I currently have the effect that sometimes UDP port numbers seem to get
replaced somewhere between the coLinux guest and the Windows host.
Let me explain what I'm doing:
I have set up an NFS server in a coLinux guest which communicates via
colinux-slirp. I connect to this server from a remote Linux box. After
coLinux booted up I can mount an NFS share exported by the coLinux guest
on the remote Linux box, copy files back and forth and umount the share
again. No problem so far.
But: If I try to mount the same NFS share once again from the same remote
Linux box, the mount attempt fails (running into a time-out). I have then
monitored the network traffic using tcpdump/windump within the coLinux
guest as well as on the Windows host and the remote Linux box and found
- The communication between the Windows host and the remote Linux box seems
to be OK, i.e. the Ethereal recordings show no differences.
- In the communication between the coLinux guest and the Windows host, the
number of the UDP port used for the mount reply seems to get replaced!
This only happens during the second, unsuccessful mount attempt.
The remote Linux box sends an NFS mount request using source port 848 to
the mount daemon of the coLinux guest which is fixed at port number 32767.
This can be monitored in both the logs of the Windows host and the coLinux
guest. The mount reply however goes to port number 848 (OK) according to
the log of the coLinux guest, but to port number 847 (Wrong!) according to
the log of the Windows host. This of course results in an ICMP message
from the remote Linux box indicating that the destination port is
The wrong port number always seems to be a number which has been used
recently before in the communication.
This is with devel-colinux-20051013, kernel 2.6.12-co-0.7.1. I'll attach
the commented ASCII dumps of the network traffic recorded in the coLinux
guest and on the Windows host to this mail. Perhaps there's a network
specialist around who can tell me what's going on here?
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