[PATCH] Documentation, clarify tuntap IPX example.

[PATCH] Documentation, clarify tuntap IPX example.

[andrew hendry]

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.

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.

Re: [PATCH] Documentation, clarify tuntap IPX example.

[Max Krasnyansky]

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.

Re: [PATCH] Documentation, clarify tuntap IPX example.

[andrew hendry]

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.
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?

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.
>
>

Re: [PATCH] Documentation, clarify tuntap IPX example.

[Max Krasnyansky]

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.
>>

Re: [PATCH] Documentation, clarify tuntap IPX example.

[andrew hendry]

Hi Max,

Thanks. TUNSETLINK looks like exactly what I need.
I'll have to have a closer look at kernel x.25 next, i don't think it
likes the tunx25 going away with routes still too it.

deb32:~# cat /proc/net/x25/route
Address          Digits  Device
000000000000000  0       @�\x18��
                              \x18�@�\x1d

[  662.425648] BUG: unable to handle kernel NULL pointer dereference at 00000017
[  662.426291] IP: [<c10b5908>] dup_fd+0x21f/0x2fa
[  662.427849] *pde = 00000000
[  662.428028] Oops: 0002 [#1] SMP
[  662.428028] last sysfs file: /sys/class/net/lo/operstate
[  662.428028] Modules linked in: x25 tun ipv6 loop ac button
parport_pc parport snd_pcm snd_timer serio_raw psmouse snd soundcore
snd_page_alloc pcspkr i2c_piix4 i2c_core evdev ext3 jbd mbcache
ide_cd_mod cdrom ide_gd_mod ata_generic ata_piix libata scsi_mod
ide_pci_generic piix floppy pcnet32 mii ide_core thermal fan
thermal_sys [last unloaded: tun]
[  662.428028]
[  662.428028] Pid: 12252, comm: net.agent Not tainted (2.6.31.6 #1) VirtualBox
[  662.428028] EIP: 0060:[<c10b5908>] EFLAGS: 00010286 CPU: 0
[  662.428028] EIP is at dup_fd+0x21f/0x2fa
[  662.428028] EAX: 00000017 EBX: ce5262a0 ECX: 00000220 EDX: ffffffff
[  662.428028] ESI: 00000088 EDI: ce41e400 EBP: 00000100 ESP: c2849eec
[  662.428028]  DS: 007b ES: 007b FS: 00d8 GS: 0033 SS: 0069
[  662.428028] Process net.agent (pid: 12252, ti=c2848000
task=ce9d51c0 task.ti=c2848000)
[  662.428028] Stack:
[  662.428028]  00000202 00000020 00000008 cf466cc0 cf466cc4 cf4667c0
ce41e400 00000078
[  662.428028] <0> ce5262c0 cf466d00 cf4667c8 ce02bc00 ce18db60
00000000 00000000 ce9d51c0
[  662.428028] <0> c102d03b 080a8120 cf649668 c2849fb4 bfe05a6c
01200011 ce18dca4 fffffff4
[  662.428028] Call Trace:
[  662.428028]  [<c102d03b>] ? copy_process+0x469/0xf96
[  662.428028]  [<c102dc7d>] ? do_fork+0x115/0x282
[  662.428028]  [<c10a4965>] ? vfs_llseek+0x30/0x34
[  662.428028]  [<c1001d8e>] ? sys_clone+0x21/0x27
[  662.428028]  [<c10030c9>] ? syscall_call+0x7/0xb
[  662.428028] Code: 4c 24 08 8b 70 08 f3 a5 8b 4c 24 04 83 e1 03 74
02 f3 a4 31 c9 31 f6 89 6c 24 1c eb 29 8b 7c 24 18 8b 14 0f 85 d2 74
09 8d 42 18 <3e> ff 42 18 eb 06 8b 43 0c 0f b3 30 8b 44 24 2c 46 89 14
08 83
[  662.428028] EIP: [<c10b5908>] dup_fd+0x21f/0x2fa SS:ESP 0069:c2849eec
[  662.428028] CR2: 0000000000000017
[  662.452941] ---[ end trace aab1610cb3ca8b89 ]---

Message from syslogd@deb32 at Nov 19 06:58:56 ...
 kernel:[  904.324109] unregister_netdevice: waiting for xotdtun to
become free. Usage count = -3


Andrew

On Wed, Nov 18, 2009 at 4:52 PM, Max Krasnyansky <maxk@qualcomm.com> wrote:
> 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.
>>>
>
>