Wireshark · Wireshark-dev: Re: [Wireshark-dev] [PATCH] new dissector for ip.access GSM A-bis over IP

[Michael Tüxen <Michael.Tuexen@xxxxxxxxxxxxxxxxx>]

Hi Harald,

I get a warning that len might be used uninitialized in  
dissect_ipa_attr,
which is the case if attr_type is neither 0x00 nor 0x01. What is the  
right
action if the switch statement falls through?
Why do you need the tag variable in that function?

Best regards
Michael


On Jul 4, 2009, at 4:22 AM, Harald Welte wrote:

> Hi!
>
> I've written the following wireshark dissector for the GSM A-bis  
> over IP
> protocol as it is used with ip.access nanoBTS products.  The code  
> was written
> while developing OpenBSC (see http://openbsc.gnumonks.org/).
>
> I'd like to request its inclusion into the wireshark mainline tree.   
> Please
> review and let me know if there are any issues.
>
> I'm also in the process of writing a generic GSM 12.21 (A-bis OML)  
> dissector,
> as well as extending the packet-rsl.c with ip.access nanoBTS vendor  
> extensions.
> I'm not sure when those will be finished, but I expect to post them  
> within the
> next couple of weeks.
>
> Regards,
> 	Harald
>
> Index: epan/dissectors/Makefile.common
> ===================================================================
> --- epan/dissectors/Makefile.common.orig	2009-07-03  
> 22:19:54.000000000 +0200
> +++ epan/dissectors/Makefile.common	2009-07-03 22:20:16.000000000  
> +0200
> @@ -471,6 +471,7 @@
> 	packet-gsm_a_gm.c		\
> 	packet-gsm_a_rp.c		\
> 	packet-gsm_a_rr.c	\
> +	packet-gsm_abis_ip.c	\
> 	packet-gsm_bsslap.c		\
> 	packet-gsm_bssmap_le.c	\
> 	packet-gsm_sms.c	\
> Index: epan/dissectors/packet-rsl.c
> ===================================================================
> --- epan/dissectors/packet-rsl.c.orig	2009-07-03 22:19:54.000000000  
> +0200
> +++ epan/dissectors/packet-rsl.c	2009-07-03 22:20:16.000000000 +0200
> @@ -3950,6 +3950,7 @@
> 	proto_register_field_array(proto_rsl, hf, array_length(hf));
> 	proto_register_subtree_array(ett, array_length(ett));
>
> +	register_dissector("gsm_abis_rsl", dissect_rsl, proto_rsl);
>
> }
>
> Index: epan/dissectors/packet-gsm_abis_ip.c
> ===================================================================
> --- /dev/null	1970-01-01 00:00:00.000000000 +0000
> +++ epan/dissectors/packet-gsm_abis_ip.c	2009-07-03  
> 22:20:16.000000000 +0200
> @@ -0,0 +1,279 @@
> +/* packet-gsm_abis_ip.c
> + * Routines for packet dissection of ip.access A-bis over IP
> + * Copyright 2009 by Harald Welte <laforge@xxxxxxxxxxxx>
> + *
> + * $Id$
> + *
> + * Wireshark - Network traffic analyzer
> + * By Gerald Combs <gerald@xxxxxxxxxxxxx>
> + * Copyright 1998 Gerald Combs
> + *
> + * This program is free software; you can redistribute it and/or
> + * modify it under the terms of the GNU General Public License
> + * as published by the Free Software Foundation; either version 2
> + * of the License, or (at your option) any later version.
> + *
> + * This program is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> + * GNU General Public License for more details.
> + *
> + * You should have received a copy of the GNU General Public License
> + * along with this program; if not, write to the Free Software
> + * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  
> 02111-1307, USA.
> + */
> +
> +#ifdef HAVE_CONFIG_H
> +# include "config.h"
> +#endif
> +
> +#include <glib.h>
> +
> +#include <epan/packet.h>
> +#include <epan/emem.h>
> +
> +/* Initialize the protocol and registered fields */
> +static int proto_abisip = -1;
> +static int proto_ipaccess = -1;
> +
> +static int hf_abisip_data_len = -1;
> +static int hf_abisip_protocol = -1;
> +
> +static int hf_ipaccess_msgtype = -1;
> +static int hf_ipaccess_attr_tag = -1;
> +static int hf_ipaccess_attr_string = -1;
> +
> +/* Initialize the subtree pointers */
> +static gint ett_abisip = -1;
> +static gint ett_ipaccess = -1;
> +
> +enum {
> +	SUB_OML,
> +	SUB_RSL,
> +	SUB_IPACCESS,
> +
> +	SUB_MAX
> +};
> +
> +static dissector_handle_t sub_handles[SUB_MAX];
> +
> +#define TCP_PORT_ABISIP_PRIM	 3002
> +#define TCP_PORT_ABISIP_SEC	 3003
> +#define TCP_PORT_ABISIP_INST	 3006
> +
> +#define ABISIP_RSL	0x00
> +#define ABISIP_IPACCESS	0xfe
> +#define ABISIP_OML	0xff
> +
> +static const value_string abisip_protocol_vals[] = {
> +	{ 0x00,		"RSL" },
> +	{ 0xfe,		"IPA" },
> +	{ 0xff,		"OML" },
> +	{ 0, 		NULL }
> +};
> +
> +static const value_string ipaccess_msgtype_vals[] = {
> +	{ 0x00,		"PING?" },
> +	{ 0x01, 	"PONG!" },
> +	{ 0x04, 	"IDENTITY REQUEST" },
> +	{ 0x05, 	"IDENTITY RESPONSE" },
> +	{ 0x06, 	"IDENTITY CONF" },
> +	{ 0,		NULL }
> +};
> +
> +static const value_string ipaccess_idtag_vals[] = {
> +	{ 0x00,		"Serial Number" },
> +	{ 0x01,		"Unit Name" },
> +	{ 0x02,		"Location" },
> +	{ 0x04,		"Equipment Version" },
> +	{ 0x05,		"Software Version" },
> +	{ 0x06,		"IP Address" },
> +	{ 0x07,		"MAC Address" },
> +	{ 0x08,		"Unit ID" },
> +};
> +
> +static gint
> +dissect_ipa_attr(tvbuff_t *tvb, int base_offs, proto_tree *tree)
> +{
> +	guint8 len, tag, attr_type;
> +
> +	int offset = base_offs;
> +
> +	while (tvb_reported_length_remaining(tvb, offset) != 0) {
> +		attr_type = tvb_get_guint8(tvb, offset);
> +
> +		switch (attr_type) {
> +		case 0x00:	/* a string prefixed by its length */
> +			len = tvb_get_guint8(tvb, offset+1);
> +			tag = tvb_get_guint8(tvb, offset+2);
> +			proto_tree_add_item(tree, hf_ipaccess_attr_tag,
> +					    tvb, offset+2, 1, FALSE);
> +			proto_tree_add_item(tree, hf_ipaccess_attr_string,
> +					    tvb, offset+3, len-1, FALSE);
> +			break;
> +		case 0x01:	/* a single-byte reqest for a certain attr */
> +			len = 0;
> +			proto_tree_add_item(tree, hf_ipaccess_attr_tag,
> +					    tvb, offset+1, 1, FALSE);
> +			break;
> +		};
> +		offset += len + 2;
> +	};
> +	return offset;
> +}
> +
> +/* Dissect an ip.access specific message */
> +static gint
> +dissect_ipaccess(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree)
> +{
> +	proto_item *ti;
> +	proto_tree *ipaccess_tree;
> +	guint8 msg_type;
> +
> +	msg_type = tvb_get_guint8(tvb, 0);
> +
> +	if (check_col(pinfo->cinfo, COL_INFO))
> +		col_append_fstr(pinfo->cinfo, COL_INFO, "%s ",
> +				val_to_str(msg_type, ipaccess_msgtype_vals,
> +					   "unknown 0x%02x"));
> +	if (tree) {
> +		ti = proto_tree_add_item(tree, proto_ipaccess, tvb, 0, -1, FALSE);
> +		ipaccess_tree = proto_item_add_subtree(ti, ett_ipaccess);
> +		proto_tree_add_item(ipaccess_tree, hf_ipaccess_msgtype,
> +				    tvb, 0, 1, FALSE);
> +		switch (msg_type) {
> +		case 4:
> +		case 5:
> +			dissect_ipa_attr(tvb, 1, ipaccess_tree);
> +			break;
> +		}
> +	}
> +
> +	return 1;
> +}
> +
> +
> +/* Code to actually dissect the packets */
> +static void
> +dissect_abisip(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree)
> +{
> +
> +	int offset = 0;
> +
> +	if (check_col(pinfo->cinfo, COL_PROTOCOL))
> +		col_set_str(pinfo->cinfo, COL_PROTOCOL, "Abis/IP");
> +	if (check_col(pinfo->cinfo, COL_INFO))
> +		col_clear(pinfo->cinfo, COL_INFO);
> +
> +	while (tvb_reported_length_remaining(tvb, offset) != 0) {
> +		proto_item *ti;
> +		proto_tree *abisip_tree;
> +		guint8 len, msg_type;
> +		tvbuff_t *next_tvb;
> +
> +		len = tvb_get_guint8(tvb, offset+1);
> +		msg_type = tvb_get_guint8(tvb, offset+2);
> +
> +		if (check_col(pinfo->cinfo, COL_INFO))
> +			col_append_fstr(pinfo->cinfo, COL_INFO, "%s ",
> +				     val_to_str(msg_type, abisip_protocol_vals,
> +						   "unknown 0x%02x"));
> +
> +		if (tree) {
> +			ti = proto_tree_add_protocol_format(tree, proto_abisip,
> +					tvb, offset, len+3,
> +					"A-bis/IP protocol ip.access, type: %s",
> +					val_to_str(msg_type, abisip_protocol_vals,
> +						   "unknown 0x%02x"));
> +			abisip_tree = proto_item_add_subtree(ti, ett_abisip);
> +			proto_tree_add_item(abisip_tree, hf_abisip_data_len,
> +					    tvb, offset+1, 1, FALSE);
> +			proto_tree_add_item(abisip_tree, hf_abisip_protocol,
> +					    tvb, offset+2, 1, FALSE);
> +		}
> +
> +		next_tvb = tvb_new_subset(tvb, offset+3, len, len);
> +
> +		switch (msg_type) {
> +		case ABISIP_RSL:
> +			/* hand this off to the standard A-bis RSL dissector */
> +			call_dissector(sub_handles[SUB_RSL], next_tvb, pinfo, tree);
> +			break;
> +		case ABISIP_OML:
> +			/* hand this off to the standard A-bis OML dissector */
> +			if (sub_handles[SUB_OML])
> +				call_dissector(sub_handles[SUB_OML], next_tvb,
> +						 pinfo, tree);
> +			break;
> +		case ABISIP_IPACCESS:
> +			dissect_ipaccess(next_tvb, pinfo, tree);
> +			break;
> +		}
> +		offset += len + 3;
> +	}
> +}
> +
> +void proto_register_abis_ip(void)
> +{
> +	static hf_register_info hf[] = {
> +		{&hf_abisip_data_len,
> +		 {"DataLen", "abisip.data_len",
> +		  FT_UINT8, BASE_DEC, NULL, 0x0,
> +		  "The length of the data (in bytes)", HFILL}
> +		 },
> +		{&hf_abisip_protocol,
> +		 {"Protocol", "abisip.protocol",
> +		  FT_UINT8, BASE_HEX, VALS(abisip_protocol_vals), 0x0,
> +		  "The A-bis/IP Sub-Protocol", HFILL}
> +		 },
> +	};
> +	static hf_register_info hf_ipa[] = {
> +		{&hf_ipaccess_msgtype,
> +		 {"MessageType", "ipaccess.msg_type",
> +		  FT_UINT8, BASE_HEX, VALS(ipaccess_msgtype_vals), 0x0,
> +		  "Type of ip.access messsage", HFILL}
> +		 },
> +		{&hf_ipaccess_attr_tag,
> +		 {"Tag", "ipaccess.attr_tag",
> +		  FT_UINT8, BASE_HEX, VALS(ipaccess_idtag_vals), 0x0,
> +		  "Attribute Tag", HFILL}
> +		 },
> +		{&hf_ipaccess_attr_string,
> +		 {"String", "ipaccess.attr_string",
> +		  FT_STRING, BASE_NONE, NULL, 0x0,
> +		  "String attribute", HFILL}
> +		 },
> +	};
> +
> +	static gint *ett[] = {
> +		&ett_abisip,
> +		&ett_ipaccess,
> +	};
> +
> +	proto_abisip =
> +	    proto_register_protocol("GSM A-bis/IP protocol as used by  
> ip.access",
> +				    "GSM A-bis/IP", "gsm_abis_ip");
> +	proto_ipaccess =
> +	    proto_register_protocol("GSM A-bis/IP ip.access CCM sub- 
> protocol",
> +				    "IPA", "ipaccess");
> +
> +	proto_register_field_array(proto_abisip, hf, array_length(hf));
> +	proto_register_field_array(proto_ipaccess, hf_ipa,  
> array_length(hf_ipa));
> +	proto_register_subtree_array(ett, array_length(ett));
> +
> +	register_dissector("gsm_abis_ip", dissect_abisip, proto_abisip);
> +}
> +
> +void proto_reg_handoff_gsm_abis_ip(void)
> +{
> +	dissector_handle_t abisip_handle;
> +
> +	sub_handles[SUB_RSL] = find_dissector("gsm_abis_rsl");
> +	sub_handles[SUB_OML] = find_dissector("gsm_abis_oml");
> +
> +	abisip_handle = create_dissector_handle(dissect_abisip,  
> proto_abisip);
> +	dissector_add("tcp.port", TCP_PORT_ABISIP_PRIM, abisip_handle);
> +	dissector_add("tcp.port", TCP_PORT_ABISIP_SEC, abisip_handle);
> +	dissector_add("tcp.port", TCP_PORT_ABISIP_INST, abisip_handle);
> +	dissector_add("udp.port", TCP_PORT_ABISIP_INST, abisip_handle);
> +}
>
> --
> - Harald Welte <laforge@xxxxxxxxxxxx>           http://laforge.gnumonks.org/
> = 
> = 
> = 
> = 
> = 
> = 
> ======================================================================
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