README.NetConsole question

Hello List!

I'm trying to use netconsole on my board but I met unxecpected problems on host side (the machine I'm trying to connect to u-boot'ed board).

I'm trying to use on the host side script from README.NetConsole. The one which is quoted below. When I start the script, my Linux complains about the string "nc -u -l -p 6666".

As the "man nc" states about -l option, "It
is an error to use this option in conjunction with the -p".

Regarding -p: "It is an error to use this option in conjunction with the -l option."

Am I doing something wrong? Should I change nc utility or script?

U-boot version is 1.1.6, host machine uses
Fedora Core 5, nc (netcat utility) is from "nc-1.84-3.2.rpm".

The script from README.NetConsole:

#!/bin/bash -x

[ $# = 1 ] || { echo "Usage: $0 target_ip" >&2 ; exit 1 ; } TARGET_IP=$1

stty -icanon -echo intr ^T
nc -u -l -p 6666 < /dev/null &
nc -u ${TARGET_IP} 6666
stty icanon echo intr ^C

Best regards,
Igor Marnat
mailto:[email protected]

Hi Igor,

Huh! Where exactly does it say so? I cannot even find "error" in the manpage to my nc (1.10-32 on a Debian system). Actually this statement is nonsense, -l tells netcat to "l"isten on a socket and -p tells it the portnumber. How exactly should one start netcat as a listener without combining these options?

Please check the netcat that you have - maybe "nc" simply isn't netcat on your system. Sometimes the binary is called "netcat".

Cheers
Detlev

He thinks he's really smooth, but he's only C^1.
--
DENX Software Engineering GmbH, HRB 165235 Munich, CEO: Wolfgang Denk
Office: Kirchenstr. 5, D-82194 Groebenzell, Germany +49 8142 66989 40

Hi Igor & Detlev,

On my FC5 system, (nc-1.84-3.2) the netcat manpage does make such a statement:

Note that it does not define an option parameter in the manpage documentation for the option ... but the "CLIENT/SERVER MODEL" section of the manpage gives an example:

I'm not sure when or why the option differences started between your two versions of netcat -- but they do apparently exist.

That said, you may want to use the following if your version complains about the -l and -p options being used together:

    $ nc -u -l 6666

Regards,
--Scott

Hi,

Wow, a short research shows that netcat is not a program but a whole family :) Just for the records the Debian netcat seems to be the original implementation by <hobbit AT atstake DOT com>.

Anyway, if the netcat from FedoraCore wins out and -l does not combine with -p anymore, can someone please fix Wikipedia[1]?

Thanks
Detlev

[1] http://en.wikipedia.org/wiki/Netcat

Directories are added, deleted, and rearranged much as you would
expect, even if you don't know it's what you'd expect.
                                         -- Tom Lord in TLA Documentation
--
DENX Software Engineering GmbH, HRB 165235 Munich, CEO: Wolfgang Denk
Office: Kirchenstr. 5, D-82194 Groebenzell, Germany +49 8142 66989 40

I checked the CVS repo at OpenBSD It looks like the -l -p option interaction was pulled in when Eric Jackson's updates for IPv6 support were added in Revision 1.21

http://www.openbsd.org/cgi-bin/cvsweb/src/usr.bin/nc/netcat.c

The commit comments seem humorous (but only in hindsight):

"Import completely re-written netcat w/ support for IPv6. very little usage has changed ...."

That and a hundred other web pages! ;-)

Best Regards,
--Scott

Hello folks,

SM> That and a hundred other web pages! ;-)

Thank you to all guys for the help.

I'd suggest the following patch to begin with. May be native english guys correct me.

diff -urN -X dontdiff u-boot-1.1.6/doc/README.NetConsole u-boot-1.1.6-tz/doc/README.NetConsole
@@ -34,6 +34,11 @@
 stty icanon echo intr ^C
 +++++++++++++++++++++++++++++++++++++++++++
 
+Be aware that in some distributives (Fedora Core 5 at least) usage of
+nc has been changed and -l and -p options are considered as mutually exclusive.
+If nc complains about options provided, try to rebuild it from scratch.
+Known working version lives in nc110.tgz
+
 The script expects exactly one argument, which is interpreted as  the
 target IP address (or host name, assuming DNS is working). The script
 can be interrupted by pressing ^T (CTRL-T).

Best regards,
Igor Marnat
mailto:marny at rambler.ru

Hi Igor

...

Now if you could please submit this as a patch against README.NetConsole ?

Thanks in advance.

Best regards,

Wolfgang Denk

DENX Software Engineering GmbH, HRB 165235 Munich, CEO: Wolfgang Denk
Office:  Kirchenstr. 5,       D-82194 Groebenzell,            Germany
Phone: (+49)-8142-66989-10 Fax: (+49)-8142-66989-80 Email: wd at denx.de
Backed up the system lately?

Hello guys,

WD> Now if you could please submit this as a patch against WD> README.NetConsole ?

Here it goes. I tried, it works.

diff -urN -X dontdiff u-boot-1.1.6/doc/README.NetConsole u-boot-1.1.6-tz/doc/README.NetConsole
@@ -34,6 +34,23 @@
 stty icanon echo intr ^C
 +++++++++++++++++++++++++++++++++++++++++++
 
+Be aware that in some distributives (Fedora Core 5 at least)
+usage of nc has been changed and -l and -p options are considered
+as mutually exclusive. If nc complains about options provided,
+you can remove the -p option from the script. For example:
+
++++++++++++++++++++++++++++++++++++++++++++
+#! /bin/bash
+
+[ $# = 1 ] || { echo "Usage: $0 target_ip" >&2 ; exit 1 ; }
+TARGET_IP=$1
+
+stty -icanon -echo intr ^T
+nc -u -l 6666 < /dev/null &
+nc -u ${TARGET_IP} 6666
+stty icanon echo intr ^C
++++++++++++++++++++++++++++++++++++++++++++
+
 The script expects exactly one argument, which is interpreted as  the
 target IP address (or host name, assuming DNS is working). The script
 can be interrupted by pressing ^T (CTRL-T).

Best regards,
Igor Marnat
mailto:[email protected]

Igor,

On Mon, 2007-03-19 at 09:24 +0300, Igor Marnat wrote:
<snip>

Hello Ben,

BW> I don't think it's necessary to repeat the script in its entirety, since BW> the difference is only two characters. The descriptive paragraph should BW> be enough.

Yes, I think you are right.

BW> Also, please submit with a 'Signed-off-by' line so it gets properly BW> tracked.

I'm not an advanced user of git unfortunately. Anyway, I did my best, hope it's ok now.

---
 doc/README.NetConsole |    5 +++++
 1 files changed, 5 insertions(+), 0 deletions(-)

index cc35a0a..950b0c4 100644
@@ -38,6 +38,11 @@ The script expects exactly one argument, which is interpreted as  the
 target IP address (or host name, assuming DNS is working). The script
 can be interrupted by pressing ^T (CTRL-T).
 
+Be aware that in some distributives (Fedora Core 5 at least)
+usage of nc has been changed and -l and -p options are considered
+as mutually exclusive. If nc complains about options provided,
+you can just remove the -p option from the script. 
+
 It turns out that 'netcat' cannot be used to listen to broadcast
 packets. We developed our own tool 'ncb' (see tools directory) that
 listens to broadcast packets on a given port and dumps them to the

1.4.4.2


Best regards,
Igor Marnat
mailto:marny at rambler.ru

Hello Detlev,

DZ> Please check the netcat that you have - maybe "nc" simply isn't netcat DZ> on your system. Sometimes the binary is called "netcat".

Thank you for your reply, it really helped.

I rebuilt nc from sources (nc110.tgz) and data from the board really appears on my host side as if it was serial console. Obviously distributive of Fedora Core 5 contains some strange version of nc.

Perhaps it worth to mentioned in README.NetConsole.

Best regards,
Igor Marnat
mailto:marny at rambler.ru