Exemplo n.º 1
0
static void
dissect_pw_eth_cw(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree)
{
        proto_tree *pw_eth_tree = NULL;
        proto_item *ti = NULL;
        tvbuff_t *next_tvb = NULL;
        guint16 sequence_number = 0;
        
        if (tvb_reported_length_remaining(tvb, 0) < 4) {
                if (tree)
                        proto_tree_add_text(tree, tvb, 0, -1, 
                                            "Error processing Message");
                return;
        }

        if (dissect_try_cw_first_nibble(tvb, pinfo, tree)) 
                return;

        sequence_number = tvb_get_ntohs(tvb, 2);
        if (tree) {
                ti = proto_tree_add_boolean(tree, hf_pw_eth_cw, 
                                            tvb, 0, 0, TRUE);
                PROTO_ITEM_SET_HIDDEN(ti);
                ti = proto_tree_add_item(tree, proto_pw_eth_cw, 
                                         tvb, 0, 4, FALSE);
                pw_eth_tree = proto_item_add_subtree(ti, ett_pw_eth);
                if (pw_eth_tree == NULL)
                        return;
                proto_tree_add_uint_format(pw_eth_tree, 
                                           hf_pw_eth_cw_sequence_number,
                                           tvb, 2, 2, sequence_number,
                                           "Sequence Number: %d", 
                                           sequence_number);
        }
        next_tvb = tvb_new_subset_remaining(tvb, 4);
        {
                /*
                 * When Ethernet frames being decoded, pinfo->ethertype is extracted 
                 * from the top-level Ethernet frame. Dissection of Ethernet PW payload
                 * overwrites this value as the same dissector is invoked again.
                 * This may lead to undesired behavior (like disappearance of "Link"
                 * tab from the "Decode as" menu).
                 *
                 * Let's save/restore ethertype. --ATA 
                 *
                 * XXX it looks that more pinfo members (or even the whole pinfo) 
                 * XXX should be saved/restored in PW cases. Multilayer encapsulations, 
                 * XXX like ethernet/mpls/ethernet-pw/ip/vlan, may lead to undesired 
                 * XXX changes if pinfo->ipproto, ptype etc.
                 */
                guint32 etype_save = pinfo->ethertype;
                call_dissector(eth_withoutfcs_handle, next_tvb, pinfo, tree);
                pinfo->ethertype = etype_save;
        }
}
Exemplo n.º 2
0
static
void dissect_pw_satop(tvbuff_t * tvb_original
					,packet_info * pinfo
					,proto_tree * tree
					,pwc_demux_type_t demux)
{
	const int encaps_size = 4; /*RTP header in encapsulation is not supported yet*/
	gint      packet_size;
	gint      payload_size;
	gint      padding_size;
	int properties;

	enum {
		PAY_NO_IDEA = 0
		,PAY_LIKE_E1
		,PAY_LIKE_T1
		,PAY_LIKE_E3_T3
		,PAY_LIKE_OCTET_ALIGNED_T1
	} payload_properties;

	packet_size = tvb_reported_length_remaining(tvb_original, 0);
	/*
	 * FIXME
	 * "4" below should be replaced by something like "min_packet_size_this_dissector"
	 * Also call to dissect_try_cw_first_nibble() should be moved before this block
	 */
	if (packet_size < 4) /* 4 is smallest size which may be sensible (for PWACH dissector) */
	{
		proto_item  *item;
		item = proto_tree_add_item(tree, proto, tvb_original, 0, -1, ENC_NA);
		expert_add_info_format(pinfo, item, &ei_cw_packet_size_too_small,
				       "PW packet size (%d) is too small to carry sensible information"
				       ,(int)packet_size);
		col_set_str(pinfo->cinfo, COL_PROTOCOL, shortname);
		col_set_str(pinfo->cinfo, COL_INFO, "Malformed: PW packet is too small");
		return;
	}

	switch (demux)
	{
	case PWC_DEMUX_MPLS:
		if (dissect_try_cw_first_nibble(tvb_original, pinfo, tree))
		{
			return;
		}
		break;
	case PWC_DEMUX_UDP:
		break;
	default:
		DISSECTOR_ASSERT_NOT_REACHED();
		return;
	}

	/* check how "good" is this packet */
	/* also decide payload length from packet size and CW */
	properties = 0;
	if (0 != (tvb_get_guint8(tvb_original, 0) & 0xf0 /*bits03*/))
	{
		properties |= PWC_CW_BAD_BITS03;
	}
	if (0 != (tvb_get_guint8(tvb_original, 0) & 0x03 /*rsv*/))
	{
		properties |= PWC_CW_BAD_RSV;
	}
	if (0 != (tvb_get_guint8(tvb_original, 1) & 0xc0 /*frag*/))
	{
		properties |= PWC_CW_BAD_FRAG;
	}
	{
		/* RFC4553:
		 * [...MAY be used to carry the length of the SAToP
		 * packet (defined as the size of the SAToP header + the payload
		 * size) if it is less than 64 bytes, and MUST be set to zero
		 * otherwise... ]
		 *
		 * Note that this differs from RFC4385's definition of length:
		 * [ If the MPLS payload is less than 64 bytes, the length field
		 * MUST be set to the length of the PW payload...]
		 *
		 * We will use RFC4553's definition here.
		 */
		int  cw_len;
		gint payload_size_from_packet;

		cw_len = tvb_get_guint8(tvb_original, 1) & 0x3f;
		payload_size_from_packet = packet_size - encaps_size;
		if (cw_len != 0)
		{
			gint payload_size_from_cw;
			payload_size_from_cw = cw_len - encaps_size;
			/*
			 * Assumptions for error case,
			 * will be overwritten if no errors found:
			 */
			payload_size = payload_size_from_packet;
			padding_size = 0;

			if (payload_size_from_cw < 0)
			{
				properties |= PWC_CW_BAD_PAYLEN_LT_0;
			}
			else if (payload_size_from_cw > payload_size_from_packet)
			{
				properties |= PWC_CW_BAD_PAYLEN_GT_PACKET;
			}
			else if (payload_size_from_packet >= 64)
			{
				properties |= PWC_CW_BAD_LEN_MUST_BE_0;
			}
			else /* ok */
			{
				payload_size = payload_size_from_cw;
				padding_size = payload_size_from_packet - payload_size_from_cw; /* >=0 */
			}
		}
		else
		{
			payload_size = payload_size_from_packet;
			padding_size = 0;
		}
	}
	if (payload_size == 0)
	{
		/*
		 * As CW.L it indicates that PW payload is invalid, dissector should
		 * not blame packets with bad payload (including "bad" or "strange" SIZE of
		 * payload) when L bit is set.
		 */
		if (0 == (tvb_get_guint8(tvb_original, 0) & 0x08 /*L bit*/))
		{
			properties |= PWC_PAY_SIZE_BAD;
		}
	}

	/* guess about payload type */
	if (payload_size == 256)
	{
		payload_properties = PAY_LIKE_E1;
	}
	else if (payload_size == 192)
	{
		payload_properties = PAY_LIKE_T1;
	}
	else if (payload_size == 1024)
	{
		payload_properties = PAY_LIKE_E3_T3;
	}
	else if ((payload_size != 0) && (payload_size % 25 == 0))
	{
		payload_properties = PAY_LIKE_OCTET_ALIGNED_T1;
	}
	else
	{
		payload_properties = PAY_NO_IDEA; /*we do not have any ideas about payload type*/
	}

	/* fill up columns*/
	col_set_str(pinfo->cinfo, COL_PROTOCOL, shortname);
	col_clear(pinfo->cinfo, COL_INFO);
	if (properties & PWC_ANYOF_CW_BAD)
	{
		col_set_str(pinfo->cinfo, COL_INFO, "CW:Bad, ");
	}

	if (properties & PWC_PAY_SIZE_BAD)
	{
		col_append_str(pinfo->cinfo, COL_INFO, "Payload size:0 (Bad)");
	}
	else
	{
		col_append_fstr(pinfo->cinfo, COL_INFO, "TDM octets:%d", (int)payload_size);
	}

	if (padding_size != 0)
	{
		col_append_fstr(pinfo->cinfo, COL_INFO, ", Padding:%d", (int)padding_size);
	}


	{
		proto_item* item;
		item = proto_tree_add_item(tree, proto, tvb_original, 0, -1, ENC_NA);
		pwc_item_append_cw(item,tvb_get_ntohl(tvb_original, 0),TRUE);
		pwc_item_append_text_n_items(item,(int)payload_size,"octet");
		{
			proto_tree* tree2;
			tree2 = proto_item_add_subtree(item, ett);
			{
				tvbuff_t* tvb;
				proto_item* item2;
				tvb = tvb_new_subset_length(tvb_original, 0, PWC_SIZEOF_CW);
				item2 = proto_tree_add_item(tree2, hf_cw, tvb, 0, -1, ENC_NA);
				pwc_item_append_cw(item2, tvb_get_ntohl(tvb, 0),FALSE);
				{
					proto_tree* tree3;
					tree3 = proto_item_add_subtree(item2, ett);
					{
						proto_item* item3;
						if (properties & PWC_CW_BAD_BITS03) /*display only if value is wrong*/
						{
							item3 = proto_tree_add_item(tree3, hf_cw_bits03, tvb, 0, 1, ENC_BIG_ENDIAN);
							expert_add_info(pinfo, item3, &ei_cw_bits03);
						}

						proto_tree_add_item(tree3, hf_cw_l  , tvb, 0, 1, ENC_BIG_ENDIAN);
						proto_tree_add_item(tree3, hf_cw_r  , tvb, 0, 1, ENC_BIG_ENDIAN);

						item3 = proto_tree_add_item(tree3, hf_cw_rsv, tvb, 0, 1, ENC_BIG_ENDIAN);
						if (properties & PWC_CW_BAD_RSV)
						{
							expert_add_info(pinfo, item3, &ei_cw_rsv);
						}

						item3 = proto_tree_add_item(tree3, hf_cw_frg, tvb, 1, 1, ENC_BIG_ENDIAN);
						if (properties & PWC_CW_BAD_FRAG)
						{
							expert_add_info(pinfo, item3, &ei_cw_frg);
						}

						item3 = proto_tree_add_item(tree3, hf_cw_len, tvb, 1, 1, ENC_BIG_ENDIAN);
						if (properties & PWC_CW_BAD_PAYLEN_LT_0)
						{
							expert_add_info_format(pinfo, item3, &ei_payload_size_invalid,
								"Bad Length: too small, must be > %d",
								(int)encaps_size);
						}
						if (properties & PWC_CW_BAD_PAYLEN_GT_PACKET)
						{
							expert_add_info_format(pinfo, item3, &ei_payload_size_invalid,
								"Bad Length: must be <= than PSN packet size (%d)",
								(int)packet_size);
						}
						if (properties & PWC_CW_BAD_LEN_MUST_BE_0)
						{
							expert_add_info_format(pinfo, item3, &ei_payload_size_invalid,
								"Bad Length: must be 0 if SAToP packet size (%d) is > 64",
								(int)packet_size);
						}

						proto_tree_add_item(tree3, hf_cw_seq, tvb, 2, 2, ENC_BIG_ENDIAN);
					}
				}
			}
		}

		/* payload */
		if (properties & PWC_PAY_SIZE_BAD)
		{
			expert_add_info_format(pinfo, item, &ei_payload_size_invalid,
				"SAToP payload: none found. Size of payload must be <> 0");
		}
		else if (payload_size == 0)
		{
			expert_add_info(pinfo, item, &ei_payload_size_invalid_undecoded);
		}
		else
		{

			proto_tree* tree2;
			tree2 = proto_item_add_subtree(item, ett);
			{
				proto_item* item2;
				tvbuff_t* tvb;
				tvb = tvb_new_subset_length(tvb_original, PWC_SIZEOF_CW, payload_size);
				item2 = proto_tree_add_item(tree2, hf_payload, tvb, 0, -1, ENC_NA);
				pwc_item_append_text_n_items(item2,(int)payload_size,"octet");
				{
					proto_tree* tree3;
					const char* s;
					switch(payload_properties)
					{
					case PAY_LIKE_E1:
						s = " (looks like E1)";
						break;
					case PAY_LIKE_T1:
						s = " (looks like T1)";
						break;
					case PAY_LIKE_E3_T3:
						s = " (looks like E3/T3)";
						break;
					case PAY_LIKE_OCTET_ALIGNED_T1:
						s = " (looks like octet-aligned T1)";
						break;
					case PAY_NO_IDEA:
					default:
						s = "";
						break;
					}
					proto_item_append_text(item2, "%s", s);
					tree3 = proto_item_add_subtree(item2, ett);
					call_data_dissector(tvb, pinfo, tree3);
					item2 = proto_tree_add_int(tree3, hf_payload_l, tvb, 0, 0
						,(int)payload_size); /* allow filtering */
					PROTO_ITEM_SET_HIDDEN(item2);
				}
			}
		}

		/* padding */
		if (padding_size > 0)
		{
			proto_tree* tree2;
			tree2 = proto_item_add_subtree(item, ett);
			{
				tvbuff_t* tvb;
				tvb = tvb_new_subset(tvb_original, PWC_SIZEOF_CW + payload_size, padding_size, -1);
				call_dissector(pw_padding_handle, tvb, pinfo, tree2);
			}
		}
	}
	return;
}
Exemplo n.º 3
0
static
void dissect_pw_cesopsn( tvbuff_t * tvb_original
						,packet_info * pinfo
						,proto_tree * tree
						,pwc_demux_type_t demux)
{
	const int encaps_size = 4; /*RTP header in encapsulation is not supported yet*/
	gint      packet_size;
	gint      payload_size;
	gint      padding_size;
	int properties;

	packet_size = tvb_reported_length_remaining(tvb_original, 0);

	/*
	 * FIXME
	 * "4" below should be replaced by something like "min_packet_size_this_dissector"
	 * Also call to dissect_try_cw_first_nibble() should be moved before this block
	 */
	if (packet_size < 4) /* 4 is smallest size which may be sensible (for PWACH dissector) */
	{
		proto_item  *item;
		item = proto_tree_add_item(tree, proto, tvb_original, 0, -1, ENC_NA);
		expert_add_info_format(pinfo, item, &ei_packet_size_too_small,
				       "PW packet size (%d) is too small to carry sensible information"
				       ,(int)packet_size);
		col_set_str(pinfo->cinfo, COL_PROTOCOL, shortname);
		col_set_str(pinfo->cinfo, COL_INFO, "Malformed: PW packet is too small");
		return;
	}

	switch (demux)
	{
	case PWC_DEMUX_MPLS:
		if (dissect_try_cw_first_nibble(tvb_original, pinfo, tree))
		{
			return;
		}
		break;
	case PWC_DEMUX_UDP:
		break;
	default:
		DISSECTOR_ASSERT_NOT_REACHED();
		return;
	}

	/* check how "good" is this packet */
	/* also decide payload length from packet size and CW */
	properties = PWC_PACKET_PROPERTIES_T_INITIALIZER;
	if (0 != (tvb_get_guint8(tvb_original, 0) & 0xf0 /*bits03*/))
	{
		properties |= PWC_CW_BAD_BITS03;
	}
	if (0 != (tvb_get_guint8(tvb_original, 1) & 0xc0 /*frag*/))
	{
		properties |= PWC_CW_BAD_FRAG;
	}
	{
		/* RFC5086:
		 * [LEN (bits (10 to 15) MAY be used to carry the length of the CESoPSN
		 * packet (defined as the size of the CESoPSN header + the payload size)
		 * if it is less than 64 bytes, and MUST be set to zero otherwise.
		 * Note:  If fixed RTP header is used in the encapsulation, it is
		 * considered part of the CESoPSN header.]
		 *
		 * Note that this differs from RFC4385's definition of length:
		 * [ If the MPLS payload is less than 64 bytes, the length field
		 * MUST be set to the length of the PW payload...]
		 *
		 * We will use RFC5086's definition here.
		 */
		int  cw_len;
		gint payload_size_from_packet;

		cw_len = tvb_get_guint8(tvb_original, 1) & 0x3f;
		payload_size_from_packet = packet_size - encaps_size;
		if (cw_len != 0)
		{
			gint payload_size_from_cw;
			payload_size_from_cw = cw_len - encaps_size;
			/*
			 * Assumptions for error case,
			 * will be overwritten if no errors found:
			 */
			payload_size = payload_size_from_packet;
			padding_size = 0;

			if (payload_size_from_cw < 0)
			{
				properties |= PWC_CW_BAD_PAYLEN_LT_0;
			}
			else if (payload_size_from_cw > payload_size_from_packet)
			{
				properties |= PWC_CW_BAD_PAYLEN_GT_PACKET;
			}
			else if (payload_size_from_packet >= 64)
			{
				properties |= PWC_CW_BAD_LEN_MUST_BE_0;
			}
			else /* ok */
			{
				payload_size = payload_size_from_cw;
				padding_size = payload_size_from_packet - payload_size_from_cw; /* >=0 */
			}
		}
		else
		{
			payload_size = payload_size_from_packet;
			padding_size = 0;
		}
	}

	{
		guint8 cw_lm;
		cw_lm = tvb_get_guint8(tvb_original, 0) & 0x0b /*l+mod*/;
		if (NULL == try_val_to_str(cw_lm, vals_cw_lm))
		{
			properties |= PWC_CW_SUSPECT_LM;
		}

		{
			guint8 l_bit, m_bits;
			l_bit  = (cw_lm & 0x08) >> 3;
			m_bits = (cw_lm & 0x03) >> 0;
			if ((l_bit == 0 && m_bits == 0x0) /*CESoPSN data packet - normal situation*/
			    ||(l_bit == 0 && m_bits == 0x2) /*CESoPSN data packet - RDI on the AC*/ )
			{
				if ((payload_size == 0) || ((payload_size % 8) != 0))
				{
					properties |= PWC_PAY_SIZE_BAD;
				}
			}
			else if (l_bit == 1 && m_bits == 0x0) /*TDM data is invalid; payload MAY be omitted*/
			{
				/*allow any size of payload*/
			}
			else /*reserved combinations*/
			{
				/*allow any size of payload*/
			}
		}
	}

	/* fill up columns*/
	col_set_str(pinfo->cinfo, COL_PROTOCOL, shortname);
	col_clear(pinfo->cinfo, COL_INFO);
	if (properties & PWC_ANYOF_CW_BAD)
	{
		col_set_str(pinfo->cinfo, COL_INFO, "CW:Bad, ");
	}
	else if (properties & PWC_ANYOF_CW_SUSPECT)
	{
		col_append_str(pinfo->cinfo, COL_INFO, "CW:Suspect, ");
	}

	if (properties & PWC_PAY_SIZE_BAD)
	{
		col_append_str(pinfo->cinfo, COL_INFO, "Payload size:Bad, ");
	}

	col_append_fstr(pinfo->cinfo, COL_INFO, "TDM octets:%d", (int)payload_size);

	if (padding_size != 0)
	{
		col_append_fstr(pinfo->cinfo, COL_INFO, ", Padding:%d", (int)padding_size);
	}

	{
		proto_item* item;
		item = proto_tree_add_item(tree, proto, tvb_original, 0, -1, ENC_NA);
		pwc_item_append_cw(item,tvb_get_ntohl(tvb_original, 0),TRUE);
		pwc_item_append_text_n_items(item,(int)payload_size,"octet");
		{
			proto_tree* tree2;
			tree2 = proto_item_add_subtree(item, ett);
			{
				tvbuff_t* tvb;
				proto_item* item2;
				tvb = tvb_new_subset(tvb_original, 0, PWC_SIZEOF_CW, PWC_SIZEOF_CW);
				item2 = proto_tree_add_item(tree2, hf_cw, tvb, 0, -1, ENC_NA);
				pwc_item_append_cw(item2,tvb_get_ntohl(tvb, 0),FALSE);
				{
					proto_tree* tree3;
					tree3 = proto_item_add_subtree(item, ett);
					{
						proto_item* item3;
						if (properties & PWC_CW_BAD_BITS03) /*display only if value is wrong*/
						{
							item3 = proto_tree_add_item(tree3, hf_cw_bits03, tvb, 0, 1, ENC_BIG_ENDIAN);
							expert_add_info(pinfo, item3, &ei_cw_bits03);
						}

						item3 = proto_tree_add_item(tree3, hf_cw_lm,  tvb, 0, 1, ENC_BIG_ENDIAN);
						if (properties & PWC_CW_SUSPECT_LM)
						{
							expert_add_info(pinfo, item3, &ei_cw_lm);
						}

						proto_tree_add_item(tree3, hf_cw_r, tvb, 0, 1, ENC_BIG_ENDIAN);

						item3 = proto_tree_add_item(tree3, hf_cw_frg, tvb, 1, 1, ENC_BIG_ENDIAN);
						if (properties & PWC_CW_BAD_FRAG)
						{
							expert_add_info(pinfo, item3, &ei_cw_frg);
						}

						item3 = proto_tree_add_item(tree3, hf_cw_len, tvb, 1, 1, ENC_BIG_ENDIAN);
						if (properties & PWC_CW_BAD_PAYLEN_LT_0)
						{
							expert_add_info_format(pinfo, item3, &ei_pref_cw_len,
								"Bad Length: too small, must be > %d",
								(int)encaps_size);
						}
						if (properties & PWC_CW_BAD_PAYLEN_GT_PACKET)
						{
							expert_add_info_format(pinfo, item3, &ei_pref_cw_len,
								"Bad Length: must be <= than PSN packet size (%d)",
								(int)packet_size);
						}
						if (properties & PWC_CW_BAD_LEN_MUST_BE_0)
						{
							expert_add_info_format(pinfo, item3, &ei_pref_cw_len,
								"Bad Length: must be 0 if CESoPSN packet size (%d) is > 64",
								(int)packet_size);
						}

						proto_tree_add_item(tree3, hf_cw_seq, tvb, 2, 2, ENC_BIG_ENDIAN);

					}
				}
			}
		}

		/* payload */
		if (payload_size == 0)
		{
			if (properties & PWC_PAY_SIZE_BAD)
			{
				expert_add_info_format(pinfo, item, &ei_payload_size_invalid_error,
					"CESoPSN payload: none found. Size of payload must be <> 0");
			}
			else
			{
				expert_add_info_format(pinfo, item, &ei_payload_size_invalid_undecoded,
					"CESoPSN payload: omitted to conserve bandwidth");
			}
		}
		else
		{
			proto_tree* tree2;
			tree2 = proto_item_add_subtree(item, ett);
			{
				proto_item* item2;
				tvbuff_t* tvb;
				tvb = tvb_new_subset(tvb_original, PWC_SIZEOF_CW, payload_size, payload_size);
				item2 = proto_tree_add_item(tree2, hf_payload, tvb, 0, -1, ENC_NA);
				pwc_item_append_text_n_items(item2,(int)payload_size,"octet");
				if (properties & PWC_PAY_SIZE_BAD)
				{
					expert_add_info_format(pinfo, item2, &ei_payload_size_invalid_error,
						"CESoPSN packet payload size must be multiple of 8");
				}
				tree2 = proto_item_add_subtree(item2, ett);
				call_dissector(data_handle, tvb, pinfo, tree2);
				item2 = proto_tree_add_int(tree2, hf_payload_l, tvb, 0, 0
					,(int)payload_size); /* allow filtering */
				PROTO_ITEM_SET_HIDDEN(item2);
			}
		}

		/* padding */
		if (padding_size > 0)
		{
			proto_tree* tree2;
			tree2 = proto_item_add_subtree(item, ett);
			{
				tvbuff_t* tvb;
				tvb = tvb_new_subset(tvb_original, PWC_SIZEOF_CW + payload_size, padding_size, -1);
				call_dissector(pw_padding_handle, tvb, pinfo, tree2);
			}
		}
	}
	return;
}
Exemplo n.º 4
0
static void
dissect_pw_fr( tvbuff_t * tvb, packet_info * pinfo, proto_tree * tree )
{
	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;
	}

	if (dissect_try_cw_first_nibble(tvb,pinfo,tree))
	{
		return;
	}

	/* 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" G_GINT32_MODIFIER "x", 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);
		}

		(void)proto_tree_add_item( subtree, hf_cw_fecn, tvb, 0, 1, ENC_BIG_ENDIAN );
		(void)proto_tree_add_item( subtree, hf_cw_becn, tvb, 0, 1, ENC_BIG_ENDIAN );
		(void)proto_tree_add_item( subtree, hf_cw_de,   tvb, 0, 1, ENC_BIG_ENDIAN );
		(void)proto_tree_add_item( subtree, hf_cw_cr,   tvb, 0, 1, ENC_BIG_ENDIAN );
		(void)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_text(subtree, tvb,
				encaps_size+payload_size, payload_padding,
				"[Padding: %d octets]",(int)payload_padding);
		}

		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(tvb, encaps_size, payload_size, payload_size);
		call_dissector( fr_stripped_address_handle, tvb_payload, pinfo, tree );
	}
	return;
}