All of a sudden (read: without changing any parameters) my netbsd virtualmachine started acting oddly. The symptoms concern ssh tunneling.

From my laptop I launch:

$ ssh -L 7000:localhost:7000 [email protected] -N -v

Then, in another shell:

$ irssi -c localhost -p 7000

The ssh debug says:

debug1: Connection to port 7000 forwarding to localhost port 7000 requested.
debug1: channel 2: new [direct-tcpip]
channel 2: open failed: connect failed: Connection refused
debug1: channel 2: free: direct-tcpip: listening port 7000 for localhost port 7000, connect from port 53954, nchannels 3

I tried also with localhost:80 to connect to the (remote) web server, with identical results.

The remote host runs NetBSD:

bash-4.2# uname -a
NetBSD host 5.1_STABLE NetBSD 5.1_STABLE (XEN3PAE_DOMU) #6: Fri Nov  4 16:56:31 MET 2011  [email protected]:/m/obj/m/src/sys/arch/i386/compile/XEN3PAE_DOMU i386

I am a bit lost. I tried running tcpdump on the remote host, and I spotted these ‘bad chksum’:

09:25:55.823849 IP (tos 0x0, ttl 64, id 0, offset 0, flags [DF], proto TCP (6), length 67, bad cksum 0 (->3cb3)!) > P, cksum 0xfe37 (incorrect (-> 0xa801), 1622402406:1622402421(15) ack 1635127887 win 4096 <nop,nop,timestamp 5002727 5002603>

I tried restarting the ssh daemon to no avail. I haven’t rebooted yet – perhaps somebody here can suggest other diagnostics. I think it might either be the virtual network card driver, or somebody rooted our ssh.


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