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gmr1_rach: Update NULL GPS position decoding with reality 

The spec doesn't always match 100% reality. In this case it seems some
manufacturer implemented NULL GPS position with longitude.

Change-Id: I0c09627d64814a9467ecbecdc18e43974e4bab4a
Signed-off-by: Sylvain Munaut <tnt@246tNt.com>
Reviewed-on: https://code.wireshark.org/review/6289
Reviewed-by: Pascal Quantin <pascal.quantin@gmail.com>
This commit is contained in:
Sylvain Munaut 2015-01-03 10:50:28 +01:00 committed by Pascal Quantin
parent a16ac8f306
commit a22ea3dc52
1 changed files with 14 additions and 3 deletions
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17
epan/dissectors/packet-gmr1_rach.c
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@ -245,12 +245,23 @@ rach_gps_pos_long_fmt(gchar *s, guint32 v)
static void
dissect_gmr1_rach_gps_pos(tvbuff_t *tvb, int offset, packet_info *pinfo _U_, proto_tree *tree)
{
guint32 lat;
guint32 lat, lng;
/* Check for NULL */
lat = (tvb_get_ntohl(tvb, offset) >> 4) & 0x7ffff;
/* Spec says that NULL is latitude == 0x40000 and longitude
* is random. But from real capture it seems that
* longitude == 0x80000 and latitude random is also NULL pos */
lat = (tvb_get_ntohl(tvb, offset) >> 12) & 0x7ffff;
lng = tvb_get_ntohl(tvb, offset + 1) & 0xfffff;
if (lat == 0x40000) {
proto_tree_add_int_format(tree, hf_rach_gps_pos_lat, tvb, offset, 5, 0x40000, "NULL GPS Position");
proto_tree_add_int_format(tree, hf_rach_gps_pos_lat, tvb, offset, 5, lat,
"NULL GPS Position (latitude == 0x40000)");
return;
} else if (lng == 0x80000) {
proto_tree_add_int_format(tree, hf_rach_gps_pos_long, tvb, offset, 5, lng,
"NULL GPS Position (longitude == 0x80000)");
return;
}