2 Dec
2012
2 Dec
'12
6:49 a.m.
While running Cell-Log application, I found that the main branch of OsmocomBB gives wrong
value of MCC/MNC in hex (but correct one in decimal), but the Sylvain testing branch gives
correct value.
In practice this means compiling Cell-Log in testing branch gives the name of the country,
but the compiling it in main branch does not recognise the country. Other side-effects are
unknown to me at present.
Tracing through the source leads to the "gsm48_decode_lai" as the culprit. The
code seems correct in the testing branch, but has not been updated in the main. Moreover,
the code is shifted out from gsm48.c to sysinfo.c in the testing branch.
Testing branch decodes MCC/MNC to hex:
*mcc = ((lai->digits[0] & 0x0f) << 8)
| (lai->digits[0] & 0xf0)
| (lai->digits[1] & 0x0f);
But main branch decodes MCC/MNC to decimal:
*mcc = (lai->digits[0] & 0x0f) * 100
+ (lai->digits[0] >> 4) * 10
+ (lai->digits[1] & 0x0f);
The comment in main branch states that "/* Attention: this function retunrs true
integers, not hex! */". There is no such comment in the testing branch.
So is this a problem because Cell_Log wrongly uses gsm48_decode_lai? Or does
gsm48_decode_lai need to be updated in the main branch?
B.
2 Dec
2 Dec
8:57 a.m.
On Sun, Dec 2, 2012 at 7:49 AM, Bhaskar11 <niceguy108(a)gmail.com> wrote:
While running Cell-Log application, I found that the
main branch of
OsmocomBB gives wrong value of MCC/MNC in hex (but correct one in decimal),
but the Sylvain testing branch gives correct value.
Your branches are not up to date ... testing has only two commits
added to it and they have nothing to do with gsm48_decode_lai.
So please update and re-test.
Now when looking at the history of this function, it looks very weird to me :
You find:
----
commit a8ce4ea4696a385d18beb785eef8f510c6fed143
Author: Harald Welte <laforge(a)gnumonks.org>
Date: Sat Sep 8 22:43:50 2012 +0200
layer23: gsm48_decode_lai() is now in libosmogsm
----
followed by:
----
commit 07f83456460a2cdb8d288ac647f04a5bc09dc1cf
Author: Andreas Eversberg <jolly(a)eversberg.eu>
Date: Tue Oct 30 10:26:20 2012 +0100
Fixed decoding of hexadecimal LAI components
libosmocore has changed its LAI decoding from hex to decimal. This caused
wrong decoding of MCC and MNC. In order to provide required hex
transcoding, special hex encoding and decoding function are added to
mobile/sysinfo.c.
----
and in libosmocore:
---
commit 774a9de8b36a53c9e4e4dca4efbb9944cd39ff65
Author: Harald Welte <laforge(a)gnumonks.org>
Date: Fri Jul 13 21:35:13 2012 +0200
import gsm48_decode_lai() function from osmocom-bb/mobile sysinfo.c
commit a9250b9ebcdab7134e5d062e8ca37f9532eca5e8
Author: Harald Welte <laforge(a)gnumonks.org>
Date: Fri Jul 13 22:57:31 2012 +0200
gsm48_decode_lai(): return real integers for mcc/mnc, not hex!
This is to make it orthogonal with gsm48_encode_lai()
---
Now ... this look a little bit like a SNAFU. Now if the goal was to
put common code in libosmocore, that didn't quite endup like that
because now osmocom-bb has a gsm48_decode_lai_hex function that does
the exact same thing as the previous gsm48_decode_lai function and it
doesn't use the libosmocore gsm48_decode_lai function at all. And
having those two different interface looks silly to me ... So which
one is the more practical ?
Cheers,
Sylvain
4 Dec
4 Dec
5:48 p.m.
Sylvain Munaut wrote:
Now ... this look a little bit like a SNAFU.
hi
sylvain,
i don't like having two functions with different results too. the
problem is that osmocom-bb uses hex lai everywhere, and openbsc uses
decimal lai. changing osmocom-bb would result in loosing support for
3-digits-MNC. (02 is not 002 and neither 02x) harald mentioned to maybe
change lai at openbsc in the future, so 3-digits-MNC are correctly
supported there too. then i would suggest to use hex MCC also. also it
would make sense to move the "input" and "print" functions for hex
type
MCC/MNC to libosmocore too.
regards,
andreas
6 Dec
6 Dec
8:14 p.m.
i don't like having two functions with different
results too. the problem is
that osmocom-bb uses hex lai everywhere, and openbsc uses decimal lai.
changing osmocom-bb would result in loosing support for 3-digits-MNC. (02 is
not 002 and neither 02x) harald mentioned to maybe change lai at openbsc in
the future, so 3-digits-MNC are correctly supported there too. then i would
suggest to use hex MCC also. also it would make sense to move the "input"
and "print" functions for hex type MCC/MNC to libosmocore too.
Ok thanks for the explanation, that makes it clear why and this
certainly indicates that the hex version are the "right" way.
Then I'd suggest to put both encode_hex decode_hex version in
libosmocore and put a note deprecating use of the decimal version
since they can't be used to support all mnc/mcc combination like they
should. This way we avoid writing new software against functions that
have these limitations.
Sounds good to everyone ? If no objections, I'll do that.
Cheers,
Sylvain
8:34 p.m.
On Thu, Dec 06, 2012 at 09:14:15PM +0100, Sylvain Munaut wrote:
Then I'd suggest to put both encode_hex decode_hex
version in
libosmocore and put a note deprecating use of the decimal version
since they can't be used to support all mnc/mcc combination like they
should. This way we avoid writing new software against functions that
have these limitations.
agreed.
Sounds good to everyone ? If no objections, I'll
do that.
yes. Will you also check for any users of the decimal version and
convert them to the hex version?
Regards,
Harald
--
- Harald Welte <laforge(a)gnumonks.org> http://laforge.gnumonks.org/
============================================================================
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baseband-devel@lists.osmocom.org
4 comments
4 participants
participants (4)
-
Andreas Eversberg -
Bhaskar11 -
Harald Welte -
Sylvain Munaut