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/* packet-discard.c
* Routines for Discard Protocol dissection
*
* Discard specs taken from RFC 863
* https://tools.ietf.org/html/rfc863
*
* Inspiration from packet-chargen.c and packet-data.
*
* Wireshark - Network traffic analyzer
* By Gerald Combs <gerald@wireshark.org>
* Copyright 1998 Gerald Combs
*
* SPDX-License-Identifier: GPL-2.0-or-later
*/
#include "config.h"
#include <epan/packet.h>
#include <epan/prefs.h>
#include <wsutil/wsgcrypt.h>
#include <wsutil/to_str.h>
#define DISCARD_PORT_UDP 9
#define DISCARD_PORT_TCP 9
void proto_register_discard(void);
void proto_reg_handoff_discard(void);
static int proto_discard = -1;
static int hf_discard_data = -1;
static int hf_discard_text = -1;
static int hf_discard_md5_hash = -1;
static int hf_discard_len = -1;
static gboolean show_as_text = FALSE;
static gboolean generate_md5_hash = FALSE;
static gint ett_discard = -1;
/* dissect_discard - dissects discard packet data
* tvb - tvbuff for packet data (IN)
* pinfo - packet info
* proto_tree - resolved protocol tree
*/
static int
dissect_discard(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, void* dissector_data _U_)
{
proto_tree* discard_tree;
proto_item* ti;
guint32 len;
guint32 cap_len;
col_set_str(pinfo->cinfo, COL_PROTOCOL, "DISCARD");
if (show_as_text) {
col_set_str(pinfo->cinfo, COL_INFO, "Discard: ");
} else {
col_set_str(pinfo->cinfo, COL_INFO, "Discard");
}
ti = proto_tree_add_item(tree, proto_discard, tvb, 0, -1, ENC_NA);
discard_tree = proto_item_add_subtree(ti, ett_discard);
len = tvb_reported_length(tvb);
cap_len = tvb_captured_length(tvb);
proto_tree_add_item(discard_tree, hf_discard_data, tvb, 0, -1, ENC_NA);
if (show_as_text) {
char *display_str;
proto_tree_add_item_ret_display_string(discard_tree, hf_discard_text, tvb, 0, -1, ENC_ASCII, pinfo->pool, &display_str);
col_append_str(pinfo->cinfo, COL_INFO, display_str);
}
if (generate_md5_hash) {
const guint8 *cp;
guint8 digest[HASH_MD5_LENGTH];
const gchar *digest_string;
cp = tvb_get_ptr(tvb, 0, cap_len);
gcry_md_hash_buffer(GCRY_MD_MD5, digest, cp, cap_len);
digest_string = bytes_to_str_punct(pinfo->pool, digest, HASH_MD5_LENGTH, '\0');
ti = proto_tree_add_string(discard_tree, hf_discard_md5_hash, tvb, 0, 0, digest_string);
proto_item_set_generated(ti);
}
ti = proto_tree_add_uint(discard_tree, hf_discard_len, tvb, 0, 0, len);
proto_item_set_generated(ti);
if(len > cap_len) {
/*
* Trigger _ws.short, e.g. [Packet size limited during capture: DISCARD truncated]
*/
tvb_get_ptr(tvb, 0, len);
}
return cap_len;
}
void
proto_register_discard(void)
{
static hf_register_info hf[] = {
{ &hf_discard_data, {
"Data", "discard.data",
FT_BYTES, BASE_NONE, NULL, 0,
NULL, HFILL }
},
{ &hf_discard_text, {
"Text", "discard.text",
FT_STRING, BASE_NONE, NULL, 0,
NULL, HFILL }
},
{ &hf_discard_md5_hash, {
"Payload MD5 hash", "discard.md5_hash",
FT_STRING, BASE_NONE, NULL, 0,
NULL, HFILL }
},
{ &hf_discard_len, {
"Reported Length", "discard.len",
FT_UINT32, BASE_DEC, NULL, 0,
NULL, HFILL }
},
};
static gint *ett[] = {
&ett_discard,
};
module_t *module_data;
proto_discard = proto_register_protocol("Discard Protocol", "DISCARD", "discard");
proto_register_field_array(proto_discard, hf, array_length(hf));
proto_register_subtree_array(ett, array_length(ett));
module_data = prefs_register_protocol(proto_discard, NULL);
prefs_register_bool_preference(module_data,
"show_as_text",
"Show data as text",
"Show data as text in the Packet Details pane",
&show_as_text);
prefs_register_bool_preference(module_data,
"md5_hash",
"Generate MD5 hash",
"Whether or not MD5 hashes should be generated and shown for each payload.",
&generate_md5_hash);
}
void
proto_reg_handoff_discard(void)
{
dissector_handle_t discard_handle;
discard_handle = create_dissector_handle(dissect_discard, proto_discard);
dissector_add_uint_with_preference("udp.port", DISCARD_PORT_UDP, discard_handle);
dissector_add_uint_with_preference("tcp.port", DISCARD_PORT_TCP, discard_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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