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Note that the "heuristic" is fatally weak, and must be strengthened or 

eliminated.

Fix indentation.

Use tvb_reported_length(), so we throw an exception for packets cut
short by a snapshot length.

Don't bother showing or dissecting the payload if there isn't any.

Don't show an item with a zero-length payload as going to the end of the
packet.

svn path=/trunk/; revision=29603
This commit is contained in:
Guy Harris 2009-08-29 01:08:31 +00:00
parent 988a595e79
commit a340788eb2
1 changed files with 86 additions and 67 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

153
epan/dissectors/packet-nb_rtpmux.c
View File

@ -57,8 +57,8 @@ dissect_nb_rtpmux(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree)
{
/* Set up structures needed to add the protocol subtree and manage it */
proto_item *ti;
proto_tree *nb_rtpmux_tree;
proto_item *ti;
proto_tree *nb_rtpmux_tree;
/* First, if at all possible, do some heuristics to check if the packet cannot
* possibly belong to your protocol. This is especially important for
@ -68,14 +68,24 @@ dissect_nb_rtpmux(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree)
* if someone analyzed that web server's traffic in Wireshark, would result
* in Wireshark handing an HTTP packet to your dissector). For example:
*/
/* Check that there's enough data */
if (tvb_length(tvb) < 6)
return 0;
/*
* XXX - this is *FAR* too weak a heuristic; it could cause all sorts
* of stuff to be incorrectly identified as Nb_RTPmux. Either this
* needs a stronger heuristic, or it needs to have a preference to
* set the port on which to dissect it, or it needs to be a non-heuristic
* dissector and *require* that a user use "Decode As..." to decode
* traffic as Nb_RTPmux.
*/
/* Check that there's enough data */
if (tvb_length(tvb) < 6)
return 0;
/* Make entries in Protocol column and Info column on summary display */
col_set_str(pinfo->cinfo, COL_PROTOCOL, "Nb_RTPmux");
col_set_str(pinfo->cinfo, COL_PROTOCOL, "Nb_RTPmux");
if (tree) {
if (tree) {
unsigned int offset = 0;
/* NOTE: The offset and length values in the call to
"proto_tree_add_item()" define what data bytes to highlight in the hex
@ -87,47 +97,58 @@ dissect_nb_rtpmux(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree)
/* create display subtree for the protocol */
while (offset < tvb_length(tvb)-5)
while (offset < tvb_reported_length(tvb)-5)
{
guint16 dstport, srcport;
unsigned int length;
gint captured_length;
tvbuff_t* next_tvb;
length = tvb_get_guint8(tvb, offset+2);
ti = proto_tree_add_item(tree, proto_nb_rtpmux, tvb, offset, length == 0 ? -1:length+5, FALSE);
nb_rtpmux_tree = proto_item_add_subtree(ti, ett_nb_rtpmux);
ti = proto_tree_add_item(tree, proto_nb_rtpmux, tvb, offset,
length+5, FALSE);
nb_rtpmux_tree = proto_item_add_subtree(ti, ett_nb_rtpmux);
proto_tree_add_item(nb_rtpmux_tree,
hf_nb_rtpmux_compressed, tvb, offset, 1, FALSE);
proto_tree_add_item(nb_rtpmux_tree,
hf_nb_rtpmux_compressed, tvb, offset, 1, FALSE);
dstport = (tvb_get_ntohs(tvb, offset) & 0x7fff) << 1;
proto_tree_add_uint(nb_rtpmux_tree, hf_nb_rtpmux_dstport, tvb, offset, 2, dstport );
proto_tree_add_item(nb_rtpmux_tree,
hf_nb_rtpmux_length, tvb, offset+2, 1, FALSE);
proto_tree_add_item(nb_rtpmux_tree,
hf_nb_rtpmux_length, tvb, offset+2, 1, FALSE);
srcport = (tvb_get_ntohs(tvb, offset+3) & 0x7fff) << 1;
proto_tree_add_uint(nb_rtpmux_tree, hf_nb_rtpmux_srcport, tvb, offset+3, 2, srcport );
if (length == 0)
{
/* XXX - is an item with a zero-length payload always
an end marker? */
break;
}
/* We have an RTP payload. */
if (rtpdissector)
{
next_tvb = tvb_new_subset(tvb, offset+5,
MIN(tvb_length(tvb)-5-offset, length), length);
captured_length = tvb_length_remaining(tvb, offset + 5);
if (captured_length > (gint)length)
captured_length = length;
next_tvb = tvb_new_subset(tvb, offset+5, captured_length,
length);
call_dissector(rtpdissector, next_tvb, pinfo, nb_rtpmux_tree);
call_dissector(rtpdissector, next_tvb, pinfo, nb_rtpmux_tree);
}
else
{
proto_tree_add_item(nb_rtpmux_tree,
hf_nb_rtpmux_data, tvb, offset+5, length == 0 ? -1:length, FALSE);
proto_tree_add_item(nb_rtpmux_tree,
hf_nb_rtpmux_data, tvb, offset+5, length, FALSE);
}
if (length == 0)
break;
offset += 5+length;
}
}
}
/* If this protocol has a sub-dissector call it here, see section 1.8 */
/* Return the amount of data this dissector was able to dissect */
return tvb_length(tvb);
return tvb_length(tvb);
}
@ -141,46 +162,46 @@ void
proto_register_nb_rtpmux(void)
{
static hf_register_info hf[] = {
{ &hf_nb_rtpmux_compressed,
{ "Compressed headers", "nb_rtpmux.compressed",
FT_BOOLEAN, BASE_NONE, NULL, 0x80,
"", HFILL }
},
{ &hf_nb_rtpmux_dstport,
{ "Dst port", "nb_rtpmux.dstport",
FT_UINT16, BASE_DEC, NULL, 0x00,
"", HFILL }
},
{ &hf_nb_rtpmux_length,
{ "Length", "nb_rtpmux.length",
FT_UINT8, BASE_DEC, NULL, 0x00,
"", HFILL }
},
{ &hf_nb_rtpmux_srcport,
{ "Src port", "nb_rtpmux.srcport",
FT_UINT16, BASE_DEC, NULL, 0x00,
"", HFILL }
},
{ &hf_nb_rtpmux_data,
{ "RTP Packet", "nb_rtpmux.data",
FT_BYTES, BASE_HEX, NULL, 0x00,
"", HFILL }
}
};
static hf_register_info hf[] = {
{ &hf_nb_rtpmux_compressed,
{ "Compressed headers", "nb_rtpmux.compressed",
FT_BOOLEAN, BASE_NONE, NULL, 0x80,
"", HFILL }
},
{ &hf_nb_rtpmux_dstport,
{ "Dst port", "nb_rtpmux.dstport",
FT_UINT16, BASE_DEC, NULL, 0x00,
"", HFILL }
},
{ &hf_nb_rtpmux_length,
{ "Length", "nb_rtpmux.length",
FT_UINT8, BASE_DEC, NULL, 0x00,
"", HFILL }
},
{ &hf_nb_rtpmux_srcport,
{ "Src port", "nb_rtpmux.srcport",
FT_UINT16, BASE_DEC, NULL, 0x00,
"", HFILL }
},
{ &hf_nb_rtpmux_data,
{ "RTP Packet", "nb_rtpmux.data",
FT_BYTES, BASE_HEX, NULL, 0x00,
"", HFILL }
}
};
/* Setup protocol subtree array */
static gint *ett[] = {
&ett_nb_rtpmux
};
static gint *ett[] = {
&ett_nb_rtpmux
};
/* Register the protocol name and description */
proto_nb_rtpmux = proto_register_protocol("3GPP Nb Interface RTP Multiplex",
"nb_rtpmux", "nb_rtpmux");
proto_nb_rtpmux = proto_register_protocol("3GPP Nb Interface RTP Multiplex",
"nb_rtpmux", "nb_rtpmux");
/* Required function calls to register the header fields and subtrees used */
proto_register_field_array(proto_nb_rtpmux, hf, array_length(hf));
proto_register_subtree_array(ett, array_length(ett));
proto_register_field_array(proto_nb_rtpmux, hf, array_length(hf));
proto_register_subtree_array(ett, array_length(ett));
}
@ -196,23 +217,21 @@ proto_register_nb_rtpmux(void)
void
proto_reg_handoff_nb_rtpmux(void)
{
static gboolean inited = FALSE;
static gboolean inited = FALSE;
if (!inited) {
if (!inited) {
dissector_handle_t nb_rtpmux_handle;
dissector_handle_t nb_rtpmux_handle;
/* Use new_create_dissector_handle() to indicate that dissect_nb_rtpmux()
* returns the number of bytes it dissected (or 0 if it thinks the packet
* does not belong to PROTONAME).
*/
nb_rtpmux_handle = new_create_dissector_handle(dissect_nb_rtpmux,
proto_nb_rtpmux);
nb_rtpmux_handle = new_create_dissector_handle(dissect_nb_rtpmux,
proto_nb_rtpmux);
dissector_add_handle("udp.port", nb_rtpmux_handle);
dissector_add_handle("udp.port", nb_rtpmux_handle);
rtpdissector = find_dissector("rtp");
inited = TRUE;
}
inited = TRUE;
}
}