epan/dissectors/packet-sdlc.c

   1 /* packet-sdlc.c
   2  * Routines for SDLC frame disassembly
   3  *
   4  * Wireshark - Network traffic analyzer
   5  * By Gerald Combs <gerald@wireshark.org>
   6  * Copyright 1998
   7  *
   8  * SPDX-License-Identifier: GPL-2.0-or-later
   9  */
  10
  11 #include "config.h"
  12
  13 #include <epan/packet.h>
  14 #include <wiretap/wtap.h>
  15 #include <epan/xdlc.h>
  16 #include <epan/tfs.h>
  17 #include <wsutil/array.h>
  18
  19 /*
  20  * See:
  21  *
  22  * http://web.archive.org/web/20020206033700/http://www.wanresources.com/snacell.html
  23  *
  24  * http://web.archive.org/web/20150522015710/http://www.protocols.com/pbook/sna.htm
  25  *
  26  * Systems Network Architecture Formats, GA27-3136-20:
  27  * https://publibfp.dhe.ibm.com/epubs/pdf/d50a5007.pdf
  28  */
  29 void proto_register_sdlc(void);
  30 void proto_reg_handoff_sdlc(void);
  31
  32 static dissector_handle_t sdlc_handle;
  33
  34 static int proto_sdlc;
  35 static int hf_sdlc_address;
  36 static int hf_sdlc_control;
  37 static int hf_sdlc_n_r;
  38 static int hf_sdlc_n_s;
  39 static int hf_sdlc_p;
  40 static int hf_sdlc_f;
  41 static int hf_sdlc_s_ftype;
  42 static int hf_sdlc_u_modifier_cmd;
  43 static int hf_sdlc_u_modifier_resp;
  44 static int hf_sdlc_ftype_i;
  45 static int hf_sdlc_ftype_s_u;
  46
  47 static int ett_sdlc;
  48 static int ett_sdlc_control;
  49
  50 static dissector_handle_t sna_handle;
  51
  52 static const xdlc_cf_items sdlc_cf_items = {
  53         &hf_sdlc_n_r,
  54         &hf_sdlc_n_s,
  55         &hf_sdlc_p,
  56         &hf_sdlc_f,
  57         &hf_sdlc_s_ftype,
  58         &hf_sdlc_u_modifier_cmd,
  59         &hf_sdlc_u_modifier_resp,
  60         &hf_sdlc_ftype_i,
  61         &hf_sdlc_ftype_s_u
  62 };
  63
  64 static int
  65 dissect_sdlc(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, void* data _U_)
  66 {
  67         proto_tree      *sdlc_tree;
  68         proto_item      *sdlc_ti;
  69         uint8_t         addr;
  70         uint16_t                control;
  71         int             sdlc_header_len;
  72         bool    is_response;
  73         tvbuff_t        *next_tvb;
  74
  75         col_set_str(pinfo->cinfo, COL_PROTOCOL, "SDLC");
  76         col_clear(pinfo->cinfo, COL_INFO);
  77
  78         addr = tvb_get_uint8(tvb, 0);
  79         sdlc_header_len = 1;    /* address */
  80
  81         /*
  82          * XXX - is there something in the SDLC header that indicates
  83          * how to interpret "command vs. response" based on the
  84          * direction?
  85          */
  86         if (pinfo->p2p_dir == P2P_DIR_SENT) {
  87                 is_response = false;
  88                 col_set_str(pinfo->cinfo, COL_RES_DL_DST, "DCE");
  89                 col_set_str(pinfo->cinfo, COL_RES_DL_SRC, "DTE");
  90         }
  91         else {
  92                 /* XXX - what if the direction is unknown? */
  93                 is_response = true;
  94                 col_set_str(pinfo->cinfo, COL_RES_DL_DST, "DTE");
  95                 col_set_str(pinfo->cinfo, COL_RES_DL_SRC, "DCE");
  96         }
  97
  98         sdlc_ti = proto_tree_add_item(tree, proto_sdlc, tvb, 0, -1,
  99                 ENC_NA);
 100         sdlc_tree = proto_item_add_subtree(sdlc_ti, ett_sdlc);
 101
 102         proto_tree_add_uint(sdlc_tree, hf_sdlc_address, tvb, 0, 1,
 103                 addr);
 104
 105         /*
 106          * XXX - SDLC has a mod-128 mode as well as a mod-7 mode.
 107          * We can infer the mode from an SNRM/SRME frame, but if
 108          * we don't see one of them, we may have to have a preference
 109          * to control what to use.
 110          */
 111         control = dissect_xdlc_control(tvb, 1, pinfo, sdlc_tree, hf_sdlc_control,
 112             ett_sdlc_control, &sdlc_cf_items, NULL, NULL, NULL,
 113             is_response, false, false);
 114         sdlc_header_len += XDLC_CONTROL_LEN(control, false);
 115
 116         proto_item_set_len(sdlc_ti, sdlc_header_len);
 117
 118         /*
 119          * XXX - is there an FCS at the end, at least in Sniffer
 120          * captures?  (There doesn't appear to be.)
 121          */
 122         next_tvb = tvb_new_subset_remaining(tvb, sdlc_header_len);
 123         if (XDLC_IS_INFORMATION(control)) {
 124                 /* call the SNA dissector */
 125                 call_dissector(sna_handle, next_tvb, pinfo, tree);
 126         } else
 127                 call_data_dissector(next_tvb, pinfo, tree);
 128
 129         return tvb_captured_length(tvb);
 130 }
 131
 132 void
 133 proto_register_sdlc(void)
 134 {
 135         static hf_register_info hf[] = {
 136                 { &hf_sdlc_address,
 137                   { "Address Field", "sdlc.address", FT_UINT8, BASE_HEX,
 138                     NULL, 0x0, NULL, HFILL }},
 139
 140                 { &hf_sdlc_control,
 141                   { "Control Field", "sdlc.control", FT_UINT16, BASE_HEX,
 142                     NULL, 0x0, NULL, HFILL }},
 143
 144                 { &hf_sdlc_n_r,
 145                   { "N(R)", "sdlc.control.n_r", FT_UINT8, BASE_DEC,
 146                     NULL, XDLC_N_R_MASK, NULL, HFILL }},
 147
 148                 { &hf_sdlc_n_s,
 149                   { "N(S)", "sdlc.control.n_s", FT_UINT8, BASE_DEC,
 150                     NULL, XDLC_N_S_MASK, NULL, HFILL }},
 151
 152                 { &hf_sdlc_p,
 153                   { "Poll", "sdlc.control.p", FT_BOOLEAN, 8,
 154                     TFS(&tfs_set_notset), XDLC_P_F, NULL, HFILL }},
 155
 156                 { &hf_sdlc_f,
 157                   { "Final", "sdlc.control.f", FT_BOOLEAN, 8,
 158                     TFS(&tfs_set_notset), XDLC_P_F, NULL, HFILL }},
 159
 160                 { &hf_sdlc_s_ftype,
 161                   { "Supervisory frame type", "sdlc.control.s_ftype", FT_UINT8, BASE_HEX,
 162                     VALS(stype_vals), XDLC_S_FTYPE_MASK, NULL, HFILL }},
 163
 164                 { &hf_sdlc_u_modifier_cmd,
 165                   { "Command", "sdlc.control.u_modifier_cmd", FT_UINT8, BASE_HEX,
 166                     VALS(modifier_vals_cmd), XDLC_U_MODIFIER_MASK, NULL, HFILL }},
 167
 168                 { &hf_sdlc_u_modifier_resp,
 169                   { "Response", "sdlc.control.u_modifier_resp", FT_UINT8, BASE_HEX,
 170                     VALS(modifier_vals_resp), XDLC_U_MODIFIER_MASK, NULL, HFILL }},
 171
 172                 { &hf_sdlc_ftype_i,
 173                   { "Frame type", "sdlc.control.ftype", FT_UINT8, BASE_HEX,
 174                     VALS(ftype_vals), XDLC_I_MASK, NULL, HFILL }},
 175
 176                 { &hf_sdlc_ftype_s_u,
 177                   { "Frame type", "sdlc.control.ftype", FT_UINT8, BASE_HEX,
 178                     VALS(ftype_vals), XDLC_S_U_MASK, NULL, HFILL }},
 179         };
 180         static int *ett[] = {
 181                 &ett_sdlc,
 182                 &ett_sdlc_control,
 183         };
 184
 185         proto_sdlc = proto_register_protocol("Synchronous Data Link Control (SDLC)", "SDLC", "sdlc");
 186         proto_register_field_array(proto_sdlc, hf, array_length(hf));
 187         proto_register_subtree_array(ett, array_length(ett));
 188
 189         sdlc_handle = register_dissector("sdlc", dissect_sdlc, proto_sdlc);
 190 }
 191
 192 void
 193 proto_reg_handoff_sdlc(void)
 194 {
 195         /*
 196          * Get handle for the SNA dissector.
 197          */
 198         sna_handle = find_dissector_add_dependency("sna", proto_sdlc);
 199
 200         dissector_add_uint("wtap_encap", WTAP_ENCAP_SDLC, sdlc_handle);
 201 }
 202
 203 /*
 204  * Editor modelines  -  https://www.wireshark.org/tools/modelines.html
 205  *
 206  * Local variables:
 207  * c-basic-offset: 8
 208  * tab-width: 8
 209  * indent-tabs-mode: t
 210  * End:
 211  *
 212  * vi: set shiftwidth=8 tabstop=8 noexpandtab:
 213  * :indentSize=8:tabSize=8:noTabs=false:
 214  */