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wireshark/epan/dissectors/packet-pw-fr.c

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/* packet-pw-fr.c
* Routines for Frame Relay MPLS PW dissection as per RFC4619.
* Copyright 2009, Dmitry Trebich, Artem Tamazov <artem.tamazov@tellabs.com>
*
* Wireshark - Network traffic analyzer
* By Gerald Combs <gerald@wireshark.org>
* Copyright 1998 Gerald Combs
*
* SPDX-License-Identifier: GPL-2.0-or-later
*
* History:
* ---------------------------------
* 18.03.2009 initial implementation
* - FR DLCI mode
* Not supported yet:
* - Correct FR decode for encapsulations which contain fragmented FR frames.
* - FR DLCI Martini (legacy) mode (i.e. legacy CW).
*/
#include "config.h"
#include <epan/packet.h>
#include <epan/expert.h>
#include "packet-mpls.h"
void proto_register_pw_fr(void);
void proto_reg_handoff_pw_fr(void);
static gint proto_encaps = -1;
static gint ett_encaps = -1;
/* static int hf_pw_fr = -1; */
static int hf_cw_bits03 = -1;
static int hf_cw_fecn = -1;
static int hf_cw_becn = -1;
static int hf_cw_de = -1;
static int hf_cw_cr = -1;
static int hf_cw_frg = -1;
static int hf_cw_len = -1;
static int hf_cw_seq = -1;
static int hf_cw_padding = -1;
static expert_field ei_payload_size_invalid = EI_INIT;
static expert_field ei_cw_bits03 = EI_INIT;
static expert_field ei_cw_packet_size_too_small = EI_INIT;
static const value_string vals_frg[] = {
{ 0x0, "Unfragmented" },
{ 0x1, "First fragment" },
{ 0x2, "Last fragment" },
{ 0x3, "Intermediate fragment" },
{ 0, NULL }
};
static dissector_handle_t fr_stripped_address_handle;
static dissector_handle_t pw_fr_mpls_handle;
static int
dissect_pw_fr( tvbuff_t * tvb, packet_info * pinfo, proto_tree * tree, void* data _U_ )
{
gint packet_size;
gint payload_size;
gint payload_padding;
const int encaps_size = 4; /*encapsulation consists of mandatory CW only*/
enum {
PQ_CW_BAD = 0x001
,PQ_CW_BAD_BITS03 = 0x002
,PQ_CW_BAD_LEN_GT_PACKET = 0x004
,PQ_CW_BAD_LEN_MUST_BE_ZERO = 0x008
,PQ_CW_BAD_LEN_MUST_BE_NONZERO = 0x010
,PQ_PAYLOAD_SIZE_ZERO = 0x020
};
int packet_quality;
packet_size = tvb_reported_length_remaining(tvb, 0);
if (packet_size < encaps_size)
{
{
proto_item *item;
item = proto_tree_add_item(tree, proto_encaps, tvb, 0, -1, ENC_NA);
expert_add_info_format(pinfo, item, &ei_cw_packet_size_too_small,
"PW packet (%d) is smaller than PW encapsulation header (%d)",
(int)packet_size,(int)encaps_size);
}
col_set_str(pinfo->cinfo, COL_PROTOCOL, "FR PW");
col_set_str(pinfo->cinfo, COL_INFO, "Malformed: PW packet < PW encapsulation header");
return 1;
}
if (dissect_try_cw_first_nibble(tvb,pinfo,tree))
{
return tvb_captured_length(tvb);
}
/* check how "good" is this packet */
/* also decide payload length from packet size and CW */
packet_quality = 0;
if (0 != (tvb_get_guint8(tvb, 0) & 0xf0 /*bits03*/))
{
packet_quality |= PQ_CW_BAD + PQ_CW_BAD_BITS03;
}
{
/* RFC4619:
* [ If the frame's length (defined as the
* length of the layer 2 payload plus the length of the control word)
* is less than 64 octets, the length field MUST be set to the PW
* payload length. Otherwise, the length field MUST be set to zero. ]
*
* Note difference from RFC4385 which states that:
* [..the length field MUST be set to the length of the PW payload
* *plus* the length of the *PWMCW*. ]
*/
int cw_len;
gint payload_size_packet; /*derived from packet size*/
cw_len = tvb_get_guint8(tvb, 1) & 0x3f;
payload_size_packet = packet_size - encaps_size;
/*
* Initial assumptions.
*/
payload_size = payload_size_packet;
payload_padding = 0;
if (payload_size_packet < 64)
{
gint payload_size_cw; /*derived from cw*/
payload_size_cw = cw_len; /*RFC4619-specific*/
if (payload_size_cw == 0)
{
packet_quality |= PQ_CW_BAD + PQ_CW_BAD_LEN_MUST_BE_NONZERO;
}
else if (payload_size_cw > payload_size_packet)
{
packet_quality |= PQ_CW_BAD + PQ_CW_BAD_LEN_GT_PACKET;
}
else /* ok */
{
payload_size = payload_size_cw;
payload_padding = payload_size_packet - payload_size_cw; /* >=0 */
}
}
else /* payload_size_packet >= 64 */
{
if (cw_len != 0)
{
packet_quality |= PQ_CW_BAD + PQ_CW_BAD_LEN_MUST_BE_ZERO;
}
}
}
if (payload_size == 0)
{
packet_quality |= PQ_PAYLOAD_SIZE_ZERO;
}
col_set_str(pinfo->cinfo, COL_PROTOCOL, "FR PW");
col_clear(pinfo->cinfo, COL_INFO);
if (packet_quality & PQ_CW_BAD)
{
col_set_str(pinfo->cinfo, COL_INFO, "CW:Malformed, ");
}
col_append_fstr(pinfo->cinfo, COL_INFO, "%d payload octets", (int)payload_size);
if (payload_padding != 0)
{
col_append_fstr(pinfo->cinfo, COL_INFO, ", %d padding", (int)payload_padding);
}
{
proto_tree* subtree;
proto_item* item_headline;
proto_item* item;
item_headline = proto_tree_add_item(tree, proto_encaps, tvb, 0, 4, ENC_NA);
proto_item_append_text(item_headline, ": 0x%.8" PRIx32, tvb_get_ntohl(tvb, 0));
subtree = proto_item_add_subtree(item_headline, ett_encaps);
if (packet_quality & PQ_CW_BAD_BITS03) /*display only if value is wrong*/
{
item = proto_tree_add_item(subtree, hf_cw_bits03, tvb, 0, 1, ENC_BIG_ENDIAN);
expert_add_info(pinfo, item, &ei_cw_bits03);
}
proto_tree_add_item( subtree, hf_cw_fecn, tvb, 0, 1, ENC_BIG_ENDIAN );
proto_tree_add_item( subtree, hf_cw_becn, tvb, 0, 1, ENC_BIG_ENDIAN );
proto_tree_add_item( subtree, hf_cw_de, tvb, 0, 1, ENC_BIG_ENDIAN );
proto_tree_add_item( subtree, hf_cw_cr, tvb, 0, 1, ENC_BIG_ENDIAN );
proto_tree_add_item( subtree, hf_cw_frg, tvb, 1, 1, ENC_BIG_ENDIAN );
item = proto_tree_add_item( subtree, hf_cw_len, tvb, 1, 1, ENC_BIG_ENDIAN );
if (packet_quality & PQ_CW_BAD_LEN_GT_PACKET)
{
expert_add_info_format(pinfo, item, &ei_payload_size_invalid,
"Bad Length: greater than FR payload size (%d)",
(int)payload_size);
}
if (packet_quality & PQ_CW_BAD_LEN_MUST_BE_NONZERO)
{
expert_add_info_format(pinfo, item, &ei_payload_size_invalid,
"Bad Length: must be non-zero if FR PW packet size (%d) is < 64",
(int)(payload_size+encaps_size));
}
if (packet_quality & PQ_CW_BAD_LEN_MUST_BE_ZERO)
{
expert_add_info_format(pinfo, item, &ei_payload_size_invalid,
"Bad Length: must be 0 if FR PW packet size (%d) is >= 64",
(int)(payload_size+encaps_size));
}
proto_tree_add_item( subtree, hf_cw_seq, tvb, 2, 2, ENC_BIG_ENDIAN );
if (payload_padding > 0)
{
proto_tree_add_item(subtree, hf_cw_padding, tvb,
encaps_size+payload_size, payload_padding, ENC_NA);
}
if (packet_quality & PQ_PAYLOAD_SIZE_ZERO)
{
expert_add_info_format(pinfo, item_headline, &ei_payload_size_invalid,
"FR payload size must be non-zero");
}
}
if (payload_size > 0)
{
tvbuff_t *tvb_payload;
tvb_payload = tvb_new_subset_length(tvb, encaps_size, payload_size);
call_dissector( fr_stripped_address_handle, tvb_payload, pinfo, tree );
}
return tvb_captured_length(tvb);
}
void
proto_register_pw_fr(void)
{
static hf_register_info hf[] = {
{&hf_cw_bits03 ,{"Bits 0 to 3" ,"pwfr.bits03" ,FT_UINT8 ,BASE_HEX
,NULL ,0xf0 ,NULL
,HFILL }},
{&hf_cw_fecn ,{"FR FECN" ,"pwfr.fecn" ,FT_UINT8 ,BASE_DEC
,NULL ,0x08 ,"FR Forward Explicit Congestion Notification bit"
,HFILL}},
{&hf_cw_becn ,{"FR BECN" ,"pwfr.becn" ,FT_UINT8 ,BASE_DEC
,NULL ,0x04 ,"FR Backward Explicit Congestion Notification bit"
,HFILL}},
{&hf_cw_de ,{"FR DE bit" ,"pwfr.de" ,FT_UINT8 ,BASE_DEC
,NULL ,0x02 ,"FR Discard Eligibility bit"
,HFILL}},
{&hf_cw_cr ,{"FR Frame C/R" ,"pwfr.cr" ,FT_UINT8 ,BASE_DEC
,NULL ,0x01 ,"FR frame Command/Response bit"
,HFILL}},
{&hf_cw_frg ,{"Fragmentation" ,"pwfr.frag" ,FT_UINT8 ,BASE_DEC
,VALS(vals_frg) ,0xc0 ,NULL
,HFILL}},
{&hf_cw_len ,{"Length" ,"pwfr.length" ,FT_UINT8 ,BASE_DEC
,NULL ,0x3f ,NULL
,HFILL}},
{&hf_cw_seq ,{"Sequence number" ,"pwfr.seqno" ,FT_UINT16 ,BASE_DEC
,NULL ,0 ,NULL
,HFILL}},
{&hf_cw_padding,{"Padding" ,"pwfr.padding" ,FT_BYTES, BASE_NONE
,NULL ,0 ,NULL
,HFILL}}
};
static gint *ett[] = {
&ett_encaps
};
static ei_register_info ei[] = {
{ &ei_cw_packet_size_too_small, { "pwfr.packet_size_too_small", PI_MALFORMED, PI_ERROR, "PW packet is smaller than PW encapsulation header", EXPFILL }},
{ &ei_cw_bits03, { "pwfr.cw.bits03.not_zero", PI_MALFORMED, PI_ERROR, "Bits 0..3 of Control Word must be 0", EXPFILL }},
{ &ei_payload_size_invalid, { "pwfr.payload.size_invalid", PI_MALFORMED, PI_ERROR, "Bad Length: greater than FR payload size", EXPFILL }},
};
expert_module_t* expert_pwfr;
proto_encaps = proto_register_protocol( "PW Frame Relay DLCI Control Word",
"Frame Relay DLCI PW",
"pwfr");
proto_register_field_array(proto_encaps, hf, array_length(hf));
proto_register_subtree_array(ett, array_length(ett));
expert_pwfr = expert_register_protocol(proto_encaps);
expert_register_field_array(expert_pwfr, ei, array_length(ei));
pw_fr_mpls_handle = register_dissector("pw_fr", dissect_pw_fr, proto_encaps );
}
void
proto_reg_handoff_pw_fr(void)
{
dissector_add_for_decode_as("mpls.label", pw_fr_mpls_handle);
fr_stripped_address_handle = find_dissector_add_dependency("fr_stripped_address", proto_encaps);
}
/*
* 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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