October 2011 - OpenBSC - lists.osmocom.org

GPRS - local and foreign TLLIs
by Luca Melette 04 Feb '26

04 Feb '26

Hello everybody, after setting up a nanoBTS with OpenBSC/SGSN/GGSN, I had some troubles trying to connect my smartphone to the GPRS cell. Investigating the BTS-to-SGSN traffic, I saw that the frames sent by the SGSN were all marked with the same N(U) value (at LLC layer), the value was 0. With some debug, I found that the there was a mismatch in the TLLI storage, used to keep the status of attached terminals. The mentioned code is contained in gprs_llc.c, involving LL Entity functions and gprs_llc_tx_ui(). /* look-up or create the LL Entity for this (TLLI, SAPI) tuple */ lle = lle_by_tlli_sapi(msgb_tlli(msg), sapi); if (!lle) { struct gprs_llc_llme *llme; LOGP(DLLC, LOGL_ERROR, "LLC TX: unknown TLLI 0x%08x, " "creating LLME on the fly\n", msgb_tlli(msg)); llme = llme_alloc(msgb_tlli(msg)); lle = &llme->lle[sapi]; } The TX function uses the previously received TLLI to lookup for the LLE. The lle_by_tlli_sapi() performs the search, but preliminary it applies a foreign2local TLLI conversion to ensure to have a local one. Since no valid entry for the searched TLLI is found, a new one is created. And the problem is here. The new entry has the foreign TLLI. Next time the lookup fails again, and a new entry is created. This way, the counter N(U) is always reset, and the mobile do not recognize the message sequence and no attach is possible. My question is about foreign and local TLLIs. I patched the lookup, avoiding the conversion, so that the LLE is found and everything works fine... but... What is the sense of the conversion? Should the TLLI be always stored as a local one? Can this problem be solved with another foreign2local while allocating new entries? Actually, my problem has been solved with that workaround. But I'm curious to know what is the right way. Hope somebody can answer :) Thanks. Cheers, LM

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Re: Help with sccp library
by mosbah abdelkader 07 Jul '25

07 Jul '25

> I don't understand. This callback will be called with data you need to write > to the network. In case of MTP Level3 you will need to wrap that around the > msgb you got. I means: is the interaction with mtp3 layer implemented (is sending sccp data by mtp3 implemented by the library?)? Also, what about the reception of data from mtp3 layer. is that implemented in the sccp lib. I am asking these questions because I see the code of mtp3 in the lib but no significant call is present in the sccp part of the lib. Thank you for your help.

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Several questions
by jason mercury 06 Dec '12

06 Dec '12

I have some questions: 1) When I start bsc_hack bsc_init.c first establishes OML link and initializes the bts then it establishes RSL link and bts starts broadcasting. However, it takes so much time to start the bts. Instead of this I want to do the following: it establishes OML link at the beginning and only once, then when i want to start broadcasting it establishes just the RSL link and bts will start faster since i don't have to wait for OML link. What should be done for this? 2) If i send one or two word messages from telnet interface it is okay. But if i send a longer message the phone could't receive the end of the message correctly(last words may be incomplete). Did any one encounter with this problem? What is wrong with me? 3) Could I send SMS in which extension of the sender is text not integer. For example, i want to send an information SMS that this is a test network. For this purpose i want to send an SMS from 'OpenBSC'. I set the extension of the first subscriber in database as text and tried to send the SMS but SMS wasn't delivered. What should i do? 4) Can i add SMS externally to SMS table of database? Thanks. Jason

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LCR + Asterisk + NanoBTS: Strange Voice Behaviour "Dropping incompatible voice frame on lcr/1"
by Luca Bongiorni 08 Nov '11

08 Nov '11

Hi all, i compiled and configured all (mISDN, lcr, asterisk, etc...), unfortunately, when i try to place a call from the softphone to the MS, i can ear only the voice originated from the laptop to the MS and not viceversa. I'm using it on an Ubuntu 10.4, Asterisk 1.6.2.5 and the others sources from "last git". Configurations: - extension.conf: http://pastebin.com/mHH46HbQ - sip.conf: http://pastebin.com/SkPN3z6q - gsm.conf: http://pastebin.com/C1Eckdgh - interface.conf: http://pastebin.com/ctGapa1F - options.conf: http://pastebin.com/6xhgL0P1 - routing.conf: http://pastebin.com/TVNvwTEB Logs: - osmo-nitb's log: http://pastebin.com/X10B5NjE - lcr's log: http://pastebin.com/uLY9VAiB - Asterisk's log: http://pastebin.com/8qzw6aMn As you can see from Asterisk, there is a mismatch: "NOTICE[2315]: channel.c:2960 __ast_read: Dropping incompatible voice frame on lcr/1 of format alaw since our native format has changed to 0x0 (nothing) " I tried to set alaw / ulaw on the configurations, to change efr, fr and amr, but it didn't change nothing. Ideas or hints for further investigations are welcome. Regards, Luca

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[RFC] MNCC introduce a hello packet to include a version number
by Holger Hans Peter Freyther 01 Nov '11

01 Nov '11

Hi Jolly, all, I spent some time figuring out why LCR and OpenBSC wouldn't want to work with each other. The reason was the addition of an element to the MNCC structure. I propose to send a hello packet down the MNCC socket and leave it to the client to decide if the version is acceptable. I will need to move the mncc header to libosmocore as osmocomBB is currently using a copy of the OpenBSC header. comments holger

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OpenBSC implementation problem
by Marek Świąder 28 Oct '11

28 Oct '11

Dear Sir or Madam, We are students from Poznan University of Technology in Poland.We want to develop our GUI enhancement for OpenBSC project.It's about adding and deleting users registered in network. We have already implemented adding logged users, but we couldn't make this part of program, which is responsible for deleting users when they have already logged out. Could you give some advice, where to find appropriate place in the source code in OpenBSC. Thanks in advance. Best regards Marek Świąder

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Looking for a CSN.1 library
by Alexander Chemeris 27 Oct '11

27 Oct '11

Hi all, Does anyone know a good C/C++ library for CSN.1 bitstream reading/writing? We're working on a GPRS implementation for OpenBTS and we don't want to code all those RLC/MAC messages by hands when we can do this automatically. Right now we think that the easiest way is to re-purpose csn1 "library" from Wireshark - adopt it to OpenBTS bitstream operations and add support for writing to bitstream. Then we can even re-use those RLC/MAC messages already converted to macros' for Wireshark's rlcmac dissector. But we would appreciate if someone points us to a better way of doing this. -- Regards, Alexander Chemeris.

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how to know GPRS channel coding
by John Wu 27 Oct '11

27 Oct '11

Hi all, I want to know how to know GPRS channel coding. GPRS using PDCH, both MAC/RLC data block and MAC/RLC control block is transmitted on PDCH, although there is PACCH, PTCH, PTCCH and so on it still PDCH. then the MAC/RLC control block is coded with cs-1 channel coding scheme and MAC/RLC data block may be coded with other channel coding scheme. so when received a burst how to know what kind of MAC/RLC block it belong to and which channel coding scheme it used? Thanks!

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Way to invoke multiple imsi msisdn in sgnsemu
by anish achenkunju 21 Oct '11

21 Oct '11

Hi All, Wondering if there is a way to create pdp request for multple imsi or msisdn. Currently there is an option to emulate more than one pdp context, can we do the same for different imsi's or msisdn via sgsnemu as an input to sgsnemu.conf file? Thank you in advance. Anish

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[PATCH] mncc: Introduce a hello packet that is sent to the client.
by Holger Hans Peter Freyther 21 Oct '11

21 Oct '11

Send a hello packet down to the client with the version number of the MNCC interface. The hello structure might be extended to include the endianes, size of each structure, etc. --- openbsc/include/openbsc/mncc.h | 8 ++++++++ openbsc/src/libmsc/mncc_sock.c | 24 ++++++++++++++++++++++++ 2 files changed, 32 insertions(+), 0 deletions(-) diff --git a/openbsc/include/openbsc/mncc.h b/openbsc/include/openbsc/mncc.h index 8c59fe2..9153d65 100644 --- a/openbsc/include/openbsc/mncc.h +++ b/openbsc/include/openbsc/mncc.h @@ -96,6 +96,8 @@ struct gsm_call { #define GSM_TCHF_FRAME 0x0300 #define GSM_TCHF_FRAME_EFR 0x0301 +#define MNCC_SOCKET_HELLO 0x0400 + #define GSM_MAX_FACILITY 128 #define GSM_MAX_SSVERSION 128 #define GSM_MAX_USERUSER 128 @@ -158,6 +160,12 @@ struct gsm_data_frame { unsigned char data[0]; }; +#define MNCC_SOCK_VERSION 1 +struct gsm_mncc_hello { + uint32_t msg_type; + uint32_t version; +}; + char *get_mncc_name(int value); void mncc_set_cause(struct gsm_mncc *data, int loc, int val); void cc_tx_to_mncc(struct gsm_network *net, struct msgb *msg); diff --git a/openbsc/src/libmsc/mncc_sock.c b/openbsc/src/libmsc/mncc_sock.c index d8caf07..b9ebdb0 100644 --- a/openbsc/src/libmsc/mncc_sock.c +++ b/openbsc/src/libmsc/mncc_sock.c @@ -213,6 +213,29 @@ static int mncc_sock_cb(struct osmo_fd *bfd, unsigned int flags) return rc; } +/** + * Send a version indication to the remote. + */ +static void queue_hello(struct mncc_sock_state *mncc) +{ + struct gsm_mncc_hello *hello; + struct msgb *msg; + + msg = msgb_alloc(512, "mncc hello"); + if (!msg) { + LOGP(DMNCC, LOGL_ERROR, "Failed to allocate hello.\n"); + mncc_sock_close(mncc); + return; + } + + hello = (struct gsm_mncc_hello *) msgb_put(msg, sizeof(*hello)); + hello->msg_type = MNCC_SOCKET_HELLO; + hello->version = MNCC_SOCK_VERSION; + + msgb_enqueue(&mncc->net->upqueue, msg); + mncc->conn_bfd.when |= BSC_FD_WRITE; +} + /* accept a new connection */ static int mncc_sock_accept(struct osmo_fd *bfd, unsigned int flags) { @@ -253,6 +276,7 @@ static int mncc_sock_accept(struct osmo_fd *bfd, unsigned int flags) LOGP(DMNCC, LOGL_NOTICE, "MNCC Socket has connection with external " "call control application\n"); + queue_hello(state); return 0; } -- 1.7.5.4 --------------020402070302030203020301 Content-Type: text/x-patch; name="0001-gsm-Verify-the-MNCC_VERSION-of-the-BSC-MS-and-close-.patch" Content-Transfer-Encoding: 7bit Content-Disposition: attachment; filename*0="0001-gsm-Verify-the-MNCC_VERSION-of-the-BSC-MS-and-close-.pa"; filename*1="tch"

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