Unbreak heimdal_gssapi auth driver

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

diff --git a/src/src/dns.c b/src/src/dns.c
index ad98a9d4e420003bf003f64c204bac1356b70ade..b7978c52133519455a211bbc4ef2789175e9f7a0 100644 (file)
--- a/src/src/dns.c
+++ b/src/src/dns.c
@@ -2,7 +2,7 @@
 *     Exim - an Internet mail transport agent    *
 *************************************************/
 
 *     Exim - an Internet mail transport agent    *
 *************************************************/
 

-/* Copyright (c) University of Cambridge 1995 - 2014 */
+/* Copyright (c) University of Cambridge 1995 - 2018 */

 /* See the file NOTICE for conditions of use and distribution. */
 
 /* Functions for interfacing with the DNS. */
 /* See the file NOTICE for conditions of use and distribution. */
 
 /* Functions for interfacing with the DNS. */


@@ -40,7 +40,6 @@ fakens_search(const uschar *domain, int type, uschar *answerptr, int size)
 {
 int len = Ustrlen(domain);
 int asize = size;                  /* Locally modified */
 {
 int len = Ustrlen(domain);
 int asize = size;                  /* Locally modified */

-uschar *endname;

 uschar name[256];
 uschar utilname[256];
 uschar *aptr = answerptr;          /* Locally modified */
 uschar name[256];
 uschar utilname[256];
 uschar *aptr = answerptr;          /* Locally modified */


@@ -51,33 +50,6 @@ struct stat statbuf;
 if (domain[len - 1] == '.') len--;
 Ustrncpy(name, domain, len);
 name[len] = 0;
 if (domain[len - 1] == '.') len--;
 Ustrncpy(name, domain, len);
 name[len] = 0;

-endname = name + len;
-
-/* This code, for forcing TRY_AGAIN and NO_RECOVERY, is here so that it works
-for the old test suite that uses a real nameserver. When the old test suite is
-eventually abandoned, this code could be moved into the fakens utility. */
-
-if (len >= 14 && Ustrcmp(endname - 14, "test.again.dns") == 0)
-  {
-  int delay = Uatoi(name);  /* digits at the start of the name */
-  DEBUG(D_dns) debug_printf("Return from DNS lookup of %s (%s) faked for testing\n",
-    name, dns_text_type(type));
-  if (delay > 0)
-    {
-    DEBUG(D_dns) debug_printf("delaying %d seconds\n", delay);
-    sleep(delay);
-    }
-  h_errno = TRY_AGAIN;
-  return -1;
-  }
-
-if (len >= 13 && Ustrcmp(endname - 13, "test.fail.dns") == 0)
-  {
-  DEBUG(D_dns) debug_printf("Return from DNS lookup of %s (%s) faked for testing\n",
-    name, dns_text_type(type));
-  h_errno = NO_RECOVERY;
-  return -1;
-  }

 
 /* Look for the fakens utility, and if it exists, call it. */
 
 
 /* Look for the fakens utility, and if it exists, call it. */
 


@@ -112,7 +84,7 @@ if (stat(CS utilname, &statbuf) >= 0)
     asize -= rc;      /* may need to be passed on to res_search(). */
     }
 
     asize -= rc;      /* may need to be passed on to res_search(). */
     }
 

-  /* If we ran out of output buffer before exhasting the return,
+  /* If we ran out of output buffer before exhausting the return,

   carry on reading and counting it. */
 
   if (asize == 0)
   carry on reading and counting it. */
 
   if (asize == 0)


@@ -137,7 +109,7 @@ if (stat(CS utilname, &statbuf) >= 0)
   }
 else
   {
   }
 else
   {

-    DEBUG(D_dns) debug_printf("fakens (%s) not found\n", utilname);
+  DEBUG(D_dns) debug_printf("fakens (%s) not found\n", utilname);

   }
 
 /* fakens utility not found, or it returned "pass on" */
   }
 
 /* fakens utility not found, or it returned "pass on" */


@@ -299,10 +271,7 @@ else
     {
     int j;
     for (j = 0; j < 32; j += 4)
     {
     int j;
     for (j = 0; j < 32; j += 4)

-      {
-      sprintf(CS pp, "%x.", (v6[i] >> j) & 15);
-      pp += 2;
-      }
+      pp += sprintf(CS pp, "%x.", (v6[i] >> j) & 15);

     }
   Ustrcpy(pp, "ip6.arpa.");
 
     }
   Ustrcpy(pp, "ip6.arpa.");
 


@@ -333,6 +302,15 @@ else
 
 
 
 
 
 

+/* Increment the aptr in dnss, checking against dnsa length.
+Return: TRUE for a bad result
+*/
+static BOOL
+dnss_inc_aptr(const dns_answer * dnsa, dns_scan * dnss, unsigned delta)
+{
+return (dnss->aptr += delta) >= dnsa->answer + dnsa->answerlen;
+}
+

 /*************************************************
 *       Get next DNS record from answer block    *
 *************************************************/
 /*************************************************
 *       Get next DNS record from answer block    *
 *************************************************/


@@ -345,59 +323,89 @@ The result is in static storage which must be copied if it is to be preserved.
 Arguments:
   dnsa      pointer to dns answer block
   dnss      pointer to dns scan block
 Arguments:
   dnsa      pointer to dns answer block
   dnss      pointer to dns scan block

-  reset     option specifing what portion to scan, as described above
+  reset     option specifying what portion to scan, as described above

 
 Returns:    next dns record, or NULL when no more
 */
 
 dns_record *
 
 Returns:    next dns record, or NULL when no more
 */
 
 dns_record *

-dns_next_rr(dns_answer *dnsa, dns_scan *dnss, int reset)
+dns_next_rr(const dns_answer *dnsa, dns_scan *dnss, int reset)

 {
 {

-HEADER *h = (HEADER *)dnsa->answer;
+const HEADER * h = (const HEADER *)dnsa->answer;

 int namelen;
 
 int namelen;
 

+char * trace = NULL;
+#ifdef rr_trace
+# define TRACE DEBUG(D_dns)
+#else
+trace = trace;
+# define TRACE if (FALSE)
+#endif
+

 /* Reset the saved data when requested to, and skip to the first required RR */
 
 if (reset != RESET_NEXT)
   {
   dnss->rrcount = ntohs(h->qdcount);
 /* Reset the saved data when requested to, and skip to the first required RR */
 
 if (reset != RESET_NEXT)
   {
   dnss->rrcount = ntohs(h->qdcount);

+  TRACE debug_printf("%s: reset (Q rrcount %d)\n", __FUNCTION__, dnss->rrcount);

   dnss->aptr = dnsa->answer + sizeof(HEADER);
 
   /* Skip over questions; failure to expand the name just gives up */
 
   while (dnss->rrcount-- > 0)
     {
   dnss->aptr = dnsa->answer + sizeof(HEADER);
 
   /* Skip over questions; failure to expand the name just gives up */
 
   while (dnss->rrcount-- > 0)
     {

+    TRACE trace = "Q-namelen";

     namelen = dn_expand(dnsa->answer, dnsa->answer + dnsa->answerlen,
     namelen = dn_expand(dnsa->answer, dnsa->answer + dnsa->answerlen,

-      dnss->aptr, (DN_EXPAND_ARG4_TYPE) &(dnss->srr.name), DNS_MAXNAME);
-    if (namelen < 0) { dnss->rrcount = 0; return NULL; }
-    dnss->aptr += namelen + 4;    /* skip name & type & class */
+      dnss->aptr, (DN_EXPAND_ARG4_TYPE) &dnss->srr.name, DNS_MAXNAME);
+    if (namelen < 0) goto null_return;
+    /* skip name & type & class */
+    TRACE trace = "Q-skip";
+    if (dnss_inc_aptr(dnsa, dnss, namelen+4)) goto null_return;

     }
 
   /* Get the number of answer records. */
 
   dnss->rrcount = ntohs(h->ancount);
     }
 
   /* Get the number of answer records. */
 
   dnss->rrcount = ntohs(h->ancount);

+  TRACE debug_printf("%s: reset (A rrcount %d)\n", __FUNCTION__, dnss->rrcount);

 
   /* Skip over answers if we want to look at the authority section. Also skip
   the NS records (i.e. authority section) if wanting to look at the additional
   records. */
 
 
   /* Skip over answers if we want to look at the authority section. Also skip
   the NS records (i.e. authority section) if wanting to look at the additional
   records. */
 

-  if (reset == RESET_ADDITIONAL) dnss->rrcount += ntohs(h->nscount);
+  if (reset == RESET_ADDITIONAL)
+    {
+    TRACE debug_printf("%s: additional\n", __FUNCTION__);
+    dnss->rrcount += ntohs(h->nscount);
+    TRACE debug_printf("%s: reset (NS rrcount %d)\n", __FUNCTION__, dnss->rrcount);
+    }

 
   if (reset == RESET_AUTHORITY || reset == RESET_ADDITIONAL)
     {
 
   if (reset == RESET_AUTHORITY || reset == RESET_ADDITIONAL)
     {

+    TRACE if (reset == RESET_AUTHORITY)
+      debug_printf("%s: authority\n", __FUNCTION__);

     while (dnss->rrcount-- > 0)
       {
     while (dnss->rrcount-- > 0)
       {

+      TRACE trace = "A-namelen";

       namelen = dn_expand(dnsa->answer, dnsa->answer + dnsa->answerlen,
       namelen = dn_expand(dnsa->answer, dnsa->answer + dnsa->answerlen,

-        dnss->aptr, (DN_EXPAND_ARG4_TYPE) &(dnss->srr.name), DNS_MAXNAME);
-      if (namelen < 0) { dnss->rrcount = 0; return NULL; }
-      dnss->aptr += namelen + 8;            /* skip name, type, class & TTL */
+        dnss->aptr, (DN_EXPAND_ARG4_TYPE) &dnss->srr.name, DNS_MAXNAME);
+      if (namelen < 0) goto null_return;
+      /* skip name, type, class & TTL */
+      TRACE trace = "A-hdr";
+      if (dnss_inc_aptr(dnsa, dnss, namelen+8)) goto null_return;

       GETSHORT(dnss->srr.size, dnss->aptr); /* size of data portion */
       GETSHORT(dnss->srr.size, dnss->aptr); /* size of data portion */

-      dnss->aptr += dnss->srr.size;         /* skip over it */
+      /* skip over it */
+      TRACE trace = "A-skip";
+      if (dnss_inc_aptr(dnsa, dnss, dnss->srr.size)) goto null_return;

       }
       }

-    dnss->rrcount = (reset == RESET_AUTHORITY)
+    dnss->rrcount = reset == RESET_AUTHORITY

       ? ntohs(h->nscount) : ntohs(h->arcount);
       ? ntohs(h->nscount) : ntohs(h->arcount);

+    TRACE debug_printf("%s: reset (%s rrcount %d)\n", __FUNCTION__,
+      reset == RESET_AUTHORITY ? "NS" : "AR", dnss->rrcount);

     }
     }

+  TRACE debug_printf("%s: %d RRs to read\n", __FUNCTION__, dnss->rrcount);

   }
   }

+else
+  TRACE debug_printf("%s: next (%d left)\n", __FUNCTION__, dnss->rrcount);

 
 /* The variable dnss->aptr is now pointing at the next RR, and dnss->rrcount
 contains the number of RR records left. */
 
 /* The variable dnss->aptr is now pointing at the next RR, and dnss->rrcount
 contains the number of RR records left. */


@@ -407,24 +415,67 @@ if (dnss->rrcount-- <= 0) return NULL;
 /* If expanding the RR domain name fails, behave as if no more records
 (something safe). */
 
 /* If expanding the RR domain name fails, behave as if no more records
 (something safe). */
 

+TRACE trace = "R-namelen";

 namelen = dn_expand(dnsa->answer, dnsa->answer + dnsa->answerlen, dnss->aptr,
 namelen = dn_expand(dnsa->answer, dnsa->answer + dnsa->answerlen, dnss->aptr,

-  (DN_EXPAND_ARG4_TYPE) &(dnss->srr.name), DNS_MAXNAME);
-if (namelen < 0) { dnss->rrcount = 0; return NULL; }
+  (DN_EXPAND_ARG4_TYPE) &dnss->srr.name, DNS_MAXNAME);
+if (namelen < 0) goto null_return;

 
 /* Move the pointer past the name and fill in the rest of the data structure
 from the following bytes. */
 
 
 /* Move the pointer past the name and fill in the rest of the data structure
 from the following bytes. */
 

-dnss->aptr += namelen;
-GETSHORT(dnss->srr.type, dnss->aptr); /* Record type */
-dnss->aptr += 6;                      /* Don't want class or TTL */
-GETSHORT(dnss->srr.size, dnss->aptr); /* Size of data portion */
-dnss->srr.data = dnss->aptr;          /* The record's data follows */
-dnss->aptr += dnss->srr.size;         /* Advance to next RR */
+TRACE trace = "R-name";
+if (dnss_inc_aptr(dnsa, dnss, namelen)) goto null_return;
+
+GETSHORT(dnss->srr.type, dnss->aptr);          /* Record type */
+TRACE trace = "R-class";
+if (dnss_inc_aptr(dnsa, dnss, 2)) goto null_return;    /* Don't want class */
+GETLONG(dnss->srr.ttl, dnss->aptr);            /* TTL */
+GETSHORT(dnss->srr.size, dnss->aptr);          /* Size of data portion */
+dnss->srr.data = dnss->aptr;                   /* The record's data follows */
+
+/* Unchecked increment ok here since no further access on this iteration;
+will be checked on next at "R-name". */
+
+dnss->aptr += dnss->srr.size;                  /* Advance to next RR */

 
 /* Return a pointer to the dns_record structure within the dns_answer. This is
 for convenience so that the scans can use nice-looking for loops. */
 
 
 /* Return a pointer to the dns_record structure within the dns_answer. This is
 for convenience so that the scans can use nice-looking for loops. */
 

-return &(dnss->srr);
+return &dnss->srr;
+
+null_return:
+  TRACE debug_printf("%s: terminate (%d RRs left). Last op: %s; errno %d %s\n",
+    __FUNCTION__, dnss->rrcount, trace, errno, strerror(errno));
+  dnss->rrcount = 0;
+  return NULL;
+}
+
+
+/* Extract the AUTHORITY information from the answer. If the answer isn't
+authoritative (AA not set), we do not extract anything.
+
+The AUTHORITY section contains NS records if the name in question was found,
+it contains a SOA record otherwise. (This is just from experience and some
+tests, is there some spec?)
+
+Scan the whole AUTHORITY section, since it may contain other records
+(e.g. NSEC3) too.
+
+Return: name for the authority, in an allocated string, or NULL if none found */
+
+static const uschar *
+dns_extract_auth_name(const dns_answer * dnsa) /* FIXME: const dns_answer */
+{
+dns_scan dnss;
+dns_record * rr;
+const HEADER * h = (const HEADER *) dnsa->answer;
+
+if (h->nscount && h->aa)
+  for (rr = dns_next_rr(dnsa, &dnss, RESET_AUTHORITY);
+       rr; rr = dns_next_rr(dnsa, &dnss, RESET_NEXT))
+    if (rr->type == (h->ancount ? T_NS : T_SOA))
+      return string_copy(rr->name);
+return NULL;

 }
 
 
 }
 
 


@@ -436,7 +487,7 @@ return &(dnss->srr);
 
 /* We do not perform DNSSEC work ourselves; if the administrator has installed
 a verifying resolver which sets AD as appropriate, though, we'll use that.
 
 /* We do not perform DNSSEC work ourselves; if the administrator has installed
 a verifying resolver which sets AD as appropriate, though, we'll use that.

-(AD = Authentic Data)
+(AD = Authentic Data, AA = Authoritative Answer)

 
 Argument:   pointer to dns answer block
 Returns:    bool indicating presence of AD bit
 
 Argument:   pointer to dns answer block
 Returns:    bool indicating presence of AD bit


@@ -450,18 +501,60 @@ DEBUG(D_dns)
   debug_printf("DNSSEC support disabled at build-time; dns_is_secure() false\n");
 return FALSE;
 #else
   debug_printf("DNSSEC support disabled at build-time; dns_is_secure() false\n");
 return FALSE;
 #else

-HEADER *h = (HEADER *)dnsa->answer;
-return h->ad ? TRUE : FALSE;
+const HEADER * h = (const HEADER *) dnsa->answer;
+const uschar * auth_name;
+const uschar * trusted;
+
+if (h->ad) return TRUE;
+
+/* If the resolver we ask is authoritative for the domain in question, it
+* may not set the AD but the AA bit. If we explicitly trust
+* the resolver for that domain (via a domainlist in dns_trust_aa),
+* we return TRUE to indicate a secure answer.
+*/
+
+if (  !h->aa
+   || !dns_trust_aa
+   || !(trusted = expand_string(dns_trust_aa))
+   || !*trusted
+   || !(auth_name = dns_extract_auth_name(dnsa))
+   || OK != match_isinlist(auth_name, &trusted, 0, NULL, NULL,
+                           MCL_DOMAIN, TRUE, NULL)
+   )
+  return FALSE;
+
+DEBUG(D_dns) debug_printf("DNS faked the AD bit "
+  "(got AA and matched with dns_trust_aa (%s in %s))\n",
+  auth_name, dns_trust_aa);
+
+return TRUE;

 #endif
 }
 
 static void
 dns_set_insecure(dns_answer * dnsa)
 {
 #endif
 }
 
 static void
 dns_set_insecure(dns_answer * dnsa)
 {

+#ifndef DISABLE_DNSSEC

 HEADER * h = (HEADER *)dnsa->answer;
 HEADER * h = (HEADER *)dnsa->answer;

-h->ad = 0;
+h->aa = h->ad = 0;
+#endif

 }
 
 }
 

+/************************************************
+ *     Check whether the AA bit is set         *
+ *     We need this to warn if we requested AD *
+ *     from an authoritative server            *
+ ************************************************/
+
+BOOL
+dns_is_aa(const dns_answer *dnsa)
+{
+#ifdef DISABLE_DNSSEC
+return FALSE;
+#else
+return ((const HEADER*)dnsa->answer)->aa;
+#endif
+}

 
 
 
 
 
 


@@ -503,6 +596,15 @@ switch(t)
 *        Cache a failed DNS lookup result        *
 *************************************************/
 
 *        Cache a failed DNS lookup result        *
 *************************************************/
 

+static void
+dns_fail_tag(uschar * buf, const uschar * name, int dns_type)
+{
+res_state resp = os_get_dns_resolver_res();
+sprintf(CS buf, "%.255s-%s-%lx", name, dns_text_type(dns_type),
+  (unsigned long) resp->options);
+}
+
+

 /* We cache failed lookup results so as not to experience timeouts many
 times for the same domain. We need to retain the resolver options because they
 may change. For successful lookups, we rely on resolver and/or name server
 /* We cache failed lookup results so as not to experience timeouts many
 times for the same domain. We need to retain the resolver options because they
 may change. For successful lookups, we rely on resolver and/or name server


@@ -519,28 +621,28 @@ Returns:     the return code
 static int
 dns_return(const uschar * name, int type, int rc)
 {
 static int
 dns_return(const uschar * name, int type, int rc)
 {

-res_state resp = os_get_dns_resolver_res();

 tree_node *node = store_get_perm(sizeof(tree_node) + 290);
 tree_node *node = store_get_perm(sizeof(tree_node) + 290);

-sprintf(CS node->name, "%.255s-%s-%lx", name, dns_text_type(type),
-  resp->options);
+dns_fail_tag(node->name, name, type);

 node->data.val = rc;
 (void)tree_insertnode(&tree_dns_fails, node);
 return rc;
 }
 
 node->data.val = rc;
 (void)tree_insertnode(&tree_dns_fails, node);
 return rc;
 }
 

-
-

 /*************************************************
 *              Do basic DNS lookup               *
 *************************************************/
 
 /* Call the resolver to look up the given domain name, using the given type,
 and check the result. The error code TRY_AGAIN is documented as meaning "non-
 /*************************************************
 *              Do basic DNS lookup               *
 *************************************************/
 
 /* Call the resolver to look up the given domain name, using the given type,
 and check the result. The error code TRY_AGAIN is documented as meaning "non-

-Authoritive Host not found, or SERVERFAIL". Sometimes there are badly set
+Authoritative Host not found, or SERVERFAIL". Sometimes there are badly set

 up nameservers that produce this error continually, so there is the option of
 providing a list of domains for which this is treated as a non-existent
 host.
 
 up nameservers that produce this error continually, so there is the option of
 providing a list of domains for which this is treated as a non-existent
 host.
 

+The dns_answer structure is pretty big; enough to hold a max-sized DNS message
+- so best allocated from fast-release memory.  As of writing, all our callers
+use a stack-auto variable.
+

 Arguments:
   dnsa      pointer to dns_answer structure
   name      name to look up
 Arguments:
   dnsa      pointer to dns_answer structure
   name      name to look up


@@ -562,7 +664,6 @@ dns_basic_lookup(dns_answer *dnsa, const uschar *name, int type)
 int rc = -1;
 const uschar *save_domain;
 #endif
 int rc = -1;
 const uschar *save_domain;
 #endif

-res_state resp = os_get_dns_resolver_res();

 
 tree_node *previous;
 uschar node_name[290];
 
 tree_node *previous;
 uschar node_name[290];


@@ -572,21 +673,19 @@ a timeout on one domain doesn't happen time and time again for messages that
 have many addresses in the same domain. We rely on the resolver and name server
 caching for successful lookups. */
 
 have many addresses in the same domain. We rely on the resolver and name server
 caching for successful lookups. */
 

-sprintf(CS node_name, "%.255s-%s-%lx", name, dns_text_type(type),
-  resp->options);
-previous = tree_search(tree_dns_fails, node_name);
-if (previous != NULL)
+dns_fail_tag(node_name, name, type);
+if ((previous = tree_search(tree_dns_fails, node_name)))

   {
   DEBUG(D_dns) debug_printf("DNS lookup of %.255s-%s: using cached value %s\n",
     name, dns_text_type(type),
   {
   DEBUG(D_dns) debug_printf("DNS lookup of %.255s-%s: using cached value %s\n",
     name, dns_text_type(type),

-      (previous->data.val == DNS_NOMATCH)? "DNS_NOMATCH" :
-      (previous->data.val == DNS_NODATA)? "DNS_NODATA" :
-      (previous->data.val == DNS_AGAIN)? "DNS_AGAIN" :
-      (previous->data.val == DNS_FAIL)? "DNS_FAIL" : "??");
+      previous->data.val == DNS_NOMATCH ? "DNS_NOMATCH" :
+      previous->data.val == DNS_NODATA ? "DNS_NODATA" :
+      previous->data.val == DNS_AGAIN ? "DNS_AGAIN" :
+      previous->data.val == DNS_FAIL ? "DNS_FAIL" : "??");

   return previous->data.val;
   }
 
   return previous->data.val;
   }
 

-#ifdef EXPERIMENTAL_INTERNATIONAL
+#ifdef SUPPORT_I18N

 /* Convert all names to a-label form before doing lookup */
   {
   uschar * alabel;
 /* Convert all names to a-label form before doing lookup */
   {
   uschar * alabel;


@@ -598,14 +697,14 @@ if (previous != NULL)
     DEBUG(D_dns)
       debug_printf("DNS name '%s' utf8 conversion to alabel failed: %s\n", name,
         errstr);
     DEBUG(D_dns)
       debug_printf("DNS name '%s' utf8 conversion to alabel failed: %s\n", name,
         errstr);

-    host_find_failed_syntax = TRUE;
+    f.host_find_failed_syntax = TRUE;

     return DNS_NOMATCH;
     }
   name = alabel;
   }
 #endif
 
     return DNS_NOMATCH;
     }
   name = alabel;
   }
 #endif
 

-/* If configured, check the hygene of the name passed to lookup. Otherwise,
+/* If configured, check the hygiene of the name passed to lookup. Otherwise,

 although DNS lookups may give REFUSED at the lower level, some resolvers
 turn this into TRY_AGAIN, which is silly. Give a NOMATCH return, since such
 domains cannot be in the DNS. The check is now done by a regular expression;
 although DNS lookups may give REFUSED at the lower level, some resolvers
 turn this into TRY_AGAIN, which is silly. Give a NOMATCH return, since such
 domains cannot be in the DNS. The check is now done by a regular expression;


@@ -617,7 +716,11 @@ lookup, which constructs the names itself, so they should be OK. Besides,
 bitstring labels don't conform to normal name syntax. (But the aren't used any
 more.)
 
 bitstring labels don't conform to normal name syntax. (But the aren't used any
 more.)
 

-For SRV records, we omit the initial _smtp._tcp. components at the start. */
+For SRV records, we omit the initial _smtp._tcp. components at the start.
+The check has been seen to bite on the destination of a SRV lookup that
+initiall hit a CNAME, for which the next name had only two components.
+RFC2782 makes no mention of the possibiility of CNAMES, but the Wikipedia
+article on SRV says they are not a valid configuration. */

 
 #ifndef STAND_ALONE   /* Omit this for stand-alone tests */
 
 
 #ifndef STAND_ALONE   /* Omit this for stand-alone tests */
 


@@ -633,17 +736,17 @@ if (check_dns_names_pattern[0] != 0 && type != T_PTR && type != T_TXT)
 
   if (type == T_SRV || type == T_TLSA)
     {
 
   if (type == T_SRV || type == T_TLSA)
     {

-    while (*checkname++ != '.');
-    while (*checkname++ != '.');
+    while (*checkname && *checkname++ != '.') ;
+    while (*checkname && *checkname++ != '.') ;

     }
 
   if (pcre_exec(regex_check_dns_names, NULL, CCS checkname, Ustrlen(checkname),
     }
 
   if (pcre_exec(regex_check_dns_names, NULL, CCS checkname, Ustrlen(checkname),

-      0, PCRE_EOPT, ovector, sizeof(ovector)/sizeof(int)) < 0)
+      0, PCRE_EOPT, ovector, nelem(ovector)) < 0)

     {
     DEBUG(D_dns)
       debug_printf("DNS name syntax check failed: %s (%s)\n", name,
         dns_text_type(type));
     {
     DEBUG(D_dns)
       debug_printf("DNS name syntax check failed: %s (%s)\n", name,
         dns_text_type(type));

-    host_find_failed_syntax = TRUE;
+    f.host_find_failed_syntax = TRUE;

     return DNS_NOMATCH;
     }
   }
     return DNS_NOMATCH;
     }
   }


@@ -666,62 +769,63 @@ if ((type == T_A || type == T_AAAA) && string_is_ip_address(name, NULL) != 0)
 (res_search), we call fakens_search(), which recognizes certain special
 domains, and interfaces to a fake nameserver for certain special zones. */
 
 (res_search), we call fakens_search(), which recognizes certain special
 domains, and interfaces to a fake nameserver for certain special zones. */
 

-dnsa->answerlen = running_in_test_harness
-  ? fakens_search(name, type, dnsa->answer, MAXPACKET)
-  : res_search(CCS name, C_IN, type, dnsa->answer, MAXPACKET);
+dnsa->answerlen = f.running_in_test_harness
+  ? fakens_search(name, type, dnsa->answer, sizeof(dnsa->answer))
+  : res_search(CCS name, C_IN, type, dnsa->answer, sizeof(dnsa->answer));

 
 

-if (dnsa->answerlen > MAXPACKET)
+if (dnsa->answerlen > (int) sizeof(dnsa->answer))

   {
   {

-  DEBUG(D_dns) debug_printf("DNS lookup of %s (%s) resulted in overlong packet (size %d), truncating to %d.\n",
-    name, dns_text_type(type), dnsa->answerlen, MAXPACKET);
-  dnsa->answerlen = MAXPACKET;
+  DEBUG(D_dns) debug_printf("DNS lookup of %s (%s) resulted in overlong packet"
+    " (size %d), truncating to %u.\n",
+    name, dns_text_type(type), dnsa->answerlen, (unsigned int) sizeof(dnsa->answer));
+  dnsa->answerlen = sizeof(dnsa->answer);

   }
 
 if (dnsa->answerlen < 0) switch (h_errno)
   {
   case HOST_NOT_FOUND:
   }
 
 if (dnsa->answerlen < 0) switch (h_errno)
   {
   case HOST_NOT_FOUND:

-  DEBUG(D_dns) debug_printf("DNS lookup of %s (%s) gave HOST_NOT_FOUND\n"
-    "returning DNS_NOMATCH\n", name, dns_text_type(type));
-  return dns_return(name, type, DNS_NOMATCH);
+    DEBUG(D_dns) debug_printf("DNS lookup of %s (%s) gave HOST_NOT_FOUND\n"
+      "returning DNS_NOMATCH\n", name, dns_text_type(type));
+    return dns_return(name, type, DNS_NOMATCH);

 
   case TRY_AGAIN:
 
   case TRY_AGAIN:

-  DEBUG(D_dns) debug_printf("DNS lookup of %s (%s) gave TRY_AGAIN\n",
-    name, dns_text_type(type));
+    DEBUG(D_dns) debug_printf("DNS lookup of %s (%s) gave TRY_AGAIN\n",
+      name, dns_text_type(type));

 
 

-  /* Cut this out for various test programs */
+    /* Cut this out for various test programs */

 #ifndef STAND_ALONE
 #ifndef STAND_ALONE

-  save_domain = deliver_domain;
-  deliver_domain = string_copy(name);  /* set $domain */
-  rc = match_isinlist(name, (const uschar **)&dns_again_means_nonexist, 0, NULL, NULL,
-    MCL_DOMAIN, TRUE, NULL);
-  deliver_domain = save_domain;
-  if (rc != OK)
-    {
-    DEBUG(D_dns) debug_printf("returning DNS_AGAIN\n");
-    return dns_return(name, type, DNS_AGAIN);
-    }
-  DEBUG(D_dns) debug_printf("%s is in dns_again_means_nonexist: returning "
-    "DNS_NOMATCH\n", name);
-  return dns_return(name, type, DNS_NOMATCH);
+    save_domain = deliver_domain;
+    deliver_domain = string_copy(name);  /* set $domain */
+    rc = match_isinlist(name, (const uschar **)&dns_again_means_nonexist, 0, NULL, NULL,
+      MCL_DOMAIN, TRUE, NULL);
+    deliver_domain = save_domain;
+    if (rc != OK)
+      {
+      DEBUG(D_dns) debug_printf("returning DNS_AGAIN\n");
+      return dns_return(name, type, DNS_AGAIN);
+      }
+    DEBUG(D_dns) debug_printf("%s is in dns_again_means_nonexist: returning "
+      "DNS_NOMATCH\n", name);
+    return dns_return(name, type, DNS_NOMATCH);

 
 #else   /* For stand-alone tests */
 
 #else   /* For stand-alone tests */

-  return dns_return(name, type, DNS_AGAIN);
+    return dns_return(name, type, DNS_AGAIN);

 #endif
 
   case NO_RECOVERY:
 #endif
 
   case NO_RECOVERY:

-  DEBUG(D_dns) debug_printf("DNS lookup of %s (%s) gave NO_RECOVERY\n"
-    "returning DNS_FAIL\n", name, dns_text_type(type));
-  return dns_return(name, type, DNS_FAIL);
+    DEBUG(D_dns) debug_printf("DNS lookup of %s (%s) gave NO_RECOVERY\n"
+      "returning DNS_FAIL\n", name, dns_text_type(type));
+    return dns_return(name, type, DNS_FAIL);

 
   case NO_DATA:
 
   case NO_DATA:

-  DEBUG(D_dns) debug_printf("DNS lookup of %s (%s) gave NO_DATA\n"
-    "returning DNS_NODATA\n", name, dns_text_type(type));
-  return dns_return(name, type, DNS_NODATA);
+    DEBUG(D_dns) debug_printf("DNS lookup of %s (%s) gave NO_DATA\n"
+      "returning DNS_NODATA\n", name, dns_text_type(type));
+    return dns_return(name, type, DNS_NODATA);

 
   default:
 
   default:

-  DEBUG(D_dns) debug_printf("DNS lookup of %s (%s) gave unknown DNS error %d\n"
-    "returning DNS_FAIL\n", name, dns_text_type(type), h_errno);
-  return dns_return(name, type, DNS_FAIL);
+    DEBUG(D_dns) debug_printf("DNS lookup of %s (%s) gave unknown DNS error %d\n"
+      "returning DNS_FAIL\n", name, dns_text_type(type), h_errno);
+    return dns_return(name, type, DNS_FAIL);

   }
 
 DEBUG(D_dns) debug_printf("DNS lookup of %s (%s) succeeded\n",
   }
 
 DEBUG(D_dns) debug_printf("DNS lookup of %s (%s) succeeded\n",


@@ -740,6 +844,8 @@ return DNS_SUCCEED;
 /* Look up the given domain name, using the given type. Follow CNAMEs if
 necessary, but only so many times. There aren't supposed to be CNAME chains in
 the DNS, but you are supposed to cope with them if you find them.
 /* Look up the given domain name, using the given type. Follow CNAMEs if
 necessary, but only so many times. There aren't supposed to be CNAME chains in
 the DNS, but you are supposed to cope with them if you find them.

+By default, follow one CNAME since a resolver has been seen, faced with
+an MX request and a CNAME (to an A) but no MX present, returning the CNAME.

 
 The assumption is made that if the resolver gives back records of the
 requested type *and* a CNAME, we don't need to make another call to look up
 
 The assumption is made that if the resolver gives back records of the
 requested type *and* a CNAME, we don't need to make another call to look up


@@ -775,18 +881,24 @@ int i;
 const uschar *orig_name = name;
 BOOL secure_so_far = TRUE;
 
 const uschar *orig_name = name;
 BOOL secure_so_far = TRUE;
 

-/* Loop to follow CNAME chains so far, but no further... */
+/* By default, assume the resolver follows CNAME chains (and returns NODATA for
+an unterminated one). If it also does that for a CNAME loop, fine; if it returns
+a CNAME (maybe the last?) whine about it.  However, retain the coding for dumb
+resolvers hiding behind a config variable. Loop to follow CNAME chains so far,
+but no further...  The testsuite tests the latter case, mostly assuming that the
+former will work. */

 
 

-for (i = 0; i < 10; i++)
+for (i = 0; i <= dns_cname_loops; i++)

   {
   {

-  uschar data[256];
+  uschar * data;

   dns_record *rr, cname_rr, type_rr;
   dns_scan dnss;
   dns_record *rr, cname_rr, type_rr;
   dns_scan dnss;

-  int datalen, rc;
+  int rc;

 
   /* DNS lookup failures get passed straight back. */
 
 
   /* DNS lookup failures get passed straight back. */
 

-  if ((rc = dns_basic_lookup(dnsa, name, type)) != DNS_SUCCEED) return rc;
+  if ((rc = dns_basic_lookup(dnsa, name, type)) != DNS_SUCCEED)
+    return rc;

 
   /* We should have either records of the required type, or a CNAME record,
   or both. We need to know whether both exist for getting the fully qualified
 
   /* We should have either records of the required type, or a CNAME record,
   or both. We need to know whether both exist for getting the fully qualified


@@ -796,28 +908,26 @@ for (i = 0; i < 10; i++)
 
   cname_rr.data = type_rr.data = NULL;
   for (rr = dns_next_rr(dnsa, &dnss, RESET_ANSWERS);
 
   cname_rr.data = type_rr.data = NULL;
   for (rr = dns_next_rr(dnsa, &dnss, RESET_ANSWERS);

-       rr != NULL;
-       rr = dns_next_rr(dnsa, &dnss, RESET_NEXT))
-    {
+       rr; rr = dns_next_rr(dnsa, &dnss, RESET_NEXT))

     if (rr->type == type)
       {
       if (type_rr.data == NULL) type_rr = *rr;
       if (cname_rr.data != NULL) break;
       }
     if (rr->type == type)
       {
       if (type_rr.data == NULL) type_rr = *rr;
       if (cname_rr.data != NULL) break;
       }

-    else if (rr->type == T_CNAME) cname_rr = *rr;
-    }
+    else if (rr->type == T_CNAME)
+      cname_rr = *rr;

 
   /* For the first time round this loop, if a CNAME was found, take the fully
   qualified name from it; otherwise from the first data record, if present. */
 
 
   /* For the first time round this loop, if a CNAME was found, take the fully
   qualified name from it; otherwise from the first data record, if present. */
 

-  if (i == 0 && fully_qualified_name != NULL)
+  if (i == 0 && fully_qualified_name)

     {
     {

-    uschar * rr_name = cname_rr.data ? cname_rr.name
-      : type_rr.data ? type_rr.name : NULL;
+    uschar * rr_name = cname_rr.data
+      ? cname_rr.name : type_rr.data ? type_rr.name : NULL;

     if (  rr_name
        && Ustrcmp(rr_name, *fully_qualified_name) != 0
        && rr_name[0] != '*'
     if (  rr_name
        && Ustrcmp(rr_name, *fully_qualified_name) != 0
        && rr_name[0] != '*'

-#ifdef EXPERIMENTAL_INTERNATIONAL
+#ifdef SUPPORT_I18N

        && (  !string_is_utf8(*fully_qualified_name)
          || Ustrcmp(rr_name,
               string_domain_utf8_to_alabel(*fully_qualified_name, NULL)) != 0
        && (  !string_is_utf8(*fully_qualified_name)
          || Ustrcmp(rr_name,
               string_domain_utf8_to_alabel(*fully_qualified_name, NULL)) != 0


@@ -829,7 +939,7 @@ for (i = 0; i < 10; i++)
 
   /* If any data records of the correct type were found, we are done. */
 
 
   /* If any data records of the correct type were found, we are done. */
 

-  if (type_rr.data != NULL)
+  if (type_rr.data)

     {
     if (!secure_so_far)        /* mark insecure if any element of CNAME chain was */
       dns_set_insecure(dnsa);
     {
     if (!secure_so_far)        /* mark insecure if any element of CNAME chain was */
       dns_set_insecure(dnsa);


@@ -841,10 +951,13 @@ for (i = 0; i < 10; i++)
   have had a failure from dns_lookup). However code against the possibility of
   its not existing. */
 
   have had a failure from dns_lookup). However code against the possibility of
   its not existing. */
 

-  if (cname_rr.data == NULL) return DNS_FAIL;
-  datalen = dn_expand(dnsa->answer, dnsa->answer + dnsa->answerlen,
-    cname_rr.data, (DN_EXPAND_ARG4_TYPE)data, sizeof(data));
-  if (datalen < 0) return DNS_FAIL;
+  if (!cname_rr.data)
+    return DNS_FAIL;
+
+  data = store_get(256);
+  if (dn_expand(dnsa->answer, dnsa->answer + dnsa->answerlen,
+      cname_rr.data, (DN_EXPAND_ARG4_TYPE)data, 256) < 0)
+    return DNS_FAIL;

   name = data;
 
   if (!dns_is_secure(dnsa))
   name = data;
 
   if (!dns_is_secure(dnsa))


@@ -869,7 +982,7 @@ return DNS_FAIL;
 *    Do a DNS lookup and handle virtual types   *
 ************************************************/
 
 *    Do a DNS lookup and handle virtual types   *
 ************************************************/
 

-/* This function handles some invented "lookup types" that synthesize feature
+/* This function handles some invented "lookup types" that synthesize features

 not available in the basic types. The special types all have negative values.
 Positive type values are passed straight on to dns_lookup().
 
 not available in the basic types. The special types all have negative values.
 Positive type values are passed straight on to dns_lookup().
 


@@ -895,25 +1008,25 @@ switch (type)
   {
   /* The "mx hosts only" type doesn't require any special action here */
   case T_MXH:
   {
   /* The "mx hosts only" type doesn't require any special action here */
   case T_MXH:

-       return dns_lookup(dnsa, name, T_MX, fully_qualified_name);
+    return dns_lookup(dnsa, name, T_MX, fully_qualified_name);

 
   /* Find nameservers for the domain or the nearest enclosing zone, excluding
   the root servers. */
   case T_ZNS:
 
   /* Find nameservers for the domain or the nearest enclosing zone, excluding
   the root servers. */
   case T_ZNS:

-       type = T_NS;
-       /* FALLTHROUGH */
+    type = T_NS;
+    /* FALLTHROUGH */

   case T_SOA:
   case T_SOA:

-       {
-       const uschar *d = name;
-       while (d != 0)
-         {
-         int rc = dns_lookup(dnsa, d, type, fully_qualified_name);
-         if (rc != DNS_NOMATCH && rc != DNS_NODATA) return rc;
-         while (*d != 0 && *d != '.') d++;
-         if (*d++ == 0) break;
-         }
-       return DNS_NOMATCH;
-       }
+    {
+    const uschar *d = name;
+    while (d != 0)
+      {
+      int rc = dns_lookup(dnsa, d, type, fully_qualified_name);
+      if (rc != DNS_NOMATCH && rc != DNS_NODATA) return rc;
+      while (*d != 0 && *d != '.') d++;
+      if (*d++ == 0) break;
+      }
+    return DNS_NOMATCH;
+    }

 
   /* Try to look up the Client SMTP Authorization SRV record for the name. If
   there isn't one, search from the top downwards for a CSA record in a parent
 
   /* Try to look up the Client SMTP Authorization SRV record for the name. If
   there isn't one, search from the top downwards for a CSA record in a parent


@@ -922,148 +1035,144 @@ switch (type)
   can tell whether to look at the explicit authorization field or the subdomain
   assertion field. */
   case T_CSA:
   can tell whether to look at the explicit authorization field or the subdomain
   assertion field. */
   case T_CSA:

-       {
-       uschar *srvname, *namesuff, *tld, *p;
-       int priority, weight, port;
-       int limit, rc, i;
-       BOOL ipv6;
-       dns_record *rr;
-       dns_scan dnss;
-
-       DEBUG(D_dns) debug_printf("CSA lookup of %s\n", name);
-
-       srvname = string_sprintf("_client._smtp.%s", name);
-       rc = dns_lookup(dnsa, srvname, T_SRV, NULL);
-       if (rc == DNS_SUCCEED || rc == DNS_AGAIN)
-         {
-         if (rc == DNS_SUCCEED) *fully_qualified_name = string_copy(name);
-         return rc;
-         }
+    {
+    uschar *srvname, *namesuff, *tld;
+    int priority, weight, port;
+    int limit, rc, i;
+    BOOL ipv6;
+    dns_record *rr;
+    dns_scan dnss;
+
+    DEBUG(D_dns) debug_printf("CSA lookup of %s\n", name);
+
+    srvname = string_sprintf("_client._smtp.%s", name);
+    rc = dns_lookup(dnsa, srvname, T_SRV, NULL);
+    if (rc == DNS_SUCCEED || rc == DNS_AGAIN)
+      {
+      if (rc == DNS_SUCCEED) *fully_qualified_name = string_copy(name);
+      return rc;
+      }
+
+    /* Search for CSA subdomain assertion SRV records from the top downwards,
+    starting with the 2nd level domain. This order maximizes cache-friendliness.
+    We skip the top level domains to avoid loading their nameservers and because
+    we know they'll never have CSA SRV records. */

 
 

-       /* Search for CSA subdomain assertion SRV records from the top downwards,
-       starting with the 2nd level domain. This order maximizes cache-friendliness.
-       We skip the top level domains to avoid loading their nameservers and because
-       we know they'll never have CSA SRV records. */
+    namesuff = Ustrrchr(name, '.');
+    if (namesuff == NULL) return DNS_NOMATCH;
+    tld = namesuff + 1;
+    ipv6 = FALSE;
+    limit = dns_csa_search_limit;

 
 

-       namesuff = Ustrrchr(name, '.');
-       if (namesuff == NULL) return DNS_NOMATCH;
+    /* Use more appropriate search parameters if we are in the reverse DNS. */
+
+    if (strcmpic(namesuff, US".arpa") == 0)
+      if (namesuff - 8 > name && strcmpic(namesuff - 8, US".in-addr.arpa") == 0)
+       {
+       namesuff -= 8;
+       tld = namesuff + 1;
+       limit = 3;
+       }
+      else if (namesuff - 4 > name && strcmpic(namesuff - 4, US".ip6.arpa") == 0)
+       {
+       namesuff -= 4;

        tld = namesuff + 1;
        tld = namesuff + 1;

-       ipv6 = FALSE;
-       limit = dns_csa_search_limit;
+       ipv6 = TRUE;
+       limit = 3;
+       }

 
 

-       /* Use more appropriate search parameters if we are in the reverse DNS. */
+    DEBUG(D_dns) debug_printf("CSA TLD %s\n", tld);

 
 

-       if (strcmpic(namesuff, US".arpa") == 0)
-         {
-         if (namesuff - 8 > name && strcmpic(namesuff - 8, US".in-addr.arpa") == 0)
-               {
-               namesuff -= 8;
-               tld = namesuff + 1;
-               limit = 3;
-               }
-         else if (namesuff - 4 > name && strcmpic(namesuff - 4, US".ip6.arpa") == 0)
-               {
-               namesuff -= 4;
-               tld = namesuff + 1;
-               ipv6 = TRUE;
-               limit = 3;
-               }
-         }
+    /* Do not perform the search if the top level or 2nd level domains do not
+    exist. This is quite common, and when it occurs all the search queries would
+    go to the root or TLD name servers, which is not friendly. So we check the
+    AUTHORITY section; if it contains the root's SOA record or the TLD's SOA then
+    the TLD or the 2LD (respectively) doesn't exist and we can skip the search.
+    If the TLD and the 2LD exist but the explicit CSA record lookup failed, then
+    the AUTHORITY SOA will be the 2LD's or a subdomain thereof. */

 
 

-       DEBUG(D_dns) debug_printf("CSA TLD %s\n", tld);
+    if (rc == DNS_NOMATCH)
+      {
+      /* This is really gross. The successful return value from res_search() is
+      the packet length, which is stored in dnsa->answerlen. If we get a
+      negative DNS reply then res_search() returns -1, which causes the bounds
+      checks for name decompression to fail when it is treated as a packet
+      length, which in turn causes the authority search to fail. The correct
+      packet length has been lost inside libresolv, so we have to guess a
+      replacement value. (The only way to fix this properly would be to
+      re-implement res_search() and res_query() so that they don't muddle their
+      success and packet length return values.) For added safety we only reset
+      the packet length if the packet header looks plausible. */
+
+      const HEADER * h = (const HEADER *)dnsa->answer;
+      if (h->qr == 1 && h->opcode == QUERY && h->tc == 0
+         && (h->rcode == NOERROR || h->rcode == NXDOMAIN)
+         && ntohs(h->qdcount) == 1 && ntohs(h->ancount) == 0
+         && ntohs(h->nscount) >= 1)
+           dnsa->answerlen = sizeof(dnsa->answer);
+
+      for (rr = dns_next_rr(dnsa, &dnss, RESET_AUTHORITY);
+          rr; rr = dns_next_rr(dnsa, &dnss, RESET_NEXT)
+         )
+       if (rr->type != T_SOA) continue;
+       else if (strcmpic(rr->name, US"") == 0 ||
+                strcmpic(rr->name, tld) == 0) return DNS_NOMATCH;
+       else break;
+      }

 
 

-       /* Do not perform the search if the top level or 2nd level domains do not
-       exist. This is quite common, and when it occurs all the search queries would
-       go to the root or TLD name servers, which is not friendly. So we check the
-       AUTHORITY section; if it contains the root's SOA record or the TLD's SOA then
-       the TLD or the 2LD (respectively) doesn't exist and we can skip the search.
-       If the TLD and the 2LD exist but the explicit CSA record lookup failed, then
-       the AUTHORITY SOA will be the 2LD's or a subdomain thereof. */
+    for (i = 0; i < limit; i++)
+      {
+      if (ipv6)
+       {
+       /* Scan through the IPv6 reverse DNS in chunks of 16 bits worth of IP
+       address, i.e. 4 hex chars and 4 dots, i.e. 8 chars. */
+       namesuff -= 8;
+       if (namesuff <= name) return DNS_NOMATCH;
+       }
+      else
+       /* Find the start of the preceding domain name label. */
+       do
+         if (--namesuff <= name) return DNS_NOMATCH;
+       while (*namesuff != '.');

 
 

-       if (rc == DNS_NOMATCH)
-         {
-         /* This is really gross. The successful return value from res_search() is
-         the packet length, which is stored in dnsa->answerlen. If we get a
-         negative DNS reply then res_search() returns -1, which causes the bounds
-         checks for name decompression to fail when it is treated as a packet
-         length, which in turn causes the authority search to fail. The correct
-         packet length has been lost inside libresolv, so we have to guess a
-         replacement value. (The only way to fix this properly would be to
-         re-implement res_search() and res_query() so that they don't muddle their
-         success and packet length return values.) For added safety we only reset
-         the packet length if the packet header looks plausible. */
-
-         HEADER *h = (HEADER *)dnsa->answer;
-         if (h->qr == 1 && h->opcode == QUERY && h->tc == 0
-                 && (h->rcode == NOERROR || h->rcode == NXDOMAIN)
-                 && ntohs(h->qdcount) == 1 && ntohs(h->ancount) == 0
-                 && ntohs(h->nscount) >= 1)
-               dnsa->answerlen = MAXPACKET;
-
-         for (rr = dns_next_rr(dnsa, &dnss, RESET_AUTHORITY);
-                  rr != NULL;
-                  rr = dns_next_rr(dnsa, &dnss, RESET_NEXT))
-               if (rr->type != T_SOA) continue;
-               else if (strcmpic(rr->name, US"") == 0 ||
-                                strcmpic(rr->name, tld) == 0) return DNS_NOMATCH;
-               else break;
-         }
+      DEBUG(D_dns) debug_printf("CSA parent search at %s\n", namesuff + 1);

 
 

-       for (i = 0; i < limit; i++)
+      srvname = string_sprintf("_client._smtp.%s", namesuff + 1);
+      rc = dns_lookup(dnsa, srvname, T_SRV, NULL);
+      if (rc == DNS_AGAIN) return rc;
+      if (rc != DNS_SUCCEED) continue;
+
+      /* Check that the SRV record we have found is worth returning. We don't
+      just return the first one we find, because some lower level SRV record
+      might make stricter assertions than its parent domain. */
+
+      for (rr = dns_next_rr(dnsa, &dnss, RESET_ANSWERS);
+          rr; rr = dns_next_rr(dnsa, &dnss, RESET_NEXT)) if (rr->type == T_SRV)
+       {
+       const uschar * p = rr->data;
+
+       /* Extract the numerical SRV fields (p is incremented) */
+       GETSHORT(priority, p);
+       GETSHORT(weight, p);    weight = weight; /* compiler quietening */
+       GETSHORT(port, p);
+
+       /* Check the CSA version number */
+       if (priority != 1) continue;
+
+       /* If it's making an interesting assertion, return this response. */
+       if (port & 1)

          {
          {

-         if (ipv6)
-               {
-               /* Scan through the IPv6 reverse DNS in chunks of 16 bits worth of IP
-               address, i.e. 4 hex chars and 4 dots, i.e. 8 chars. */
-               namesuff -= 8;
-               if (namesuff <= name) return DNS_NOMATCH;
-               }
-         else
-               /* Find the start of the preceding domain name label. */
-               do
-                 if (--namesuff <= name) return DNS_NOMATCH;
-               while (*namesuff != '.');
-
-         DEBUG(D_dns) debug_printf("CSA parent search at %s\n", namesuff + 1);
-
-         srvname = string_sprintf("_client._smtp.%s", namesuff + 1);
-         rc = dns_lookup(dnsa, srvname, T_SRV, NULL);
-         if (rc == DNS_AGAIN) return rc;
-         if (rc != DNS_SUCCEED) continue;
-
-         /* Check that the SRV record we have found is worth returning. We don't
-         just return the first one we find, because some lower level SRV record
-         might make stricter assertions than its parent domain. */
-
-         for (rr = dns_next_rr(dnsa, &dnss, RESET_ANSWERS);
-                  rr != NULL;
-                  rr = dns_next_rr(dnsa, &dnss, RESET_NEXT))
-               {
-               if (rr->type != T_SRV) continue;
-
-               /* Extract the numerical SRV fields (p is incremented) */
-               p = rr->data;
-               GETSHORT(priority, p);
-               GETSHORT(weight, p);    weight = weight; /* compiler quietening */
-               GETSHORT(port, p);
-
-               /* Check the CSA version number */
-               if (priority != 1) continue;
-
-               /* If it's making an interesting assertion, return this response. */
-               if (port & 1)
-                 {
-                 *fully_qualified_name = namesuff + 1;
-                 return DNS_SUCCEED;
-                 }
-               }
+         *fully_qualified_name = namesuff + 1;
+         return DNS_SUCCEED;

          }
          }

-       return DNS_NOMATCH;

        }
        }

+      }
+    return DNS_NOMATCH;
+    }

 
   default:
 
   default:

-       if (type >= 0)
-         return dns_lookup(dnsa, name, type, fully_qualified_name);
+    if (type >= 0)
+      return dns_lookup(dnsa, name, type, fully_qualified_name);

   }
 
 /* Control should never reach here */
   }
 
 /* Control should never reach here */


@@ -1079,8 +1188,7 @@ return DNS_FAIL;
 *          Get address(es) from DNS record       *
 *************************************************/
 
 *          Get address(es) from DNS record       *
 *************************************************/
 

-/* The record type is either T_A for an IPv4 address or T_AAAA (or T_A6 when
-supported) for an IPv6 address.
+/* The record type is either T_A for an IPv4 address or T_AAAA for an IPv6 address.

 
 Argument:
   dnsa       the DNS answer block
 
 Argument:
   dnsa       the DNS answer block


@@ -1112,8 +1220,11 @@ else
   {
   if (rr->data + 16 <= dnsa_lim)
     {
   {
   if (rr->data + 16 <= dnsa_lim)
     {

+    struct in6_addr in6;
+    int i;
+    for (i = 0; i < 16; i++) in6.s6_addr[i] = rr->data[i];

     yield = store_get(sizeof(dns_address) + 50);
     yield = store_get(sizeof(dns_address) + 50);

-    inet_ntop(AF_INET6, US rr->data, CS yield->address, 50);
+    inet_ntop(AF_INET6, &in6, CS yield->address, 50);

     yield->next = NULL;
     }
   }
     yield->next = NULL;
     }
   }