imsi_detach: Add testcase for the crash Tobias experienced on IMSI detach

A simple IMSI detach could crash the nitb application. It has been
fixed but this should be a regression test.

imsi_detach/IMSIDetach.st

@@ -0,0 +1,65 @@
+"
+ (C) 2012 by Holger Hans Peter Freyther
+ All Rights Reserved
+
+ This program is free software: you can redistribute it and/or modify
+ it under the terms of the GNU Affero General Public License as
+ published by the Free Software Foundation, either version 3 of the
+ License, or (at your option) any later version.
+
+ This program is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ GNU Affero General Public License for more details.
+
+ You should have received a copy of the GNU Affero General Public License
+ along with this program.  If not, see <http://www.gnu.org/licenses/>.
+"
+
+PackageLoader fileInPackage: #FakeBTS.
+
+FakeBTS.OpenBSCTest subclass: IMSIDetach [
+    <import: OsmoGSM>
+
+    startTest [
+        "1. Connect to the BTS"
+        self createAndConnectBTS: '1801/0/0'.
+        self testIMSIDetach.
+    ]
+
+    testIMSIDetach [
+        | lchan detach tmsi |
+
+        tmsi := self allocateTmsi: '901010000001111'.
+
+        "2. Get a LCHAN"
+        lchan := self requireAnyChannel.
+
+        "3. Send a IMSI Detach"
+        detach := GSM48IMSIDetachInd new.
+        detach mi tmsi: tmsi.
+        lchan sendGSM: detach toMessage.
+
+        "Wait for the channel to be released.."
+        [
+            | msg |
+            "Read all messages until the end on SAPI=0. Ignore SAPI=3"
+            "If we send another SAPI=3 Release Indication we get a double
+             RF Channel Release from the NITB."
+            [
+            msg := GSM48MSG decode: lchan nextSapi0Msg readStream.
+            (msg isKindOf: GSM48RRChannelRelease)
+                ifTrue: [lchan releaseAllSapis. ^true]
+            ] on: Exception do: [Transcript nextPutAll: 'GSM decoding error'; nl.].
+        ] repeat.
+    ]
+]
+
+Eval [
+    | test |
+
+    test := IMSIDetach new
+                startTest;
+                stopBts;
+                yourself.
+]

imsi_detach/README

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+Test if OpenBSC is crashing on a IMSI detach