2.2.1.6.1 FID Generation

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File IDs (FIDs) are generated on CIFS servers. The generation of FIDs MUST satisfy the following constraints:

  • The FID MUST be a 16-bit opaque value.

  • The FID MUST be unique within a specified client/server SMB connection.

  • The FID MUST remain valid for the lifetime of the SMB connection on which the open request is performed, or until the client sends a request to the server to close the FID.

  • Once a FID has been closed, the value can be reused for another create or open request.

  • The value 0xFFFF MUST NOT be used as a valid FID. All other possible values for FID, including zero (0x0000) are valid. The value 0xFFFF is used to specify all FIDs or no FID, depending upon the context in which it is used.