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wireshark/epan/dissectors/packet-ax25.c

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/* packet-ax25.c
*
* Routines for Amateur Packet Radio protocol dissection
* AX.25 frames
* Copyright 2005,2006,2007,2008,2009,2010,2012 R.W. Stearn <richard@rns-stearn.demon.co.uk>
*
* Wireshark - Network traffic analyzer
* By Gerald Combs <gerald@wireshark.org>
* Copyright 1998 Gerald Combs
*
* SPDX-License-Identifier: GPL-2.0-or-later
*/
/*
* This dissector is for:
* AX.25 Amateur Packet-Radio Link-Layer Protocol, Version 2.0, October 1984
*
* At the time of writing the specification could be found here:
* http://www.tapr.org/pub_ax25.html
*
* A newer version, Version 2.2, July 1998, can be found at
* http://www.ax25.net/AX25.2.2-Jul%2098-2.pdf
*
* Inspiration on how to build the dissector drawn from
* packet-sdlc.c
* packet-x25.c
* packet-lapb.c
* paket-gprs-llc.c
* xdlc.c
* with the base file built from README.developers.
*/
#include "config.h"
#include <epan/packet.h>
#include <epan/capture_dissectors.h>
#include <wiretap/wtap.h>
#include <epan/to_str.h>
#include <epan/xdlc.h>
#include <epan/ax25_pids.h>
#include <epan/ipproto.h>
#define STRLEN 80
#define AX25_HEADER_SIZE 15 /* length of src_addr + dst_addr + cntl */
#define AX25_MAX_DIGIS 8
void proto_register_ax25(void);
void proto_reg_handoff_ax25(void);
/* Dissector table */
static dissector_table_t ax25_dissector_table;
static capture_dissector_handle_t ax25_cap_handle;
/* Initialize the protocol and registered fields */
static int proto_ax25 = -1;
static int hf_ax25_dst = -1;
static int hf_ax25_src = -1;
static int hf_ax25_via[ AX25_MAX_DIGIS ] = { -1,-1,-1,-1,-1,-1,-1,-1 };
static int hf_ax25_ctl = -1;
static int hf_ax25_n_r = -1;
static int hf_ax25_n_s = -1;
static int hf_ax25_p = -1;
static int hf_ax25_f = -1;
static int hf_ax25_ftype_s = -1;
static int hf_ax25_ftype_i = -1;
static int hf_ax25_ftype_su = -1;
static int hf_ax25_u_cmd = -1;
static int hf_ax25_u_resp = -1;
static int hf_ax25_pid = -1;
static const xdlc_cf_items ax25_cf_items = {
&hf_ax25_n_r,
&hf_ax25_n_s,
&hf_ax25_p,
&hf_ax25_f,
&hf_ax25_ftype_s,
&hf_ax25_u_cmd,
&hf_ax25_u_resp,
&hf_ax25_ftype_i,
&hf_ax25_ftype_su
};
static const value_string pid_vals[] = {
{ AX25_P_ROSE, "Rose" },
{ AX25_P_RFC1144C, "RFC1144 (compressed)" },
{ AX25_P_RFC1144, "RFC1144 (uncompressed)" },
{ AX25_P_SEGMENT, "Segment" },
{ AX25_P_TEXNET, "Texnet" },
{ AX25_P_LCP, "Link Quality protocol" },
{ AX25_P_ATALK, "AppleTalk" },
{ AX25_P_ATALKARP, "AppleTalk ARP" },
{ AX25_P_IP, "IP" },
{ AX25_P_ARP, "ARP" },
{ AX25_P_FLEXNET, "FlexNet" },
{ AX25_P_NETROM, "NetRom" },
{ AX25_P_NO_L3, "No L3" },
{ AX25_P_L3_ESC, "L3 esc" },
{ 0, NULL }
};
static gint ett_ax25 = -1;
static gint ett_ax25_ctl = -1;
static dissector_handle_t ax25_handle;
static int
dissect_ax25( tvbuff_t *tvb, packet_info *pinfo, proto_tree *parent_tree, void* data _U_ )
{
proto_item *ti;
proto_tree *ax25_tree;
int offset;
int via_index;
char *info_buffer;
/* char v2cmdresp; */
const char *ax25_version;
int is_response;
guint8 control;
guint8 pid = AX25_P_NO_L3;
guint8 src_ssid;
guint8 dst_ssid;
tvbuff_t *next_tvb = NULL;
info_buffer = (char *)wmem_alloc( wmem_packet_scope(), STRLEN );
info_buffer[0] = '\0';
col_set_str( pinfo->cinfo, COL_PROTOCOL, "AX.25" );
col_clear( pinfo->cinfo, COL_INFO );
/* start at the dst addr */
offset = 0;
/* create display subtree for the protocol */
ti = proto_tree_add_protocol_format( parent_tree, proto_ax25, tvb, offset, -1, "AX.25");
ax25_tree = proto_item_add_subtree( ti, ett_ax25 );
proto_tree_add_item( ax25_tree, hf_ax25_dst, tvb, offset, AX25_ADDR_LEN, ENC_NA);
set_address_tvb(&pinfo->dl_dst, AT_AX25, AX25_ADDR_LEN, tvb, offset);
copy_address_shallow(&pinfo->dst, &pinfo->dl_dst);
dst_ssid = tvb_get_guint8(tvb, offset+6);
/* step over dst addr point at src addr */
offset += AX25_ADDR_LEN;
proto_tree_add_item( ax25_tree, hf_ax25_src, tvb, offset, AX25_ADDR_LEN, ENC_NA);
set_address_tvb(&pinfo->dl_src, AT_AX25, AX25_ADDR_LEN, tvb, offset);
copy_address_shallow(&pinfo->src, &pinfo->dl_src);
src_ssid = tvb_get_guint8(tvb, offset+6);
/* step over src addr point at either 1st via addr or control byte */
offset += AX25_ADDR_LEN;
proto_item_append_text( ti, ", Src: %s, Dst: %s",
address_to_str(wmem_packet_scope(), &pinfo->src),
address_to_str(wmem_packet_scope(), &pinfo->dst));
/* decode the cmd/resp field */
/* v2cmdresp = '.'; */
switch ( ( (dst_ssid >> 6) & 0x02) | ( (src_ssid >> 7) & 0x01 ) )
{
case 1 : /* V2.0 Response */
ax25_version = "V2.0+";
/* v2cmdresp = 'R'; */
is_response = TRUE;
break;
case 2 : /* V2.0 Command */
ax25_version = "V2.0+";
/* v2cmdresp = 'C'; */
is_response = FALSE;
break;
default :
ax25_version = "V?.?";
/* v2cmdresp = '?'; */
is_response = FALSE;
break;
}
proto_item_append_text( ti, ", Ver: %s", ax25_version );
/* handle the vias, if any */
via_index = 0;
while ( ( tvb_get_guint8( tvb, offset - 1 ) & 0x01 ) == 0 )
{
if ( via_index < AX25_MAX_DIGIS )
{
proto_tree_add_item( ax25_tree, hf_ax25_via[ via_index ], tvb, offset, AX25_ADDR_LEN, ENC_NA);
via_index++;
}
/* step over a via addr */
offset += AX25_ADDR_LEN;
}
/* XXX - next-to-last argument should be TRUE if modulo 128 operation */
control = dissect_xdlc_control( tvb,
offset,
pinfo,
ax25_tree,
hf_ax25_ctl,
ett_ax25_ctl,
&ax25_cf_items,
NULL,
NULL,
NULL,
is_response,
FALSE,
FALSE );
/* XXX - second argument should be TRUE if modulo 128 operation */
offset += XDLC_CONTROL_LEN(control, FALSE); /* step over control field */
if ( XDLC_IS_INFORMATION( control ) )
{
pid = tvb_get_guint8( tvb, offset );
col_append_fstr( pinfo->cinfo, COL_INFO, ", %s", val_to_str(pid, pid_vals, "Unknown (0x%02x)") );
proto_tree_add_uint( ax25_tree, hf_ax25_pid, tvb, offset, 1, pid );
/* Call sub-dissectors here */
offset += 1; /* step over pid to the 1st byte of the payload */
proto_item_set_end(ti, tvb, offset);
next_tvb = tvb_new_subset_remaining(tvb, offset);
if (!dissector_try_uint(ax25_dissector_table, pid, next_tvb, pinfo, parent_tree))
{
call_data_dissector(next_tvb, pinfo, parent_tree);
}
}
else
proto_item_set_end(ti, tvb, offset);
return tvb_captured_length(tvb);
}
static gboolean
capture_ax25( const guchar *pd, int offset, int len, capture_packet_info_t *cpinfo, const union wtap_pseudo_header *pseudo_header)
{
guint8 control;
guint8 pid;
int l_offset;
if ( ! BYTES_ARE_IN_FRAME( offset, len, AX25_HEADER_SIZE ) )
return FALSE;
l_offset = offset;
l_offset += AX25_ADDR_LEN; /* step over dst addr point at src addr */
l_offset += AX25_ADDR_LEN; /* step over src addr point at either 1st via addr or control byte */
while ( ( pd[ l_offset - 1 ] & 0x01 ) == 0 )
l_offset += AX25_ADDR_LEN; /* step over a via addr */
control = pd[ l_offset ];
/* decode the pid field (if appropriate) */
if ( XDLC_IS_INFORMATION( control ) )
{
l_offset += 1; /* step over control byte point at pid */
pid = pd[ l_offset ];
l_offset += 1; /* step over the pid and point to the first byte of the payload */
return try_capture_dissector("ax25.pid", pid & 0x0ff, pd, l_offset, len, cpinfo, pseudo_header);
}
return FALSE;
}
void
proto_register_ax25(void)
{
/* Setup list of header fields */
static hf_register_info hf[] = {
{ &hf_ax25_dst,
{ "Destination", "ax25.dst",
FT_AX25, BASE_NONE, NULL, 0x0,
"Destination callsign", HFILL }
},
{ &hf_ax25_src,
{ "Source", "ax25.src",
FT_AX25, BASE_NONE, NULL, 0x0,
"Source callsign", HFILL }
},
{ &hf_ax25_via[ 0 ],
{ "Via 1", "ax25.via1",
FT_AX25, BASE_NONE, NULL, 0x0,
"Via callsign 1", HFILL }
},
{ &hf_ax25_via[ 1 ],
{ "Via 2", "ax25.via2",
FT_AX25, BASE_NONE, NULL, 0x0,
"Via callsign 2", HFILL }
},
{ &hf_ax25_via[ 2 ],
{ "Via 3", "ax25.via3",
FT_AX25, BASE_NONE, NULL, 0x0,
"Via callsign 3", HFILL }
},
{ &hf_ax25_via[ 3 ],
{ "Via 4", "ax25.via4",
FT_AX25, BASE_NONE, NULL, 0x0,
"Via callsign 4", HFILL }
},
{ &hf_ax25_via[ 4 ],
{ "Via 5", "ax25.via5",
FT_AX25, BASE_NONE, NULL, 0x0,
"Via callsign 5", HFILL }
},
{ &hf_ax25_via[ 5 ],
{ "Via 6", "ax25.via6",
FT_AX25, BASE_NONE, NULL, 0x0,
"Via callsign 6", HFILL }
},
{ &hf_ax25_via[ 6 ],
{ "Via 7", "ax25.via7",
FT_AX25, BASE_NONE, NULL, 0x0,
"Via callsign 7", HFILL }
},
{ &hf_ax25_via[ 7 ],
{ "Via 8", "ax25.via8",
FT_AX25, BASE_NONE, NULL, 0x0,
"Via callsign 8", HFILL }
},
{ &hf_ax25_ctl,
{ "Control", "ax25.ctl",
FT_UINT8, BASE_HEX, NULL, 0x0,
"Control field", HFILL }
},
{ &hf_ax25_n_r,
{ "n(r)", "ax25.ctl.n_r",
FT_UINT8, BASE_DEC, NULL, XDLC_N_R_MASK,
NULL, HFILL }
},
{ &hf_ax25_n_s,
{ "n(s)", "ax25.ctl.n_s",
FT_UINT8, BASE_DEC, NULL, XDLC_N_S_MASK,
NULL, HFILL }
},
{ &hf_ax25_p,
{ "Poll", "ax25.ctl.p",
FT_BOOLEAN, 8, TFS(&tfs_set_notset), XDLC_P_F,
NULL, HFILL }
},
{ &hf_ax25_f,
{ "Final", "ax25.ctl.f",
FT_BOOLEAN, 8, TFS(&tfs_set_notset), XDLC_P_F,
NULL, HFILL }
},
{ &hf_ax25_ftype_s,
{ "Frame type", "ax25.ctl.ftype_s",
FT_UINT8, BASE_HEX, VALS(stype_vals), XDLC_S_FTYPE_MASK,
NULL, HFILL }
},
{ &hf_ax25_ftype_i,
{ "Frame type", "ax25.ctl.ftype_i",
FT_UINT8, BASE_HEX, VALS(ftype_vals), XDLC_I_MASK,
NULL, HFILL }
},
{ &hf_ax25_ftype_su,
{ "Frame type", "ax25.ctl.ftype_su",
FT_UINT8, BASE_HEX, VALS(ftype_vals), XDLC_S_U_MASK,
NULL, HFILL }
},
{ &hf_ax25_u_cmd,
{ "Frame type", "ax25.ctl.u_cmd",
FT_UINT8, BASE_HEX, VALS(modifier_vals_cmd), XDLC_U_MODIFIER_MASK,
NULL, HFILL }
},
{ &hf_ax25_u_resp,
{ "Frame type", "ax25.ctl.u_resp",
FT_UINT8, BASE_HEX, VALS(modifier_vals_resp), XDLC_U_MODIFIER_MASK,
NULL, HFILL }
},
{ &hf_ax25_pid,
{ "Protocol ID", "ax25.pid",
FT_UINT8, BASE_HEX, VALS(pid_vals), 0x0,
"Protocol identifier", HFILL }
},
};
/* Setup protocol subtree array */
static gint *ett[] = {
&ett_ax25,
&ett_ax25_ctl,
};
/* Register the protocol name and description */
proto_ax25 = proto_register_protocol("Amateur Radio AX.25", "AX.25", "ax25");
/* Register the dissector */
ax25_handle = register_dissector( "ax25", dissect_ax25, proto_ax25 );
/* Required function calls to register the header fields and subtrees used */
proto_register_field_array( proto_ax25, hf, array_length(hf ) );
proto_register_subtree_array(ett, array_length(ett ) );
/* Register dissector table for protocol IDs */
ax25_dissector_table = register_dissector_table("ax25.pid", "AX.25 protocol ID", proto_ax25, FT_UINT8, BASE_HEX);
register_capture_dissector_table("ax25.pid", "AX.25");
ax25_cap_handle = register_capture_dissector("ax25", capture_ax25, proto_ax25);
}
void
proto_reg_handoff_ax25(void)
{
dissector_add_uint("wtap_encap", WTAP_ENCAP_AX25, ax25_handle);
dissector_add_uint("ip.proto", IP_PROTO_AX25, ax25_handle);
capture_dissector_add_uint("wtap_encap", WTAP_ENCAP_AX25, ax25_cap_handle);
}
/*
* 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:
*/
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