SLIP over USBSerial?

[Bill Buzbee]

Hi,
I'm hoping to use a NSLU2 to replace a dedicated x86 Linux box
running Ubuntu 7.10 to serve as a SLIP bridge to my silly homebrew
computer project (http://www.homebrewcpu.com). Because I need
hardware handshaking, I plan on using a USB to Serial converter rather
than the internal serial port.
My NSLU2 arrived in the mail today, and so far I've unslung it
(with 6.10) and installed net tools, busybox and the USBSerial
modules. I also verified the basic operation of the USBSerial
converter (by ssh'ng into the NSLU2 and then using Minicom to log into
my HomebrewCPU machine).
I'm running into a bit of trouble, though, with slattach. On my
Ubuntu box, I can use a USBSerial converter as a SLIP bridge as follows:

slattach -s 38400 -p slip /dev/ttyUSB0 2> /dev/null &
ifconfig sl0 192.168.0.89 pointopoint 192.168.0.76 mtu 576 up
route add -host 192.168.0.76 sl0
arp -Ds 192.168.0.76 eth1 pub
echo 1 > /proc/sys/net/ipv4/ip_forward

However, my first attempt at repeating this sequence on my NSLU2
results in slattach throwing the following error message:

"SLIP_set_disc(1): Invalid argument"

Has anyone out there successfully used an NSLU2 in a similar fashion?
Any other sugggestions?

Thanks much,
...Bill Buzbee
http://www.homebrewcpu.com

[Gregg C Levine]

Hello!
(Hello Bill.)
Whose USB to Serial dongle are you using for the NSLU2 end? Or for that
matter on your Linux box? Some of the devices being sold don't fully enable
the usual serial functions.

For example, one made by Belkin, the F5U109 definitely does not. I believe
the ones from Keyspan do. Certainly according to Parallax the ones made
using the FTDICHIP parts do.

I believe there is a list somewhere on their site.

They are recommended by them for the microcontroller modules the firm
sells.

I should also commend you for your efforts regarding using such a device
with an NSLU2 to act as a connection host for your further efforts and
activities. It's, ah, it's an idea I've long pursued.
--
Gregg C Levine hansolofalcon-XfrvlLN1Pqtfpb/***@public.gmane.org
"The Force will be with you always." Obi-Wan Kenobi
 

-----Original Message-----

Behalf

Of Bill Buzbee
Sent: Monday, December 31, 2007 10:30 PM
Subject: [nslu2-linux] SLIP over USBSerial?
Hi,
I'm hoping to use a NSLU2 to replace a dedicated x86 Linux box
running Ubuntu 7.10 to serve as a SLIP bridge to my silly homebrew
computer project (http://www.homebrewcpu.com). Because I need
hardware handshaking, I plan on using a USB to Serial converter rather
than the internal serial port.
My NSLU2 arrived in the mail today, and so far I've unslung it
(with 6.10) and installed net tools, busybox and the USBSerial
modules. I also verified the basic operation of the USBSerial
converter (by ssh'ng into the NSLU2 and then using Minicom to log into
my HomebrewCPU machine).
I'm running into a bit of trouble, though, with slattach. On my
slattach -s 38400 -p slip /dev/ttyUSB0 2> /dev/null &
ifconfig sl0 192.168.0.89 pointopoint 192.168.0.76 mtu 576 up
route add -host 192.168.0.76 sl0
arp -Ds 192.168.0.76 eth1 pub
echo 1 > /proc/sys/net/ipv4/ip_forward
However, my first attempt at repeating this sequence on my NSLU2
"SLIP_set_disc(1): Invalid argument"
Has anyone out there successfully used an NSLU2 in a similar fashion?
Any other sugggestions?
Thanks much,
...Bill Buzbee
http://www.homebrewcpu.com
Yahoo! Groups Links

[Bill Buzbee]

Post by Gregg C Levine
Whose USB to Serial dongle are you using for the NSLU2 end? Or for that
matter on your Linux box?

I've got several - but the one I'm using right now is a development
kit board with the FTDI chipset. I'm confident that the basic
USB-to-Serial functionality works. I'm currently able to use minicom
on the NSLU2 to connect to my machine over the serial port.

I've done a bit more Googling since my first message, and my current
suspicion is that the unslung kernel wasn't compiled with SLIP support.

Post by Gregg C Levine
I should also commend you for your efforts regarding using such a device
with an NSLU2 to act as a connection host for your further efforts and
activities. It's, ah, it's an idea I've long pursued.

I'm pretty jazzed about getting this working - it looks to be an easy
and cheap way to bridge various of my old serial devices to the net.

[Rod Whitby]

Post by Bill Buzbee

Post by Gregg C Levine
Whose USB to Serial dongle are you using for the NSLU2 end? Or for that
matter on your Linux box?

I've got several - but the one I'm using right now is a development
kit board with the FTDI chipset. I'm confident that the basic
USB-to-Serial functionality works. I'm currently able to use minicom
on the NSLU2 to connect to my machine over the serial port.
I've done a bit more Googling since my first message, and my current
suspicion is that the unslung kernel wasn't compiled with SLIP support.

Unslung:
<http://svn.nslu2-linux.org/svnroot/unslung/releases/unslung-6.10-beta/openembedded/packages/linux/unslung-kernel/defconfig>

# CONFIG_SLIP is not set

SlugOS:
<http://svn.nslu2-linux.org/svnroot/slugos/releases/slugos-4.8-beta/openembedded/packages/linux/linux-ixp4xx/defconfig-2.6.21.7>

# CONFIG_SLIP is not set

(Angstrom uses the same kernel config)

OpenWrt:
<https://svn.openwrt.org/openwrt/tags/kamikaze_7.09/target/linux/ixp4xx-2.6/config/default>

# CONFIG_SLIP is not set

Debian:
<http://svn.debian.org/wsvn/kernel/releases/linux-2.6/2.6.18-5/debian/arch/arm/config.ixp4xx?op=file&rev=0&sc=0>

CONFIG_SLIP=m

Looks like Debian is the distro for you.

-- Rod

[Bill Buzbee]

..snip

Post by Rod Whitby

Post by Bill Buzbee
I've done a bit more Googling since my first message, and my current
suspicion is that the unslung kernel wasn't compiled with SLIP support.

..snip
<http://svn.debian.org/wsvn/kernel/releases/linux-2.6/2.6.18-5/debian/arch/arm/config.ixp4xx?op=file&rev=0&sc=0>

Post by Rod Whitby
CONFIG_SLIP=m
Looks like Debian is the distro for you.
-- Rod

Time for an update:

It's pretty close to working - but not quite there yet. I decided
that Debian was a bit heavyweight for what I had in mind, so I've been
trying with OpenWrt. First step was to rebuild OpenWrt with SLIP
support included, as well as compiling in support for the FTDI-based
USB to Serial converter. That went pretty smoothly, but I then ran
into a problem in which it appeared that the pre-built net-tools
package was compiled with SLIP support disabled.

I also noticed that recent versions of busybox have slattach and
pretty much everything else I need. I really like the idea of running
my slug completely from internal flash, so I decided to use the
busybox slattach. The 1.4 version of busybox didn't include this, so
I backported from 1.7.

The current state of the world is that I can ping my Magic-1 computer
via slip, as well as wget web pages - but only from the NSLU2. I can
arping Magic-1 from elsewhere on my network, and the slug seems to
correctly understand Magic-1's IP address and report its own hardware
address. However, if I do a normal ping to Magic-1 from elsewhere on
the net, I get no response.

I'm profoundly ignorant when it comes to networking magic, so I'd sure
appreciate any advice.

Here's my setup, how I configured the slip link, and the output of
ifconfig, route and arp:

NSLU2 running OpenWrt with custom kernel (built-in SLIP and
USBSerial drivers)
Customized busybox 1.4, with slattach backported from busybox 1.7
FTDI-based USBSerial converter, connected to auxilliary serial port
of my Magic-1 homebrew (running at 38.4K baud)

I set up the slip link as follows (a sequence that has worked
successfully with an X86 Ubuntu 7.10 box):

Note: Slug is 192.168.0.51, Magic-1 is 192.168.0.76

slattach -s 38400 -p slip /dev/ttyUSB0 2> /dev/null &
ifconfig sl0 192.168.0.51 pointopoint 192.168.0.76 mtu 576 up
route add -host 192.168.0.76 sl0
arp -Ds 192.168.0.76 eth0 pub
echo 1 > /proc/sys/net/ipv4/ip_forward

And finally, following is the output of ifconfig, route and arp.
Any suggestions about what additional information would be useful to
track this problem down would be greatly appreciated. It seems pretty
close.

Thanks,
...Bill

---------- output follows:

***@OpenWrt:~# ifconfig
eth0 Link encap:Ethernet HWaddr 00:18:39:AB:19:32
inet addr:192.168.0.51 Bcast:192.168.0.255 Mask:255.255.255.0
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:956 errors:0 dropped:0 overruns:0 frame:0
TX packets:502 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:100
RX bytes:83543 (81.5 KiB) TX bytes:55811 (54.5 KiB)

lo Link encap:Local Loopback
inet addr:127.0.0.1 Mask:255.0.0.0
UP LOOPBACK RUNNING MTU:16436 Metric:1
RX packets:42 errors:0 dropped:0 overruns:0 frame:0
TX packets:42 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:2982 (2.9 KiB) TX bytes:2982 (2.9 KiB)

sl0 Link encap:UNSPEC HWaddr
00-00-00-00-00-00-00-00-00-00-00-00-00-00-00-00
inet addr:192.168.0.51 P-t-P:192.168.0.76 Mask:255.255.255.255
UP POINTOPOINT RUNNING NOARP MULTICAST MTU:576 Metric:1
RX packets:7 errors:0 dropped:0 overruns:0 frame:0
TX packets:8 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:10
RX bytes:815 (815.0 B) TX bytes:549 (549.0 B)

***@OpenWrt:~# route
Kernel IP routing table
Destination Gateway Genmask Flags Metric Ref
Use Iface
192.168.0.76 * 255.255.255.255 UH 0 0
0 sl0
192.168.0.76 * 255.255.255.255 UH 0 0
0 sl0
192.168.0.0 * 255.255.255.0 U 0 0
0 eth0
default 192.168.0.2 0.0.0.0 UG 0 0
0 eth0
***@OpenWrt:~# arp
? (192.168.0.2) at 00:09:5B:EF:02:B8 [ether] on eth0
? (192.168.0.101) at 00:13:02:12:BE:9F [ether] on eth0
? (192.168.0.76) at * PERM PUP on eth0
***@OpenWrt:~#

[Bill Buzbee]

WooHoo! - It's all all working now. On my 4th cup of coffee, I ran
across a posting describing a similar problem:

http://forum.openwrt.org/viewtopic.php?pid=21056

It seems that the default for iptables is to drop forwarded packets. By
doing:

iptables -P FORWARD ACCEPT; iptables -F FORWARD

my little flash-only slug is now working as a SLIP bridge for Magic-1.

Next I'll cobble together a power plug to run the slug off of
Magic-1's power supply. When it's all done, I'll post again with a
recap of getting SLIP over USBSerial working.

Thanks to all!

[Mike (mwester)]

Post by Bill Buzbee
Hi,
I'm hoping to use a NSLU2 to replace a dedicated x86 Linux box
running Ubuntu 7.10 to serve as a SLIP bridge to my silly homebrew
computer project (http://www.homebrewcpu.com). Because I need
hardware handshaking, I plan on using a USB to Serial converter rather
than the internal serial port.
My NSLU2 arrived in the mail today, and so far I've unslung it
(with 6.10) and installed net tools, busybox and the USBSerial
modules. I also verified the basic operation of the USBSerial
converter (by ssh'ng into the NSLU2 and then using Minicom to log into
my HomebrewCPU machine).
I'm running into a bit of trouble, though, with slattach. On my
slattach -s 38400 -p slip /dev/ttyUSB0 2> /dev/null &
ifconfig sl0 192.168.0.89 pointopoint 192.168.0.76 mtu 576 up
route add -host 192.168.0.76 sl0
arp -Ds 192.168.0.76 eth1 pub
echo 1 > /proc/sys/net/ipv4/ip_forward
However, my first attempt at repeating this sequence on my NSLU2
"SLIP_set_disc(1): Invalid argument"
Has anyone out there successfully used an NSLU2 in a similar fashion?
Any other sugggestions?

I'd give SlugOS a try - I'm betting that SlugOS is probably a lot closer to
Ubuntu than is Unslung, especially when it comes to the drivers (the kernel
on Unslung is rather ancient).

Mike (mwester)

[Bill Buzbee]

Post by Mike (mwester)
I'd give SlugOS a try - I'm betting that SlugOS is probably a lot closer to
Ubuntu than is Unslung, especially when it comes to the drivers (the kernel
on Unslung is rather ancient).

Thanks - I'll try that next. My current suspicion is that it isn't a
problem with USBSerial driver support, but rather that the unslung
kernel wasn't compiled with SLIP support. I'm hoping that the stock
SlugOS kernel has SLIP support - otherwise I guess I'll be cobbling
together a build environment.

I'll report back what I discover.

...Bill