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4317 discussions

Call waiting and MNCC_RTP_CREATE
by Mychaela Falconia 14 Oct '22

14 Oct '22

Hello Osmocom CNI community, I am writing my own software that talks MNCC to OsmoMSC instead of using osmo-sip-connector, and I am seeing perplexing behaviour with call waiting. Normally when I send an MT call toward GSM with MNCC_SETUP_REQ, the response from OsmoMSC consists of MNCC_CALL_CONF_IND (when the called phone confirms the call), followed by MNCC_RTP_CREATE (when OsmoMSC assigns the call), and finally followed by MNCC_ALERT_IND when the called phone starts alerting. Likewise on MO calls I get an MNCC_RTP_CREATE message on the MNCC interface when the call is assigned, typically in response to MNCC_CALL_PROC_REQ. But now consider a call waiting scenario: call 1 is already in progress (fully connected, parties talking), and there is a second incoming call. I send a new MNCC_SETUP_REQ to OpenMSC for call 2, with a new callref, the phone receives it and starts making call-waiting beeps. The response on the MNCC socket for call 2 is that I get MNCC_CALL_CONF_IND followed by MNCC_ALERT_IND (and then MNCC_SETUP_CNF if the target phone puts call 1 on hold and answers call 2) - but there is no MNCC_RTP_CREATE! I can see how MNCC_RTP_CREATE is sent by OsmoMSC when the call has been assigned and there is a TCH cross-connected through OsmoMGW, and I can see how the call assignment step will naturally be omitted in the call waiting scenario when TCH is already there for call 1. But the call gateway (be it osmo-sip-connector or an independent reimplementation) feeding MT call 2 to MNCC has to have some way of obtaining RTP connection information for this call without having to know how to associate it with another previous call, and if it doesn't get MNCC_RTP_CREATE, how would it get this vital info? This is one of those "how does it work for everyone else?" moments - while I am certainly unique in writing my own MNCC software instead of running osmo-sip-connector, surely o-s-c also needs to receive MNCC_RTP_CREATE with RTP info from OsmoMSC in order to successfully connect call 2... And given that someone implemented call hold and retrieve operations in o-s-c, I reason that someone must be using the call waiting feature and it must be working for them - but how? One thing which o-s-c does differently from my sw is that o-s-c sends an empty MNCC_RTP_CREATE (the "command" version of this packet) to OsmoMSC in response to MNCC_CALL_CONF_IND, which my sw doesn't do at the moment. But I looked in the OsmoMSC code, and I don't see any difference: the function that handles MNCC_RTP_CREATE command (tch_rtp_create()) simply calls msc_a_try_call_assignment(trans), and the exact same call is made in the gsm48_cc_rx_call_conf() function that sends MNCC_CALL_CONF_IND. So I don't see any code path that can result in call 2 receiving MNCC_RTP_CREATE from OsmoMSC in the call waiting scenario when TCH is already there from call 1. So, how does the call waiting feature work for others in the community, and what am I missing? I am running the tagged release from 2021-11. M~

3 10

osmo-gsm-tester: Issue with osmo-gsm-tester-runner Jenkins job
by Callum Snowden 11 Oct '22

11 Oct '22

Hi all, We're trying to setup osmo-gsm-tester on bare metal and are currently experiencing issues with the Jenkins job 'osmo-gsm-tester-runner'. All of our test machines are running Ubuntu Server 20.04 and have been setup following the latest available manual from https://downloads.osmocom.org/docs/latest/osmo-gsm-tester-manual.pdf. We've trying to use the '4g_srsLTE' example from https://github.com/osmocom/osmo-gsm-tester/tree/master/doc/examples/4g_srsL… but when trying to run the 'ping' test the following error is returned in the Jenkins console output: " 14:07:52.867022 run mk-remote-dir(pid=2480): ERR: Terminated: ERROR {rc=1} [trial-21↪4g:srsenb-rftype@soapy↪ping.py:9↪ping.py↪srsepc_10.100.100.113↪host-jenkins@10.100.100.113↪mk-remote-dir(pid=2480)] 14:07:53.015620 run mk-remote-dir(pid=2480): stdout: | (launched: 2022-09-23_14:07:51.598612) | mkdir: cannot create directory ‘/osmo-gsm-tester-srsepc’: Permission denied " It appears that osmo-gsm-tester is trying to create the directory 'osmo-gsm-tester-srsepc' under root, which is not permitted as the Jenkins user the script runs has does not have permissions. Additionally, it looks like this path is hard-coded in the Python module https://github.com/osmocom/osmo-gsm-tester/blob/master/src/osmo_gsm_tester/… and also the same applies for srsENB https://github.com/osmocom/osmo-gsm-tester/blob/master/src/osmo_gsm_tester/… Is this the intended behaviour? Or have we missed out steps during our bare-metal setup process? I've double-checked that the main unit can SSH into the slave unit without a password so that's not the issue causing "permission denied". Best regards, Callum.

3 11

osmo-gsm-tester: Issue with osmo-gsm-tester-runner Jenkins job
by Callum Snowden 26 Sep '22

26 Sep '22

1 0

osmo-gsm-tester: Issue with osmo-gsm-tester-runner Jenkins job
by Callum Snowden 26 Sep '22

26 Sep '22

1 0

git infrastructure
by Neels Hofmeyr 26 Sep '22

26 Sep '22

I guess it's a bit late, but do we really need categories on gitea? The simple world I would have expected: git clone https://gitea.osmocom.org/libosmo-pfcp git clone https://gitea.osmocom.org/osmo-upf The world we live in: git clone https://gitea.osmocom.org/celullar_infarsturcure/libosmo-pfcp git clone https://gitea.osmocom.org/osmocom/osmo-upf git clone https://gerrit.osmocom.org/libosmo-dsp and works: git clone git://git.osmocom.org/osmo-upf fails: git clone https://git.osmocom.org/osmo-upf works: git clone https://git.osmocom.org/libosmo-pfcp While I'm at it: do we have a designated primary git place for Osmocom? De facto the answer seems to be: gerrit, except when it's not on gerrit. Because of the above issues, currently there is a wave of patches rolling out which edit build scripts and READMEs to change git URLs -- it feels wrong that this is necessary. It seems the topic needs some clarification, and maybe it is still possible to simplify the git structures? - remove the layer of categories from gitea? - move gitea/cellular-infrastraucute/* to gitea/osmocom/* ? - point git.osmocom.org at gitea.osmocom.org/osmocom/ ? (cgit.osmocom.org still works) - keep cgit as the primary git place, gitea as users' playgrounds? (not sure if possible or good ideas) ~N

3 5

transceiver aborted
by msfu 24 Sep '22

24 Sep '22

hi there, i ran into an error with ./transceiver in osmocom-bb if i write osmocom/osmocom-bb/src/host/layer23/src/transceiver # sudo ./transceiver -a 47 -2 -r 99 the cli returns with 47 41 1 Aborted what am i doing wrong? i hope you can help me out. have a nice day msfu

1 0

Ideas/proposals for Osmocom project submissions to NLnet or prototypefund?
by Harald Welte 20 Sep '22

20 Sep '22

Dear Osmocom community, during the past years, we've been applying for (and often receiving) grants for the development of certain parts of the Osmocom project. There are two organizations (NLnet foundation and the German prototype fund) where the next call for proposals ends in 10 days from now. So if any of you has some ideas about Osmocom related work that you would want to see implemented and for which you can argue that it fits the scope of the related funds, please feel free to bring them up here. For NLnet, the scope should fit either * https://nlnet.nl/entrust/ * https://nlnet.nl/useroperated/ For prototype fund, the scope should fit https://prototypefund.de/jetzt-bewerben-fuer-runde-13/ - specifically I think it is likely that we could fit a number of "our" topics in https://prototypefund.de/softwareinfrastruktur/ which explicitly lists implementation of communication protocols. Given that I have plenty of experience with both funds, I'd be willing to work on a concrete proposal and submit it before the deadline on Sept 30 / Oct 1. In terms of "who would do the actual work": With NLnet projects we can involve freelancers across Europe, with prototype fund probably only in Germany. In the worst case, if you propose some idea but have no time to work on such a project yourself, or you are not eligible due to the restriction to EU/DE, sysmocom could carry out the implementation. Let me know if anyone of you has some ideas as to what kind of osmocom related topics might be suitable candidates. Thanks, Harald -- - Harald Welte <laforge(a)osmocom.org> http://laforge.gnumonks.org/ ============================================================================ "Privacy in residential applications is a desirable marketing option." (ETSI EN 300 175-7 Ch. A6)

1 0

mscgen
by Neels Hofmeyr 14 Sep '22

14 Sep '22

RFC about mscgen mscgen is our tool of choice to generate ladder diagrams from the "msc" text input format. We use it in user manuals and on our redmine wiki, and there are also various .msc files in doc/ subdirs, as assistance for development. I've written a lot of ladder diagrams, for documentation as well as figuring out how to implement things. I've developed a love/hate relationship, and recently I found a bug in mscgen. Things have come up that I'd like your opinion on: * ladder_to_msc.py Writing .msc files by hand quickly started to annoy me: - Having to write '[label="..."]' all the time. - Multiline labels (e.g. '(note)' block) require "foo\nbar\nbaz" - input symbols for arrows are weird / non-intuitive - cannot use 'msc' as entity, weirdly conflicts with the outer 'msc { ... }', which is annoying for GSM diagrams featuring an MSC. So quite some while ago I wrote a python script that reads my personal favorite format in which i enjoy writing ladder diagrams, and outputs plain .msc file format. I put it in libosmocore/contrib/ on a branch, have been using it ever since, but i never submitted it for merging, because it seemed like a personal preference thing, not worth complicating the doc tool chain for. So far I was, if at all, committing only the resulting .msc to git. But that creates a situation where only I have the *original* source in .ladder format, so (hypothetically) collaborating on ladder diagrams becomes convoluted. Here is an example of my favorite ".ladder" format: ------ {hscale=1} upf = User Plane function cpf = Control Plane function upf <- cpf PFCP Association Setup Request CP function Node Id, features upf -> cpf PFCP Association Setup Response UP function Node Id, features upf <> cpf associated upf () cpf start Heartbeat checking ... ------ The equivalent .msc produced by ladder_to_msc.py: ------ msc { hscale="1"; upf[label="User Plane function"],cpf[label="Control Plane function"]; upf <= cpf [label="PFCP Association Setup Request\nCP function Node Id, features"]; upf => cpf [label="PFCP Association Setup Response\nUP function Node Id, features"]; upf abox cpf [label="associated"]; upf rbox cpf [label="start Heartbeat checking"]; ...; ------ I'd like to hear some opinions, if you have any, on whether anyone else likes my new ladder format, and how to deal with .ladder source files. Would it make sense to merge ladder_to_msc.py to libosmocore, install it via 'make install', and add the original .ladder files as well as Makefile rules to convert .ladder to .msc to .png where ever i wrote .ladder diagrams? * mscgen bitrot is likely Recently I've found a segfault in mscgen. I found a fix and tried to submit it. That's when I discovered that: - the original project on code.google.com is dead and gone - the mail addresses of the original author result in bounces - random people put mscgen's trunk on github, exported from google code, no activity is apparent I did reach the Debian maintainer of mscgen by mail. He doesn't have any way to contact the original author, either. It seems there could be a patch in the Debian package, at best. I wonder if it would make sense to officially create an mscgen "fork" on Osmocom, in an effort to save the tool from bitrot and extinction, and offer our mscgen as the new upstream for debian's mscgen packaging. I do have a number of things i'd like mscgen to be able to do, like left-adjust text in "note" blocks or improve the resolution of produced PNG images; I might also implement support for my .ladder format directly in mscgen. I am vague on what my opinion is between the advantages and disadvantages, and it's all only semi important. I just know that I always end up writing .ladder instead of .msc, and that we will always need ladder diagrams. Do you have any opinions on these things? Thanks! pointers: ladder_to_msc.py: libosmocore branch neels/ladder https://cgit.osmocom.org/libosmocore/commit/?h=neels/ladder&id=073ad74435ec… My most recent ladder chart: https://cgit.osmocom.org/osmo-bsc/commit/?h=neels/codec&id=01f370c1b365305f… -- - Neels Hofmeyr <nhofmeyr(a)sysmocom.de> http://www.sysmocom.de/ ======================================================================= * sysmocom - systems for mobile communications GmbH * Alt-Moabit 93 * 10559 Berlin, Germany * Sitz / Registered office: Berlin, HRB 134158 B * Geschäftsführer / Managing Directors: Harald Welte

2 1

Osmocom GUI support
by Ahnaf Tahmid 02 Sep '22

02 Sep '22

Dear OpenBSC team, I am Ahnaf Tahmid Chowdhury, currently building Osmocom graphical user interface. I have created a subscriber page where one can add/remove/update subscriber. The repo is available at: https://github.com/ahnaf-tahmid-chowdhury/osmo-gui Please let me know your thoughts about the application. Thank you

4 6

two distinct SCCP sources?
by Neels Hofmeyr 28 Aug '22

28 Aug '22

I'm confused by what is happening in the pcap linked below: According to wireshark, the SCCP message seems to come from *both* PC=4 and PC=185. A column configured as sccp.calling.pc shows Point-Code 4. A column configured as "Source Address" shows Point-Code 185. Is it even possible that the in-band Calling Address differs from whatever wireshark detects as the SCCP Source Addres? Can anyone explain where the 185 is coming from? apparently not from sccp.calling.pc. The pcap and a screenshot showing the two point-codes and the column config are here: http://people.osmocom.org/neels/Eew7we0I/ Context: The original RESET message (not part of the pcap) was sent to called.pc=4, but I have SCCP routing set up to forward PC=4 to the MSC that sees itself as PC=185. I am expecting to see a RESET-ACK sent from PC=185. IIUC The 4 should have evaporated when the MSC parsed the RESET message. But apparently when answering, it takes the "called.pc" and puts it in the response as "calling.pc" (4 is nowhere in the MSC's confguration, it MUST have taken the "4" from the received SCCP message). So what I am seeing in wireshark is eerily correct: it is the MSC that has "185" in its cfg as local address sending the ACK, and it is responding to a request that was originally sent to "4", and which osmo-stp routed to "185". The response shows calling.pc=4. But how can wireshark know that it was really "185" sending, when no such information is in the SCCP layer of that message? What am I missing? if anyone knows, thanks in advance... ~N

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