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s1ap_proxy: parse and store Global-ENB-ID IE

This commit prepares for a follow-up change implementing the NFT-based
KPI (GTP-U packets/bytes stats) reporting, which will need the
Global-ENB-ID.

Change-Id: Icc24d4daf06d161d7b5b386456e8e92ac07d5eba
Related: SYS#7307
---
M src/s1ap_proxy.erl
1 file changed, 56 insertions(+), 0 deletions(-)

git pull ssh://gerrit.osmocom.org:29418/erlang/osmo-s1gw refs/changes/68/40368/1

diff --git a/src/s1ap_proxy.erl b/src/s1ap_proxy.erl
index 774fc66..bf5f849 100644
--- a/src/s1ap_proxy.erl
+++ b/src/s1ap_proxy.erl
@@ -67,8 +67,12 @@
 -type enb_ue_id() :: 0..16#ffffff.
 -type erab_id() :: 0..16#ff.
 -type erab_uid() :: {mme_ue_id(), enb_ue_id(), erab_id()}.
+-type plmn_id() :: {MCC :: nonempty_string(),
+                    MNC :: nonempty_string()}.
 
 -record(proxy_state, {erabs :: dict:dict(),
+                      enb_id :: undefined | non_neg_integer(),
+                      plmn_id :: undefined | plmn_id(),
                       mme_ue_id :: undefined | mme_ue_id(),
                       enb_ue_id :: undefined | enb_ue_id(),
                       erab_id :: undefined | erab_id(),
@@ -195,6 +199,35 @@
     ok.
 
 
+%% Parse PLMN-ID as per 3GPP TS 24.008, Figure 10.5.13
+%% | MCC digit 2 | MCC digit 1 |  octet 1
+%% | MNC digit 3 | MCC digit 3 |  octet 2
+%% | MNC digit 2 | MNC digit 1 |  octet 3
+-spec parse_plmn_id(<< _:24 >>) -> plmn_id().
+parse_plmn_id(<< MCC2:4, MCC1:4,
+                 MNC3:4, MCC3:4,
+                 MNC2:4, MNC1:4 >>) ->
+    MCC = parse_mcc_mnc(MCC1, MCC2, MCC3),
+    MNC = parse_mcc_mnc(MNC1, MNC2, MNC3),
+    {MCC, MNC}.
+
+
+-define(UNHEX(H), H + 48).
+
+parse_mcc_mnc(D1, D2, 16#f) ->
+    [?UNHEX(D1), ?UNHEX(D2)];
+
+parse_mcc_mnc(D1, D2, D3) ->
+    [?UNHEX(D1), ?UNHEX(D2), ?UNHEX(D3)].
+
+
+-spec parse_enb_id(tuple()) -> non_neg_integer().
+parse_enb_id({'macroENB-ID', << ID:20 >>}) -> ID;
+parse_enb_id({'homeENB-ID', << ID:28 >>}) -> ID;
+parse_enb_id({'short-macroENB-ID', << ID:18 >>}) -> ID;
+parse_enb_id({'long-macroENB-ID', << ID:21 >>}) -> ID.
+
+
 %% Encode an S1AP PDU
 -spec encode_pdu(s1ap_pdu()) -> {ok, binary()} |
                                 {error, {asn1, tuple()}}.
@@ -260,6 +293,17 @@
 -spec handle_pdu(s1ap_pdu(), proxy_state()) -> {{proxy_action(), s1ap_pdu()}, proxy_state()} |
                                                {forward, proxy_state()}.
 
+%% 9.1.8.4 S1 SETUP REQUEST
+handle_pdu({initiatingMessage,
+            #'InitiatingMessage'{procedureCode = ?'id-S1Setup',
+                                 value = C0}}, S0) ->
+    ?LOG_DEBUG("Processing S1 SETUP REQUEST"),
+    %% there's nothing to patch in this PDU, so we forward it as-is
+    %% TODO: check result of handle_ies(), inc. ?S1GW_CTR_S1AP_PROXY_IN_PKT_PROC_ERROR
+    {_, S1} = handle_ies(?'id-Global-ENB-ID',
+                         C0#'S1SetupRequest'.protocolIEs, S0),
+    {forward, S1};
+
 %% 9.1.3.1 E-RAB SETUP REQUEST
 handle_pdu({Outcome = initiatingMessage,
             #'InitiatingMessage'{procedureCode = ?'id-E-RABSetup',
@@ -538,6 +582,18 @@
          Result :: {handle_ie_result(),
                     proxy_state()}.
 
+handle_ie([?'id-Global-ENB-ID'],
+          #'Global-ENB-ID'{'pLMNidentity' = PLMNId,
+                           'eNB-ID' = ENBId} = C, S0) ->
+    %% store PLMNId/ENBId
+    %% TODO: use that as a context for logging
+    S1 = S0#proxy_state{plmn_id = parse_plmn_id(PLMNId),
+                        enb_id = parse_enb_id(ENBId)},
+    ?LOG_INFO("Global-ENB-ID: PLMN-ID=~p, eNB-ID=~p",
+              [S1#proxy_state.plmn_id,
+               S1#proxy_state.enb_id]),
+    {{ok, C}, S1};
+
 %% E-RAB SETUP REQUEST related IEs
 handle_ie([?'id-E-RABToBeSetupListBearerSUReq'], C, S) ->
     %% This IE contains a list of BearerSUReq, so patch inner IEs

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