gvpe.osdep(5) os dependent information

DESCRIPTION

This file tries to capture OS-dependent configuration or build issues, quirks and platform limitations, as known.

TUN vs. TAP interface

Most operating systems nowadays support something called a tunnel-device, which makes it possible to divert IPv4 (and often other protocols, too) into a user space daemon like gvpe
. This is being referred to as a TUN-device.

This is fine for point-to-point tunnels, but for a virtual ethernet, an additional ethernet header is needed. This functionality (called a TAP device here) is only provided by a subset of the configurations.

On platforms only supporting a TUN-device, gvpe will invoke it's magical ethernet emulation package, which currently only handles ARP requests for the IPv4 protocol (but more could be added, bu the tincd network drivers might need to be modified for this to work). This means that on those platforms, only IPv4 will be supported.

Also, since there is no way (currently) to tell gvpe which IP subnets are found on a specific host, you will either need to hardwire the MAC address for TUN-style hosts on all networks (and avoid ARP altogether, which is possible), or you need to send a packet from these hosts into the vpn network to tell gvpe the local interface address.

Interface Initialisation

Unless otherwise notes, the network interface will be initialized with the expected MAC address and correct MTU value. With most interface drivers, this is done by running /sbin/ifconfig
, so make sure that this command exists.

Interface Types


native/linux

TAP-device; already part of the kernel (only 2.4+ supported, but see tincd/linux). This is the configuration tested best, as gvpe is being developed on this platform.

ifname
 should be set to the name of the network device.

To hardwire ARP addresses, use iproute2 ( arp
 can do it, too): 

  MAC=fe:fd:80:00:00:$(printf "%02x" $NODEID)
  ip neighbour add 10.11.12.13 lladdr $MAC nud permanent dev $IFNAME

tincd/linux

TAP-device; already part of the kernel (2.2 only). See native/linux
 for more info.

ifname
 should be set to the path of a tap device, e.g. /dev/tap0
. The interface will be named accordingly.

native/cygwin

TAP-device; The TAP device to be used must either be the CIPE driver ( http://cipe-win32.sourceforge.net/
), or (highly recommended) the newer TAP-Win32 driver bundled with openvpn (http://openvpn.sf.net/). Just download and run the openvpn installer. The only option you need to select is the TAP driver.

ifname
 should be set to the name of the device, found in the registry at (no kidding :): 

      HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Network\{4D36E972-E325-11CE-BFC1-08002BE10318}\<adapterid>\Connection\Name

The MAC address is dynamically being patched into packets and ARP-requests, so only IPv4 works with ARP on this platform.

tincd/bsd

TAP-device, maybe; migth work for many bsd variants.

This driver is a newer version of the tincd/*bsd
 drivers. It might provide a TAP device, or might not work at all. You might try this interface type first, and, if it doesn't work, try one of the OS-specific drivers.

tincd/freebsd

TAP-device; part of the kernel (since 4.x, maybe earlier).

ifname
 should be set to the path of a tap device, e.g. /dev/tap0
. The interface will be named accordingly.

These commands might be helpful examples: 

  ifconfig $IFNAME 10.0.0.$NODEID
  route add -net 10.0.0.0 -netmask 255.255.255.0 -interface $IFNAME 10.0.0.$NODEID

tincd/netbsd

TUN-device; The interface is a point-to-point device. To initialize it, you currently need to configure it as a point-to-point device, giving it an address on your vpn (the exact address doesn't matter), like this: 

  ifconfig $IFNAME mtu $MTU up
  ifconfig $IFNAME 10.11.12.13 10.55.66.77
  route add -net 10.0.0.0 10.55.66.77 255.0.0.0
  ping -c1 10.55.66.77 # ping once to tell gvpe your gw ip

The ping is required to tell the ARP emulator inside GVPE the local IP address.

ifname
 should be set to the path of a tun device, e.g. /dev/tun0
. The interface will be named accordingly.

tincd/openbsd

TUN-device; already part of the kernel. See tincd/netbsd
 for more information.

native/darwin

TAP-device;

The necessary kernel extension can be found here: 


  http://www-user.rhrk.uni-kl.de/~nissler/tuntap/

There are two drivers, the one to use is the ``tap'' driver. It driver must be loaded before use, read the docs on how to install it as a startup item.

ifname
 should be set to the path of a tap device, e.g. /dev/tap0
. The interface will be named accordingly.

These commands might be helpful examples: 

  ifconfig $IFNAME 10.0.0.$NODEID
  route add -net 10.0.0.0 -interface $IFNAME 255.255.255.0

tincd/darwin

TUN-device; See tincd/netbsd
 for more information. native/darwin
 is preferable.

The necessary kernel extension can be found here: 


  http://chrisp.de/en/projects/tunnel.html

ifname
 should be set to the path of a tun device, e.g. /dev/tun0
. The interface will be named accordingly.

The driver must be loaded before use: 

  kmodload tunnel

tincd/solaris

TUN-device; already part of the kernel(?), or available here: 


  http://vtun.sourceforge.net/tun/

Some precompiled tun drivers might be available here: 


  http://www.monkey.org/~dugsong/fragroute/

The interface MAC and MTU are NOT set up for you. Please try it out and send me an ifconfig
 command invocation that does that.

See tincd/netbsd
 for more information.

Completely untested so far.

tincd/mingw

TAP-device; see native/cygwin
 for more information.

The setup is likely to be similar to native/cygwin
.

Completely untested so far.

tincd/raw_socket

TAP-device; purpose unknown and untested, probably binds itself on an existing ethernet device (given by ifname
). It must be down prior to running the command, and GVPE will try to set it's MAC address and MTU to the ``correct'' values.

Completely untested so far.

tincd/uml_socket

TAP-device; purpose unknown and untested, probably creates a UNIX datagram socket (path given by ifname
) and reads and writes raw packets, so might be useful in other than UML contexts.

No network interface is created, and the MAC and MTU must be set as appropriate on the other side of the socket. GVPE will exit if the MAC address doesn't match what it expects.

Completely untested so far.

tincd/cygwin

Known to be broken, use native/cygwin
 instead.

AUTHOR

Marc Lehmann <[email protected]>

SEE ALSO

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