[libvirt] [PATCH] virNetworkDefUpdateDNSHost: Require both IP and a hostname to match

[W. Trevor King]

Since fc19a0059 (network: backend functions for updating network dns
host/srv/txt, 2012-11-12), the matching logic for various network
components has been:

1) for HOST records, it's considered a match if the IP address or any
   of the hostnames of an existing record matches.

2) for SRV records, it's a match if all of
   domain+service+protocol+target *which have been specified* are
   matched.

3) for TXT records, there is only a single field to match - name
   (value can be the same for multiple records, and isn't considered a
   search term), so by definition there can be no ambiguous matches.

But HOST records can have the same hostname for multiple records
(similar to TXT records with the same value).  The value that needs to
be distinct for HOST records is the IP address.  This commit updates
the matching logic to only consider the IP address.  Compared to the
previous HOST logic:

1. You can now delete entries from an existing network like:

     <dns>
       <host ip="192.168.1.1">
         <hostname>example</hostname>
       </host>
       <host ip="192.168.1.2">
         <hostname>example</hostname>
       </host>
     </dns>

  with input like:

       <host ip="192.168.1.1">
       </host>

  or:

       <host ip="192.168.1.1">
         <hostname>example</hostname>
       </host>

  Previously, only the former would work (the latter used to raise
  "multiple matching DNS HOST records were found in network").

2. You can no longer remove entries by hostname alone.  Previously,
   you may have been able to remove an entry from an existing network
   like:

     <dns>
       <host ip="192.168.1.1">
         <hostname>example-1</hostname>
       </host>
       <host ip="192.168.1.2">
         <hostname>example-2</hostname>
       </host>
     </dns>

   with input like:

     <host name="example">
       <hostname>example-1</hostname>
     </host>

   using the 'name' property to get through the partialOkay check in
   virNetworkDHCPHostDefParseXML.  Now that input will raise "Missing
   IP address in network '%s' DNS HOST record".

3. You can now add multiple entries with a common hostname (as long as
   they have distinct IP addresses).  Previously, adding:

     <host ip="192.168.1.1">
       <hostname>example</hostname>
     </host>

   to an existing:

     <host ip="192.168.1.2">
       <hostname>example</hostname>
     </host>

   would have raised "there is already at least one DNS HOST record
   with a matching field in network".
---

I'm actually not clear on whether the 'ip' attribute is required to be
unique or not.  If not, maybe the logic should be:

* Deletes with just an IP remove all <host> entries that match that
  IP.
* Deletes with just a hostname remove all <hostname> entries that
  match that hostname.
* Deletes with an IP and a hostname remove matching <hostname> entries
  from <host> entries which match the IP.
* If <hostname> removal completely empties a <host>, the <host> is
  also removed.

Thoughts?

 src/conf/network_conf.c | 31 ++++++++++---------------------
 1 file changed, 10 insertions(+), 21 deletions(-)

diff --git a/src/conf/network_conf.c b/src/conf/network_conf.c
index 39a13b4..8ed62ac 100644
--- a/src/conf/network_conf.c
+++ b/src/conf/network_conf.c
@@ -587,14 +587,14 @@ virNetworkDNSHostDefParseXML(const char *networkName,
     xmlNodePtr cur;
     char *ip;
 
-    if (!(ip = virXMLPropString(node, "ip")) && !partialOkay) {
+    if (!(ip = virXMLPropString(node, "ip"))) {
         virReportError(VIR_ERR_XML_DETAIL,
                        _("Missing IP address in network '%s' DNS HOST record"),
                        networkName);
         goto error;
     }
 
-    if (ip && (virSocketAddrParse(&def->ip, ip, AF_UNSPEC) < 0)) {
+    if (virSocketAddrParse(&def->ip, ip, AF_UNSPEC) < 0) {
         virReportError(VIR_ERR_XML_DETAIL,
                        _("Invalid IP address in network '%s' DNS HOST record"),
                        networkName);
@@ -603,6 +603,13 @@ virNetworkDNSHostDefParseXML(const char *networkName,
     }
     VIR_FREE(ip);
 
+    if (!VIR_SOCKET_ADDR_VALID(&def->ip)) {
+        virReportError(VIR_ERR_XML_DETAIL,
+                       _("Invalid IP address in network '%s' DNS HOST record"),
+                       networkName);
+        goto error;
+    }
+
     cur = node->children;
     while (cur != NULL) {
         if (cur->type == XML_ELEMENT_NODE &&
@@ -631,13 +638,6 @@ virNetworkDNSHostDefParseXML(const char *networkName,
         goto error;
     }
 
-    if (!VIR_SOCKET_ADDR_VALID(&def->ip) && def->nnames == 0) {
-        virReportError(VIR_ERR_XML_DETAIL,
-                       _("Missing ip and hostname in network '%s' DNS HOST record"),
-                       networkName);
-        goto error;
-    }
-
     return 0;
 
  error:
@@ -3334,18 +3334,7 @@ virNetworkDefUpdateDNSHost(virNetworkDefPtr def,
         goto cleanup;
 
     for (i = 0; i < dns->nhosts; i++) {
-        bool foundThisTime = false;
-
-        if (virSocketAddrEqual(&host.ip, &dns->hosts[i].ip))
-            foundThisTime = true;
-
-        for (j = 0; j < host.nnames && !foundThisTime; j++) {
-            for (k = 0; k < dns->hosts[i].nnames && !foundThisTime; k++) {
-                if (STREQ(host.names[j], dns->hosts[i].names[k]))
-                    foundThisTime = true;
-            }
-        }
-        if (foundThisTime) {
+        if virSocketAddrEqual(&host.ip, &dns->hosts[i].ip) {
             foundCt++;
             foundIdx = i;
         }
-- 
1.8.3.1