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does anyone have problems in dissecting LDP P2MP FEC elements?

asked 2017-11-28 13:42:55 +0000

sharkdam gravatar image

updated 2017-11-28 14:05:32 +0000

grahamb gravatar image

Hi All, I would like to see multipoint LDP FEC elements like

ldp.msg.tlv.ldp_p2mp.addr_len   Address Length  Unsigned integer, 1 byte    1.12.0 to 2.4.2
ldp.msg.tlv.ldp_p2mp.ipv4_rtnodeaddr    Root Node Address   IPv4 address    1.12.0 to 2.4.2
ldp.msg.tlv.ldp_p2mp.oplength   Opaque Length   Unsigned integer, 2 bytes   1.12.0 to 2.4.2
ldp.msg.tlv.ldp_p2mp.opvalue    Opaque Value    Sequence of bytes   1.12.0 to 2.4.2
ldp.msg.tlv.ldp_p2mp.type   P2MP Type   Unsigned integer, 1 byte    1.12.0 to 2.4.2

I see that they are supported but when I open a capture with these packets wireshark cannot decode them

Frame 6130: 108 bytes on wire (864 bits), 108 bytes captured (864 bits) on interface 0
Ethernet II, Src: ca:01:1d:fd:00:08 (ca:01:1d:fd:00:08), Dst: ca:02:1e:0c:00:08 (ca:02:1e:0c:00:08)
Internet Protocol Version 4, Src:, Dst:
Transmission Control Protocol, Src Port: 646, Dst Port: 14535, Seq: 1981, Ack: 1981, Len: 54
Label Distribution Protocol
    Version: 1
    PDU Length: 50
    LSR ID:
    Label Space ID: 0
    Label Mapping Message
        0... .... = U bit: Unknown bit not set
        Message Type: Label Mapping Message (0x400)
        Message Length: 40
        Message ID: 0x00000132
        Forwarding Equivalence Classes TLV
            00.. .... = TLV Unknown bits: Known TLV, do not Forward (0x0)
            TLV Type: Forwarding Equivalence Classes TLV (0x100)
            TLV Length: 24
            **FEC Elements**
                **FEC Element 1**
                    **Unknown FEC TLV type**
                        **[Expert Info (Warning/Protocol): Unknown FEC TLV type]
                            [Unknown FEC TLV type]**
                            **[Severity level: Warning]**
                            **[Group: Protocol]**

I used 2.4.2 on Windows and 2.2.6 on linux, same results, any ideas?


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answered 2017-11-28 19:19:20 +0000

Jaap gravatar image

If you are convinced these are valid packets then enter a bug report and make sure to attach this capture file. The fact that it says Unknown FEC TLV type tells me that there is a different interpretation of the tag between WIreharks' LDP dissector and the protocol.

Without the capture file there's little else to do.

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Hello Jaap and All,

I was trying to attach the pcap file, but blog says I need >60 point to attach a file, unfortunately I'm new to this community, there is way to overcome this limitation and attach the files? I would like someone can try top open it to check if results are the same I see.


sharkdam gravatar imagesharkdam ( 2017-11-29 08:24:43 +0000 )edit

Hello again,

I checked on bugzilla and saw that there is already a bug opened for version 2.2.2 about the dissection of P2MP = 0x06 MP2MP (Upstream) = 0x07 MP2MP (Downstream) = 0x08, bug is 13171. Do you think it's better to file a new bug for the specific version I'm using?

Version 2.4.2 (v2.4.2-0-gb6c63ae086)

Compiled (64-bit) with Qt 5.6.3, with WinPcap (4_1_3), with GLib 2.42.0, with
zlib 1.2.8, with SMI 0.4.8, with c-ares 1.12.0, with Lua 5.2.4, with GnuTLS
3.4.11, with Gcrypt 1.7.6, with MIT Kerberos, with GeoIP, with nghttp2 1.14.0,
with LZ4, with Snappy, with libxml2 2.9.4, with QtMultimedia, with AirPcap, with
SBC, with SpanDSP.

Running on 64-bit Windows 10, build 14393, with Intel(R) Core(TM) i5-6200U CPU @
2.30GHz (with SSE4 ...
sharkdam gravatar imagesharkdam ( 2017-11-29 08:44:55 +0000 )edit

Add the capture file to the bug in Bugzilla. If it's not relevant to that specific bug, someone will move it to an appropriate entry.

grahamb gravatar imagegrahamb ( 2017-11-29 10:07:58 +0000 )edit

Hello, file attached to the bug. Thanks.

sharkdam gravatar imagesharkdam ( 2017-11-29 10:26:10 +0000 )edit

I see that bug 13171 is now fixed, I tried to build new wireshark patching packet-ldp.c with the diff file attached to the bug, but results are the same for me, I cannot see MP2MP FEC elements, could someone try the fix? Thanks.

sharkdam gravatar imagesharkdam ( 2017-12-04 12:52:49 +0000 )edit

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Asked: 2017-11-28 13:42:55 +0000

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Last updated: Nov 29