Support of DNS domain for DHCP-less drivers

We set DNS domain either via interactve service or DHCP.
When interactive service is not used, for example,
when profiles are started by OpenVPNService, this option
is not working for DCO and wintun.

This implements setting DNS domain via WMIC command,
similar to implementation in interactive service.
This is done when:

 - interactive service is not used

 - DHCP is not used (ip-win32 is either NETSH or IPAPI,
   or IPv4 address is not pushed)

Github: fixes #306

Change-Id: Ic72a4ecd0414c0d7bf013415f52640fd122cb739
Signed-off-by: Lev Stipakov <lev@openvpn.net>
Acked-by: Selva Nair <selva.nair@gmail.com>
Message-Id: <20230406071546.1056-1-lstipakov@gmail.com>
URL: https://www.mail-archive.com/openvpn-devel@lists.sourceforge.net/msg26582.html
Signed-off-by: Gert Doering <gert@greenie.muc.de>

src/openvpn/tun.c

@@ -84,6 +84,8 @@ static void netsh_set_dns6_servers(const struct in6_addr *addr_list,
 
 static void netsh_command(const struct argv *a, int n, int msglevel);
 
+static void exec_command(const char *prefix, const struct argv *a, int n, int msglevel);
+
 static const char *netsh_get_id(const char *dev_node, struct gc_arena *gc);
 
 static bool
@@ -324,6 +326,22 @@ do_set_mtu_service(const struct tuntap *tt, const short family, const int mtu)
     return ret;
 }
 
+static void
+do_dns_domain_wmic(bool add, const struct tuntap *tt)
+{
+    if (!tt->options.domain)
+    {
+        return;
+    }
+
+    struct argv argv = argv_new();
+    argv_printf(&argv, "%s%s nicconfig where (InterfaceIndex=%ld) call SetDNSDomain %s",
+                get_win_sys_path(), WMIC_PATH_SUFFIX, tt->adapter_index, add ? tt->options.domain : "");
+    exec_command("WMIC", &argv, 1, M_WARN);
+
+    argv_free(&argv);
+}
+
 #endif /* ifdef _WIN32 */
 
 #ifdef TARGET_SOLARIS
@@ -1190,6 +1208,11 @@ do_ifconfig_ipv6(struct tuntap *tt, const char *ifname, int tun_mtu,
         /* set ipv6 dns servers if any are specified */
         netsh_set_dns6_servers(tt->options.dns6, tt->options.dns6_len, tt->adapter_index);
         windows_set_mtu(tt->adapter_index, AF_INET6, tun_mtu);
+
+        if (!tt->did_ifconfig_setup)
+        {
+            do_dns_domain_wmic(true, tt);
+        }
     }
 #else /* platforms we have no IPv6 code for */
     msg(M_FATAL, "Sorry, but I don't know how to do IPv6 'ifconfig' commands on this operating system.  You should ifconfig your TUN/TAP device manually or use an --up script.");
@@ -1535,11 +1558,18 @@ do_ifconfig_ipv4(struct tuntap *tt, const char *ifname, int tun_mtu,
         do_dns_service(true, AF_INET, tt);
         do_dns_domain_service(true, tt);
     }
-    else if (tt->options.ip_win32_type == IPW32_SET_NETSH)
+    else
     {
-        netsh_ifconfig(&tt->options, tt->adapter_index, tt->local,
-                       tt->adapter_netmask, NI_IP_NETMASK|NI_OPTIONS);
+        if (tt->options.ip_win32_type == IPW32_SET_NETSH)
+        {
+            netsh_ifconfig(&tt->options, tt->adapter_index, tt->local,
+                           tt->adapter_netmask, NI_IP_NETMASK | NI_OPTIONS);
+        }
+
+        do_dns_domain_wmic(true, tt);
     }
+
+
     if (tt->options.msg_channel)
     {
         do_set_mtu_service(tt, AF_INET, tun_mtu);
@@ -5238,29 +5268,31 @@ dhcp_renew(const struct tuntap *tt)
     }
 }
 
-/*
- * netsh functions
- */
-
 static void
-netsh_command(const struct argv *a, int n, int msglevel)
+exec_command(const char *prefix, const struct argv *a, int n, int msglevel)
 {
     int i;
     for (i = 0; i < n; ++i)
     {
         bool status;
         management_sleep(0);
         netcmd_semaphore_lock();
-        argv_msg_prefix(M_INFO, a, "NETSH");
-        status = openvpn_execve_check(a, NULL, 0, "ERROR: netsh command failed");
+        argv_msg_prefix(M_INFO, a, prefix);
+        status = openvpn_execve_check(a, NULL, 0, "ERROR: command failed");
         netcmd_semaphore_release();
         if (status)
         {
             return;
         }
         management_sleep(4);
     }
-    msg(msglevel, "NETSH: command failed");
+    msg(msglevel, "%s: command failed", prefix);
+}
+
+static void
+netsh_command(const struct argv *a, int n, int msglevel)
+{
+    exec_command("NETSH", a, n, msglevel);
 }
 
 void
@@ -6927,6 +6959,11 @@ close_tun(struct tuntap *tt, openvpn_net_ctx_t *ctx)
         }
         else
         {
+            if (!tt->did_ifconfig_setup)
+            {
+                do_dns_domain_wmic(false, tt);
+            }
+
             netsh_delete_address_dns(tt, true, &gc);
         }
     }
@@ -6947,9 +6984,14 @@ close_tun(struct tuntap *tt, openvpn_net_ctx_t *ctx)
             do_dns_service(false, AF_INET, tt);
             do_address_service(false, AF_INET, tt);
         }
-        else if (tt->options.ip_win32_type == IPW32_SET_NETSH)
+        else
         {
-            netsh_delete_address_dns(tt, false, &gc);
+            do_dns_domain_wmic(false, tt);
+
+            if (tt->options.ip_win32_type == IPW32_SET_NETSH)
+            {
+                netsh_delete_address_dns(tt, false, &gc);
+            }
         }
     }
 

src/openvpn/win32.h

@@ -38,6 +38,7 @@
 #define WIN_ROUTE_PATH_SUFFIX "\\system32\\route.exe"
 #define WIN_IPCONFIG_PATH_SUFFIX "\\system32\\ipconfig.exe"
 #define WIN_NET_PATH_SUFFIX "\\system32\\net.exe"
+#define WMIC_PATH_SUFFIX "\\system32\\wbem\\wmic.exe"
 
 /*
  * Win32-specific OpenVPN code, targeted at the mingw