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Use the fact that the MS must answer the RRBP of the Pkt Cell Change
Continue with a CTRL ACK to find out whether the message was received
successfuly or a retransmission is potentially required.
3GPP TS 44.060:
"""
When the mobile station receives the PACKET CELL CHANGE ORDER or
the PACKET CELL CHANGE CONTINUE message the mobile station shall
transmit a PACKET CONTROL ACKNOWLEDGMENT message in the specified
uplink radio block if a valid RRBP field is received as part of the
message; the mobile station may then switch to a new cell.
"""
Related: SYS#4909
Change-Id: I7cc28922e71699598da0ef6eb90136a47d3c002f
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A new nacc_fsm is introduced per MS object, with its partner priv
structure struct nacc_fsm_ctx, which exists and is available in the MS
object only during the duration of the NACC procedure.
The NACC context is created on an MS whenever a Pkt Cell Change
Notification is received on Uplink RLCMAC, which asks for neighbor
information of a given ARFCN+BSIC.
First, the target ARFCN+BSIC needs to be translated into a CGI-PS
(RAC+CI) address. That's done by asking the BSC through the Neighbour
Resolution Service available in osmo-bsc using the CTRL interface.
Once the CGI-PS of the target cell is known, PCU starts a RIM RAN-INFO
request against the SGSN (which will route the request as needed), and
wait for a response containing the SI bits from the target cell.
After the SI are received, the scheduler is instructed to eventually
poll a TBF for the MS originating the CCN, so that we can send the SI
encapsulated into multiple Packet Neighbor Cell Data messages on the
downlink.
One all the SI bits are sent, the scheduler is instructed to send a
Packet Cell Change Continue message.
Once the message above has been sent, the FSM autodestroys itself.
Caches are also introduced in this patch which allows for re-using
recently known translations ARFCN+BSIC -> CGI-PS and CGI-PS -> SI_INFO
respectively.
Change-Id: Id35f40d05f3e081f32fddbf1fa34cb338db452ca
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Under some circumstances, it could happen that a DL TBF is created as a
GPRS TBF due to not yet having enough information of the MS, and only
after the TBF is created the PCU gains that information and upgrades the
MS mode to "EGPRS". Hence, there's the possibility to run into a
situation where a GPRS TBF is attached to a EGPRS MS.
It may also happen sometimes that despite the TBF and the MS be EGPRS,
there's need to further limit the DL MCS to use, eg. MCS1-4 (GMSK).
As a result, when asking for the current DL (M)CS to use, we must tell
the MS which kind of limitations we want to apply. The later reasoning
was already implemented when GPRS+EGPRS multiplexing was added, but the
former was not being checked. Hence, by further spreading through the
call stack the "req_kind_mode" we match both cases.
Related: OS#4973
Change-Id: Ic0276ce045660713129f0c72f1158a3321c5977f
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Previous work on BTS class started to get stuff out of the C++ struct
into a C struct (BTS -> struct gprs_glcmac_bts) so that some parts of
it were accessible from C code. Doing so, however, ended up being messy
too, since all code needs to be switching from one object to another,
which actually refer to the same logical component.
Let's instead rejoin the structures and make sure the struct is
accessible and usable from both C and C++ code by rewriting all methods
to be C compatible and converting 3 allocated suboject as pointers.
This way BTS can internally still use those C++ objects while providing
a clean APi to both C and C++ code.
Change-Id: I7d12c896c5ded659ca9d3bff4cf3a3fc857db9dd
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Let's use usual osmocom rate_ctr instead of having one variable +
setter/getter functions, so we can easily add new counters and also
because it makes code more clear (no need to look at what the "update"
function is doing).
Using rate counter also provides info about how recently the MS has been
interacting with the network.
Related: OS#4907
Change-Id: I744507fde4291955c1dbbb9739b18a12a80145b1
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As we integrate osmo-pcu more and more with libosmocore features, it
becomes really hard to use them since libosmocore relies heavily on C
specific compilation features, which are not available in old C++
compilers (such as designated initializers for complex types in FSMs).
GprsMs is right now a quite simple object since initial design of
osmo-pcu made it optional and most of the logic was placed and stored
duplicated in TBF objects. However, that's changing as we introduce more
features, with the GprsMS class getting more weight. Hence, let's move
it now to be a C struct in order to be able to easily use libosmocore
features there, such as FSMs.
Some helper classes which GprsMs uses are also mostly move to C since
they are mostly structs with methods, so there's no point in having
duplicated APIs for C++ and C for such simple cases.
For some more complex classes, like (ul_,dl_)tbf, C API bindings are
added where needed so that GprsMs can use functionalitites from that
class. Most of those APIs can be kept afterwards and drop the C++ ones
since they provide no benefit in general.
Change-Id: I0b50e3367aaad9dcada76da97b438e452c8b230c
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The assumption that TLLI 0x00000000 is invalid and can be used
as the initializer is wrong. Similar to TMSI, 0x00000000 is a
perfectly valid value, while 0xffffffff is reserved - use it.
According to 3GPP TS 23.003, section 2.4, a TMSI/P-TMSI with
all 32 bits equal to 1 is special and shall not be allocated by
the network. The reason is that it must be stored on the SIM,
where 'ff'O represents the erased state. According to section
2.6 of the same document, a local/foreign TLLI is derived from
P-TMSI, so the same rule applies to TLLI.
I manually checked and corrected all occurances of 'tlli' in the
code. The test expectations have been adjusted with this command:
$ find tests/ -name "*.err" | xargs sed -i "s/0x00000000/0xffffffff/g"
so there should be no behavior change. The only exception is
the 'TypesTest', where TLLI 0xffffffff is being encoded and
expected in the hexdump, so I regenerated the test output.
Change-Id: Ie89fab75ecc1d8b5e238d3ff214ea7ac830b68b5
Related: OS#4844
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Avoid passing tons of params to internal helper function
tbf_nel_dl_assignment() in order to either fetch again the ms object or
create a new one. Let's instead create the ms function earlier if needed
and fill it with all the discovered information prior to calling the
helper function. This provides cleaner code and also better log output.
This way we also avoid trying to fill the MS twice and unneeded
getter+setter for TA.
tbf::imsi(): There' always an ms, so simply forward call to
ms()->imsi().
We can also get rid of assign_imsi, since the modified code is the only
place where it's used and there's already some code in place there to
update the MS. We instead merge it with set_imsi and keep the
duplication code to catch possible bugs from callers.
Move merge_and_clear_ms from tbf class to GprsMS, where it really
belongs.
Change-Id: Id18098bac3cff26fc4a8d2f419e21641a1f4c83b
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Change-Id: Ifd98abbcce49e4605c764267965903fbf9f35867
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Change-Id: Ib304ced06531a5154b7ec8bf87f9717dfd7d1397
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Change-Id: I987af0d33b79302c037d062c9d1c828a0e027147
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We have same kind of object splitted into two layers, in coding_scheme
and gprs_coding_scheme. Let's merge them together and get rid of the
class, which is not really useful because it's only a set of functions
operating on one enum value.
This change also fixes gcc 10.1.0 error about memseting a complex type
in rlc.h init().
Change-Id: Ie9ce2144ba9e8dbba9704d4e0000a2929e3e41df
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It's a good start towards clearing current mess between parent and the 2
children classes.
Change-Id: Ibc22ea2e02609af7ee058b8bc15df2115d4c6f60
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Receive an Application Information Request from the BTS via PCU
interface. Construct a Packet Application Information message from it
(3GPP TS 44.060 11.2.47) and send it to all MS with active TBF.
The TTCN-3 test infrastructure to test this feature is not quite ready
yet, so I've added C unit tests instead.
Related: OS#4048
Change-Id: Ie35959f833f46bde5f2126314b6f96763f863b36
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Move Mode (EDGE/GPRS) definition and related functions outside of
GprsCodingScheme class. This allows us to use standard libosmocore
value_string functions.
Change-Id: I3baaac7f1ca3f5b88917a23c1679d63847455f47
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Move generic MCS enum to C header file to simplify further modifications
to GprsCodingScheme class in follow-up patches. This also allows us
to use standard libosmocore value_sting functions in upcoming patches
for IA Rest Octet encoding/decoding.
Related: OS#3014
Change-Id: I993b49d9a82b8c7ad677d52d11003794aeabe117
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Many files include unnecessary headers and don't include headers which
are actually used. Because of that combined with the fact that OsmoPCU
is a mixture of C and C++, it makes it hard to modularize code. Fix
this (using iwyu [1] tool):
* add missing headers
* remove unused headers
[1] https://include-what-you-use.org/
Related: OS#1539
Change-Id: I8c9f488a43b099c72b2d30d3245e7ba50872fc00
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Change-Id: I59da04edd1b8ff965bbfbe00ccae1f7c9b6e5301
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Adds spb counters at BTS level(show bts statistics).
Adds RLC/MAC downlink control msg at ms level(show ms imsi <imsi_val>).
Adds the number of coding schemes counter for UL at TBF level.
Change-Id: Icbe4ba95e34bea89ee36f532d099db68204b7c38
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Add accessor function in existing classes to support ARQ-II for
retransmission in EGPRS DL
Change-Id: Iefff956bf2dcfe8fb0b2f5a7a7a2122d5d555f9e
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The PACCH is specific to an MS and may change when a TBF is
established or removed (see TS 44.060, 8.1.1.2.2). For multislot
class type 2 phones, more than one timeslot may be used to transmit
RLC/MAC control messages.
Add a method that returns a set of TS which can be used for the
PACCH.
Sponsored-by: On-Waves ehf
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Currently the TBF and MS object use a plain integer value
(current_cs) to manage the coding scheme. This makes it difficult to
support the MCS schemes. GprsCodingScheme supports a partial ordering
of these values (CS and MCS) and provides safe increment and
decrement methods.
Use the GprsCodingScheme type instead of integer for cs fields and
variables. Add a 'mode' to GprsMs which can be set to either GPRS,
EGPRS, or EGPRS_GMSK which also set the initial values of
current_cs_ul/dl. Select the mode based on max_mcs_ul and max_mcs_dl.
Sponsored-by: On-Waves ehf
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The EGPRS MS class ist contained in the MS_RA_capability information.
Its presence indicates, that the MS is able (and willing) to use
EGPRS.
This commit implements basic support for retrieving, storing, and
showing it in the VTY. The information is stored in the MS object.
Sponsored-by: On-Waves ehf
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Currently an existing DL TBF can get lost in the process of
establishing an UL TBF via RACH. This can lead to stalled connections
until the network sends more LLC frames.
This commit adds a check for a non-empty LLC queue after the UL TBF
has been established to rcv_control_ack (GPRS_RLCMAC_UL_ASS_WAIT_ACK
path) to eventually establish a new DL TBF on the UL TBF's PACCH.
Sponsored-by: On-Waves ehf
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Currently when calling GprsMs::attach_tbf and a TBF of the same
direction already exists, the old TBF gets detached from the MS
object.
Therefore that TBF object loses access to that MS object including
for instance TLLI and IMSI.
This leads to failing DL TBF reuses, since the downlink assigment
cannot be sent on the PACCH later on because that must be sent on the
old DL TBF which ms() is NULL and the new DL TBF cannot be retrieved.
This commit fixes this bug by changing the GprsMs implementation to
keep a list of replaced (old) TBFs. TBFs are only removed when they
are being detached explicitely (see tbf_free and set_ms).
Addresses:
tbf.cpp:741 We have a schedule for downlink assignment at uplink
TBF(TFI=1 TLLI=0xf35a680e DIR=UL STATE=RELEASING), but there is no
downlink TBF
Sponsored-by: On-Waves ehf
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Currently the merging of the meta information (MS class, IMSI) takes
place in gprs_rlcmac_tbf::merge_and_clear_ms(). This makes it
difficult to merge the internal state and does not directly relate to
TBFs anyway.
This commit moves this into a new method GprsMs::merge_old_ms.
Sponsored-by: On-Waves ehf
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When doing an RA Update the network can request to change the TLLI.
In this case, there can be 2 MS objects with different TLLI for a
single real MS. The first is associated with the old TLLI and the
IMSI, while the second is associated with the new TLLI and no IMSI if
it had been created for the uplink TBF. When the first message with
the new TLLI and the IMSI arrives from the network, the PCU is able
to detect this.
Currently this is not handled properly. The TBFs of the old MS object
are not cleaned up properly, keeping the old MS from being deleted.
This patch modifies gprs_rlcmac_dl_tbf::handle to check for this and
if neccessary to move an existing DL TBF and to clean up the old MS
object to ensure its deletion.
Sponsored-by: On-Waves ehf
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Currently packets are only dropped if they have reached their maximum
life time. This leads to LLC queues being constantly filled under
load, increasing the latency up to the maximum life time. This kind
of bufferbloat hinders TCP's congestion avoidance algorithms. To keep
the queues short, the CoDel active queue management algorithm can be
used.
This commit changes to llc_dequeue method to apply the CoDel
algorithm to selectively drop LLC frames before they passed to the
TBF layer to be encoded in BSNs. This feature is currently disabled
by default.
The CoDel state is managed per MS since the LLC queues are also kept
in the MS objects.
Note that there is still some buffering in the TBF objects, in the
worst case (CS4) 3.5kByte + LLC-MTU octets are stored there. The
resulting additional packet delay is not (yet) taken into account for
CoDel.
Also note that configuration changes are applied to new MS objects
only.
The following VTY commands are added to the 'pcu' node:
- queue codel activates CoDel, the interval is selected by
the implementation
- queue codel interval <1-1000>
activates CoDel with a fixed interval given
in centiseconds (10ms-10s)
- no queue codel deactivates CoDel
Which interval value to use is still an open issue. For high speed
links (e.g. Ethernet), CoDel suggests 100ms. For slower links, the
expected RTT is recommended. The current implementation uses a
default value of 2000ms.
Measurements:
Note that the following measurements depend on several other factors,
most notably the interaction with the SGSN's flow control. They are
just examples to give an idea how CoDel might influence some
parameters.
The measurements have been done with a single E71, first with a
running ping only (Idle), then with an additional TCP download
of a 360k file (Busy). The CoDel interval was set to 1s.
- Idle :
ping ~400ms, avg queue delay 0ms, dropped 0
- Busy, No CoDel:
ping ~6s, avg queue delay 4-6s,
dropped 0, scheduled 948, duration 54s
- Busy, CoDel:
ping 500-1500ms, avg queue delay ~600ms,
dropped 77, scheduled 1040, duration 60s
More measurements with two MS downloading in parallel (two
independant measurements per case).
- Busy, No CoDel:
dropped 0, scheduled 1883, duration 121s
dropped 19, scheduled 2003, duration 133s
- Busy, CoDel:
dropped 22, scheduled 1926, duration 116s
dropped 22, scheduled 1955, duration 108s
Sponsored-by: On-Waves ehf
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Currently there is no simple way to determine, whether the MS object
protected by a guard will continue to exist after the guard object is
destroyed.
This patch adds a is_idle() method that will return true if the MS
object is just kept by the guard from being idle. In that case, the
MS object would either be deleted or return true for
GprsMs::is_idle() after the guard's destruction, provided that no
TBF attachment took place in between.
Sponsored-by: On-Waves ehf
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This commits adds methods to GprsMs and gprs_rlcmac_tbf to retrieve
the slots that are actively used.
Sponsored-by: On-Waves ehf
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In contrast to the slots currently used by existing TBFs, the
reserved slots refer to the time slots that can be used for newly
allocated TBFs without causing conflicts (given that the first common
TS does not change). They correspond to the potential use of the
PDCHs and can be used to achieve a more uniform slot allocation.
This commit adds bit set based methods to GprsMs and gprs_rlcmac_trx
and a counter to gprs_rlcmac_pdch. The current TRX will also be
stored in the MS object.
Sponsored-by: On-Waves ehf
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To avoid the need for a switch or conditional statement when needing
a TBF from an MS object in direction independant code, this method
contains that case distinction. For additional flexibility, a
reverse() function is added to get the opposite direction.
Sponsored-by: On-Waves ehf
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This method gets the index (0 based) of first common time slot used
by the TBFs attach to it. It expects that all of them have the same
notion of this. If no TBF is attached, -1 will be returned.
Sponsored-by: On-Waves ehf
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If just a few bytes are left to send to the MS, it makes sense to
reduce the coding scheme level to increase the throughput. This
has been shown by Chen and Goodman in their paper "Theoretical
Analysis of GPRS Throughput and Delay". See their throughput over C/I
measurement graphs (figures 4 and 5 in the paper) for details.
This commit implements a simplified CS downgrade feature for the
downlink. The coding scheme will be downgraded if there are only a
few octets are left to be send over the TBF (see the
downgrade-threshold command below) and the NACK rate is not low (the
CS will not get degraded on a high quality RF link). As an exception,
CS-3 will be degraded to CS-1, since CS-2 does not improve the
throughput in general when a few small packets are sent and the
signal fades slowly (see Chen/Goodman).
The following VTY command is added to the config-pcu node:
- cs downgrade-threshold <1-10000>
- cs no downgrade-threshold
to set the threshold of the number of remaining bytes to be RLC/MAC
encoded. The CS will only be reduced, if the number is below the
threshold. The 'no' command disables this feature completely. The
default value is 200 octets.
Sponsored-by: On-Waves ehf
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Currently the NACK/unconfirmed ratio is already passed to the
corresponding MS object, but the value is not being stored there.
This commit adds a member and a getter method and include the values
into the output of the 'show ms' command.
Sponsored-by: On-Waves ehf
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This commits adds the GprsMs::update_l1_meas() and GprsMs::l1_meas()
methods to store and access the measurement values. The internal
state is updated depending on which values are actually set.
In addition, these values are shown in the output of the 'show ms
imsi|tlli' command.
Sponsored-by: On-Waves ehf
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Currently the CS level is immediately increased if the error rate
drops below the lower threshold. Since the measurement values are not
damped, this behaviour leads to a quick return to higher CS values
even under bad radio conditions. Since with GPRS RLC/MAC blocks
cannot be resent with another coding scheme, increasing the CS value
should be done carefully.
This commit adds a blocking period that only allows higher CS values
if all error rate measurements were below the LOW threshold for a
certain amount of time (currently fixed to 1s).
Ticket: #1674
Sponsored-by: On-Waves ehf
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To cope with transmission failures due to bad radio conditions, a
different coding scheme with more redundance can be used.
This commit adds an implemenation that is based on the Ack/Nack
ratio per PACKET DOWNLINK ACK/NACK message received from the MS.
Basically the CS level is decreased, if the block error rate goes
above cs_adj_upper_limit (default 33%), and it is increased, if the
rate drops below cs_adj_lower_limit (default 10%). Only blocks that
have been encoded with the current CS are taken into account.
Note that this approach doesn't measure the MS->BTS conditions and
that the measurement values reported by the MS are not taken into
account.
Ticket: #1739
Sponsored-by: On-Waves ehf
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Currently the current CS value is stored in the cs field of
gprs_rlcmac_tbf and initialised when it is used the first time.
This commit adds separate fields for UL and DL CS values to the
GprsMs class and provides corresponding getter methods for GprsMs and
gprs_rlcmac_tbf.
Ticket: #1739
Sponsored-by: On-Waves ehf
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Since more functionality will be moved to the GprsMs class, a pointer
to the current BTS object is added to allow access to configuration
data and other methods.
Sponsored-by: On-Waves ehf
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The ms_class value is a property of the MS and thus belongs to the
GprsMs class. Nevertheless the MS object is created after the TLLI
gets known, so the value still has to be stored in the TBF initially.
This commit add the ms_class value to the GprsMs class and introduces
TBF accessor functions which either access that object or, if that is
not available, the value stored locally.
Ticket: #1674
Sponsored-by: On-Waves ehf
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Currently the enqueued DL LLC messages which have not yet passed to
RLC/MAC encoding are eventually copied from one TBF to the next one
(see gprs_rlcmac_dl_tbf::reuse_tbf). Since the enqueued LLC messages
are related to a specific MS, they should be stored at that layer.
This commit moves the gprs_llc_queue object to GprsMs and changes the
TBF's accessor methods accordingly. The LLC copying code is removed
from gprs_rlcmac_dl_tbf::reuse_tbf().
Sponsored-by: On-Waves ehf
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Currently the MS object is immediately idle when all TBFs are
detached and if no guard is being used. Since the plan is to use the
MS objects to pass information from one TBF to the next one even
across the gap of some seconds of inactivity, a mechanism is needed
to keep the MS objects around for some time.
This commit extends the GprsMs class by a timer that keeps the MS
objects in non-idle state for some time after all TBFs have been
detached. The set_timeout method must be used with a non-zero value
to activate this feature.
Sponsored-by: On-Waves ehf
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The TA value rather relates to an MS and not to a single TBF. So all
TBFs share the same TA value. Currently the TA value is stored per
TBF and eventually copied from an old TBF to a new one. It is in
general only passed with an RACH request when the TLLI and thus the
MS is not yet known.
This commit adds a TA member to the GprsMs class and uses that one
when the TBF is associated to an MS object. Since the TBF is not
always associated with an MS object (after RACH or when it has been
replaced by another TBF), the TA value is still stored in each TBF
and that value is used as long as no MS object is being associated.
Sponsored-by: On-Waves ehf
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Currently the IMSI is stored in the TBFs. Since it directly refers to
an MS, it should rather be stored in an MS object.
This patch move the m_imsi field from gprs_rlcmac_tbf to GprsMs,
changes gprs_rlcmac_tbf::imsi() to get the IMSI from the associated
MS object, and adds getter and setter to GprsMs. Before changing the
IMSI of the associated MS object, assign_imsi() checks if there is
already another MS object with the same IMSI and eventually resets
the IMSI of that one. So using update_ms() and assign_imsi() ensures
that there are not two MS object entries is the storage with the
same TLLI or the same IMSI.
Ticket: #1674
Sponsored-by: On-Waves ehf
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Currently the m_tlli member in GprsMs is set by the constructor,
circumventing the TLLI confirmation mechanism.
This commit replaces the get_or_create_ms() method by a create_ms()
method which takes the TLLI and the direction (UL or DL) as
parameters to select either set_tlli() or confirm_tlli(). The MS
object is instantiated with TLLI = 0, and therefore GprsMs::tlli() is
extended to return the DL TLLI if both of the other TLLI are not set.
Note that create_ms() will not check whether an MS object with a
matching TLLI is already stored in the list, so it should only be
called after a corresponding get_ms() in general.
Sponsored-by: On-Waves ehf
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According to the specification (GSM 04.08/24.008, 4.7.1.5) after a
new P-TMSI has been assigned, the old P-TMSI must be kept basically
until it has been used by both sides. Since the TLLI will be derived
from the P-TMSI, the old TLLI must also be kept until the new TLLI
has been used by both MS and SGSN.
This commit modifies the TLLI handling of GprsMs accordingly.
set_tlli() is only used with TLLIs derived from MS messages,
confirm_tlli() is used with TLLIs derived from messages received from
the SGSN. tlli() returns the value set by the MS. check_tlli()
matches each of the TLLI used by either MS or SGSN as well as the old
TLLI until it has been confirmed.
Sponsored-by: On-Waves ehf
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Currently the MS objects are contained in the TBF objects only. To
allow for an extended life time after the TBF objects have been freed
and to find them based on TLLI, a container for the MS objects is
needed.
This commit adds the container class and also adds the corresponding
m_list member to GprsMs. Further integration into the PCU code is not
yet done.
Ticket: #1674
Sponsored-by: On-Waves ehf
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Currently only TBF objects are used to handle the data flow between
the MS and the SGSN. MS specific data (e.g. pending LLC frames, TLLI)
is copied between successive TBFs. If all TBFs (uplink and downlink)
are idle for some time, all information about the MS is discarded in
the PCU. This makes the implementation of some features more
difficult, e.g. proper TLLI and timing advance handling,
connection based CS selection, and proper management of multiple TBF.
This commit adds the GprsMs class that is intended to hold
information directly related to the MS and to keep references to the
active TBFs.
The class is not yet integrated with the other PCU code. A GprsMs
object container and MS specific fields (TA, CS) will be added in
later commits.
Note that calling detach_tbf() can possibly delete the MS object
depending on the callback implementation.
Ticket: #1674
Sponsored-by: On-Waves ehf
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