s4/dns_common_replace: add comments about tombstones

Signed-off-by: Douglas Bagnall <douglas.bagnall@catalyst.net.nz>
Reviewed-by: Andrew Bartlett <abartlet@samba.org>

diff --git a/source4/dns_server/dnsserver_common.c b/source4/dns_server/dnsserver_common.c
index ef582a471c8ab72af4c4c9e7a2d5dd297a9106e9..5c5ec1f9ebd0c6a5511efe1adf4b8ba7fb33853d 100644 (file)
--- a/source4/dns_server/dnsserver_common.c
+++ b/source4/dns_server/dnsserver_common.c
@@ -1012,6 +1012,25 @@ WERROR dns_common_replace(struct ldb_context *samdb,
                enum ndr_err_code ndr_err;
 
                if (records[i].wType == DNS_TYPE_TOMBSTONE) {
+                       /*
+                        * There are two things that could be going on here.
+                        *
+                        * 1. We use a tombstone with EntombedTime == 0 for
+                        * passing deletion messages through the stack, and
+                        * this is the place we filter them out to perform
+                        * that deletion.
+                        *
+                        * 2. This node is tombstoned, with no records except
+                        * for a single tombstone, and it is just waiting to
+                        * disappear. In this case, unless the caller has
+                        * added a record, rec_count should be 1, and
+                        * el->num_values will end up at 0, and we will make
+                        * no changes. But if the caller has added a record,
+                        * we need to un-tombstone the node.
+                        *
+                        * It is not possible to add an explicit tombstone
+                        * record.
+                        */
                        if (records[i].data.EntombedTime != 0) {
                                was_tombstoned = true;
                        }
@@ -1065,6 +1084,10 @@ WERROR dns_common_replace(struct ldb_context *samdb,
        }
 
        if (el->num_values == 0) {
+               /*
+                * We get here if there are no records or all the records were
+                * tombstones.
+                */
                struct dnsp_DnssrvRpcRecord tbs;
                struct ldb_val *v = &el->values[el->num_values];
                enum ndr_err_code ndr_err;