multiple EXCHANGE_ID diring a mount.

"Mkrtchyan, Tigran" <tigran.mkrtchyan@xxxxxxx> · Wed, 15 Apr 2020 11:39:16 +0200 (CEST)

Dear NFS (client) developers,

Today I notice, that during mount nfs client sends two  EXCHANGE_ID operations:

    4 0.000380551 131.169.185.213 → 131.169.191.144 NFS V4 NULL Call
    6 0.001052087 131.169.191.144 → 131.169.185.213 NFS V4 NULL Reply (Call In 4)
    8 0.001501687 131.169.185.213 → 131.169.191.144 NFS V4 Call EXCHANGE_ID
    9 0.002105356 131.169.191.144 → 131.169.185.213 NFS V4 Reply (Call In 8) EXCHANGE_ID
   11 0.002489297 131.169.185.213 → 131.169.191.144 NFS V4 Call EXCHANGE_ID <----------------------------------- A second one
   12 0.003422630 131.169.191.144 → 131.169.185.213 NFS V4 Reply (Call In 11) EXCHANGE_ID
   14 0.003569542 131.169.185.213 → 131.169.191.144 NFS V4 Call CREATE_SESSION
   17 0.004701642 131.169.191.144 → 131.169.185.213 NFS V4 Reply (Call In 14) CREATE_SESSION
   18 0.004822235 131.169.185.213 → 131.169.191.144 NFS V4 Call RECLAIM_COMPLETE
   19 0.005317324 131.169.191.144 → 131.169.185.213 NFS V4 Reply (Call In 18) RECLAIM_COMPLETE
   20 0.005489908 131.169.185.213 → 131.169.191.144 NFS V4 Call SECINFO_NO_NAME
   21 0.006648815 131.169.191.144 → 131.169.185.213 NFS V4 Reply (Call In 20) SECINFO_NO_NAME

I observe this with kernel 5.6 and 5.5. On opposite, the older kernels, like in RHEL7 don't do this

Older kernel (3.10.0-1062.12.1.el7.x86_64)

$ tshark -r ex_id_el7.pcap -Y nfs
  8 0.006731652 131.169.240.106 -> 131.169.240.145 NFS 336 V4 Call EXCHANGE_ID
  9 0.008812988 131.169.240.145 -> 131.169.240.106 NFS 224 V4 Reply (Call In 8) EXCHANGE_ID
 10 0.009127689 131.169.240.106 -> 131.169.240.145 NFS 292 V4 Call CREATE_SESSION
 13 0.012583411 131.169.240.145 -> 131.169.240.106 NFS 196 V4 Reply (Call In 10) CREATE_SESSION
 14 0.012805867 131.169.240.106 -> 131.169.240.145 NFS 208 V4 Call RECLAIM_COMPLETE
 15 0.013716790 131.169.240.145 -> 131.169.240.106 NFS 160 V4 Reply (Call In 14) RECLAIM_COMPLETE
 16 0.013981538 131.169.240.106 -> 131.169.240.145 NFS 216 V4 Call SECINFO_NO_NAME
 17 0.019359329 131.169.240.145 -> 131.169.240.106 NFS 176 V4 Reply (Call In 16) SECINFO_NO_NAME

This is of course not a big problem, but can point to an unintended change or error. The capture
file available at:

https://sas.desy.de/index.php/s/3sRA9WD5BEpZH7z

Regards,
   Tigran.