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localhost -> localhost - Checksum: 0xfe40 [incorrect, should be 0xc55f]

To: sslug-teknik@xxxxxxxx
From: "Martin Schiøtz" <malinux@xxxxxxxxx>
Date: Thu, 13 Jul 2006 14:58:17 +0200
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Hejsa

Jeg har observeret til at på mine Fedora Core 5 maskiner får jeg en
tcp checksum incorrect, når jeg f.eks laver en 'ssh localhost'. Det
sker også for andre protokoller localhost til localhost.
Kommunikationen fungerer fint og fejler ikke eller foretager
retransmission på pakkerne. Der er ikke ingen checksum problemer, når
kommunikationen går ud af et fysisk interface.

Er det normalt????

- Martin

Udsnit fra ethereal af 2 pakker i en 'ssh localhost' kommunikation:

No.     Time        Source                Destination           Protocol Info
     9 0.020382    127.0.0.1             127.0.0.1             TCP
 ssh > 42162 [ACK] Seq=21 Ack=733 Win=32768 Len=0 TSV=454082948
TSER=454082948
Frame 9 (66 bytes on wire, 66 bytes captured)
Ethernet II, Src: 00:00:00_00:00:00 (00:00:00:00:00:00), Dst:
00:00:00_00:00:00 (00:00:00:00:00:00)
Internet Protocol, Src: 127.0.0.1 (127.0.0.1), Dst: 127.0.0.1 (127.0.0.1)
Transmission Control Protocol, Src Port: ssh (22), Dst Port: 42162
(42162), Seq: 21, Ack: 733, Len: 0
   Source port: ssh (22)
   Destination port: 42162 (42162)
   Sequence number: 21    (relative sequence number)
   Acknowledgement number: 733    (relative ack number)
   Header length: 32 bytes
   Flags: 0x0010 (ACK)
   Window size: 32768 (scaled)
   Checksum: 0xf677 [correct]
   Options: (12 bytes)
   SEQ/ACK analysis

No.     Time        Source                Destination           Protocol Info
    10 0.022785    127.0.0.1             127.0.0.1             SSHv2
 Server: Key Exchange Init
Frame 10 (770 bytes on wire, 770 bytes captured)
Ethernet II, Src: 00:00:00_00:00:00 (00:00:00:00:00:00), Dst:
00:00:00_00:00:00 (00:00:00:00:00:00)
Internet Protocol, Src: 127.0.0.1 (127.0.0.1), Dst: 127.0.0.1 (127.0.0.1)
Transmission Control Protocol, Src Port: ssh (22), Dst Port: 42162
(42162), Seq: 21, Ack: 733, Len: 704
   Source port: ssh (22)
   Destination port: 42162 (42162)
   Sequence number: 21    (relative sequence number)
   Next sequence number: 725    (relative sequence number)
   Acknowledgement number: 733    (relative ack number)
   Header length: 32 bytes
   Flags: 0x0018 (PSH, ACK)
   Window size: 32768 (scaled)
   Checksum: 0x00e9 [incorrect, should be 0x98fb]
   Options: (12 bytes)
SSH Protocol