RHEL7.6: NFSv3 client hangs after 5 minute idle timer drops the TCP connection and a subsequent TCP 3-way handhake fails due to duplicate SYN or unexpected RST from the NFS client

Solution Verified - Updated -

Issue

  • On an NFSv3 client, a NFS share that was previously active goes idle for 5 minutes and the NFS client initiates a close of the TCP connection. After some time, a process accesses the NFS share and the NFS client attempts a 3-way TCP handshake to the NFS server. During the 3-way handshake, the NFS client issues either a duplicate SYN packet for the first part of the 3-way handshake, or issues an RST to the response to the second part (SYN,ACK from NFS server). As a result, the NFS client is unable to complete the TCP 3-way handshake, and the NFS share hangs.

Environment

  • NFS client
    • Red Hat Enterprise Linux 7.6
    • seen on kernel-3.10.0-957.el7 and earlier than kernel-3.10.0-957.5.1.el7
  • NFS server

    • seen with Solaris 10 NFS server
    • seen with Windows Server 2008
  • NFSv3

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