What is backing_length, reported_length ?

Question

void tvb_set_subset  
(   tvbuff_t *  tvb,    
    tvbuff_t *  backing,  
    const gint  backing_offset,  
    const gint  backing_length,  
    const gint  reported_length  
)

What is backing_length, reported_length here ?

Please help.

Accepted Answer

This function makes tvb a subset of backing. It creates a window upon the backing tvb as it were. The boundaries of that window are given by backing_offset and backing_length. The reported_length is the length as optionally reported by a lower layer protocol. It may be that during capture only the first part of a frame is captured, whereby the data in a protocol header can indicate what the true length of the frame, or packet on that protocol layer would have been. Then, if you dissect your protocol, you can discern why you run out of data, either because it is not in the frame (which is a protocol violation), or it may have been there, but was not captured (which is not a protocol violation, just a limitation of the capture).