nwfilter: Fix support for trusted DHCP servers

Fix the support for trusted DHCP server in the ebtables code's
hard-coded function applying DHCP only filtering rules:
Rather than using a char * use the more flexible
virNWFilterVarValuePtr that contains the trusted DHCP server(s)
IP address. Process all entries.

Since all callers so far provided NULL as parameter, no changes
are necessary in any other code.

src/conf/nwfilter_conf.h

@@ -625,7 +625,7 @@ typedef int (*virNWFilterApplyBasicRules)(const char *ifname,
 
 typedef int (*virNWFilterApplyDHCPOnlyRules)(const char *ifname,
                                              const unsigned char *macaddr,
-                                             const char *dhcpserver,
+                                             virNWFilterVarValuePtr dhcpsrvs,
                                              bool leaveTemporary);
 
 typedef int (*virNWFilterRemoveBasicRules)(const char *ifname);

src/nwfilter/nwfilter_ebiptables_driver.c

@@ -3195,7 +3195,7 @@ tear_down_tmpebchains:
  * @ifname: name of the backend-interface to which to apply the rules
  * @macaddr: MAC address the VM is using in packets sent through the
  *    interface
- * @dhcpserver: The DHCP server from which the VM may receive traffic
+ * @dhcpsrvrs: The DHCP server(s) from which the VM may receive traffic
  *    from; may be NULL
  * @leaveTemporary: Whether to leave the table names with their temporary
  *    names (true) or also perform the renaming to their final names as
@@ -3209,14 +3209,15 @@ tear_down_tmpebchains:
 static int
 ebtablesApplyDHCPOnlyRules(const char *ifname,
                            const unsigned char *macaddr,
-                           const char *dhcpserver,
+                           virNWFilterVarValuePtr dhcpsrvrs,
                            bool leaveTemporary)
 {
     virBuffer buf = VIR_BUFFER_INITIALIZER;
     char chain_in [MAX_CHAINNAME_LENGTH],
          chain_out[MAX_CHAINNAME_LENGTH];
     char macaddr_str[VIR_MAC_STRING_BUFLEN];
-    char *srcIPParam = NULL;
+    unsigned int idx = 0;
+    unsigned int num_dhcpsrvrs;
 
     if (!ebtables_cmd_path) {
         virNWFilterReportError(VIR_ERR_INTERNAL_ERROR, "%s",
@@ -3225,15 +3226,6 @@ ebtablesApplyDHCPOnlyRules(const char *ifname,
         return -1;
     }
 
-    if (dhcpserver) {
-        virBufferAsprintf(&buf, " --ip-src %s", dhcpserver);
-        if (virBufferError(&buf)) {
-            virBufferFreeAndReset(&buf);
-            return -1;
-        }
-        srcIPParam = virBufferContentAndReset(&buf);
-    }
-
     virMacAddrFormat(macaddr, macaddr_str);
 
     ebiptablesAllTeardown(ifname);
@@ -3267,6 +3259,24 @@ ebtablesApplyDHCPOnlyRules(const char *ifname,
                       chain_in,
                       CMD_STOPONERR(1));
 
+    num_dhcpsrvrs = (dhcpsrvrs != NULL)
+                    ? virNWFilterVarValueGetCardinality(dhcpsrvrs)
+                    : 0;
+
+    while (true) {
+        char *srcIPParam = NULL;
+
+        if (idx < num_dhcpsrvrs) {
+            const char *dhcpserver;
+
+            dhcpserver = virNWFilterVarValueGetNthValue(dhcpsrvrs, idx);
+
+            if (virAsprintf(&srcIPParam, "--ip-src %s", dhcpserver) < 0) {
+                virReportOOMError();
+                goto tear_down_tmpebchains;
+            }
+        }
+
         virBufferAsprintf(&buf,
                           CMD_DEF("$EBT -t nat -A %s"
                                   " -d %s"
@@ -3282,6 +3292,14 @@ ebtablesApplyDHCPOnlyRules(const char *ifname,
                           srcIPParam != NULL ? srcIPParam : "",
                           CMD_STOPONERR(1));
 
+        VIR_FREE(srcIPParam);
+
+        if (idx == num_dhcpsrvrs)
+            break;
+
+        idx++;
+    }
+
     virBufferAsprintf(&buf,
                       CMD_DEF("$EBT -t nat -A %s -j DROP") CMD_SEPARATOR
                       CMD_EXEC
@@ -3301,8 +3319,6 @@ ebtablesApplyDHCPOnlyRules(const char *ifname,
     if (ebiptablesExecCLI(&buf, NULL, NULL) < 0)
         goto tear_down_tmpebchains;
 
-    VIR_FREE(srcIPParam);
-
     return 0;
 
 tear_down_tmpebchains:
@@ -3312,8 +3328,6 @@ tear_down_tmpebchains:
                            "%s",
                            _("Some rules could not be created."));
 
-    VIR_FREE(srcIPParam);
-
     return -1;
 }