util: refactor iptables command construction into multiple steps

Instead of creating an iptables command in one shot, do it in steps
so we can add conditional options like physdev and protocol.

This removes code duplication while keeping existing behaviour.
Signed-off-by: NNatanael Copa <ncopa@alpinelinux.org>
Signed-off-by: NEric Blake <eblake@redhat.com>

src/util/viriptables.c

 /*
  * viriptables.c: helper APIs for managing iptables
  *
- * Copyright (C) 2007-2012 Red Hat, Inc.
+ * Copyright (C) 2007-2013 Red Hat, Inc.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Lesser General Public
@@ -129,15 +129,10 @@ iptRulesNew(const char *table,
     return NULL;
 }
 
-static int ATTRIBUTE_SENTINEL
-iptablesAddRemoveRule(iptRules *rules, int family, int action,
-                      const char *arg, ...)
+static virCommandPtr
+iptablesCommandNew(iptRules *rules, int family, int action)
 {
-    va_list args;
-    int ret;
     virCommandPtr cmd = NULL;
-    const char *s;
-
 #if HAVE_FIREWALLD
     virIpTablesInitialize();
     if (firewall_cmd_path) {
@@ -154,16 +149,36 @@ iptablesAddRemoveRule(iptRules *rules, int family, int action,
 
     virCommandAddArgList(cmd, "--table", rules->table,
                          action == ADD ? "--insert" : "--delete",
-                         rules->chain, arg, NULL);
+                         rules->chain, NULL);
+    return cmd;
+}
+
+static int
+iptablesCommandRunAndFree(virCommandPtr cmd)
+{
+    int ret;
+    ret = virCommandRun(cmd, NULL);
+    virCommandFree(cmd);
+    return ret;
+}
+
+static int ATTRIBUTE_SENTINEL
+iptablesAddRemoveRule(iptRules *rules, int family, int action,
+                      const char *arg, ...)
+{
+    va_list args;
+    virCommandPtr cmd = NULL;
+    const char *s;
+
+    cmd = iptablesCommandNew(rules, family, action);
+    virCommandAddArg(cmd, arg);
 
     va_start(args, arg);
     while ((s = va_arg(args, const char *)))
         virCommandAddArg(cmd, s);
     va_end(args);
 
-    ret = virCommandRun(cmd, NULL);
-    virCommandFree(cmd);
-    return ret;
+    return iptablesCommandRunAndFree(cmd);
 }
 
 /**
@@ -372,28 +387,24 @@ iptablesForwardAllowOut(iptablesContext *ctx,
 {
     int ret;
     char *networkstr;
+    virCommandPtr cmd = NULL;
 
     if (!(networkstr = iptablesFormatNetwork(netaddr, prefix)))
         return -1;
 
-    if (physdev && physdev[0]) {
-        ret = iptablesAddRemoveRule(ctx->forward_filter,
-                                    VIR_SOCKET_ADDR_FAMILY(netaddr),
-                                    action,
-                                    "--source", networkstr,
-                                    "--in-interface", iface,
-                                    "--out-interface", physdev,
-                                    "--jump", "ACCEPT",
-                                    NULL);
-    } else {
-        ret = iptablesAddRemoveRule(ctx->forward_filter,
-                                    VIR_SOCKET_ADDR_FAMILY(netaddr),
-                                    action,
-                                    "--source", networkstr,
-                                    "--in-interface", iface,
-                                    "--jump", "ACCEPT",
-                                    NULL);
-    }
+    cmd = iptablesCommandNew(ctx->forward_filter,
+                             VIR_SOCKET_ADDR_FAMILY(netaddr),
+                             action);
+    virCommandAddArgList(cmd,
+                         "--source", networkstr,
+                         "--in-interface", iface, NULL);
+
+    if (physdev && physdev[0])
+        virCommandAddArgList(cmd, "--out-interface", physdev, NULL);
+
+    virCommandAddArgList(cmd, "--jump", "ACCEPT", NULL);
+
+    ret = iptablesCommandRunAndFree(cmd);
     VIR_FREE(networkstr);
     return ret;
 }
@@ -799,6 +810,7 @@ iptablesForwardMasquerade(iptablesContext *ctx,
 {
     int ret;
     char *networkstr;
+    virCommandPtr cmd = NULL;
 
     if (!(networkstr = iptablesFormatNetwork(netaddr, prefix)))
         return -1;
@@ -812,49 +824,23 @@ iptablesForwardMasquerade(iptablesContext *ctx,
         return -1;
     }
 
-    if (protocol && protocol[0]) {
-        if (physdev && physdev[0]) {
-            ret = iptablesAddRemoveRule(ctx->nat_postrouting,
-                                        AF_INET,
-                                        action,
-                                        "--source", networkstr,
-                                        "-p", protocol,
-                                        "!", "--destination", networkstr,
-                                        "--out-interface", physdev,
-                                        "--jump", "MASQUERADE",
-                                        "--to-ports", "1024-65535",
-                                        NULL);
-        } else {
-            ret = iptablesAddRemoveRule(ctx->nat_postrouting,
-                                        AF_INET,
-                                        action,
-                                        "--source", networkstr,
-                                        "-p", protocol,
-                                        "!", "--destination", networkstr,
-                                        "--jump", "MASQUERADE",
-                                        "--to-ports", "1024-65535",
-                                        NULL);
-        }
-    } else {
-        if (physdev && physdev[0]) {
-            ret = iptablesAddRemoveRule(ctx->nat_postrouting,
-                                        AF_INET,
-                                        action,
-                                        "--source", networkstr,
-                                        "!", "--destination", networkstr,
-                                        "--out-interface", physdev,
-                                        "--jump", "MASQUERADE",
-                                        NULL);
-        } else {
-            ret = iptablesAddRemoveRule(ctx->nat_postrouting,
-                                        AF_INET,
-                                        action,
-                                        "--source", networkstr,
-                                        "!", "--destination", networkstr,
-                                        "--jump", "MASQUERADE",
-                                        NULL);
-        }
-    }
+    cmd = iptablesCommandNew(ctx->nat_postrouting, AF_INET, action);
+    virCommandAddArgList(cmd, "--source", networkstr, NULL);
+
+    if (protocol && protocol[0])
+        virCommandAddArgList(cmd, "-p", protocol, NULL);
+
+    virCommandAddArgList(cmd, "!", "--destination", networkstr, NULL);
+
+    if (physdev && physdev[0])
+        virCommandAddArgList(cmd, "--out-interface", physdev, NULL);
+
+    virCommandAddArgList(cmd, "--jump", "MASQUERADE", NULL);
+
+    if (protocol && protocol[0])
+        virCommandAddArgList(cmd, "--to-ports", "1024-65535", NULL);
+
+    ret = iptablesCommandRunAndFree(cmd);
     VIR_FREE(networkstr);
     return ret;
 }