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s1ap_proxy: Handle "E-RABs Failed to Setup List" IE

The HANDOVER REQUEST ACKNOWLEDGE PDU may contain an optional IE with
the list of E-RABs that the eNB failed to setup.  The S1GW needs to
handle this list and terminate the respective E-RAB FSMs.

Change-Id: I207094fd0019d10a61a5566c649ded1f98a41967
Related: 05b55609 ("s1ap_proxy: Add support for S1 HANDOVER procedure")
Related: SYS#7309
---
M src/s1ap_proxy.erl
1 file changed, 26 insertions(+), 3 deletions(-)

diff --git a/src/s1ap_proxy.erl b/src/s1ap_proxy.erl
index 658f08c..22c2da7 100644
--- a/src/s1ap_proxy.erl
+++ b/src/s1ap_proxy.erl
@@ -690,8 +690,9 @@
                                  value = C0} = Msg}, S0) ->
     ?LOG_DEBUG("Processing HANDOVER REQUEST ACKNOWLEDGE"),
     ctr_inc(?S1GW_CTR_S1AP_PROXY_IN_PKT_HANDOVER_REQ_ACK, S0),
-    case handle_ies(?'id-E-RABAdmittedList',
-                    C0#'HandoverRequestAcknowledge'.protocolIEs, S0) of
+    %% handle the list of admitted E-RABs
+    {Result, S2} = case handle_ies(?'id-E-RABAdmittedList',
+                                   C0#'HandoverRequestAcknowledge'.protocolIEs, S0) of
         {{ok, IEs}, S1} ->
             C1 = C0#'HandoverRequestAcknowledge'{protocolIEs = IEs},
             PDU = {Outcome, Msg#'SuccessfulOutcome'{value = C1}},
@@ -700,7 +701,13 @@
             ?LOG_NOTICE("Failed to process HANDOVER REQUEST ACKNOWLEDGE: ~p", [Reason]),
             ctr_inc(?S1GW_CTR_S1AP_PROXY_IN_PKT_PROC_ERROR, S1),
             {drop, S1} %% drop this PDU
-    end;
+    end,
+    %% handle the (optional) list of failed E-RABs
+    %% no #proxy_state modification is expected here
+    handle_ies(?'id-E-RABFailedToSetupListHOReqAck',
+               C0#'HandoverRequestAcknowledge'.protocolIEs, S2),
+    {Result, S2};
+
 
 %% TODO: 9.1.5.8 PATH SWITCH REQUEST :: (M) Transport Layer Address
 %% TODO: 9.1.5.9 PATH SWITCH REQUEST ACKNOWLEDGE :: (M) Transport Layer Address
@@ -1149,6 +1156,22 @@
             {{error, erab_not_registered}, S}
     end;
 
+handle_ie([?'id-E-RABFailedToSetupListHOReqAck'], C, S) ->
+    %% This IE contains a list of id-E-RABFailedtoSetupItemHOReqAck, so patch inner IEs
+    handle_ies(?'id-E-RABFailedtoSetupItemHOReqAck', C, S);
+
+handle_ie([?'id-E-RABFailedtoSetupItemHOReqAck',
+           ?'id-E-RABFailedToSetupListHOReqAck'],
+          #'E-RABFailedToSetupItemHOReqAck'{'e-RAB-ID' = ERABId} = C, S) ->
+    %% poke E-RAB FSM
+    case erab_fsm_find(ERABId, S) of
+        {ok, Pid} ->
+            ok = erab_fsm:erab_release_ind(Pid),
+            {{ok, C}, S};
+        error ->
+            ?LOG_ERROR("E-RAB-ID ~p is not registered", [erab_uid(ERABId, S)]),
+            {{error, erab_not_registered}, S}
+    end;
 
 %% Catch-all variant, which should not be called normally
 handle_ie(P, C, S) ->

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