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Cisco Bug: CSCvu75387 - "sshd_child_handler" memory depletion when transfer files through SFTP using WinSCP

Last Modified

Oct 06, 2020

Products (9)

  • Cisco ASR 9000 Series Aggregation Services Routers
  • Cisco ASR 9910 Router
  • Cisco IOS XR Software
  • Cisco ASR 9922 Router
  • Cisco ASR 9010 Router
  • Cisco ASR 9904 Router
  • Cisco ASR 9006 Router
  • Cisco ASR 9001 Router
  • Cisco ASR 9912 Router

Known Affected Releases

6.4.1

Description (partial)

Symptom:
Process "sshd_child_handler" allocates all the available memory per thread, after all the memory is allocated, the process is restarted to release the memory.

It was also seen that after the thread "sshd_child_handler" was restarted, the process "pipe" and "sftp_server" never release the CPU cycles.

Everytime the sshd_child_handler is restarted, WinSCP restarts the transfer creating a new sftp_server and sshd_child_handler, however the old threads are not released:

RP/0/RSP1/CPU0:ASR9k#sho process cpu | e 0%      0%       0%  
Thu Jun 18 19:11:46.831 CDT
 
CPU utilization for one minute: 51%; five minutes: 51%; fifteen minutes: 51%
 
PID    1Min    5Min    15Min Process
1       10%     10%      10% kernel
6619151  27%     27%      27% pipe
6672755   2%      2%       2% sftp_server
7750005   2%      2%       2% sftp_server
8581496   2%      2%       2% sftp_server
8790388   2%      2%       2% sftp_server
9249146   2%      2%       2% sftp_server
9273724   2%      2%       2% sftp_server

Conditions:
Transfer a large file (like a new IOS XR Image) through SFTP using WinSCP with default options.

The issue is not seen when using FileZilla or Linux SFTP client.
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