- DDNS removal routines were updated so that the DHCID is not removed until

  the client has been deprived of all A and AAAA records (not only the last
  one of either of those).  This resolves a bug where dual stack clients
  would not be able to regain their names after either expiration event.
  [ISC-Bugs #18716]

diff --git a/RELNOTES b/RELNOTES
index fcf5f4e1f185a4db371d016ffe1f9641ee902a6f..50064319f173011ca527d9d5734f4efb3fe3a6f5 100644 (file)
--- a/RELNOTES
+++ b/RELNOTES
@@ -105,6 +105,11 @@ work on other platforms. Please report any problems and suggested fixes to
 - A dhclient-script for MacOS X has been included, which enables
   'dhclient -6' support.
 
+- DDNS removal routines were updated so that the DHCID is not removed until
+  the client has been deprived of all A and AAAA records (not only the last
+  one of either of those).  This resolves a bug where dual stack clients
+  would not be able to regain their names after either expiration event.
+
                        Changes since 4.1.0a1
 
 - Corrected list of failover state values in dhcpd man page.

diff --git a/common/dns.c b/common/dns.c
index 878caf5beddd8c04b15471e0d6cc1b841ea70450..25cfb598f699cc01ef4d71d8fea031f1b3e97937 100644 (file)
--- a/common/dns.c
+++ b/common/dns.c
@@ -859,7 +859,7 @@ ddns_remove_fwd(struct data_string *ddns_fwd_name,
 
 
        /*
-        * A RR matches the expiring lease.
+        * Address RR (A/AAAA) matches the expiring lease.
         */
        updrec = minires_mkupdrec (S_PREREQ,
                                   (const char *)ddns_fwd_name -> data,
@@ -877,7 +877,7 @@ ddns_remove_fwd(struct data_string *ddns_fwd_name,
 
 
        /*
-        * Delete appropriate A RR.
+        * Delete appropriate Address RR (A/AAAA).
         */
        updrec = minires_mkupdrec (S_UPDATE,
                                   (const char *)ddns_fwd_name -> data,
@@ -926,20 +926,27 @@ ddns_remove_fwd(struct data_string *ddns_fwd_name,
                minires_freeupdrec (updrec);
        }
 
-       /* If the deletion of the A succeeded, and there are no A records
-          left for this domain, then we can blow away the DHCID record
-          as well.   We can't blow away the DHCID record above because
-          it's possible that more than one A has been added to this
-          domain name. */
+       /*
+        * If the deletion of the desired address succeeded (its A or AAAA
+        * RR was removed above), and there are zero other A or AAAA records
+        * left for this domain, then we can delete the DHCID record as well.
+        * We can't delete the DHCID record above because it's possible the
+        * client has more than one valid address added to this domain name,
+        * by this or other DHCP servers.
+        *
+        * Essentially, this final update is a cleanup operation that is only
+        * intended to succeed after the last address has been removed from
+        * DNS (which is only expected to happen after the client is not
+        * reasonably in possession of those addresses).
+        */
        ISC_LIST_INIT (updqueue);
 
        /*
         * A RR does not exist.
         */
-       updrec = minires_mkupdrec (S_PREREQ,
-                                  (const char *)ddns_fwd_name -> data,
-                                  C_IN, ddns_address_type, 0);
-       if (!updrec) {
+       updrec = minires_mkupdrec(S_PREREQ, (const char *)ddns_fwd_name->data,
+                                 C_IN, T_A, 0);
+       if (updrec == NULL) {
                result = ISC_R_NOMEMORY;
                goto error;
        }
@@ -950,6 +957,23 @@ ddns_remove_fwd(struct data_string *ddns_fwd_name,
 
        ISC_LIST_APPEND (updqueue, updrec, r_link);
 
+       /*
+        * AAAA RR does not exist.
+        */
+       updrec = minires_mkupdrec(S_PREREQ, (const char *)ddns_fwd_name->data,
+                                 C_IN, T_AAAA, 0);
+
+       if (updrec == NULL) {
+               result = ISC_R_NOMEMORY;
+               goto error;
+       }
+
+       updrec->r_data = NULL;
+       updrec->r_size = 0;
+       updrec->r_opcode = NXRRSET;
+
+       ISC_LIST_APPEND(updqueue, updrec, r_link);
+
        /*
         * Delete appropriate DHCID RR.
         */