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DVB-S2 BB: Fix BB header CRC checks 

Fix problem with baseband header CRC check that caused almost all
baseband frames to show a spurious CRC error, introduced with
proto_tree_add_checksum.

Change-Id: I6b2f9680507eeb79e59b825f3ac9e4cee1033976
Reviewed-on: https://code.wireshark.org/review/19567
Petri-Dish: Alexis La Goutte <alexis.lagoutte@gmail.com>
Tested-by: Petri Dish Buildbot <buildbot-no-reply@wireshark.org>
Reviewed-by: Martin Kaiser <wireshark@kaiser.cx>
This commit is contained in:
MustBeArt 2017-01-01 08:47:40 -08:00 committed by Martin Kaiser
parent 0dcbfab426
commit fb9ac503c1
1 changed files with 4 additions and 9 deletions
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13
epan/dissectors/packet-dvb-s2-bb.c
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@ -546,7 +546,7 @@ static const range_string gse_proto_str[] = {
#define DVB_S2_GSE_CRC32_LEN 4
/* *** helper functions *** */
static gboolean check_crc8(tvbuff_t *p, guint8 len, guint8 offset, guint8 received_fcs)
static guint8 compute_crc8(tvbuff_t *p, guint8 len, guint8 offset)
{
int i;
guint8 crc = 0, tmp;
@ -555,10 +555,7 @@ static gboolean check_crc8(tvbuff_t *p, guint8 len, guint8 offset, guint8 receiv
tmp = tvb_get_guint8(p, offset++);
crc = crc8_table[crc ^ tmp];
}
if (received_fcs == crc)
return TRUE;
else
return FALSE;
return crc;
}
/* *** Code to actually dissect the packets *** */
@ -709,7 +706,7 @@ static gboolean test_dvb_s2_crc(tvbuff_t *tvb, guint offset) {
input8 = tvb_get_guint8(tvb, offset + DVB_S2_BB_OFFS_CRC);
if (!check_crc8(tvb, DVB_S2_BB_HEADER_LEN - 1, offset, input8))
if (compute_crc8(tvb, DVB_S2_BB_HEADER_LEN - 1, offset) != input8)
return FALSE;
else
return TRUE;
@ -787,11 +784,9 @@ static int dissect_dvb_s2_bb(tvbuff_t *tvb, int cur_off, proto_tree *tree, packe
new_off += 2;
proto_tree_add_item(dvb_s2_bb_tree, hf_dvb_s2_bb_syncd, tvb, cur_off + DVB_S2_BB_OFFS_SYNCD, 2, ENC_BIG_ENDIAN);
input8 = tvb_get_guint8(tvb, cur_off + DVB_S2_BB_OFFS_CRC);
new_off += 1;
proto_tree_add_checksum(dvb_s2_bb_tree, tvb, cur_off + DVB_S2_BB_OFFS_CRC, hf_dvb_s2_bb_crc, hf_dvb_s2_bb_crc_status, &ei_dvb_s2_bb_crc, pinfo,
check_crc8(tvb, DVB_S2_BB_HEADER_LEN - 1, cur_off, input8), ENC_NA, PROTO_CHECKSUM_VERIFY);
compute_crc8(tvb, DVB_S2_BB_HEADER_LEN - 1, cur_off), ENC_NA, PROTO_CHECKSUM_VERIFY);
while (bb_data_len) {
/* start DVB-GSE dissector */