[Jeff Morriss <jeff.morriss.ws@xxxxxxxxx>]

damker wrote:
> Hi experts：
>       Attachment is a normal IP packet，the last "00 00 00" is m3ua padding, but treated as malformed packet.

I think the packet is malformed.

If you disable the BSSMAP dissector, the M3UA padding will correctly be 
displayed.  (It doesn't in this case because BSSMAP is throwing an 
exception.)

The last octet in the BSSMAP portion indicates that "T-GSM 400 Band 
Information present" is true which means there should be another couple 
of octets of (400-Band) info, but it's not there (thus leading to the 
exception/malformed indication).