Wireshark mailing list archives
Re: Reassembly Fragment fail
From: Pascal Quantin <pascal.quantin () gmail com>
Date: Tue, 17 Feb 2015 12:19:46 +0100
2015-02-17 8:59 GMT+01:00 Raj sekar <mrajsekar () gmail com>:
Hi, Hi , Iam developing a custom dissector on top of UDP which uses PDCP layer PDU RFC 2507 Selective Repeat ARQ Mechanism for segmentation and Reassembly. My message contains Beginning of Message continuation of message and end of message Messages are not coming in sequence and based on sequence number and message id i need to reassemble. I dont know whether i should use conversation or add_fragment_seq_next or add_fragment_seq_check Please suggest. I got stuck with this for long time. Why is my code below not working? The fragmentation itself not successful and thus reassembly not working. Please suggest!
Hi, first of all I highly suggest you to read https://www.wireshark.org/docs/wsdg_html_chunked/ChDissectReassemble.html#idp424235420 and have a look at how it is used by other dissectors.
switch (stype) { case 0x00: // Continuation of Message msg_seqid = 2; 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 = 1; proto_tree_add_text(BCnPDU_bom_tree, next_tvb, offset_payload, 2, "PDU Length : 0x%02x (%d)", pdu_len, pdu_len); rem_length = tvb_length_remaining(next_tvb, offset_payload); rem_length -= 2; proto_tree_add_text(BCnPDU_bom_tree, next_tvb, offset_payload, rem_length, "PDU data : %d ", rem_length); break; case 0x02: // End of Message msg_seqid = 3; bctsdu_length += 2; more_frags = FALSE; 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 0x04: // Single Segment Message ---- // doesn't need fragment/reassembly break; } if (msg_seqid == 1 || msg_seqid == 2 || msg_seqid == 3) { save_fragmented = pinfo->fragmented; pinfo->fragmented = TRUE; frag_msg = fragment_add_seq_check(&mns_reassembly_table, next_tvb, offset_payload, pinfo, mns_seqnum, What is this mns_seqnum parameter? Do you confirm it changes between PDUs
and is the same for all fragments of a given PDU?
NULL, mns_seqid, mns_seqid should start from 0 while here you are starting it from 1. It
means that the API is endlessly waiting for the first fragment. As indicated in reassemble.h header file: * These functions add a new fragment to the fragment hash table, * assuming that frag_number is a block sequence number (starting from zero for * the first fragment of each datagram).
rem_length, more_frags); if (frag_msg) { col_append_fstr(pinfo->cinfo, COL_INFO, " mns segment of a FRAGMENT PDU"); } else { col_append_fstr(pinfo->cinfo, COL_INFO, " FRAGMENT NOT DONE "); } } if (more_frags == FALSE) { This code should be done unconditionally, and not only when you receive
the last fragment (especially as you could receive the last before the other ones). So remove this (more_frags == FALSE) check.
save_fragmented = pinfo->fragmented; pinfo->fragmented = FALSE; rass_tvb = process_reassembled_data(next_tvb, offset_payload, pinfo, "Reassembled Message", frag_msg, &mns_frag_items, NULL, FT_BCnPDU_tree); if (rass_tvb) { col_append_str(pinfo->cinfo, COL_INFO, "(Message reassembled ) "); ALSIGPDU(rass_tvb, pinfo, FT_BCnPDU_tree); } } I am always getting the FRAGMENT NOT DONE error.
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Current thread:
- Reassembly Fragment fail Raj sekar (Feb 16)
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- Re: Dissector plugin not working with wireshark 1.12.3 Pascal Quantin (Feb 17)
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- Re: Dissector plugin not working with wireshark 1.12.3 Pascal Quantin (Feb 17)
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- Re: Dissector plugin not working with wireshark 1.12.3 Pascal Quantin (Feb 17)
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