Messages in this thread | | | Date | Tue, 17 Nov 2009 21:52:55 -0800 | From | Max Krasnyansky <> | Subject | Re: [PATCH] Documentation, clarify tuntap IPX example. |
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andrew hendry wrote: > Hi Max, > > I started looking through the documentation because im looking to use > tun for X.25 over TCP. The IPX example sounded similar but i couldn't > get it to work as I was expecting. Looking for a hint in the right > direction. Ah, X25 is different.
> There is an old non-mainline patch called x25tap (clone of obsolete > ethertap). I'm hoping to replace x25tap with tun. > > The old x25tap creates a device like: > x25tap0 Link encap:generic X.25 HWaddr > UP BROADCAST RUNNING NOARP MULTICAST MTU:1024 Metric:1 > RX packets:3040785 errors:0 dropped:0 overruns:0 frame:0 > TX packets:2895530 errors:0 dropped:0 overruns:0 carrier:0 > collisions:0 txqueuelen:10 > RX bytes:138787339 (132.3 Mb) TX bytes:91395983 (87.1 Mb) > When the x25tap is loaded it has dev->type = ARPHRD_X25, after which > x.25 routing and AF_X25 sockets can be created. Along with an XoT > userspace program which handles some basic headers and TCP port 1998 > it works well. > > If using tun, how does something get registered to handle protocol AF_X25? >
I've never tried this personally so ... :). But I just glanced over net/ax25 and drivers/wan/ax25 and it looks TUNSETLINK might work for you. In other words you want to allocate TUN device (not TAP) and then call TUNSETLINK with ARPHRD_X25. Seems like you'll get exactly what you need.
Max
> Regards, > Andrew. > > On Wed, Nov 18, 2009 at 12:40 PM, Max Krasnyansky <maxk@qualcomm.com> wrote: >> On 11/17/2009 05:30 PM, andrew hendry wrote: >>> Can the TUNSETIFF ioctl change a tap's protocol to IPX as the >>> documentation suggests? >>> I think tun.c would need IFF_IPX_TAP added for it to work as described? >>> Otherwise tap can only be ptp or ethernet, and there is no way to >>> route or use AF_IPX. >> TAP is an Ethernet device. No special handling is required for IPX or for >> that matter any other protocol. Example seems fine too. >> >> Max >> >>> Signed-off-by: Andrew Hendry<andrew.hendry@gmail.com> >>> >>> --- a/Documentation/networking/tuntap.txt 2009-11-11 >>> 14:03:22.676167648 +1100 >>> +++ b/Documentation/networking/tuntap.txt 2009-11-18 >>> 11:34:18.106647029 +1100 >>> @@ -127,12 +127,14 @@ Ethernet device, which instead of receiv >>> media, receives them from user space program and instead of sending >>> packets via physical media sends them to the user space program. >>> >>> -Let's say that you configured IPX on the tap0, then whenever >>> -the kernel sends an IPX packet to tap0, it is passed to the application >>> -(VTun for example). The application encrypts, compresses and sends it to >>> -the other side over TCP or UDP. The application on the other side >>> decompresses >>> -and decrypts the data received and writes the packet to the TAP device, >>> -the kernel handles the packet like it came from real physical device. >>> +Let's say for the purpose of example, IPX support was added to tuntap. >>> +Then whenever the kernel routes an IPX packet to tap0, it is passed to >>> the >>> +application reading the file descriptor from /dev/net/tun (VTun for >>> example). >>> +The application encrypts, compresses and sends it to the other side over >>> TCP >>> +or UDP. The application on the other side decompresses and decrypts the >>> data >>> +received and writes the packet to the TAP device, the remote kernel >>> handles >>> +the packet like it came from real physical device. The IPX applications >>> are >>> +able to communicate as if there was a real IPX network. >>> >>> 4. What is the difference between TUN driver and TAP driver? >>> TUN works with IP frames. TAP works with Ethernet frames. >>
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