recent change to ifconfig breaks OpenVPN?

[Stefan Bethke]

(Moving the discussion to -ports.)

Am 31.07.2009 um 00:57 schrieb Matthias Andree:

> Am 31.07.2009, 00:36 Uhr, schrieb Bjoern A. Zeeb <bzeeb-lists at lists.zabbadoz.net 
> >:
>
>> Yeah that is as great as we are or rather were.
>>
>> So really, fix the openvpn scripts that assign the address to
>> interfaces to do something that would make sense from the ``man ip''
>> (not the literal command) point of view.  Just that it's "working"
>> somewhere or used to work elswhere neither means that it was correct
>> nor made sense at any time before.
>
> It's actually in the C code where it was advertised as FreeBSD fix.
> OpenVPN runs in 'topology subnet' mode here, which is documented as  
> follows:
>
> 	Use a subnet rather than a point-to-point topology by
>        configuring the tun interface with a local IP address and  
> subnet
>        mask,  similar  to  the  topology used in --dev tap and  
> ethernet
>        bridging mode.  This mode allocates a single IP address per  
> con-
>        necting  client [... MS-Windows stuff here ...]
>           When used on *nix, requires that the
>        tun driver supports an ifconfig(8) command which sets  a   
> subnet
>        instead of a remote endpoint IP address.
>
> I wonder if TUNSIFMODE (see tun(4)) is somehow needed and if so,  
> already done, and how the proper ifconfig call would look like in  
> this case. Stefan already uttered some ideas in that direction.


Here's a first draft at a patch for OpenVPN.  With this, the tun  
interface gets set to IFF_BROADCAST mode.  One small piece is still  
missing: OpenVPN tries to install a route for the subnet, but that  
fails because now ifconfig has already inserted that route.  I'll try  
to look into that a bit later on.  I also haven't tested the server  
side yet, or any other mode.

root at freebsd-current:/usr/ports/security/openvpn-devel# cat files/ 
patch-tun.c
--- tun.c.orig	2009-05-30 23:34:13.000000000 +0200
+++ tun.c	2009-07-31 14:22:31.000000000 +0200
@@ -863,11 +863,10 @@
        else {
  	if (tt->topology == TOP_SUBNET)
              argv_printf (&argv,
-                              "%s %s %s %s netmask %s mtu %d up",
+                              "%s %s %s netmask %s mtu %d up",
                                IFCONFIG_PATH,
                                actual,
                                ifconfig_local,
-                              ifconfig_local,
                                ifconfig_remote_netmask,
                                tun_mtu
                                );
@@ -1745,14 +1744,15 @@
  {
    open_tun_generic (dev, dev_type, dev_node, ipv6, true, true, tt);

-  if (tt->fd >= 0)
+  if (tt->fd >= 0 && tt->type == DEV_TYPE_TUN)
      {
        int i = 0;

-      /* Disable extended modes */
+      i = tt->topology == TOP_SUBNET ? IFF_BROADCAST : IFF_POINTOPOINT;
+      i |= IFF_MULTICAST;
+      ioctl (tt->fd, TUNSIFMODE, &i);
+      i = 0;
        ioctl (tt->fd, TUNSLMODE, &i);
-      i = 1;
-      ioctl (tt->fd, TUNSIFHEAD, &i);
      }
  }


Stefan

-- 
Stefan Bethke <stb at lassitu.de>   Fon +49 151 14070811