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SCTP: Fix relative sequence number calculation first pass 

Calculate the relative sequence number correctly for the first
data chunk of an association in the first pass. This fixes
tshark display and fixes calculation of retransmissions if the
first data chunk of an association is retransmitted. Fix #17917.
This commit is contained in:
John Thacker 2022-01-31 20:57:21 -05:00
parent 778fc283a7
commit b88b7ce798
1 changed files with 9 additions and 5 deletions
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14
epan/dissectors/packet-sctp.c
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@ -3332,7 +3332,7 @@ dissect_data_chunk(tvbuff_t *chunk_tvb,
proto_tree *flags_tree;
guint8 oct, e_bit, b_bit, u_bit;
guint16 stream_id;
guint32 tsn, ppid, stream_seq_num = 0;
guint32 tsn, rawtsn, ppid, stream_seq_num = 0;
proto_item *tsn_item = NULL;
gboolean call_subdissector = FALSE;
gboolean is_retransmission;
@ -3376,9 +3376,13 @@ dissect_data_chunk(tvbuff_t *chunk_tvb,
b_bit = oct & SCTP_DATA_CHUNK_B_BIT;
u_bit = oct & SCTP_DATA_CHUNK_U_BIT;
tsn = tvb_get_ntohl(chunk_tvb, DATA_CHUNK_TSN_OFFSET);
if((show_relative_tsns) && (ha)) {
tsn -= ha->first_tsn;
tsn = rawtsn = tvb_get_ntohl(chunk_tvb, DATA_CHUNK_TSN_OFFSET);
if ((show_relative_tsns) && (ha)) {
if (!ha->started) {
ha->first_tsn = tsn;
ha->started = TRUE;
}
tsn -= ha->first_tsn;
}
col_append_fstr(pinfo->cinfo, COL_INFO, "(TSN=%" PRIu32 ") ", tsn);
@ -3446,7 +3450,7 @@ dissect_data_chunk(tvbuff_t *chunk_tvb,
chunk_length - DATA_CHUNK_HEADER_LENGTH, plurality(chunk_length - DATA_CHUNK_HEADER_LENGTH, "", "s"));
}
is_retransmission = sctp_tsn(pinfo, chunk_tvb, tsn_item, ha, tsn);
is_retransmission = sctp_tsn(pinfo, chunk_tvb, tsn_item, ha, rawtsn);
if (is_idata) {
header_length = I_DATA_CHUNK_HEADER_LENGTH;