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Improve handling of VOIP VLAN queries and replies. 

For queries, there appear to be two different versions, one with a
2-byte value of some unknown type and one with a 1-byte value that
appears to be an "appliance type" code followed by a 2-byte VLAN ID.

For replies, there only appears to be a version with a 1-byte "appliance
type" followed by a 2-byte VLAN ID, but handle a too-short payload.

Also point to http://www.rhyshaden.com/cdp.htm in some comments.

Change-Id: If1b476d5e6b23c7e0ba027835c6f0c84c8b723b7
Reviewed-on: https://code.wireshark.org/review/25249
Reviewed-by: Guy Harris <guy@alum.mit.edu>
This commit is contained in:
Guy Harris 2018-01-10 12:16:30 -08:00
parent 182112c10d
commit 37e364b241
1 changed files with 52 additions and 35 deletions
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87
epan/dissectors/packet-cdp.c
View File

@ -38,9 +38,13 @@
*
* and
*
* http://www.cisco.com/c/en/us/support/docs/switches/catalyst-4500-series-switches/13414-103.html#cdp
* http://www.cisco.com/c/en/us/support/docs/switches/catalyst-4500-series-switches/13414-103.html#cdp
*
* for some more information on CDP version 2 (a superset of version 1).
*
* Also see
*
* http://www.rhyshaden.com/cdp.htm
*/
void proto_register_cdp(void);
@ -577,52 +581,58 @@ dissect_cdp(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, void* data _U_)
break;
case TYPE_VOIP_VLAN_REPLY:
tlvi = NULL;
if (tree) {
if (length >= 7) {
tlv_tree = proto_tree_add_subtree_format(cdp_tree, tvb, offset, length, ett_cdp_tlv, NULL,
"VoIP VLAN Reply: %u", tvb_get_ntohs(tvb, offset + 5));
} else {
/*
* XXX - what are these? I've seen them in some captures;
* they have a length of 6, and run up to the end of
* the packet, so if we try to dissect it the same way
* we dissect the 7-byte ones, we report a malformed
* frame.
*/
tlv_tree = proto_tree_add_subtree(cdp_tree, tvb,
offset, length, ett_cdp_tlv, NULL, "VoIP VLAN Reply");
}
guint32 vlan_id;
tlv_tree = proto_tree_add_subtree(cdp_tree, tvb,
offset, length, ett_cdp_tlv, &tlvi,
"VoIP VLAN Reply");
proto_tree_add_item(tlv_tree, hf_cdp_tlvtype, tvb, offset + TLV_TYPE, 2, ENC_BIG_ENDIAN);
proto_tree_add_item(tlv_tree, hf_cdp_tlvlength, tvb, offset + TLV_LENGTH, 2, ENC_BIG_ENDIAN);
proto_tree_add_item(tlv_tree, hf_cdp_data, tvb, offset + 4, 1, ENC_NA);
if (length >= 7) {
proto_tree_add_item(tlv_tree, hf_cdp_voice_vlan, tvb, offset + 5, 2, ENC_BIG_ENDIAN);
if (length == 6) {
/*
* XXX - this doesn't appear to happen, so report it
* as an error.
*/
proto_tree_add_item(tlv_tree, hf_cdp_data, tvb, offset + 4, 2, ENC_NA);
} else {
/*
* XXX - the first byte appears to be a 1-byte
* "appliance type" code.
*/
proto_tree_add_item(tlv_tree, hf_cdp_data, tvb, offset + 4, 1, ENC_NA);
proto_tree_add_item_ret_uint(tlv_tree, hf_cdp_voice_vlan, tvb, offset + 5, 2, ENC_BIG_ENDIAN, &vlan_id);
proto_item_append_text(tlvi, ": VLAN %u", vlan_id);
}
}
offset += length;
break;
case TYPE_VOIP_VLAN_QUERY:
tlvi = NULL;
if (tree) {
if (length >= 7) {
tlv_tree = proto_tree_add_subtree_format(cdp_tree, tvb, offset, length,
ett_cdp_tlv, NULL, "VoIP VLAN Query: %u", tvb_get_ntohs(tvb, offset + 5));
} else {
/*
* XXX - what are these? I've seen them in some captures;
* they have a length of 6, and run up to the end of
* the packet, so if we try to dissect it the same way
* we dissect the 7-byte ones, we report a malformed
* frame.
*/
tlv_tree = proto_tree_add_subtree(cdp_tree, tvb,
offset, length, ett_cdp_tlv, NULL, "VoIP VLAN Query");
}
guint32 vlan_id;
tlv_tree = proto_tree_add_subtree(cdp_tree, tvb,
offset, length, ett_cdp_tlv, &tlvi,
"VoIP VLAN Query");
proto_tree_add_item(tlv_tree, hf_cdp_tlvtype, tvb, offset + TLV_TYPE, 2, ENC_BIG_ENDIAN);
proto_tree_add_item(tlv_tree, hf_cdp_tlvlength, tvb, offset + TLV_LENGTH, 2, ENC_BIG_ENDIAN);
proto_tree_add_item(tlv_tree, hf_cdp_data, tvb, offset + 4, 1, ENC_NA);
if (length >= 7) {
proto_tree_add_item(tlv_tree, hf_cdp_voice_vlan, tvb, offset + 5, 2, ENC_BIG_ENDIAN);
if (length == 6) {
/*
* This is some unknown value; it's typically 0x20 0x00,
* which, as a big-endian value, is not a VLAN ID, as
* VLAN IDs are 12 bits long.
*/
proto_tree_add_item(tlv_tree, hf_cdp_data, tvb, offset + 4, 2, ENC_BIG_ENDIAN);
} else {
/*
* XXX - is this a 1-byte "appliance type" code?
*/
proto_tree_add_item(tlv_tree, hf_cdp_data, tvb, offset + 4, 1, ENC_NA);
proto_tree_add_item_ret_uint(tlv_tree, hf_cdp_voice_vlan, tvb, offset + 5, 2, ENC_BIG_ENDIAN, &vlan_id);
proto_item_append_text(tlvi, ": VLAN %u", vlan_id);
}
}
offset += length;
@ -1123,6 +1133,13 @@ dissect_address_tlv(tvbuff_t *tvb, int offset, int length, proto_tree *tree)
}
}
if ((protocol_type == PROTO_TYPE_IEEE_802_2) && (protocol_length == 8) && (etypeid > 0)) {
/*
* See also:
*
* http://www.rhyshaden.com/cdp.htm
*
* where other Ethertypes are mentioned.
*/
switch (etypeid) {
case ETHERTYPE_IPv6: