network: implement backend of virNetworkUpdate(IP_DHCP_HOST)

This patch fills in the first implementation for one of the
virNetworkUpdate sections. With this code, you can now add/delete/edit
<host> entries in a network's <ip> address <dhcp> element (by
specifying a section of VIR_NETWORK_SECTION_IP_DHCP_HOST).

If you pass in a parentIndex of -1, the code will automatically find
the one ip element that has a <dhcp> section and make the updates
there. Otherwise, you can specify an index >= 0, and libvirt will look
for that particular instance of <ip> in the network, and modify its
<dhcp> element. (This currently isn't very useful, because libvirt
only supports having dhcp information on a single IP address, but that
could change in the future).

When adding a new host entry
(VIR_NETWORK_UPDATE_COMMAND_ADD_(FIRST|LAST)), the existing entries
will be compared to the new entry, and if any non-empty attribute
matches, the add will fail. When updating an existing entry
(VIR_NETWORK_UPDATE_COMMAND_MODIFY), the mac address or name will be
used to find the existing entry, and other fields will only be updated
(note there is some potential for ambiguity here if you specify the
mac address from one entry and the name from another).  When deleting
an existing entry (VIR_NETWORK_UPDATE_COMMAND_DELETE), all non-empty
attributes in the supplied xml arg will be compared - all of them must
match before libvirt will delete the host.

The xml should be a fully formed <host> element as it would appear in
a network definition, e.g. "<host mac=00:11:22:33:44:55 ip=10.1.23.22
name='testbox'/>" (when adding/updating, ip and one of mac|name is
required; when deleting, you can specify any one, two, or all
attributes, but they all must match the target element).

As with the update of any other section, you can choose to affect the
live config (with flag VIR_NETWORK_UPDATE_AFFECT_LIVE), the persistent
config (VIR_NETWORK_UPDATE_AFFECT_CONFIG), or both. If you've chosen
to affect the live config, those changes will take effect immediately,
with no need to destroy/restart the network.

An example of adding a host entry:

   virNetworkUpdate(net, VIR_NETWORK_UPDATE_COMMAND_ADD_LAST,
                     VIR_NETWORK_SECTION_IP_DHCP_HOST, -1,
                    "<host mac='00:11:22:33:44:55' ip='192.168.122.5'/>",
                    VIR_NETWORK_UPDATE_AFFECT_LIVE
                    | VIR_NETWORK_UPDATE_AFFECT_CONFIG);

To delete that same entry:

   virNetworkUpdate(net, VIR_NETWORK_UPDATE_COMMAND_DELETE,
                    VIR_NETWORK_SECTION_IP_DHCP_HOST, -1,
                    "<host mac='00:11:22:33:44:55'/>",
                    VIR_NETWORK_UPDATE_AFFECT_LIVE
                    | VIR_NETWORK_UPDATE_AFFECT_CONFIG);

(you could also delete it by replacing "mac='00:11:22:33:44:55'" with
"ip='192.168.122.5'".)

1 files changed, 173 insertions, 7 deletions

diff --git a/src/conf/network_conf.c b/src/conf/network_conf.c
index 2a65f1db9..db398ae89 100644
--- a/src/conf/network_conf.c
+++ b/src/conf/network_conf.c
@@ -2261,7 +2261,6 @@ virNetworkDefUpdateNoSupport(virNetworkDefPtr def, const char *section)
                    section, def->name);
 }
 
-#if 0
 static int
 virNetworkDefUpdateCheckElementName(virNetworkDefPtr def,
                                     xmlNodePtr node,
@@ -2276,7 +2275,6 @@ virNetworkDefUpdateCheckElementName(virNetworkDefPtr def,
     }
     return 0;
 }
-#endif
 
 static int
 virNetworkDefUpdateBridge(virNetworkDefPtr def,
@@ -2314,16 +2312,184 @@ virNetworkDefUpdateIP(virNetworkDefPtr def,
     return -1;
 }
 
+static virNetworkIpDefPtr
+virNetworkIpDefByIndex(virNetworkDefPtr def, int parentIndex)
+{
+    virNetworkIpDefPtr ipdef = NULL;
+    int ii;
+
+    /* first find which ip element's dhcp host list to work on */
+    if (parentIndex >= 0) {
+        ipdef = virNetworkDefGetIpByIndex(def, AF_UNSPEC, parentIndex);
+        if (!(ipdef &&
+              VIR_SOCKET_ADDR_IS_FAMILY(&ipdef->address, AF_INET))) {
+            virReportError(VIR_ERR_OPERATION_INVALID,
+                           _("couldn't update dhcp host entry - "
+                             "no <ip family='ipv4'> "
+                             "element found at index %d in network '%s'"),
+                           parentIndex, def->name);
+        }
+        return ipdef;
+    }
+
+    /* -1 means "find the most appropriate", which in this case
+     * means the one and only <ip> that has <dhcp> element
+     */
+    for (ii = 0;
+         (ipdef = virNetworkDefGetIpByIndex(def, AF_UNSPEC, ii));
+         ii++) {
+        if (VIR_SOCKET_ADDR_IS_FAMILY(&ipdef->address, AF_INET) &&
+            (ipdef->nranges || ipdef->nhosts)) {
+            break;
+        }
+    }
+    if (!ipdef)
+        ipdef = virNetworkDefGetIpByIndex(def, AF_INET, 0);
+    if (!ipdef) {
+        virReportError(VIR_ERR_OPERATION_INVALID,
+                       _("couldn't update dhcp host entry - "
+                         "no <ip family='ipv4'> "
+                         "element found in network '%s'"), def->name);
+    }
+    return ipdef;
+}
+
 static int
 virNetworkDefUpdateIPDHCPHost(virNetworkDefPtr def,
-                              unsigned int command ATTRIBUTE_UNUSED,
-                              int parentIndex ATTRIBUTE_UNUSED,
-                              xmlXPathContextPtr ctxt ATTRIBUTE_UNUSED,
+                              unsigned int command,
+                              int parentIndex,
+                              xmlXPathContextPtr ctxt,
                               /* virNetworkUpdateFlags */
                               unsigned int fflags ATTRIBUTE_UNUSED)
 {
-    virNetworkDefUpdateNoSupport(def, "ip dhcp host");
-    return -1;
+    int ii, ret = -1;
+    virNetworkIpDefPtr ipdef = virNetworkIpDefByIndex(def, parentIndex);
+    virNetworkDHCPHostDef host;
+
+    memset(&host, 0, sizeof(host));
+
+    if (virNetworkDefUpdateCheckElementName(def, ctxt->node, "host") < 0)
+        goto cleanup;
+
+    /* ipdef is the ip element that needs its host array updated */
+    if (!ipdef)
+        goto cleanup;
+
+    /* parse the xml into a virNetworkDHCPHostDef */
+    if (command == VIR_NETWORK_UPDATE_COMMAND_MODIFY) {
+
+        if (virNetworkDHCPHostDefParse(def->name, ctxt->node, &host, false) < 0)
+            goto cleanup;
+
+        /* search for the entry with this (mac|name),
+         * and update the IP+(mac|name) */
+        for (ii = 0; ii < ipdef->nhosts; ii++) {
+            if ((host.mac &&
+                 !virMacAddrCompare(host.mac, ipdef->hosts[ii].mac)) ||
+                (host.name &&
+                 STREQ_NULLABLE(host.name, ipdef->hosts[ii].name))) {
+                break;
+            }
+        }
+
+        if (ii == ipdef->nhosts) {
+            virReportError(VIR_ERR_OPERATION_INVALID,
+                           _("couldn't locate an existing dhcp host entry with "
+                             "\"mac='%s'\" in network '%s'"),
+                           host.mac, def->name);
+            goto cleanup;
+        }
+
+        /* clear the existing hosts entry, move the new one in its place,
+         * then clear out the extra copy to get rid of the duplicate pointers
+         * to its data (mac and name strings).
+         */
+        virNetworkDHCPHostDefClear(&ipdef->hosts[ii]);
+        ipdef->hosts[ii] = host;
+        memset(&host, 0, sizeof(host));
+
+    } else if ((command == VIR_NETWORK_UPDATE_COMMAND_ADD_FIRST) ||
+               (command == VIR_NETWORK_UPDATE_COMMAND_ADD_LAST)) {
+
+        if (virNetworkDHCPHostDefParse(def->name, ctxt->node, &host, true) < 0)
+            goto cleanup;
+
+        /* log error if an entry with same name/address/ip already exists */
+        for (ii = 0; ii < ipdef->nhosts; ii++) {
+            if ((host.mac &&
+                 !virMacAddrCompare(host.mac, ipdef->hosts[ii].mac)) ||
+                (host.name &&
+                 STREQ_NULLABLE(host.name, ipdef->hosts[ii].name)) ||
+                (VIR_SOCKET_ADDR_VALID(&host.ip) &&
+                 virSocketAddrEqual(&host.ip, &ipdef->hosts[ii].ip))) {
+                char *ip = virSocketAddrFormat(&host.ip);
+
+                virReportError(VIR_ERR_OPERATION_INVALID,
+                               _("there is an existing dhcp host entry in "
+                                 "network '%s' that matches "
+                                 "\"<host mac='%s' name='%s' ip='%s'/>\""),
+                               def->name, host.mac, host.name,
+                               ip ? ip : "unknown");
+                VIR_FREE(ip);
+                goto cleanup;
+            }
+        }
+        /* add to beginning/end of list */
+        if (VIR_REALLOC_N(ipdef->hosts, ipdef->nhosts +1) < 0) {
+            virReportOOMError();
+            goto cleanup;
+        }
+
+        if (command == VIR_NETWORK_UPDATE_COMMAND_ADD_LAST) {
+
+            ipdef->hosts[ipdef->nhosts] = host;
+            ipdef->nhosts++;
+            memset(&host, 0, sizeof(host));
+
+        } else { /* implied (command == VIR_NETWORK_UPDATE_COMMAND_ADD_FIRST) */
+
+            memmove(ipdef->hosts + 1, ipdef->hosts,
+                    sizeof(ipdef->hosts) * ipdef->nhosts);
+            ipdef->hosts[0] = host;
+            ipdef->nhosts++;
+            memset(&host, 0, sizeof(host));
+        }
+
+    } else if (command == VIR_NETWORK_UPDATE_COMMAND_DELETE) {
+
+        if (virNetworkDHCPHostDefParse(def->name, ctxt->node, &host, false) < 0)
+            goto cleanup;
+
+        /* find matching entry - all specified attributes must match */
+        for (ii = 0; ii < ipdef->nhosts; ii++) {
+            if ((!host.mac ||
+                 !virMacAddrCompare(host.mac, ipdef->hosts[ii].mac)) &&
+                (!host.name ||
+                 STREQ_NULLABLE(host.name, ipdef->hosts[ii].name)) &&
+                (!VIR_SOCKET_ADDR_VALID(&host.ip) ||
+                 virSocketAddrEqual(&host.ip, &ipdef->hosts[ii].ip))) {
+                break;
+            }
+        }
+        if (ii == ipdef->nhosts) {
+            virReportError(VIR_ERR_OPERATION_INVALID,
+                           _("couldn't locate a matching dhcp host entry "
+                             "in network '%s'"), def->name);
+            goto cleanup;
+        }
+
+        /* remove it */
+        virNetworkDHCPHostDefClear(&ipdef->hosts[ii]);
+        memmove(ipdef->hosts + ii, ipdef->hosts + ii + 1,
+                sizeof(ipdef->hosts) * ipdef->nhosts - ii - 1);
+        ipdef->nhosts--;
+        ignore_value(VIR_REALLOC_N(ipdef->hosts, ipdef->nhosts));
+    }
+
+    ret = 0;
+cleanup:
+    virNetworkDHCPHostDefClear(&host);
+    return ret;
 }
 
 static int