[ePDG] Add Node-Identifier IE support in GTPv2 S2b Create-Session-Request for SMF Diameter S6b Routing (#3507)

Implement support for Node-Identifier IE in GTPv2 S2b Create-Session-Request
to SMF for Diameter S6b integration

This patch adds support for processing the Node-Identifier IE within GTPv2
Create-Session-Request messages sent via the S2b interface to the SMF.
When the ePDG includes the Node-Identifier IE containing both host and realm
of the AAA-Server, the SMF now uses this information to populate
the Destination-Realm and Destination-Host AVPs in the Diameter S6b AAR message.

This enables seamless integration and allows the SMF to route requests directly
to the appropriate AAA-Server, enhancing interoperability in setups
where the host and realm data are required by the Diameter network.

lib/gtp/v2/types.c

@@ -26,13 +26,15 @@
 int16_t ogs_gtp2_parse_bearer_qos(
     ogs_gtp2_bearer_qos_t *bearer_qos, ogs_tlv_octet_t *octet)
 {
-    ogs_gtp2_bearer_qos_t *source = (ogs_gtp2_bearer_qos_t *)octet->data;
+    ogs_gtp2_bearer_qos_t *source = NULL;
     int16_t size = 0;
 
     ogs_assert(bearer_qos);
     ogs_assert(octet);
     ogs_assert(octet->len == GTP2_BEARER_QOS_LEN);
 
+    source = (ogs_gtp2_bearer_qos_t *)octet->data;
+
     memset(bearer_qos, 0, sizeof(ogs_gtp2_bearer_qos_t));
 
     bearer_qos->pre_emption_capability = source->pre_emption_capability;
@@ -201,13 +203,15 @@ uint64_t ogs_gtp2_qos_to_kbps(uint8_t br, uint8_t extended, uint8_t extended2)
 int16_t ogs_gtp2_parse_flow_qos(
     ogs_gtp2_flow_qos_t *flow_qos, ogs_tlv_octet_t *octet)
 {
-    ogs_gtp2_flow_qos_t *source = (ogs_gtp2_flow_qos_t *)octet->data;
+    ogs_gtp2_flow_qos_t *source = NULL;
     int16_t size = 0;
 
     ogs_assert(flow_qos);
     ogs_assert(octet);
     ogs_assert(octet->len == GTP2_FLOW_QOS_LEN);
 
+    source = (ogs_gtp2_flow_qos_t *)octet->data;
+
     memset(flow_qos, 0, sizeof(ogs_gtp2_flow_qos_t));
 
     flow_qos->qci = source->qci;
@@ -617,12 +621,14 @@ int16_t ogs_gtp2_build_tft(
 /* 8.21 User Location Information (ULI) */
 int16_t ogs_gtp2_parse_uli(ogs_gtp2_uli_t *uli, ogs_tlv_octet_t *octet)
 {
-    ogs_gtp2_uli_t *source = (ogs_gtp2_uli_t *)octet->data;
+    ogs_gtp2_uli_t *source = NULL;
     int16_t size = 0;
 
     ogs_assert(uli);
     ogs_assert(octet);
 
+    source = (ogs_gtp2_uli_t *)octet->data;
+
     memset(uli, 0, sizeof(ogs_gtp2_uli_t));
 
     uli->flags = source->flags;
@@ -796,3 +802,95 @@ int16_t ogs_gtp2_build_uli(
 
     return octet->len;
 }
+
+int16_t ogs_gtp2_parse_node_identifier(
+    ogs_gtp2_node_identifier_t *node_identifier, ogs_tlv_octet_t *octet)
+{
+    int16_t size = 0;
+
+    ogs_assert(node_identifier);
+    ogs_assert(octet);
+
+    memset(node_identifier, 0, sizeof(ogs_gtp2_node_identifier_t));
+
+    if (size + sizeof(node_identifier->name_len) > octet->len) {
+        ogs_error("Invalid TLV length [%d != %d]", size, octet->len);
+        ogs_log_hexdump(OGS_LOG_ERROR, octet->data, octet->len);
+        return size;
+    }
+    memcpy(&node_identifier->name_len,
+            (unsigned char *)octet->data + size,
+            sizeof(node_identifier->name_len));
+    size += sizeof(node_identifier->name_len);
+
+    if (size + node_identifier->name_len > octet->len) {
+        ogs_error("Invalid TLV length [%d != %d]", size, octet->len);
+        ogs_log_hexdump(OGS_LOG_ERROR, octet->data, octet->len);
+        return size;
+    }
+    node_identifier->name = (char *)octet->data + size;
+    size += node_identifier->name_len;
+
+    if (size + sizeof(node_identifier->realm_len) > octet->len) {
+        ogs_error("Invalid TLV length [%d != %d]", size, octet->len);
+        ogs_log_hexdump(OGS_LOG_ERROR, octet->data, octet->len);
+        return size;
+    }
+    memcpy(&node_identifier->realm_len,
+            (unsigned char *)octet->data + size,
+            sizeof(node_identifier->realm_len));
+    size += sizeof(node_identifier->realm_len);
+
+    if (size + node_identifier->realm_len > octet->len) {
+        ogs_error("Invalid TLV length [%d != %d]", size, octet->len);
+        ogs_log_hexdump(OGS_LOG_ERROR, octet->data, octet->len);
+        return size;
+    }
+    node_identifier->realm = (char *)octet->data + size;
+    size += node_identifier->realm_len;
+
+    if (size != octet->len) {
+        ogs_error("Invalid TLV length [%d != %d]", size, octet->len);
+        ogs_log_hexdump(OGS_LOG_ERROR, octet->data, octet->len);
+    }
+
+    return size;
+}
+int16_t ogs_gtp2_build_node_identifier(ogs_tlv_octet_t *octet,
+    ogs_gtp2_node_identifier_t *node_identifier, void *data, int data_len)
+{
+    int16_t size = 0;
+
+    ogs_assert(node_identifier);
+    ogs_assert(octet);
+    ogs_assert(data);
+    ogs_assert(data_len);
+
+    octet->data = data;
+
+    ogs_assert(size + sizeof(node_identifier->name_len) <= data_len);
+    memcpy((unsigned char *)octet->data + size,
+            &node_identifier->name_len,
+            sizeof(node_identifier->name_len));
+    size += sizeof(node_identifier->name_len);
+
+    ogs_assert(size + node_identifier->name_len <= data_len);
+    memcpy((unsigned char *)octet->data + size,
+            node_identifier->name, node_identifier->name_len);
+    size += node_identifier->name_len;
+
+    ogs_assert(size + sizeof(node_identifier->realm_len) <= data_len);
+    memcpy((unsigned char *)octet->data + size,
+            &node_identifier->realm_len,
+            sizeof(node_identifier->realm_len));
+    size += sizeof(node_identifier->realm_len);
+
+    ogs_assert(size + node_identifier->realm_len <= data_len);
+    memcpy((unsigned char *)octet->data + size,
+            node_identifier->realm, node_identifier->realm_len);
+    size += node_identifier->realm_len;
+
+    octet->len = size;
+
+    return octet->len;
+}

lib/gtp/v2/types.h

@@ -571,6 +571,20 @@ ED5(uint8_t spare1:1;,
     uint8_t pre_emption_capability:1;)
 } __attribute__ ((packed)) ogs_gtp2_arp_t;
 
+/* 8.107 Node Identifier */
+#define OGS_GTP2_MAX_NODE_IDENTIFIER_LEN (1+OGS_MAX_FQDN_LEN)*2
+typedef struct ogs_gtp2_node_identifier_s {
+    uint8_t name_len;
+    char *name;
+    uint8_t realm_len;
+    char *realm;
+} ogs_gtp2_node_identifier_t;
+
+int16_t ogs_gtp2_parse_node_identifier(
+    ogs_gtp2_node_identifier_t *node_identifier, ogs_tlv_octet_t *octet);
+int16_t ogs_gtp2_build_node_identifier(ogs_tlv_octet_t *octet,
+    ogs_gtp2_node_identifier_t *node_identifier, void *data, int data_len);
+
 #ifdef __cplusplus
 }
 #endif

src/smf/context.c

@@ -1791,6 +1791,11 @@ void smf_sess_remove(smf_sess_t *sess)
     /* Free SBI object memory */
     ogs_sbi_object_free(&sess->sbi);
 
+    if (sess->aaa_server_identifier.name)
+        ogs_free(sess->aaa_server_identifier.name);
+    if (sess->aaa_server_identifier.realm)
+        ogs_free(sess->aaa_server_identifier.realm);
+
     smf_bearer_remove_all(sess);
 
     ogs_assert(sess->pfcp.bar);

src/smf/context.h

@@ -486,6 +486,12 @@ typedef struct smf_sess_s {
         uint32_t id;
     } charging;
 
+    /* AAA Node Identifier */
+    struct {
+        char *name;
+        char *realm;
+    } aaa_server_identifier;
+
     /* Data Forwarding between the CP and UP functions */
     ogs_pfcp_pdr_t  *cp2up_pdr;
     ogs_pfcp_pdr_t  *up2cp_pdr;

src/smf/s5c-handler.c

@@ -445,6 +445,34 @@ uint8_t smf_s5c_handle_create_session_request(
             smf_ue->imeisv, smf_ue->imeisv_len, smf_ue->imeisv_bcd);
     }
 
+    /* Set Node Identifier */
+    if (req->_aaa_server_identifier.presence) {
+        ogs_gtp2_node_identifier_t node_identifier;
+        decoded = ogs_gtp2_parse_node_identifier(
+                &node_identifier, &req->_aaa_server_identifier);
+        if (req->_aaa_server_identifier.len == decoded) {
+            if (sess->aaa_server_identifier.name)
+                ogs_free(sess->aaa_server_identifier.name);
+            sess->aaa_server_identifier.name = ogs_memdup(
+                node_identifier.name, node_identifier.name_len+1);
+            ogs_assert(sess->aaa_server_identifier.name);
+            sess->aaa_server_identifier.name[node_identifier.name_len] = 0;
+
+            if (sess->aaa_server_identifier.realm)
+                ogs_free(sess->aaa_server_identifier.realm);
+            sess->aaa_server_identifier.realm = ogs_memdup(
+                node_identifier.realm, node_identifier.realm_len+1);
+            ogs_assert(sess->aaa_server_identifier.realm);
+            sess->aaa_server_identifier.realm[node_identifier.realm_len] = 0;
+        } else {
+            ogs_error("Invalid AAA Server Identifier [%d != %d]",
+                    req->_aaa_server_identifier.len, decoded);
+            ogs_log_hexdump(OGS_LOG_ERROR,
+                    req->_aaa_server_identifier.data,
+                    req->_aaa_server_identifier.len);
+        }
+    }
+
     return OGS_GTP2_CAUSE_REQUEST_ACCEPTED;
 }
 

src/smf/s6b-path.c

@@ -176,11 +176,28 @@ void smf_s6b_send_aar(smf_sess_t *sess, ogs_gtp_xact_t *xact)
     ret = fd_msg_add_origin(req, 0);
     ogs_assert(ret == 0);
 
+    /* Set the Destination-Host AVP */
+    if (sess->aaa_server_identifier.name) {
+        ret = fd_msg_avp_new(ogs_diam_destination_host, 0, &avp);
+        ogs_assert(ret == 0);
+        val.os.data = (unsigned char *)sess->aaa_server_identifier.name;
+        val.os.len  = strlen(sess->aaa_server_identifier.name);
+        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);
+    }
+
     /* Set the Destination-Realm AVP */
     ret = fd_msg_avp_new(ogs_diam_destination_realm, 0, &avp);
     ogs_assert(ret == 0);
-    val.os.data = (unsigned char *)(fd_g_config->cnf_diamrlm);
+    if (sess->aaa_server_identifier.realm) {
-    val.os.len  = strlen(fd_g_config->cnf_diamrlm);
+        val.os.data = (unsigned char *)(sess->aaa_server_identifier.realm);
+        val.os.len  = strlen(sess->aaa_server_identifier.realm);
+    } else {
+        val.os.data = (unsigned char *)(fd_g_config->cnf_diamrlm);
+        val.os.len  = strlen(fd_g_config->cnf_diamrlm);
+    }
     ret = fd_msg_avp_setvalue(avp, &val);
     ogs_assert(ret == 0);
     ret = fd_msg_avp_add(req, MSG_BRW_LAST_CHILD, avp);

tests/non3gpp/s2b-build.c

@@ -46,6 +46,9 @@ ogs_pkbuf_t *test_s2b_build_create_session_request(
 
     ogs_gtp2_indication_t indication;
 
+    char node_identifier_buf[OGS_GTP2_MAX_NODE_IDENTIFIER_LEN];
+    ogs_gtp2_node_identifier_t node_identifier;
+
     ogs_assert(sess);
     test_ue = sess->test_ue;
     ogs_assert(test_ue);
@@ -172,6 +175,16 @@ ogs_pkbuf_t *test_s2b_build_create_session_request(
         (uint8_t *)"\x80\x00\x0d\x00";
     req->additional_protocol_configuration_options.len = 4;
 
+    memset(&node_identifier, 0, sizeof(ogs_gtp2_node_identifier_t));
+    node_identifier.name = "aaa.localdomain";
+    node_identifier.name_len = strlen(node_identifier.name);
+    node_identifier.realm = "localdomain";
+    node_identifier.realm_len = strlen(node_identifier.realm);
+    req->_aaa_server_identifier.presence = 1;
+    ogs_gtp2_build_node_identifier(
+            &req->_aaa_server_identifier, &node_identifier,
+            node_identifier_buf, OGS_GTP2_MAX_NODE_IDENTIFIER_LEN);
+
     gtp_message.h.type = type;
     return ogs_gtp2_build_msg(&gtp_message);
 }