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Cisco Bug: CSCuq15440 - Assertion egtpc_validate_evt.c:3157 egtpc_validate_fwd_reloc_rsp_evt()

Last Modified

Dec 24, 2016

Products (1)

  • Cisco ASR 5000 Series

Known Affected Releases

16.2.0.56410 17.0.0.56029

Description (partial)

Symptom:
The foll crash will be seen

Assertion failure at sess/egtp/egtpc/egtpc_validate_evt.c:3157
  Function: egtpc_validate_fwd_reloc_rsp_evt()
  Expression: egtpc_evt->handle.tun_handle != ((void *)0)
  Proclet: sessmgr (f=87000,i=102)
  Process: card=6 cpu=0 arch=X pid=6919 cpu=~4% argv0=sessmgr
  Crash time: 2014-Jul-30+05:21:16 UTC
  Recent errno: 11 Resource temporarily unavailable
  Stack (131071@0xfffb9000, probably truncated):
    [ffffe430/X] __kernel_vsyscall() sp=0xfffb9408
    [0acd554f/X] sn_assert() sp=0xfffb9448
    [079bb238/X] egtpc_validate_fwd_reloc_rsp_evt() sp=0xfffc5328
    [07a50faa/X] egtpc_validate_event() sp=0xfffc5768
    [07a548ee/X] egtpc_handle_user_sap_event() sp=0xfffc5d78
    [07e91a14/X] mme_app_send_egtp_failed_mme_fwd_reloc_req() sp=0xfffd23d8
    [07e9a957/X] mme_s1ho_gen_to_4g_procedure_clear() sp=0xfffd2428
    [07ea4d34/X] mme_end_procedure() sp=0xfffd24b8
    [07f2f5c8/X] mme_app_destroy_ue_ctxt() sp=0xfffd4a98
    [07f7b895/X] mme_app_egtp_validate_s10s3_fwd_reloc_ind() sp=0xfffd4d48

Conditions:
1. S3 Forward Relocation Request received from an SGSN.  MME sends S1AP Handover Request to the target eNodeB.
2. While this is pending, an S3 path failure occurs with the SGSN, triggering an EGTPC Abort_Proc_Cmd to the MME.  This sets a zero-second timer to finish cleaning up the UE context, due to lack of reentrancy with EGTPC duirng a path failure.
3. Before the timer fires, another S3 Forward Relocation Request is received for the same UE.  The MME attempts to abort the previous call and send a failed Forward Relocation Response back to the SGSN, but this triggers an assertion because the EGTPC state for the first call no longer exists due to step 2.

There is a timing window that must be hit between the notification of the path failure in step 2 and a zero-second timer firing, during which the second Forward Relocation Request is received. Else crash wont be seen.
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