Feature #4532
closedfix writing the various PLMN files
Added by laforge about 4 years ago. Updated about 3 years ago.
100%
Description
- PLMNsel
- PLMNwAcT
- OPLMNwAcT
- HPLMNAcT
However, related updates don't always happen on all cards, as they should.
Files
| mksim_sja2.sh | mksim_sja2.sh | 326 Bytes | dexter, 05/11/2020 11:38 AM | ||
| sysmo_usim_sja2_after_write.txt | sysmo_usim_sja2_after_write.txt | 5.65 KB | dexter, 05/11/2020 11:38 AM | ||
| sysmo_usim_sja2_before_write.txt | sysmo_usim_sja2_before_write.txt | 5.62 KB | dexter, 05/11/2020 11:38 AM | ||
| mobilcom_sim.txt | mobilcom_sim.txt | 4.8 KB | dexter, 05/12/2020 04:57 PM |
Checklist
- verify sysmoISIM-SJA2 fix
- ensure we have a test covering all PLMN files are written correctly
- port fix to WavemobileSIM (if needed, maybe it doesn't haven have that EF?)
Updated by laforge about 4 years ago
- Checklist item verify sysmoISIM-SJA2 fix added
- Checklist item ensure we have a test covering all PLMN files are written correctly added
- Checklist item port fix to WavemobileSIM (if needed, maybe it doesn't haven have that EF?) added
- Subject changed from support writing the various PLMN files to fix writing the various PLMN files
- Assignee set to dexter
- Priority changed from Low to High
Contrary to my original assumption, we actually do have code to write them. This code is used in both SysmoUSIMSJS1 and FairwavesSIM. However, the code is missing from the sysmoISIMSJA2 (and also from WavemobileSIM).
dexter, I created a trivial fix for the sysmoISIMSJA2, see https://gerrit.osmocom.org/c/pysim/+/18051
Please verify this patch, make sure we have test coverage (our tests didn't discover this bug, they should!) and also consider expanding the fix to WavemobileSIM
Updated by dexter almost 4 years ago
- Checklist item verify sysmoISIM-SJA2 fix set to Done
- File mksim_sja2.sh mksim_sja2.sh added
- File sysmo_usim_sja2_after_write.txt sysmo_usim_sja2_after_write.txt added
- File sysmo_usim_sja2_before_write.txt sysmo_usim_sja2_before_write.txt added
- Status changed from New to In Progress
- % Done changed from 0 to 20
I have checked the problem back and from what I can see PLMNsel, PLMNwAcT, OPLMNwAcT, HPLMNAcT are updated. I have attached the output of pySim-Read.py before and after the write. So from what I can see the patch is working fine.
Updated by laforge almost 4 years ago
There are some open questions on the correctness of the encoding of the files (see related sysmocom customer support inquiry)
Updated by dexter almost 4 years ago
The implementation of enc_plmn() in utils.py seems have a problem with padding unused digits correctly.
See 3GPP TS 51.011, 10.3.4 gives an example, lets try encoding it manually and see if the result matches up
246 81 MCC/MNC 246F81 Padd unused digit with 0xF 42F618 Swap nibbles (matches also output of enc_plmn()
And now lets try the PLMN we try to use
262 02 262F02 62F220
When calling enc_plmn() manually with 262 02, we get: 62f22f
I think the way enc_plmn handles leading zeros is wrong.
Updated by dexter almost 4 years ago
- File mobilcom_sim.txt mobilcom_sim.txt added
I had a look at a simcard from a productive network. There the leading zeros of the MNC are also preserved but what confuses me is that the PLMNsel file does not start with 62f210, which would be the home network (262 01).
Here is what what the beginning of my PLMNsel looks like:
32f23012f47022f21002f8100 32f230 => 232f03 => 232 03 12f470 => 214f07 => 214 07
Attached one can find the dump from the simcard I used for this test.
Updated by laforge almost 4 years ago
In case this is not obvious: MNCs come as 2-digit MNC or as 3-digit MNC.
Hence, 262-02 and 262-002 are different networks.
The encoding as per TS 04.08 is implemented in libosmocore for more than a decade and we use it pretty much anywhre on the radio interface, whether in RR or MM or other sub-layers such as BSSMAP. They python code should just simply replicate what the C code is doing.
The encoding of the above two examples should be:- 262-02 -> 62F220
- 262-002 -> 620220
Furthermore, it is not surprising that EF_PLMNsel doesn't list the home operator (derived from the IMSI prefix). In classic 2G SIM cards, the home network is always derived from the IMSI prefix, and it cannot be overridden. Only in USIM, it is possible that the HPLMN MCC/MNC is explicitly set different (e.g. like the EF_HPLMNwAcT
Updated by laforge almost 4 years ago
- treat MNC as a string
- verify that it only contains decimal digits
- pad it to three characters length (if it is 2 only) using a leading F
- then concatenate + nibble-swap with the MCC in enc_plmn()
I hacked this up in https://gerrit.osmocom.org/c/pysim/+/18225 and it seemed to work locally with both 2-digit and 3-digit MNC as well as 1/2/3 digit MCC.
Updated by laforge almost 4 years ago
- % Done changed from 20 to 70
patch has been merged. dexter, please check the two missing checklist items in this ticket and take any action, if required.
Updated by dexter about 3 years ago
- Checklist item ensure we have a test covering all PLMN files are written correctly set to Done
- Checklist item port fix to WavemobileSIM (if needed, maybe it doesn't haven have that EF?) set to Done
Updated by dexter about 3 years ago
- Status changed from Stalled to Resolved
- % Done changed from 70 to 100
I have checked the test data of sysmo-usim-sjs1 and sysmo-isim-sja2, both write PLMNsel, PLMNwAcT, OPLMNwAcT and HPLMNAcT with pySim-prog.py and re-read them with pySim-read.py. The same is true for WavemobileSIM, but it seems not to have HPLMNAcT on the card (we also do not make any write attemts, but pySim-read.py complains). So from what I can see we should be fine as far as this ticket is concerned.
