pinfo->fd->flags.visited for wireshark c dissector

["Ran Bao" <worksev () gmail com>]

Hi 

I am currently implementing a dissector plugin for a DMR conventional and
trunked protocols. Three layers of protocols were involved. Messages was
send to a specific UDP port on server. 

 

UDP port -> Company specified protocol -> DMR Layer 2 Protocols -> DMR Layer
3 Protocols.

 

Raw messages are processed or reassembled and delivered to higher layer sub
dissectors for further analysis. Some DMRL2 PDUs are required to be
reassembled into a large message. Due to the limitation of DMRL2 PDUs, many
message bursts do not contain fragmentation number or stop bit. The DMRL2
dissector heavily relies on the receiving order of fragments. I used
fragment_add_seq_next() function to add each fragments into hash tables. 

 

However, I noticed that the value of pinfo->fd->flags.visited was
initialized with 0, so that each fragments are only added once, when opening
*.pcapng file with filter applied. If there is no filter specified before
opening *.pcapng file, either using Open or Open from recent,  the
pinfo->fd->flags.visited for each PDUs were set to 1 initially. Hence no
fragment was reassembled. 

 

It turned out that the user have to provide some filter before capturing or
reading from file in order to assemble these PDUs. Is that the feature that
Wireshark was designed? Is there any method to reset visited flag for each
PDUs? 

 

Cheers

Ran Bao

___________________________________________________________________________
Sent via:    Wireshark-dev mailing list <wireshark-dev () wireshark org>
Archives:    https://www.wireshark.org/lists/wireshark-dev
Unsubscribe: https://wireshark.org/mailman/options/wireshark-dev
             mailto:wireshark-dev-request () wireshark org?subject=unsubscribe