args: -redir tcp:HOSTPORT::GUESTPORT
‘hostfwd=[tcp|udp]:[hostaddr]:hostport-[guestaddr]:guestport’Redirect incoming TCP or UDP connections to the host port hostport to the guest IP address guestaddr on guest port guestport. If guestaddr is not specified, its value is x.x.x.15 (default first address given by the built-in DHCP server). By specifying hostaddr, the rule can be bound to a specific host interface. If no connection type is set, TCP is used. This option can be given multiple times.
For example, to redirect host X11 connection from screen 1 to guest screen 0, use the following:
| | # on the host
qemu -net user,hostfwd=tcp:127.0.0.1:6001-:6000 [...]
# this host xterm should open in the guest X11 server
xterm -display :1
|
To redirect telnet connections from host port 5555 to telnet port on the guest, use the following:
| | # on the host
qemu -net user,hostfwd=tcp:5555::23 [...]
telnet localhost 5555
|
Then when you use on the host telnet localhost 5555, you connect to the guest telnet server.
‘guestfwd=[tcp]:server
ort-dev’Forward guest TCP connections to the IP address server on port port to the character device dev. This option can be given multiple times.
Note: Legacy stand-alone options -tftp, -bootp, -smb and -redir are still processed and applied to -net user. Mixing them with the new configuration syntax gives undefined results. Their use for new applications is discouraged as they will be removed from future versions.
[h=3]Forwarding ports to KVM clients[/h]
If you create a VM under Ubuntu 11.10 using virt-manager the default is for it to use Usermode Networking. This doesn't require any setup, however the VM gets an IP address on a new subnet (10.0.2.1/24) that isn't available from the outside world - or even from the host!
You can move to bridged networking but this requires a fair amount of system configuration work. Another, less well documented, way is to use the redirect functionality built into QEMU.
The QEMU man page specifies -redir as follows:
-redir [tcp|udp]:host-port:[guest-host]:guest-port When using the user mode network stack, redirect incoming TCP or UDP connections to the host port host-port to the guest guest-host on guest port guest-port. If guest-host is not specified, its value is 10.0.2.15 (default address given by the built-in DHCP server). For example, to redirect host X11 connection from screen 1 to guest screen 0, use the following: # on the host qemu -redir tcp:6001::6000 [...] # this host xterm should open in the guest X11 server xterm -display :1 To redirect telnet connections from host port 5555 to telnet port on the guest, use the following: # on the host qemu -redir tcp:5555::23 [...] telnet localhost 5555 Then when you use on the host CWtelnet localhost 5555, you connect to the guest telnet server. To use this with a virt-manager created virtual machine you need to manually edit the VM Config (I'm using QEMU usermode to manage my VMs so I have to specify a special connection string):
virsh --connect qemu:///session edit Windows You then have to specify that this domain will use extra commands from a special namespace, so change the top attribute from:
<domain type='kvm'> to:
<domain type='kvm' xmlns:qemu='http://libvirt.org/schemas/domain/qemu/1.0'> Then add a some override parameters to be passed straight through to the QEMU command line. Here I'm forwarding port 1234 on the host to port 3389 on the VM (make this block immediately under the node):
<qemu:commandline> <qemu:arg value='-redir'/> <qemu:arg value='tcp:1234::3389'/> </qemu:commandline> Save these changes, exit the editor and then start up the VM. You should be able to connect to localhost:1234 and be plumbed through to port 3389 on the VM.
