osmocom-net-gprs May 2017

osmocom-net-gprs@lists.osmocom.org

8 participants
4 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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[PATCH] net: fix potential null pointer dereference
by Gustavo A. R. Silva 26 May '17

26 May '17

Add null check to avoid a potential null pointer dereference. Addresses-Coverity-ID: 1408831 Signed-off-by: Gustavo A. R. Silva <garsilva(a)embeddedor.com> --- drivers/net/gtp.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/net/gtp.c b/drivers/net/gtp.c index 4fea1b3..7b652bb 100644 --- a/drivers/net/gtp.c +++ b/drivers/net/gtp.c @@ -873,7 +873,7 @@ static struct gtp_dev *gtp_find_dev(struct net *src_net, struct nlattr *nla[]) /* Check if there's an existing gtpX device to configure */ dev = dev_get_by_index_rcu(net, nla_get_u32(nla[GTPA_LINK])); - if (dev->netdev_ops == &gtp_netdev_ops) + if (dev && dev->netdev_ops == &gtp_netdev_ops) gtp = netdev_priv(dev); put_net(net); -- 2.5.0

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Removing FCS from SNDCP packages
by Holger Freyther 17 May '17

17 May '17

Hi, I see that while adding decompression support dexter has fixed a bug in the sndcp code. Before the GTP-U frame would include the LLC FCS and now we do this: npdu_len = (msg->data + msg->len) - npdu - 3; What I wonder (and the commit message didn't say is) was the fragment part handled as well. The calculation is: /* make sure to subtract length of SNDCP header from 'len' */ rc = defrag_enqueue(sne, suh->seg_nr, data, len - (data - hdr)); and len is passed in from the TLV struct in gprs_llc_rcvmsg. I think the fragmented case is working okay. Shall we try to unify the length calculation to rely on the local "len" variable instead of checking msg->data+msg->len? cheers holger

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kernel-to-kernel gtp implementation
by fırat sönmez 05 May '17

05 May '17

Hi, I am currently working in a project where I was asked to implement a GTP tunnel from client to company servers. I have read through osmocom pages and tried to implement the simple network structure. I have seen from Basic testing of openGGSN page: " test GTP-U interoperability of the kernel with at least one other implementation, not just kernel-to-kernel (which currently is not supported in the kernel, as it only implements the GGSN/P-GW role) " I would not like to implement openGGSN but just linux-kernel-gtp-u implementation between two kernels. To achieve kernel-to-kernel implementation, I found sgsn patch on the internet: https://patchwork.ozlabs.org/patch/739408/ and there is already a kernel-gtp-U in osmocom. So, my basic network structure is below. [image: Satır içi resim 2] I would like make a tunnel between sgsn and ggsn. I have used libgtpnl tools to create link and then tunnel. I have added a default gateway GTP interface to route table on sgsn side, but the packets cannot reach ggsn side. Is there any detailed explanation for a simple bidirectional tunnel setup. If so, it would be so nice to know about. Thank you for all your efforts, Fırat

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osmocom-net-gprs May 2017