Recast more internal string routines to use growable-strings

[exim.git] / src / src / host.c

diff --git a/src/src/host.c b/src/src/host.c
index b5af8f92b01822e45f72943047e8c790c591bbd8..c3694c047b4b399614f6994e1c0ac322979ec7ff 100644 (file)
--- a/src/src/host.c
+++ b/src/src/host.c
@@ -2,7 +2,7 @@
 *     Exim - an Internet mail transport agent    *
 *************************************************/
 
 *     Exim - an Internet mail transport agent    *
 *************************************************/
 

-/* Copyright (c) University of Cambridge 1995 - 2016 */
+/* Copyright (c) University of Cambridge 1995 - 2018 */

 /* See the file NOTICE for conditions of use and distribution. */
 
 /* Functions for finding hosts, either by gethostbyname(), gethostbyaddr(), or
 /* See the file NOTICE for conditions of use and distribution. */
 
 /* Functions for finding hosts, either by gethostbyname(), gethostbyaddr(), or


@@ -84,7 +84,7 @@ if (limit < 1)
   return 0;
 if (random_seed == 0)
   {
   return 0;
 if (random_seed == 0)
   {

-  if (running_in_test_harness) random_seed = 42; else
+  if (f.running_in_test_harness) random_seed = 42; else

     {
     int p = (int)getpid();
     random_seed = (int)time(NULL) ^ ((p << 16) | p);
     {
     int p = (int)getpid();
     random_seed = (int)time(NULL) ^ ((p << 16) | p);


@@ -520,7 +520,9 @@ There wouldn't be two different variables if I had got all this right in the
 first place.
 
 Because this data may survive over more than one incoming SMTP message, it has
 first place.
 
 Because this data may survive over more than one incoming SMTP message, it has

-to be in permanent store.
+to be in permanent store.  However, STARTTLS has to be forgotten and redone
+on a multi-message conn, so this will be called once per message then.  Hence
+we use malloc, so we can free.

 
 Arguments:  none
 Returns:    nothing
 
 Arguments:  none
 Returns:    nothing


@@ -530,13 +532,12 @@ void
 host_build_sender_fullhost(void)
 {
 BOOL show_helo = TRUE;
 host_build_sender_fullhost(void)
 {
 BOOL show_helo = TRUE;

-uschar *address;
+uschar * address, * fullhost, * rcvhost, * reset_point;

 int len;
 int len;

-int old_pool = store_pool;

 
 

-if (sender_host_address == NULL) return;
+if (!sender_host_address) return;

 
 

-store_pool = POOL_PERM;
+reset_point = store_get(0);

 
 /* Set up address, with or without the port. After discussion, it seems that
 the only format that doesn't cause trouble is [aaaa]:pppp. However, we can't
 
 /* Set up address, with or without the port. After discussion, it seems that
 the only format that doesn't cause trouble is [aaaa]:pppp. However, we can't


@@ -549,7 +550,7 @@ if (!LOGGING(incoming_port) || sender_host_port <= 0)
 
 /* If there's no EHLO/HELO data, we can't show it. */
 
 
 /* If there's no EHLO/HELO data, we can't show it. */
 

-if (sender_helo_name == NULL) show_helo = FALSE;
+if (!sender_helo_name) show_helo = FALSE;

 
 /* If HELO/EHLO was followed by an IP literal, it's messy because of two
 features of IPv6. Firstly, there's the "IPv6:" prefix (Exim is liberal and
 
 /* If HELO/EHLO was followed by an IP literal, it's messy because of two
 features of IPv6. Firstly, there's the "IPv6:" prefix (Exim is liberal and


@@ -586,46 +587,40 @@ else if (sender_helo_name[0] == '[' &&
 
 /* Host name is not verified */
 
 
 /* Host name is not verified */
 

-if (sender_host_name == NULL)
+if (!sender_host_name)

   {
   uschar *portptr = Ustrstr(address, "]:");
   {
   uschar *portptr = Ustrstr(address, "]:");

-  int size = 0;
-  int ptr = 0;
+  gstring * g;

   int adlen;    /* Sun compiler doesn't like ++ in initializers */
 
   int adlen;    /* Sun compiler doesn't like ++ in initializers */
 

-  adlen = (portptr == NULL)? Ustrlen(address) : (++portptr - address);
-  sender_fullhost = (sender_helo_name == NULL)? address :
-    string_sprintf("(%s) %s", sender_helo_name, address);
+  adlen = portptr ? (++portptr - address) : Ustrlen(address);
+  fullhost = sender_helo_name
+    ? string_sprintf("(%s) %s", sender_helo_name, address)
+    : address;

 
 

-  sender_rcvhost = string_catn(NULL, &size, &ptr, address, adlen);
+  g = string_catn(NULL, address, adlen);

 
 

-  if (sender_ident != NULL || show_helo || portptr != NULL)
+  if (sender_ident || show_helo || portptr)

     {
     int firstptr;
     {
     int firstptr;

-    sender_rcvhost = string_catn(sender_rcvhost, &size, &ptr, US" (", 2);
-    firstptr = ptr;
+    g = string_catn(g, US" (", 2);
+    firstptr = g->ptr;

 
 

-    if (portptr != NULL)
-      sender_rcvhost = string_append(sender_rcvhost, &size, &ptr, 2, US"port=",
-        portptr + 1);
+    if (portptr)
+      g = string_append(g, 2, US"port=", portptr + 1);

 
     if (show_helo)
 
     if (show_helo)

-      sender_rcvhost = string_append(sender_rcvhost, &size, &ptr, 2,
-        (firstptr == ptr)? US"helo=" : US" helo=", sender_helo_name);
+      g = string_append(g, 2,
+        firstptr == g->ptr ? US"helo=" : US" helo=", sender_helo_name);

 
 

-    if (sender_ident != NULL)
-      sender_rcvhost = string_append(sender_rcvhost, &size, &ptr, 2,
-        (firstptr == ptr)? US"ident=" : US" ident=", sender_ident);
+    if (sender_ident)
+      g = string_append(g, 2,
+        firstptr == g->ptr ? US"ident=" : US" ident=", sender_ident);

 
 

-    sender_rcvhost = string_catn(sender_rcvhost, &size, &ptr, US")", 1);
+    g = string_catn(g, US")", 1);

     }
 
     }
 

-  sender_rcvhost[ptr] = 0;   /* string_cat() always leaves room */
-
-  /* Release store, because string_cat allocated a minimum of 100 bytes that
-  are rarely completely used. */
-
-  store_reset(sender_rcvhost + ptr + 1);
+  rcvhost = string_from_gstring(g);

   }
 
 /* Host name is known and verified. Unless we've already found that the HELO
   }
 
 /* Host name is known and verified. Unless we've already found that the HELO


@@ -638,25 +633,30 @@ else
 
   if (show_helo)
     {
 
   if (show_helo)
     {

-    sender_fullhost = string_sprintf("%s (%s) %s", sender_host_name,
+    fullhost = string_sprintf("%s (%s) %s", sender_host_name,

       sender_helo_name, address);
       sender_helo_name, address);

-    sender_rcvhost = (sender_ident == NULL)?
-      string_sprintf("%s (%s helo=%s)", sender_host_name,
-        address, sender_helo_name) :
-      string_sprintf("%s\n\t(%s helo=%s ident=%s)", sender_host_name,
-        address, sender_helo_name, sender_ident);
+    rcvhost = sender_ident
+      ?  string_sprintf("%s\n\t(%s helo=%s ident=%s)", sender_host_name,
+        address, sender_helo_name, sender_ident)
+      : string_sprintf("%s (%s helo=%s)", sender_host_name,
+        address, sender_helo_name);

     }
   else
     {
     }
   else
     {

-    sender_fullhost = string_sprintf("%s %s", sender_host_name, address);
-    sender_rcvhost = (sender_ident == NULL)?
-      string_sprintf("%s (%s)", sender_host_name, address) :
-      string_sprintf("%s (%s ident=%s)", sender_host_name, address,
-        sender_ident);
+    fullhost = string_sprintf("%s %s", sender_host_name, address);
+    rcvhost = sender_ident
+      ?  string_sprintf("%s (%s ident=%s)", sender_host_name, address,
+        sender_ident)
+      : string_sprintf("%s (%s)", sender_host_name, address);

     }
   }
 
     }
   }
 

-store_pool = old_pool;
+if (sender_fullhost) store_free(sender_fullhost);
+sender_fullhost = string_copy_malloc(fullhost);
+if (sender_rcvhost) store_free(sender_rcvhost);
+sender_rcvhost = string_copy_malloc(rcvhost);
+
+store_reset(reset_point);

 
 DEBUG(D_host_lookup) debug_printf("sender_fullhost = %s\n", sender_fullhost);
 DEBUG(D_host_lookup) debug_printf("sender_rcvhost = %s\n", sender_rcvhost);
 
 DEBUG(D_host_lookup) debug_printf("sender_fullhost = %s\n", sender_fullhost);
 DEBUG(D_host_lookup) debug_printf("sender_rcvhost = %s\n", sender_rcvhost);


@@ -737,16 +737,14 @@ host_build_ifacelist(const uschar *list, uschar *name)
 {
 int sep = 0;
 uschar *s;
 {
 int sep = 0;
 uschar *s;

-uschar buffer[64];
-ip_address_item *yield = NULL;
-ip_address_item *last = NULL;
-ip_address_item *next;
+ip_address_item * yield = NULL, * last = NULL, * next;

 
 

-while ((s = string_nextinlist(&list, &sep, buffer, sizeof(buffer))) != NULL)
+while ((s = string_nextinlist(&list, &sep, NULL, 0)))

   {
   int ipv;
   int port = host_address_extract_port(s);            /* Leaves just the IP address */
   {
   int ipv;
   int port = host_address_extract_port(s);            /* Leaves just the IP address */

-  if ((ipv = string_is_ip_address(s, NULL)) == 0)
+
+  if (!(ipv = string_is_ip_address(s, NULL)))

     log_write(0, LOG_MAIN|LOG_PANIC_DIE, "Malformed IP address \"%s\" in %s",
       s, name);
 
     log_write(0, LOG_MAIN|LOG_PANIC_DIE, "Malformed IP address \"%s\" in %s",
       s, name);
 


@@ -764,7 +762,9 @@ while ((s = string_nextinlist(&list, &sep, buffer, sizeof(buffer))) != NULL)
   next->port = port;
   next->v6_include_v4 = FALSE;
 
   next->port = port;
   next->v6_include_v4 = FALSE;
 

-  if (yield == NULL) yield = last = next; else
+  if (!yield)
+    yield = last = next;
+  else

     {
     last->next = next;
     last = next;
     {
     last->next = next;
     last = next;


@@ -919,21 +919,21 @@ if (type < 0)
   if (family == AF_INET6)
     {
     struct sockaddr_in6 *sk = (struct sockaddr_in6 *)arg;
   if (family == AF_INET6)
     {
     struct sockaddr_in6 *sk = (struct sockaddr_in6 *)arg;

-    yield = (uschar *)inet_ntop(family, &(sk->sin6_addr), CS addr_buffer,
+    yield = US inet_ntop(family, &(sk->sin6_addr), CS addr_buffer,

       sizeof(addr_buffer));
     if (portptr != NULL) *portptr = ntohs(sk->sin6_port);
     }
   else
     {
     struct sockaddr_in *sk = (struct sockaddr_in *)arg;
       sizeof(addr_buffer));
     if (portptr != NULL) *portptr = ntohs(sk->sin6_port);
     }
   else
     {
     struct sockaddr_in *sk = (struct sockaddr_in *)arg;

-    yield = (uschar *)inet_ntop(family, &(sk->sin_addr), CS addr_buffer,
+    yield = US inet_ntop(family, &(sk->sin_addr), CS addr_buffer,

       sizeof(addr_buffer));
     if (portptr != NULL) *portptr = ntohs(sk->sin_port);
     }
   }
 else
   {
       sizeof(addr_buffer));
     if (portptr != NULL) *portptr = ntohs(sk->sin_port);
     }
   }
 else
   {

-  yield = (uschar *)inet_ntop(type, arg, CS addr_buffer, sizeof(addr_buffer));
+  yield = US inet_ntop(type, arg, CS addr_buffer, sizeof(addr_buffer));

   }
 
 /* If the result is a mapped IPv4 address, show it in V4 format. */
   }
 
 /* If the result is a mapped IPv4 address, show it in V4 format. */


@@ -1160,10 +1160,7 @@ tt--;   /* lose final separator */
 if (mask < 0)
   *tt = 0;
 else
 if (mask < 0)
   *tt = 0;
 else

-  {
-  sprintf(CS tt, "/%d", mask);
-  while (*tt) tt++;
-  }
+  tt += sprintf(CS tt, "/%d", mask);

 
 return tt - buffer;
 }
 
 return tt - buffer;
 }


@@ -1587,7 +1584,7 @@ if (hosts->h_name == NULL || hosts->h_name[0] == 0 || hosts->h_name[0] == '.')
 /* Copy and lowercase the name, which is in static storage in many systems.
 Put it in permanent memory. */
 
 /* Copy and lowercase the name, which is in static storage in many systems.
 Put it in permanent memory. */
 

-s = (uschar *)hosts->h_name;
+s = US hosts->h_name;

 len = Ustrlen(s) + 1;
 t = sender_host_name = store_get_perm(len);
 while (*s != 0) *t++ = tolower(*s++);
 len = Ustrlen(s) + 1;
 t = sender_host_name = store_get_perm(len);
 while (*s != 0) *t++ = tolower(*s++);


@@ -1677,7 +1674,7 @@ HDEBUG(D_host_lookup)
 /* For testing the case when a lookup does not complete, we have a special
 reserved IP address. */
 
 /* For testing the case when a lookup does not complete, we have a special
 reserved IP address. */
 

-if (running_in_test_harness &&
+if (f.running_in_test_harness &&

     Ustrcmp(sender_host_address, "99.99.99.99") == 0)
   {
   HDEBUG(D_host_lookup)
     Ustrcmp(sender_host_address, "99.99.99.99") == 0)
   {
   HDEBUG(D_host_lookup)


@@ -1742,7 +1739,7 @@ while ((ordername = string_nextinlist(&list, &sep, buffer, sizeof(buffer))))
         truncated and dn_expand may fail. */
 
         if (dn_expand(dnsa.answer, dnsa.answer + dnsa.answerlen,
         truncated and dn_expand may fail. */
 
         if (dn_expand(dnsa.answer, dnsa.answer + dnsa.answerlen,

-             (uschar *)(rr->data), (DN_EXPAND_ARG4_TYPE)(s), ssize) < 0)
+             US (rr->data), (DN_EXPAND_ARG4_TYPE)(s), ssize) < 0)

           {
           log_write(0, LOG_MAIN, "host name alias list truncated for %s",
             sender_host_address);
           {
           log_write(0, LOG_MAIN, "host name alias list truncated for %s",
             sender_host_address);


@@ -1799,9 +1796,9 @@ while ((ordername = string_nextinlist(&list, &sep, buffer, sizeof(buffer))))
 /* If we have failed to find a name, return FAIL and log when required.
 NB host_lookup_msg must be in permanent store.  */
 
 /* If we have failed to find a name, return FAIL and log when required.
 NB host_lookup_msg must be in permanent store.  */
 

-if (sender_host_name == NULL)
+if (!sender_host_name)

   {
   {

-  if (host_checking || !log_testing_mode)
+  if (host_checking || !f.log_testing_mode)

     log_write(L_host_lookup_failed, LOG_MAIN, "no host name found for IP "
       "address %s", sender_host_address);
   host_lookup_msg = US" (failed to find host name from IP address)";
     log_write(L_host_lookup_failed, LOG_MAIN, "no host name found for IP "
       "address %s", sender_host_address);
   host_lookup_msg = US" (failed to find host name from IP address)";


@@ -1835,17 +1832,11 @@ for (hname = sender_host_name; hname; hname = *aliases++)
   {
   int rc;
   BOOL ok = FALSE;
   {
   int rc;
   BOOL ok = FALSE;

-  host_item h;
-  dnssec_domains d;
-
-  h.next = NULL;
-  h.name = hname;
-  h.mx = MX_NONE;
-  h.address = NULL;
-  d.request = sender_host_dnssec ? US"*" : NULL;;
-  d.require = NULL;
+  host_item h = { .next = NULL, .name = hname, .mx = MX_NONE, .address = NULL };
+  dnssec_domains d =
+    { .request = sender_host_dnssec ? US"*" : NULL, .require = NULL };

 
 

-  if (  (rc = host_find_bydns(&h, NULL, HOST_FIND_BY_A,
+  if (  (rc = host_find_bydns(&h, NULL, HOST_FIND_BY_A | HOST_FIND_BY_AAAA,

          NULL, NULL, NULL, &d, NULL, NULL)) == HOST_FOUND
      || rc == HOST_FOUND_LOCAL
      )
          NULL, NULL, NULL, &d, NULL, NULL)) == HOST_FOUND
      || rc == HOST_FOUND_LOCAL
      )


@@ -2014,7 +2005,7 @@ lookups here (except when testing standalone). */
 /* Initialize the flag that gets set for DNS syntax check errors, so that the
 interface to this function can be similar to host_find_bydns. */
 
 /* Initialize the flag that gets set for DNS syntax check errors, so that the
 interface to this function can be similar to host_find_bydns. */
 

-host_find_failed_syntax = FALSE;
+f.host_find_failed_syntax = FALSE;

 
 /* Loop to look up both kinds of address in an IPv6 world */
 
 
 /* Loop to look up both kinds of address in an IPv6 world */
 


@@ -2036,7 +2027,7 @@ for (i = 1; i <= times;
   if (slow_lookup_log) time_msec = get_time_in_ms();
 
   #if HAVE_IPV6
   if (slow_lookup_log) time_msec = get_time_in_ms();
 
   #if HAVE_IPV6

-  if (running_in_test_harness)
+  if (f.running_in_test_harness)

     hostdata = host_fake_gethostbyname(host->name, af, &error_num);
   else
     {
     hostdata = host_fake_gethostbyname(host->name, af, &error_num);
   else
     {


@@ -2049,7 +2040,7 @@ for (i = 1; i <= times;
     }
 
   #else    /* not HAVE_IPV6 */
     }
 
   #else    /* not HAVE_IPV6 */

-  if (running_in_test_harness)
+  if (f.running_in_test_harness)

     hostdata = host_fake_gethostbyname(host->name, AF_INET, &error_num);
   else
     {
     hostdata = host_fake_gethostbyname(host->name, AF_INET, &error_num);
   else
     {


@@ -2099,7 +2090,7 @@ for (i = 1; i <= times;
 
   if (hostdata->h_name[0] != 0 &&
       Ustrcmp(host->name, hostdata->h_name) != 0)
 
   if (hostdata->h_name[0] != 0 &&
       Ustrcmp(host->name, hostdata->h_name) != 0)

-    host->name = string_copy_dnsdomain((uschar *)hostdata->h_name);
+    host->name = string_copy_dnsdomain(US hostdata->h_name);

   if (fully_qualified_name != NULL) *fully_qualified_name = host->name;
 
   /* Get the list of addresses. IPv4 and IPv6 addresses can be distinguished
   if (fully_qualified_name != NULL) *fully_qualified_name = host->name;
 
   /* Get the list of addresses. IPv4 and IPv6 addresses can be distinguished


@@ -2174,7 +2165,7 @@ if (host->address == NULL)
 
   HDEBUG(D_host_lookup) debug_printf("%s\n", msg);
   if (temp_error) goto RETURN_AGAIN;
 
   HDEBUG(D_host_lookup) debug_printf("%s\n", msg);
   if (temp_error) goto RETURN_AGAIN;

-  if (host_checking || !log_testing_mode)
+  if (host_checking || !f.log_testing_mode)

     log_write(L_host_lookup_failed, LOG_MAIN, "%s", msg);
   return HOST_FIND_FAILED;
   }
     log_write(L_host_lookup_failed, LOG_MAIN, "%s", msg);
   return HOST_FIND_FAILED;
   }


@@ -2245,9 +2236,7 @@ field set to NULL, fill in its IP address from the DNS. If it is multi-homed,
 create additional host items for the additional addresses, copying all the
 other fields, and randomizing the order.
 
 create additional host items for the additional addresses, copying all the
 other fields, and randomizing the order.
 

-On IPv6 systems, A6 records are sought first (but only if support for A6 is
-configured - they may never become mainstream), then AAAA records are sought,
-and finally A records are sought as well.
+On IPv6 systems, AAAA records are sought first, then A records.

 
 The host name may be changed if the DNS returns a different name - e.g. fully
 qualified or changed via CNAME. If fully_qualified_name is not NULL, dns_lookup
 
 The host name may be changed if the DNS returns a different name - e.g. fully
 qualified or changed via CNAME. If fully_qualified_name is not NULL, dns_lookup


@@ -2270,6 +2259,7 @@ Arguments:
                           to something)
   dnssec_request       if TRUE request the AD bit
   dnssec_require       if TRUE require the AD bit
                           to something)
   dnssec_request       if TRUE request the AD bit
   dnssec_require       if TRUE require the AD bit

+  whichrrs             select ipv4, ipv6 results

 
 Returns:       HOST_FIND_FAILED     couldn't find A record
                HOST_FIND_AGAIN      try again later
 
 Returns:       HOST_FIND_FAILED     couldn't find A record
                HOST_FIND_AGAIN      try again later


@@ -2282,7 +2272,7 @@ static int
 set_address_from_dns(host_item *host, host_item **lastptr,
   const uschar *ignore_target_hosts, BOOL allow_ip,
   const uschar **fully_qualified_name,
 set_address_from_dns(host_item *host, host_item **lastptr,
   const uschar *ignore_target_hosts, BOOL allow_ip,
   const uschar **fully_qualified_name,

-  BOOL dnssec_request, BOOL dnssec_require)
+  BOOL dnssec_request, BOOL dnssec_require, int whichrrs)

 {
 dns_record *rr;
 host_item *thishostlast = NULL;    /* Indicates not yet filled in anything */
 {
 dns_record *rr;
 host_item *thishostlast = NULL;    /* Indicates not yet filled in anything */


@@ -2297,8 +2287,8 @@ those sites that feel they have to flaunt the RFC rules. */
 if (allow_ip && string_is_ip_address(host->name, NULL) != 0)
   {
   #ifndef STAND_ALONE
 if (allow_ip && string_is_ip_address(host->name, NULL) != 0)
   {
   #ifndef STAND_ALONE

-  if (ignore_target_hosts != NULL &&
-        verify_check_this_host(&ignore_target_hosts, NULL, host->name,
+  if (  ignore_target_hosts
+     && verify_check_this_host(&ignore_target_hosts, NULL, host->name,

         host->name, NULL) == OK)
     return HOST_IGNORED;
   #endif
         host->name, NULL) == OK)
     return HOST_IGNORED;
   #endif


@@ -2308,16 +2298,18 @@ if (allow_ip && string_is_ip_address(host->name, NULL) != 0)
   }
 
 /* On an IPv6 system, unless IPv6 is disabled, go round the loop up to twice,
   }
 
 /* On an IPv6 system, unless IPv6 is disabled, go round the loop up to twice,

-looking for AAAA records the first time. However, unless
-doing standalone testing, we force an IPv4 lookup if the domain matches
-dns_ipv4_lookup is set.  On an IPv4 system, go round the
-loop once only, looking only for A records. */
+looking for AAAA records the first time. However, unless doing standalone
+testing, we force an IPv4 lookup if the domain matches dns_ipv4_lookup global.
+On an IPv4 system, go round the loop once only, looking only for A records. */

 
 #if HAVE_IPV6
   #ifndef STAND_ALONE
 
 #if HAVE_IPV6
   #ifndef STAND_ALONE

-    if (disable_ipv6 || (dns_ipv4_lookup != NULL &&
-        match_isinlist(host->name, CUSS &dns_ipv4_lookup, 0, NULL, NULL,
-         MCL_DOMAIN, TRUE, NULL) == OK))
+    if (  disable_ipv6
+       || !(whichrrs & HOST_FIND_BY_AAAA)
+       || (dns_ipv4_lookup
+          && match_isinlist(host->name, CUSS &dns_ipv4_lookup, 0, NULL, NULL,
+             MCL_DOMAIN, TRUE, NULL) == OK)
+       )

       i = 0;    /* look up A records only */
     else
   #endif        /* STAND_ALONE */
       i = 0;    /* look up A records only */
     else
   #endif        /* STAND_ALONE */


@@ -2334,7 +2326,8 @@ for (; i >= 0; i--)
   {
   static int types[] = { T_A, T_AAAA };
   int type = types[i];
   {
   static int types[] = { T_A, T_AAAA };
   int type = types[i];

-  int randoffset = (i == 0)? 500 : 0;  /* Ensures v6 sorts before v4 */
+  int randoffset = i == (whichrrs & HOST_FIND_IPV4_FIRST ? 1 : 0)
+    ? 500 : 0;  /* Ensures v6/4 sort order */

   dns_answer dnsa;
   dns_scan dnss;
 
   dns_answer dnsa;
   dns_scan dnss;
 


@@ -2536,10 +2529,13 @@ Arguments:
   whichrrs              flags indicating which RRs to look for:
                           HOST_FIND_BY_SRV  => look for SRV
                           HOST_FIND_BY_MX   => look for MX
   whichrrs              flags indicating which RRs to look for:
                           HOST_FIND_BY_SRV  => look for SRV
                           HOST_FIND_BY_MX   => look for MX

-                          HOST_FIND_BY_A    => look for A or AAAA
+                          HOST_FIND_BY_A    => look for A
+                          HOST_FIND_BY_AAAA => look for AAAA

                         also flags indicating how the lookup is done
                           HOST_FIND_QUALIFY_SINGLE   ) passed to the
                           HOST_FIND_SEARCH_PARENTS   )   resolver
                         also flags indicating how the lookup is done
                           HOST_FIND_QUALIFY_SINGLE   ) passed to the
                           HOST_FIND_SEARCH_PARENTS   )   resolver

+                         HOST_FIND_IPV4_FIRST => reverse usual result ordering
+                         HOST_FIND_IPV4_ONLY  => MX results elide ipv6

   srv_service           when SRV used, the service name
   srv_fail_domains      DNS errors for these domains => assume nonexist
   mx_fail_domains       DNS errors for these domains => assume nonexist
   srv_service           when SRV used, the service name
   srv_fail_domains      DNS errors for these domains => assume nonexist
   mx_fail_domains       DNS errors for these domains => assume nonexist


@@ -2590,20 +2586,21 @@ if (fully_qualified_name != NULL) *fully_qualified_name = host->name;
 dns_init((whichrrs & HOST_FIND_QUALIFY_SINGLE) != 0,
          (whichrrs & HOST_FIND_SEARCH_PARENTS) != 0,
         dnssec_request);
 dns_init((whichrrs & HOST_FIND_QUALIFY_SINGLE) != 0,
          (whichrrs & HOST_FIND_SEARCH_PARENTS) != 0,
         dnssec_request);

-host_find_failed_syntax = FALSE;
+f.host_find_failed_syntax = FALSE;

 
 /* First, if requested, look for SRV records. The service name is given; we
 assume TCP protocol. DNS domain names are constrained to a maximum of 256
 characters, so the code below should be safe. */
 
 
 /* First, if requested, look for SRV records. The service name is given; we
 assume TCP protocol. DNS domain names are constrained to a maximum of 256
 characters, so the code below should be safe. */
 

-if ((whichrrs & HOST_FIND_BY_SRV) != 0)
+if (whichrrs & HOST_FIND_BY_SRV)

   {
   {

-  uschar buffer[300];
-  uschar *temp_fully_qualified_name = buffer;
+  gstring * g;
+  uschar * temp_fully_qualified_name;

   int prefix_length;
 
   int prefix_length;
 

-  (void)sprintf(CS buffer, "_%s._tcp.%n%.256s", srv_service, &prefix_length,
-    host->name);
+  g = string_fmt_append(NULL, "_%s._tcp.%n%.256s",
+       srv_service, &prefix_length, host->name);
+  temp_fully_qualified_name = string_from_gstring(g);

   ind_type = T_SRV;
 
   /* Search for SRV records. If the fully qualified name is different to
   ind_type = T_SRV;
 
   /* Search for SRV records. If the fully qualified name is different to


@@ -2612,12 +2609,13 @@ if ((whichrrs & HOST_FIND_BY_SRV) != 0)
 
   dnssec = DS_UNK;
   lookup_dnssec_authenticated = NULL;
 
   dnssec = DS_UNK;
   lookup_dnssec_authenticated = NULL;

-  rc = dns_lookup_timerwrap(&dnsa, buffer, ind_type, CUSS &temp_fully_qualified_name);
+  rc = dns_lookup_timerwrap(&dnsa, temp_fully_qualified_name, ind_type,
+       CUSS &temp_fully_qualified_name);

 
   DEBUG(D_dns)
     if ((dnssec_request || dnssec_require)
 
   DEBUG(D_dns)
     if ((dnssec_request || dnssec_require)

-       & !dns_is_secure(&dnsa)
-       & dns_is_aa(&dnsa))
+       && !dns_is_secure(&dnsa)
+       && dns_is_aa(&dnsa))

       debug_printf("DNS lookup of %.256s (SRV) requested AD, but got AA\n", host->name);
 
   if (dnssec_request)
       debug_printf("DNS lookup of %.256s (SRV) requested AD, but got AA\n", host->name);
 
   if (dnssec_request)


@@ -2628,7 +2626,7 @@ if ((whichrrs & HOST_FIND_BY_SRV) != 0)
       { dnssec = DS_NO; lookup_dnssec_authenticated = US"no"; }
     }
 
       { dnssec = DS_NO; lookup_dnssec_authenticated = US"no"; }
     }
 

-  if (temp_fully_qualified_name != buffer && fully_qualified_name != NULL)
+  if (temp_fully_qualified_name != g->s && fully_qualified_name != NULL)

     *fully_qualified_name = temp_fully_qualified_name + prefix_length;
 
   /* On DNS failures, we give the "try again" error unless the domain is
     *fully_qualified_name = temp_fully_qualified_name + prefix_length;
 
   /* On DNS failures, we give the "try again" error unless the domain is


@@ -2720,7 +2718,7 @@ host. */
 
 if (rc != DNS_SUCCEED)
   {
 
 if (rc != DNS_SUCCEED)
   {

-  if ((whichrrs & HOST_FIND_BY_A) == 0)
+  if (!(whichrrs & (HOST_FIND_BY_A | HOST_FIND_BY_AAAA)))

     {
     DEBUG(D_host_lookup) debug_printf("Address records are not being sought\n");
     yield = HOST_FIND_FAILED;
     {
     DEBUG(D_host_lookup) debug_printf("Address records are not being sought\n");
     yield = HOST_FIND_FAILED;


@@ -2733,7 +2731,7 @@ if (rc != DNS_SUCCEED)
   host->dnssec = DS_UNK;
   lookup_dnssec_authenticated = NULL;
   rc = set_address_from_dns(host, &last, ignore_target_hosts, FALSE,
   host->dnssec = DS_UNK;
   lookup_dnssec_authenticated = NULL;
   rc = set_address_from_dns(host, &last, ignore_target_hosts, FALSE,

-    fully_qualified_name, dnssec_request, dnssec_require);
+    fully_qualified_name, dnssec_request, dnssec_require, whichrrs);

 
   /* If one or more address records have been found, check that none of them
   are local. Since we know the host items all have their IP addresses
 
   /* If one or more address records have been found, check that none of them
   are local. Since we know the host items all have their IP addresses


@@ -2857,7 +2855,7 @@ for (rr = dns_next_rr(&dnsa, &dnss, RESET_ANSWERS);
   block. Otherwise, add a new block in the correct place; if it has to be
   before the first block, copy the first block's data to a new second block. */
 
   block. Otherwise, add a new block in the correct place; if it has to be
   before the first block, copy the first block's data to a new second block. */
 

-  if (last == NULL)
+  if (!last)

     {
     host->name = string_copy_dnsdomain(data);
     host->address = NULL;
     {
     host->name = string_copy_dnsdomain(data);
     host->address = NULL;


@@ -3068,20 +3066,18 @@ for (h = host; h != last->next; h = h->next)
   if (h->address) continue;  /* Inserted by a multihomed host */
 
   rc = set_address_from_dns(h, &last, ignore_target_hosts, allow_mx_to_ip,
   if (h->address) continue;  /* Inserted by a multihomed host */
 
   rc = set_address_from_dns(h, &last, ignore_target_hosts, allow_mx_to_ip,

-    NULL, dnssec_request, dnssec_require);
+    NULL, dnssec_request, dnssec_require,
+    whichrrs & HOST_FIND_IPV4_ONLY
+    ?  HOST_FIND_BY_A  :  HOST_FIND_BY_A | HOST_FIND_BY_AAAA);

   if (rc != HOST_FOUND)
     {
     h->status = hstatus_unusable;
     switch (rc)
       {
   if (rc != HOST_FOUND)
     {
     h->status = hstatus_unusable;
     switch (rc)
       {

-      case HOST_FIND_AGAIN:
-       yield = rc; h->why = hwhy_deferred; break;
-      case HOST_FIND_SECURITY:
-       yield = rc; h->why = hwhy_insecure; break;
-      case HOST_IGNORED:
-       h->why = hwhy_ignored; break;
-      default:
-       h->why = hwhy_failed; break;
+      case HOST_FIND_AGAIN:    yield = rc; h->why = hwhy_deferred; break;
+      case HOST_FIND_SECURITY: yield = rc; h->why = hwhy_insecure; break;
+      case HOST_IGNORED:       h->why = hwhy_ignored; break;
+      default:                 h->why = hwhy_failed; break;

       }
     }
   }
       }
     }
   }


@@ -3132,12 +3128,22 @@ if (h != last && !disable_ipv6) for (h = host; h != last; h = h->next)
   host_item temp;
   host_item *next = h->next;
 
   host_item temp;
   host_item *next = h->next;
 

-  if (h->mx != next->mx ||                   /* If next is different MX */
-      h->address == NULL ||                  /* OR this one is unset */
-      Ustrchr(h->address, ':') != NULL ||    /* OR this one is IPv6 */
-      (next->address != NULL &&
-       Ustrchr(next->address, ':') == NULL)) /* OR next is IPv4 */
+  if (  h->mx != next->mx                      /* If next is different MX */
+     || !h->address                            /* OR this one is unset */
+     )
+    continue;                                  /* move on to next */
+
+  if (  whichrrs & HOST_FIND_IPV4_FIRST
+     ?     !Ustrchr(h->address, ':')           /* OR this one is IPv4 */
+        || next->address
+           && Ustrchr(next->address, ':')      /* OR next is IPv6 */
+
+     :     Ustrchr(h->address, ':')            /* OR this one is IPv6 */
+        || next->address
+           && !Ustrchr(next->address, ':')     /* OR next is IPv4 */
+     )

     continue;                                /* move on to next */
     continue;                                /* move on to next */

+

   temp = *h;                                 /* otherwise, swap */
   temp.next = next->next;
   *h = *next;
   temp = *h;                                 /* otherwise, swap */
   temp.next = next->next;
   *h = *next;


@@ -3198,7 +3204,7 @@ return yield;
 int main(int argc, char **cargv)
 {
 host_item h;
 int main(int argc, char **cargv)
 {
 host_item h;

-int whichrrs = HOST_FIND_BY_MX | HOST_FIND_BY_A;
+int whichrrs = HOST_FIND_BY_MX | HOST_FIND_BY_A | HOST_FIND_BY_AAAA;

 BOOL byname = FALSE;
 BOOL qualify_single = TRUE;
 BOOL search_parents = FALSE;
 BOOL byname = FALSE;
 BOOL qualify_single = TRUE;
 BOOL search_parents = FALSE;


@@ -3240,15 +3246,15 @@ while (Ufgets(buffer, 256, stdin) != NULL)
 
   if (Ustrcmp(buffer, "byname") == 0) byname = TRUE;
   else if (Ustrcmp(buffer, "no_byname") == 0) byname = FALSE;
 
   if (Ustrcmp(buffer, "byname") == 0) byname = TRUE;
   else if (Ustrcmp(buffer, "no_byname") == 0) byname = FALSE;

-  else if (Ustrcmp(buffer, "a_only") == 0) whichrrs = HOST_FIND_BY_A;
+  else if (Ustrcmp(buffer, "a_only") == 0) whichrrs = HOST_FIND_BY_A | HOST_FIND_BY_AAAA;

   else if (Ustrcmp(buffer, "mx_only") == 0) whichrrs = HOST_FIND_BY_MX;
   else if (Ustrcmp(buffer, "srv_only") == 0) whichrrs = HOST_FIND_BY_SRV;
   else if (Ustrcmp(buffer, "srv+a") == 0)
   else if (Ustrcmp(buffer, "mx_only") == 0) whichrrs = HOST_FIND_BY_MX;
   else if (Ustrcmp(buffer, "srv_only") == 0) whichrrs = HOST_FIND_BY_SRV;
   else if (Ustrcmp(buffer, "srv+a") == 0)

-    whichrrs = HOST_FIND_BY_SRV | HOST_FIND_BY_A;
+    whichrrs = HOST_FIND_BY_SRV | HOST_FIND_BY_A | HOST_FIND_BY_AAAA;

   else if (Ustrcmp(buffer, "srv+mx") == 0)
     whichrrs = HOST_FIND_BY_SRV | HOST_FIND_BY_MX;
   else if (Ustrcmp(buffer, "srv+mx+a") == 0)
   else if (Ustrcmp(buffer, "srv+mx") == 0)
     whichrrs = HOST_FIND_BY_SRV | HOST_FIND_BY_MX;
   else if (Ustrcmp(buffer, "srv+mx+a") == 0)

-    whichrrs = HOST_FIND_BY_SRV | HOST_FIND_BY_MX | HOST_FIND_BY_A;
+    whichrrs = HOST_FIND_BY_SRV | HOST_FIND_BY_MX | HOST_FIND_BY_A | HOST_FIND_BY_AAAA;

   else if (Ustrcmp(buffer, "qualify_single")    == 0) qualify_single = TRUE;
   else if (Ustrcmp(buffer, "no_qualify_single") == 0) qualify_single = FALSE;
   else if (Ustrcmp(buffer, "search_parents")    == 0) search_parents = TRUE;
   else if (Ustrcmp(buffer, "qualify_single")    == 0) qualify_single = TRUE;
   else if (Ustrcmp(buffer, "no_qualify_single") == 0) qualify_single = FALSE;
   else if (Ustrcmp(buffer, "search_parents")    == 0) search_parents = TRUE;


@@ -3258,7 +3264,7 @@ while (Ufgets(buffer, 256, stdin) != NULL)
   else if (Ustrcmp(buffer, "require_dnssec")    == 0) require_dnssec = TRUE;
   else if (Ustrcmp(buffer, "no_require_dnssec") == 0) require_dnssec = FALSE;
   else if (Ustrcmp(buffer, "test_harness") == 0)
   else if (Ustrcmp(buffer, "require_dnssec")    == 0) require_dnssec = TRUE;
   else if (Ustrcmp(buffer, "no_require_dnssec") == 0) require_dnssec = FALSE;
   else if (Ustrcmp(buffer, "test_harness") == 0)

-    running_in_test_harness = !running_in_test_harness;
+    f.running_in_test_harness = !f.running_in_test_harness;

   else if (Ustrcmp(buffer, "ipv6") == 0) disable_ipv6 = !disable_ipv6;
   else if (Ustrcmp(buffer, "res_debug") == 0)
     {
   else if (Ustrcmp(buffer, "ipv6") == 0) disable_ipv6 = !disable_ipv6;
   else if (Ustrcmp(buffer, "res_debug") == 0)
     {