Ethereal-dev: [ethereal-dev] Bug in packet-tcp: ack value not in tree when RST

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From: Biot Olivier <Olivier.Biot@xxxxxxxxxxxxxxx>
Date: Tue, 25 Sep 2001 15:17:56 +0200
Hi all,

I just looked in-depth at some TCP traces, and I've seen the following
behavior (Ethereal 0.8.19): at the end of a TCP stream, the RST bit is set
in the last packet.  For such a packet, the packet summary displays
correctly Seq and Ack, but the tree lacks Ack while it's present in the
packet (the following 4 bytes).  Example:

--- Packet
0000  00 00 00 00 00 01 08 00 20 a6 e0 90 08 00 45 00   ........ .....E.

0010  00 28 9c 73 40 00 7d 06 a1 f2 8b 0a 86 9a ac 10   .(.s@.}.........

0020  01 b5 0e 33 09 29 11 f2 9f 44 7a 94 62 20 50 04   ...3.)...Dz.b P.

0030  00 00 4b 2f 00 00 55 55 55 55 55 55               ..K/..UUUUUU

---- End Packet

--- From UI:
Transmission Control Protocol, Src Port: 3635 (3635), Dst Port: 2345 (2345),
Seq: 301113156, Ack: 2056544800
    Source port: 3635 (3635)
    Destination port: 2345 (2345)
    Sequence number: 301113156
    Header length: 20 bytes
    Flags: 0x0004 (RST)
        0... .... = Congestion Window Reduced (CWR): Not set
        .0.. .... = ECN-Echo: Not set
        ..0. .... = Urgent: Not set
        ...0 .... = Acknowledgment: Not set
        .... 0... = Push: Not set
        .... .1.. = Reset: Set
        .... ..0. = Syn: Not set
        .... ...0 = Fin: Not set
    Window size: 0
    Checksum: 0x4b2f (correct)
--- End From UI

This should be easy to fix.

Regards,

Olivier