Wireshark-dev: [Wireshark-dev] Someone please help me on this Reassemly fragmentation
From: Raj sekar <[email protected]>
Date: Wed, 25 Feb 2015 17:07:48 +0800

i have a off-line capture file..

iam developing dissector for customised protocol

i have a old ethereal tool for the same protocol now iam developing in wireshark.

My message pdu got 3 different message types

  1. Beginning of message
  2. continuation of message
  3. end of message

in one Frame at a time it can receive any one of this message

when it End of message sequence comes i need to reassemble whole PDU

i have opened in ethereal tool and my output are like this
 
Frame Number    Message type pollflag NS (sequence Number) NR (SEquence ID)
   
283 Beginning of message 0 0 0
343 End of message  0 1 0  -> Reassembly done here
   
379 Beginning of message  0 2 1
414 Continuation of message 0 3 1
416 Continuation of message 0 4 1
417 End of Message 1 5 1  -> Reassembly done here
   
536 Beginning of message 0 6 2
541 End of meassage 0 7 2  -> Reassembly done here


I have used my code structure like this


guint32 rem_length;
guint8 iflag,pf,stype,flag_sel,num_sel,i,sflag;  //
guint32 pdu_len;
guint8 save_fragmented;
gboolean more_frags = FALSE;
gboolean need_frag = FALSE;
const *data = ""
//tvbuff_t *try_tvb = NULL;
//proto_item *frag_tree_item;
tvbuff_t  *rass_tvb = NULL;
tvbuff_t  *mns_tvb = NULL;
guint32 msg_seqid;
guint32 mns_seqid = 0;
guint32 mns_seqnum = 0;
fragment_head *frag_msg = NULL;
gboolean reassembled = FALSE;
//guint32  reassembled_in = 0;
tvbuff_t * res_tvb = NULL;
fragment_head * frag_head = NULL; 
proto_tree *ptree = NULL;
ptree = proto_tree_get_parent(tree);

        
         pf = (tvb_get_guint8(next_tvb, offset_payload) & 0x40) >>6 ; // Bit 7 pf
         mns_seqnum = (tvb_get_ntohs(next_tvb, offset_payload) & 0x3ff00000) >>20; // 10 Bits are ns
         offset_payload +=1;
         mns_seqid = (tvb_get_ntohs(next_tvb, offset_payload) & 0x0ffc0000) >>18; // 10 bits are nr
         offset_payload +=1;
         stype = (tvb_get_guint8(next_tvb, offset_payload) & 0x03) ; // 2 bits LSB are Stype
         offset_payload -=2;
         
         FT_BCnPDU_item = proto_tree_add_text(tree, next_tvb, offset_payload, bctsdu_length, "BCnPDU (Formatted) : Information, I flag = 0x%02x, Pf = 0x%02x, Ns = 0x%02x, Nr = 0x%02x ", iflag,pf,mns_seqnum,mns_seqid );
         FT_BCnPDU_tree = proto_item_add_subtree(FT_BCnPDU_item, ett_FT_BCnPDU);
         proto_tree_add_text(FT_BCnPDU_tree, next_tvb, offset_payload, 1, " bctsdu_length: %d", bctsdu_length);
    
         proto_tree_add_text(FT_BCnPDU_tree, next_tvb, offset_payload, 1, "I flag : 0x%02x (%s)", iflag,val_to_str(iflag,true_false_vals,"%s"));
         proto_tree_add_text(FT_BCnPDU_tree, next_tvb, offset_payload, 1, "Pf : 0x%02x (%d)", pf,pf);
         proto_tree_add_text(FT_BCnPDU_tree, next_tvb, offset_payload, 2, "Ns : 0x%02x (%d)", mns_seqnum,mns_seqnum);
         offset_payload +=1;
         bctsdu_length-=1;
         proto_tree_add_text(FT_BCnPDU_tree, next_tvb, offset_payload, 2, "Nr : 0x%02x (%d)", mns_seqid,mns_seqid);
         offset_payload +=1;
         bctsdu_length-=1;
         proto_tree_add_text(FT_BCnPDU_tree, next_tvb, offset_payload, 1, "BCnSegType : 0x%02x (%s)", stype,val_to_str(stype,BCn_Seg_Type_vals,"%s"));
         offset_payload +=1;
         bctsdu_length-=1;
         
         
         switch (stype){
         
         case 0x00: // Continuation of Message
           
           msg_seqid=1;
          
           bctsdu_length+=1;
           
           rem_length = bctsdu_length;
           proto_tree_add_text(FT_BCnPDU_tree, next_tvb, offset_payload, rem_length , "PDU data : %d", rem_length);
           
                           
           
           
         break;
         
         case 0x01: // Beginning of Message
            
            msg_seqid=0;
            
            
            BCnPDU_stype_item = proto_tree_add_text(FT_BCnPDU_tree, next_tvb, offset_payload, 1, "%s",val_to_str(stype,BCn_Seg_Type_vals,"%s"));
            BCnPDU_stype_tree = proto_item_add_subtree(BCnPDU_stype_item, ett_BCnPDU_stype);
            
            BCnPDU_bom_item = proto_tree_add_text(BCnPDU_stype_tree, next_tvb, offset_payload, 1, "MACSAPFLAGS");
            BCnPDU_bom_tree = proto_item_add_subtree(BCnPDU_bom_item, ett_BCnPDU_bom);
            
            temp_val = (tvb_get_guint8(next_tvb, offset_payload) & 0x80) >>7 ; // Bit 8 - Flow Control
            proto_tree_add_text(BCnPDU_bom_tree, next_tvb, offset_payload, 1, "Flow Control : 0x%02x (%s)", temp_val,val_to_str(temp_val, true_false_vals,"%s"));
            temp_val = (tvb_get_guint8(next_tvb, offset_payload) & 0x40) >>6 ; // Bit 7 - Reserved l
            proto_tree_add_text(BCnPDU_bom_tree, next_tvb, offset_payload, 1, "Reserved l : 0x%02x (%d)", temp_val,temp_val);
            temp_val = (tvb_get_guint8(next_tvb, offset_payload) & 0x20) >>5 ; // Bit 6 - Expedited
            proto_tree_add_text(BCnPDU_bom_tree, next_tvb, offset_payload, 1, "Expedited : 0x%02x (%s)", temp_val,val_to_str(temp_val, true_false_vals,"%s"));
            temp_val = (tvb_get_guint8(next_tvb, offset_payload) & 0x10) >>4 ; // Bit 5 - OAM PDU Flag
            proto_tree_add_text(BCnPDU_bom_tree, next_tvb, offset_payload, 1, "OAM PDU Flag : 0x%02x (%s)", temp_val,val_to_str(temp_val, true_false_vals,"%s"));
            temp_val = (tvb_get_guint8(next_tvb, offset_payload) & 0x08) >>3 ; // Bit 4 - Reserved 2
            proto_tree_add_text(BCnPDU_bom_tree, next_tvb, offset_payload, 1, "Reserved 2 : 0x%02x (%d)", temp_val,temp_val);
            pdu_len = (tvb_get_ntohl(next_tvb, offset_payload) & 0x07ff0000) >>16; // PDU Length - 11 Bits
            
            proto_tree_add_text(BCnPDU_bom_tree, next_tvb, offset_payload, 2, "PDU Length : 0x%02x (%d)", pdu_len,pdu_len);
            
            offset_payload+=2;
            bctsdu_length-=2;
           
                        
            if (rem_length >= pdu_len){
            
            rem_length-=2;
            
            proto_tree_add_text(BCnPDU_bom_tree, next_tvb, offset_payload, rem_length, "PDU data (if) : %d ", rem_length);
            
            } else {
          
            proto_tree_add_text(BCnPDU_bom_tree, next_tvb, offset_payload, rem_length, "PDU data (else) : %d ", rem_length);
            
            }
            
            
         break;
         
         case 0x02: // End of Message
           
           msg_seqid=2;
           
           bctsdu_length+=2;
           
           more_frags=TRUE;
           
           
           rem_length =  bctsdu_length;
           rem_length-=2;
           
           proto_tree_add_text(FT_BCnPDU_tree, next_tvb, offset_payload, rem_length , "PDU data : %d", rem_length);
          
           disable_CRC=1;
           
           
         break;
         
         case 0x03: // Single Segment Message
            // No need of fragmentation and reassembly
            offset_payload+=1;
            bctsdu_length-=1;
            if (bctsdu_length>0){
           
             ALSIGPDU(next_tvb, pinfo, tree);
               }
               
           
           break;
           
           }
            
            if ( stype==0x01 || stype==0x02 || stype==0x00  ){
                       
                   
                       pinfo->fragmented = TRUE;
                       save_fragmented = pinfo->fragmented;
                       
                       frag_head = fragment_add_check(&mns_reassembly_table,
                          next_tvb,
                          offset_payload,
                          pinfo,
                          msg_seqid,
                          NULL,
                          mns_seqid,
                          pdu_length,
                          ((msg_seqid == 2)?0:1));
                          
                          
                          
                      
                        if (frag_head != NULL) {
                         
                           col_append_str(pinfo->cinfo, COL_INFO, " [Fragment Successful]");
                          } else {
                          
                          col_append_str(pinfo->cinfo, COL_INFO, " [Fragment Not Successful]");
                          }     
                             
                          save_fragmented = pinfo->fragmented;
                       pinfo->fragmented = FALSE;
                   

                       
                       res_tvb = process_reassembled_data( next_tvb, offset_payload, pinfo, "Reassembled PDU", frag_head, &mns_frag_items, NULL, FT_BCnPDU_tree );
                       save_fragmented = pinfo->fragmented;
                       pinfo->fragmented = FALSE;
                          
                       if (res_tvb) {
                          
                          col_append_str(pinfo->cinfo, COL_INFO, " [mns reassembled]");
                          } else {
                            col_append_str(pinfo->cinfo, COL_INFO, "[mns not reassembled ]");
                            
                            }
                         offset_payload+=rem_length; 
                         bctsdu_length-=rem_length;
           
                   }

 

    I dont have any clue my fragmentation always not succesful. please help.
 
Thanks
 
Best Regards
Raj