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Cisco Bug: CSCvu76373 - DHCP Snoop Memory Leak When Receiving High Amounts Of CFS Traffic

Last Modified

Jul 22, 2020

Products (55)

  • Cisco Nexus 9000 Series Switches
  • Cisco Nexus 3548-X Switch
  • Cisco Nexus 9516 Switch
  • Cisco Nexus 3548 Switch
  • Cisco Nexus 92160YC-X Switch
  • Cisco Nexus 93108TC-FX Switch
  • Cisco Nexus 9396PX Switch
  • Cisco Nexus 3064 Switch
  • Cisco Nexus 31108TC-V Switch
  • Cisco Nexus 3548-XL Switch
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Known Affected Releases

7.0(3)I7(6)

Description (partial)

Symptom:
+ dhcp_snoop process crashes due to memory leak
+ The following output is displayed in syslog once the process has crashed:

==========================================
'show logging log'

2020 Mar 31 04:15:33.393 [hostname] %SISF-3-INTERNAL: Internal error, Cannot allocate packet
2020 Mar 31 04:15:37.945 [hostname] last message repeated 26 times
2020 Mar 31 04:15:38.314 [hostname] %SISF-3-INTERNAL: Internal error, Cannot allocate packet
2020 Mar 31 04:15:53.411 [hostname] last message repeated 104 times
2020 Mar 31 04:15:53.958 [hostname] %SISF-3-INTERNAL: Internal error, Cannot allocate packet
2020 Mar 31 04:16:15.972 [hostname] last message repeated 138 times
2020 Mar 31 04:16:16.563 [hostname] %SISF-3-INTERNAL: Internal error, Cannot allocate packet
==========================================

+ The crash may eventually result in a core of the process

==========================================
'show cores'

VDC  Module  Instance  Process-name     PID       Date(Year-Month-Day Time)
---  ------  --------  ---------------  --------  -------------------------
1    28      1         dhcp_snoop       32191     2020-04-08 06:32:02
==========================================

Conditions:
+ Nexus 9K running software version 7.0(3)I7(6)
+ Receiving high amounts of CFS traffic
+ While the issue is occuring you will slowly see the memory consumed by the 'dhcp_snoop' process increment until the "MemUsed" hits the "MemLimit".  At which point you will see the symptoms above.

==========================================
'show processes mem | i snoop|Process|--'

PID    MemAlloc  MemLimit    MemUsed     StackBase/Ptr      Process
-----  --------  ----------  ----------  -----------------  ----------------
30264  54337536  1750758374  1044357120  ffafb810/ffaf905c  dhcp_snoop
==========================================

+ When running the "show system internal dhcp mem-stats detail" command over time, the "DHCP_MEM_query_ref" subprocess will be the highest incrementing
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