Wireshark · Wireshark-users: Re: [Wireshark-users] Parse CFM Type Test signal (TST) without CRC

[Pascal Quantin <pascal.quantin@xxxxxxxxx>]

Le 16 juin 2015 4:14 PM, "Jiunrong" <jiunrong@xxxxxxxxx> a écrit :
>
> Hi advancer:
>
> I found [Malformed Packet: CFM] when I receive CFM Type Test signal (TST) without CRC32, but it is ok with CRC32.
>
>  
>
> I try to find what happen, so I download the source code.
>
> I am new guide in wireshark, if I make mistake, please don’t laugh me.
>
>  
>
> in file: epan/dissectors/packet-cfm.c
>
> Due to
>
>                 tlv_data_offset += (cfm_tlv_length-5);
>
> I think next line maybe need -1
>
>                 tlv_data_offset += cfm_tlv_length;  //maybe it need -1
>
>  
>
>  
>
> if (cfm_tlv_length > 0) {
>
>         switch (tlv_tst_test_pattern_type) {
>
>         case 0:
>
>         case 2:
>
>                 proto_tree_add_item(cfm_tlv_tree, hf_tlv_tst_test_pattern,
>
>                                 tvb, tlv_data_offset, cfm_tlv_length-1, ENC_NA);
>
>                 tlv_data_offset += cfm_tlv_length;  //maybe it need -1
>
>                 break;
>
>         case 1:
>
>         case 3:
>
>                 proto_tree_add_item(cfm_tlv_tree, hf_tlv_tst_test_pattern,
>
>                         tvb, tlv_data_offset, cfm_tlv_length-5, ENC_NA);
>
>                 tlv_data_offset += (cfm_tlv_length-5);
>
>                 proto_tree_add_item(cfm_tlv_tree, hf_tlv_tst_CRC32,
>
>                                 tvb, tlv_data_offset, 4, ENC_NA);
>
>                 tlv_data_offset += 4;
>
>                 break;
>
>         }
>
> }      
>
> From JustinKu
>

Hi JustinKu,

Can I convince you to fill a bug on http://bugs.wireshark.org with your pcap file triggering the malformed message attached?

Best regards,
Pascal.