osmith
/
wireshark
forked from osmocom/wireshark
1
0
Fork 0
Code Pull Requests Releases Wiki Activity

rlcmac: Handle properly LI=0 in GPRS data blocks and identify spare bits 

The previous handling of LI=0 was a confusion with the LI=0 meaning from
EGPRS (see TS 44.060 B.8.2 Example 2) data block.


(cherry picked from commit 9d5de22a88)
This commit is contained in:
Pau Espin 2020-11-03 20:01:32 +00:00 committed by Wireshark GitLab Utility
parent b97332b12e
commit a00ac1eb9c
1 changed files with 48 additions and 32 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

80
epan/dissectors/packet-gsm_rlcmac.c
View File

@ -8549,8 +8549,10 @@ static gint construct_egprs_data_segment_li_array(tvbuff_t *tvb, proto_tree *tre
return (offset - initial_offset);
}
static guint8 dissect_gprs_data_segments(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, guint8 initial_offset,
guint8 octet_length, guint8 li_count, length_indicator_t *li_array)
static guint8 dissect_gprs_data_segments(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree,
guint8 initial_offset, guint8 octet_length,
gboolean is_uplink, guint8 cs,
guint8 li_count, length_indicator_t *li_array)
{
guint8 octet_offset = initial_offset;
guint8 i;
@ -8558,6 +8560,10 @@ static guint8 dissect_gprs_data_segments(tvbuff_t *tvb, packet_info *pinfo, prot
gboolean more = TRUE, first_li = TRUE;
proto_tree *subtree = NULL;
guint8 blk_length = gsm_rlcmac_gprs_cs_to_block_length[cs - 1];
if (blk_length > octet_length)
blk_length = octet_length; /* part of the block or spare bits missing */
/* decode the LIs and any associated LLC Frames */
for(i = 0; (i < li_count) && more; i++)
{
@ -8569,9 +8575,16 @@ static guint8 dissect_gprs_data_segments(tvbuff_t *tvb, packet_info *pinfo, prot
switch (li)
{
case 0:
proto_tree_add_subtree_format(tree, tvb, li_array[i].offset, 1, ett_data_segments, NULL,
"LI[%d]=%d indicates: The previous segment of LLC Frame precisely filled the previous RLC Block",
i, li);
/* 3GPP TS 44.060 B.2 Example 2 */
col_append_str_uint(pinfo->cinfo, COL_INFO, "Len", blk_length - octet_offset, " ");
subtree = proto_tree_add_subtree_format(tree, tvb, li_array[i].offset, 1, ett_data_segments, NULL,
"LI[%d]=%d indicates: The current LLC PDU would fit within current RLC data block but the addition "
"of the length indicator octet (to indicate the LLC PDU boundary) causes the LLC PDU to extend into "
"another RLC data block",
i, li);
data_tvb = tvb_new_subset_length(tvb, octet_offset, blk_length - octet_offset);
call_data_dissector(data_tvb, pinfo, subtree);
octet_offset = blk_length;
break;
case 63:
@ -8587,9 +8600,9 @@ static guint8 dissect_gprs_data_segments(tvbuff_t *tvb, packet_info *pinfo, prot
"data segment: LI[%d]=%d indicates: The remainder of the RLC data block contains filler bits",
i, li);
}
data_tvb = tvb_new_subset_length(tvb, octet_offset, octet_length - octet_offset);
data_tvb = tvb_new_subset_length(tvb, octet_offset, blk_length - octet_offset);
call_data_dissector(data_tvb, pinfo, subtree);
octet_offset = octet_length;
octet_offset = blk_length;
break;
default:
@ -8604,24 +8617,27 @@ static guint8 dissect_gprs_data_segments(tvbuff_t *tvb, packet_info *pinfo, prot
}
first_li = FALSE;
}
if (octet_offset < octet_length)
if (octet_offset < blk_length)
{
/* if there is space left in the RLC Block, then it is a segment of LLC Frame without LI*/
if (more)
{
col_append_str_uint(pinfo->cinfo, COL_INFO, "Len", octet_length - octet_offset, " ");
subtree = proto_tree_add_subtree_format(tree, tvb, octet_offset, octet_length - octet_offset, ett_data_segments, NULL,
col_append_str_uint(pinfo->cinfo, COL_INFO, "Len", blk_length - octet_offset, " ");
subtree = proto_tree_add_subtree_format(tree, tvb, octet_offset, blk_length - octet_offset, ett_data_segments, NULL,
"data segment: LI not present: \n The Upper Layer PDU in the current RLC data block either fills the current RLC data block precisely \nor continues in the following in-sequence RLC data block");
}
else
{
subtree = proto_tree_add_subtree(tree, tvb, octet_offset, octet_length - octet_offset, ett_data_segments, NULL, "Padding Octets");
}
data_tvb = tvb_new_subset_length(tvb, octet_offset, octet_length - octet_offset);
call_data_dissector(data_tvb, pinfo, subtree);
octet_offset = octet_length;
data_tvb = tvb_new_subset_length(tvb, octet_offset, blk_length - octet_offset);
call_data_dissector(data_tvb, pinfo, subtree);
} else {
proto_tree_add_bytes_item(tree, hf_padding, tvb, octet_offset, blk_length - octet_offset, ENC_BIG_ENDIAN, NULL, NULL, NULL);
}
}
return (octet_offset - initial_offset);
octet_offset = blk_length;
if(octet_offset < octet_length)
proto_tree_add_bits_item(tree, is_uplink ? hf_ul_data_spare : hf_dl_data_spare, tvb,
octet_offset*8, (octet_length - octet_offset)*8, ENC_BIG_ENDIAN);
return octet_length;
}
static guint16 dissect_egprs_data_segments(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, guint initial_offset, guint8 octet_length, guint8 li_count, length_indicator_t *li_array)
@ -9005,13 +9021,13 @@ dissect_dl_gprs_block(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, RlcMa
{
length_indicator_t li_array[7];
guint8 li_count = array_length(li_array);
guint8 cs = (data->block_format & 0x0F);
guint64 e;
col_set_str(pinfo->cinfo, COL_PROTOCOL, "GSM RLC/MAC");
col_append_sep_fstr(pinfo->cinfo, COL_INFO, " ", "DATA: CS%d", data->block_format & 0x0F);
col_append_sep_fstr(pinfo->cinfo, COL_INFO, " ", "DATA: CS%d", cs);
ti = proto_tree_add_protocol_format(tree, proto_gsm_rlcmac, tvb, bit_offset >> 3, -1,
"GPRS DL DATA (CS%d)",
data->block_format & 0x0F);
"GPRS DL DATA (CS%d)", cs);
rlcmac_tree = proto_item_add_subtree(ti, ett_gsm_rlcmac);
csnStreamInit(&ar, 0, bit_length, pinfo);
@ -9040,9 +9056,9 @@ dissect_dl_gprs_block(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, RlcMa
if (e)
{
/* dissect the data segments */
/*bit_offset += 8 * */ dissect_gprs_data_segments(tvb, pinfo, rlcmac_tree, bit_offset / 8, bit_length / 8,
li_count,
li_array);
/*bit_offset += 8 * */ dissect_gprs_data_segments(tvb, pinfo, rlcmac_tree,
bit_offset / 8, bit_length / 8,
FALSE, cs, li_count, li_array);
}
else
{
@ -9438,11 +9454,11 @@ dissect_ul_gprs_block(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, RlcMa
guint64 e;
length_indicator_t li_array[10];
guint8 li_count = array_length(li_array);
guint8 cs = data->block_format & 0x0F;
col_append_sep_fstr(pinfo->cinfo, COL_INFO, " ", "DATA: CS%d", data->block_format & 0x0F);
col_append_sep_fstr(pinfo->cinfo, COL_INFO, " ", "DATA: CS%d", cs);
ti = proto_tree_add_protocol_format(tree, proto_gsm_rlcmac, tvb, bit_offset >> 3, -1,
"GPRS UL DATA (CS%d)",
data->block_format & 0x0F);
"GPRS UL DATA (CS%d)", cs);
rlcmac_tree = proto_item_add_subtree(ti, ett_gsm_rlcmac);
data->u.UL_Data_Block_GPRS.TI = 0;
data->u.UL_Data_Block_GPRS.PI = 0;
@ -9482,9 +9498,9 @@ dissect_ul_gprs_block(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, RlcMa
if (e)
{
/* dissect the data segments */
/*bit_offset += 8 * */ dissect_gprs_data_segments(tvb, pinfo, rlcmac_tree, bit_offset / 8, bit_length / 8,
li_count,
li_array);
/*bit_offset += 8 * */ dissect_gprs_data_segments(tvb, pinfo, rlcmac_tree,
bit_offset / 8, bit_length / 8,
TRUE, cs, li_count, li_array);
}
else
{
@ -10956,7 +10972,7 @@ proto_register_gsm_rlcmac(void)
},
{ &hf_padding,
{ "Padding", "gsm_rlcmac.dl.padding",
FT_UINT8, BASE_DEC, NULL, 0x0,
FT_BYTES, BASE_NONE, NULL, 0x0,
NULL, HFILL
}
},