for what is the visited_plmn_id of mme_ue context used?

[lezixiao]

Could you please explain your consideration to store last_visited_registered_tai->nas_plmn_id into mme_ue->visited_plmn_id? This mme_ue->visited_plmn_id is also used to derive Kasme in HSS. When the last_visited_registered_tai->nas_plmn_id is different from the current ENB's plmn_id, it will cause UE send security command reject.

emm-handler.c int emm_handle_attach_request(
mme_ue_t *mme_ue, nas_attach_request_t *attach_request)int emm_handle_attach_request(
mme_ue_t *mme_ue, nas_attach_request_t *attach_request)

/* Store UE specific information */
if (attach_request->presencemask &
NAS_ATTACH_REQUEST_LAST_VISITED_REGISTERED_TAI_PRESENT) {
nas_tracking_area_identity_t *last_visited_registered_tai =
&attach_request->last_visited_registered_tai;

    nas_to_plmn_id(&mme_ue->visited_plmn_id,
        &last_visited_registered_tai->nas_plmn_id);
    ogs_debug("    Visited_PLMN_ID:%06x",
            plmn_id_hexdump(&mme_ue->visited_plmn_id));
} else {
    memcpy(&mme_ue->visited_plmn_id, &mme_ue->tai.plmn_id, PLMN_ID_LEN);

}

mme-fd-path.c void mme_s6a_send_air(mme_ue_t *mme_ue,
nas_authentication_failure_parameter_t authentication_failure_parameter)
/ Set the Visited-PLMN-Id AVP */
ret = fd_msg_avp_new(s6a_visited_plmn_id, 0, &avp);
ogs_assert(ret == 0);
val.os.data = nas_from_plmn_id(&nas_plmn_id, &mme_ue->visited_plmn_id);
val.os.len = PLMN_ID_LEN;
ret = fd_msg_avp_setvalue(avp, &val);
ogs_assert(ret == 0);
ret = fd_msg_avp_add(req, MSG_BRW_LAST_CHILD, avp);
ogs_assert(ret == 0);

[acetcom]

I don't remember why I implement it like this. -_-;

HSS should use the Visited PLMN ID. So, I've changed to use tai.plmn_id for deriving KASME.
Please let me know if I have misunderstanding!

Thank you very much!

[lezixiao]

thansk.