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CIFS disconnect while copying data when encryption is enabled and NULL sessions are created

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ontap-9
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Applies to

  • ONTAP 9
  • Microsoft Defender
  • SMB Encryption

Issue

  • Network Error: There is a problem accessing <path>. Make sure that you're connected to the network and try again

CIFS disconnect while copying data when encryption is enabled and NULL sessions are created.png

  • Every time a Windows client, with Microsoft Defender enabled, sends an encrypted packet, ONTAP resets the TCP stream
  • No. Time Source Destination Protocol Length tcp.srcport tcp.dstport tcp.stream smb2.acct smb2.domain smb2.host ntlmssp.auth.domain ntlmssp.auth.username Info
    575 ...  <ip-1> <ip-2>      SMB2     186    57663         445       0          -         -           -         -                   -                     Session Setup Request, NTLMSSP_NEGOTIATE
    588 ...  <ip-1> <ip-2>      SMB2     281    57663         445       0          -         -           <domain>  NULL                NULL                  Session Setup Request, NTLMSSP_AUTH, User: \
    589 ...  <ip-2> <ip-1>      SMB2     130      445       57663       0          -         -           <domain>  -                   -                     Session Setup Response
    593 ...  <ip-2> <ip-1>      TCP       54      445       57663       0          -         -           -         -                   -                     445 → 57663 [RST, ACK] Seq=1198768 Ack=55095 Win=259 Len=0
    595 ...  <ip-2> <ip-1>      TCP       54      445       57663       0          -         -           -         -                   -                     445 → 57663 [RST] Seq=1198768 Win=0 Len=0
    597 ...  <ip-2> <ip-1>      TCP       54      445       57663       0          -         -           -         -                   -                     445 → 57663 [RST] Seq=1198768 Win=0 Len=0
    anonymous (null) login, no user (User: \)
    • anonymous (null) login, no user (User: \), so as you can see the CIFS/SMB server sends a TCP [RST] to the CIFS/SMB client, see frames: 593,595,597

 

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