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ranap: Improve error handling in Rx RESET

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* Verify the CN Indicator is set to PS to avoid reacting on content from
  unexpected peers (eg. IuCS). If none is set, be permissive on rx and
  assume PS.

* If GlobalRNC-ID IE is missing, reject the RESET with an Error
  Indication towards the peer to notify about the rejection.
  Same if we couldn't decode properly it.

* Introduce Tx helpers for generic SCCP UNITDATA.req and RANAP Error
  Indication helpers to simplify code and avoid duplication.

Depends: osmo-iuh.git Change-Id I58c75b3e0e0f33f48d077385ffac820a6b2be59e
Change-Id: I2a53e10c3903992a42d081e3ec300fbdb9b3c34c
This commit is contained in:
Pau Espin Pedrol
2025-08-28 17:40:53 +02:00
parent dfcb514076
commit b9c9271a1f
3 changed files with 68 additions and 5 deletions
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1
TODO-RELEASE
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@@ -12,3 +12,4 @@ libgtp >1.12.0 gtp_set_cb_update_context_ind(), gtp_update_context_resp()
libosmocore >1.10.0 enum gsm48_gprs_ie_mm: GSM48_IE_GMM_UE_NET_CAP, GSM48_IE_GMM_VD_PREF_UE_USAGE
libosmo-gsup-client >1.8.0 osmo_gsup_client_is_connected(), osmo_gsup_client_get_rem_addr(), osmo_gsup_client_get_rem_port()
osmo-iuh >1.7.0 ranap multiple params are constified, see osmo-iuh Change-Id I667dc2ef377c1ceb5b11315458f00b282c143c81
osmo-iuh >1.7.0 ranap_new_msg_error_ind()

7
include/osmocom/sgsn/gprs_ranap.h
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@@ -33,6 +33,13 @@ void sgsn_ranap_iu_tx_release_free(struct ranap_ue_conn_ctx *ctx,
const struct RANAP_Cause *cause,
int timeout);
int sgsn_ranap_iu_tx_cl(struct sgsn_sccp_user_iups *scu_iups,
const struct osmo_sccp_addr *dst_addr,
struct msgb *msg);
int sgsn_ranap_iu_tx_error_ind(struct sgsn_sccp_user_iups *scu_iups,
const struct osmo_sccp_addr *dst_addr,
const RANAP_Cause_t *cause);
int sgsn_ranap_iu_rx_cl_msg(struct sgsn_sccp_user_iups *scu_iups,
const struct osmo_scu_unitdata_param *ud_prim,
const uint8_t *data, size_t len);

65
src/sgsn/gprs_ranap.c
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@@ -329,6 +329,30 @@ int sgsn_ranap_iu_tx(struct msgb *msg_nas, uint8_t sapi)
return sgsn_scu_iups_tx_data_req(uectx->scu_iups, uectx->conn_id, msg);
}
/* Send CL RANAP message over SCCP: */
int sgsn_ranap_iu_tx_cl(struct sgsn_sccp_user_iups *scu_iups,
const struct osmo_sccp_addr *dst_addr,
struct msgb *msg)
{
msg->l2h = msg->data;
return osmo_sccp_tx_unitdata_msg(scu_iups->scu, &scu_iups->local_sccp_addr, dst_addr, msg);
}
/* Send RANAP Error Indication */
int sgsn_ranap_iu_tx_error_ind(struct sgsn_sccp_user_iups *scu_iups,
const struct osmo_sccp_addr *dst_addr,
const RANAP_Cause_t *cause)
{
RANAP_CN_DomainIndicator_t domain = RANAP_CN_DomainIndicator_ps_domain;
struct msgb *ranap_msg;
ranap_msg = ranap_new_msg_error_ind(cause, NULL, &domain, NULL);
if (!ranap_msg)
return -ENOMEM;
return sgsn_ranap_iu_tx_cl(scu_iups, dst_addr, ranap_msg);
}
/* Send Iu Release for the given UE connection.
* If cause is NULL, Normal Release cause is sent, otherwise
* the provided cause. */
@@ -647,19 +671,50 @@ static int ranap_handle_cl_reset_req(struct sgsn_sccp_user_iups *scu_iups,
const RANAP_ResetIEs_t *ies)
{
const RANAP_GlobalRNC_ID_t *grnc_id = NULL;
RANAP_Cause_t cause;
struct osmo_rnc_id rnc_id = {};
struct msgb *resp;
/* FIXME: verify ies.cN_DomainIndicator */
if (ies->presenceMask & ERRORINDICATIONIES_RANAP_CN_DOMAININDICATOR_PRESENT) {
if (ies->cN_DomainIndicator != RANAP_CN_DomainIndicator_ps_domain) {
LOGP(DRANAP, LOGL_ERROR, "Rx RESET: Unexpected CN Domain Indicator %d\n",
(int)ies->cN_DomainIndicator);
cause = (RANAP_Cause_t){
.present = RANAP_Cause_PR_protocol,
.choice.protocol = RANAP_CauseProtocol_semantic_error,
};
return sgsn_ranap_iu_tx_error_ind(scu_iups, &ud_prim->calling_addr, &cause);
}
} /* else: assume PS */
if (ies->presenceMask & RESETIES_RANAP_GLOBALRNC_ID_PRESENT)
grnc_id = &ies->globalRNC_ID;
/* FIXME: support handling Extended RNC-ID instead of Global RNC-ID */
if (!(ies->presenceMask & RESETIES_RANAP_GLOBALRNC_ID_PRESENT)) {
LOGP(DRANAP, LOGL_ERROR,
"Rx RESET: Missing RANAP Global-RNC-ID IE\n");
cause = (RANAP_Cause_t){
.present = RANAP_Cause_PR_protocol,
.choice.protocol = RANAP_CauseProtocol_transfer_syntax_error,
};
return sgsn_ranap_iu_tx_error_ind(scu_iups, &ud_prim->calling_addr, &cause);
}
grnc_id = &ies->globalRNC_ID;
if (iu_grnc_id_parse(&rnc_id, &ies->globalRNC_ID) != 0) {
LOGP(DRANAP, LOGL_ERROR,
"Rx RESET: Failed to parse RANAP Global-RNC-ID IE\n");
cause = (RANAP_Cause_t){
.present = RANAP_Cause_PR_protocol,
.choice.protocol = RANAP_CauseProtocol_transfer_syntax_error,
};
return sgsn_ranap_iu_tx_error_ind(scu_iups, &ud_prim->calling_addr, &cause);
}
/* send reset response */
resp = ranap_new_msg_reset_ack(ies->cN_DomainIndicator, grnc_id);
if (!resp)
return -ENOMEM;
resp->l2h = resp->data;
return osmo_sccp_tx_unitdata_msg(scu_iups->scu, &scu_iups->local_sccp_addr, &ud_prim->calling_addr, resp);
return sgsn_ranap_iu_tx_cl(scu_iups, &ud_prim->calling_addr, resp);
}
static int ranap_handle_cl_err_ind(struct sgsn_sccp_user_iups *scu_iups,