11863 SMB2 CREATE should validate impersonation level
While we don't use the impersonation level we should be ensuring that the client hasn't passed a bogus value for it:
"If the ImpersonationLevel in the request is not one of the values specified in section 2.2.13, the server SHOULD fail the request with STATUS_BAD_IMPERSONATION_LEVEL."
This impacts the following WPTS test cases:
CreateCloseTestCaseS640

CreateCloseTestCaseS733

CreateCloseTestCaseS179
11864 SMB2 CREATE should reject absolute paths
The SMB2 documentation says we should reject CREATE requests with absolute paths but we don't currently do that:
"If the file name length is greater than zero and the first character is a path separator character, the server MUST fail the request with STATUS_INVALID_PARAMETER."
This impacts the following WPTS test cases:
CreateCloseTestCaseS249

CreateCloseTestCaseS122

CreateCloseTestCaseS443

CreateCloseTestCaseS418

CreateCloseTestCaseS406

CreateCloseTestCaseS379

CreateCloseTestCaseS367

CreateCloseTestCaseS346

CreateCloseTestCaseS331

CreateCloseTestCaseS285

CreateCloseTestCaseS273
11865 SMB2 CREATE should check MxAc create context size
The SMB2 server should fail with STATUS_INVALID_PARAMETER if the size of a MxAc create context is not large enough to hold the optional timestamp value. This is something the WPTS checks for by issuing a bogus CREATE request with a MxAc create context with a size of 4 bytes (the spec says it MUST be either 0 or 8 bytes long):
"The Data in the Buffer field of the SMB2_CREATE_CONTEXT MUST either contain the following structure or be empty (0 bytes in length)." 

https://docs.microsoft.com/en-us/openspecs/windows_protocols/ms-smb2/5ea40835-5d40-4e85-977d-13cd745d3af8
This impacts the following WPTS test case:
InvalidCreateRequestStructureSize

Prior to applying the fix the above test cases fail.  With the fix applied they now pass.