Wireshark-dev: [Wireshark-dev] issue: SMB2: The value of "Fixed Part Length" seems wrong

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From: Xuan k <kxuanobj@xxxxxxxxx>
Date: Tue, 24 Sep 2019 19:05:50 +0800
Hi everyone,

I found a issue about SMB2 protocol. The wireshark gives a wrong value on "Fixed Part Length" field. 

This is a Close Request message:
Close Request (0x06)
  StructureSize: 0x0018
    0000 0000 0001 100. = Fixed Part Length: 12
    .... .... .... ...0 = Dynamic Part: False
  Close Flags: 0x0000
  GUID handle File: Templates

But the "Fixed Part Length" should be 24 in this message, not 12.

It seems that the problem is caused by misusing the bit mask of struct header_field_info. 
The source line epan/dissectors/packet-smb2.c:10984 use a mask 0xFFFE to filter out the field. 
10982                 { &hf_smb2_buffer_code_len,
10983                         { "Fixed Part Length", "smb2.buffer_code.length", FT_UINT16, BASE_DEC,
10984                         NULL, 0xFFFE, "Length of fixed portion of PDU", HFILL }
10985                 },

But in function `proto_tree_set_uint` (epan/proto.c:5281), it shifts the numberic, and cause the numberic been divided by 2.

hope this issue will be resolved soon.

Thanks,
Zhai Zhaoxuan