/* packet-lapb.c * Routines for lapb frame disassembly * Olivier Abad * * Wireshark - Network traffic analyzer * By Gerald Combs * Copyright 1998 * * SPDX-License-Identifier: GPL-2.0-or-later */ #include "config.h" #include #include #include void proto_register_lapb(void); void proto_reg_handoff_lapb(void); static int proto_lapb; static int hf_lapb_address; static int hf_lapb_control; static int hf_lapb_n_r; static int hf_lapb_n_s; static int hf_lapb_p; static int hf_lapb_f; static int hf_lapb_s_ftype; static int hf_lapb_u_modifier_cmd; static int hf_lapb_u_modifier_resp; static int hf_lapb_ftype_i; static int hf_lapb_ftype_s_u; static int ett_lapb; static int ett_lapb_control; static dissector_handle_t x25_dir_handle; static dissector_handle_t x25_handle; static dissector_handle_t lapb_handle; static const xdlc_cf_items lapb_cf_items = { &hf_lapb_n_r, &hf_lapb_n_s, &hf_lapb_p, &hf_lapb_f, &hf_lapb_s_ftype, &hf_lapb_u_modifier_cmd, &hf_lapb_u_modifier_resp, &hf_lapb_ftype_i, &hf_lapb_ftype_s_u }; static int dissect_lapb(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, void* data _U_) { proto_tree *lapb_tree, *ti; uint16_t control; int is_response; uint8_t byte0; tvbuff_t *next_tvb; col_set_str(pinfo->cinfo, COL_PROTOCOL, "LAPB"); col_clear(pinfo->cinfo, COL_INFO); switch (pinfo->p2p_dir) { case P2P_DIR_SENT: col_set_str(pinfo->cinfo, COL_RES_DL_SRC, "DTE"); col_set_str(pinfo->cinfo, COL_RES_DL_DST, "DCE"); break; case P2P_DIR_RECV: col_set_str(pinfo->cinfo, COL_RES_DL_SRC, "DCE"); col_set_str(pinfo->cinfo, COL_RES_DL_DST, "DTE"); break; default: col_set_str(pinfo->cinfo, COL_RES_DL_SRC, "N/A"); col_set_str(pinfo->cinfo, COL_RES_DL_DST, "N/A"); break; } byte0 = tvb_get_uint8(tvb, 0); if (byte0 != 0x01 && byte0 != 0x03 && byte0 != 0x07 && byte0 != 0x0f) /* invalid LAPB frame */ { col_set_str(pinfo->cinfo, COL_INFO, "Invalid LAPB frame"); if (tree) proto_tree_add_protocol_format(tree, proto_lapb, tvb, 0, -1, "Invalid LAPB frame"); return 1; } switch (pinfo->p2p_dir) { case P2P_DIR_SENT: if (byte0 == 0x03) is_response = true; else is_response = false; break; case P2P_DIR_RECV: if (byte0 == 0x01) is_response = true; else is_response = false; break; default: /* * XXX - should we base this on the source and destination * addresses? The problem is that we can tell one direction * from another with that, but we can't say which is DTE->DCE * and which is DCE->DTE. */ is_response = false; break; } ti = proto_tree_add_protocol_format(tree, proto_lapb, tvb, 0, 2, "LAPB"); lapb_tree = proto_item_add_subtree(ti, ett_lapb); proto_tree_add_uint(lapb_tree, hf_lapb_address, tvb, 0, 1, byte0); control = dissect_xdlc_control(tvb, 1, pinfo, lapb_tree, hf_lapb_control, ett_lapb_control, &lapb_cf_items, NULL, NULL, NULL, is_response, false, false); /* information frame ==> X.25 */ if (XDLC_IS_INFORMATION(control)) { next_tvb = tvb_new_subset_remaining(tvb, 2); switch (pinfo->p2p_dir) { case P2P_DIR_SENT: case P2P_DIR_RECV: call_dissector(x25_dir_handle, next_tvb, pinfo, tree); break; default: call_dissector(x25_handle, next_tvb, pinfo, tree); break; } } return tvb_captured_length(tvb); } void proto_register_lapb(void) { static hf_register_info hf[] = { { &hf_lapb_address, { "Address", "lapb.address", FT_UINT8, BASE_HEX, NULL, 0x0, NULL, HFILL }}, { &hf_lapb_control, { "Control Field", "lapb.control", FT_UINT8, BASE_HEX, NULL, 0x0, NULL, HFILL }}, { &hf_lapb_n_r, { "N(R)", "lapb.control.n_r", FT_UINT8, BASE_DEC, NULL, XDLC_N_R_MASK, NULL, HFILL }}, { &hf_lapb_n_s, { "N(S)", "lapb.control.n_s", FT_UINT8, BASE_DEC, NULL, XDLC_N_S_MASK, NULL, HFILL }}, { &hf_lapb_p, { "Poll", "lapb.control.p", FT_BOOLEAN, 8, TFS(&tfs_set_notset), XDLC_P_F, NULL, HFILL }}, { &hf_lapb_f, { "Final", "lapb.control.f", FT_BOOLEAN, 8, TFS(&tfs_set_notset), XDLC_P_F, NULL, HFILL }}, { &hf_lapb_s_ftype, { "Supervisory frame type", "lapb.control.s_ftype", FT_UINT8, BASE_HEX, VALS(stype_vals), XDLC_S_FTYPE_MASK, NULL, HFILL }}, { &hf_lapb_u_modifier_cmd, { "Command", "lapb.control.u_modifier_cmd", FT_UINT8, BASE_HEX, VALS(modifier_vals_cmd), XDLC_U_MODIFIER_MASK, NULL, HFILL }}, { &hf_lapb_u_modifier_resp, { "Response", "lapb.control.u_modifier_resp", FT_UINT8, BASE_HEX, VALS(modifier_vals_resp), XDLC_U_MODIFIER_MASK, NULL, HFILL }}, { &hf_lapb_ftype_i, { "Frame type", "lapb.control.ftype", FT_UINT8, BASE_HEX, VALS(ftype_vals), XDLC_I_MASK, NULL, HFILL }}, { &hf_lapb_ftype_s_u, { "Frame type", "lapb.control.ftype", FT_UINT8, BASE_HEX, VALS(ftype_vals), XDLC_S_U_MASK, NULL, HFILL }}, }; static int *ett[] = { &ett_lapb, &ett_lapb_control, }; proto_lapb = proto_register_protocol("Link Access Procedure Balanced (LAPB)", "LAPB", "lapb"); proto_register_field_array (proto_lapb, hf, array_length(hf)); proto_register_subtree_array(ett, array_length(ett)); lapb_handle = register_dissector("lapb", dissect_lapb, proto_lapb); } void proto_reg_handoff_lapb(void) { /* * Get handles for the X.25 dissectors; we don't get an X.25 * pseudo-header for LAPB-over-Ethernet, but we do get it * for raw LAPB. */ x25_dir_handle = find_dissector_add_dependency("x.25_dir", proto_lapb); x25_handle = find_dissector_add_dependency("x.25", proto_lapb); dissector_add_uint("wtap_encap", WTAP_ENCAP_LAPB, lapb_handle); } /* * Editor modelines - https://www.wireshark.org/tools/modelines.html * * Local variables: * c-basic-offset: 4 * tab-width: 8 * indent-tabs-mode: nil * End: * * vi: set shiftwidth=4 tabstop=8 expandtab: * :indentSize=4:tabSize=8:noTabs=true: */