/* packet-ax25-kiss.c * * Routines for AX.25 KISS protocol dissection * Copyright 2010,2012 R.W. Stearn * * Wireshark - Network traffic analyzer * By Gerald Combs * Copyright 1998 Gerald Combs * * SPDX-License-Identifier: GPL-2.0-or-later */ /* * This dissector handles the "KISS" protocol as implemented by the * Linux kernel. * * The original definition of the KISS protocol can be found here: * http://www.ka9q.net/papers/kiss.html * and here: * http://www.ax25.net/kiss.aspx * * The Linux implementation does not appear to attempt to implement that * protocol in full. It does provide the ability to send a KISS command via * ax25_kiss_cmd() and internally will send FULLDUPLEX KISS commands if * DAMA is enabled/disabled. * i.e.: * ax25_dev_dama_on sends FullDuplex ON * ax25_dev_dama_off sends FullDuplex OFF * * Data frames are prefixed with a "Data Frame" command but the port appears to * be always 0. * * Abstract from http://www.ka9q.net/papers/kiss.html * -------------------------------------------------- * For reference the first byte of a KISS frame is the frame type and the TNC * port number, * LSB 4 bits = frame type, * MSB 4 bits = port number. * * The frame types are: * Command Function Comments * 0 Data frame The rest of the frame is data to * be sent on the HDLC channel. * * 1 TXDELAY The next byte is the transmitter * keyup delay in 10 ms units. * The default start-up value is 50 * (i.e., 500 ms). * * 2 P The next byte is the persistence * parameter, p, scaled to the range * 0 - 255 with the following * formula: * * P = p * 256 - 1 * * The default value is P = 63 * (i.e., p = 0.25). * * 3 SlotTime The next byte is the slot interval * in 10 ms units. * The default is 10 (i.e., 100ms). * * 4 TXtail The next byte is the time to hold * up the TX after the FCS has been * sent, in 10 ms units. This command * is obsolete, and is included here * only for compatibility with some * existing implementations. * * 5 FullDuplex The next byte is 0 for half duplex, * nonzero for full duplex. * The default is 0 * (i.e., half duplex). * * 6 SetHardware Specific for each TNC. In the * TNC-1, this command sets the * modem speed. Other implementations * may use this function for other * hardware-specific functions. * * FF Return Exit KISS and return control to a * higher-level program. This is useful * only when KISS is incorporated * into the TNC along with other * applications. * * * G8BPQ extensions: * * 12 Data frame Data with acknowledge request * * 14 Poll mode Set poll mode * * Checksum mode * */ #include "config.h" #include #include #include #define STRLEN 80 #define KISS_HEADER_SIZE 1 /* length of the KISS type header */ /* KISS frame types */ #define KISS_DATA_FRAME 0 #define KISS_TXDELAY 1 #define KISS_PERSISTENCE 2 #define KISS_SLOT_TIME 3 #define KISS_TXTAIL 4 #define KISS_FULLDUPLEX 5 #define KISS_SETHARDWARE 6 #define KISS_DATA_FRAME_ACK 12 #define KISS_POLL_MODE 14 #define KISS_RETURN 15 #define KISS_CMD_MASK 0x0f #define KISS_PORT_MASK 0xf0 /* Global preferences */ static bool gPREF_CKSUM_MODE; void proto_register_ax25_kiss(void); void proto_reg_handoff_ax25_kiss(void); /* Initialize the protocol and registered fields */ static int proto_ax25_kiss; static int hf_ax25_kiss_cmd; static int hf_ax25_kiss_port; static int hf_ax25_kiss_txdelay; static int hf_ax25_kiss_persistence; static int hf_ax25_kiss_slottime; static int hf_ax25_kiss_txtail; static int hf_ax25_kiss_fullduplex; static int hf_ax25_kiss_sethardware; static int hf_ax25_kiss_data_ack; static int hf_ax25_kiss_cksum; /* Initialize the subtree pointers */ static int ett_ax25_kiss; static dissector_handle_t kiss_handle; static capture_dissector_handle_t ax25_cap_handle; /* Dissector handles - all the possibles are listed */ static dissector_handle_t ax25_handle; static const value_string kiss_frame_types[] = { { KISS_DATA_FRAME, "Data frame" }, { KISS_TXDELAY, "Tx delay" }, { KISS_PERSISTENCE, "Persistence" }, { KISS_SLOT_TIME, "Slot time" }, { KISS_TXTAIL, "Tx tail" }, { KISS_FULLDUPLEX, "Full duplex" }, { KISS_SETHARDWARE, "Set hardware" }, { KISS_DATA_FRAME_ACK, "Data frame ack" }, { KISS_POLL_MODE, "Poll mode" }, { KISS_RETURN, "Return" }, { 0, NULL } }; static bool capture_ax25_kiss( const unsigned char *pd, int offset, int len, capture_packet_info_t *cpinfo, const union wtap_pseudo_header *pseudo_header) { int l_offset; uint8_t kiss_cmd; if ( ! BYTES_ARE_IN_FRAME( offset, len, KISS_HEADER_SIZE ) ) return false; l_offset = offset; kiss_cmd = pd[ l_offset ]; l_offset += KISS_HEADER_SIZE; /* step over kiss header */ switch ( kiss_cmd & KISS_CMD_MASK ) { case KISS_DATA_FRAME : return call_capture_dissector( ax25_cap_handle, pd, l_offset, len, cpinfo, pseudo_header ); case KISS_TXDELAY : break; case KISS_PERSISTENCE : break; case KISS_SLOT_TIME : break; case KISS_TXTAIL : break; case KISS_FULLDUPLEX : break; case KISS_SETHARDWARE : break; case KISS_DATA_FRAME_ACK: l_offset += 2; return call_capture_dissector( ax25_cap_handle, pd, l_offset, len, cpinfo, pseudo_header ); case KISS_POLL_MODE : break; case KISS_RETURN : break; default : break; } return false; } /* Code to actually dissect the packets */ static int dissect_ax25_kiss( tvbuff_t *tvb, packet_info *pinfo, proto_tree *parent_tree, void* data _U_ ) { proto_item *ti; proto_tree *kiss_tree; int offset; int kiss_cmd; int kiss_type; int kiss_port; int kiss_param; int kiss_param_len; int kiss_cksum; int kiss_cksum_index; int kiss_tvb_length; const char *frame_type_text; char *info_buffer; tvbuff_t *next_tvb = NULL; info_buffer = (char *)wmem_alloc( pinfo->pool, STRLEN ); info_buffer[0] = '\0'; col_set_str( pinfo->cinfo, COL_PROTOCOL, "AX.25 KISS" ); col_clear( pinfo->cinfo, COL_INFO ); /* protocol offset for the KISS header */ offset = 0; kiss_cmd = tvb_get_uint8( tvb, offset ) & 0xff; kiss_type = kiss_cmd & KISS_CMD_MASK; kiss_port = (kiss_cmd & KISS_PORT_MASK) >> 4; offset += KISS_HEADER_SIZE; kiss_param = 0; kiss_param_len = 0; switch ( kiss_type ) { case KISS_TXDELAY : kiss_param_len = 1; kiss_param = tvb_get_uint8( tvb, offset ) & 0xff; break; case KISS_PERSISTENCE : kiss_param_len = 1; kiss_param = tvb_get_uint8( tvb, offset ) & 0xff; break; case KISS_SLOT_TIME : kiss_param_len = 1; kiss_param = tvb_get_uint8( tvb, offset ) & 0xff; break; case KISS_TXTAIL : kiss_param_len = 1; kiss_param = tvb_get_uint8( tvb, offset ) & 0xff; break; case KISS_FULLDUPLEX : kiss_param_len = 1; kiss_param = tvb_get_uint8( tvb, offset ) & 0xff; break; case KISS_SETHARDWARE : kiss_param_len = tvb_captured_length_remaining( tvb, offset ); if ( kiss_param_len < 0 ) kiss_param_len = 0; if ( (kiss_param_len > 0) && gPREF_CKSUM_MODE ) kiss_param_len--; break; case KISS_DATA_FRAME_ACK: kiss_param_len = 2; kiss_param = tvb_get_uint8( tvb, offset ) & 0xff; break; default : break; } frame_type_text = val_to_str(kiss_type, kiss_frame_types, "Unknown (%u)"); snprintf( info_buffer, STRLEN, "%s, Port %u", frame_type_text, kiss_port ); if ( kiss_param_len > 0 ) snprintf( info_buffer, STRLEN, "%s %u, Port %u", frame_type_text, kiss_param, kiss_port ); offset += kiss_param_len; col_add_str( pinfo->cinfo, COL_INFO, info_buffer ); if ( parent_tree ) { /* protocol offset for the KISS header */ offset = 0; /* create display subtree for the protocol */ ti = proto_tree_add_protocol_format( parent_tree, proto_ax25_kiss, tvb, offset, tvb_captured_length_remaining( tvb, offset ), "KISS: %s", info_buffer ); kiss_tree = proto_item_add_subtree( ti, ett_ax25_kiss ); proto_tree_add_uint( kiss_tree, hf_ax25_kiss_cmd, tvb, offset, KISS_HEADER_SIZE, kiss_cmd ); proto_tree_add_uint( kiss_tree, hf_ax25_kiss_port, tvb, offset, KISS_HEADER_SIZE, kiss_port ); offset += KISS_HEADER_SIZE; switch ( kiss_type ) { case KISS_DATA_FRAME : break; case KISS_TXDELAY : proto_tree_add_uint( kiss_tree, hf_ax25_kiss_txdelay, tvb, offset, kiss_param_len, kiss_param ); offset += kiss_param_len; break; case KISS_PERSISTENCE : proto_tree_add_uint( kiss_tree, hf_ax25_kiss_persistence, tvb, offset, kiss_param_len, kiss_param ); offset += kiss_param_len; break; case KISS_SLOT_TIME : proto_tree_add_uint( kiss_tree, hf_ax25_kiss_slottime, tvb, offset, kiss_param_len, kiss_param ); offset += kiss_param_len; break; case KISS_TXTAIL : proto_tree_add_uint( kiss_tree, hf_ax25_kiss_txtail, tvb, offset, kiss_param_len, kiss_param ); offset += kiss_param_len; break; case KISS_FULLDUPLEX : proto_tree_add_uint( kiss_tree, hf_ax25_kiss_fullduplex, tvb, offset, kiss_param_len, kiss_param ); offset += kiss_param_len; break; case KISS_SETHARDWARE : proto_tree_add_item( kiss_tree, hf_ax25_kiss_sethardware, tvb, offset, kiss_param_len, ENC_NA ); offset += kiss_param_len; break; case KISS_DATA_FRAME_ACK: proto_tree_add_uint( kiss_tree, hf_ax25_kiss_data_ack, tvb, offset, kiss_param_len, kiss_param ); offset += kiss_param_len; break; case KISS_POLL_MODE : break; case KISS_RETURN : break; default : break; } if ( gPREF_CKSUM_MODE ) { kiss_cksum = 0; kiss_tvb_length = tvb_captured_length(tvb) - 1; if ( kiss_tvb_length > 0 ) { for ( kiss_cksum_index = 0; kiss_cksum_index < kiss_tvb_length; kiss_cksum_index++ ) kiss_cksum ^= (tvb_get_uint8( tvb, kiss_cksum_index ) & 0xff); proto_tree_add_checksum(kiss_tree, tvb, 0, hf_ax25_kiss_cksum, -1, NULL, pinfo, kiss_cksum, ENC_NA, PROTO_CHECKSUM_GENERATED); } } } /* Call sub-dissectors here */ if ( ( kiss_type == KISS_DATA_FRAME ) || ( kiss_type == KISS_DATA_FRAME_ACK ) ) { next_tvb = tvb_new_subset_remaining( tvb, offset ); call_dissector( ax25_handle, next_tvb, pinfo, parent_tree ); } return tvb_captured_length(tvb); } void proto_register_ax25_kiss(void) { module_t *ax25_kiss_module; /* Setup list of header fields */ static hf_register_info hf[] = { { &hf_ax25_kiss_cmd, { "Cmd", "ax25_kiss.cmd", FT_UINT8, BASE_DEC, VALS(kiss_frame_types), KISS_CMD_MASK, NULL, HFILL } }, { &hf_ax25_kiss_port, { "Port", "ax25_kiss.port", FT_UINT8, BASE_DEC, NULL, KISS_PORT_MASK, NULL, HFILL } }, { &hf_ax25_kiss_txdelay, { "Tx delay", "ax25_kiss.txdelay", FT_UINT8, BASE_DEC, NULL, 0x0, NULL, HFILL } }, { &hf_ax25_kiss_persistence, { "Persistence", "ax25_kiss.persistence", FT_UINT8, BASE_DEC, NULL, 0x0, NULL, HFILL } }, { &hf_ax25_kiss_slottime, { "Slot time", "ax25_kiss.slottime", FT_UINT8, BASE_DEC, NULL, 0x0, NULL, HFILL } }, { &hf_ax25_kiss_txtail, { "Tx tail", "ax25_kiss.txtail", FT_UINT8, BASE_DEC, NULL, 0x0, NULL, HFILL } }, { &hf_ax25_kiss_fullduplex, { "Full duplex", "ax25_kiss.fullduplex", FT_UINT8, BASE_DEC, NULL, 0x0, NULL, HFILL } }, { &hf_ax25_kiss_sethardware, { "Set hardware", "ax25_kiss.sethardware", FT_BYTES, BASE_NONE, NULL, 0x0, NULL, HFILL } }, { &hf_ax25_kiss_data_ack, { "Data ack", "ax25_kiss.data_ack", FT_UINT16, BASE_DEC, NULL, 0x0, NULL, HFILL } }, { &hf_ax25_kiss_cksum, { "Checksum", "ax25_kiss.cksum", FT_UINT16, BASE_HEX, NULL, 0x0, NULL, HFILL } }, }; /* Setup protocol subtree array */ static int *ett[] = { &ett_ax25_kiss, }; /* Register the protocol name and description */ proto_ax25_kiss = proto_register_protocol( "AX.25 KISS", "AX.25 KISS", "ax25_kiss" ); /* Register the dissector */ kiss_handle = register_dissector( "ax25_kiss", dissect_ax25_kiss, proto_ax25_kiss ); /* Required function calls to register the header fields and subtrees used */ proto_register_field_array( proto_ax25_kiss, hf, array_length( hf ) ); proto_register_subtree_array( ett, array_length( ett ) ); /* Register preferences module */ ax25_kiss_module = prefs_register_protocol( proto_ax25_kiss, NULL); prefs_register_bool_preference(ax25_kiss_module, "showcksum", "Set checksum mode", "Enable checksum calculation.", &gPREF_CKSUM_MODE ); } void proto_reg_handoff_ax25_kiss(void) { capture_dissector_handle_t ax25_kiss_cap_handle; dissector_add_uint( "wtap_encap", WTAP_ENCAP_AX25_KISS, kiss_handle ); ax25_kiss_cap_handle = create_capture_dissector_handle(capture_ax25_kiss, proto_ax25_kiss); capture_dissector_add_uint("wtap_encap", WTAP_ENCAP_AX25_KISS, ax25_kiss_cap_handle); /* only currently implemented for AX.25 */ ax25_handle = find_dissector_add_dependency( "ax25", proto_ax25_kiss ); ax25_cap_handle = find_capture_dissector("ax25"); } /* * Editor modelines - https://www.wireshark.org/tools/modelines.html * * Local variables: * c-basic-offset: 8 * tab-width: 8 * indent-tabs-mode: t * End: * * vi: set shiftwidth=8 tabstop=8 noexpandtab: * :indentSize=8:tabSize=8:noTabs=false: */