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3GPP TS 49.008 '4.3 Roles of MSC-A, MSC-I and MSC-T' defines distinct roles:
- MSC-A is responsible for managing subscribers,
- MSC-I is the gateway to the RAN.
- MSC-T is a second transitory gateway to another RAN during Handover.
After inter-MSC Handover, the MSC-I is handled by a remote MSC instance, while
the original MSC-A retains the responsibility of subscriber management.
MSC-T exists in this patch but is not yet used, since Handover is only prepared
for, not yet implemented.
Facilitate Inter-MSC and inter-BSC Handover by the same internal split of MSC
roles.
Compared to inter-MSC Handover, mere inter-BSC has the obvious simplifications:
- all of MSC-A, MSC-I and MSC-T roles will be served by the same osmo-msc
instance,
- messages between MSC-A and MSC-{I,T} don't need to be routed via E-interface
(GSUP),
- no call routing between MSC-A and -I via MNCC necessary.
This is the largest code bomb I have submitted, ever. Out of principle, I
apologize to everyone trying to read this as a whole. Unfortunately, I see no
sense in trying to split this patch into smaller bits. It would be a huge
amount of work to introduce these changes in separate chunks, especially if
each should in turn be useful and pass all test suites. So, unfortunately, we
are stuck with this code bomb.
The following are some details and rationale for this rather huge refactoring:
* separate MSC subscriber management from ran_conn
struct ran_conn is reduced from the pivotal subscriber management entity it has
been so far to a mere storage for an SCCP connection ID and an MSC subscriber
reference.
The new pivotal subscriber management entity is struct msc_a -- struct msub
lists the msc_a, msc_i, msc_t roles, the vast majority of code paths however
use msc_a, since MSC-A is where all the interesting stuff happens.
Before handover, msc_i is an FSM implementation that encodes to the local
ran_conn. After inter-MSC Handover, msc_i is a compatible but different FSM
implementation that instead forwards via/from GSUP. Same goes for the msc_a
struct: if osmo-msc is the MSC-I "RAN proxy" for a remote MSC-A role, the
msc_a->fi is an FSM implementation that merely forwards via/from GSUP.
* New SCCP implementation for RAN access
To be able to forward BSSAP and RANAP messages via the GSUP interface, the
individual message layers need to be cleanly separated. The IuCS implementation
used until now (iu_client from libosmo-ranap) did not provide this level of
separation, and needed a complete rewrite. It was trivial to implement this in
such a way that both BSSAP and RANAP can be handled by the same SCCP code,
hence the new SCCP-RAN layer also replaces BSSAP handling.
sccp_ran.h: struct sccp_ran_inst provides an abstract handler for incoming RAN
connections. A set of callback functions provides implementation specific
details.
* RAN Abstraction (BSSAP vs. RANAP)
The common SCCP implementation did set the theme for the remaining refactoring:
make all other MSC code paths entirely RAN-implementation-agnostic.
ran_infra.c provides data structures that list RAN implementation specifics,
from logging to RAN de-/encoding to SCCP callbacks and timers. A ran_infra
pointer hence allows complete abstraction of RAN implementations:
- managing connected RAN peers (BSC, RNC) in ran_peer.c,
- classifying and de-/encoding RAN PDUs,
- recording connected LACs and cell IDs and sending out Paging requests to
matching RAN peers.
* RAN RESET now also for RANAP
ran_peer.c absorbs the reset_fsm from a_reset.c; in consequence, RANAP also
supports proper RESET semantics now. Hence osmo-hnbgw now also needs to provide
proper RESET handling, which it so far duly ignores. (TODO)
* RAN de-/encoding abstraction
The RAN abstraction mentioned above serves not only to separate RANAP and BSSAP
implementations transparently, but also to be able to optionally handle RAN on
distinct levels. Before Handover, all RAN messages are handled by the MSC-A
role. However, after an inter-MSC Handover, a standalone MSC-I will need to
decode RAN PDUs, at least in order to manage Assignment of RTP streams between
BSS/RNC and MNCC call forwarding.
ran_msg.h provides a common API with abstraction for:
- receiving events from RAN, i.e. passing RAN decode from the BSC/RNC and
MS/UE: struct ran_dec_msg represents RAN messages decoded from either BSSMAP
or RANAP;
- sending RAN events: ran_enc_msg is the counterpart to compose RAN messages
that should be encoded to either BSSMAP or RANAP and passed down to the
BSC/RNC and MS/UE.
The RAN-specific implementations are completely contained by ran_msg_a.c and
ran_msg_iu.c.
In particular, Assignment and Ciphering have so far been distinct code paths
for BSSAP and RANAP, with switch(via_ran){...} statements all over the place.
Using RAN_DEC_* and RAN_ENC_* abstractions, these are now completely unified.
Note that SGs does not qualify for RAN abstraction: the SGs interface always
remains with the MSC-A role, and SGs messages follow quite distinct semantics
from the fairly similar GERAN and UTRAN.
* MGW and RTP stream management
So far, managing MGW endpoints via MGCP was tightly glued in-between
GSM-04.08-CC on the one and MNCC on the other side. Prepare for switching RTP
streams between different RAN peers by moving to object-oriented
implementations: implement struct call_leg and struct rtp_stream with distinct
FSMs each. For MGW communication, use the osmo_mgcpc_ep API that has originated
from osmo-bsc and recently moved to libosmo-mgcp-client for this purpose.
Instead of implementing a sequence of events with code duplication for the RAN
and CN sides, the idea is to manage each RTP stream separately by firing and
receiving events as soon as codecs and RTP ports are negotiated, and letting
the individual FSMs take care of the MGW management "asynchronously". The
caller provides event IDs and an FSM instance that should be notified of RTP
stream setup progress. Hence it becomes possible to reconnect RTP streams from
one GSM-04.08-CC to another (inter-BSC Handover) or between CC and MNCC RTP
peers (inter-MSC Handover) without duplicating the MGCP code for each
transition.
The number of FSM implementations used for MGCP handling may seem a bit of an
overkill. But in fact, the number of perspectives on RTP forwarding are far
from trivial:
- an MGW endpoint is an entity with N connections, and MGCP "sessions" for
configuring them by talking to the MGW;
- an RTP stream is a remote peer connected to one of the endpoint's
connections, which is asynchronously notified of codec and RTP port choices;
- a call leg is the higher level view on either an MT or MO side of a voice
call, a combination of two RTP streams to forward between two remote peers.
BSC MGW PBX
CI CI
[MGW-endpoint]
[--rtp_stream--] [--rtp_stream--]
[----------------call_leg----------------]
* Use counts
Introduce using the new osmo_use_count API added to libosmocore for this
purpose. Each use token has a distinct name in the logging, which can be a
globally constant name or ad-hoc, like the local __func__ string constant. Use
in the new struct msc_a, as well as change vlr_subscr to the new osmo_use_count
API.
* FSM Timeouts
Introduce using the new osmo_tdef API, which provides a common VTY
implementation for all timer numbers, and FSM state transitions with the
correct timeout. Originated in osmo-bsc, recently moved to libosmocore.
Depends: Ife31e6798b4e728a23913179e346552a7dd338c0 (libosmocore)
Ib9af67b100c4583342a2103669732dab2e577b04 (libosmocore)
Id617265337f09dfb6ddfe111ef5e578cd3dc9f63 (libosmocore)
Ie9e2add7bbfae651c04e230d62e37cebeb91b0f5 (libosmo-sccp)
I26be5c4b06a680f25f19797407ab56a5a4880ddc (osmo-mgw)
Ida0e59f9a1f2dd18efea0a51680a67b69f141efa (osmo-mgw)
I9a3effd38e72841529df6c135c077116981dea36 (osmo-mgw)
Change-Id: I27e4988e0371808b512c757d2b52ada1615067bd
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Depends: Ife31e6798b4e728a23913179e346552a7dd338c0 (libosmocore)
Change-Id: Ib06d030e8464abe415ff597d462ed40eeddef475
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So far, sms_pending_failed() starts a new sms_queue_trigger() run. The
intention behind that might have been to fill up the queue when sending SMS has
failed, but the practical effect is actually bad:
As current ttcn3-msc-test runs show, a failed MT SMS gets triggered multiple
times in short succession, i.e. osmo-msc repeatedly sends Paging Requests for
the same subscriber.
This special case happens actually only when there are few SMS still in the DB
to be delivered. In the TTCN3 test, there is exactly one MT SMS for one
subscriber, and retriggering the queue brings up the same SMS every time.
See f_tc_lu_and_mt_sms_paging_and_nothing() and f_tc_sgsap_mt_sms_and_nothing()
which say:
"/* Expect the MSC to page exactly 10 times before giving up */"
This is bad because an MSC should send a Paging Request exactly once. Retrying
failed Paging is clearly the task of the BSC, not the MSC. The remaining code
around Paging correctly follows this paradigm, but this retrigger doesn't.
Do not immediately trigger the SMS queue on a failed MT SMS. Instead, leave it
up to the periodical SMS queue trigger to decide.
This patch will cause the MT SMS tests in ttcn3-msc-tests to fail, because the
test expectations are bogus. The patch fixing the test run is listed 'Related'
below.
Related: I7dce12942a65eaaf97f78ca69401c7f93faacb9e (osmo-ttcn3-hacks)
Change-Id: I24bf9f1c1167efe1080ae4cf47ed2ef0bd981e49
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If subscriber is NULL, vlr_subscr_msisdn_or_name() returns string
"unknown", which is less informative than printing destination msisdn
expected for the queued sms.
This happens for instance if an sms was queued with Store&Forward and
destination subscriber is not currently registered
Change-Id: I4b8b54c9c41b17d4e1fa7ece63aa91a98036ef11
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A memleak has been noticed after executing some of TTCN-3 test
cases. For example, the following ones:
- MSC_Tests.TC_lu_and_mo_sms,
- MSC_Tests.TC_lu_and_mt_sms.
The key point is that MSC_Tests.TC_lu_and_mo_sms basically sends
a MO SMS to a non-attached subscriber with MSISDN 12345, so this
message is getting stored in the SMSC's database.
As soon as the SMSC's queue is triggered, sms_submit_pending() would
retrieve pending messages from the database by calling function
smsq_take_next_sms() in loop and attempt to deliver them.
This function in it's turn checks whether the subscriber is attached
or not. If not, the allocated 'gsm_sms' structure would not be
free()ed! Therefore, every time smsq_take_next_sms() is called,
one 'gsm_sms' structure for an unattached subscriber is leaked.
Furthermore, there is a unit test called 'sms_queue_test', that
actually does cover smsq_take_next_sms() and was designed to
catch some potential memory leaks, but...
In order to avoid emulating the low-level SQLite API, the unit
test by design overwrites some functions of libmsc, including
db_sms_get_next_unsent_rr_msisdn(), that is being called by
smsq_take_next_sms().
The problem is that the original function in libmsc does
allocate a 'gsm_sms' structure on heap (using talloc), while
the overwriting function did this statically, returning a
pointer to stack. This critical difference made it impossible
to spot the memleak in smsq_take_next_sms() during the
unit test execution.
Let's refactor 'sms_queue_test' to use dynamic memory allocation,
and finally fix the evil memleak in smsq_take_next_sms().
Change-Id: Iad5e4d84d8d410ea43d5907e9ddf6e5fdb55bc7a
Closes: OS#3860
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Change-Id: I16f2d29855eb715eccbdc5def225f43c110fab8e
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gsm_subscriber.h contains some legacy cruft, part of which is that the VLR's
max MSISDN length should rather be defined in vlr.h. Same for GSM_NAME_LENGTH
-> VLR_NAME_LENGTH.
Adjust some sms_queue stuff that anyway includes vlr.h already.
Drop gsm_subscriber.h from vlr.h.
Add other (more concise) includes that thus become necessary, since the include
chain vlr.h->gsm_subscriber.h->gsm_data.h is no longer in place.
Change-Id: Iab5c507ec04fc2884187cf946f6ae2240e4a31f8
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According to GSM TS 04.11, the SMC (Short Message Control) state
machine is a part of CM-sublayer of L3, that is responsible for
connection management (establisment and releasing), and SM-RP
(Relay Protocol) message delivery.
For some reason, the connection establisment request from SMC
(GSM411_MMSMS_EST_REQ) was not handled properly - it was
always assumed that connection is already established.
This is why the code initiating a MT (Mobile Terminated) SMS
transfer had to establish a radio connection with subscriber
manually.
Let's benefit from having the SMC state machine, and offload
connection establishment to it. This change makes the local
implementation closer to GSM TS 04.11, and facilitates the
further integration of GSUP transport.
NOTE: the expected unit test output is changed, because now we
always allocate a transaction first, and then establish a
connection, not vice versa.
Change-Id: I4a07ece80d8dd40b23da6bb1ffc9d3d745b54092
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Change-Id: Ie5883953f48d11ec498f47c30ab4201bb956368c
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This bug is super obvious: We cannot first call
sms_pending_free(pending) and then in the next line still dereference
the pending->sms_id member.
This bug was introduced in January with Change-Id: I3749855fe25d9d4e37ec96b0c2bffbc692b66a78
and apparently nobody has tested any MT-SMS with asan enabled since?
Change-Id: Ibf17f270cdeb8153036eda3de274dd163bbff7e6
Closes: OS#3152
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We don't usually put space before in-place increment or decrement. Let's
make code look similar to other Osmocom projects.
Change-Id: I5962431ad16c97e412939dc1b8949f6361a5c26e
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Using following semantic patch:
@@ expression A, B, C; @@
- osmo_strlcpy(A, B, sizeof(A));
+ OSMO_STRLCPY_ARRAY(A, B);
Which was applied using following command:
spatch --dir src -I src --sp-file strlcpy.spatch --in-place --recursive-includes
All the calls to osmo_strlcpy() which use destination buffer obtained
via sizeof() were replaced with the corresponding wrapper macro.
Change-Id: I67b482dedfa11237ac21894fc5930039e12434ab
Related: OS#2864
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Delete expired SMS whenever we are done processing an SMS-related signal.
In order to minimize additional latency only one SMS is removed at a time.
Change-Id: I56cbe716e52b679c4b94f6cbb4a171306975be2e
Related: OS#2354
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We already delete SMS which have been sent successfully. However, there
are plans to accept SMS for any subscriber in order to fix the problem
described in https://osmocom.org/issues/2354 ("SMSC: Store&Forward not
working for subscribed but unregistered MS").
This means we may end up storing SMS which never get sent, e.g. because
the B subscriber doesn't actually exist. This could lead to a higher
degree of SMS database growth over time, and therefore we need a way
to keep database size under control.
As a first step, introduce a DB function which removes an expired SMS,
and add a VTY command which removes all expired SMS from the DB.
Later commits will build upon this to remove expired SMS automatically.
The SMS expiry time period is currently hard-coded to 2 weeks.
We could make this configurable in the future if desired.
Change-Id: Icd6093b7b5d8db84b19a0aa47c68182566113ee2
Related: OS#2354
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osmo-msc still had large amounts of dead code that came along from
openbsc.git. This commit removes a lot of it, mostly stuff relevant
only to the BSC side of things (or even GPRS).
Change-Id: I247def85da2dc3ec461389fb74414a0d964e7e3c
Related: OS#2528
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Currently the SMS database keeps accumulating entries for each SMS.
These entries are never deleted automatically. With this change, we
start deleting SMS which have successfully been sent to subscriber B.
Change-Id: I3749855fe25d9d4e37ec96b0c2bffbc692b66a78
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Change-Id: I1f96a1285bbd1b4607614856bca935d5c26e2da9
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Original libvlr code is by Harald Welte <laforge@gnumonks.org>,
polished and tweaked by Neels Hofmeyr <nhofmeyr@sysmocom.de>.
This is a long series of trial-and-error development collapsed in one patch.
This may be split in smaller commits if reviewers prefer that. If we can keep
it as one, we have saved ourselves the additional separation work.
SMS:
The SQL based lookup of SMS for attached subscribers no longer works since the
SQL database no longer has the subscriber data. Replace with a round-robin on
the SMS recipient MSISDNs paired with a VLR subscriber RAM lookup whether the
subscriber is currently attached.
If there are many SMS for not-attached subscribers in the SMS database, this
will become inefficient: a DB hit returns a pending SMS, the RAM lookup will
reveal that the subscriber is not attached, after which the DB is hit for the
next SMS. It would become more efficient e.g. by having an MSISDN based hash
list for the VLR subscribers and by marking non-attached SMS recipients in the
SMS database so that they can be excluded with the SQL query already.
There is a sanity limit to do at most 100 db hits per attempt to find a pending
SMS. So if there are more than 100 stored SMS waiting for their recipients to
actually attach to the MSC, it may take more than one SMS queue trigger to
deliver SMS for subscribers that are actually attached.
This is not very beautiful, but is merely intended to carry us over to a time
when we have a proper separate SMSC entity.
Introduce gsm_subscriber_connection ref-counting in libmsc.
Remove/Disable VTY and CTRL commands to create subscribers, which is now a task
of the OsmoHLR. Adjust the python tests accordingly.
Remove VTY cmd subscriber-keep-in-ram.
Use OSMO_GSUP_PORT = 4222 instead of 2222. See
I4222e21686c823985be8ff1f16b1182be8ad6175.
So far use the LAC from conn->bts, will be replaced by conn->lac in
Id3705236350d5f69e447046b0a764bbabc3d493c.
Related: OS#1592 OS#1974
Change-Id: I639544a6cdda77a3aafc4e3446a55393f60e4050
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This is the first step in creating this repository from the legacy openbsc.git.
Like all other Osmocom repositories, keep the autoconf and automake files in
the repository root. openbsc.git has been the sole exception, which ends now.
Change-Id: I9c6f2a448d9cb1cc088cf1cf6918b69d7e69b4e7
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