Nextepc died in some MT-Fallback

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Sukchan Lee acetcom at gmail.com
Sun Jul 21 13:59:44 UTC 2019


Today I've analyzed this problem. Luckily it was reproduced in simulator.

The bad news seems to be a problem with the asn1c library.
More than 9 protocol IE cannot be built from InitialContextSetupRequest.

So, I've added some workaround as below.

if CS Fallback then
  Add CS Fallback ProtofcolIE
  Add RegisteredLAI
ELSE if RadioCababiltiy
  Add RadioCapbability
endif

ELSE prevents InitialContextSetupRequest from creating more than 9 protocol
IEs.

See more information the following link:
https://github.com/open5gs/nextepc/commit/f19009c736875847f30d7ea010d1064c5810d644

Thanks a lot!

Best Regards,
    Sukchan



On Thu, Jul 18, 2019 at 5:55 AM Romeu Medeiros <medeiros at medeiros.eng.br>
wrote:

> Hello,
>
> In some situations the Nextepc is crashing when try the MT-CSFB.
>
> Here is the log:
>
> 07/17 17:48:53.270: [mme] WARNING: EMM_CAUSE : IMSI Unknown in HSS
> (mme-sm.c:339)
> 07/17 17:48:54.480: [mme] WARNING: ERROR DIAMETER Result Code(5001)
> (mme-fd-path.c:298)
> 07/17 17:48:54.480: [mme] WARNING: EMM_CAUSE : IMSI Unknown in HSS
> (mme-sm.c:339)
> 07/17 17:48:55.611: [s1ap] ERROR: Failed to encode S1AP-PDU[-1]
> (s1ap-encoder.c:41)
> 07/17 17:48:55.611: [mme] ERROR: s1ap_encode_pdu() failed
> (s1ap-build.c:555)
> 07/17 17:48:55.611: [mme] FATAL: s1ap_send_initial_context_setup_request:
> Assertion `rv == OGS_OK && s1apbuf' failed. (s1ap-path.c:252)
> File Logging: '//var/log/nextepc/mme.log'
> Configuration: '//etc/nextepc/mme.conf'
> 07/17 17:48:58.215: [mme] INFO: MME initialize...done (mme.c:28)
>
> NextEPC daemon v0.5.0.26-b642c
>
> 07/17 17:48:58.215: [gtp] INFO: gtp_server() [10.3.15.38]:2123
> (gtp-path.c:36)
> 07/17 17:48:58.215: [gtp] INFO: gtp_server()
> [2804:828:3:15:b010:37ff:fe46:4521]:2123 (gtp-path.c:36)
> 07/17 17:48:58.215: [gtp] INFO: gtp_server()
> [2804:828:3:208:48a0:1cff:fed9:b7c9]:2123 (gtp-path.c:36)
> 07/17 17:48:58.215: [gtp] INFO: gtp_connect() [127.0.0.2]:2123
> (gtp-path.c:61)
> 07/17 17:48:58.216: [mme] INFO: sgsap client() [127.0.0.1]:29118
> (sgsap-lkpath.c:47)
> 07/17 17:48:58.216: [mme] INFO: s1ap_server() [10.3.15.38]:36412
> (s1ap-lkpath.c:44)
> 07/17 17:48:58.217: [fd] INFO: CONNECTED TO 'hss.localdomain'
> (TCP,soc#14): (fd-logger.c:113)
> 07/17 17:48:58.802: [mme] INFO: eNB-S1 accepted[10.12.0.3]:36412 in
> s1_path module (s1ap-lkpath.c:70)
>
> In the attached file is the pcap from this moment, I will try to find what
> is happened.
>
> Thanks
>
> Romeu Medeiros
>
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