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Tx Loc UPD ACC: Use PLMN provided by subscr

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The MS in general provides the Selected PLMN ID (IE) in the Complete
Layer 3 Information message. osmo-msc handles that message in
msc_a_ran_dec_from_msc_i() and stores the information of the PLMN in
msc_a->via_cell. If no PLMN information is provided in the message, then
at that same place the PLMN configured in the VTY is taken as an implicit
default.

The PLMN information stored in msc_a->via_cell is then finally stored
into vsub->cgi in evaluate_acceptance_outcome().

This patch changes gsm0408_loc_upd_acc() to avoid re-applying the PLMN
configured at the VTY again, and instead use whatever is already in
vsub->cgi. This is more correct since the PLMN provided by the MS takes
precedence over the implicitly configured one, meaning several PLMNs can
be handled. Otherwise, the code is always overwriting the PLMN announced
by the network on a specific RAN with the one in the MSC, which may end
up with unexpected results.

Related: SYS#6360
Change-Id: I421bd63a264db2bf6e1c4a4eea976f389e87b332
This commit is contained in:
Pau Espin Pedrol
2023-07-13 11:33:18 +02:00
parent 1c98031203
commit aecf85705c
1 changed files with 1 additions and 6 deletions
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7
src/libmsc/gsm_04_08.c
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@@ -120,12 +120,7 @@ static int gsm0408_loc_upd_acc(struct msc_a *msc_a, uint32_t send_tmsi)
struct msgb *msg = gsm48_msgb_alloc_name("GSM 04.08 LOC UPD ACC");
struct gsm48_hdr *gh;
struct gsm48_loc_area_id *lai;
struct gsm_network *net = msc_a_net(msc_a);
struct vlr_subscr *vsub = msc_a_vsub(msc_a);
struct osmo_location_area_id laid = {
.plmn = net->plmn,
.lac = vsub->cgi.lai.lac,
};
uint8_t *l;
int rc;
struct osmo_mobile_identity mi = {};
@@ -135,7 +130,7 @@ static int gsm0408_loc_upd_acc(struct msc_a *msc_a, uint32_t send_tmsi)
gh->msg_type = GSM48_MT_MM_LOC_UPD_ACCEPT;
lai = (struct gsm48_loc_area_id *) msgb_put(msg, sizeof(*lai));
gsm48_generate_lai2(lai, &laid);
gsm48_generate_lai2(lai, &vsub->cgi.lai);
if (send_tmsi == GSM_RESERVED_TMSI) {
/* we did not allocate a TMSI to the MS, so we need to