == T_TLSA && rr->size > 3)
	    {
	    uint16_t payload_length = rr->size - 3;
	    uschar s[MAX_TLSA_EXPANDED_SIZE], * sp = s, * p = US rr->data;

	    sp += sprintf(CS sp, "%d ", *p++); /* usage */
	    sp += sprintf(CS sp, "%d ", *p++); /* selector */
	    sp += sprintf(CS sp, "%d ", *p++); /* matchtype */
	    while (payload_length-- > 0 && sp-s < (MAX_TLSA_EXPANDED_SIZE - 4))
	      sp += sprintf(CS sp, "%02x", *p++);

	    debug_printf(" %s\n", s);
	    }
	}
      return OK;
      }
    log_write(0, LOG_MAIN,
      "DANE error: TLSA lookup for %s not DNSSEC", host->name);
    /*FALLTRHOUGH*/

  case DNS_NODATA:	/* no TLSA RR for this lookup */
  case DNS_NOMATCH:	/* no records at all for this lookup */
    return dane_required ? FAIL : FAIL_FORCED;

  default:
  case DNS_FAIL:
    return dane_required ? FAIL : DEFER;
  }
}
#endif



typedef struct smtp_compare_s
{
    uschar                          *current_sender_address;
    struct transport_instance       *tblock;
} smtp_compare_t;


/* Create a unique string that identifies this message, it is based on
sender_address, helo_data and tls_certificate if enabled.
*/

static uschar *
smtp_local_identity(uschar * sender, struct transport_instance * tblock)
{
address_item * addr1;
uschar * if1 = US"";
uschar * helo1 = US"";
#ifdef SUPPORT_TLS
uschar * tlsc1 = US"";
#endif
uschar * save_sender_address = sender_address;
uschar * local_identity = NULL;
smtp_transport_options_block * ob = SOB tblock->options_block;

sender_address = sender;

addr1 = deliver_make_addr (sender, TRUE);
deliver_set_expansions(addr1);

if (ob->interface)
  if1 = expand_string(ob->interface);

if (ob->helo_data)
  helo1 = expand_string(ob->helo_data);

#ifdef SUPPORT_TLS
if (ob->tls_certificate)
  tlsc1 = expand_string(ob->tls_certificate);
local_identity = string_sprintf ("%s^%s^%s", if1, helo1, tlsc1);
#else
local_identity = string_sprintf ("%s^%s", if1, helo1);
#endif

deliver_set_expansions(NULL);
sender_address = save_sender_address;

return local_identity;
}



/* This routine is a callback that is called from transport_check_waiting.
This function will evaluate the incoming message versus the previous
message.  If the incoming message is using a different local identity then
we will veto this new message.  */

static BOOL
smtp_are_same_identities(uschar * message_id, smtp_compare_t * s_compare)
{
uschar * message_local_identity,
       * current_local_identity,
       * new_sender_address;

current_local_identity =
  smtp_local_identity(s_compare->current_sender_address, s_compare->tblock);

if (!(new_sender_address = deliver_get_sender_address(message_id)))
    return 0;

message_local_identity =
  smtp_local_identity(new_sender_address, s_compare->tblock);

return Ustrcmp(current_local_identity, message_local_identity) == 0;
}



static unsigned
ehlo_response(uschar * buf, unsigned checks)
{
size_t bsize = Ustrlen(buf);

/* debug_printf("%s: check for 0x%04x\n", __FUNCTION__, checks); */

#ifdef SUPPORT_TLS
# ifdef EXPERIMENTAL_REQUIRETLS
if (  checks & OPTION_REQUIRETLS
   && pcre_exec(regex_REQUIRETLS, NULL, CS buf,bsize, 0, PCRE_EOPT, NULL,0) < 0)
# endif
  checks &= ~OPTION_REQUIRETLS;

if (  checks & OPTION_TLS
   && pcre_exec(regex_STARTTLS, NULL, CS buf, bsize, 0, PCRE_EOPT, NULL, 0) < 0)
#endif
  checks &= ~OPTION_TLS;

if (  checks & OPTION_IGNQ
   && pcre_exec(regex_IGNOREQUOTA, NULL, CS buf, bsize, 0,
		PCRE_EOPT, NULL, 0) < 0)
  checks &= ~OPTION_IGNQ;

if (  checks & OPTION_CHUNKING
   && pcre_exec(regex_CHUNKING, NULL, CS buf, bsize, 0, PCRE_EOPT, NULL, 0) < 0)
  checks &= ~OPTION_CHUNKING;

#ifndef DISABLE_PRDR
if (  checks & OPTION_PRDR
   && pcre_exec(regex_PRDR, NULL, CS buf, bsize, 0, PCRE_EOPT, NULL, 0) < 0)
#endif
  checks &= ~OPTION_PRDR;

#ifdef SUPPORT_I18N
if (  checks & OPTION_UTF8
   && pcre_exec(regex_UTF8, NULL, CS buf, bsize, 0, PCRE_EOPT, NULL, 0) < 0)
#endif
  checks &= ~OPTION_UTF8;

if (  checks & OPTION_DSN
   && pcre_exec(regex_DSN, NULL, CS buf, bsize, 0, PCRE_EOPT, NULL, 0) < 0)
  checks &= ~OPTION_DSN;

if (  checks & OPTION_PIPE
   && pcre_exec(regex_PIPELINING, NULL, CS buf, bsize, 0,
		PCRE_EOPT, NULL, 0) < 0)
  checks &= ~OPTION_PIPE;

if (  checks & OPTION_SIZE
   && pcre_exec(regex_SIZE, NULL, CS buf, bsize, 0, PCRE_EOPT, NULL, 0) < 0)
  checks &= ~OPTION_SIZE;

#ifdef EXPERIMENTAL_PIPE_CONNECT
if (  checks & OPTION_EARLY_PIPE
   && pcre_exec(regex_EARLY_PIPE, NULL, CS buf, bsize, 0,
		PCRE_EOPT, NULL, 0) < 0)
#endif
  checks &= ~OPTION_EARLY_PIPE;

/* debug_printf("%s: found     0x%04x\n", __FUNCTION__, checks); */
return checks;
}



/* Callback for emitting a BDAT data chunk header.

If given a nonzero size, first flush any buffered SMTP commands
then emit the command.

Reap previous SMTP command responses if requested, and always reap
the response from a previous BDAT command.

Args:
 tctx		transport context
 chunk_size	value for SMTP BDAT command
 flags
   tc_chunk_last	add LAST option to SMTP BDAT command
   tc_reap_prev		reap response to previous SMTP commands

Returns:	OK or ERROR
*/

static int
smtp_chunk_cmd_callback(transport_ctx * tctx, unsigned chunk_size,
  unsigned flags)
{
smtp_transport_options_block * ob = SOB tctx->tblock->options_block;
smtp_context * sx = tctx->smtp_context;
int cmd_count = 0;
int prev_cmd_count;

/* Write SMTP chunk header command.  If not reaping responses, note that
there may be more writes (like, the chunk data) done soon. */

if (chunk_size > 0)
  {
#ifdef EXPERIMENTAL_PIPE_CONNECT
  BOOL new_conn = !!(sx->outblock.conn_args);
#endif
  if((cmd_count = smtp_write_command(sx,
	      flags & tc_reap_prev ? SCMD_FLUSH : SCMD_MORE,
	      "BDAT %u%s\r\n", chunk_size, flags & tc_chunk_last ? " LAST" : "")
     ) < 0) return ERROR;
  if (flags & tc_chunk_last)
    data_command = string_copy(big_buffer);  /* Save for later error message */
#ifdef EXPERIMENTAL_PIPE_CONNECT
  /* That command write could have been the one that made the connection.
  Copy the fd from the client conn ctx (smtp transport specific) to the
  generic transport ctx. */

  if (new_conn)
    tctx->u.fd = sx->outblock.cctx->sock;
#endif
  }

prev_cmd_count = cmd_count += sx->cmd_count;

/* Reap responses for any previous, but not one we just emitted */

if (chunk_size > 0)
  prev_cmd_count--;
if (sx->pending_BDAT)
  prev_cmd_count--;

if (flags & tc_reap_prev  &&  prev_cmd_count > 0)
  {
  DEBUG(D_transport) debug_printf("look for %d responses"
    " for previous pipelined cmds\n", prev_cmd_count);

  switch(sync_responses(sx, prev_cmd_count, 0))
    {
    case 1:				/* 2xx (only) => OK */
    case 3: sx->good_RCPT = TRUE;	/* 2xx & 5xx => OK & progress made */
    case 2: sx->completed_addr = TRUE;	/* 5xx (only) => progress made */
    case 0: break;			/* No 2xx or 5xx, but no probs */

    case -1:				/* Timeout on RCPT */
#ifdef EXPERIMENTAL_PIPE_CONNECT
    case -4:				/* non-2xx for pipelined banner or EHLO */
#endif
    default: return ERROR;		/* I/O error, or any MAIL/DATA error */
    }
  cmd_count = 1;
  if (!sx->pending_BDAT)
    pipelining_active = FALSE;
  }

/* Reap response for an outstanding BDAT */

if (sx->pending_BDAT)
  {
  DEBUG(D_transport) debug_printf("look for one response for BDAT\n");

  if (!smtp_read_response(sx, sx->buffer, sizeof(sx->buffer), '2',
       ob->command_timeout))
    {
    if (errno == 0 && sx->buffer[0] == '4')
      {
      errno = ERRNO_DATA4XX;	/*XXX does this actually get used? */
      sx->addrlist->more_errno |=
	((sx->buffer[1] - '0')*10 + sx->buffer[2] - '0') << 8;
      }
    return ERROR;
    }
  cmd_count--;
  sx->pending_BDAT = FALSE;
  pipelining_active = FALSE;
  }
else if (chunk_size > 0)
  sx->pending_BDAT = TRUE;


sx->cmd_count = cmd_count;
return OK;
}





/*************************************************
*       Make connection for given message        *
*************************************************/

/*
Arguments:
  ctx		  connection context
  suppress_tls    if TRUE, don't attempt a TLS connection - this is set for
                    a second attempt after TLS initialization fails

Returns:          OK    - the connection was made and the delivery attempted;
                          fd is set in the conn context, tls_out set up.
                  DEFER - the connection could not be made, or something failed
                          while setting up the SMTP session, or there was a
                          non-message-specific error, such as a timeout.
                  ERROR - helo_data or add_headers or authenticated_sender is
			  specified for this transport, and the string failed
			  to expand
*/
int
smtp_setup_conn(smtp_context * sx, BOOL suppress_tls)
{
#if defined(SUPPORT_TLS) && defined(SUPPORT_DANE)
dns_answer tlsa_dnsa;
#endif
smtp_transport_options_block * ob = sx->conn_args.tblock->options_block;
BOOL pass_message = FALSE;
uschar * message = NULL;
int yield = OK;
int rc;

sx->conn_args.ob = ob;

sx->lmtp = strcmpic(ob->protocol, US"lmtp") == 0;
sx->smtps = strcmpic(ob->protocol, US"smtps") == 0;
sx->ok = FALSE;
sx->send_rset = TRUE;
sx->send_quit = TRUE;
sx->setting_up = TRUE;
sx->esmtp = TRUE;
sx->esmtp_sent = FALSE;
#ifdef SUPPORT_I18N
sx->utf8_needed = FALSE;
#endif
sx->dsn_all_lasthop = TRUE;
#if defined(SUPPORT_TLS) && defined(SUPPORT_DANE)
sx->dane = FALSE;
sx->dane_required =
  verify_check_given_host(CUSS &ob->hosts_require_dane, sx->conn_args.host) == OK;
#endif
#ifdef EXPERIMENTAL_PIPE_CONNECT
sx->early_pipe_active = sx->early_pipe_ok = FALSE;
sx->ehlo_resp.cleartext_features = sx->ehlo_resp.crypted_features = 0;
sx->pending_BANNER = sx->pending_EHLO = FALSE;
#endif

if ((sx->max_rcpt = sx->conn_args.tblock->max_addresses) == 0) sx->max_rcpt = 999999;
sx->peer_offered = 0;
sx->avoid_option = 0;
sx->igquotstr = US"";
if (!sx->helo_data) sx->helo_data = ob->helo_data;
#ifdef EXPERIMENTAL_DSN_INFO
sx->smtp_greeting = NULL;
sx->helo_response = NULL;
#endif

smtp_command = US"initial connection";
sx->buffer[0] = '\0';

/* Set up the buffer for reading SMTP response packets. */

sx->inblock.buffer = sx->inbuffer;
sx->inblock.buffersize = sizeof(sx->inbuffer);
sx->inblock.ptr = sx->inbuffer;
sx->inblock.ptrend = sx->inbuffer;

/* Set up the buffer for holding SMTP commands while pipelining */

sx->outblock.buffer = sx->outbuffer;
sx->outblock.buffersize = sizeof(sx->outbuffer);
sx->outblock.ptr = sx->outbuffer;
sx->outblock.cmd_count = 0;
sx->outblock.authenticating = FALSE;
sx->outblock.conn_args = NULL;

/* Reset the parameters of a TLS session. */

tls_out.bits = 0;
tls_out.cipher = NULL;	/* the one we may use for this transport */
tls_out.ourcert = NULL;
tls_out.peercert = NULL;
tls_out.peerdn = NULL;
#if defined(SUPPORT_TLS) && !defined(USE_GNUTLS)
tls_out.sni = NULL;
#endif
tls_out.ocsp = OCSP_NOT_REQ;

/* Flip the legacy TLS-related variables over to the outbound set in case
they're used in the context of the transport.  Don't bother resetting
afterward (when being used by a transport) as we're in a subprocess.
For verify, unflipped once the callout is dealt with */

tls_modify_variables(&tls_out);

#ifndef SUPPORT_TLS
if (sx->smtps)
  {
  set_errno_nohost(sx->addrlist, ERRNO_TLSFAILURE, US"TLS support not available",
	    DEFER, FALSE);
  return ERROR;
  }
#endif

/* Make a connection to the host if this isn't a continued delivery, and handle
the initial interaction and HELO/EHLO/LHLO. Connect timeout errors are handled
specially so they can be identified for retries. */

if (!continue_hostname)
  {
  if (sx->verify)
    HDEBUG(D_verify) debug_printf("interface=%s port=%d\n", sx->conn_args.interface, sx->port);

  /* Get the actual port the connection will use, into sx->conn_args.host */

  smtp_port_for_connect(sx->conn_args.host, sx->port);

#if defined(SUPPORT_TLS) && defined(SUPPORT_DANE)
    /* Do TLSA lookup for DANE */
    {
    tls_out.dane_verified = FALSE;
    tls_out.tlsa_usage = 0;

    if (sx->conn_args.host->dnssec == DS_YES)
      {
      if(  sx->dane_required
	|| verify_check_given_host(CUSS &ob->hosts_try_dane, sx->conn_args.host) == OK
	)
	switch (rc = tlsa_lookup(sx->conn_args.host, &tlsa_dnsa, sx->dane_required))
	  {
	  case OK:		sx->dane = TRUE;
				ob->tls_tempfail_tryclear = FALSE;
				break;
	  case FAIL_FORCED:	break;
	  default:		set_errno_nohost(sx->addrlist, ERRNO_DNSDEFER,
				  string_sprintf("DANE error: tlsa lookup %s",
				    rc == DEFER ? "DEFER" : "FAIL"),
				  rc, FALSE);
# ifndef DISABLE_EVENT
				(void) event_raise(sx->conn_args.tblock->event_action,
				  US"dane:fail", sx->dane_required
				    ?  US"dane-required" : US"dnssec-invalid");
# endif
				return rc;
	  }
      }
    else if (sx->dane_required)
      {
      set_errno_nohost(sx->addrlist, ERRNO_DNSDEFER,
	string_sprintf("DANE error: %s lookup not DNSSEC", sx->conn_args.host->name),
	FAIL, FALSE);
# ifndef DISABLE_EVENT
      (void) event_raise(sx->conn_args.tblock->event_action,
	US"dane:fail", US"dane-required");
# endif
      return FAIL;
      }
    }
#endif	/*DANE*/

  /* Make the TCP connection */

  sx->cctx.tls_ctx = NULL;
  sx->inblock.cctx = sx->outblock.cctx = &sx->cctx;
  sx->avoid_option = sx->peer_offered = smtp_peer_options = 0;

#ifdef EXPERIMENTAL_PIPE_CONNECT
  if (verify_check_given_host(CUSS &ob->hosts_pipe_connect, sx->conn_args.host) == OK)
    {
    sx->early_pipe_ok = TRUE;
    if (  read_ehlo_cache_entry(sx)
       && sx->ehlo_resp.cleartext_features & OPTION_EARLY_PIPE)
      {
      DEBUG(D_transport) debug_printf("Using cached cleartext PIPE_CONNECT\n");
      sx->early_pipe_active = TRUE;
      sx->peer_offered = sx->ehlo_resp.cleartext_features;
      }
    }

  if (sx->early_pipe_active)
    sx->outblock.conn_args = &sx->conn_args;
  else
#endif
    {
    if ((sx->cctx.sock = smtp_connect(&sx->conn_args, NULL)) < 0)
      {
      uschar * msg = NULL;
      if (sx->verify)
	{
	msg = US strerror(errno);
	HDEBUG(D_verify) debug_printf("connect: %s\n", msg);
	}
      set_errno_nohost(sx->addrlist,
	errno == ETIMEDOUT ? ERRNO_CONNECTTIMEOUT : errno,
	sx->verify ? string_sprintf("could not connect: %s", msg)
	       : NULL,
	DEFER, FALSE);
      sx->send_quit = FALSE;
      return DEFER;
      }
    }
  /* Expand the greeting message while waiting for the initial response. (Makes
  sense if helo_data contains ${lookup dnsdb ...} stuff). The expansion is
  delayed till here so that $sending_interface and $sending_port are set. */
/*XXX early-pipe: they still will not be. Is there any way to find out what they
will be?  Somehow I doubt it. */

  if (sx->helo_data)
    if (!(sx->helo_data = expand_string(sx->helo_data)))
      if (sx->verify)
	log_write(0, LOG_MAIN|LOG_PANIC,
	  "<%s>: failed to expand transport's helo_data value for callout: %s",
	  sx->addrlist->address, expand_string_message);

#ifdef SUPPORT_I18N
  if (sx->helo_data)
    {
    expand_string_message = NULL;
    if ((sx->helo_data = string_domain_utf8_to_alabel(sx->helo_data,
					      &expand_string_message)),
	expand_string_message)
      if (sx->verify)
	log_write(0, LOG_MAIN|LOG_PANIC,
	  "<%s>: failed to expand transport's helo_data value for callout: %s",
	  sx->addrlist->address, expand_string_message);
      else
	sx->helo_data = NULL;
    }
#endif

  /* The first thing is to wait for an initial OK response. The dreaded "goto"
  is nevertheless a reasonably clean way of programming this kind of logic,
  where you want to escape on any error. */

  if (!sx->smtps)
    {
#ifdef EXPERIMENTAL_PIPE_CONNECT
    if (sx->early_pipe_active)
      {
      sx->pending_BANNER = TRUE;	/* sync_responses() must eventually handle */
      sx->outblock.cmd_count = 1;
      }
    else
#endif
      {
#ifdef TCP_QUICKACK
      (void) setsockopt(sx->cctx.sock, IPPROTO_TCP, TCP_QUICKACK, US &off,
			sizeof(off));
#endif
      if (!smtp_reap_banner(sx))
	goto RESPONSE_FAILED;
      }

#ifndef DISABLE_EVENT
      {
      uschar * s;
      lookup_dnssec_authenticated = sx->conn_args.host->dnssec==DS_YES ? US"yes"
	: sx->conn_args.host->dnssec==DS_NO ? US"no" : NULL;
      s = event_raise(sx->conn_args.tblock->event_action, US"smtp:connect", sx->buffer);
      if (s)
	{
	set_errno_nohost(sx->addrlist, ERRNO_EXPANDFAIL,
	  string_sprintf("deferred by smtp:connect event expansion: %s", s),
	  DEFER, FALSE);
	yield = DEFER;
	goto SEND_QUIT;
	}
      }
#endif

    /* Now check if the helo_data expansion went well, and sign off cleanly if
    it didn't. */

    if (!sx->helo_data)
      {
      message = string_sprintf("failed to expand helo_data: %s",
        expand_string_message);
      set_errno_nohost(sx->addrlist, ERRNO_EXPANDFAIL, message, DEFER, FALSE);
      yield = DEFER;
      goto SEND_QUIT;
      }
    }

/** Debugging without sending a message
sx->addrlist->transport_return = DEFER;
goto SEND_QUIT;
**/

  /* Errors that occur after this point follow an SMTP command, which is
  left in big_buffer by smtp_write_command() for use in error messages. */

  smtp_command = big_buffer;

  /* Tell the remote who we are...

  February 1998: A convention has evolved that ESMTP-speaking MTAs include the
  string "ESMTP" in their greeting lines, so make Exim send EHLO if the
  greeting is of this form. The assumption was that the far end supports it
  properly... but experience shows that there are some that give 5xx responses,
  even though the banner includes "ESMTP" (there's a bloody-minded one that
  says "ESMTP not spoken here"). Cope with that case.

  September 2000: Time has passed, and it seems reasonable now to always send
  EHLO at the start. It is also convenient to make the change while installing
  the TLS stuff.

  July 2003: Joachim Wieland met a broken server that advertises "PIPELINING"
  but times out after sending MAIL FROM, RCPT TO and DATA all together. There
  would be no way to send out the mails, so there is now a host list
  "hosts_avoid_esmtp" that disables ESMTP for special hosts and solves the
  PIPELINING problem as well. Maybe it can also be useful to cure other
  problems with broken servers.

  Exim originally sent "Helo" at this point and ran for nearly a year that way.
  Then somebody tried it with a Microsoft mailer... It seems that all other
  mailers use upper case for some reason (the RFC is quite clear about case
  independence) so, for peace of mind, I gave in. */

  sx->esmtp = verify_check_given_host(CUSS &ob->hosts_avoid_esmtp, sx->conn_args.host) != OK;

  /* Alas; be careful, since this goto is not an error-out, so conceivably
  we might set data between here and the target which we assume to exist
  and be usable.  I can see this coming back to bite us. */
#ifdef SUPPORT_TLS
  if (sx->smtps)
    {
    smtp_peer_options |= OPTION_TLS;
    suppress_tls = FALSE;
    ob->tls_tempfail_tryclear = FALSE;
    smtp_command = US"SSL-on-connect";
    goto TLS_NEGOTIATE;
    }
#endif

  if (sx->esmtp)
    {
    if (smtp_write_command(sx,
#ifdef EXPERIMENTAL_PIPE_CONNECT
	  sx->early_pipe_active ? SCMD_BUFFER :
#endif
	    SCMD_FLUSH,
	  "%s %s\r\n", sx->lmtp ? "LHLO" : "EHLO", sx->helo_data) < 0)
      goto SEND_FAILED;
    sx->esmtp_sent = TRUE;

#ifdef EXPERIMENTAL_PIPE_CONNECT
    if (sx->early_pipe_active)
      {
      sx->pending_EHLO = TRUE;

      /* If we have too many authenticators to handle and might need to AUTH
      for this transport, pipeline no further as we will need the
      list of auth methods offered.  Reap the banner and EHLO. */

      if (  (ob->hosts_require_auth || ob->hosts_try_auth)
	 && f.smtp_in_early_pipe_no_auth)
	{
	DEBUG(D_transport) debug_printf("may need to auth, so pipeline no further\n");
	if (smtp_write_command(sx, SCMD_FLUSH, NULL) < 0)
	  goto SEND_FAILED;
	if (sync_responses(sx, 2, 0) != 0)
	  {
	  HDEBUG(D_transport)
	    debug_printf("failed reaping pipelined cmd responses\n");
	  goto RESPONSE_FAILED;
	  }
	sx->early_pipe_active = FALSE;
	}
      }
    else
#endif
      if (!smtp_reap_ehlo(sx))
	goto RESPONSE_FAILED;
    }
  else
    DEBUG(D_transport)
      debug_printf("not sending EHLO (host matches hosts_avoid_esmtp)\n");

#ifdef EXPERIMENTAL_PIPE_CONNECT
  if (!sx->early_pipe_active)
#endif
    if (!sx->esmtp)
      {
      BOOL good_response;
      int n = sizeof(sx->buffer);
      uschar * rsp = sx->buffer;

      if (sx->esmtp_sent && (n = Ustrlen(sx->buffer)) < sizeof(sx->buffer)/2)
	{ rsp = sx->buffer + n + 1; n = sizeof(sx->buffer) - n; }

      if (smtp_write_command(sx, SCMD_FLUSH, "HELO %s\r\n", sx->helo_data) < 0)
	goto SEND_FAILED;
      good_response = smtp_read_response(sx, rsp, n, '2', ob->command_timeout);
#ifdef EXPERIMENTAL_DSN_INFO
      sx->helo_response = string_copy(rsp);
#endif
      if (!good_response)
	{
	/* Handle special logging for a closed connection after HELO
	when had previously sent EHLO */

	if (rsp != sx->buffer && rsp[0] == 0 && (errno == 0 || errno == ECONNRESET))
	  {
	  errno = ERRNO_SMTPCLOSED;
	  goto EHLOHELO_FAILED;
	  }
	memmove(sx->buffer, rsp, Ustrlen(rsp));
	goto RESPONSE_FAILED;
	}
      }

  if (sx->esmtp || sx->lmtp)
    {
#ifdef EXPERIMENTAL_PIPE_CONNECT
    if (!sx->early_pipe_active)
#endif
      {
      sx->peer_offered = ehlo_response(sx->buffer,
	OPTION_TLS	/* others checked later */
#ifdef EXPERIMENTAL_PIPE_CONNECT
	| (sx->early_pipe_ok
	  ?   OPTION_IGNQ
	    | OPTION_CHUNKING | OPTION_PRDR | OPTION_DSN | OPTION_PIPE | OPTION_SIZE
#ifdef SUPPORT_I18N
	    | OPTION_UTF8
#endif
	    | OPTION_EARLY_PIPE
	  : 0
	  )
#endif
	);
#ifdef EXPERIMENTAL_PIPE_CONNECT
      if (sx->early_pipe_ok)
	{
	sx->ehlo_resp.cleartext_features = sx->peer_offered;

	if (  (sx->peer_offered & (OPTION_PIPE | OPTION_EARLY_PIPE))
	   == (OPTION_PIPE | OPTION_EARLY_PIPE))
	  {
	  DEBUG(D_transport) debug_printf("PIPE_CONNECT usable in future for this IP\n");
	  sx->ehlo_resp.cleartext_auths = study_ehlo_auths(sx);
	  write_ehlo_cache_entry(sx);
	  }
	}
#endif
      }

  /* Set tls_offered if the response to EHLO specifies support for STARTTLS. */

#ifdef SUPPORT_TLS
    smtp_peer_options |= sx->peer_offered & OPTION_TLS;
#endif
    }
  }

/* For continuing deliveries down the same channel, having re-exec'd  the socket
is the standard input; for a socket held open from verify it is recorded
in the cutthrough context block.  Either way we don't need to redo EHLO here
(but may need to do so for TLS - see below).
Set up the pointer to where subsequent commands will be left, for
error messages. Note that smtp_peer_options will have been
set from the command line if they were set in the process that passed the
connection on. */

/*XXX continue case needs to propagate DSN_INFO, prob. in deliver.c
as the continue goes via transport_pass_socket() and doublefork and exec.
It does not wait.  Unclear how we keep separate host's responses
separate - we could match up by host ip+port as a bodge. */

else
  {
  if (cutthrough.cctx.sock >= 0 && cutthrough.callout_hold_only)
    {
    sx->cctx = cutthrough.cctx;
    sx->conn_args.host->port = sx->port = cutthrough.host.port;
    }
  else
    {
    sx->cctx.sock = 0;				/* stdin */
    sx->cctx.tls_ctx = NULL;
    smtp_port_for_connect(sx->conn_args.host, sx->port);	/* Record the port that was used */
    }
  sx->inblock.cctx = sx->outblock.cctx = &sx->cctx;
  smtp_command = big_buffer;
  sx->helo_data = NULL;		/* ensure we re-expand ob->helo_data */

  /* For a continued connection with TLS being proxied for us, or a
  held-open verify connection with TLS, nothing more to do. */

  if (  continue_proxy_cipher
     || (cutthrough.cctx.sock >= 0 && cutthrough.callout_hold_only
         && cutthrough.is_tls)
     )
    {
    sx->peer_offered = smtp_peer_options;
    sx->pipelining_used = pipelining_active = !!(smtp_peer_options & OPTION_PIPE);
    HDEBUG(D_transport) debug_printf("continued connection, %s TLS\n",
      continue_proxy_cipher ? "proxied" : "verify conn with");
    return OK;
    }
  HDEBUG(D_transport) debug_printf("continued connection, no TLS\n");
  }

/* If TLS is available on this connection, whether continued or not, attempt to
start up a TLS session, unless the host is in hosts_avoid_tls. If successful,
send another EHLO - the server may give a different answer in secure mode. We
use a separate buffer for reading the response to STARTTLS so that if it is
negative, the original EHLO data is available for subsequent analysis, should
the client not be required to use TLS. If the response is bad, copy the buffer
for error analysis. */

#ifdef SUPPORT_TLS
if (  smtp_peer_options & OPTION_TLS
   && !suppress_tls
   && verify_check_given_host(CUSS &ob->hosts_avoid_tls, sx->conn_args.host) != OK
   && (  !sx->verify
      || verify_check_given_host(CUSS &ob->hosts_verify_avoid_tls, sx->conn_args.host) != OK
   )  )
  {
  uschar buffer2[4096];

  if (smtp_write_command(sx, SCMD_FLUSH, "STARTTLS\r\n") < 0)
    goto SEND_FAILED;

#ifdef EXPERIMENTAL_PIPE_CONNECT
  /* If doing early-pipelining reap the banner and EHLO-response but leave
  the response for the STARTTLS we just sent alone. */

  if (sx->early_pipe_active && sync_responses(sx, 2, 0) != 0)
    {
    HDEBUG(D_transport)
      debug_printf("failed reaping pipelined cmd responses\n");
    goto RESPONSE_FAILED;
    }
#endif

  /* If there is an I/O error, transmission of this message is deferred. If
  there is a temporary rejection of STARRTLS and tls_tempfail_tryclear is
  false, we also defer. However, if there is a temporary rejection of STARTTLS
  and tls_tempfail_tryclear is true, or if there is an outright rejection of
  STARTTLS, we carry on. This means we will try to send the message in clear,
  unless the host is in hosts_require_tls (tested below). */

  if (!smtp_read_response(sx, buffer2, sizeof(buffer2), '2', ob->command_timeout))
    {
    if (  errno != 0
       || buffer2[0] == 0
       || (buffer2[0] == '4' && !ob->tls_tempfail_tryclear)
       )
      {
      Ustrncpy(sx->buffer, buffer2, sizeof(sx->buffer));
      sx->buffer[sizeof(sx->buffer)-1] = '\0';
      goto RESPONSE_FAILED;
      }
    }

  /* STARTTLS accepted: try to negotiate a TLS session. */

  else
  TLS_NEGOTIATE:
    {
    address_item * addr;
    uschar * errstr;
    sx->cctx.tls_ctx = tls_client_start(sx->cctx.sock, sx->conn_args.host,
			    sx->addrlist, sx->conn_args.tblock,
# ifdef SUPPORT_DANE
			     sx->dane ? &tlsa_dnsa : NULL,
# endif
			     &tls_out, &errstr);

    if (!sx->cctx.tls_ctx)
      {
      /* TLS negotiation failed; give an error. From outside, this function may
      be called again to try in clear on a new connection, if the options permit
      it for this host. */
      DEBUG(D_tls) debug_printf("TLS session fail: %s\n", errstr);

# ifdef SUPPORT_DANE
      if (sx->dane)
        {
	log_write(0, LOG_MAIN,
	  "DANE attempt failed; TLS connection to %s [%s]: %s",
	  sx->conn_args.host->name, sx->conn_args.host->address, errstr);
#  ifndef DISABLE_EVENT
	(void) event_raise(sx->conn_args.tblock->event_action,
	  US"dane:fail", US"validation-failure");	/* could do with better detail */
#  endif
	}
# endif

      errno = ERRNO_TLSFAILURE;
      message = string_sprintf("TLS session: %s", errstr);
      sx->send_quit = FALSE;
      goto TLS_FAILED;
      }

    /* TLS session is set up */

    smtp_peer_options_wrap = smtp_peer_options;
    for (addr = sx->addrlist; addr; addr = addr->next)
      if (addr->transport_return == PENDING_DEFER)
        {
        addr->cipher = tls_out.cipher;
        addr->ourcert = tls_out.ourcert;
        addr->peercert = tls_out.peercert;
        addr->peerdn = tls_out.peerdn;
	addr->ocsp = tls_out.ocsp;
        }
    }
  }

/* if smtps, we'll have smtp_command set to something else; always safe to
reset it here. */
smtp_command = big_buffer;

/* If we started TLS, redo the EHLO/LHLO exchange over the secure channel. If
helo_data is null, we are dealing with a connection that was passed from
another process, and so we won't have expanded helo_data above. We have to
expand it here. $sending_ip_address and $sending_port are set up right at the
start of the Exim process (in exim.c). */

if (tls_out.active.sock >= 0)
  {
  uschar * greeting_cmd;

  if (!sx->helo_data && !(sx->helo_data = expand_string(ob->helo_data)))
    {
    uschar *message = string_sprintf("failed to expand helo_data: %s",
      expand_string_message);
    set_errno_nohost(sx->addrlist, ERRNO_EXPANDFAIL, message, DEFER, FALSE);
    yield = DEFER;
    goto SEND_QUIT;
    }

#ifdef EXPERIMENTAL_PIPE_CONNECT
  /* For SMTPS there is no cleartext early-pipe; use the crypted permission bit.
  We're unlikely to get the group sent and delivered before the server sends its
  banner, but it's still worth sending as a group.
  For STARTTLS allow for cleartext early-pipe but no crypted early-pipe, but not
  the reverse.  */

  if (sx->smtps ? sx->early_pipe_ok : sx->early_pipe_active)
    {
    sx->peer_offered = sx->ehlo_resp.crypted_features;
    if ((sx->early_pipe_active =
	 !!(sx->ehlo_resp.crypted_features & OPTION_EARLY_PIPE)))
      DEBUG(D_transport) debug_printf("Using cached crypted PIPE_CONNECT\n");
    }
#endif

  /* For SMTPS we need to wait for the initial OK response. */
  if (sx->smtps)
#ifdef EXPERIMENTAL_PIPE_CONNECT
    if (sx->early_pipe_active)
      {
      sx->pending_BANNER = TRUE;
      sx->outblock.cmd_count = 1;
      }
    else
#endif
      if (!smtp_reap_banner(sx))
	goto RESPONSE_FAILED;

  if (sx->lmtp)
    greeting_cmd = US"LHLO";
  else if (sx->esmtp)
    greeting_cmd = US"EHLO";
  else
    {
    greeting_cmd = US"HELO";
    DEBUG(D_transport)
      debug_printf("not sending EHLO (host matches hosts_avoid_esmtp)\n");
    }

  if (smtp_write_command(sx,
#ifdef EXPERIMENTAL_PIPE_CONNECT
	sx->early_pipe_active ? SCMD_BUFFER :
#endif
	  SCMD_FLUSH,
	"%s %s\r\n", greeting_cmd, sx->helo_data) < 0)
    goto SEND_FAILED;

#ifdef EXPERIMENTAL_PIPE_CONNECT
  if (sx->early_pipe_active)
    sx->pending_EHLO = TRUE;
  else
#endif
    {
    if (!smtp_reap_ehlo(sx))
      goto RESPONSE_FAILED;
    smtp_peer_options = 0;
    }
  }

/* If the host is required to use a secure channel, ensure that we
have one. */

else if (  sx->smtps
# ifdef SUPPORT_DANE
	|| sx->dane
# endif
# ifdef EXPERIMENTAL_REQUIRETLS
	|| tls_requiretls & REQUIRETLS_MSG
# endif
	|| verify_check_given_host(CUSS &ob->hosts_require_tls, sx->conn_args.host) == OK
	)
  {
  errno =
# ifdef EXPERIMENTAL_REQUIRETLS
      tls_requiretls & REQUIRETLS_MSG ? ERRNO_REQUIRETLS :
# endif
      ERRNO_TLSREQUIRED;
  message = string_sprintf("a TLS session is required, but %s",
    smtp_peer_options & OPTION_TLS
    ? "an attempt to start TLS failed" : "the server did not offer TLS support");
# if defined(SUPPORT_DANE) && !defined(DISABLE_EVENT)
  if (sx->dane)
    (void) event_raise(sx->conn_args.tblock->event_action, US"dane:fail",
      smtp_peer_options & OPTION_TLS
      ? US"validation-failure"		/* could do with better detail */
      : US"starttls-not-supported");
# endif
  goto TLS_FAILED;
  }
#endif	/*SUPPORT_TLS*/

/* If TLS is active, we have just started it up and re-done the EHLO command,
so its response needs to be analyzed. If TLS is not active and this is a
continued session down a previously-used socket, we haven't just done EHLO, so
we skip this. */

if (continue_hostname == NULL
#ifdef SUPPORT_TLS
    || tls_out.active.sock >= 0
#endif
    )
  {
  if (sx->esmtp || sx->lmtp)
    {
#ifdef EXPERIMENTAL_PIPE_CONNECT
  if (!sx->early_pipe_active)
#endif
    {
    sx->peer_offered = ehlo_response(sx->buffer,
	0 /* no TLS */
#ifdef EXPERIMENTAL_PIPE_CONNECT
	| (sx->lmtp && ob->lmtp_ignore_quota ? OPTION_IGNQ : 0)
	| OPTION_DSN | OPTION_PIPE | OPTION_SIZE
	| OPTION_CHUNKING | OPTION_PRDR | OPTION_UTF8 | OPTION_REQUIRETLS
	| (tls_out.active.sock >= 0 ? OPTION_EARLY_PIPE : 0) /* not for lmtp */

#else

	| (sx->lmtp && ob->lmtp_ignore_quota ? OPTION_IGNQ : 0)
	| OPTION_CHUNKING
	| OPTION_PRDR
# ifdef SUPPORT_I18N
	| (sx->addrlist->prop.utf8_msg ? OPTION_UTF8 : 0)
	  /*XXX if we hand peercaps on to continued-conn processes,
		must not depend on this addr */
# endif
	| OPTION_DSN
	| OPTION_PIPE
	| (ob->size_addition >= 0 ? OPTION_SIZE : 0)
# if defined(SUPPORT_TLS) && defined(EXPERIMENTAL_REQUIRETLS)
	| (tls_requiretls & REQUIRETLS_MSG ? OPTION_REQUIRETLS : 0)
# endif
#endif
      );
#ifdef EXPERIMENTAL_PIPE_CONNECT
    if (tls_out.active.sock >= 0)
      sx->ehlo_resp.crypted_features = sx->peer_offered;
#endif
    }

    /* Set for IGNOREQUOTA if the response to LHLO specifies support and the
    lmtp_ignore_quota option was set. */

    sx->igquotstr = sx->peer_offered & OPTION_IGNQ ? US" IGNOREQUOTA" : US"";

    /* If the response to EHLO specified support for the SIZE parameter, note
    this, provided size_addition is non-negative. */

    smtp_peer_options |= sx->peer_offered & OPTION_SIZE;

    /* Note whether the server supports PIPELINING. If hosts_avoid_esmtp matched
    the current host, esmtp will be false, so PIPELINING can never be used. If
    the current host matches hosts_avoid_pipelining, don't do it. */

    if (  sx->peer_offered & OPTION_PIPE
       && verify_check_given_host(CUSS &ob->hosts_avoid_pipelining, sx->conn_args.host) != OK)
      smtp_peer_options |= OPTION_PIPE;

    DEBUG(D_transport) debug_printf("%susing PIPELINING\n",
      smtp_peer_options & OPTION_PIPE ? "" : "not ");

    if (  sx->peer_offered & OPTION_CHUNKING
       && verify_check_given_host(CUSS &ob->hosts_try_chunking, sx->conn_args.host) != OK)
      sx->peer_offered &= ~OPTION_CHUNKING;

    if (sx->peer_offered & OPTION_CHUNKING)
      DEBUG(D_transport) debug_printf("CHUNKING usable\n");

#ifndef DISABLE_PRDR
    if (  sx->peer_offered & OPTION_PRDR
       && verify_check_given_host(CUSS &ob->hosts_try_prdr, sx->conn_args.host) != OK)
      sx->peer_offered &= ~OPTION_PRDR;

    if (sx->peer_offered & OPTION_PRDR)
      DEBUG(D_transport) debug_printf("PRDR usable\n");
#endif

    /* Note if the server supports DSN */
    smtp_peer_options |= sx->peer_offered & OPTION_DSN;
    DEBUG(D_transport) debug_printf("%susing DSN\n",
			sx->peer_offered & OPTION_DSN ? "" : "not ");

#if defined(SUPPORT_TLS) && defined(EXPERIMENTAL_REQUIRETLS)
    if (sx->peer_offered & OPTION_REQUIRETLS)
      {
      smtp_peer_options |= OPTION_REQUIRETLS;
      DEBUG(D_transport) debug_printf(
	tls_requiretls & REQUIRETLS_MSG
	? "using REQUIRETLS\n" : "REQUIRETLS offered\n");
      }
#endif

#ifdef EXPERIMENTAL_PIPE_CONNECT
    if (  sx->early_pipe_ok
       && !sx->early_pipe_active
       && tls_out.active.sock >= 0
       && smtp_peer_options & OPTION_PIPE
       && ( sx->ehlo_resp.cleartext_features | sx->ehlo_resp.crypted_features)
	  & OPTION_EARLY_PIPE)
      {
      DEBUG(D_transport) debug_printf("PIPE_CONNECT usable in future for this IP\n");
      sx->ehlo_resp.crypted_auths = study_ehlo_auths(sx);
      write_ehlo_cache_entry(sx);
      }
#endif

    /* Note if the response to EHLO specifies support for the AUTH extension.
    If it has, check that this host is one we want to authenticate to, and do
    the business. The host name and address must be available when the
    authenticator's client driver is running. */

    switch (yield = smtp_auth(sx))
      {
      default:		goto SEND_QUIT;
      case OK:		break;
      case FAIL_SEND:	goto SEND_FAILED;
      case FAIL:	goto RESPONSE_FAILED;
      }
    }
  }
sx->pipelining_used = pipelining_active = !!(smtp_peer_options & OPTION_PIPE);

/* The setting up of the SMTP call is now complete. Any subsequent errors are
message-specific. */

sx->setting_up = FALSE;

#ifdef SUPPORT_I18N
if (sx->addrlist->prop.utf8_msg)
  {
  uschar * s;

  /* If the transport sets a downconversion mode it overrides any set by ACL
  for the message. */

  if ((s = ob->utf8_downconvert))
    {
    if (!(s = expand_string(s)))
      {
      message = string_sprintf("failed to expand utf8_downconvert: %s",
        expand_string_message);
      set_errno_nohost(sx->addrlist, ERRNO_EXPANDFAIL, message, DEFER, FALSE);
      yield = DEFER;
      goto SEND_QUIT;
      }
    switch (*s)
      {
      case '1':	sx->addrlist->prop.utf8_downcvt = TRUE;
		sx->addrlist->prop.utf8_downcvt_maybe = FALSE;
		break;
      case '0':	sx->addrlist->prop.utf8_downcvt = FALSE;
		sx->addrlist->prop.utf8_downcvt_maybe = FALSE;
		break;
      case '-':	if (s[1] == '1')
		  {
		  sx->addrlist->prop.utf8_downcvt = FALSE;
		  sx->addrlist->prop.utf8_downcvt_maybe = TRUE;
		  }
		break;
      }
    }

  sx->utf8_needed = !sx->addrlist->prop.utf8_downcvt
		    && !sx->addrlist->prop.utf8_downcvt_maybe;
  DEBUG(D_transport) if (!sx->utf8_needed)
    debug_printf("utf8: %s downconvert\n",
      sx->addrlist->prop.utf8_downcvt ? "mandatory" : "optional");
  }

/* If this is an international message we need the host to speak SMTPUTF8 */
if (sx->utf8_needed && !(sx->peer_offered & OPTION_UTF8))
  {
  errno = ERRNO_UTF8_FWD;
  goto RESPONSE_FAILED;
  }
#endif	/*SUPPORT_I18N*/

#if defined(SUPPORT_TLS) && defined(EXPERIMENTAL_REQUIRETLS)
  /*XXX should tls_requiretls actually be per-addr? */

if (  tls_requiretls & REQUIRETLS_MSG
   && !(sx->peer_offered & OPTION_REQUIRETLS)
   )
  {
  sx->setting_up = TRUE;
  errno = ERRNO_REQUIRETLS;
  message = US"REQUIRETLS support is required from the server"
    " but it was not offered";
  DEBUG(D_transport) debug_printf("%s\n", message);
  goto TLS_FAILED;
  }
#endif

return OK;


  {
  int code;

  RESPONSE_FAILED:
    message = NULL;
    sx->send_quit = check_response(sx->conn_args.host, &errno, sx->addrlist->more_errno,
      sx->buffer, &code, &message, &pass_message);
    yield = DEFER;
    goto FAILED;

  SEND_FAILED:
    code = '4';
    message = US string_sprintf("send() to %s [%s] failed: %s",
      sx->conn_args.host->name, sx->conn_args.host->address, strerror(errno));
    sx->send_quit = FALSE;
    yield = DEFER;
    goto FAILED;

  EHLOHELO_FAILED:
    code = '4';
    message = string_sprintf("Remote host closed connection in response to %s"
      " (EHLO response was: %s)", smtp_command, sx->buffer);
    sx->send_quit = FALSE;
    yield = DEFER;
    goto FAILED;

  /* This label is jumped to directly when a TLS negotiation has failed,
  or was not done for a host for which it is required. Values will be set
  in message and errno, and setting_up will always be true. Treat as
  a temporary error. */

#ifdef SUPPORT_TLS
  TLS_FAILED:
# ifdef EXPERIMENTAL_REQUIRETLS
    if (errno == ERRNO_REQUIRETLS)
      code = '5', yield = FAIL;
      /*XXX DSN will be labelled 500; prefer 530 5.7.4 */
    else
# endif
      code = '4', yield = DEFER;
    goto FAILED;
#endif

  /* The failure happened while setting up the call; see if the failure was
  a 5xx response (this will either be on connection, or following HELO - a 5xx
  after EHLO causes it to try HELO). If so, and there are no more hosts to try,
  fail all addresses, as this host is never going to accept them. For other
  errors during setting up (timeouts or whatever), defer all addresses, and
  yield DEFER, so that the host is not tried again for a while.

  XXX This peeking for another host feels like a layering violation. We want
  to note the host as unusable, but down here we shouldn't know if this was
  the last host to try for the addr(list).  Perhaps the upper layer should be
  the one to do set_errno() ?  The problem is that currently the addr is where
  errno etc. are stashed, but until we run out of hosts to try the errors are
  host-specific.  Maybe we should enhance the host_item definition? */

FAILED:
  sx->ok = FALSE;                /* For when reached by GOTO */
  set_errno(sx->addrlist, errno, message,
	    sx->conn_args.host->next
	    ? DEFER
	    : code == '5'
#ifdef SUPPORT_I18N
			|| errno == ERRNO_UTF8_FWD
#endif
	    ? FAIL : DEFER,
	    pass_message, sx->conn_args.host
#ifdef EXPERIMENTAL_DSN_INFO
	    , sx->smtp_greeting, sx->helo_response
#endif
	    );
  }


SEND_QUIT:

if (sx->send_quit)
  (void)smtp_write_command(sx, SCMD_FLUSH, "QUIT\r\n");

#ifdef SUPPORT_TLS
if (sx->cctx.tls_ctx)
  {
  tls_close(sx->cctx.tls_ctx, TLS_SHUTDOWN_NOWAIT);
  sx->cctx.tls_ctx = NULL;
  }
#endif

/* Close the socket, and return the appropriate value, first setting
works because the NULL setting is passed back to the calling process, and
remote_max_parallel is forced to 1 when delivering over an existing connection,
*/

HDEBUG(D_transport|D_acl|D_v) debug_printf_indent("  SMTP(close)>>\n");
if (sx->send_quit)
  {
  shutdown(sx->cctx.sock, SHUT_WR);
  if (fcntl(sx->cctx.sock, F_SETFL, O_NONBLOCK) == 0)
    for (rc = 16; read(sx->cctx.sock, sx->inbuffer, sizeof(sx->inbuffer)) > 0 && rc > 0;)
      rc--;				/* drain socket */
  sx->send_quit = FALSE;
  }
(void)close(sx->cctx.sock);
sx->cctx.sock = -1;

#ifndef DISABLE_EVENT
(void) event_raise(sx->conn_args.tblock->event_action, US"tcp:close", NULL);
#endif

continue_transport = NULL;
continue_hostname = NULL;
return yield;
}




/* Create the string of options that will be appended to the MAIL FROM:
in the connection context buffer */

static int
build_mailcmd_options(smtp_context * sx, address_item * addrlist)
{
uschar * p = sx->buffer;
address_item * addr;
int address_count;

*p = 0;

/* If we know the receiving MTA supports the SIZE qualification, and we know it,
send it, adding something to the message size to allow for imprecision
and things that get added en route. Exim keeps the number of lines
in a message, so we can give an accurate value for the original message, but we
need some additional to handle added headers. (Double "." characters don't get
included in the count.) */

if (  message_size > 0
   && sx->peer_offered & OPTION_SIZE && !(sx->avoid_option & OPTION_SIZE))
  {
/*XXX problem here under spool_files_wireformat?
Or just forget about lines?  Or inflate by a fixed proportion? */

  sprintf(CS p, " SIZE=%d", message_size+message_linecount+(SOB sx->conn_args.ob)->size_addition);
  while (*p) p++;
  }

#ifndef DISABLE_PRDR
/* If it supports Per-Recipient Data Responses, and we have more than one recipient,
request that */

sx->prdr_active = FALSE;
if (sx->peer_offered & OPTION_PRDR)
  for (addr = addrlist; addr; addr = addr->next)
    if (addr->transport_return == PENDING_DEFER)
      {
      for (addr = addr->next; addr; addr = addr->next)
        if (addr->transport_return == PENDING_DEFER)
	  {			/* at least two recipients to send */
	  sx->prdr_active = TRUE;
	  sprintf(CS p, " PRDR"); p += 5;
	  break;
	  }
      break;
      }
#endif

#ifdef SUPPORT_I18N
/* If it supports internationalised messages, and this meesage need that,
request it */

if (  sx->peer_offered & OPTION_UTF8
   && addrlist->prop.utf8_msg
   && !addrlist->prop.utf8_downcvt
   )
  Ustrcpy(p, " SMTPUTF8"), p += 9;
#endif

#if defined(SUPPORT_TLS) && defined(EXPERIMENTAL_REQUIRETLS)
if (tls_requiretls & REQUIRETLS_MSG)
  Ustrcpy(p, " REQUIRETLS") , p += 11;
#endif

/* check if all addresses have DSN-lasthop flag; do not send RET and ENVID if so */
for (sx->dsn_all_lasthop = TRUE, addr = addrlist, address_count = 0;
     addr && address_count < sx->max_rcpt;
     addr = addr->next) if (addr->transport_return == PENDING_DEFER)
  {
  address_count++;
  if (!(addr->dsn_flags & rf_dsnlasthop))
    {
    sx->dsn_all_lasthop = FALSE;
    break;
    }
  }

/* Add any DSN flags to the mail command */

if (sx->peer_offered & OPTION_DSN && !sx->dsn_all_lasthop)
  {
  if (dsn_ret == dsn_ret_hdrs)
    { Ustrcpy(p, " RET=HDRS"); p += 9; }
  else if (dsn_ret == dsn_ret_full)
    { Ustrcpy(p, " RET=FULL"); p += 9; }

  if (dsn_envid)
    {
    string_format(p, sizeof(sx->buffer) - (p-sx->buffer), " ENVID=%s", dsn_envid);
    while (*p) p++;
    }
  }

/* If an authenticated_sender override has been specified for this transport
instance, expand it. If the expansion is forced to fail, and there was already
an authenticated_sender for this message, the original value will be used.
Other expansion failures are serious. An empty result is ignored, but there is
otherwise no check - this feature is expected to be used with LMTP and other
cases where non-standard addresses (e.g. without domains) might be required. */

if (smtp_mail_auth_str(p, sizeof(sx->buffer) - (p-sx->buffer), addrlist, sx->conn_args.ob))
  return ERROR;

return OK;
}


static void
build_rcptcmd_options(smtp_context * sx, const address_item * addr)
{
uschar * p = sx->buffer;
*p = 0;

/* Add any DSN flags to the rcpt command */

if (sx->peer_offered & OPTION_DSN && !(addr->dsn_flags & rf_dsnlasthop))
  {
  if (addr->dsn_flags & rf_dsnflags)
    {
    int i;
    BOOL first = TRUE;

    Ustrcpy(p, " NOTIFY=");
    while (*p) p++;
    for (i = 0; i < nelem(rf_list); i++) if (addr->dsn_flags & rf_list[i])
      {
      if (!first) *p++ = ',';
      first = FALSE;
      Ustrcpy(p, rf_names[i]);
      while (*p) p++;
      }
    }

  if (addr->dsn_orcpt)
    {
    string_format(p, sizeof(sx->buffer) - (p-sx->buffer), " ORCPT=%s",
      addr->dsn_orcpt);
    while (*p) p++;
    }
  }
}



/*
Return:
 0	good, rcpt results in addr->transport_return (PENDING_OK, DEFER, FAIL)
 -1	MAIL response error
 -2	any non-MAIL read i/o error
 -3	non-MAIL response timeout
 -4	internal error; channel still usable
 -5	transmit failed
 */

int
smtp_write_mail_and_rcpt_cmds(smtp_context * sx, int * yield)
{
address_item * addr;
int address_count;
int rc;

if (build_mailcmd_options(sx, sx->first_addr) != OK)
  {
  *yield = ERROR;
  return -4;
  }

/* From here until we send the DATA command, we can make use of PIPELINING
if the server host supports it. The code has to be able to check the responses
at any point, for when the buffer fills up, so we write it totally generally.
When PIPELINING is off, each command written reports that it has flushed the
buffer. */

sx->pending_MAIL = TRUE;     /* The block starts with MAIL */

  {
  uschar * s = sx->from_addr;
#ifdef SUPPORT_I18N
  uschar * errstr = NULL;

  /* If we must downconvert, do the from-address here.  Remember we had to
  for the to-addresses (done below), and also (ugly) for re-doing when building
  the delivery log line. */

  if (  sx->addrlist->prop.utf8_msg
     && (sx->addrlist->prop.utf8_downcvt || !(sx->peer_offered & OPTION_UTF8))
     )
    {
    if (s = string_address_utf8_to_alabel(s, &errstr), errstr)
      {
      set_errno_nohost(sx->addrlist, ERRNO_EXPANDFAIL, errstr, DEFER, FALSE);
      *yield = ERROR;
      return -4;
      }
    setflag(sx->addrlist, af_utf8_downcvt);
    }
#endif

  rc = smtp_write_command(sx, pipelining_active ? SCMD_BUFFER : SCMD_FLUSH,
	  "MAIL FROM:<%s>%s\r\n", s, sx->buffer);
  }

mail_command = string_copy(big_buffer);  /* Save for later error message */

switch(rc)
  {
  case -1:                /* Transmission error */
    return -5;

  case +1:                /* Cmd was sent */
    if (!smtp_read_response(sx, sx->buffer, sizeof(sx->buffer), '2',
       (SOB sx->conn_args.ob)->command_timeout))
      {
      if (errno == 0 && sx->buffer[0] == '4')
	{
	errno = ERRNO_MAIL4XX;
	sx->addrlist->more_errno |= ((sx->buffer[1] - '0')*10 + sx->buffer[2] - '0') << 8;
	}
      return -1;
      }
    sx->pending_MAIL = FALSE;
    break;

  /* otherwise zero: command queued for pipeline */
  }

/* Pass over all the relevant recipient addresses for this host, which are the
ones that have status PENDING_DEFER. If we are using PIPELINING, we can send
several before we have to read the responses for those seen so far. This
checking is done by a subroutine because it also needs to be done at the end.
Send only up to max_rcpt addresses at a time, leaving next_addr pointing to
the next one if not all are sent.

In the MUA wrapper situation, we want to flush the PIPELINING buffer for the
last address because we want to abort if any recipients have any kind of
problem, temporary or permanent. We know that all recipient addresses will have
the PENDING_DEFER status, because only one attempt is ever made, and we know
that max_rcpt will be large, so all addresses will be done at once.

For verify we flush the pipeline after any (the only) rcpt address. */

for (addr = sx->first_addr, address_count = 0;
     addr  &&  address_count < sx->max_rcpt;
     addr = addr->next) if (addr->transport_return == PENDING_DEFER)
  {
  int count;
  BOOL no_flush;
  uschar * rcpt_addr;

  addr->dsn_aware = sx->peer_offered & OPTION_DSN
    ? dsn_support_yes : dsn_support_no;

  address_count++;
  no_flush = pipelining_active && !sx->verify
	  && (!mua_wrapper || addr->next && address_count < sx->max_rcpt);

  build_rcptcmd_options(sx, addr);

  /* Now send the RCPT command, and process outstanding responses when
  necessary. After a timeout on RCPT, we just end the function, leaving the
  yield as OK, because this error can often mean that there is a problem with
  just one address, so we don't want to delay the host. */

  rcpt_addr = transport_rcpt_address(addr, sx->conn_args.tblock->rcpt_include_affixes);

#ifdef SUPPORT_I18N
  if (  testflag(sx->addrlist, af_utf8_downcvt)
     && !(rcpt_addr = string_address_utf8_to_alabel(rcpt_addr, NULL))
     )
    {
    /*XXX could we use a per-address errstr here? Not fail the whole send? */
    errno = ERRNO_EXPANDFAIL;
    return -5;		/*XXX too harsh? */
    }
#endif

  count = smtp_write_command(sx, no_flush ? SCMD_BUFFER : SCMD_FLUSH,
    "RCPT TO:<%s>%s%s\r\n", rcpt_addr, sx->igquotstr, sx->buffer);

  if (count < 0) return -5;
  if (count > 0)
    {
    switch(sync_responses(sx, count, 0))
      {
      case 3: sx->ok = TRUE;			/* 2xx & 5xx => OK & progress made */
      case 2: sx->completed_addr = TRUE;	/* 5xx (only) => progress made */
	      break;

      case 1: sx->ok = TRUE;			/* 2xx (only) => OK, but if LMTP, */
	      if (!sx->lmtp)			/*  can't tell about progress yet */
		sx->completed_addr = TRUE;
      case 0:					/* No 2xx or 5xx, but no probs */
	      break;

      case -1: return -3;			/* Timeout on RCPT */
      case -2: return -2;			/* non-MAIL read i/o error */
      default: return -1;			/* any MAIL error */

#ifdef EXPERIMENTAL_PIPE_CONNECT
      case -4: return -1;			/* non-2xx for pipelined banner or EHLO */
#endif
      }
    sx->pending_MAIL = FALSE;            /* Dealt with MAIL */
    }
  }      /* Loop for next address */

sx->next_addr = addr;
return 0;
}


#ifdef SUPPORT_TLS
/*****************************************************
* Proxy TLS connection for another transport process *
******************************************************/
/*
Close the unused end of the pipe, fork once more, then use the given buffer
as a staging area, and select on both the given fd and the TLS'd client-fd for
data to read (per the coding in ip_recv() and fd_ready() this is legitimate).
Do blocking full-size writes, and reads under a timeout.  Once both input
channels are closed, exit the process.

Arguments:
  ct_ctx	tls context
  buf		space to use for buffering
  bufsiz	size of buffer
  pfd		pipe filedescriptor array; [0] is comms to proxied process
  timeout	per-read timeout, seconds
*/

void
smtp_proxy_tls(void * ct_ctx, uschar * buf, size_t bsize, int * pfd,
  int timeout)
{
fd_set rfds, efds;
int max_fd = MAX(pfd[0], tls_out.active.sock) + 1;
int rc, i, fd_bits, nbytes;

close(pfd[1]);
if ((rc = fork()))
  {
  DEBUG(D_transport) debug_printf("proxy-proc final-pid %d\n", rc);
  _exit(rc < 0 ? EXIT_FAILURE : EXIT_SUCCESS);
  }