neels has uploaded this change for review.
allow second CS RAB Assignment Request
In the field, we've encountered a so far unsupported scenario: after a
RAB Assignment Request and Response have successfully set up an RTP
stream, the CN sends *another* RAB Assignment Request to modify some SDU
parameters, omitting the transportLayerInformation IE (not modifying the
RTP address).
Detect a secondary RAB Assignment Request, and just forward it as-is:
the hNodeB is interested in the RAB configuration, osmo-hnbgw just needs
the RTP info, which is not even present in this use case.
Do not (yet?) support modifying the RTP address/port.
Related: osmo-ttcn3-hacks Iadaba0e5e82ad6d163ad509904ede213e2462d5c
Related: SYS#6624
Change-Id: I25bf19981cd75a87a7ceb3382dae1ec626ae475c
---
M src/osmo-hnbgw/mgw_fsm.c
1 file changed, 79 insertions(+), 0 deletions(-)
git pull ssh://gerrit.osmocom.org:29418/osmo-hnbgw refs/changes/74/34974/1
diff --git a/src/osmo-hnbgw/mgw_fsm.c b/src/osmo-hnbgw/mgw_fsm.c
index ddab0b5..3bbd8c6 100644
--- a/src/osmo-hnbgw/mgw_fsm.c
+++ b/src/osmo-hnbgw/mgw_fsm.c
@@ -683,6 +683,47 @@
return 0;
}
+static bool is_rab_ass_without_tli(struct hnbgw_context_map *map, ranap_message *message)
+{
+ RANAP_RAB_AssignmentRequestIEs_t *ies;
+ RANAP_ProtocolIE_ContainerPair_t *protocol_ie_container_pair;
+ RANAP_ProtocolIE_FieldPair_t *protocol_ie_field_pair;
+ RANAP_RAB_SetupOrModifyItemFirst_t _rab_setup_or_modify_item_first = { 0 };
+ RANAP_RAB_SetupOrModifyItemFirst_t *rab_setup_or_modify_item_first = &_rab_setup_or_modify_item_first;
+ int rc;
+ bool ret;
+
+ ies = &message->msg.raB_AssignmentRequestIEs;
+
+ if (!(ies->presenceMask & RAB_ASSIGNMENTREQUESTIES_RANAP_RAB_SETUPORMODIFYLIST_PRESENT))
+ return false;
+
+ /* Detect the end of the list */
+ if (ies->raB_SetupOrModifyList.list.count < 1)
+ return false;
+
+ protocol_ie_container_pair = ies->raB_SetupOrModifyList.list.array[0];
+ protocol_ie_field_pair = protocol_ie_container_pair->list.array[0];
+
+ if (!protocol_ie_field_pair)
+ return false;
+
+ if (protocol_ie_field_pair->id != RANAP_ProtocolIE_ID_id_RAB_SetupOrModifyItem) {
+ RANAP_DEBUG
+ ("Decoding failed, the protocol IE field-pair is not of type RANAP RAB setup-or-modify-item!\n");
+ return false;
+ }
+
+ rc = ranap_decode_rab_setupormodifyitemfirst(rab_setup_or_modify_item_first,
+ &protocol_ie_field_pair->firstValue);
+ if (rc < 0)
+ return false;
+
+ ret = rab_setup_or_modify_item_first->transportLayerInformation == NULL;
+ ASN_STRUCT_FREE_CONTENTS_ONLY(asn_DEF_RANAP_RAB_SetupOrModifyItemFirst, rab_setup_or_modify_item_first);
+ return ret;
+}
+
/* Check if the message contains a RAB-ReleaseItem that matches the RAB-ID that is managed by the given context map */
static bool is_our_rab_release(struct hnbgw_context_map *map, ranap_message *message)
{
@@ -721,6 +762,14 @@
initialized = true;
}
+ /* After a normal RAB Assignment, another RAB Assigment may follow, modifying some RAB parameters. This second
+ * RAB Assignment may omit transportLayerInformation (remains unchanged). Simply forward this to RUA, without
+ * the need to adjust anything here. Allow this only when there already is an mgw_fsm with proper address. */
+ if (map->mgw_fi && is_rab_ass_without_tli(map, message)) {
+ LOG_MAP(map, DCN, LOGL_INFO, "Rx secondary RAB Assignment Request, forwarding as-is\n");
+ return map_rua_dispatch(map, MAP_RUA_EV_TX_DIRECT_TRANSFER, ranap_msg);
+ }
+
/* The RTP stream negotiation usually begins with a RAB-AssignmentRequest and ends with an IU-Release, however
* it may also be that the MSC decides to release the RAB with a dedicated RAB-AssignmentRequest that contains
* a ReleaseList. In this case an FSM will already be present. */
@@ -791,6 +840,13 @@
return -1;
}
+ if (map->mgw_fi->state == MGW_ST_ESTABLISHED) {
+ /* This is a response to a second RAB Assignment Request, which only modified some RAB config on top of
+ * an earlier RAB Assignment. Just forward the response as-is, we already have our MGW set up and need
+ * no info from it. (i.e. we don't support modifying the RTP address.) */
+ return map_sccp_dispatch(map, MAP_SCCP_EV_TX_DATA_REQUEST, ranap_msg);
+ }
+
mgw_fsm_priv = map->mgw_fi->priv;
talloc_steal(mgw_fsm_priv, ranap_msg);
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