/** Checksums the data. */
static tvbuff_t *
checksum_data(tvbuff_t *tvb, proto_tree *tree)
{
proto_item *hidden_item;
int len = tvb_length(tvb) - 2;
if (len < 0)
return tvb;
if (tree) {
guint16 actual_fcs = tvb_get_letohs(tvb, len);
guint16 calculated_fcs = crc16_ccitt_tvb(tvb, len);
if (calculated_fcs == actual_fcs) {
proto_tree_add_uint_format(tree, hf_sir_fcs,
tvb, len, 2, actual_fcs,
"Frame check sequence: 0x%04x (correct)",
actual_fcs);
} else {
hidden_item = proto_tree_add_boolean(tree,
hf_sir_fcs_bad, tvb, len, 2, TRUE);
PROTO_ITEM_SET_HIDDEN(hidden_item);
proto_tree_add_uint_format(tree, hf_sir_fcs,
tvb, len, 2, actual_fcs,
"Frame check sequence: 0x%04x "
"(incorrect, should be 0x%04x)",
actual_fcs, calculated_fcs);
}
}
return tvb_new_subset_length(tvb, 0, len);
}
static void dissect_srp (tvbuff_t * tvb, packet_info * pinfo, proto_tree * tree)
{
proto_item *srp_item = NULL;
proto_tree *srp_tree = NULL;
proto_item *hidden_item;
guint8 header = tvb_get_guint8(tvb,0);
/* add the 'srp' tree to the main tree */
if (tree) {
srp_item = proto_tree_add_item (tree, proto_srp, tvb, 0, -1, ENC_NA);
srp_tree = proto_item_add_subtree (srp_item, ett_srp);
proto_tree_add_uint(srp_tree,hf_srp_header,tvb,0,1,header);
}
switch( header ) {
case SRP_SRP_COMMAND:
dissect_srp_command(tvb,pinfo,srp_tree);
break;
case SRP_SRP_RESPONSE:
break;
case SRP_NSRP_RESPONSE:
if( srp_tree )
proto_tree_add_item(srp_tree,hf_srp_seqno,tvb,1,1,ENC_BIG_ENDIAN);
break;
default:
break;
}
if( srp_tree ) {
guint16 crc, calc_crc;
guint crc_offset = tvb_reported_length(tvb)-2;
crc = tvb_get_letohs(tvb,-2);
/* crc includes the header */
calc_crc = crc16_ccitt_tvb(tvb,crc_offset);
if( crc == calc_crc ) {
proto_tree_add_uint_format(srp_tree, hf_srp_crc, tvb,
crc_offset, 2, crc,
"CRC: 0x%04x (correct)", crc);
} else {
hidden_item = proto_tree_add_boolean(srp_tree, hf_srp_crc_bad, tvb,
crc_offset, 2, TRUE);
PROTO_ITEM_SET_HIDDEN(hidden_item);
proto_tree_add_uint_format(srp_tree, hf_srp_crc, tvb,
crc_offset, 2, crc,
"CRC: 0x%04x (incorrect, should be 0x%04x)",
crc,
calc_crc);
}
}
}
/*
*******************************************************************************
* DETAILS : Calculate a new FCS-16 given the current FCS-16 and the new data.
*******************************************************************************
*/
static guint16
mtp2_fcs16(tvbuff_t * tvbuff)
{
guint len = tvb_captured_length(tvbuff)-2;
/* Check for Invalid Length */
if (len == 0)
return (0x0000);
return crc16_ccitt_tvb(tvbuff, len);
}
/** Checksums the data. */
static tvbuff_t *
checksum_data(tvbuff_t *tvb, proto_tree *tree)
{
int len = tvb_reported_length(tvb) - 2;
if (len < 0)
return tvb;
proto_tree_add_checksum(tree, tvb, len, hf_sir_fcs, hf_sir_fcs_status, NULL, NULL, crc16_ccitt_tvb(tvb, len),
ENC_LITTLE_ENDIAN, PROTO_CHECKSUM_VERIFY);
return tvb_new_subset_length(tvb, 0, len);
}
static void
dissect_v5dl(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree)
{
proto_tree *v5dl_tree, *addr_tree;
proto_item *v5dl_ti, *addr_ti;
int direction;
guint v5dl_header_len;
guint16 control;
#if 0
proto_tree *checksum_tree;
proto_item *checksum_ti;
guint16 checksum, checksum_calculated;
guint checksum_offset;
#endif
guint16 addr, cr, eah, eal, v5addr;
gboolean is_response = 0;
#if 0
guint length, reported_length;
#endif
tvbuff_t *next_tvb;
const char *srcname = "?";
const char *dstname = "?";
col_set_str(pinfo->cinfo, COL_PROTOCOL, "V5DL");
col_clear(pinfo->cinfo, COL_INFO);
addr = tvb_get_ntohs(tvb, 0);
cr = addr & V5DL_CR;
eal = (addr & V5DL_EAL) >> V5DL_EAL_SHIFT;
eah = (addr & V5DL_EAH) >> V5DL_EAH_SHIFT;
v5addr = (eah << 7) + eal;
v5dl_header_len = 2; /* addr */
direction = pinfo->p2p_dir;
if (pinfo->p2p_dir == P2P_DIR_RECV) {
is_response = cr ? FALSE : TRUE;
srcname = "Network";
dstname = "User";
}
else if (pinfo->p2p_dir == P2P_DIR_SENT) {
is_response = cr ? TRUE : FALSE;
srcname = "User";
dstname = "Network";
}
col_set_str(pinfo->cinfo, COL_RES_DL_SRC, srcname);
col_set_str(pinfo->cinfo, COL_RES_DL_DST, dstname);
if (tree) {
proto_item *direction_ti;
v5dl_ti = proto_tree_add_item(tree, proto_v5dl, tvb, 0, -1,
ENC_NA);
v5dl_tree = proto_item_add_subtree(v5dl_ti, ett_v5dl);
/*
* Don't show the direction if we don't know it.
*/
if (direction != P2P_DIR_UNKNOWN) {
direction_ti = proto_tree_add_uint(v5dl_tree, hf_v5dl_direction,
tvb, 0, 0, pinfo->p2p_dir);
PROTO_ITEM_SET_GENERATED(direction_ti);
}
addr_ti = proto_tree_add_uint(v5dl_tree, hf_v5dl_ef, tvb,
0, 2, v5addr);
addr_tree = proto_item_add_subtree(addr_ti, ett_v5dl_address);
proto_tree_add_uint(addr_tree, hf_v5dl_eah, tvb, 0, 1, addr);
proto_tree_add_uint(addr_tree, hf_v5dl_cr, tvb, 0, 1, addr);
proto_tree_add_uint(addr_tree, hf_v5dl_ea1, tvb, 0, 1, addr);
proto_tree_add_uint(addr_tree, hf_v5dl_eal, tvb, 1, 1, addr);
proto_tree_add_uint(addr_tree, hf_v5dl_ea2, tvb, 1, 1, addr);
}
else {
v5dl_ti = NULL;
v5dl_tree = NULL;
}
control = dissect_xdlc_control(tvb, 2, pinfo, v5dl_tree, hf_v5dl_control,
ett_v5dl_control, &v5dl_cf_items, &v5dl_cf_items_ext, NULL, NULL,
is_response, TRUE, FALSE);
v5dl_header_len += XDLC_CONTROL_LEN(control, TRUE);
if (tree)
proto_item_set_len(v5dl_ti, v5dl_header_len);
/*
* XXX - the sample capture supplied with bug 7027 does not
* appear to include checksums in the packets.
*/
#if 0
/*
* Check the checksum, if available.
* The checksum is a CCITT CRC-16 at the end of the packet, so
* if we don't have the entire packet in the capture - i.e., if
* tvb_captured_length(tvb) != tvb_reported_length(tvb) we can't check it.
*/
length = tvb_captured_length(tvb);
reported_length = tvb_reported_length(tvb);
/*
* If the reported length isn't big enough for the V5DL header
* and 2 bytes of checksum, the packet is malformed, as the
* checksum overlaps the header.
*/
if (reported_length < v5dl_header_len + 2)
THROW(ReportedBoundsError);
if (length == reported_length) {
/*
* There's no snapshot length cutting off any of the
* packet.
*/
checksum_offset = reported_length - 2;
checksum = tvb_get_ntohs(tvb, checksum_offset);
checksum_calculated = crc16_ccitt_tvb(tvb, checksum_offset);
checksum_calculated = g_htons(checksum_calculated); /* Note: g_htons() macro may eval arg multiple times */
if (checksum == checksum_calculated) {
checksum_ti = proto_tree_add_uint_format_value(v5dl_tree, hf_v5dl_checksum, tvb, checksum_offset,
2, 0,
"0x%04x [correct]",
checksum);
checksum_tree = proto_item_add_subtree(checksum_ti, ett_v5dl_checksum);
proto_tree_add_boolean(checksum_tree, hf_v5dl_checksum_good, tvb, checksum_offset, 2, TRUE);
proto_tree_add_boolean(checksum_tree, hf_v5dl_checksum_bad, tvb, checksum_offset, 2, FALSE);
} else {
checksum_ti = proto_tree_add_uint_format_value(v5dl_tree, hf_v5dl_checksum, tvb, checksum_offset,
2, 0,
"0x%04x [incorrect, should be 0x%04x]",
checksum, checksum_calculated);
checksum_tree = proto_item_add_subtree(checksum_ti, ett_v5dl_checksum);
proto_tree_add_boolean(checksum_tree, hf_v5dl_checksum_good, tvb, checksum_offset, 2, FALSE);
proto_tree_add_boolean(checksum_tree, hf_v5dl_checksum_bad, tvb, checksum_offset, 2, TRUE);
}
/*
* Remove the V5DL header *and* the checksum.
*/
next_tvb = tvb_new_subset(tvb, v5dl_header_len,
tvb_captured_length_remaining(tvb, v5dl_header_len) - 2,
tvb_reported_length_remaining(tvb, v5dl_header_len) - 2);
} else {
/*
* Some or all of the packet is cut off by a snapshot
* length.
*/
if (length == reported_length - 1) {
/*
* One byte is cut off, so there's only one
* byte of checksum in the captured data.
* Remove that byte from the captured length
* and both bytes from the reported length.
*/
next_tvb = tvb_new_subset(tvb, v5dl_header_len,
tvb_captured_length_remaining(tvb, v5dl_header_len) - 1,
tvb_reported_length_remaining(tvb, v5dl_header_len) - 2);
} else {
/*
* Two or more bytes are cut off, so there are
* no bytes of checksum in the captured data.
* Just remove the checksum from the reported
* length.
*/
next_tvb = tvb_new_subset(tvb, v5dl_header_len,
tvb_captured_length_remaining(tvb, v5dl_header_len),
tvb_reported_length_remaining(tvb, v5dl_header_len) - 2);
}
}
#else
next_tvb = tvb_new_subset_remaining(tvb, v5dl_header_len);
#endif
if (XDLC_IS_INFORMATION(control)) {
/* call V5.2 dissector */
call_dissector(v52_handle, next_tvb, pinfo, tree);
}
}
