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Display of reserved octet in 6lowpan IPHC header 

The 6lowpan standard specifies a reserved octet in the extended header
of an IP_PROTO_FRAGMENT packet in the same place used for the header
length for other extension headers.

The current version of the 6lowpan dissector displays the reserved octet
and the rest of the header (6 more bytes) together as data, as opposed to
displaying the reserved octet by itself and then the data (using the
data dissector).

This patch does not change the functionality of the dissector in any
way, only how the 7 bytes are displayed. Instead of displaying the
header information and then 7 bytes of data, it displays the reserved
octet and then the data. This is also consistent with the way the ipv6
dissector displays it (showing the reserved octet and its value).

For this purpose, there is a new hf (hf_6lowpan_nhc_ext_reserved) and
the corresponding proto_tree calls. Also, depending on the type of
extension header, the octets sent to the general data dissector are
shifted by one.

Change-Id: I4c7fb58a3364307e79517b979808f3e34a2e0b94
Reviewed-on: https://code.wireshark.org/review/10908
Petri-Dish: Michael Mann <mmann78@netscape.net>
Tested-by: Petri Dish Buildbot <buildbot-no-reply@wireshark.org>
Reviewed-by: Michael Mann <mmann78@netscape.net>
This commit is contained in:
Pedro Jose Marron 2015-10-09 17:13:49 +02:00 committed by Michael Mann
parent b07226775e
commit 4a45bd5bf4
1 changed files with 14 additions and 2 deletions
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16
epan/dissectors/packet-6lowpan.c
View File

@ -236,6 +236,7 @@ static int hf_6lowpan_nhc_ext_eid = -1;
static int hf_6lowpan_nhc_ext_nh = -1;
static int hf_6lowpan_nhc_ext_next = -1;
static int hf_6lowpan_nhc_ext_length = -1;
static int hf_6lowpan_nhc_ext_reserved = -1;
/* NHC UDP compression header fields. */
static int hf_6lowpan_nhc_udp_checksum = -1;
@ -1914,6 +1915,9 @@ dissect_6lowpan_iphc_nhc(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, gi
ext_hlen = 1;
length = (guint8)sizeof(struct ip6_frag);
ext_len = length - ext_hlen;
proto_tree_add_uint(nhc_tree, hf_6lowpan_nhc_ext_reserved, tvb, offset, 1, tvb_get_guint8(tvb, offset));
} else {
/* Get and display the extension header length. */
ext_hlen = (guint8)sizeof(struct ip6_ext);
@ -1957,8 +1961,13 @@ dissect_6lowpan_iphc_nhc(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, gi
return nhdr;
}
/* Display the extension header using the data dissector. */
call_dissector(data_handle, tvb_new_subset_length(tvb, offset, ext_len), pinfo, nhc_tree);
if (ext_proto == IP_PROTO_FRAGMENT) {
/* Display the extension header using the data dissector. */
call_dissector(data_handle, tvb_new_subset_length(tvb, offset+1, ext_len-1), pinfo, nhc_tree);
} else {
/* Display the extension header using the data dissector. */
call_dissector(data_handle, tvb_new_subset_length(tvb, offset, ext_len), pinfo, nhc_tree);
}
/* Copy the extension header into the struct. */
tvb_memcpy(tvb, LOWPAN_NHDR_DATA(nhdr) + ext_hlen, offset, ext_len);
@ -2667,6 +2676,9 @@ proto_register_6lowpan(void)
{ &hf_6lowpan_nhc_ext_length,
{ "Header length", "6lowpan.nhc.ext.length",
FT_UINT8, BASE_DEC, NULL, 0x0, NULL, HFILL }},
{ &hf_6lowpan_nhc_ext_reserved,
{ "Reserved octet", "6lowpan.nhc.ext.reserved",
FT_UINT8, BASE_HEX, NULL, 0x0, NULL, HFILL }},
/* NHC UDP header fields. */
{ &hf_6lowpan_nhc_udp_checksum,