Re: ssh through vista connection sharing not working, NEW INFO: 802.1q headers from vista



On Nov 14, 12:41 pm, Cacadril <en...@xxxxxxxxx> wrote:
I am trying to access a remote computer using ssh, but get no
response. Using strace, I see the client opening a socket to the
server, setting keep-alive, and hanging in the very first read system
call.

The general connectivity is in place, I browsedhttp://www.nytimes.com
without problems.

The ssh client is a linux (debian lenny) laptop. I am snooping the
connection with wireshark, and I see the response from the ssh server,
saying "SSH-2.0-OpenSSH_5.1\r\n". Then I see eight retransissions of
this datagram, and finally a FIN followed by a FIN-ACK response.

I found something: All response datagrams, i.e., all datagrams issued
by the remote server, arrive at my linux box with an 802.1q "header"
inserted between the ethernet header and the ip header. I guess this
is something Vista introduces, see the quoted topology description
below. I will start a new thread to ask about this.

There
is never an ACK response from my laptop, other than the final FIN-ACK.

Not exactly correct, as there is an ack after a very long time delay.
This is also apparent in the quoted list of exchanges below.

Also the connection establishment itself looks strange, with multiple
retransmissions:

  source:    message:
  client       SYN
  server      SYN,ACK     70 ms response time
  client       SYN             3 seconds after the first SYN
  server      SYN,ACK     70 ms
  server      SYN,ACK     retransmission 15 ms after previous

repeat the last three datagrams with increasing delays, 6 seconds, 12
seconds between tries. Then 24 seconds after last try,

  client     SYN
  server    SYN,ACK
  client     SYN,ACK     0,1 ms delay   -- NB this is an ACK reponse
from my client
  server    "SSH-2.0-OpenSSH_5.1\r\n"    (21 bytes)  70 ms
  server    retransmission of last message X 8
  server    FIN,ACK  Seq=22, ack=21
  client     FIN,ACK  Seq=1, ack=1    1270 seconds after server FIN

I checked the iptables state using iptables -v -L; got policy ACCEPT
and no rules on all chains.  Same for tables nat, mangle, and raw.

Yet I could browse the internet.

The network topology is as follows.

I connect to the internet from a Vista laptop, using a wireless. The
linux laptop is connected to the Vista laptop using an ethernet cable.
Connection sharing is turned on in the Vista. I run putty (windows
telent/ssh client) on Vista and connect successfully to the ssh server
in question. I run wireshark on both laptops, snooping the ethernet
interface and see exactly the same datagrams.

What am I missing?

Thanks
.



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