osmocom-net-gprs

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507 discussions

Fwd: icmp encapsulation
by fırat sönmez 01 Feb '18

01 Feb '18

---------- Forwarded message ---------- From: fırat sönmez <firatssonmez(a)gmail.com> Date: 2018-02-01 15:51 GMT+03:00 Subject: Re: icmp encapsulation To: Pau Espin Pedrol <pespin(a)sysmocom.de> Hi Pau, Thank you for your response. You are right, I should have told the configuration in more detail. However, you came to the point already. I am talking about the second case where there is NAT. There is a slight difference though. After the NAT two IP (IP1 and IP2) will be IPnat, but the NAT maps the IP1 and IP2 to the port range. Since, there is no port in ICMP, both IP1 and IP2 will be go to uplink as IPg and but on the return there must be problem for NAT machine to traverse the two different paths from IPnat to IP1 and IPnat to IP2. I looked into the ICMP header and observed the packets have different identifiers. So, NAT machine must be using the identifies to reverse the packets. Anyways, in my case the *IP1=IP2* (In my experimental architecture, the GGSN will not be assigning distinct IP for each host. Instead, GGSN will assign 1 IP address for 32 hosts (seems like NAT). My configuration is probably out of standard architectures, but I need to understand how would gtp handle matching these two pdp contexts. I have tried this configuration, pinging from two different host with same IP and it was successful! Two packets coming from the server to the GGSN will be *[src:IPs | dst:IP1]* and *[src:IPs | dst:IP2]* IP1=IP2, but two packets have different icmp identifier. And pdp contexts are still resolved successfully. so a big HOW in my mind? Fırat 2018-02-01 13:46 GMT+03:00 Pau Espin Pedrol <pespin(a)sysmocom.de>: > Hi firat, > > I didn't understand fully the configuration you are describing. Something > like this? > > Host1 --SGSN1--\GGSN--Server > Host2 --SGSN2--/ > > Where Host1 has been assigned IP1 and Host2 has been assigned IP2, both > assigned by GGSN where IP1 != IP2. Let's assume the server IP is IPs and > the GGSN public uplink (non-GTP) IP is IPg. > > As far as I understand, it works as follow: > > - Case without NAT between GGSN and Server: > Host1 sends ICMP packet with saddr=IP1 daddr=IPs, which gets encapsulated > through GTP and GGSN decapsulates it. Same for Host2 but in this case the > packet will have saddr=IP2. As there's no NAT (eg. host clients are > assigned a public IP), the server receives 2 ICMP packets with different > saddr, and when answering back using the original saddr now as daddr. As > GGSN keeps track of the saddr assigned to each pdp context, when it > receives a packet from the uplink (non-GTP side), it matches the daddr of > the packet against the saddr of the active pdp ctx to find to which pdp ctx > should forward the packet. > > - Case with NAT between GGSN and Server: > Almost the same but with extra steps done by the NAT. When the GGSN sends > the packet saddr=IP1 daddr=IPs to the server, the NAT changes > saddr=IP1->IPg. It does the same for saddr=IP2, but the NAT keeps track of > the binding. When the response is received from the server, the NAT > converts back IPg->IP1 and GGSN can again track the pdp ctx as described in > the previous case. > > -- > - Pau Espin Pedrol <pespin(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 > * Geschaeftsfuehrer / Managing Director: Harald Welte >

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icmp encapsulation
by fırat sönmez 01 Feb '18

01 Feb '18

Hi, I would like to ask&know how the GGSN holds and finds pdp contexts for icmp packets that have same source and destination address on the downlink? For example, if there are two hosts having same IP address behind two different network pinging same destination address and they are encapsulated at SGSN and then one GGSN receives both and saves the packet, decapsulates and sends to the destination. On the downlink destination responds to the two ping packets (they are different because they have different identifier in icmp packet), but then how does GGSN finds the pdp contexts again to encapsulate these packets and send back to the two SGSNs? The pdp context doesnt include thse icmp identifiers. There is no sockets either since icmp doesnt have sockets. On the downlink, when there are two icmp packets recieved by GGSN, there is only icmp identfier that distinguish each other, but this identifier is not in the pdp context. Would someone help me figure out this? Thank you all

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sgsnemu ignoring Request accepted
by Viktor Tsymbalyuk 26 Jan '18

26 Jan '18

Hello, I continue to play with sgsnemu, and found that it stopped for some reason after "Request accepted". Does sgsnemu working? At my mind problem inside `create_pdp_conf` function . After small changes, I start to see icmp inside gtp tunnel in trace. Please check attachments with console output, patch and pcap. May be I has wrong understanding. -- Viktor

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sgsnemu: why --listen and --remote in one network?
by Viktor Tsymbalyuk 19 Jan '18

19 Jan '18

Hello, I'm querying why sgsnemu shoul work in a same network with ggsn? What the reason for such limitation? -- Viktor

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Osmocom Year 2017 Review
by Harald Welte 01 Jan '18

01 Jan '18

Dear all, I've written up a "short" review of what I perceive as the most important events in the Osmocom Cellular Infrastructure projects in 2017. See http://osmocom.org/news/84 for all details, or below for a raw copy+paste: h1. Osmocom Review 2017 This is a review of the most significant changes and events in the Osmocom Cellular Infrastructure projects in 2017 h2. January 2017 * announce of first ever public [[OsmoCon:]] conference in April * osmo-bts ** Add Abis OML failure event reporting ** fix memory leaks in osmo-bts-{sysmo,lc15} at every channel activation * openbsc/osmo-bsc ** support multiple UARFCNs in SI2quater * osmo-hlr ** add test suite for 2G and 3G authentication ** fix UMTS AKA re-sync h2. February 2017 * weekly manual testing with related weekly test reports to mailing list * "heads-up about the (lack of a )future of osmo-nitb":http://lists.osmocom.org/pipermail/openbsc/2017-February/010300.html * "heads-up about libosmo-sccp SIGTRAN work":http://lists.osmocom.org/pipermail/openbsc/2017-February/010274.html * "sysmo-usim-tool":http://lists.osmocom.org/pipermail/openbsc/2017-February/010317.html * libosmo-abis ** unix domain socket support (for Ericsson L2TP) * osmo-bts ** fix AMR HR DTX FSM logic ** fix SACCH sending fo system information with enum value > 7 ** osmo-bts-trx: fix RXGAIN and POWER parameters on second TRX ** fix TCH/H interleaving table bit position ** sysmoBTS 1020/1100: slow power ramp-up on TRX enable * osmo-sgsn ** fix PDP context activation memory allocation bug ** integrate support for UMTS AKA * openggsn ** fix kernel-gtp tunnel creation/removal for GTPv1 ** release 0.93 h3. March 2017 * "cgit improvements":http://lists.osmocom.org/pipermail/openbsc/2017-March/010448.html (about page, change-ID hyperlinks, issue hyperlinks) * Add README.md files to all our repositories * libosmocore ** migrate gsm 05.03 coding from OsmoBTS to libosmocore ** fix SQN / SEQ handling in UMTS AKA ** 3GPP AoIP message encoding/decoding * libosmo-abis ** fix ever-increasing jitter buffer * libosmo-netif ** handle SCTP in in stream server ** doxygen documentation on stream an datagram modules * osmo-bts ** octphy: CBCH support ** include MS timing offset in RSL measurements * osmo-sgsn ** handle IMSIs with leading zeroes * osmo-bsc ** fix T3186 encoding in SI13 ** Improved Ericsson OM2000/RBS2000 support ** new ctrl2soap proxy in python * osmo-hlr ** add CTRL interface ** fix SQN/SEQ handling in UMTS AKA h3. April 2017 * "update of coding style for longer line lengths":http://lists.osmocom.org/pipermail/openbsc/2017-April/010502.html * [[osmo-dev-con:OsmoCon2017]] and [[osmo-dev-con:OsmoDevCon2017]] * libosmocore ** "control interface for osmo_fsm":http://lists.osmocom.org/pipermail/openbsc/2017-April/010542.html * libosmo-netif ** fix file descriptor leak in error paths ** work around linux kenrel SCTP bug with sender_dry_events ** RTP marker bit support * libosmo-sccp ** Add new [[libosmo-sigtran:]] library with SS7 AS/ASP Link/Linkset handling, M3UA support, new FSM based SCCP implementation ** Add [[osmo-stp:]] program * osmo-bts ** inform BSC of PCU disconnect ** fix measurement reporting period ** exclude idle channels from uplink measurement processing ** octphy: measurement reports h3. May 2017 * libosmocore ** fix embedded builds ** import and generalise 'sercomm' from osmocom-bb into libosmocore ** SSE optimized convolutional coder ** fix wrong GSM FR codec SID frame generation ** doxygen docs for libosmocoding * osmo-bsc ** TS 04.14 mobile station side loop control * osmo-bts ** consistently check all RSL and OML TLVs for minimum length value ** fix bit-order in every HR codec parameter (spec compliance) ** OML get/set attribute handling ** SI2quater support ** bypass radio link timeout for lab testing * osmo-bsc ** PCU socket support for BSC-colocated PCU for Ericsson RBS2000 ** reelase 1.0.1 * "M3UA and SUA testing as part of jenkins":http://lists.osmocom.org/pipermail/openbsc/2017-May/010698.html * "osmo-gsm-tester produces successful runs with NITB as well as new AoIP":http://lists.osmocom.org/pipermail/openbsc/2017-May/010760.html h3. June 2017 * libosmocore ** doxygen autobrief ** doxygen documentation for libosmogb * osmo-bts ** use CLOCK_MONOTONIC timer for GSM frame timer ** PDTCH loopback support h3. July 2017 * "Plan for openbsc.git split and code review":http://lists.osmocom.org/pipermail/openbsc/2017-July/010914.html * libosmocore ** PDP charging characteristics in GSUP ** PRBS sequence generators ** multicast IP related helper functions ** 'make release' target * libosmo-sccp ** SCCP address book * osmo-bts ** new virtual BTS @osmo-bts-virtual@ for testing without radio hardware ** don't send dummy UI frames on unused BCCH slots on TC=5 ** GSMTAP: don't log/send fill frames consisting of only padding * osmo-hlr ** change to default GSUP port 4222 h3. August 2017 * "Support for SMPP Delivery Receipt / GSM03.40 Status Report":http://lists.osmocom.org/pipermail/openbsc/2017-August/011023.html * "Jenkins now executing M3UA, SUA and GGSN testsuite":http://lists.osmocom.org/pipermail/openbsc/2017-August/011043.html * libosmocore ** fix crash in lapd_est_req() * libosmo-abis ** release 0.4.0 * osmo-bts ** osmo-bts-trx: fix MS power control loop ** release 0.6.0 ** support sending/removing SI13 to/from PCU * osmo-bsc ** indicate R99+ MSC in SI3 to enable UMTS AKA over GERAN * osmo-sgsn ** properly report GERAN/UTRAN mode in PDP CTX ACT REQ to GGSN * osmo-msc ** implement IuCS support ** split openbsc.git into osmo-bsc.git, osmo-msc.git and osmo-sgsn.git * openggsn ** Add IPv6 address pool and IPV6 user (inner) plane support ** release 0.94 h3. September 2017 * libosmocore.git ** "'show talloc-context' VTY introspection":http://lists.osmocom.org/pipermail/openbsc/2017-June/010771.html ** CTRL parsing unit tests ** unification of vty exit/end commands * osmo-hlr ** CTRL interface tests -- - Harald Welte <laforge(a)gnumonks.org> http://laforge.gnumonks.org/ ============================================================================ "Privacy in residential applications is a desirable marketing option." (ETSI EN 300 175-7 Ch. A6)

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OsmoDevCon 2018 schedule planning
by Harald Welte 06 Dec '17

06 Dec '17

Dear Osmocom Community, [please respect the Reply-To and post all follow-up discussion to this to openbsc(a)lists.osmocom.org, so we avoid having long threads cross-posted to several mailing lists.] Like every year in early December, it is time to discuss as schedule for OsmoDevCon in the upcoming year. Note: Ths is about OsmoDevCon, the more private meeting of developers, *NOT* about OsmoCon, the public conference. == When, Who, Where == I propose the following date for OsmoDevCon 2018: April 20 - April 23rd, 2018 * Who: Active developers/contributors of Osmocom projects (as usual) * Where: IN-Berlin, Berlin (as usual) Please let me know ASAP if that proposed date works for everyone who'd want to attend. We can still change it now, but I would want to nail down the date pretty soon. == Format == After the experiment of reducing from 4 to 3 days last year (due to OsmoCon), we will again go for *four days* in 2018. However, we should clearly divide the days in a way that e.g. "GSM/3G" topics are on two days, while SDR+Other topics are on the other days, so people not interested in some topics can skip one or two days, as needed. We could even divide it further like: * 1 day 3GPP RAN (osmo-bts, osmo-bsc, osmo-pcu, virt_phy, fake_trx, ...) * 1 day 3GPP CN (osmo-msc, osmo-hlr, osmo-sip-connector, nextepc, etc.) * 2 days misc Regards, and looking forward to meeting you [again] in 2018, Harald -- - Harald Welte <laforge(a)gnumonks.org> http://laforge.gnumonks.org/ ============================================================================ "Privacy in residential applications is a desirable marketing option." (ETSI EN 300 175-7 Ch. A6)

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Packets are not arrived at tunnel setup by libgtpnl
by congnt 24 Nov '17

24 Nov '17

Hi guys, I'm using libgtpnl tools (gtp-link, gtp-tunnel) to setup a tunnel in my local machines. I was able to setup gtp link to 2152 port as well as gtp tunnel. I have pre-recorded GTP packets with correct teid and IP address as well as chksum and port to send to 2152. However I can not see any packets in gtp link device when using tcpdump. By add some messages in gtp module, I notice that the function gtp1u_udp_encap_recv in gtp.c kernel file was never been called if I send packet with GTP headers. However, that function is called if I send normal UDP packet without GTP header. Note that I'm using Ubuntu 14.04 with kernel 4.8.0 lowlatency, the tunnel is on a VM created by Virtualbox using virtio network driver. Any suggestions on how to debug/solve this problem? Many thanks in advances. Best regards Cong.

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libgtpnl migrated to gerrit
by Harald Welte 12 Nov '17

12 Nov '17

Hi all, FYI: I migrated libgtpnl (the kernel-GTP netlink interface helper library used by OpenGGSN and OsmoGGSN) to gerrit earlier today. This means direct pushes to git.osmocom.org no longer work and you will have to submit modifications via gerrit, as we do for all our other major repositories. I've also set up a gerrit build verification job via jenkins-job-builder and added a corresponding contrib/jenkins.sh script to it. The buildhosts now need libmnl-dev as build dependency installed. I added this to our current debian8 + debian9 build slaves and the wiki documentation about them. In other news: libgtpnl is already part of the network:osmocom:nightly and network:osmocom:latest feeds for some weeks. I intend to test kernel GTP support in osmo-ggsn soon and then change the package builds to include kernel-gtp support via libgtpnl by default. Regards, Harald -- - Harald Welte <laforge(a)gnumonks.org> http://laforge.gnumonks.org/ ============================================================================ "Privacy in residential applications is a desirable marketing option." (ETSI EN 300 175-7 Ch. A6)

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Re: GPRS EXperiments
by Neels Hofmeyr 03 Nov '17

03 Nov '17

(BTW, for GPRS we use osmocom-net-gprs(a)lists.osmocom.org but admittedly, almost all osmocom communication is taking place on openbsc@) On Mon, Oct 30, 2017 at 12:12:03PM -0600, Keith wrote: > I've installed up to date versions of osmo-bts and osmo-pcu > on sysmobts 2050 hardware and it's working great! > Dynamic channels are really nice, with half rate TCH and AMR > working perfectly. Thanks for all that work! Good to hear that! > I configured pcodns1 in the ggsn to point to this DNS > server, AND I setup a port 53 redirect to catch quite a lot > of traffic from android that likes to just talk directly to > 8.8.8.8 anyway. Interesting, this sounds like it would make for a good wiki page on osmocom.org. > games. Such is the sad state of affairs on today's internet. > Fortunately, we have iptables and ip sets and we have AS > blocks assigned to certain bandwidth hungry corporations :-) So instead of compromising net neutrality by giving the rich more bandwidth, you do it by cutting the big ones out instead ;) > I have observed that if I initiate any data transfer from > the network side then the uplink is established. By the same > token, If I transfer a file from the network (http download > or some such), the same applies. The link stays active and > the IM chat session is very responsive alongside the file > transfer. Shortly after the file transfer completes, the > uplink is quiet again and the latency in the IM session > becomes a problem. It might be related to a basic problem we still have with data services: we don't cache anything. If a PDP context is still being established, we drop data transfers to the floor, instead of storing them and sending them through when the context is established. I'm personally not familiar with the details there, but that's my current understanding. So a first ping would get lost, a second one within a timeframe that still has the PDP context open will go through. I think the idea there is that generally, higher level data communication should attempt to resend, but in practice that often doesn't seem to work that well. Not sure how to configure the PDP context timeout, or whether we even can. Theoretically, if you had on your phone a regular ping running in the background ... it's ugly, but yea. Caching those first packets is quite complex, especially for SGSNs sitting on a small device like a sysmoBTS with limited memory. I guess something could be tried there, by limiting resources used for caching in intelligent ways... Someone would need to fund that, or go ahead and try. ~N

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Want to do paid work on Osmocom? sysmocom is hiring
by Harald Welte 31 Oct '17

31 Oct '17

Dear Osmocom community, I would like to point out that at sysmocom, we're currently (again) hiring [1]. If you happen to have an interest in open source cellular communications and are fluent in C language development, we would love to hear from you. sysmocom probably doesn't need any introduction here, but just in case: The company was founded by Holger Freyther and Harald Welte, two of the leading OpenBSC and Osmocom developers from the very early days of the project. Today we are responsible for by far the largest number of commits to the Osmocom GSM/3G infrastructure related git repositories. Among our current priorities are automatic testing for the GPRS PCU, generalization of the OsmoMGW media gateway, support for load-based hand-over, inter-BSC hand-over as well as various improvements on the lower layers of the GPRS protocol stack. We're very dedicated to the cause in furthering the capabilities of open source cellular infrastructure from 2G to 4G. We believe in working upstream, no open core or dual licensing. If you have an interest working with an enthusiastic, strong technical and dedicated team of Osmocom hackers, please don't hesitate to let me know, best by e-mail to jobs(a)sysmocom.de Thanks, Harald p.s.: I hope this kind of message is not disturbing to anyone. I think it is important to the Osmocom project to have more paid people working on the stack, so it is justified. The positions we are seeking to fill will work [almost exclusively] on Osmocom, so it's not a random job ad but in the very interest of Osmocom, and hence on-topic for this list. [1] https://www.sysmocom.de/jobs/ -- - Harald Welte <hwelte(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 * Geschaeftsfuehrer / Managing Director: Harald Welte

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