bug in (linux) slattach

bug in (linux) slattach

[jb1]

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If you can't ping ELKS from Linux *AT ALL*, it may be a bug in your Linux
installation rather than in ELKS; slattach 1.21 (1999-11-21), which comes
in net-tools 1.56, doesn't seem to set the serial port speed (at least
under Red Hat 7.0). It seems to be necessary to issue the appropriate stty
command *before* the slattach command. Apparently slattach won't *set* the
speed, but does *lock* it! I've attached a script that seems to work.

There's still a problem in ELKS: it responds to each ping, but with a 
"CHECKSUM ERROR", and telnet, ftp, etc. don't connect.

SOURCE PACKAGES:
        elks-0.1.1.tar.gz, elkscmd_20020501.tar.gz, elksnet-0.1.1.tar.gz,
        Dev86src-0.16.0.tar.gz
CVS PATCHES:
        (none)
COMPILED UNDER:
        Red Hat 7.0 Linux, kernel 2.2.16-22

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# slattach 1.21 (1999-11-21), which comes in net-tools 1.56, doesn't seem 
# to set the serial port speed (at least under Red Hat 7.0). It seems to 
# be necessary to issue the appropriate stty command *before* the slattach 
# command; apparently slattach won't *set* the speed, but does *lock* it!

# Set the serial port speed.
# Some versions of stty apparently require this syntax:
# stty 4800 < /dev/ttyS0
/bin/stty -F /dev/ttyS0 4800

# Enable the serial port.
# The "-s 4800" doesn't seem to do any harm, so I left it in.
/sbin/slattach -p slip -L -m -s 4800 /dev/ttyS0 &

# Wait for slattach to take effect before configuring the interface.
# This seems to be necessary for subsequent commands to take effect.
sleep 1

# Configure the interface.
# This would allow 192.168.2.5 to ping/telnet self as 192.168.1.100:
# /sbin/ifconfig sl0 192.168.1.100 pointopoint 192.168.2.5
/sbin/ifconfig sl0 192.168.2.5 pointopoint 192.168.1.100

# The O'Reilly Linux Network Administrator's Guide example also adds a 
# default route. This doesn't seem to be necessary if just two machines 
# connected.
# /sbin/route add default gw 192.168.1.100

Re: bug in (linux) slattach

[Harry Kalogirou]

Την Πεμ, 26-09-2002 στις 11:49, ο/η jb1@btstream.com έγραψε:
> If you can't ping ELKS from Linux *AT ALL*, it may be a bug in your Linux
> installation rather than in ELKS; slattach 1.21 (1999-11-21), which comes
> in net-tools 1.56, doesn't seem to set the serial port speed (at least
> under Red Hat 7.0). It seems to be necessary to issue the appropriate stty
> command *before* the slattach command. Apparently slattach won't *set* the
> speed, but does *lock* it! I've attached a script that seems to work.
> 
> There's still a problem in ELKS: it responds to each ping, but with a 
> "CHECKSUM ERROR", and telnet, ftp, etc. don't connect.
> 

Hi!
 The "CHECKSUM ERROR" problem is something of a mystery. I stumpled on
it when I tried to connect ELKS to a REDHAT 6.x. The weird thing is that
everything else worked fine... telnet, ftp, http...

 This CHECKSUM ERROR doen't show up on debian machines...


Harry



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Re: bug in (linux) slattach

[Harry Kalogirou]

Την Πεμ, 26-09-2002 στις 11:49, ο/η jb1@btstream.com έγραψε:
> If you can't ping ELKS from Linux *AT ALL*, it may be a bug in your Linux
> installation rather than in ELKS; slattach 1.21 (1999-11-21), which comes
> in net-tools 1.56, doesn't seem to set the serial port speed (at least
> under Red Hat 7.0). It seems to be necessary to issue the appropriate stty
> command *before* the slattach command. Apparently slattach won't *set* the
> speed, but does *lock* it! I've attached a script that seems to work.
> 
> There's still a problem in ELKS: it responds to each ping, but with a 
> "CHECKSUM ERROR", and telnet, ftp, etc. don't connect.
> 

Maybe ELKS is using CSLIP... try 

-p cslip

on slattach...

If that doeen't work... would it be possible to send us a tcpdump of the
slip link?

Harry


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Re: bug in (linux) slattach

[gabucino]

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> installation rather than in ELKS; slattach 1.21 (1999-11-21), which comes
> in net-tools 1.56, doesn't seem to set the serial port speed (at least
I'm using:
net-tools 1.60
@(#) slattach 1.21 (1999-11-21)
net-tools, Fred N. van Kempen et al.

Vanilla net-tools, on my homebrew LFS.
Worked on 4800, and 9600.
Probably another redhat bug you have there.

-- 
Gabucino

/ Worshipping Niedermayer 4ever /
"Do you always look at it encoded?" (C) D. R. F.
"minden lehet. ez nem." (c) A'rpi

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Re: bug in (linux) slattach

[jb1]

On Thu, 26 Sep 2002 gabucino@mplayerhq.hu wrote:

> > installation rather than in ELKS; slattach 1.21 (1999-11-21), which comes
> > in net-tools 1.56, doesn't seem to set the serial port speed (at least
> I'm using:
> net-tools 1.60
> @(#) slattach 1.21 (1999-11-21)
> net-tools, Fred N. van Kempen et al.
> 
> Vanilla net-tools, on my homebrew LFS.
> Worked on 4800, and 9600.
> Probably another redhat bug you have there.

Thank you for letting me know that the same version of slattach works
correctly in a different installation. I upgraded to net-tools-1.60-4
(which also contains ifconfig), and to iputils-20020124-3 (which contains
ping). Now ping works correctly, but slattach ... -s ... still doesn't set
the serial port speed and telnet, etc. still don't work. I guess Red Hat 
hid the bug well.

Re: bug in (linux) slattach

[jb1]

On 15 Oct 2002, Harry Kalogirou wrote:

> I don't seem to get what causes the problem. As much as I can see ELKS
> does the job fine.

I don't get it either. From what you say, ELKS works with everything but
Red Hat; as far as I know, Red Hat works with everything but ELKS. What
you found is *almost* consistent with something I discovered and reported
to the mailing list as "webserver stalls". Essentially, if the
Content-Length is less than 100 bytes then lynx and telnet (and, by the
way, the Linux version of urlget) work fine, otherwise they all stall. 
Maybe we're looking in the wrong place. I assume ELKS serial port works 
properly and I *know* Red Hat's does even for large transfers, but if this 
were a new system I'd suspect something like this: after the first 
100-or-so bytes are received all further incomming bytes are discarded, 
and the current contents of the buffer are are re-read over and over. 
I'll have to check it again, but I think "tcpdump -a" is consistent 
with something like that. Does that suggest anything to you?

> Is there any chance that tcpdump even dumps packets with wrong checksum?

I'm not sure, but I thought I read a *complaint* that tcpdump ignored 
malformed packets. I'll have to look for it again. In light of your 
interpretation, I'll also study these packets in more detail.

When you were counting bytes, did you notice if ELKS sent all 266 bytes of 
the default webpage?

Among the *many* things I had to change to get elkscmd to compile 
correctly was to delete "#include <netdb.h>" from ttn.c because it seemed 
to be both unnecessary and non-existent. I don't see how, but could that 
have anything to do with the problem?

Do you know if anyone has or has not encountered this problem using the 
same versions?
SOURCE PACKAGES:
        elks-0.1.1.tar.gz, elkscmd_20020501.tar.gz, elksnet-0.1.1.tar.gz,
        Dev86src-0.16.0.tar.gz
CVS PATCHES:
        (none)
COMPILED UNDER:
        Red Hat 7.0 Linux, kernel 2.2.16-22