fixeria has uploaded this change for review. ( https://gerrit.osmocom.org/c/osmo-ttcn3-hacks/+/31241 )

Change subject: library/GSM_Types: fix encoding of BcdMccMnc (3 octets) ......................................................................

library/GSM_Types: fix encoding of BcdMccMnc (3 octets)

In [1] I copied the hexstring concatenation statement for the 3-digit MNC from the original function f_enc_BcdMccMnc(), which was renamed to f_enc_BcdMccMnc_int(). Unfortunately, this statement (originally introduced in commit [2]) is incorrect.

In our implementation a pair of MCC and MNC is encoded as follows:

| MCC digit 1 | MCC digit 2 | octet 1 | MNC digit 3 | MCC digit 3 | octet 2 | MNC digit 1 | MNC digit 2 | octet 3

Additionally, in the case of a 2-digit MNC, the original variant of f_enc_BcdMccMnc() (before [1]) would swap MCC and MCC in the 2nd octet, generating even more unpredictable results.

According to 3GPP TS 24.008, Figure 10.5.13, the correct coding is:

| MCC digit 2 | MCC digit 1 | octet 1 | MNC digit 3 | MCC digit 3 | octet 2 | MNC digit 2 | MNC digit 1 | octet 3

So far the only user of this API is the PCU_Tests module. Looking at the PCAPs of testcases invoking this function, Wireshark indeed shows weird MCC/MNC values (expected 262/42):

Routing area identification: 23-43-423-2 Mobile Country Code (MCC): Unknown (23) Mobile Network Code (MNC): Unknown (43) Location Area Code (LAC): 0x01a7 (423) Routing Area Code (RAC): 0x02 (2)

Change-Id: Ifa3083fdd6307b56baa1ef3ac85a3e7a2efab728 Related: [1] 7a92d5fbc008ba7c3085fe1b524424a32da3a49f Fixes: [2] 0637ba072820a370ed539ab0e23f8ded8bce6d16 --- M library/GSM_Types.ttcn 1 file changed, 5 insertions(+), 1 deletion(-)

git pull ssh://gerrit.osmocom.org:29418/osmo-ttcn3-hacks refs/changes/41/31241/1

diff --git a/library/GSM_Types.ttcn b/library/GSM_Types.ttcn index 07da576..134edbd 100644 --- a/library/GSM_Types.ttcn +++ b/library/GSM_Types.ttcn @@ -440,7 +440,11 @@ if (lengthof(mnc) == 2) { mnc := mnc[0] & mnc[1] & 'F'H; } - return mcc[0] & mcc[1] & mnc[2] & mcc[2] & mnc[0] & mnc[1]; + /* 3GPP TS 24.008, Figure 10.5.13 + * | MCC digit 2 | MCC digit 1 | octet 1 + * | MNC digit 3 | MCC digit 3 | octet 2 + * | MNC digit 2 | MNC digit 1 | octet 3 */ + return mcc[1] & mcc[0] & mnc[2] & mcc[2] & mnc[1] & mnc[0]; }

/* Compute BcdMccMnc from integer values */