Harald Welte <laforge@gnumonks.org>

via https://bugs.wireshark.org/bugzilla/show_bug.cgi?id=6792

This is a new dissector for the non-standard Ericsson OM2000 protocol, as it is
used for the OML on A-bis of Ericsson RBS 2xxx BTSs.

It also includes a dissector for a shim-layer protocol that Ericsson uses for
IP-based A-bis like the RBS 2409.  As the protocol is not publicly documented,
I have invented the name "EHDLC" (Ericsson HLDC) for it.


svn path=/trunk/; revision=41195

1 files changed, 322 insertions, 0 deletions

diff --git a/epan/dissectors/packet-ehdlc.c b/epan/dissectors/packet-ehdlc.c
new file mode 100644
index 0000000000..64f9eb152f
--- /dev/null
+++ b/epan/dissectors/packet-ehdlc.c
@@ -0,0 +1,322 @@
+/* packet-ehdlc.c
+ * Routines for packet dissection of Ericsson HDLC as used in A-bis over IP
+ * Copyright 2010-2012 by Harald Welte <laforge@gnumonks.org>
+ *
+ * $Id$
+ *
+ * This code is based on pure educational guesses while looking at protocol
+ * traces, as there is no publicly available protocol description by Ericsson.
+ * Even the name is a guess, since it looks quite a bit like HDLC and is used
+ * by Ericsson, I called it EHDLC.
+ *
+ * Wireshark - Network traffic analyzer
+ * By Gerald Combs <gerald@wireshark.org>
+ * 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/ipproto.h>
+#include <epan/xdlc.h>
+
+/* Initialize the protocol and registered fields */
+static int proto_ehdlc = -1;
+
+static int hf_ehdlc_data_len = -1;
+static int hf_ehdlc_protocol = -1;
+static int hf_ehdlc_sapi = -1;
+static int hf_ehdlc_c_r = -1;
+
+static int hf_ehdlc_xid_payload = -1;
+static int hf_ehdlc_control = -1;
+
+static int hf_ehdlc_p = -1;
+static int hf_ehdlc_f = -1;
+static int hf_ehdlc_u_modifier_cmd = -1;
+static int hf_ehdlc_u_modifier_resp = -1;
+static int hf_ehdlc_ftype_s_u = -1;
+
+static int hf_ehdlc_n_r = -1;
+static int hf_ehdlc_n_s = -1;
+static int hf_ehdlc_p_ext = -1;
+static int hf_ehdlc_f_ext = -1;
+static int hf_ehdlc_s_ftype = -1;
+static int hf_ehdlc_ftype_i = -1;
+static int hf_ehdlc_ftype_s_u_ext = -1;
+
+/* Used only for U frames */
+static const xdlc_cf_items ehdlc_cf_items = {
+	NULL,
+	NULL,
+	&hf_ehdlc_p,
+	&hf_ehdlc_f,
+	NULL,
+	&hf_ehdlc_u_modifier_cmd,
+	&hf_ehdlc_u_modifier_resp,
+	NULL,
+	&hf_ehdlc_ftype_s_u
+};
+
+/* Used only for I and S frames */
+static const xdlc_cf_items ehdlc_cf_items_ext = {
+	&hf_ehdlc_n_r,
+	&hf_ehdlc_n_s,
+	&hf_ehdlc_p_ext,
+	&hf_ehdlc_f_ext,
+	&hf_ehdlc_s_ftype,
+	NULL,
+	NULL,
+	&hf_ehdlc_ftype_i,
+	&hf_ehdlc_ftype_s_u_ext,
+};
+
+/* Initialize the subtree pointers */
+static gint ett_ehdlc = -1;
+static gint ett_ehdlc_control = -1;
+
+static const value_string ehdlc_protocol_vals[] = {
+	{ 0x20,		"RSL" },
+	{ 0xa0,		"ACK" },
+	{ 0xc0,		"OML" },
+	{ 0, 		NULL }
+};
+
+enum {
+	SUB_RSL,
+	SUB_OML,
+	SUB_DATA,
+
+	SUB_MAX
+};
+
+static dissector_handle_t sub_handles[SUB_MAX];
+
+/* Code to actually dissect the packets */
+static void
+dissect_ehdlc(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree)
+{
+	gint remaining;
+	int offset = 4;
+
+	col_set_str(pinfo->cinfo, COL_PROTOCOL, "EHDLC");
+	col_clear(pinfo->cinfo, COL_INFO);
+
+	while ((remaining = tvb_reported_length_remaining(tvb, offset)) > 0) {
+		proto_item *ti = NULL;
+		proto_tree *ehdlc_tree = NULL;
+		guint16 len, msg_type;
+		tvbuff_t *next_tvb;
+		guint16 control;
+		gboolean is_response = 0, is_extended = TRUE;
+		gint header_length = 2;	/* Address + Length field */
+
+		msg_type = tvb_get_guint8(tvb, offset);
+		len = tvb_get_guint8(tvb, offset+1);
+#if 0
+		col_append_fstr(pinfo->cinfo, COL_INFO, "%s ",
+		                val_to_str(msg_type, ehdlc_protocol_vals,
+		                           "unknown 0x%02x"));
+#endif
+		if (tree) {
+			ti = proto_tree_add_protocol_format(tree, proto_ehdlc,
+					tvb, offset, len,
+					"Ericsson HDLC protocol, type: %s",
+					val_to_str(msg_type, ehdlc_protocol_vals,
+						   "unknown 0x%02x"));
+			ehdlc_tree = proto_item_add_subtree(ti, ett_ehdlc);
+			proto_tree_add_item(ehdlc_tree, hf_ehdlc_protocol,
+					    tvb, offset, 1, FALSE);
+#if 0
+			proto_tree_add_item(ehdlc_tree, hf_ehdlc_sapi,
+					    tvb, offset, 1, FALSE);
+			proto_tree_add_item(ehdlc_tree, hf_ehdlc_c_r,
+					    tvb, offset, 1, FALSE);
+#endif
+			proto_tree_add_item(ehdlc_tree, hf_ehdlc_data_len,
+					    tvb, offset+1, 1, FALSE);
+		}
+
+		control = dissect_xdlc_control(tvb, offset+2, pinfo, ehdlc_tree, hf_ehdlc_control,
+					       ett_ehdlc_control, &ehdlc_cf_items, &ehdlc_cf_items_ext,
+					       NULL, NULL, is_response, is_extended, FALSE);
+		header_length += XDLC_CONTROL_LEN(control, is_extended);
+
+		if (XDLC_IS_INFORMATION(control)) {
+			next_tvb = tvb_new_subset(tvb, offset+header_length,
+						  len-header_length, len);
+
+			switch (msg_type) {
+			case 0x20:
+				/* len == 4 seems to be some kind of ACK */
+				if (len <= 4)
+					break;
+				call_dissector(sub_handles[SUB_RSL], next_tvb, pinfo, tree);
+				break;
+			case 0xbc:
+			case 0xdc:
+			case 0xa0:
+			case 0xc0:
+				/* len == 4 seems to be some kind of ACK */
+				if (len <= 4)
+					break;
+				call_dissector(sub_handles[SUB_OML], next_tvb, pinfo, tree);
+				break;
+			default:
+				call_dissector(sub_handles[SUB_DATA], next_tvb, pinfo, tree);
+				break;
+			}
+		} else if (control == (XDLC_U | XDLC_XID)) {
+			/* XID is formatted like ISO 8885, typically we see
+ 			 * something like
+			 * 82		format identifier
+			 * 80		group identifier
+			 * 00 09 	length
+			 * 07 01 05 	Window Size Tx
+			 * 09 01 04	Ack Timer (msec)
+			 * 08 01 05	Window Size Rx */
+			proto_tree_add_item(ehdlc_tree, hf_ehdlc_xid_payload,
+					    tvb, offset+header_length,
+					    len-header_length, FALSE);
+		}
+
+		if (len == 0)
+			len = 1;
+		offset += len;
+	}
+}
+
+void proto_register_ehdlc(void)
+{
+	static hf_register_info hf[] = {
+		{ &hf_ehdlc_data_len,
+		  { "DataLen", "ehdlc.data_len",
+		    FT_UINT8, BASE_DEC, NULL, 0x0,
+		    "The length of the data (in bytes)", HFILL }
+		},
+		{ &hf_ehdlc_protocol,
+		  { "Protocol", "ehdlc.protocol",
+		    FT_UINT8, BASE_HEX, VALS(ehdlc_protocol_vals), 0x0,
+		    "The HDLC Sub-Protocol", HFILL }
+		},
+		{ &hf_ehdlc_sapi,
+		  { "SAPI", "ehdlc.sapi",
+		    FT_UINT8, BASE_DEC, NULL, 0x1f,
+		    NULL, HFILL }
+		},
+		{ &hf_ehdlc_c_r,
+		  { "C/R", "ehdlc.c_r",
+		    FT_UINT8, BASE_HEX, NULL, 0x20,
+		    NULL, HFILL }
+		},
+		{ &hf_ehdlc_xid_payload,
+		  { "XID Payload", "ehdlc.xid_payload",
+		    FT_BYTES, BASE_NONE, NULL, 0,
+		    NULL, HFILL }
+		},
+		{ &hf_ehdlc_control,
+		  { "Control Field", "ehdlc.control",
+		    FT_UINT16, BASE_HEX, NULL, 0,
+		    NULL, HFILL }
+		},
+		{ &hf_ehdlc_n_r,
+		  { "N(R)", "ehdlc.control.n_r",
+		    FT_UINT16, BASE_DEC, NULL, XDLC_N_R_EXT_MASK,
+		    NULL, HFILL }
+		},
+		{ &hf_ehdlc_n_s,
+		  { "N(S)", "ehdlc.control.n_s",
+		    FT_UINT16, BASE_DEC, NULL, XDLC_N_S_EXT_MASK,
+		    NULL, HFILL }
+		},
+		{ &hf_ehdlc_p,
+		  { "Poll", "ehdlc.control.p",
+		    FT_BOOLEAN, 8, TFS(&tfs_set_notset), XDLC_P_F,
+		    NULL, HFILL }
+		},
+		{ &hf_ehdlc_p_ext,
+		  { "Poll", "ehdlc.control.p",
+		    FT_BOOLEAN, 16, TFS(&tfs_set_notset), XDLC_P_F_EXT,
+		    NULL, HFILL }
+		},
+		{ &hf_ehdlc_f,
+		  { "Final", "ehdlc.control.f",
+		    FT_BOOLEAN, 8, TFS(&tfs_set_notset), XDLC_P_F,
+		    NULL, HFILL }
+		},
+		{ &hf_ehdlc_f_ext,
+		  { "Final", "ehdlc.control.f",
+		    FT_BOOLEAN, 16, TFS(&tfs_set_notset), XDLC_P_F_EXT,
+		    NULL, HFILL }
+		},
+		{ &hf_ehdlc_s_ftype,
+		  { "Supervisory frame type", "ehdlc.control.s_ftype",
+		    FT_UINT16, BASE_HEX, VALS(stype_vals), XDLC_S_FTYPE_MASK,
+		    NULL, HFILL }
+		},
+		{ &hf_ehdlc_u_modifier_cmd,
+		  { "Command", "ehdlc.control.u_modifier_cmd",
+		    FT_UINT8, BASE_HEX, VALS(modifier_vals_cmd), XDLC_U_MODIFIER_MASK,
+		    NULL, HFILL }
+		},
+		{ &hf_ehdlc_u_modifier_resp,
+		  { "Response", "ehdlc.control.u_modifier_resp",
+		    FT_UINT8, BASE_HEX, VALS(modifier_vals_resp), XDLC_U_MODIFIER_MASK,
+		    NULL, HFILL }
+		},
+		{ &hf_ehdlc_ftype_i,
+		  { "Frame Type", "ehdlc.control.ftype",
+		    FT_UINT16, BASE_HEX, VALS(ftype_vals), XDLC_I_MASK,
+		    NULL, HFILL }
+		},
+		{ &hf_ehdlc_ftype_s_u,
+		  { "Frame Type", "ehdlc.control.ftype",
+		    FT_UINT8, BASE_HEX, VALS(ftype_vals), XDLC_S_U_MASK,
+		    NULL, HFILL }
+		},
+		{ &hf_ehdlc_ftype_s_u_ext,
+		  { "Frame Type", "ehdlc.control.ftype",
+		    FT_UINT16, BASE_HEX, VALS(ftype_vals), XDLC_S_U_MASK,
+		    NULL, HFILL }
+		},
+	};
+
+	static gint *ett[] = {
+		&ett_ehdlc,
+		&ett_ehdlc_control,
+	};
+
+	proto_ehdlc =
+	    proto_register_protocol("Ericsson HDLC",
+				    "Ericsson HDLC as used in A-bis over IP", "ehdlc");
+
+	proto_register_field_array(proto_ehdlc, hf, array_length(hf));
+	proto_register_subtree_array(ett, array_length(ett));
+
+	register_dissector("ehdlc", dissect_ehdlc, proto_ehdlc);
+}
+
+void proto_reg_handoff_ehdlc(void)
+{
+	sub_handles[SUB_RSL] = find_dissector("gsm_abis_rsl");
+	sub_handles[SUB_OML] = find_dissector("gsm_abis_oml");
+	sub_handles[SUB_DATA] = find_dissector("data");
+}