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dicom: Handle frames with segments from different reassemblies 

There can be multiple PDV segments in the same frame that belong to
different reassemblies. Change the reassembly_id used for the
reassembly tables so that it is not identical for all segments in
the same presentation context (but still unique for a given reassembly),
so that that case can be handled properly. Otherwise fragment_add_seq_next
will retrieve the wrong reassembly for one of the segments (especially
on the second pass.)

Bug: 13110
Change-Id: Ib967fc7f6b7b591b9e3494d81d3b5d4ecc43cac1
Reviewed-on: https://code.wireshark.org/review/38200
Petri-Dish: Anders Broman <a.broman58@gmail.com>
Tested-by: Petri Dish Buildbot
Reviewed-by: Anders Broman <a.broman58@gmail.com>
This commit is contained in:
John Thacker 2020-08-19 10:15:33 -04:00 committed by Anders Broman
parent abd6f143c7
commit df69e61cb6
1 changed files with 15 additions and 1 deletions
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16
epan/dissectors/packet-dcm.c
View File

@ -597,6 +597,8 @@ typedef struct dcm_state_pdv {
dcm_open_tag_t open_tag; /* Container to store information about a fragmented tag */
guint8 reassembly_id;
} dcm_state_pdv_t;
/*
@ -617,6 +619,7 @@ typedef struct dcm_state_pctx {
#define DCM_ELE 0x03 /* explicit, little endian */
#define DCM_UNK 0xf0
guint8 reassembly_count;
dcm_state_pdv_t *first_pdv, *last_pdv; /* List of PDV objects */
} dcm_state_pctx_t;
@ -2479,6 +2482,13 @@ dissect_dcm_pdv_header(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree,
(*pdv)->syntax = DCM_UNK;
}
if (!PINFO_FD_VISITED(pinfo)) {
(*pdv)->reassembly_id = pctx->reassembly_count;
if ((*pdv)->is_last_fragment) {
pctx->reassembly_count++;
}
}
if (flags == 0 || flags == 2) {
/* Data PDV */
pdv_first_data = dcm_state_pdv_get_obj_start(*pdv);
@ -3535,13 +3545,17 @@ dissect_dcm_pdv_fragmented(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree,
/* Try to create somewhat unique ID.
Include the conversation index, to separate TCP session
Include bits from the reassembly number in the current Presentation
Context (that we track ourselves) in order to distinguish between
PDV fragments from the same frame but different reassemblies.
*/
DISSECTOR_ASSERT(conv);
/* The following expression seems to executed late in VS2017 in 'RelWithDebInf'.
Therefore it may appear as 0 at first
*/
reassembly_id = (((conv->conv_index) & 0x00FFFFFF) << 8) + (guint32)(pdv->pctx_id);
reassembly_id = (((conv->conv_index) & 0x000FFFFF) << 12) +
((guint32)(pdv->pctx_id) << 4) + ((guint32)(pdv->reassembly_id & 0xF));
/* This one will chain the packets until 'is_last_fragment' */
head = fragment_add_seq_next(