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From Matt P via bug 3774: 

Patch utilizes techniques incorporated in the packet-ieee8023.c dissect_802_3()
routine to dynamically calculate the remaining payload length.  This is then
compared to the length included in the CCSDS header.

svn path=/trunk/; revision=29329
This commit is contained in:
Gerald Combs 2009-08-07 21:53:40 +00:00
parent 2a6163ec32
commit 7110e957f6
1 changed files with 30 additions and 14 deletions
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44
epan/dissectors/packet-eth.c
View File

@ -179,7 +179,7 @@ capture_eth(const guchar *pd, int offset, int len, packet_counts *ld)
}
}
static gboolean check_is_802_2(tvbuff_t *tvb);
static gboolean check_is_802_2(tvbuff_t *tvb, int fcs_len);
static void
dissect_eth_common(tvbuff_t *tvb, packet_info *pinfo, proto_tree *parent_tree,
@ -262,7 +262,7 @@ dissect_eth_common(tvbuff_t *tvb, packet_info *pinfo, proto_tree *parent_tree,
*/
if (ehdr->type <= IEEE_802_3_MAX_LEN && ehdr->type != ETHERTYPE_UNK) {
is_802_2 = check_is_802_2(tvb);
is_802_2 = check_is_802_2(tvb, fcs_len);
col_add_fstr(pinfo->cinfo, COL_INFO, "IEEE 802.3 Ethernet %s",
(is_802_2 ? "" : "Raw "));
@ -344,9 +344,11 @@ dissect_eth_common(tvbuff_t *tvb, packet_info *pinfo, proto_tree *parent_tree,
}
/* -------------- */
static gboolean check_is_802_2(tvbuff_t *tvb)
static gboolean check_is_802_2(tvbuff_t *tvb, int fcs_len)
{
volatile gboolean is_802_2;
volatile int length;
gint captured_length, reported_length;
is_802_2 = TRUE;
@ -371,25 +373,39 @@ static gboolean check_is_802_2(tvbuff_t *tvb)
/* See if the reported payload size matches the
size contained in the CCSDS header. */
if (ccsds_heuristic_length) {
/* Get payload length */
gint size = tvb_reported_length(tvb) - 14;
/* Check if payload is large enough to contain CCSDS header with
packet length info. */
if (size >= 6) {
/* Get CCSDS packet length contained in CCSDS header. */
gint size2 = 7 + tvb_get_ntohs(tvb, 14 + 4);
if (size != size2)
/* The following technique to account for FCS
is copied from packet-ieee8023.c dissect_802_3() */
length = tvb_get_ntohs(tvb, 12);
reported_length = tvb_reported_length_remaining(tvb, ETH_HEADER_SIZE);
if (fcs_len > 0) {
if (reported_length >= fcs_len)
reported_length -= fcs_len;
}
/* Make sure the length in the 802.3 header doesn't go past the end of
the payload. */
if (length > reported_length) {
length = reported_length;
}
/* Only allow inspection of 'length' number of bytes. */
captured_length = tvb_length_remaining(tvb, ETH_HEADER_SIZE);
if (captured_length > length)
captured_length = length;
/* Check if payload is large enough to contain a CCSDS header */
if (captured_length >= 6) {
/* Compare length to packet length contained in CCSDS header. */
if (length != 7 + tvb_get_ntohs(tvb, ETH_HEADER_SIZE + 4))
CCSDS_len = FALSE;
}
}
/* Check if CCSDS Version number (first 3 bits of payload) is zero */
if ((ccsds_heuristic_version) && (tvb_get_bits8(tvb, 8*14, 3)!=0))
if ((ccsds_heuristic_version) && (tvb_get_bits8(tvb, 8*ETH_HEADER_SIZE, 3)!=0))
CCSDS_ver = FALSE;
/* Check if Secondary Header Flag (4th bit of payload) is set to one. */
if ((ccsds_heuristic_header) && (tvb_get_bits8(tvb, 8*14 + 4, 1)!=1))
if ((ccsds_heuristic_header) && (tvb_get_bits8(tvb, 8*ETH_HEADER_SIZE + 4, 1)!=1))
CCSDS_head = FALSE;
/* Check if spare bit (1st bit of 7th word of payload) is zero. */
if ((ccsds_heuristic_bit) && (tvb_get_bits8(tvb, 8*14 + 16*6, 1)!=0))
if ((ccsds_heuristic_bit) && (tvb_get_bits8(tvb, 8*ETH_HEADER_SIZE + 16*6, 1)!=0))
CCSDS_bit = FALSE;
/* If all the conditions are true, don't interpret payload as an 802.2 (LLC).
* Additional check in packet-802.3.c will distinguish between