[SMF]: Update stored PCO IE requested in GTPv2 over S5c in SMF context

As per 3GPP TS 29.274 version 10.5.0, section 7.2.9 and 7.2.10,
Only if PCO IE is included in Delete Session Request then it
must be present in Delete Session Response.

In order to reflect on whether the request contained PCO IE or not
the SMF context containing the GTP request needs to be updated
i.e. update if present else clear the contents

src/smf/s5c-handler.c

@@ -410,6 +410,23 @@ uint8_t smf_s5c_handle_delete_session_request(
         }
     }
 
+    /* PCO
+     * 3GPP TS 29.274 version 10.5.0, Table 7.2.9.1-1
+     * If the UE includes the PCO IE, then the MME/SGSN shall copy
+     * the content of this IE transparently from the PCO IE included by the UE.
+     * If SGW receives the PCO IE, SGW shall forward it to PGW.
+     */
+    if (req->protocol_configuration_options.presence) {
+        OGS_TLV_STORE_DATA(&sess->gtp.ue_pco,
+                &req->protocol_configuration_options);
+    } else {
+        /* 
+         * Clear contents to reflect whether PCO IE was included or not as part
+         * of session deletion procedure
+         */
+        OGS_TLV_CLEAR_DATA(&sess->gtp.ue_pco);
+    }
+
     ogs_debug("    SGW_S5C_TEID[0x%x] SMF_N4_TEID[0x%x]",
             sess->sgw_s5c_teid, sess->smf_n4_teid);