ranap: Reject ActivatePDPCtx from UE if RABAssResp parsing fails

Before this patch, if Rx path at RAB Ass Req failed, the PDP ctx in the
middle of being activated was left untouched.
Explicitly communicate the failure to both sides (UE and GGSN).

Related: OS#6508
Related: SYS#7119
Change-Id: I111cc4b17100d2e1ef756b654dc9e98415b3a8bb

src/sgsn/gprs_ranap.c

@@ -68,6 +68,7 @@ static int sgsn_ranap_rab_ass_resp(struct sgsn_mm_ctx *ctx, RANAP_RAB_SetupOrMod
 	pdp = sgsn_pdp_ctx_by_nsapi(ctx, rab_id);
 	if (!pdp) {
 		LOGP(DRANAP, LOGL_ERROR, "RAB Assignment Response for unknown RAB/NSAPI=%u\n", rab_id);
+		sgsn_ranap_iu_release_free(ctx, NULL);
 		return -1;
 	}
 
@@ -81,7 +82,7 @@ static int sgsn_ranap_rab_ass_resp(struct sgsn_mm_ctx *ctx, RANAP_RAB_SetupOrMod
 			     "RAB Assignment Resp: Unknown Transport Layer Address (size %u): %s\n",
 			     item->transportLayerAddress->size,
 			     osmo_hexdump(item->transportLayerAddress->buf, item->transportLayerAddress->size));
-			return -1;
+			goto ret_error;
 		}
 
 		switch (addr.u.sa.sa_family) {
@@ -92,12 +93,12 @@ static int sgsn_ranap_rab_ass_resp(struct sgsn_mm_ctx *ctx, RANAP_RAB_SetupOrMod
 			/* TODO: Support IPv6 address */
 			LOGP(DRANAP, LOGL_ERROR,
 			     "RAB Assignment Resp: IPv6 transport layer address not supported!\n");
-			return -1;
+			goto ret_error;
 		default:
 			LOGP(DRANAP, LOGL_ERROR,
 			     "RAB Assignment Resp: Unexpected transport layer address size %u\n",
 			     item->transportLayerAddress->size);
-			return -1;
+			goto ret_error;
 		}
 		require_pdp_update = true;
 	}
@@ -125,6 +126,15 @@ static int sgsn_ranap_rab_ass_resp(struct sgsn_mm_ctx *ctx, RANAP_RAB_SetupOrMod
 	}
 	return 0;
 
+ret_error:
+	if (pdp->state != PDP_STATE_CR_CONF) {
+		gsm48_tx_gsm_act_pdp_rej(ctx, pdp->ti, GSM_CAUSE_NET_FAIL,
+					 0, NULL);
+		sgsn_delete_pdp_ctx(pdp);
+	} else {
+		gsm48_tx_gsm_deact_pdp_req(pdp, GSM_CAUSE_NET_FAIL, true);
+	}
+	return -1;
 }
 
 int sgsn_ranap_iu_event(struct ranap_ue_conn_ctx *ctx, enum ranap_iu_event_type type, void *data)