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Add ethernet protocol preference to manually set the trailer length. 

(some TAPs can slice packets and then add a custom trailer)


svn path=/trunk/; revision=49675
This commit is contained in:
Sake Blok 2013-06-01 09:05:56 +00:00
parent 9c4488cedf
commit b2a6a6c15c
1 changed files with 41 additions and 8 deletions
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49
epan/dissectors/packet-eth.c
View File

@ -45,6 +45,7 @@ void proto_reg_handoff_eth(void);
/* Assume all packets have an FCS */
static gboolean eth_assume_padding = TRUE;
static guint eth_trailer_length = 0;
static gboolean eth_assume_fcs = FALSE;
static gboolean eth_check_fcs = TRUE;
/* Interpret packets as FW1 monitor file packets if they look as if they are */
@ -207,7 +208,7 @@ capture_eth(const guchar *pd, int offset, int len, packet_counts *ld)
static gboolean check_is_802_2(tvbuff_t *tvb, int fcs_len);
static void
static proto_tree *
dissect_eth_common(tvbuff_t *tvb, packet_info *pinfo, proto_tree *parent_tree,
int fcs_len)
{
@ -252,7 +253,7 @@ dissect_eth_common(tvbuff_t *tvb, packet_info *pinfo, proto_tree *parent_tree,
* Ethernet packet.
*/
if (dissector_try_heuristic(heur_subdissector_list, tvb, pinfo, parent_tree, NULL))
return;
return fh_tree;
if (ehdr->type <= IEEE_802_3_MAX_LEN) {
/* Oh, yuck. Cisco ISL frames require special interpretation of the
@ -266,7 +267,7 @@ dissect_eth_common(tvbuff_t *tvb, packet_info *pinfo, proto_tree *parent_tree,
tvb_get_guint8(tvb, 3) == 0x00 &&
tvb_get_guint8(tvb, 4) == 0x00) {
dissect_isl(tvb, pinfo, parent_tree, fcs_len);
return;
return fh_tree;
}
}
@ -319,7 +320,7 @@ dissect_eth_common(tvbuff_t *tvb, packet_info *pinfo, proto_tree *parent_tree,
"Invalid length/type: 0x%04x (%d)", ehdr->type, ehdr->type);
next_tvb = tvb_new_subset_remaining(tvb, 14);
call_dissector(data_handle, next_tvb, pinfo, parent_tree);
return;
return fh_tree;
}
if (ehdr->type <= IEEE_802_3_MAX_LEN && ehdr->type != ETHERTYPE_UNK) {
@ -367,7 +368,7 @@ dissect_eth_common(tvbuff_t *tvb, packet_info *pinfo, proto_tree *parent_tree,
if ((dst_addr[0] == 'i') || (dst_addr[0] == 'I') ||
(dst_addr[0] == 'o') || (dst_addr[0] == 'O')) {
call_dissector(fw1_handle, tvb, pinfo, parent_tree);
return;
return fh_tree;
}
}
@ -407,6 +408,7 @@ dissect_eth_common(tvbuff_t *tvb, packet_info *pinfo, proto_tree *parent_tree,
ethertype(ehdr->type, tvb, ETH_HEADER_SIZE, pinfo, parent_tree, fh_tree, hf_eth_type,
hf_eth_trailer, fcs_len);
}
return fh_tree;
}
/* -------------- */
@ -663,9 +665,33 @@ add_ethernet_trailer(packet_info *pinfo, proto_tree *tree, proto_tree *fh_tree,
static void
dissect_eth_maybefcs(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree)
{
dissect_eth_common(tvb, pinfo, tree,
eth_assume_fcs ? 4 :
pinfo->pseudo_header->eth.fcs_len);
proto_tree *fh_tree;
/* Some devices slice the packet and add their own trailer before
putting the frame on the network. Make sure these packets get
a proper trailer (even though the sliced frame might not
properly dissect. */
if ( (eth_trailer_length > 0) && (eth_trailer_length < tvb_length(tvb)) ) {
tvbuff_t *next_tvb;
guint total_trailer_length;
total_trailer_length = eth_trailer_length + (eth_assume_fcs ? 4 : 0);
/* Dissect the tvb up to, but not including the trailer */
next_tvb = tvb_new_subset(tvb, 0,
tvb_length(tvb) - total_trailer_length,
tvb_reported_length(tvb) - total_trailer_length);
fh_tree = dissect_eth_common(next_tvb, pinfo, tree, 0);
/* Now handle the ethernet trailer and optional FCS */
if ( fh_tree != NULL ) {
next_tvb = tvb_new_subset_remaining(tvb, tvb_length(tvb) - total_trailer_length);
add_ethernet_trailer(pinfo, tree, fh_tree, hf_eth_trailer, tvb, next_tvb,
eth_assume_fcs ? 4 : pinfo->pseudo_header->eth.fcs_len);
}
} else {
dissect_eth_common(tvb, pinfo, tree, eth_assume_fcs ? 4 : pinfo->pseudo_header->eth.fcs_len);
}
}
/* Called by other dissectors This one's for encapsulated Ethernet
@ -781,6 +807,13 @@ proto_register_eth(void)
"before the frame was padded.",
&eth_assume_padding);
prefs_register_uint_preference(eth_module, "trailer_length",
"Fixed ethernet trailer length",
"Some TAPs add a fixed length ethernet trailer at the end "
"of the frame, but before the (optional) FCS. Make sure it "
"gets interpreted correctly.",
10, &eth_trailer_length);
prefs_register_bool_preference(eth_module, "assume_fcs",
"Assume packets have FCS",
"Some Ethernet adapters and drivers include the FCS at the end of a packet, others do not. "