problem with fragment_add_seq_next

edit

A pcap file have 5 packet with the following parameters. these packets must be reassembled and formed two 2 different messages.

message 1 = packet 1 + packet 2 + packet 3(first_part_of_packet 3);

message 2 = packet 3(second_part_of_packet 3) + packet 4 + packet 5;

packet 1: id =1; start_flag =1; end_flag = 0; cont_flag = 0;

packet 2: id =1; start_flag =0; end_flag = 0; cont_flag = 1;

packet 3: first part of packet 3 : id =1; start_flag =0; end_flag = 1; cont_flag = 0;

packet 3: second part of packet 3 : id =1; start_flag =1; end_flag = 0; cont_flag = 0;

packet 4: id =1; start_flag =0; end_flag = 0; cont_flag = 1;

packet 5: id =1; start_flag =0; end_flag = 1; cont_flag = 0;

result:

message 1 = packet 1 + packet 2 + packet 3(first_part_of_packet 3);

message 2 = packet 4 + packet 5;

how can I fix this problem.

static int
desegment_fnc( tvbuff_t *tvb, packet_info *pinfo, proto_tree *parent_tree, void* data _U_ ,guint8 start_flag ,guint8 end_flag  ,guint8 cont_flag, guint8 reassembly_id)
{
...
...

fragment_head *head = NULL;
head = fragment_add_seq_next(&myproto_reassembly_table, tvb, offset ,pinfo, reassembly_id, tvb_captured_length(tvb), moregrag);
...
...

    return tvb_captured_length(tvb);
}


static int
dissect_myproto( tvbuff_t *tvb, packet_info *pinfo, proto_tree *parent_tree, void* data _U_ )
{



if (cond1)
{
 ... 
 ...
 tvbuff_t *next_tvb = tvb_new_subset_remaining(tvb, offset);
 ...
 ...
 start_flag =1;end_flag = 0; cont_flag = 0;
 desegment_fnc(next_tvb, pinfo ,tree, id, start_flag ,end_flag , cont_flag, id);
}

else if (cond2)
{
 ... 
 ...
 tvbuff_t *next_tvb = tvb_new_subset_remaining(tvb, offset);
 ...
 ...
 start_flag =0; end_flag = 0; cont_flag = 1;
  desegment_fnc(next_tvb, pinfo ,tree, id, start_flag ,end_flag , cont_flag, id);

}

else if (cond3) // packet 3
{
 ... 
 ...
 if(cond3_subcond) // first part of packet 3
 {
    // first part of packet 3
    tvbuff_t *next_tvb = tvb_new_subset_remaining(tvb, offset); // tvb fot first part of packet 3
    // process and extract info from next_tvb
    ...
    ...
    start_flag =0; end_flag = 1; cont_flag = 0;
     desegment_fnc(next_tvb, pinfo ,tree, id, start_flag ,end_flag , cont_flag, id);
 }
 else
 {
     // second part of packet 3
     ...
     ...
     tvbuff_t *next_tvb = tvb_new_subset_remaining(tvb, offset); // tvb fot second part of packet 3
     //  process and extract info from next_tvb
    ...
    ...
    start_flag =1; end_flag = 0; cont_flag = 0;
     desegment_fnc(next_tvb, pinfo ,tree, id, start_flag ,end_flag , cont_flag, id);
 }
}



    return tvb_captured_length(tvb);

}