osmocom-net-gprs February 2018

osmocom-net-gprs@lists.osmocom.org

7 participants
8 discussions

RFC: unit tests for kernel GTP module
by Harald Welte 01 Jan '26

01 Jan '26

Dear GTP-interested folks, I would love to somehow get towards some degree of unit testing (or even "continuous integration") for teh kernel GTP code. We currently have the original code in the kernel, we had some recent small fixes and now are getting more patches into place. With relatively few active users out there (and probably none of them in production yet), it's particularly easy to introduce regressions while working on the code. Also, having tested new code even against a test set with limited covrage could help to get more confidence in new patches and thus get them merged sooner. Using tools like sgsnemu of OpenGGSN and the command line tools included in libgtpnl, it should be possibel to cook up some scripts for testing. Even the most basic set of tests would be an improvement over what we have now. One could also think about pcap replay to test with hand-crafted or real-world packets from other GTP implementations. As much as I'd like to put something like this into place myself, I don't think I will be able to work much on this in the near future. The GTP module at this point is a pure hobby and contrary to some years ago while I started it, I don't have any contract work in the GTP area at this point, so other projects currently unfortunately get more attention. So in case somebody among the GTP-interested parties (Travelping, OAI, ...) would want to do something in terms of testing, I'd be more than happy if somebody would step ahead. Otherwise it's all just vapourware going to end up on my ever-growing TODO list :/ Also, if netdev folks have some ideas/pointers about possible frameworks/tools for this kind of testing [it must exist for at least some other kernel networking code?]: Please let me know. I'd be interested to have a look if there's something that can be used as a basis (starting network namespaces, sending/transmitting packets, test case startup/teardown, ...) My "old school" approach would have been to start one or multiple user-mode-linux kernels (those that are to be tested), and then have scripts that set up a gtp socket and gtp tunnels via the libgtp command line tools, and throw packets at that. But I'm sure there must be quite powerful frameworks for that kind of testing in the 21st century? How do other tunneling implementations handle this? 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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Data Rate of EGPRS is Too Low
by XINKE ZHANG 28 Jun '18

28 Jun '18

Hi all, I have set up the EGPRS network using software bundles (osmo-nitb + osmo-bts-trx + osmo-trx + osmo-pcu + osmo-sgsn + openggsn) based on the USRP B210 platform. Now the cell phone can connect to the EGPRS network, but the network is not stable and the data rate is too low (only about 8kbs). Is this data rate correct? If not, could you pls send me some working config files? Thank you. Best Regards, Xinke

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Interfering with the GTP-u Kernel module
by Thomas Boros 16 Feb '18

16 Feb '18

Hello, I would like to implement a command line tool, which will be able to open / close , read / write to gtp tunnels. I was able to install the libgtpnl library, but due to lack of documentation I have no idea where to start. Is there some sort of documentation available for this library? I need to be able to create and delete tunnels without the GTP-C communication, so just basic command line tool like create-gtp-tunnel + arguments like IPs, version and teid. The GTP-U tunnels must be kernel based. I have the latest kernel with the gtp kernel module loaded. Any help is appreciated. Thank you, Tomas

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Problem when building OsmoSGSN
by XINKE ZHANG 16 Feb '18

16 Feb '18

Hi all, I built OsmoSGSN with the these following instructions. <build instructions> git clone git://git.osmocom.org/osmo-sgsn cd osmo-sgsn autoreconf -fi ./configure --enable-iu make -j5 make check make install sudo ldconfig <build instructions> And no error came out during building process, but no “osmo-sgsn” executable was found. Pls help me. Thank you in advance. Best Regards, Xinke

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sgsnemu: no outgoing GTP-U in "createif" mode
by Viktor Tsymbalyuk 09 Feb '18

09 Feb '18

Hello, I tried to run sgsnemu in "createif" mode - transfer traffic via tun interface. tun interface created and routing too. But there are no outgoing GTP-U from test machine. (in my scenario sgsnemu on separated server). From gdb it looks, that in cb_tun_ind function ipm->pdp is 0x0, as result gtp_data_req(gsn, ipm->pdp, pack, len); not running. After changes like below, it's start working. Does I correctly understood internal logic? diff --git a/sgsnemu/sgsnemu.c b/sgsnemu/sgsnemu.c index 630733b..cf4aa44 100644 --- a/sgsnemu/sgsnemu.c +++ b/sgsnemu/sgsnemu.c @@ -1462,7 +1462,7 @@ static int create_pdp_conf(struct pdp_t *pdp, void *cbp, int cause) free(forwarding); } - ipset((struct iphash_t *)pdp->peer, &addr); + ipset(iph, &addr); state = 2; /* Connected */ If need more test details, please let me know. -- Viktor

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GPRS trafic in PCU - type BVC-UNBLOCK unknown // Protocol error - unspecified
by Osmocom Mailing List 06 Feb '18

06 Feb '18

Hi, I'm trying to run GPRS in my network. So far I get flooded with the bellow trafic in the PCU and the GGNS doesn't appear to receive any traffic. <000c> gprs_bssgp_bss.c:294 BSSGP (BVCI=2) Tx BVC-RESET CAUSE=O&M intervention <000c> gprs_bssgp.c:551 BSSGP BVCI=0 Rx BVC STATUS, cause=Protocol error - unspecified <000c> gprs_bssgp_pcu.cpp:348 Rx BSSGP BVCI=0 (SIGN) PDU type BVC-UNBLOCK unknown <000c> gprs_bssgp_util.c:238 BSSGP BVCI=0 Tx STATUS, cause=Protocol error - unspecified <000c> gprs_bssgp_pcu.cpp:298 Rx BSSGP BVCI=0 (SIGN) BVC_RESET_ACK <000c> gprs_bssgp_pcu.cpp:835 Sending unblock on BVCI 2 <000c> gprs_bssgp_bss.c:274 BSSGP (BVCI=2) Tx BVC-BLOCK <000c> gprs_bssgp.c:289 Cell 1-1-1-0 CI 0 on BVCI 2 Thanks, Filipe Laíns <https://github.com/FFY00> Sent via Migadu.com, world's easiest email hosting

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Fwd: icmp encapsulation
by fırat sönmez 02 Feb '18

02 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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osmocom-net-gprs February 2018